Progress 10/01/10 to 09/30/15

Outputs
Target Audience:Target audiences reached by our efforts during the reporting period include academic peer audiences reading our journalarticles, outreach articles, and attending national conferences such as ASHS, members and followers of the controlled-environment agriculture communitysuch as NCERA-101, industrial stakeholders of the SCRILED NIFA project, grower groups served during invitedpresentations, and the general public receiving outreach presentations and guided tours of our research facilities and viewers of the project website. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Graduate students and post doctoral research associatesworking in the Mitchell laboratoryhave been able to participate innational and international conferences, as well as SCRI project stakeholderannual meetings to present their findings, network with the sciencecommunity, their peers, and meet future colleagues. One grad studentpresented at an international greenhouse conference in Korea and alsoat a national controlled environmentsconference in Alaska. Two grad students attended an American Society for Horticultural Science annualconference and won awards for poster and oralpresentations. Undergraduate horticultural science and engineering-technology students collaborate on engineering-support projects in the lab. Other undergraduate students assist graduate students withtheir laboratory and greenhouse data collection and date-processing efforts. One undergraduate who conducted anindependent research project graduated with a BS in Horticultural Science and contined on for a Master's degree in the lab. A PhD student completed requirements for the degree and successfully defended thedissertation research. A Master's student did the same. Present and former students and post docs published several peer-reviewed papers during the course of the project. Students working in the lab also served as officers in departmental student organizations as well as on faculty searchcommittees and as student representatives on important departmental committees. Students in the lab continue to use theirlab experience as a springboard for scholarships, fellowships, and for professional placement. Multiple letters ofrecommendation are written annually for former and present students and post docs who are applying for positions and growing in theirprofession. How have the results been disseminated to communities of interest?The Mitchell laboratoryactively disseminatesinformation to the scientific community, professional societies, and the general public throughpeer-reviewed scientific publications,invited and contributed conference presentations, by outreach presentations to visiting tour groups, to multi-media organizations taping video stories for television,and by uploades to the SCRI project website.Scientificarticles have been published over the course of the project, one of which recorded 710 hits 5 months after publication. The PIgave invited presentations atnational and international conferences, graduate students won awards for their research at national conferences as well as at departmental research retreats, contributions were made to the SCRILED website, and findings have beencommunicated annually to commercial stakeholders and advisory board. The PIis regularly quotedin the mass media on topics ranging from LEDs tocontrolled-environment agriculture to space life-support systems, and is in frequent demand by entrpreneurs, lighting companies, and growers regardingsupplemental or sole-source lighting, hydroponics, aquaponics, and CEA startups. The lab says "yes", whenever possible, to requeststo give apublic tour of research in progressto visiting school, church, professional, or privategroups. The Mitchell lab participated activelyin developing areview article entitled "LEDs in Horticulture" published in Horticultural Reviews in 2015. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? Technology was developed to apply photosyntheticlight from light-emitting diodes (LEDs) directly into the leafcanopy of self-shadinghigh-wire tomato cropsgrowingin the greenhouse instead of using electricity-guzzling, heat-producing, high-pressure sodium(HPS) lamps that have to be mounted high above vertically trained hydroponic tomatocrops. Although supplemental lighting (SL) from HPSlamps is sufficient to produce fresh-market greenhouse tomato cropsin northern climates during the off-season, the electrical-energy cost of doing so makes the economics of local greenhouse production less favorable compared to long-distance shipping of tomatoes from southern climates in the winter. We compared yields of tomatoes grown with intracanopy-lighted LEDSL (ICL-LED)compared to traditional overhead HPSSL (OH-HPS) as well as control crops receiving no SL. Yield was compared for all treatments for crops going from winter to summer as well as from summer to winter over several years of testing. Both ICL-LED as well as OH-HPS SL treatments consistently stimulated yield of tomato fruits (number and frit mass) compared to controls, but there were no differences in yield parameters between the two types of SL. However, theelectrical cost of ICL-LED SL ranged from 25 to 50 percent that of OH-HPS, depending on the wattage of HPS used. This finding has been confirmed consistently over several years of testing. Ambient light within the foliar canopy of control or OH-HPS high-wire tomato stands declined with vertical distance from the top to the bottom of the stand, regardless of growing season. Intracanopy lighting eliminated the light gradient and would have prevented or delayed the senescence of lower leaves, but since fruits were harvested weekly from the bottom up and associated leaves removed at the same time, leaf senescence was not seen, even for OH-HPS and control treatments. A red:blue ratio of 93 to 95 percent red, 5 to 7 percent blue and a total daily light integral (DLI) of 25 mol per m2 per day gave adequate light for crop development. Neitherphysico-chemical (color, sugar, acid, conductivity, pH) norsensory testing (color, acidity, sweetness, aroma, texture, aftertaste, overall approval) indicated significantdifferences among SL treatments, and all parameters were positive for quality attributes. Thus, more energy-efficient ICL-LED SL can be used by growers without concern about negative effects of LEDs or ICL. When far-red (FR) LEDs were tested along with red (R) and blue (B) LEDs, 15 per cent of total flux as FR allowed plantsto tolerate elevated fluxes of B up to 25 per cent increased both leaf photosynthetic rateand stomatal conductance compared to unsupplemented controls. FR promotesleaf expansion while high B inhibits it, and B promotes stomatal aperture while FR has no effect. Multi-spectral blends of SL have different effects on multiple photosynthetic parameters of tomato, but effects on harvest parameters (fruit number, mass) or fruit-quality attributes (ascorbic acid, carotenoids, phenolics, flavenols) were not different. The dynamic solar environmentinherent to greenhouse production systems may nullify specific spectral effects of SL on secondary metabolism.When propagating tomato-seedling transplants in the greenhouse for subsequent crop production, SL with different spectra of light promoted number and area of leaves, hypocotyl diameter, epicotyl length, and shoot dry weight to different extents throughout the year, depending on specific spectra. Blue light in SL has potential to stimulate overall seedling growth compared to blue-deficient SL treatments in overcast, variable-DLI climates. Sole-source-lighting studies with hydroponic leaf lettuce growth conducted under adjustable red + blue LEDs found that seedlings in the lag phase of crop development do not respond readily to optimizing environments of elevated light and enriched carbon dioxide. Energy and resources can be saved until plants are ready to enter the shorter exponential phase of the growth curve. However, seedlings were found to elongate excessively, break, and die under low light levels otherwise intended to save energy during lag. However, it was found that providing 5 to 10 percent of total light as blue and gradually increasing total light level during latter stages of lag phase prevented seedlings from elongating excessively, made them stocky, and prepared them well for exponential growth. Fifteen days after seedling emergence, plants were ready to respond positively to carbon dioxide enrichment and light enhancement. Because the overhead LED array was actively heat-sinked on its backside, it was possible to position the LED array less than 10 cm above the top of the crop canopy without getting separation of red and blue colors on the leaves, as well as not scorching the surface of the crop. This close-canopy lighting allowed more than 20 times less electrical power to be used to provide adequate photosynthetic photon flux at crop level compared to traditional overhead HPS. Additional targeting of specific clusters of red and blue LEDs to specific plants on the hydroponics surface without allowing photons to fall on empty spaces between plants until the canopy closed between plants saved another 50 percent of electrical energy for lighting. The combination of close-canopy targeted lighting with red plus blue LEDs improved the efficiency of forming plant dry biomass from more than 1 g per kWh to 1.61 g per kWh. The results suggest that major savings of electrical power and energy can be achieved for growing leafy greens in commercial operations by leveraging the unique properties of LEDs for optimizing spectrum, negating the inverse square law, and control of light distribution.

Publications

• Type: Journal Articles Status: Published Year Published: 2015 Citation: Gomez, C. and C. Mitchell. 2015. Growth responses of tomato seedlings to different spectra of supplemental lighting. HortScience 50 (1): 1-7.
• Type: Journal Articles Status: Published Year Published: 2015 Citation: Massa, G.D. E.S. Chase, J.B. Santini, and C.A. Mitchell. 2015. Temperature affects long-term productivity and quality attributes of day-neutral strawberry for a space life-support system. Life Sciences in Space Research 5:39-46.
• Type: Book Chapters Status: Published Year Published: 2015 Citation: Mitchell, C., J. Burr, M. Dzakovich, C. Gomez, R. Lopez, R. Hernandez, C. Kubota, C. Currey, Q. Meng, E. Runkle, C. Bourget, R. Morrow, and A.J. Both. 2015. LEDs in Horticulture. Horticultural Reviews 43: 1-87.
• Type: Journal Articles Status: Awaiting Publication Year Published: 2015 Citation: Dzakovich, M. C. Gomez, and C.A. Mitchell. 2015. Tomatoes grown with light-emitting diodes (LEDs) or high-pressure sodium (HPS) vs. HPS supplemental lighting are of comparable quality. HortScience 50(10):1-5.

Progress 10/01/13 to 09/30/14

Outputs
Target Audience: Target audiences reached by our efforts during the reporting period include academic peer audiences reading our journal articles and attending national conferences such as ASHS, members of the controlled-environment agriculture community such as NCERA-101, industrial stakeholders in the SCRILED NIFA project, grower groups served during invited presentations, and the general public receiving outreach presentations and guided tours of research facilities. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? Graduate students working on CAMLab projects get to go to national and international conferences, as well as stakeholder mettings to present their findings and network with the scientific community, peers, and future colleagues. One grad student presented at an international greenhouse conference in Korea and was also able to attend a national controlled environments conference in Alaska. Two grad students attended a national horticulture conference and won awards for poster and oral presentations. Undergraduate horticultural science and engineering technology students collaborate on the cuvette project to integrate a complex multidisciplinary hardware/software/lighting/growing/monitoring sytem, and will be co-authors on a prrof-of-concept paper to be published in a peer-reviewed journal. Other undergraduate students assist the graduate students in their laboratory and greenhouse data collection and date-processing efforts. One undergraduate who conducted an independent research project graduated with a BS in Horticultural Science and contined for a Master's degree in the lab during the reporting period. The PhD student completed all requirements for the degree and successfully defended the dissertation research. Present and former students and post docs published several peer-reviewed papers during the reporting period. Students in the lab served as officers in departmental student organizations as well as on faculty search committees and as student representatives on important departmental committees. Students in the lab continue to use their lab experience as a springboard for schoraships, fellowships, and for professional placement. Many letters of recommendation are written annually for former and present students and post docs climbing professionally. How have the results been disseminated to communities of interest? The CAMLab is extremely active disseminating information to the scientific, professional, and general public through publications, conference presentations, both invited as well as contributed. Several articles were published during the reporting period, one of which recorded 710 hits within 5 months after publication. Dr. Mitchell gave invited presentations at national and international conferences, graduate students won awards for their research at national conferences as well as departmental research retreats, contributions were made to the SCRILED websites, and findings of the past year were communicated to commercial stakeholders. Dr. Mitchell is regularly quoted in the mass media on topics ranging from LEDs to controlled-environment agriculture, and is in constant demand from entrpreneurs, lighting companies, and growers regarding supplemental or sole-source lighting, hydroponics, aquaponics, and CEA. The CAMLab never turns down a request to give a public tour of our facilities to visiting school, church, or professional groups. CAMlab participated heavily in developing a review article entitled "LEDs in Horticulture" that will be published in Horticultural Reviews early in 2015. What do you plan to do during the next reporting period to accomplish the goals? For the SCRILED project, efforts to optimize yield and minimize energy utlization will be integrated with investigations of spectral quality on fruit nutraceutical and flavor qualities. Pending the outcome of present fruit analysis for nutraceutical content of UV-irradiated tomato plants/fruits, followup UV studies may be conducted to determine if broadband UV effects are due solely to UV-B radiation, or if UV-A alone, or even elevated blue light can achieve similar, desired results. New LED towers will be brought into service with capability to independently modulate levels of blue, red, and far-red wavebands. Red/blue ratios, red/far-red, and/or red/blue/far-red ratios will be manipulated to improve the quality and/or flavor of high-wire greenhouse tomato fruit, especially during the off-season for garden-grown tomatoes in cloudy, northern climates. For the cuvette portion of the LED project, proof-of-concept experimentation with sole-source-lighted, hydroponic lettuce crops will be conducted in the modified, retrofitted LED cuvette to characterize, and optimize, light/CO2/temperature interaction during the three main phases of the lettuce growth curve: lag, exponential, and plateau phases. during each phase, light-response curves will be determined, and light, CO2, and temperature will be minimized. Crop-stand photosynthetic rates will be monitored constantly throughout crop production (about 30 days), and energy-expensive resources will be conserved when plants are not responsive to optimizing conditions. Flow rate of atmosphere through the cuvette will be modified daily to maintain constant delta CO2 in the differential infrared gas analyzer connected to the outlet gas stream and the bypass gas stream from the cuvette. thus, flow rates will be very slow when seedlings are small, and will be ramped up as needed when plants enter exponential growth. The mass-flow component of the cuvette system not only will modulate atmosphere flow throough the cuvette appropriately, it will challeng the crop stand regularly with up/down increments of CO2, PPf, and/or temperature to give real-time optimization of the plant-growth environment that otherwise would take months to years to identify using traditional growth-analysis methods.

Impacts
What was accomplished under these goals? For propagation of tomato seedlings in the greenhouse, supplemental lighting (SL) enhanced seedling production during months of the year having low ambient solar light levels. Effects of different red : blue ratios of SL from LEDs were season specific, but stimulation of seedling growth from LEDs generaly responded linearly to total DLI. The addition of blue light to SL has potential to stimulate seedling growth compared to B-deficient SL treatments in seasonal climates with highly variable daily solar DLI. Overall, 5% blue / 95% red light gave the best growth responses across seasons. The greatest growth benefits of SL occurred during periods of low ambient DLI. For grow-out studies of high-wire tomato in the greenhouse, intracanopy lighting from LED towers (ICL-LEDs) was compared with that from Philips interlights + overhead high-pressure sodium lamps (hybrid lighting), overhead high-pressure sodium lighting (OH-HPS), and unsupplemented controls. All SL treatments gave significantly higher fruit yield than did unsupplemented controls, but yield was not different among SL treatments,which included OH-HPS, ICL-LED, and hybrid SL. However, electrical energy consumption averaged 33 kWh/d for OH-HPS, 22 kWh/d for hybrid lighting, and 13 kWh/d for ICL-LED. Only 38% of the energy consumption for the hybrid lighting system was due to LEDs. The rest was for HPS. Net photosynthesis declined from upper to lower leaf layers within high-wire tomato foliar canopies for all treatments, but especially controls receiving no SL, as a result of mutual leaf shading. ICL-LED and the interlighting component of hybrid lighting gave the highest photosynthetic light-reponse curves (LRCs) for photosythesis, but controls and OH-HPS gave the lowest LRCs. Higher source acticvity resulting from ICL does not necessarily lead to yield increases. However, energy for lighting diefinitely is saved. Because greenhouse tomatoes have a stigma of poor quality and flavor relative to garden-grown tomatoes, and because greenhouse glass does not allow solar UV-B radiation to transmit into the greenhouse, a greenhouse was equipped with UV-emitting lamps with and without a transparent mylar barrier. The lamps emitted broad-band UV-A + UV-B radiation, and the mylar filters out the UV-B component of UV. Non-UV-irradiated controls were run simultaneously, and fruits harvested from all three greenhouse treatments were compared with fruits harvested from garden-grown tomato plants during the growing season. The daily UV integral applied in the greenhouse was the same as what would be received in the field on June 21. Analysis of fruits indicated that broad-band UV treatment reduced fruit mass 20% but stimulated ascorbic acid content 31% relative to controls. Brix, titratable acidity, and pH were not affected by UV treatment. The fruit content of phenolics such as Quercitin-3-O-glucoside produced by plants as a sun screen was stimulated 50% in broadband UV-supplemented fruits. Naringenin-7-O-glucoside was stimulated less that half of that amount. Additional phenolic compounds under investigation include Quercitin-3-O--rutinoside, Kampferol-O-rutinosode, and Naringenin chalcone. In a project to integrate an LED light array with a hydroponics system, a gas-exchange cuvette, and an open gas-exchange system, integration tests were performed with plants early in the reporting period. the overall system could monitor photosynthetic rate of hydroponic lettuce crops growing under red + blue LED lighting. However, leak rates of CO2-enriched air through the cuvette were too high to detect photosynthesis of young crops during the lag phase of crop development. The cuvette therefore, was modified and retrofitted to be much more leak resistant so that CO2/air mixtures can be flowed through the cuvette at slow flow rates to detect CO2 drawdown at an early stage of crop development without losing most of the flowing atmosphere between the inlat and the outlet of the cuvette. Because the cuvette also heats up as the PPF of LED light is ramped up, an active thermal-control system also is being installed within the chamber. The control system includes an external heating-cooling-circulating water bath, copper tubing installed within the cuvette space, and fans that turbulently mix air in the chamber between inlet and outlet. A manifold also is being constructed to distribute inlet air with controlled CO2 content across the width of the chamber, The reconfigured chamber is being tested or uniformity of growth across and along the rectangular cuvette space.

Publications

• Type: Journal Articles Status: Published Year Published: 2014 Citation: Yang, Y., G.D. Massa, and C.A. Mitchell. 2014. Temperature DIP at the beginning of the photoperiod reduces plant height but not seed yield of maize grown in controlled environments. J. Industrial Crops and Products 53: 120-127.
• Type: Journal Articles Status: Published Year Published: 2014 Citation: Poulet, L., G.D. Massa, R.C. Morrow, C.M. Bourget, R.M. Wheeler, and C.A. Mitchell. 2014. Significant reduction in energy for plant-growth lighting in space using targeted LED lighting and spectral manipulation. Life Sciences in Space Research 2: 43-53.
• Type: Journal Articles Status: Published Year Published: 2014 Citation: Gomez, C. and C. Mitchell. 2014. Supplemental lighting for greenhouse-grown tomatoes: intracanopy LED towers vs. overhead HPS lamps. 2014. Proc. IS on New Technol. for Env. Control, Energy-Saving and Crop Prod. in Greenhouse and Plant Factory-GreenSys 2013, Eds.: Jung Eek Son et al. Acta Hort. 1037, ISHS: 855-862.

Progress 10/01/12 to 09/30/13

Outputs
Target Audience: The academic and industrial horticultural science community focused on use of controlled environment crop production was the target audience primarily served by our efforts during the past reporting year. Peer researchers at other academic institutions worldwide working on similar topic areas were served via our participation in national and international conferences as well as peer-reviewed publications from our laboratory. The greenhouse grower industry as well as LED companies and entrepreneurs were served via more informal outreach efforts including websites, popular news releases, magazines, etc. Emails and phone calls from vendors, growers, entrepreneurs, and the public were served via provsion of information, direction, and advice. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? The NIFA SCRILED project has generated significant opportunities for training and professional development of students during the reporting period. The PhD graduate student (C. Gomez) responsible for determining effects of LED and HPS supplemental lighting on yield and productivity of greenhouse tomato employed seven part-time student workers during the past year in various tasks related to harvest, experiment maintenance, data collection, data entry, etc. One of those undergraduate students (M. Dzakovich) also did an undergraduate thesis project on the topic of quality attributes of tomato fruits related to spectral quality and will follow up with a Master’s degree thesis project that will be an extension of his undergraduate project. Three graduating part-time student workers have been encouraged to seek advanced training and asked for letters of recommendation for graduate school or medical school. PhD candidate C. Gomez participated in an international greenhouse conference and made an oral presentation to be published in the conference proceedings. For the NASA FSB project, Electrical Engineering Technology senior D. Lotz and Mechanical Engineering senior C. Cheng collaborated in integrating the LED-cuvette-hydroponics system for monitoring crop gas exchange. Letters of recommendation for these students helped one get a summer internship and the other a permanent position. The summer internship also will turn into a permanent position. How have the results been disseminated to communities of interest? A stakeholder conference of greenhouse growers and supporting industry was hosted at Purdue University in June of 2013 in connection with the NIFA SCRILED project. The academic and industrial partners reported to the stakeholders on progress over the past year, and the stakeholders gave the partners recommendations regarding industrial application of greenhouse LED supplemental lighting systems. In addition, regular tours of the tomato-lighting project are given to visiting school, church, and administrative groups. Several invited and contributed presentations from the project were made at the GreenSys2013 conference in Jeju, Korea in October. The project website remains active and is a common referral site for the steady stream of inquiries that come from entrepreneurs, growers, and the general public regarding LEDs and plant growth. Each site of the SCRILED project continues to publish articles in peer-reviewed scientific journals, and feedback, inquiries, and invitations come back to the co-investigators in response to published articles. The entire partnership of the SCRILED project has been involved since summer of 2013 drafting sections of a review article entitled “LEDs in Horticulture” that will be submitted to Horticultural Reviews by the end of 2013. For the Fundamental Space Biology project, the entire reporting period was occupied by assembly, integration, and trouble shooting of the gas-exchange cuvette/LED system. Several tours and briefings of researchers and University administrators regarding future capabilities of the system were conducted during the reporting period. What do you plan to do during the next reporting period to accomplish the goals? For the SCRILED project, physiological studies will be conducted during the next reporting period seeking new information that will lead to improved lighting protocols to enhance the energy efficiency of greenhouse supplemental lighting and/or decrease energy inputs for LED supplemental lighting to maintain or enhance the quantity and quality of tomato-fruit yield. Focus will be on LED intracanopy supplemental lighting. Since previous studies have utilized only 95% red / 5% blue LED lighting, future studies will compare that R/B ratio with 100% red supplemental lighting as well as with 10, 20, or 30% blue LED lighting. Effects on fruit set, yield, and quality will be investigated at different times of year. Intracanopy LED lighting also will be applied to different vertical “zones” of a high-wire crop profile to determine which zones are most important to receive supplemental lighting. The findings may lead to minimal energy expenditure for lighting without compromising fruit quality or yield. A valuable tool to be used for all of these studies will be a portable, clip-on, leaf gas-exchange cuvette that not only measures photosynthetic rates but also leaf stomatal conductance and leaf fluorescence. Light-saturation curves will be established for leaves of different physiological ages within the high-wire profile and with different histories of supplemental lighting (e.g., none, HPS, different R/B ratios of LED lighting). New LED towers will be acquired with capability to emit far-red (FR) as well as R and B light. Effects of R/FR ratios on flower and fruit set as well as fruit number, fruit mass, and fruit quality also will be investigated. Separate UV-A and UV-B studies will be conducted in the greenhouse to determine effects of UV type and dose on various yield and quality parameters of tomato fruits otherwise overhead-lighted with HPS lamps during low-DLI seasons. Both organoleptic as well as physico-chemical metrics of fruit quality will be measured. If elevated levels of blue LED light also show promise to improve quality attributes of tomato fruit, future UV studies may be conducted in combination with LED studies. UV-emitting LEDs exist but are very expensive and low on the energy-efficiency scale. Finding a productive application for UV-emitting LEDs in the greenhouse industry could accelerate development of the UV LED industry as well as improve the quality of greenhouse produce. For the FSB cuvette project, completion of system integration will enable trials to begin during the next reporting period using hydroponic leaf lettuce as a model plant system. Lettuce seedlings will be transplanted to the hydroponics system when very small. As the fixed-spacing seedlings grow incrementally each day, their photosynthetic area will increase and the plants will grow closer together until they eventually close their foliar canopy on the hydroponic-lid surface, after which all LED photons will fall only on photosynthetic surface, when maximum energy utilization will then occur. The gas-exchange system will register small increases in CO2 uptake in the light at 15-second intervals throughout each day of the lettuce growth cycle. When the crop has passed the end of lag phase, as indicated by a sharp increase in photosynthetic rate (Pn), the computer-controlled mass-flow-control system will be programmed to open the mass-flow valve to different extents leading to elevated CO2 being injected into the inlet air stream to the cuvette. The system then will be checked for ability to detect and quantify different steady-state Pn levels related to CO2 level as well as to light intensity, different R/B ratios of LED light, and different, settable cuvette temperatures. A system-development article will be published during the next reporting period demonstrating the environmental-control/crop- response capabilities of the integrated system. Once this is done, the system will be used subsequently to investigate energy-saving protocols for growing this model crop in terms of minimum useful light level, appropriate R/B ratio at different stages of crop development, and appropriate CO2 level to combine with minimal light.

Impacts
What was accomplished under these goals? For the SCRILED project, the Purdue Mitchell lab conducted two half-year high-wire tomato-production experiments, one initiated in the summer and terminated in winter, and the other initiated in the winter and terminated in summer. Supplemental lighting either from overhead high-pressure sodium (HPS) lamps or from intracanopy light-emitting diodes (LEDs) was applied to achieve a total (solar + supplemental) target daily light integral (DLI) of 25 μmol/m2/s either in the presence of declining or increasing natural solar DLI, and crop yield and productivity responses to the supplemental lighting treatments were compared with those from unsupplemented controls. For the summer-to-winter experiment, supplemental lighting increased fruit yield 60-80% relative to that of controls due to a combination of more and slightly larger fruit, even though the harvest periods were identical in length. Even though fruit yield was not different between HPS and LED supplemental lighting treatments in that experiment, the LED treatments used 55% less electrical energy for lighting, and the lighting cost per fruit was almost 3 times less for LED than for HPS-supplemented plants. For the winter-to-summer production experiment, supplemental lighting did not give significantly more yield than controls. This was most likely due to unusually high solar DLI from the end of March to the end of June in 2013, much higher solar than during 2012. However, the experiment confirmed that LED lighting consumed only 27% of the energy used by HPS lighting to achieve equivalent yields. A propagation experiment conducted for 2 weeks per month over a 12-moth period compared effects of HPS, control, or three different red:blue ratios of overhead supplemental LED lighting on early seedling growth of six different tomato cultivars . A supplemental DLI of 6 mol/m2/day was provided to seedlings growing in the greenhouse under seasonally changing solar DLIs from January through December. During all months of the year, light quality had a significant effect on one or more growth metrics of young tomato transplants, but growth responses to light quality differed across seasons. In a parallel effort to evaluate potential effects of supplemental lighting per se as well as to compare spectral quality of supplemental lighting on tomato fruit quality attributes, both organoleptic (OL) taste panels as well as physico-chemical (PC) tests were performed on ripe fruits two days post-harvest. The quality attributes color, aroma, texture, sweetness, acidity, aftertaste, and overall acceptance were compared for HPS, LED, and control fruits for both objective as well as hedonic scales. PC analyses of fruit color, Brix (sugar content), titratable acidity (citric acid equivalents), pH, and EC (overall acidity and ionic charge) were performed on extracts of fruits. The outcome of the OL and PC tests was that there were no bad-tasting tomato fruits from any light treatment, including controls, in either experiment. No OL taste attributes were affected significantly by light treatment or seasonal transition. Although there were some statistically significant differences within certain PC attributes, differences were small and tasters did not detect them. In a project to integrate sole-source LED lighting with an open gas-analysis system for crop-stand photosynthetic rates, a custom-designed cuvette enclosure with a transparent lid was interfaced between an overhead LED array and a recirculating hydroponics unit within a temperature-controlled growth chamber. Adequate sealing between the cuvette, hydroponics lid, and LED array were achieved using a combination of thick, resilient, closed-cell-foam gasket material and pressure clamps, thereby retaining sufficient pressure from the inlet gas stream to adequately return airflow to the gas-analysis system after it passed over the crop surface without requiring booster pumps. Internal air-circulation fans were installed so that CO2 content of outlet air would uniformly represent CO2-removal capacity of the entire crop canopy. A movable thermocouple also was mounted within the cuvette space for monitoring ambient air temperature within the cuvette when LEDs are energized. A Peltier cooling device was obtained for purposes of maintaining temperature setpoint within the cuvette when LEDs are energized. Both differential and absolute infrared gas analyzers were calibrated and repaired in preparation for monitoring net photosynthetic rates of lettuce crops throughout their cropping cycles under different combinations of light intensity, red:blue ratios, and different CO2 concentrations.

Publications

• Type: Journal Articles Status: Published Year Published: 2013 Citation: Gomez, C., R. Morrow, C. Bourget, G. Massa, and C. Mitchell. 2013. Comparison of intracanopy light-emitting diode towers and overhead high-pressure sodium lamps for supplemental lighting of greenhouse-grown tomatoes. HortTechnology 32(1): 93-98.
• Type: Conference Papers and Presentations Status: Awaiting Publication Year Published: 2014 Citation: Gomez, C. and C. Mitchell. 2014. Supplemental lighting for greenhouse-grown tomatoes: intracanopy LED towers vs. overhead HPS lamps. Proc. in Symp. New technologies for environment control, energy-saving and crop production in greenhouse and plant factory. Acta Hort. (in press).
• Type: Conference Papers and Presentations Status: Accepted Year Published: 2014 Citation: Yang, Y., G. Massa, and C. Mitchell. 2014. Temperature DIP at the Beginning of the Photoperiod Reduces Plant Height But Not Seed Yield of Maize Grown in Controlled Environments. Journal of Industrial Crops and Products (accepted pending suitable revision).

Progress 10/01/11 to 09/30/12

Outputs
OUTPUTS: Leaf lettuce was grown hydroponically in a controlled environment under sole-source red-plus-blue light-emitting diodes (LEDs) to determine the lowest irradiance and best red : blue ratio of light to produce acceptable seedlings during the lag phase of crop growth, and an irradiance and red : blue ratio that, together with CO2 enrichment and incremental increases in nutrient concentration, would produce the most productive lettuce crop per unit electrical energy input for crop lighting. Light treatments included 5 or 10 percent blue lighting at the same total irradiance of light. Targeted lighting consisting of switching on LEDs located only directly above individual plants on the LED array was compared with untargeted lighting consisting of all LEDs on the array being switched on all the time during each photoperiod. At the end of the experimental treatment, plants were harvested, leaf area, plant dry weight, and other measures of plant productivity were obtained, and cumulative kilowatt hours of electricity consumed for lighting were recorded. Results of the research were reported to the NCERA 101 Committee on Controlled Environment Technology and Use at Iowa State University and at the annual conference of the American Society for Gravitational and Space Biology in San Jose, California. A high-wire tomato crop was grown in a greenhouse from winter to summer using soilless nutriculture for two commercial tomato cultivars and three supplemental lighting treatments including overhead high pressure sodium (HPS) lighting, intracanopy LED lighting, or no supplemental lighting. A daily light integral of 9 moles per meter squared per day of light was provided to the supplemented crops in addition to natural solar lighting that increased throughout the experimental period. Clusters of tomato fruit were harvested from the bottom up of each plant as they ripened, and plants were defoliated, lowered, and leaned to keep the same total plant height above the greenhouse floor. Productivity was measured in terms of date of first harvest, total fruit number harvested, and total fresh weight of fruits harvested. Results of the research were reported at NCERA 101 and the annual conference of the American Society for Horticultural Science in Miami, Florida. The presenting student won awards at both conferences. For three harvests of the tomato experiment, ripe tomatoes from the two test cultivars, three lighting treatments, and two different greenhouse positions of each light treatment, were subjected to either organoleptic taste panel evaluation by volunteers or to physico-chemical (PC) evaluation. The organoleptic evaluations included 11-point objective as well as 9-point subjective (hedonic) attributes of taste including sweetness, acidity, texture, aroma, color, and overall acceptability. Organoleptic attributes were correlated with PC metrics of total soluble solids, titratable acidity, and pH for purees prepared from whole fruits, as well as color from machine colorimetry of fruits before blending. The results of the research were presented at ASHS. The student presenting the fruit quality attributes won two awards at ASHS. PARTICIPANTS: Lucie Poulet, a master's student majoring in Aerospace Engineering at Purdue University, worked on an assistantship in C. Mitchell's laboratory to evaluate effects of targeted vs. untargeted LED lighting on productivity of lef lettuce as a model photosynthetic crop as well as the comparative energetics of such lighting. Celina Gomez, a PhD student in Horticulture & Landscape architecture at Purdue,worked on an assistantship in C. Mitchell's laboratory comparing effects of LED vs. HPS supplemental lighting on productivity and yield of high-wire tomato grown in a greenhouse during the off-season for tomato in notrthern climates. TARGET AUDIENCES: One target audience is the world-wide space biology and space life support academic communities interested in low-energy, highly effective LED lighting for crops grown in space. Another target audience is the worldwide controlled-environment agriculture academic community interested in energy-efficent crop lighting and commercial greenhouse growers interested in adapting LED supplementl lighting for greenhouse production. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
The lag phase of lettuce growth took 15 days under 5 percent blue : 95 percent red light starting at 75 to 100 micromoles per meter squared per second for 16 hours daily and adding 25 micromoles per day. This lighting regime kept lettuce seedlings short while allowing development of leaf area to support exponential growth 15 days after seeding. Although light utilization was 8 times less efficient during lag assimilating biomass, only 39 percent of total electrical energy was consumed due to the low light intensities used. At 0.75 kilowatt hour per gram dry seedling biomass, the energy efficiency of targeted red plus blue LED lighting was twice that of untargeted lighting but only 77 percent as efficient as untargeted white LED lighting using newer LED technology. The targeted red plus blue LED technology at 0.133 kW per square meter used only 5 percent as much power as HPS growth chamber lamps at 2.7 kW per square meter. In a winter to summer tomato production experiment, LED or HPS supplemented plants yielded fruit 22 to 24 days sooner than did control plants. Light supplemented plants developed 10 to 11 more nodes than did controls, 40 to 45 percent more fruit, and 48 to 56 percent more fruit biomass over 5 months of harvest. Differences between LED and HPS treatments were not statistically significant. Equivalent fruit yield by the LED treatments consumed only 25 percent as much electrical energy as the HPS treatments. LED panels were switched on from the bottom up to keep pace with increases in height of the crop. As lower stems were defoliated, fruit clusters harvested from the bottom up, and indeterminate stems lowered and leaned to maintain constant distance above the greenhouse floor, LED panels were switched off from the bottom up. This capability contributed to the significant energy savings of the LED towers compared to the overhead HPS lamps. LED supplemental lighting is economically promising for off season local production of vine ripened tomato fruits in northern climates. Testing quality attributes of ripened fruits indicated that the cultivar Komeett was superior to Success for aroma and color across several taste panel dates using both objective and hedonic scales, and that cultivar Success seemed more responsive to environmental changes for these attributes. Across both cultivars, both LED and control treatments ranked higher in aroma than did HPS treatments. For acidity, both LED and HPS treatments ranked slightly higher than controls for Komeett, but for Success controls were more acid than LEDs. Texture was not affected by light treatments for Komeett, but for Success controls were highest. For overall acceptance, both LED and control treatments ranked slightly higher than HPS treatments across cultivars on the hedonic scale. For physico chemical analyses, purees of LED treatments tended to have higher electrical conductivity and citric acid content than for the other treatments. LED supplemental lighting had no negative effects on taste attributes during the winter to summer experiment.

Publications

• Schluttenhofer, C.M., G.D. Massa, and C.A. Mitchell. 2011. Use of Uniconazole to control plant height for a controlled environment industrial platform. J. Industrial Crops and Products 33: 720-726.
• Massa, G.D. and C.A. Mitchell. 2012. Sweetpotato vine management for confined food production in a space life-support system. Adv. Space Res. 49: 262-270.
• Mitchell, C., A.J. Both, C. M. Bourget, J.F. Burr, C. Kubota, R.G. Lopez, R.C. Morrow, and E.S. Runkle. 2012. LEDs: The future of greenhouse lighting! Chronica Hort. 52 (1): 6-12.

Progress 10/01/10 to 09/30/11

Outputs
OUTPUTS: Outputs during the reporting period focused on testing of light-emitting diode (LED) techologies for sole-source or supplemental lighting of food crops in controlled environments (growth chambers) and semi-controlled environments (greenhouses), respectively. Plant responses were measured for growth and productivity upon harvest. Additionally, electrical energy consumption in kilowatt-hours was recorded for each light treatment applied. In one project, "smart" overhead LED lighting was compared with conventional overhead LED lighting of leaf lettuce growing hydroponically in a growth chamber. Flash patterns from green LEDs mounted on the arrays were directed downward onto lettuce seedlings during brief dark periods at all stages of crop development from germination to harvest at 21 days. Reflection of green light back from leaves was detected by photodiodes mounted on the array, and a computer-control system then automatically switched on red and blue LEDs only directly above reflecting leaf surfaces. Thus, LEDs switch on selectively so that photosynthetic photons are not wasted in spaces not populated by plant tissues. A large cuvette designed to measure real-time photosynthetic gas exchange of hydroponic crops growing under LED lighting in a flow-through system was tested and found to have design flaws related to not restricting inlet atmosphere flow only across the crop canopy from inlet to outlet and to possible non-uniformity of temperature of outlet sample and reference gas streams. Troubleshooting to identify, test, and correct mechanical-design flaws was conducted throughout the reporting period. In another project conducted in a greenhouse, cultural and lighting systems were set up for both propagation and production of high-wire tomato crops. Several cultivars of indeterminate tomato scions and a common rootstock were propagated under different ratios of red and blue supplemental LED lighting across seasons of changing solar spectral composition and irradiance. High-pressure sodium (HPS) and an unsupplemented treatment were established on a greenhouse bench as controls. A quantum-sensor/data-logging system was set up to record daily light integral (DLI) under each lighting treatment across seasons for 14-day transplant-production experiments. A soilless fertigation/high-wire trellising system for growout and tomato-fruit production also were established in the greenhouse in preparation for intracanopy LED lighting systems that were designed and under construction during the reporting period. Traditional overhead HPS lighting also was established above one row of tomatoes as a control. Two invited presentations were made at the Industrial Technology Research Institute in Taiwan, and two more at the Plant and Food Research Institute in New Zealand. Three contributed presentations were made at the NCERA-101 Committee on Controlled Environment Use and Technology meeting at Iowa State University, one presentation was made at GreenSys2011 in Halkidiki, Greece, and another at the American Society for Horticultural Science annual conference in Waikoloa, Hawaii. All presentations were on the theme of LEDs for plant growth. PARTICIPANTS: For the sole-source LED lighting project sponsored by NASA, Ms. Lucie Poulet, an Aerospace Engineering graduate student at Purdue University, worked on a half-time research assistantship during the reporting period and is developing a master's thesis project related to "smart" lighting of hydroponic lettuce crops grown in controlled environments. Also on that project, Mr. Isaac Traylor, a Senior Electrical Engineering Technology student at Purdue, provided technical and trouble-shooting support for the cuvette and gas-exchange part of that project. For the NIFA SCRI project entitled "Developing LED Lighting Technologies and Practices for the Greenhouse Industry", Ms. Celina Gomez, a Horticulture graduate student at Purdue, worked on a half-time research assistantship and is developing a PhD dissertation on a sub-project entitled "Developing LED Technology for Sustainable Tomato Propagation and Production in Northern Climates". Mr. Michael Dzakovich, a Junior Horticultural Science student at Purdue, supported both the NASA and NIFA projects and is developing an independent research project on value-added food quality in connection with the greenhouse LED tomato project. The following collaborators also contributed to the LED greenhouse supplemental lighting project during the project period: Dr. Roberto Lopez in Horticulture & Landscape Architecture at Purdue is investigating "LEDs for Photosynthetic Lighting of Ornamentals During Vegetative Propagation". Dr. John Burr in the Krannert School of Management at Purdue is addressing "Economic, Sociological, and Life-Cycle Assessment of Introducing LED Lighting Technology into the Greenhouse Industry". Dr. A.J. Both in the Department of Environmental Sciences at Rutgers University is working on "LED Lighting System Testing and Evaluation". Dr. Chieri Kubota in the School of Plant Sciences at the University of Arizona is focused on "LEDs for Photosynthetic Lighting: Supplemental Light Quality Requirement for Vegetable Seedlings Under Different Background Solar Light Integrals". Dr. Erik Runkle in the Department of Horticulture at Michigan State University is "Using LEDs to Determine Effective Red and Far-Red Ratios for Photoperiodic Flowering". Dr. Robert C. Morrow, Manager of Bioproduction Systems, and Mr. C. Michael Bourget, Lead Electrical Engineer, both of the Orbital Technologies Corporation in Madison, Wisconsin, are working with each of the co-Investigators mentioned above to custom design and fabricate LED hardware and software technology for the various LED lighting and supplemental lighting applications in the various collaborating laboratories. TARGET AUDIENCES: The sole-source LED smart-lighting project serves the space advanced life support (ALS) and controlled-environment agriculture (CEA) communities. Smart, close-canopy or intracanopy LED lighting systems have potential to save one to two orders of magnitude electrical energy compared to traditional sole-source overhead plant lighting with high-intensity discharge lamps. Independent, bioregenerative life support in space presently is limited by the high energy costs of crop lighting for food production, air revitalization, and water purification. Combining the cool photon-emitting surfaces of LEDs that both allow close placement of emitters to leaf surfaces as well as to match the absorption spectra of targeted plant pigments with selective, targeted lighting only onto leaf surfaces without wasting light energy by irradiating empty spaces will enable energetically sustainable crewed bases at distant space destinations such as the moon and Mars, without frequent resupply from Earth, and will enable ground-based CEA to be sustainable and economically viable, which it never has been before because of high lighting costs. The project for LED lighting to supplement solar radiation during low-light times of the year in greenhouses will serve both ornamental and vegetable greenhouse industries. Northern growers typically cannot afford to grow greenhouse vegetables such as tomato during low-light seasons without supplemental lighting. Innovative designs of LED arrays for propagation that do not block natural solar light while applying supplemental or daylength-extending overhead lighting will allow U.S. growers to tone and finish high-quality transplants for lower energy costs and higher profits. For grow-out and production of high-wire crops such as tomato, pepper, and cucumber, intracanopy lighting from LED light towers distributed vertically throughout the canopy and horizontally along entire rows without photons escaping into aisles will distribute photosynthetic photons only where they are needed and with much more effectiveness than using traditional overhead lighting systems with very hot lamps. A subset of project investigators met with industry stakeholders during July, 2011 at the OFA short course in Columbus, Ohio to informally update the stakeholders on progress in the LED supplemental lighting project. Project investigators also convened at the NCERA-101 meeting at Iowa State University in April, 2011 to compare experiences and present results of early project work to peers in controlled environment agriculture research. The international cademic research community was updated on project progress by individual and joint oral presentations at GreenSys2011 in Greece during June and a joint presentation made at ASHS 2011 in Hawaii in October. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
Two sole-source LED arrays were examined for software and hardware issues limiting detection of plant position and size. Collimating lenses for red LEDs were removed so that arrays could be placed closer to the crop surface with uniform irradiation and improved red-blue mixing. Because structural cross bars and edges of the arrays caused false-positive detections, a dark-scan function was programmed into the control system so that detection scans without plants could be automatically subtracted from scans with plants. Grey plugs supporting seedlings on an otherwise flat-black hydroponics lid provided sufficient green reflectance to enable detection of small seedlings before sufficient leaf tissue developed. Non-uniform reporting of electrical energy utilization among the four LED panels of an array was corrected by replacing faulty inductors. When both arrays were controlled simultaneously with the control computer, additional energy-use-reporting discrepancies occurred and were being addressed at the end of the reporting period. Two preliminary plant experiments indicated that the "smart" mode of lighting saves more than an order of magnitude energy compared to traditional HPS lighting, and significantly more energy than close-canopy LED lighting energized fully throughout crop production. Cuvette trouble shooting confirmed that the infrared gas-analysis component of the system was working properly and that difficulties were associated with 1) a Peltier cooling unit located too close to inlet air, thereby cooling it, 2) potential for some cooled inlet air to short circuit directly to the outlet port without encountering the lighted crop surface, thereby leading to a temperature discrepancy between sample and reference gas streams, and 3) a route for additional inlet air to pass behind the LED array and go directly to the outlet port without processing. One solution is to redesign part of the large cuvette. Another is to develop a second, smaller cuvette that snaps directly onto the hydroponics lid. The latter option was in progress at the end of the reporting period. Transplants of several commercial tomato cultivars were grown in a greenhouse during spring and fall when natural solar radiation was increasing or decreasing, respectively. In all cases, providing supplemental LED lighting with a daily light integral of 5.76 moles per-meter-squared-per day from open-bar, overhead LED arrays that allow sunlight to pass between bars stimulated transplant dry-weight gain. Red/blue ratio was varied to determine when during the year additional blue is needed. Red alone was adequate during long-photoperiod, "blue-sky" days. During early spring, blue LED light made stems shorter and stockier, and leaves greener than for all other treatments. Unsupplemented and HPS-supplemented controls were the smallest and second smallest transplants in all cases during the transition from spring to fall. A high-wire tomato growout system was established in the greenhouse consisting of three rows with either overhead HIDs, intracanopy red + blue LEDs, or unsupplemented controls ramdomized among and within rows.

Publications

• Mitchell, C.A., Both, A.J., C.M. Bourget, J.F. Burr, C. Kubota, R.G. Lopez, R.C. Morrow, E.S. Runkle. 2011. Developing LED lighting technologies and practices for greenhouse crop production. 2011 ASHS Annual Conference, Waikoloa, Hawaii, September 25-28, Oral Session Abstract book, P. 87.
• Schluttenhoffer, C., Massa, G.D., and Mitchell, C.A. 2011. Use of uniconazole to control plant height for an industrial/pharmaceutical maize platform. Industrial Crops and Products 33: 720-726.
• Mitchell, C.A., A.J. Both, C.M. Bourget, J.F. Burr, C. Kubota, R.G. Lopez, G.D. Massa, R.C. Morrow, E.S. Runkle. Developing LED lighting practices and technologies and practices for greenhouse crop production. 2011. GreenSys2011, Halkidiki, Greece, June 5-10, Abstract book, P. 55

Progress 10/01/09 to 09/30/10

Outputs
OUTPUTS: Experiments were conducted to test effects of daily temperature dip and pot size on yield of corn in controlled environments; to determine optimum concentration of fertigation solution on yield of sweetpotato in greenhouses; to find the optimum temperature regime for yield and quality of strawberry in controlled environments, and to select cultivars of sesame for productivity and yield in greenhouses. I represented ASHS at the Council of Agricultural Science and Technology (CAST) meeting in St. Louis, October 6-9, 2009. A multi-disciplinary, multi-institutional proposal was submitted to USDA's Specialty Crops Research Initiative (SCRI) program January 13, 2010. I served on an SCRI review panel in Washington DC March 15-18, 2010. Scientific findings were reported at the annual conference of the American Society for Gravitational and Space Biology (ASGSB) in Raleigh, North Carolina, November 5-8, 2009; at the Lunar Exploration Analysis Group (LEAG) in Houston, Texas, November 16-19, 2009; at the North Central Extension & Research Activity Committee (NCERA-101) on Controlled Environment Technology and Use in Madison, Wisconsin, March 20-23, 2010; and at the American Society for Horticultural Science (ASHS) annual conference in Palm Desert, California, August 2-5, 2010. A colloquium entitled "Closed Loop Regenerative Life Support for Sustainable Habitation in Space and on Earth" was organized and moderated for ASGSB 2009, and the proceedings of that session were edited in preparation for publication. A scientific article was published in the Journal Advances in Space Research (JASR), two others were submitted to JASR and the Journal of Industrial Crops and Products, and statistical analyses were conducted for two additional articles. An Electrical Engineering Technology graduate student and a Mechanical Engineering Technology graduate student working on a crop gas-exchange cuvette developed thesis projects, and successfully defended their theses. A Horticultural Science undergraduate was mentored in a guided research project, a Landscape Architecture undergraduate student was supervised for general laboratory assistance, an Electrical Engineering Technology undergraduate student became employed to help complete the gas-exchange project, an Aerospace Engineering graduate student joined the lab to integrate technological and biological aspects of the crop/gas-exchange/LED project, and a research scientist who coordinates all lab activities was consulted. We participated in the Indiana Horticultural Congress (Indianapolis, January 19-21, 2010), and a public outreach presentation entitled "Life Support in Space" was made at the Science Cafe (Lafayette, IN, March 9, 2010). A custom-designed crop gas-exchange cuvette was designed and fabricated to our specifications, and two "smart" lighting arrays consisting of light-emitting diodes (LEDs) and computer controls also were designed and fabricated to our specifications. One LED array was installed in the gas-exchange cuvette and the other in a growth chamber in preparation for studies to rapidly optimize environmental conditions for sustainable crop production in controlled environments. PARTICIPANTS: Experiments were conducted to test effects of daily temperature dip and pot size on yield of corn in controlled environments; to determine optimum concentration of fertigation solution on yield of sweetpotato in greenhouses; to find the optimum temperature regime for yield and quality of strawberry in controlled environments, and to select cultivars of sesame for productivity and yield in greenhouses. I represented ASHS at the Council of Agricultural Science and Technology (CAST) meeting in St. Louis, October 6-9, 2009. A multi-disciplinary, multi-institutional proposal was submitted to USDA's Specialty Crops Research Initiative (SCRI) program January 13, 2010. I served on an SCRI review panel in Washington DC March 15-18, 2010. Scientific findings were reported at the annual conference of the American Society for Gravitational and Space Biology (ASGSB) in Raleigh, North Carolina, November 5-8, 2009; at the Lunar Exploration Analysis Group (LEAG) in Houston, Texas, November 16-19, 2009; at the North Central Extension & Research Activity Committee (NCERA-101) on Controlled Environment Technology and Use in Madison, Wisconsin, March 20-23, 2010; and at the American Society for Horticultural Science (ASHS) annual conference in Palm Desert, California, August 2-5, 2010. A colloquium entitled "Closed Loop Regenerative Life Support for Sustainable Habitation in Space and on Earth" was organized and moderated for ASGSB 2009, and the proceedings of that session were edited in preparation for publication. A scientific article was published in the Journal Advances in Space Research (JASR), two others were submitted to JASR and the Journal of Industrial Crops and Products, and statistical analyses were conducted for two additional articles. An Electrical Engineering Technology graduate student and a Mechanical Engineering Technology graduate student working on a crop gas-exchange cuvette developed thesis projects, and successfully defended their theses. A Horticultural Science undergraduate was mentored in a guided research project, a Landscape Architecture undergraduate student was supervised for general laboratory assistance, an Electrical Engineering Technology undergraduate student became employed to help complete the gas-exchange project, an Aerospace Engineering graduate student joined the lab to integrate technological and biological aspects of the crop/gas-exchange/LED project, and a research scientist who coordinates all lab activities was consulted. We participated in the Indiana Horticultural Congress (Indianapolis, January 19-21, 2010), and a public outreach presentation entitled "Life Support in Space" was made at the Science Cafe (Lafayette, IN, March 9, 2010). A custom-designed crop gas-exchange cuvette was designed and fabricated to our specifications, and two "smart" lighting arrays consisting of light-emitting diodes (LEDs) and computer controls also were designed and fabricated to our specifications. One LED array was installed in the gas-exchange cuvette and the other in a growth chamber in preparation for studies to rapidly optimize environmental conditions for sustainable crop production in controlled environments. TARGET AUDIENCES: Day-neutral Seascape strawberry was grown for 282 days under 10-h photoperiods at day/night temperatures (degrees C) of 16/8, 18/10, or 20/12. Fruit were weighed and counted, and pH, Brix, and titratable acidity were measured. The coolest regime produced the largest fruit, but the middle regime produced the highest fruit weight. Plants grown warm fruited earlier than those grown cooler. Brix averaged 10.1 for the first half of the harvest period but dropped to 8.4 during the latter half, indicating that fruit became less sweet as plants aged. Titratable acidity averaged 0.6 but increased slightly during the middle harvest period. The highest yielding group (18/10) had the lowest Brix and average tritatable acidity, indicating that fruit became less sweet over time of production. Fruit from the coolest treatment had higher Brix and lower titratable acidity and were higher in pH than fruit from the other treatments. Sweetpotato vines were grown in Profile at different dilutions of a 15-5-15 fertilizer formulation that is 1000 mg/L at full strength. Root yield was higher at half-strength fertilizer than at full, but declined sharply at a quarter. Root / shoot ratio was higher at all fertilizer concentrations than full strength. Semi-dwarf corn line PI 587154 was grown in a growth chamber in large or small pots with or without a daily temperature dip for the first 2 hours of light. Corn yields as well in small pots as in large pots, while plants receiving a temperature dip at the beginning of the photoperiod were shorter than with normal day/night temperatures while seed yield was unaffected. Effects of metal halide or high-pressure sodium lamps on corn growth and yield were measured in a standardized growth room. Differences in long-wave radiation emanating from different lamp types heated plants and soil differentially and complicated apparent spectral effects. A crop gas-exchange cuvette and light-emitting diode (LED) array were integrated with a computer-control system and sensors, which includes a video camera for internal monitoring of crop growth, temperature and humidity probes, differential and absolute gas analyzers, and mass-flow controllers, thereby allowing rapid equilibration to carbon dioxide set points and real-time measurement of gas exchange throughout crop production. An electronic cooling system for the cuvette is being completed, and the smart lighting system is being calibrated so that LEDs will be energized only directly above where leaves are detected. Prototypes of overhead LED arrays were received from the Orbital Technologies Corporation and tested in a greenhouse with lettuce. Several recommendations for improvement of the prototypes were given to ORBITEC prior to startup of a funded project. A collaboration was begun with Dow Agro-Sciences to improve yield of corn grown in controlled environments. Sesaco provided six lines of sesame for tests in the greenhouse. All lines performed well with both peat-based and calcined-clay media, but line TKHAd yielded the highest seed weight. PROJECT MODIFICATIONS: Chiam, T.C., Yih, Y., and Mitchell, C.A. (2010). Development of theoretical approaches to the control of a water-treatment system. Adv. Space Res. 46: 1418-1426. Massa, G.D., Santini, J.B., and Mitchell, C.A. (2010). Minimizing energy utilization for growing strawberries during long-duration space habitation. Adv. Space Res. 46: 735-743. Chiam, T.C., Yih, Y., and Mitchell, C.A. (2010). Control policies for a water-treatment system using the Markov decision process. Part II: simulation and analysis. Habitation 12: 27-32. Chiam, T.C., Yih, Y., and Mitchell, C.A. (2010). Control policies for a water-treatment system using the Markov decision process. Part I: mathematical formulation. Habitation 12: 21-26.

Impacts
Day-neutral Seascape strawberry was grown for 282 days under 10-h photoperiods at day/night temperatures (degrees C) of 16/8, 18/10, or 20/12. Fruit were weighed and counted, and pH, Brix, and titratable acidity were measured. The coolest regime produced the largest fruit, but the middle regime produced the highest fruit weight. Plants grown warm fruited earlier than those grown cooler. Brix averaged 10.1 for the first half of the harvest period but dropped to 8.4 during the latter half, indicating that fruit became less sweet as plants aged. Titratable acidity averaged 0.6 but increased slightly during the middle harvest period. The highest yielding group (18/10) had the lowest Brix and average tritatable acidity, indicating that fruit became less sweet over time of production. Fruit from the coolest treatment had higher Brix and lower titratable acidity and were higher in pH than fruit from the other treatments. Sweetpotato vines were grown in Profile at different dilutions of a 15-5-15 fertilizer formulation that is 1000 mg/L at full strength. Root yield was higher at half-strength fertilizer than at full, but declined sharply at a quarter. Root / shoot ratio was higher at all fertilizer concentrations than full strength. Semi-dwarf corn line PI 587154 was grown in a growth chamber in large or small pots with or without a daily temperature dip for the first 2 hours of light. Corn yields as well in small pots as in large pots, while plants receiving a temperature dip at the beginning of the photoperiod were shorter than with normal day/night temperatures while seed yield was unaffected. Effects of metal halide or high-pressure sodium lamps on corn growth and yield were measured in a standardized growth room. Differences in long-wave radiation emanating from different lamp types heated plants and soil differentially and complicated apparent spectral effects. A crop gas-exchange cuvette and light-emitting diode (LED) array were integrated with a computer-control system and sensors, which includes a video camera for internal monitoring of crop growth, temperature and humidity probes, differential and absolute gas analyzers, and mass-flow controllers, thereby allowing rapid equilibration to carbon dioxide set points and real-time measurement of gas exchange throughout crop production. An electronic cooling system for the cuvette is being completed, and the smart lighting system is being calibrated so that LEDs will be energized only directly above where leaves are detected. Prototypes of overhead LED arrays were received from the Orbital Technologies Corporation and tested in a greenhouse with lettuce. Several recommendations for improvement of the prototypes were given to ORBITEC prior to startup of a funded project. A collaboration was begun with Dow Agro-Sciences to improve yield of corn grown in controlled environments. Sesaco provided six lines of sesame for tests in the greenhouse. All lines performed well with both peat-based and calcined-clay media, but line TKHAd yielded the highest seed weight.

Publications

• Chiam, T.C., Yih, Y., and Mitchell, C.A. (2010). Development of theoretical approaches to the control of a water-treatment system. Adv. Space Res. 46: 1418-1426.
• Massa, G.D., Santini, J.B., and Mitchell, C.A. (2010). Minimizing energy utilization for growing strawberries during long-duration space habitation. Adv. Space Res. 46: 735-743.
• Chiam, T.C., Yih, Y., and Mitchell, C.A. (2010). Control policies for a water-treatment system using the Markov decision process. Part II: simulation and analysis. Habitation 12: 27-32.
• Chiam, T.C., Yih, Y., and Mitchell, C.A. (2010). Control policies for a water-treatment system using the Markov decision process. Part I: mathematical formulation. Habitation 12: 21-26.

Progress 10/01/08 to 09/30/09

Outputs
OUTPUTS: In preparation for the emerging pharma-crop industry, corn was grown to harvest maturity in a growth chamber under optimizing environmental conditions intended to reduce plant height in limited-height, contained growth environments without compromising seed yield. Day/night temperature was temporarily reversed early in the photoperiod in effort to accomplish these goals compared to traditional temperature regimes. Corn also was grown in a greenhouse comparing effects of the growth retardant Sumagic on growth and seed yield. For the NASA Specialized Center of Research and Training in Advanced Life Support, day-neutral strawberry was grown in growth chambers to determine effects of different day/night temperature regimes on fruit yield and quality over an extended harvest period. The aggressive, sprawling vine growth of sweetpotato was adapted for more contained production within controlled environments by a combination of vine training (vertical helical winding) and lateral-shoot pruning. Media and fertilizer concentration were varied in effort to promote storage-root production while minimizing luxuriant shoot growth. Sweetpotato, strawberry, and corn-growth data were compiled, analyzed statistically, and prepared for publication. A survey of tomato cultivars with compact growth habits and high fruit yield was conducted in a greenhouse under different shoot-management techniques to find productive cultivars best suited for subsequent growth studies with narrow-band lighting from light-emitting diodes (LEDs) in a controlled environment. Subsequent tests grew tomato selections hydroponically in a growth chamber with red and blue LEDs providing the sole source of light for crop production. A small crop-stand growth chamber/gas-exchange cuvette accommodating hydroponic culture and intracanopy (vertical strips) LED lighting of planophile crops was constructed to specifications and integrated into a gas-exchange system that will allow measurement of real-time photosynthetic response to variables such as light intensity and quality, temperature, and carbon dioxide continuously throughout the life cycle of the crop. A second chamber/cuvette is under construction that will accommodate overhead, "smart" LED lighting of low-profile crops that detects and selectively targets only plant tissues within the lighting field. Plans were drafted for the development of a waste-energy-heated, year-round, crop-growth facility at Purdue University in conjunction with the campus power plant. Research interests and results were shared with the public through facilities tours and a website, and with the scientific community through presentations, station reports, and informal discussions at the Indiana Horticultural Congress, the NCERA-101 Committee on Controlled Environment Technology and Use, Greensys 2009: the International Symposium on High Technology for Greenhouse Systems, the annual meeting of the NASA Lunar Science Institute, the annual meeting of the American Society for Horticultural Science, the annual meeting of the American Society for Gravitational and Space Biology, and a meeting of the Lunar Exploration Analysis Group. PARTICIPANTS: Individuals working on the projects include: Gioia Massa, Research Scientist, Elaine Chase, Technician, Keith Spence and Ben Riggs, Graduate Researchers, Craig Schluttenhofer, Daniel McMillan, and Ashley Hudson, Undergraduate Research Assistants, Amber Chase, Research Assistant, Chanhoo Chun, Visiting Scientist. Partner Organizations, Collaborators and Contacts include: Robert Morrow and Mike Bourget, Orbital Technologies Corporation, Doug Ausenbaugh, Controlled Pharming Ventures, Patsy Benveniste, Chicago Botanic Garden and Windy City Harvest, Ray Wheeler, Neil Yorio, Gary Stutte and Oscar Monje, Kennedy Space Center and Dynamac Corporation, Bral Spight, UrbanPonics, Robert Richhart, Hoosier Energy Group. TARGET AUDIENCES: Target Audiences for the projects include: Industries with sources of thermal or organic waste, specialty-crop producers and those interested in specialty-crop production in areas where it is economically unfeasible due to limiting heat/light, urban agriculture movements, the plant-made pharmaceutical industry, the lighting industry, and the general public who are interested in crop growth, regenerative life support, and space exploration. PROJECT MODIFICATIONS: There have been no major modifications to the project. The waste-energy leveraged high tunnel project has been modified slightly by reducing the number of proposed tunnels to meet budgetary restrictions. In addition, new collaborators in this project include Bruce Bordelon, small fruits specialist, and Roberto Lopez, Floriculture specialist, both in the Department of Horticulture and Landscape Architecture at Purdue University.

Impacts
Corn grown under optimizing environmental conditions in a growth chamber developed one or two fully seeded ears per plant at yield rates far exceeding those in the field. Root volume (pot size) was not a limiting factor for growth and yield of plants fertigated multiple times per day. Corn grown under brief day/night temperature reversal was shorter, more branched, and typically developed two or three fertile ears per plant. Corn grown in a greenhouse with Uniconazole (Sumagic) applied as a soil drench had reduced height and seed yield in a dose-responsive manner, and favored masculine traits at high UCZ concentrations. Low concentrations reduced plant height significantly while not affecting seed yield. Day-neutral strawberry developed slowest under the coolest temperature regime tested, but produced fruit rated highest for organoleptic quality. A manuscript was prepared for previous studies indicating that strawberry yield was unaffected by short photoperiods, thereby saving considerable energy in controlled environments, and was submitted for publication to a peer-reviewed scientific journal. Comparisons of growth media for sweetpotato led to adoption of Profile calcine-clay granules as a superior choice for growing this storage-root/salad crop. lowering the concentration of injected fertilizer to an intermediate level reduced the vegetation accumulating during crop production without compromising root yield, thereby creating another way to contain vine growth. In the compact tomato yield survey, the productive cherry cultivars Small Fry and Husky Cherry Red were chosen for testing with intracanopy and overhead LED arrays in a growth chamber. Both cultivars flowered and set fruit under narrow-band red/blue lighting, but Small Fry developed severe intumescence (oedema), whereas Husky Cherry Red developed normal growth under the same conditions. A manuscript was prepared, submitted, and published summarizing the advantages of using light-emitting diodes (LEDs) for plant growth. A crop-stand gas-exchange cuvette for small crop stands was designed, constructed, and assembled that accommodates intracanopy LED lighting. Command & control software was developed for the system while mechanical components and analyzers were being integrated. Crop stands growing hydroponically within the closed cuvette can be visualized because an adjustable-height webcam is mounted on a pan & tilt stage adjacent to the growth volume. Mass-flow control was installed for CO2 injection and control, absolute and differential infrared gas analyzers were installed within the gas-exchange system, cuvette temperature is controlled by heat exchangers and temperature of the host walk-in growth room, and sensors monitor temperature and humidity within the cuvette and are displayed and logged. Oral presentations were made at all conferences attended during the report period and a symposium on regenerative life support for space was organized and moderated. "Living in Space" aired on the History Channel December 23, 2008 and was available for download by itunes. The program is also on the DVD "The Universe: Season 3".

Publications

• Massa GD, Kim H-H, Wheeler RM, Mitchell CA (2008) Plant productivity in response to LED lighting. HortScience. 43(7): 1951-1956.

Progress 10/01/07 to 09/30/08

Outputs
OUTPUTS: Experimentation was conducted throughout the reporting period in controlled-environment growth chambers, walk-in growth rooms, and greenhouses in connection with NASA-funded research in biomass/crop production for a future space-based bioregenerative life-support system as well as to complete work for previously funded pharma-crop-production studies of corn in controlled environments. Heat-exchange analysis was conducted for bottom-heated high tunnels during winter and global information systems (GIS). Analysis was performed for potential waste-heat sites in the northern quadrant of Indiana as part of a feasibility study for an Indiana Economic Development Corporation seed grant to create economically viable, year-round local production of high-value specialty crops. The NASA-related outputs were reported at the American Society for Gravitational and Space Biology conference October 25-28, 2007 at the NASA Ames Research Center, Mountain View CA. The waste-energy-leveraged high tunnel model was presented at the Indiana Horticultural Congress, Indianapolis, January 28-30, 2008. Results of all controlled environment work were reported at the International Controlled Environments Conference, Cocoa Beach, FL March 8-11, 2008. On June 10, 2008, The History Channel filmed an interview on the Purdue campus of the NASA work for an upcoming "Living in Space" episode of the History Channel's "The Universe Show". The NASA work on novel LED lighting systems was reported at the Committee on Space Research (COSPAR) conference in Montreal July 14-18, 2008 and at the NASA Lunar Sciences Institute initial meeting at the NASA Ames Research Center, Mountain View CA, on July 20-23, 2008. The waste-energy-leveraged high-tunnel agriculture work was reported at the American Society for Horticultural Science (ASHS) conference in Orlando July 21-23, 2008. Four undergraduate students received laboratory training while assisting in all aspects of the research process. One of the students presented his research as an invited undergraduate speaker at the Purdue Horticulture and Landscape Architecture research retreat on May 9, 2008. A lecture on "Plants in Space" was presented to the Purdue Summer camp program for gifted students on July 8, 2008. Two engineering graduate students were employed for the summer and fall semesters to assemble, program, and implement construction of a crop gas-exchange cuvette system. An interview on "Food in Space" was given for Gourmet Magazine on May 29th, 2008. A visiting seminar speaker hosted April 24-25th was Dr. A.J. Both from Rutgers University. Also hosted March 20, 2008 was Dr. Caula A. Beyl, Dean of the College of Agriculture, University of Tennessee, who was honored as a Purdue Distinguished Agricultural Alumni Awardee. PARTICIPANTS: The PI, Dr. Cary Mitchell, oversees all aspects of controlled environment crop research in the laboratory. Dr. Gioia Massa, a Post-Doctoral Research Associate, conducted experiments to reduce equivalent system mass for a space-based life-support system, including novel LED-based lighting systems and environmental optimization of strawberry and sweetpotato production. Drs. Raymond Wheeler of NASA and Hyeon-Hye Kim collaborated in writing a review article on plant responses to LED lighting. Mr. David Whittinghill is developing a model of plant responses to intracanopy lighting as his Ph.D. dissertation research in computer graphics technology. Mr. Mike Bourget and Dr. Bob Morrow from the Orbital Technologies Corporation collaborated in designing and fabricating the LED "lightsicle" system that has been the cornerstone of Dr. Massa's lighting work to reduce the energy needed for crop lighting in controlled environments and additionally provided hardware for testing of algal production systems. Drs. Ron Turco (Purdue Agronomy) and Megan Heller are collaborators on algal production systems research. Dr. Desmond Mortley from Tuskegee University provided propagules and expert advice for the sweetpotato phase of the project. The Indiana Berry and Plant Company provided strawberry propagules for the cultivar screening work conducted by Dr. Massa. Ms. Judith Santini provided expert statistical consulting and data analysis on strawberry, sweetpotato, and corn projects. Mr. Craig Schluttenhoeffer, an undergraduate Horticultural Science major at Purdue University, conducted greenhouse experiments with maize to reduce plant height without compromising grain yield. Ms. Elaine Chase provided expert technical assistance to Dr. Massa in conducting all phases of the NASA and maize research. Mr. Jerry Shepherd designed and fabricated a crop gas-exchange cuvette for measuring photosynthesis of test-crop stands lighted with intracanopy LED strips. Mr. Keith Spence and Mr. Ben Riggs are mechanical and electrical engineering technology graduate students, respectively, who are integrating the gas-exchange cuvette into an overall computer-controlled gas-exchange measurement system. Mr. Lawrence Theller from Agricultural and Biological Engineering at Purdue did a Global Information Systems analysis of the northwest quadrant of Indiana to determine how many thermal waste sites exist that have potential for development into waste-energy-leveraged high-tunnel sites for production of high-value specialty crops during cold seasons. Mr. Abjahit Sathe, a Mechanical Engineering PhD candiate, provided expert thermal analysis of high tunnel environments to be bottom-heated by waste hot water from the Purdue power plant. Dr. William Anderson from the Georgia Agricultural Experiment Station provided propagules of potential cellulosic biofuel species. Four undergraduate students at Purdue assisted in the laboratory during the reporting period to achieve the goals of the various projects. Training included participation at regional, national, and international conferences for Drs. Mitchell and Massa and auditing a class on Plant Pathology for Ms. Elaine Chase. TARGET AUDIENCES: The LED, strawberry, and sweetpotato work is sponsored by NASA, so the target audience is NASA's Advanced Life-Support Program and the U.S. taxpayers who support the federal government. Because there is direct spinoff application for space regenerative life-support systems to ground-based sustainable agricultural production systems, another target audience is the controlled-environment-agriculture producer, whose best days of economically viable production lie ahead. This has become especially relevant for local production as transportation costs and food security become important societal issues. The target audience for the maize work is the future pharma-crop-production industry, which needs methods to grow transgenic crops economically and productively in isolated, controlled environments. The target audience for the waste-energy-leveraged high-tunnel agriculture project include rural, urban, and sub-urban communities with thermal and/or organic waste sites that could be leveraged for job-producing, revenue-accruing new business enterprises that reduce the need for long-distance transportation of food during cold seasons and improve food quality through local, out-of-season production. The scientific community is a target audience that benefits from the publications, presentations, and findings of this controlled-environment agriculture program in terms of building data and resource bases for Earth and space-based agriculture of the twenty-first century. In addition, the increasing environmental awareness and stewardship of the general public make them the target audience for the sustainability and closed ecological system aspects of the NASA and high tunnel research, as evidenced by interest from various quarters such as the History Channel and Gourmet Magazine. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
Experiments were conducted in controlled environments using monochromatic light-emitting diodes (LEDs) as sole sources of light to grow crops, comparing traditional overhead lighting with novel intracanopy (vertical) placement of lamps. Test stands of cowpea were grown both ways with LEDs at the same power levels consisting of 20% blue and 80% red. Intracanopy-lighted stands outperformed overhead-lighted stands with more biomass produced for less energy consumed. A crop gas-exchange system was constructed, with electrical and mechanical engineering graduate students assembling and programming equipment to monitor crop photosynthesis. Growth chamber and greenhouse yield studies conducted in consultation with a statistician led to selection of the Seascape strawberry cultivar for multiple reasons, including energy savings due to high fruit production at short photoperiods, labor savings for pollination and harvest due to production of fewer large fruit vs. many small fruit, and superior organoleptic characteristics. A 10-h or 12-h photoperiod was most effective producing acceptable fruit for less energy. Seascape is being grown under 3 day/night temperature regimes at 10-h photoperiods to further enhance Seascape productivity without compromising flavor. Sweetpotato studies emphasizing strategies for vine control without compromising storage-root yield led to comparisons of growth media and nutrient applications. Comparisons of peat-based vs. calcined clay media (large or small particle size) indicated that large-particle arselite, trade-name "Turface", did not promote root production, but a high-porosity peat + perlite medium as well as a smaller-particle-sized arselite medium, "Profile", were effective for storage-root productivity. Incorporating slow-release fertilizer plus top-dress supplementation was compared to continuous fertigation with "Miracle Gro" Cal-Mag fertilizer without watering to run-through, and while fertigation produced greater root mass, shoot mass and volume also increased. The incorporated solid fertilizer gave a higher root/shoot ratio, but fewer edible roots. Current studies are determining whether lower fertilizer concentrations in the fertigation treatments will reduce vine growth and shoot biomass without compromising root yield. Controlled volumes of different fertilizer concentrations that avoid drainage are being applied to fertigated plants to further improve root/shoot ratio. Because maize develops excessive plant height in response to favorable growing conditions, a drench application of the plant-growth retardant uniconazole, trade name "Sumagic", was tested to reduce plant height in the greenhouse. A modified random block design was used to evaluate effects of eight Sumagic dosages on plant height vs. grain yield over a 110-day production period. Preliminary data analyses suggest that as Sumagic concentration increases, plant height and grain yield decrease. At low Sumagic concentration, however, grain yield is maintained or increased slightly while height reduction still occurs. Tiller number, tiller ears, and barrenness also correlate positively with higher application rates.

Publications

• Massa, G.D., Kim, H.H., Wheeler, R.M., Mitchell, C.A. 2008. Plant productivity in response to LED lighting. HortScience 43(7): 1951-1956.

Progress 10/01/06 to 09/30/07

Outputs
OUTPUTS: A light-emitting-diode intracanopy lighting system was developed for dense crop stands in controlled environments. Red-blue ratios of LEDs were shifted to prevent abnormal gall-like growths forming on leaves and petioles when using narrow-band radiation. UV-A-emitting lamps supplemented LED radiation in effort to prevent this oedema from forming. A prototype High-Efficiency-Lighting-with-Integrated-Adaptive-Control (HELIAC II) hardware/software system developed by Orbital Technologies, Inc. was tested for potential to detect leaves near specific light engines in a foliar canopy and to selectively energize individual LED light engines along vertical "lightsicles" to save electrical energy during crop-stand growth and development. Sweetpotato vines growing in greenhouses were trained on cylindrical wire cages to contain the otherwise prolific shoot growth and adapt sweetpotato for protected cultivation. Side shoots were pinched off to maintain a single trainable vine per plant, and container size was constrained to stimulate tuberous root development. Several media types were tested to determine an optimal root environment. Day-neutral strawberry cultivars were screened for potential year-round berry production in greenhouses and growth chambers. Runners were pinched off to promote continuous reproductive development, mechanical means were tested to replace seasonal insect pollinators, and several day/night temperature regimes were tested for effects on fruit yield and quality throughout the year. The shortest photoperiod permitting acceptable fruit yield and quality was investigated to minimize lighting costs in controlled-environment production. Dwarf varieties of field corn were screened in a growth chamber for seed yield under lighting from mixed high-intensity discharge lamps. The selected variety was subsequently screened for growth vigor and yield in a standardized growth room lighted by different combinations of high-pressure sodium and/or metal-halide lamps. The same corn selection was grown in a high-bay growth chamber under optimizing environmental conditions and evaluated for growth, synchronization of pollen shedding from tassels with silk receptivity on ears, and seed number and weight with respect to container size. In subsequent experiments, night temperature was maintained for the first 2 hours of light in effort to reduce main stem height and/or increase tiller and secondary ear development. A tall Bt corn variety was grown in the greenhouse and was sprayed or soil drenched with different chemical growth retardants in effort to reduce stem height and force additional ear and seed development on the main stem and/or on secondary ears developing on tillers. Concentration dependence and tiller removal of the optimum growth-regulator treatment were investigated. The outputs and outcomes of this work were disseminated in reports to the NCERA-101 Committee on Controlled-Environment Technology and Use, to the American Society for Horticultural Science, and to the American Society for Gravitational and Space Biology. PARTICIPANTS: Dr. Cary Mitchell was the Principal Investigator and Project Director for the reporting period. Dr. Gioia D. Massa was the Post-Doctoral Research Associate tasked with implementing the goals of the project. The Orbital Technologies Corporation of Madison, Wisconsin was a Collaborating Partner on the project, providing hardware and software for the LED intracanopy lighting portion of the project. Dr. Robert Morrow and Mr. Mike Bourget were the principal points of contact at Orbitec. Dr. Desmond Mortley of Tuskegee University, Alabama collaborated on the sweetpotato portion of the project and provided advice and propagules for the work. Dr. Lisa Mauer of the Purdue Food Science Department collaborated on anti-oxidant analyses of controlled-environment-grown crops. Mr. Craig Schluttenhoefer was an undergraduate student on the project who investigated effects of chemical growth retardants on corn growth and yield. Ms. Mercedes Mick and Mr. Dan McMillan were other hourly wage undergraduates who contributed substantially to the overall goals of the project. Training and outreach related to the project occurred in connection with presentations made at the 2007 Indiana Horticultural Congress, in an undergraduate class on Horticultural Production Technologies,in a seminar to Mid-America Collegiate Horticulture Students (MACHS), and in a Purdue University summer camp on the topic of "Plants in Space". TARGET AUDIENCES: Targeted audiences include planners and designers of space regenerative life-support systems and ground-based controlled-environment agriculture. PROJECT MODIFICATIONS: A component of chemical control of plant height was added to the pharma-crop part of the overall project because corn plants were growing too tall in the high-bay growth chamber prior to tasseling, and temperature dip at the beginning of the daily light period was insufficient to dwarf plants enough to complete the cropping cycle.

Impacts
When the proportion of blue LED emissions was no less than 15% of total Red + Blue photon flux, gall-like intumescence or oedema formation was prevented on cowpea but not on pepper vegetative growth, including meristems. Although UV-A radiation appeared to reduce the incidence of pepper oedema somewhat on plant parts close to the UV source, lamp output was not strong or uniform enough to give definitive results. UV-A or UV-B -emitting LEDs may be needed on light engines to prevent this productivity-limiting disorder of narrow-band irradiation from occurring. In spite of oedema, pepper plants flowered and produced normal fruits under 440-nm + 640-nm LED radiation as a sole source of plant-growth lighting. Fruit tissues did not have oedema growth. Testing the HELIAC II prototype plant-detection / light-engine-switching system with cowpea, sweetpotato, and tomato stands indicated that differences in growth habit and canopy architecture will require different green LED-flashing intensities and patterns and photodiode threshold-detection settings for different species in order to achieve optimum electrical energy and labor savings through automated switching. Double helical coiling of lateral-bud-pinched sweetpotato vines around wire-mesh cylinders produced yields of tuberous roots comparable to those of unpinched, untrained vines sprawling along a greenhouse bench while reducing the growth area by approximately 75%. Constrained root volume promoted tuberous-root development compared to unconstrained root volume. In a comparison of Turface, Profile, and high-porosity Pro-Mix peat-perlite growth media, sweetpotato yielded most consistently high when grown in the fine-grained Profile substrate. Strawberry cultivar Seascape gave the highest, most consistent, and best-quality berry yield of a number of day-neutral and ever-bearing varieties that were screened for year-round strawberry production potential in controlled environments. Wind currents, brush application of pollen, or vibrating wand all gave comparable pollination rates in a greenhouse environment. Relatively cool 18˚ C day / 10˚ C night temperatures produced the best-tasting fruit without substantially reducing yield of several temperature regimes tested in growth chambers. The shortest photoperiod that Seascape can be grown under without sacrificing yield appears to be 12 hours of light per 24-h day. Vegetative growth of corn was higher under high-pressure sodium or metal halide lamps alone, while mixtures of the two lamp types at the same overall light level surprisingly resulted in poor growth and lower ear production. Ear number and seed yield increased by growing individual corn plants in medium (10-in-diam) rather than larger (14") or smaller (7.5")-diameter pots. Temperature dip for the first two hours of the photoperiod increased ear number and seed yield per plant. The growth retardant Sumagic applied as a soil drench greatly reduced main stem length, stimulated tillering, promoted secondary ear formation, and increased overall seed yield in greenhouse-grown corn.

Publications

• Russell J., Lasinski M., Aydogan S., Pekny J., Mitchell C., (2007). Characterizing crop waste loads for solid waste processing. Int'l. Conf. Environ. Systems, 07:290.

Progress 10/01/05 to 09/30/06

Outputs
Light-emitting diode (LED) arrays have been developed to compare intracanopy (IC) vs. overhead (OH) lighting of cowpea crops in controlled environments. Stands under the OH array were less productive than those with IC lighting. Converting kW-h to g DW biomass was 70% more efficient for IC lighting. Red/blue ratio can prevent leaf intumescence in cowpea, with blue radiation being critical. An IC vs. OH fruit-yield comparison is under investigation for 'Triton' pepper. Reproduction occurs normally under both lighting conditions. Viviparous seed germination, common in greenhouses, was minimal in fruits with LED lighting. Although fruit production by the IC crop lagged the OH crop, less than half of the vertical IC light engines are energized while all of the horizontal OH ones are. Design of a crop-stand gas-exchange system for IC lighting is nearly complete and cuvette construction is about to begin. Components for mass-flow control, CO2 detection and analysis, and other environmental control and sensing parameters have been obtained, with gas-exchange-system assembly and control-system programming to follow. Sweetpotato typically has a sprawling growth habit unsuitable for efficient storage-root production in controlled environments. In effort to restrict shoot growth without affecting storage-root productivity, axillary branches are removed and single-leader vines are trained around conical or cylindrical mesh supports. Combined pinching and training dramatically reduces surface area occupied per plant. Crowding two plants per root container maximizes storage-root formation. The shoot tips removed contribute to total edible biomass formed. Sweetpotato vines were suspended from hanging baskets. Downward vine growth was limited, perhaps by negative gravitropism causing upward bending of shoot tips. Although the surface volume occupied by hanging shoots was minimized, storage-root formation also was suppressed. Five strawberry cultivars were grown in different day/night temperature environments. The coolest temperature regime tested (18 C days / 10 C nights) produced the largest number and most organoleptically acceptable berries for all but one cultivar. The same cultivars were subjected to two different pollination methods or to unpollinated control treatments. Pollen either was applied to flowers with a soft brush, flowers were vibrated with a wand, or were subjected to natural air movement and routine maintenance handling in a greenhouse. No significant differences were found among pollination methods. Strawberry cultivars 'Tribute', 'Seascape', and 'Fern' are being grown under cool temperatures and photoperiods of 14, 17, or 20 hours per day. Preliminary results indicate that the longest days stimulate fruit-biomass production in 'Tribute' and 'Seascape', while intermediate, 17-h photoperiods stimulate fruit production in the 'Fern' cultivar. Efforts to define and optimize conditions for pharma-corn production have shown that day/night temperature differential, humidity, and light intensity are all critical factors in synchronizing tasseling and silking, pollination, seed set, and ear fill in controlled environments.

Impacts
This is the century of the life sciences, of biotechnology, and of controlled-environment agriculture (CEA). Genetically improved pharmaceutical, food, and ornamental crops will command high monetary value in the market place. Certain transgenic traits will require containment, isolation, and security for their production in controlled environments (CE) as well as the processing of value-added crop harvest. Year-round production of such high-value crops in any locality, regardless of climate, will eliminate the need for expensive, long-distance transportation costs and be environmentally friendly. Although contained CEA is energy intensive, production costs can be reduced substantially by automation, identifying optimizing conditions for CE crop production, developing energy-saving methods for crop lighting, and leveraging locally available, cheap energy sources. Crop-lighting systems that are low-power-requiring, are relatively cool, long-lived, that emit only the most efficiently absorbed wavelengths, that target all competent leaves within a crop stand, and which automatically sense the position of those leaves throughout crop development will cut CE lighting and associated heat-rejection costs exponentially. LED-based intracanopy and close-canopy lighting systems under development will meet those requirements. Reclaiming electrical energy for crop lighting from locally concentrated waste biomass through application of anaerobic bioreactors and fuel calls will further enhance the profitability of producing high-value CEA crops.

Publications

• Massa, G.D., Mick M.E., and Mitchell, C.A. 2006. Strawberry cultivar analysis: temperature and pollination studies. Intl. Conf. Environ. Systems. 2006-01-2030.
• Russell, J.F., Massa, G.D., and Mitchell, C.A. 2006. Water and energy transport of crops under different lighting conditions. Intl. Conf. Environ. Systems. 2006-01-2028.

Progress 10/01/04 to 09/30/05

Outputs
Lighting Research. Orbital Technologies, Inc. constructed for us a reconfigurable LED lighting array for crop growth. Testing the array in an intracanopy (IC) configuration lead to protocols that resulted in adequate productivity of cowpea crop stands. When configured into an overhead (OH) planar array, plant growth was reduced at equivalent power usage, indicating that IC LED lighting reduced power costs for crop growth. Orbitec received a Phase 1 SBIR from NASA to develop High Efficiency Lighting with Integrated Adaptive Control (HELIAC). We conducted tests with a prototype plant detection apparatus and collected data to optimize detection of plant position for IC and OH lighting configurations. Orbitc was awarded a Phase 2 SBIR for HELIAC to integrate plant detection capability into the lighting array. Orbitec delivered a second array, and we are comparing effects of IC and OH irradiation on crop growth. Studies of space-saving sweetpotato cultivation practices were presented at an international conference. Fruit yield of strawberry cultivars was compared under different temperature regimes. Trade-offs are assessed between fruit yield and time required for assisted pollination. Collaboration with Lisa Mauer (Purdue Food Sci.) compares antioxidant levels in strawberry and carrot cultivars. Collaboration with George Chiu (Purdue Mech. Eng.) is developing automated pH control for hydroponics. Pharma-Crop Research. A high-bay room was used to prove the feasibility of growing Bt corn under HID lamps as a sole source of light. Different combinations of high-pressure sodium (HPS) and metal halide (MH) lamps were compared for their effects on vegetative growth. The combination of 600 W HPS and 400 W MH resulted in the shortest plants. Three dwarf corn lines are being grown under four different light spectra. A growth chamber of 11-foot height clearance was installed at Purdue by EGC. In an optimizing environment, Bt corn grew over 11 feet. An experiment is underway using DIP temperature treatments to reduce corn height. A pilot semi-controlled plant-growth facility was designed and constructed within the Marengo mine complex in southern Indiana to determine the feasibility of growing Bt corn and other crops underground. HID lamps were used both as the light source as well as the heat source in the facility. The naturally cool mine temperature was leveraged to prevent overheating in the growth facility. Environments were identified that lead to normal corn-crop development in an underground growth facility, and adequate seed yield occurs using HID lamps as sole light sources. Based on the experience of designing and running the pilot facility, a second-generation growth chamber was constructed with improved environmental control.

Impacts
The LED lighting system, with addition of automated plant detection and switching capabilities, will provide adaptive crop lighting with little human input. For an advanced life-support system, factors such as crewtime and power usage will determine the optimum technology. The LED array minimizes power by targeting light only to photosynthetic tissue. The LEDs emit wavelengths of peak pigment absorption. IC lighting allows greater yield than OH lighting with less power. A gas-exchange system for the LEDs will allow precise and rapid monitoring of photosynthesis in response to different environmental settings. The pharma-crop experiments not only prove the feasibility of growing corn with HID lights in a controlled environment, but also defined appropriate light intensity, planting media, pot size, and fertigation regimes for Bt corn growth. These paradigms have been adopted in the underground facility. The studies provided guidelines to select HPS/MH lamp combinations for best crop performance, as well as a framework for designing the underground controlled environment facilities. The mine facilities not only validated the feasibility of growing corn (and other crops) in a controlled underground environment, but also provided the Controlled Pharming Ventures company (CPV) with 700 square feet of controlled environment space that can be used either for research or for commercial production.

Publications

• Massa GD, Mick ME, Weiss I, Montgomery JA, Mortley DG, Mauer LJ and C A Mitchell (2005) Effects of root-zone volume, vine pruning, and season on yield, proximate composition, and antioxidant capacity of sweetpotato (Ipomea batatas (Lam.) L. TU-82-155). ICES, Paper #2005-01-2816.
• Massa GD, Emmerich JC, Morrow RC and CA Mitchell (2005) Development of a Reconfigurable LED Plant-growth Lighting System for Equivalent System Mass Reduction in an ALS. ICES, Paper #2005-01-2955.
• Massa GD, Emmerich JC, Mick ME, Kennedy RJ, Morrow RC, Mitchell CA (2005) Development and testing of an efficient LED intracanopy lighting design for minimizing equivalent system mass in an advanced life-support system. Gravit. Space. Biol. Bull. 18(2): 87-88

Progress 10/01/03 to 09/29/04

Outputs
Hydroponic crop stands growing in controlled environments with "intracanopy" placement of low-power fluorescent lamps allows the stands to be half as productive as those grown with traditional high-intensity overhead lighting, but using only 10% as much electrical energy. The lamps occupy too much space to increase lamp number more. We have subsequently designed an intracanopy lighting array consisting of thin strips containing light-emitting diodes (LEDs). The crop stand grows up among the hanging strips. Each strip contains 20 one-inch-square"light engines" arranged sequentially along the strip. Each engine contains seven parallel rows of printed-circuit LEDs that emit narrow-band, monochromatic light. The strips have been designed so that individual engines can be switched on sequentially from the bottom up, thereby allowing interior, lateral lighting to keep pace with the top of the growing crop and avoids the lighting of empty head space not populated with photosynthetic tissues. These first-generation "lightcicle" arrays are equipped with red and blue LEDs that can be switched on and off, and each color LED can be regulated separately in intensity to achieve any shade of purple desired to control different aspects of plant growth. Cowpea (Vigna unguiculata) stands are being grown among the glowing strips and are being evaluated for productivity and electrical power consumption. It is expected that the combination of sequential switching, low power and resulting coolness of the lighting system, specific wavelength emissions, and proximity of emitters to plant tissues will result in substantially reduced expenditure of energy to provide adequate plant-growth lighting in controlled environments. In a separate effort, we have teamed with an entrepreneur who wishes to isolate production of genetically engineered crops underground in former mines to mass-produce gene-expression products that can be purified into pharmaceutical drugs or consumed directly by eating harvested plant parts. A facility is needed to grow crops such as transgenic corn under all-electrical lighting in the mine environment, as well as to cope with the natural coolness of the underground environment, and to prevent foreign pollen from entering and transgenic pollen from escaping the contained, controlled-environment facility. We are growing corn from seed to seed under high-intensity discharge (HID) lamps as the only source of photosynthetic light and are optimizing conditions for future underground production of corn. We have ordered a high-bay growth chamber that will allow field corn to grow to harvest maturity under controlled-environment conditions optimized for future application at the mine location. The crop-growth facility to be constructed at the mine will have characteristics that are hybrid between those of a greenhouse and a growth chamber. Instead of requiring a heat-rejection system to remove excess heat from the HID lamps, the waste heat will be harnessed for warming the cool mine air as it is introduced into the facility to bring in fresh carbon dioxide for the contained crops. The mine crop-growth facility is unique and is presently under development.

Impacts
The impact is that a revolutionary new kind of electrical plant-growth-lighting system is being developed that operates at low electrical power, is cool to the touch, and has extremely long-lived solid-state emitters, averaging from 100,000 to 500,000 hours of operating lifetime, and emits wavelengths that match the absorption maxima of major photosynthetic pigments. Furthermore, the lighting arrays can be distributed within and among the foliar canopy of a crop stand and deliver light effectively to all leaves, even after the canopy "closes" with respect to overhead lighting. The lighting system will save considerable operational cost in lighting plants in controlled environments. Mine interiors are dark, cold, and, if limestone, tend to have elevated carbon dioxide in the mine atmosphere. The cost of mass-producing pharmaceutical drugs by low-throughput mammalian cell cultures in a laboratory is costly enough to justify electrical lighting of crops in the mine. High-intensity discharge lamps give off copious amounts of waste heat in addition to light. We are leveraging the waste heat from HID lamps as a resource for heating transgenic crops within a growth facility in the mine.Fresh mine air is mixed with recirculated waste-heat air to maintain warm tempertures around corn crops while bringing fresh carbon dioxide into the growth area. The high CO2 content in the mine also is an asset in terms of plant growth. Growing Pharma-crops this way will alleviate public concerns regarding escape of GMO germplasm.

Publications

• Montgomery, J.A., R.A. Bressan, and C.A. Mitchell. 2003. Application of mechano-dwarfing stimuli to Arabidopsis for mutant-screening development. Acta Horticulturae 618:85-93.
• Montgomery, J.A., R.A. Bressan, and C.A.Mitchell. 2004. Optimizing environmental conditions for mass application of mechano-dwarfing stimuli to Arabidopsis. J.Amer. Soc. Hort. Sci.129(3):339-343.

Progress 10/01/02 to 09/30/03

Outputs
A novel crop-lighting system is being developed for controlled-environment agriculture (CEA). The high cost of lighting crops with artificial lamps as a sole light source has prevented CEA from being profitable. The problem is that foliar canopies of many crops "close" with respect to overhead light penetration, leading to mutual shading of lower leaves. Thus, it becomes necessary to operate lamps at high intensity to maximize crop-stand productivity. The associated heat load requires substantial spatial separation of lamps and crop surfaces, with a transparent heat-shield barrier imposed between them. Substantial energy must be expended for heat rejection from the system. The separation also causes an exponential decrease in incident radiation at the crop surface with linear distance between lamps and crop. Low-power "intra-canopy" (IC) and "close-canopy" (CC) light-distribution systems close to or touching plants without causing thermal tissue damage will overcome these problems. The IC light-distribution system consists of thin, vertical strips of composite material densely populated with parallel rows of tiny, colored, light-emitting diodes (LEDs). Crop plants grow among these hanging "lightcicles", which switch on in discrete, small sections from the bottom up, keeping pace with increases in canopy height. Switching is to be automated so that light energy is not wasted on empty headspace. LED colors will be selected to match absorption spectra of major plant pigmants. Color intensity from LEDs within discrete rows will be controlled separately, but the close spacing of rows permits effective spectral blending so that hue control as well as overall photon flux from the LED strips is effectively controlled by regulating electrical current to each color of LED. For low-profile and open-canopy crops, horizontal plates populated densely with small LEDs will be positioned close above crop stands. These "bulls-eye glowplates" will switch on in concentric circles or in irregular patterns above seedlings in a stand, again irradiating only support space covered by horizontally expanding plant tissue. The sensing and switch-control software will be more complex for the glowplates than for the lightcicles, but the spacing, switching, hue, and intensity control parameters will be completely analogous for both light-distribution systems. Design parameters have been defined and preliminary measurements of photon flux and temperature as a function of applied current and distance have been completed for printed-circuit LED arrays. Spectroradiometric scans of light output at different current intensities have been performed to test for spectral shifts at different power levels.

Impacts
Development of intracanopy and close-canopy light-distribution systems will save considerable power and energy for crop production in controlled environments. It will permit year-round crop production in warehouse environments in northern climates, especially if coupled with cheap, bio-derived energy sources. The combination will make commercial controlled-environment production of salad greens and culinary herbs competitive with field-grown imports in the winter and will ensure high-quality produce year-round.

Publications

• ORCUN, S., G. BLAU, J. PEKNY, and C. MITCHELL. 2003. An advanced scheduling model for crop production in bio-regenerative advanced life-support systems. ICES 2003-01-2358.

Progress 10/01/01 to 09/30/02

Outputs
A visual growth screen of Arabidopsis thaliana (L.) Heynh. C-24 seedlings was developed to identify mechano-resistant T-DNA insertional mutants from masses of normally mechano-sensitive seedlings. Key to developing a reliable, uniform mutant screen involved growing seedlings under low photosynthetic photon flux (PPF) in the range of 50 to 60 umol/m-2/s-1, which stimulated hypocotyl elongation of controls but retained high mechano-sensitivity. Ten reciprocal brush strokes applied twice daily with burlap cloth across a rockwool substrate containing 400 seedlings reduced hypocotyl elongation 39% relative to undisturbed controls after 6 days if fluorescent lighting was used, but only 34% if fluorescent + incandescent lighting was used at the same PPF. Incandescent radiation caused seedlings to elongate excessively and to be more prone to lodging from brush treatments. Transparent plastic domes placed over seedling flats were required for high mechano-sensitivity. Mechano-responsivity of hypocotyl elongation and leaf expansion were inversely proportional to average daily temperature (ADT) in the range of 21 C to 28 C. An ADT of 23 C is a good compromise between high mechano-sensitivity and rapid growth of control seedlings, both of which are important for adequate growth separation of treated and untreated seedlings within several days. Although low PPF was critical for high mechano-sensitivity, photoperiod ranging from 12 to 24 hours per day at low PPF had no effect on mechano-responsivity. The combined effective environmental parameters are being used to implement the Arabidopsis mechano-mutant screen. In a project to discover genes controlling the mechano-sensitivity of dark-grown soybean (Glycine max (L.) Merr.) seedlings, it was necessary to modify an existing seedling growth system to eliminate uncontrolled environmental conditions that had been causing spurious touch-sensitive gene expression, without touch per se. Following modification of the growth system, a soy EST highly similar to TCH3 of Arabidopsis was found to be strongly up-regulated 1 hour following mechano-stimulation and completely turned over by 3 hours. Total RNA was extracted from hypocotyl elongation zones (HEZs) of stressed and unstressed soybean seedlings and used to synthesize double-stranded cDNA. The cDNA was used as a template for PCR amplification using primers specific to fragments of differentially expressed genes. Products were separated on polyacrylamide gels. Gel banding patterns indicated many differentially amplified gene fragments, some suggesting up-regulation and others down-regulation of touch-sensitive gene expression. Candidate fragments were re-amplified, labeled, and used as probes for Northern-blot confirmation of expression. In two preliminary Northern-blot analyses, one AFLP fragment appeared to be up-regulated, and another down-regulated following mechano-stimulation.

Impacts
Identification of genes that control mechano-stress-induced inhibition of plant growth will permit their cloning and sequencing, their subsequent targeted knockout, and creation of crop plants with enhanced resistance to wind, precipitation, and other physical stresses.

Publications

• No publications reported this period

Progress 10/01/00 to 09/30/01

Outputs
An objective is to discover and characterize genes controlling mechanical-stress inhibition of plant growth and productivity. The model system in use is the dark-grown soybean (Glycine max (L.) Merr. cv. Century 84) seedling, which elongates exclusively by cell enlargement confined to a narrow region of cells located just below the cotyledonary hook called the hypocotyl elongation zone (HEZ). A brief episode of thigmic (contact rubbing) stress applied to the hook and HEZ retarded growth 30% 12 hours after treatment. Sequences of known arabidopsis touch genes (TCH 2,3,4) were searched against a soy database hosted by The Institute for Genomic Research (TIGR). Several soy genes exhibited TCH homology, but thus far only AI900648 (GenBank Accession Number), which putatively encodes calmodulin, has been found to be differentially expressed in HEZs of touched soybean. Control seedlings express a low background level of AI900648 mRNA. However, expression of this TCH-like gene increases to a significant level 30 minutes after touch, reaching a peak of activity after 2 hours, and then decays back to the control level 4 hours after stress. The seedling growth system has been modified to minimize background expression of AI900648. Commercial growth mix covering planted seeds in flats has been replaced with a thin layer of light-weight, coarse-grade vermiculite so that shoots encounter minimal resistance during subterranean growth. Emerged seedlings are protected from uncontrolled air movement by a cheesecloth windscreen, which diminishes background expression of AI900648 mRNA relative to that of unprotected control seedlings. A growth screen of Arabidopsis thaliana (L.) Heynh. C-24 ecotype seedlings also is under development to pick out T-DNA insertional mechano-resistant mutants from masses of vegetative mechano-sensitive seedlings. Environmental control has been found essential to ensure the consistency and directionality of seedling responses to mass mechanical-stress applications, thereby essentially eliminating greenhouses from consideration for performing large-scale mutant screens. Brushing or rolling treatments were found to damage young seedling rosettes, whereas perforated transparent plates on top of seedling flats actually stimulated lateral rosette expansion. The need to sub-irrigate flats of mechanically stressed seedlings caused salt-accumulation and nutritional problems with commercial growth mixes. Photosynthetic photon flux (PPF) levels of 125-150 micromoles/m2/s from HID lamps in a growth room desensitized seedlings to all forms of mechanical stresses. Ambient, uncontrolled greenhouse PPF also rendered plants relatively insensitive. Low-irradiance PPF of 50 micromoles/m2/s from a bank of fluorescent + incandescent lamps promoted upright shoot growth of seedlings as well as sensitivity to frictional and static impedance stresses. Replacing commercial growth mixes with rock wool and using a modified Hoagland's no.1 nutrient solution further standardized conditions for developing a reliable, repeatable mutant screen based upon visual observation of vegetative seedling growth differences.

Impacts
Identification of genes that control dwarfing and loss of productivity in plants in response to mechanical stimuli will permit their isolation and sequencing, targeted knockout of those genes, and generation of model and crop plants with enhanced resistance to wind, precipitation, and other mechanical stresses.

Publications

• Frantz, J.M., Joly, R.J., and Mitchell, C.A. 2001. Intracanopy lighting reduces electrical energy utilization by closed cowpea stands. Life Support & Biosphere Sciences 7:283-290.

Progress 10/01/99 to 09/30/00

Outputs
Wind and precipitation are important forms of mechanical stress in nature that significantly limit growth, development, and yield of field crops and landscape plants. Identification of genes that determine sensitivity of plants to wind stress and modification of their expression will be an important step in genetically engineering stress-resistant crops with improved yield potential. Current work emphasizes development of methods and technologies for identifying genes associated with mechanical dwarfing of plants. A major response to touch or shaking is smaller plant size. Since cell enlargement is necessary for growth in size, we developed a system for isolating genetic material from plant tissue growing exclusively by cell enlargement. The hypocotyl elongation zone (HEZ) of 4-day-old, dark-grown soybean (Glycine max Merr.) seedlings was found to contain cells whose enlargement is slowed or stopped by brief thigmic (rubbing) stress applied to the seedling hook just above the HEZ. This system is a model for the forces encountered by subterranean seedlings before emergence from soil. We developed methods for cultivation and stress application of multiple soybean seedlings in darkness. A capillary hydroponics system wicking aqueous Ca(NO3)2 into coarse vermiculite provided a low-stress seed bed for short-term seedling growth. Mechanical stress as a static counterforce against seedling stands was compared with frictional rubbing across the tops of seedlings en masse. Briefly rubbing the tops of seedlings retarded hypocotyl elongation 30-45% compared to untouched controls. HEZ sections (1.5 cm) were cut from hypocotyls of stressed and control seedlings under green safelight at 30 minutes, 2 hours, or 24 hours after stress application and were immediately frozen in liquid N2. Frozen tissue samples (5 g) were ground and extracted for total genomic mRNA in the molecular biology laboratory of K.G. Raghothama. Reverse transcriptase was used to create cDNA from each mRNA. cDNAs were mixed from control and stress tissues, and total cDNA was transferred into bacterial cells via plasmid vectors. The resulting cDNA library was amplified by growing the transformed bacteria through multiple cell-division cycles. This library is stored at -70 C pending probing with mRNAs, cDNAs, or DNAs from test samples in effort to obtain hybridization with known sequences.

Impacts
A near-term goal is to identify putative "touch genes" in soybean HEZs homologous or different from those already known to occur in Arabidopsis. A longer-term goal is to create "knockouts" of touch genes that in turn create crop or landscape plants that are less prone to wind damage and low productivity in the field or landscape.

Publications

• Frantz, J., Joly, R., and Mitchell, C. 2000. Intracanopy lighting influences radiation capture, productivity, and leaf senescence in cowpea canopies. J. Amer. Soc. Hort. Sci. 125 (6): November issue.
• Frantz, J., Joly, R., and Mitchell, C. 2000. Improving productivity of closed cowpea stands with intracanopy lighting. J. Life Support & Biosphere Sci. Fall issue.

Progress 10/01/97 to 09/30/98

Outputs
Controlled-environment research in Dr. Mitchell's laboratory during 1998 addressed energy-utilization efficiency for crop production. Specifically, the work emphasized optimization of intracanopy (IC) lighting for closed canopies of cowpea (Vigna unguiculata Walp `IT87D-941-1') growing hydroponically within separate light-tight compartments within growth chambers relative to traditional overhead (OH) lighting. Since cowpea produces edible foliage as well as snap and dry beans, vegetative or mixed reproductive/vegetative harvest scenarios were practiced. Although total yield and edible yield rates were significantly higher for IC-grown canopies on 18-h vs. 12-h photoperiods, they were not higher for canopies grown on 24-h vs.18-h photoperiods, so the efficiency of converting electrical lighting energy into edible biomass was highest for 18-h photoperiods. Because IC lighting distributes light uniformly throughout closed canopies whereas OH lighting does not, inner leaves remain photosynthetically competent far longer than for OH lighting. In fact, interior leaves remained active and non-senescent for more than 3 weeks longer than did equivalent leaves of OH-lighted canopies. Thus, total vegetative yield, harvest index, edible yield rate, yield efficiency rate, and edible biomass per kW-h all were significantly higher for IC vs. OH canopies. These trends also were true for IC and OH canopies grown at 1000 ppm CO2 rather than at 400 ppm CO2, except that the absolute values of the above productivity parameters were shifted upward at the higher CO2 level. Carbon dioxide enrichment stimulated the yield parameters of IC canopies moreso than for OH-lighted canopies because IC leaves were photosynthetically active longer. IC-lighted canopies also had a leaf area index of more than 8 after 50 days of treatment, whereas the LAI of OH canopies was less than 5. Closed OH canopies suffered premature leaf senescence and abscission, whereas IC leaves reoriented to present their adaxial side toward the nearest source of light and remained active for as prolonged time. For OH-ighted leaves, the radiation environment in the understory of the stand rapidly became depleted in red, orange, blue, and violet wavebands with advancing canopy age, whereas ambient levels of these wavebands remained relatively constant within IC-lighted canopies. Relative levels of green and yellow light increased within OH canopies by default. Intracanopy lighting of closed canopies of crops with low-intensity lamps appears to be promising for future lighting technologies in controlled-environment agriculture.

Impacts
(N/A)

Publications

• FRANTZ, J., CHUN, C., JOLY, R., and MITCHELL, C. 1998. Intracanopy lighting of cowpea canopies in controlled environments. J. Life Support & Biosphere Sci. 5: 183-189.
• FRICK, J., PRECETTI, C., and MITCHELL, C. 1998. Predicting lettuce canopy photosynthesis with statistical and neural network models. J. Amer. Soc. Hort. Sci. 123: November Issue.
• MYERS, P., and MITCHELL, C. 1998. Optimizing the calcium content of a copolymer acrylamide gel matrix for dark-grown seedlings. J. Amer. Soc. Hort. Sci. 123: November Issue.

Progress 10/01/96 to 09/30/97

Outputs
Controlled environment research in the lab in 1997 emphasized energy utilization efficiency for hydroponic crop production in growth chambers. In one approach, canopies of leaf lettuce (Lactuca sativa L.) were grown in transparent assimilation chambers under either static conditions of high photosynthetic flux (PPF) plus CO2 enrichment during exponential growth, or PPF and CO2 were varied dynamically according to changing crop preference and tolerance as it developed, based upon feedback from real-time photosynthetic rates (Pn). Process-control software directed automatic changes in CO2 injection and PPF according to rule sets and Pn response data established from previous experiments. By comparing increments of output (Pn) with increments of input (kW-h), the size and direction of input increments were adjusted to optimize energy-use efficiency for Pn. Equivalent yield rates and Pn were obtained for dynamic and static controls, but dynamic control used only 73% as much electrical energy for plant-growth lamps. Daily energy-conversion efficiency (g edible biomass/kW-h) for the dynamic control strategy was 132% of the static controls. In another approach, limitations of canopy closure for planophile (horizontal-leafed) crops lighted overhead were addressed by using short, low-power fluorescent lamps within the canopy that were arrayed remotely from their ballasts and switches and sleeved with a transparent mylar heat shield. Canopies of cowpea (Vigna unguiculata Walp.) were grown hydroponically within separate light-tight compartments and compared for productivity and yield using different geometries of lamp arrangement, different reflective films lining compartments, and different crop-stand densities. Cowpea canopies were allowed to grow up and around lamps, providing irradiation from many different angles within the canopy. The light-scattering properties of white polyethylene film were found to be superior to the reflective properties of mirrored mylar film as a compartment liner to prevent ambient light from escaping photosynthetic surfaces. Horizontal tiers of lamps within compartments also were superior to vertical columns in terms of resulting crop productivity. Interior leaves reoriented to present adaxial surfaces toward the nearest lamp in an array, and flower bud abortion and premature leaf senescence did not occur, unlike with overhead-lighted controls. Increasing plant density within a stand between 24 and 97 plants/m2 enhanced absolute yield as well as edible yield rate and improved production efficiency with respect to non-edible biomass penalty. Total yield efficiency with respect to temporal, spatial, energetic, and non-edible biomass penalties were not different between 48 and 97 plants/m2. Computer-generated light maps were used to predict best orientation and distribution of lamp arrays within each compartment. Thus far, cowpea canopy productivity rates have been improved 130-fold using low-power intracanopy lighting instead of high-power overhead lighting, and 45% of the yield obtained from overhead lighting has been achieved with intracanopy lighting using only 10% of the energy used with traditional overhead lighting.

Impacts
(N/A)

Publications

• CHUN, C. and MITCHELL, C. 1997. Dynamic optimization of CELSS crop photosynthetic rate by computer-assisted feedback control. Adv. Space Res. (In press).
• MITCHELL, C., CHUN, C., BRANDT, W., and NIELSEN, S. 1997. Environmental modification of yield and proximate composition of Waldmann's Green leaf lettuce. J. Food Quality 20:73-80.
• NICKEL, K., NIELSEN,S., SMART,D., MITCHELL,C., and BELURY, M. 1997. Calcium bioavailability of vegetarian diets in rats: potential application in a bioregenerative life-support system. J. Food Sci. 62: 619-631.

Progress 10/01/95 to 09/30/96

Outputs
Photosynthesis (Pn) by leaf lettuce (Lactuca sativa L.) canopies was used to test feedback control of environmental inputs to crop stands. Increments of environmental inputs (PPF, CO2, temperature) were compared with increments of Pn and adjusted to maintain favorable output/input ratios throughout crop development. At harvest, edible yield rates for dynamic control of PPF and CO2 were comparable with rates obtained by static control of high CO2 and/or high PPF, but electrical energy consumption was 26% less for dynamic control, while conversion efficiency of energy to edible biomass was 32% greater. In a different approach, cowpea (Vigna unguiculata Walp.) stands were used to test the comparative yield efficiency of low intensity intracanopy lighting with that of traditional high intensity overhead lighting. Low-power fluorescent lamps were arrayed horizontally or vertically in tiers within cowpea canopies. The harvest index of intracanopy-lighted plants was twice that of overhead-lighted plants, while electrical energy use averaged half that for overhead lighting. Photosynthesis saturation curves within the canopies indicated that leaves developing within intracanopy-lighted canopies adapted for efficient light use, but had a capacity to photosynthesize at 2-6 times their measured rate.

Impacts
(N/A)

Publications

• MITCHELL, C., SHERMAN, L., NIELSEN, S., NELSON, P., TRUMBO, P., HODGES, T., HASEGAWA, P., BRESSAN, R., LADISCH, M. and AUSLANDER, D. 1996. Earth benefits ofinterdisciplinary CELSS-related research by the NSCORT in bioregenerative life supp MCKEEHEN, J., MITCHELL, C.
• WHEELER, R., BUGBEE, B. and NIELSEN, S. 1996. Excess nutrients in hydroponic solutions alter nutrient content of rice, wheat, and potato. Adv. Space Res. 18(4/5):73-83.
• MITCHELL, C., DOUGHER, T., NIELSEN, S., BELURY, M. and WHEELER, R. 1996. Costs of providing edible biomass for a balanced vegetarian diet in a controlled ecological life-support system. In: H. Suge, Ed., Plants in Space Biology, pages245-2.

Progress 10/01/94 to 09/30/95

Outputs
The semi-dwarf rice (Oryza sativa L.) cultivar 'Ai-Nan-Tsao' was grown for 78 days in a greenhouse at canopy densities ranging from 70 to over 1000 plants#m-2 at photoperiods of either 8, 10, or 12 hours#day-1. Tiller and panicle number#plant-1 declined with increasing planting density, while amount of inedible shoot biomass increased for all photoperiods tested. Edible yield was highest (at 1750 g grain#m-2) for 12-h photoperiods and 300 to 500 plants#m-2, whereas edible yield rate was highest (at 32 g#m2#day-1) for 10-h photoperiods and the same densities. Yield-efficiency rate was 0.3 to 0.4 g grain#m-3#day-1#g inedible biomass for all 3 photoperiods up to 500 plants#m-2, above which it declined. A planting density of 283 plants#m-2 and a photoperiod of 10 h produced the most favorable rice yield parameters. 'Waldmann's Green' leaf lettuce (Lactuca sativa L.) canopies were grown hydroponically under controlled-environment conditions including constant 25#C, 1100 mmol#mol-1 CO2, and variable photosynthetic photon flux (PPF). PPF was set daily at 80% of the level that gave maximum photosynthetic rate (Pn) the previous day, and adjusted to find the new maximum Pn each day. This variable control of PPF gave 0.226 g DW edible biomass#mol-1 PAR relative to 0.187 g#mol-1 for static control at constant PPF of 895 mmol#m2#sec-1. Dynamic optimization of Pn by feedback control of PPF is being automated using process-control software.

Impacts
(N/A)

Publications

Progress 10/01/93 to 09/30/94

Outputs
Mechanical Stress Project: Dark-grown soybean (Glycine max Merr.) seedlings briefly rubbed at the top and along the sides of the hypocotyl hook experienced a rapid (seconds) collapse of growth to about 20% of the pre-stress rate. Recovery of growth was slow (hours), the actual time dependent upon the total amount of mechanical stress received. Pressure microprobe measurements indicated a partial loss of turgor from sub-epidermal and cortical cells in the upper, growing region of hypocotyls during the first hour after a stress episode. The role of changes in wall extensibility and yield threshold during collapse and recovery of growth are under investigation. Controlled Environment Project: Cowpea (Vigna unguiculata (L.) Walp.) canopies were grown through a mixed (leaf plus seed) harvest scenario using hydroponic culture in a growth chamber with and without carbon dioxide enrichment. Carbon dioxide at 1200 ppm stimulated both the onset of flowering as well as senescence relative to CO(subscript 2) at 400 ppm. CO(subscript 2) enrichment also enhanced both absolute yield and harvest index for cowpeas grown in controlled environments. Rice (Oryza sativa L.) canopies were started in the greenhouse under constant light to stimulate early seedling growth, canopy closure, and early tillering. Canopies were then shifted to shorter photoperiods at different times of the cropping cycle to discourage further tillering but permit flowering and grain fill of cv. 'Ai-Nan-Tsao', which is day neutral for floral initiation.

Impacts
(N/A)

Publications

Progress 10/01/92 to 09/30/93

Outputs
Sixteen pest-resistant cowpea (Vigna unguiculata) cultivars were screened in thegreenhouse for productivity potential to provide legume protein for vegetarian diets in Controlled Ecological Life-Support systems (CELSS) to be deployed in space. For IT84S-2246, increasing photoperiod from 8 to 24 h decreased shoot harvest index (HI) from 50 to 30% for seed and mixed (i.e., seed + foliage) harvest, but kept vegetative HI constant at 60%. In contrast, HI for cv. IT82D-889 was unaffected by photoperiod for all harvest scenarios, giving greatest flexibility for air revitalization and edible biomass production in a CELSS. However, the most energy-efficient compromise between HI and yield rate involves mixed harvest of S-2246 under 8-h photoperiods. Rattooning (cutting back) cowpea shoots to regrow a vegetative crop on the same root system led to twice the edible yield rate (g.m(superscript -2).day(superscript -1)) of regrowth over replants, but a shoot HI of only 40% compared to 60% for replants. Although the tradeoff makes rattooning similar to conventional cropping, it would save labor and would close the canopy faster in a CELSS, where quantum efficiency will be important. More than 50 of the world's most productive cultivars of rice (Oryza sativa) also were screened for potential to provide cereal protein and calories in the diet. A yield-efficiency index (g.m(superscript -3).

Impacts
(N/A)

Publications

Progress 10/01/91 to 09/30/92

Outputs
A brief mechanical stimulus applied to the hook of dark-grown soybean (Glycine max) seedlings caused an abrupt (seconds) 75 to 85% decline in elongation rate followed by a slower (hours) recovery, but variable effects on cumulative growth over 24 hours. Variable growth response occurred regardless of sorting seeds for size or mass. When seedlings were selected on the basis of germination rate, elongation of those with radicle emergence occurring within 24 h after imbibing was inhibited 33% relative to undisturbed controls, while those emerging at 48 and 72 h were inhibited 22% and 14%, respectively, 24 h after a single episode of thigmic (contact rubbing) stress. Extent of soybean seedling growth was dependent on nutritional calcium level, with an initial level of 1 mM Ca+2 in SuperSorb gel medium being deficient for normal seedling growth, whereas 5 mM Ca+2 was sufficient. With sufficient Ca+2, recovery growth rate following initial stress-induced growth reduction was enhanced by increasing K+ in the growth medium, with 10 mM K+ enhancing recovery 60% relative to controls over 24 hours. Sections cut from the hypocotyl elongation zone 6 h after mechanical stress treatment had 29% lower osmotic potential of freeze-thawed cell sap than did controls, indicating osmotic adjustment in elongating cells of stressed plants 24 h after treatment. Growth of hypocotyl sections from undisturbed seedlings ceased at -0.8 MPa osmoticum, whereas that of thigmo-stressed plants continued until -0.9 MPa, indicatin.

Impacts
(N/A)

Publications

Progress 10/01/90 to 09/30/91

Outputs
A cereal, a legume, and an oilseed crop were selected as model systems to provide complex carbohydrate, complete protein, and polyunsaturated oil for a vegetarian diet in future Controlled Ecological Life-Support Systems to be deployed in space. Canopies of semi-dwarf cultivars of rice (Oryza sativa) were screened for yield in a greenhouse under 9-hour photoperiods. `M-103' yields 10.1 g of grain per plant in 112 days with a shoot harvest index of 28%, and will be further tested under more controlled environments. Cowpea (Vigna unguiculata) cultivars were screened in the greenhouse and in hydroponic culture in growth chambers for vegetative and/or reproductive harvest. For IT84E-124, vegetative or mixed-harvest scenarios yielded as much as reproductive growth, if leaves were harvested after full expansion rather than before. CO(subscript 2) enrichment to 1000 ppm enhanced yield 15%. Dwarf, rapid-cycling brassica (Brassica napus) has been grown by passive wicking hydroponics in growth chambers using a solid substrate. Nitrogen at 2 mM in solution permitted high planting densities (e.g., 1163 plants m(superscript -2)) without development of excessive vegetative biomass. Raising N to 15 mM or higher just before flowering (17 days after seeding) enhanced seed yield relative to raising N at a later time. Oil content of seeds inversely with N concentration (42% at 2 mM N to 32% at 15 mM). However, seed yield was highest (4.

Impacts
(N/A)

Publications

Progress 10/01/89 to 09/30/90

Outputs
Dark-grown soybean (Glycine max (L.) Merr.) seedlings experienced a 40-50% reduction in hypocotyl elongation 24 h after a brief thigmic (rubbing) treatment applied to the hook. An immediate 88% inhibition of growth rate resulted from thigmic stress, followed by 20% recovery of the pre-stress growth rate over the next 7 hours. Stress ethylene production was limited to the hook region where stress was applied. Silver thiosulfate, an ethylene action inhibitor, negated the stress response by 38%. Gibberellin was ineffective in negating the stress response. A breeding line of dwarf rapid-cycling brassica (Brassica napus) from Dr. Paul Williams of the University of Wisconsin was evaluated for potential as an oilseed crop for vegetarian diets in bioregenerative life-support systems to be deployed in space. Increasing plant density decreased silique number per plant and seed number per silique. A planting density of 581 plants m gave a yield rate of 5 g m day and a shoot harvest index of 24% at low light and ambient CO(2). Enrichment of CO(2) to 900 ppm delayed leaf senescence and seed fill at all planting densities tested. Several breeding lines of cowpea (Vigna unguiculata) supplied by Dr. B. B. Singh of the International Institute of Tropical Agriculture in Nigeria also were evaluated as a source of legume protein and complex carbohydrate for diets in bioregenerative life-support systems. Reproductive, vegetative, and mixed-harvest scenarios were tested.

Impacts
(N/A)

Publications

Progress 10/01/88 to 09/30/89

Outputs
Experiments were conducted to determine whether decreased cell wall extensibility is responsible for the slower growth and smaller size of mechanically stressed plants. Thigmic (rubbing) stress was applied to the hooks of dark-grown soybean (Glycine max (L.) Merr. cv. Century 84) seedlings as 20 gentle, upward strokes. Hypocotyl elongation was inhibited 50% 24 h after a single episode of stress. Cell length in the growth zone also was reduced 50% by mechanical stress. Wall extensibility of cells in the growth zone actually increased up to 137% of control 20 h after treatment. The increase was due entirely to the elastic component of extensibility. Pronase treatment increased extensibility of stressed tissues an additional 12% but that of controls 40%, indicating that protein is less involved in cross-linking cell walls of stressed plants. Cowpea (Vigna unguiculata (L.) Walp. IT 84S-2246 plants were grown hydroponically for 107 days under 8-h photoperiods at 700 mu mol ms of PAR using either a strictly vegetative or reproductive harvest strategy, or 2 different mixed-harvest scenarios. The highest yields were obtained from either the strictly vegetative scenario, where fully-expanded leaves were stripped at 1-week intervals, or from the mixed strategy, where seeds were harvested at the end but leaves stripped at 2-week intervals. Seed yield was not different between this mixed harvest strategy and the strictly reproductive one.

Impacts
(N/A)

Publications

Progress 10/01/87 to 09/30/88

Outputs
Leaf lettuce (Lactuca sativa L. cv. Waldmann's Green) was grown hydroponically in a controlled environment in single-strength Hoagland's solution in single or double-strength nitrogen as either NO(superscript -)(subscript 3) alone or as NH(superscript +)(subscript 4) + NO(superscript -)(subscript 3) in a 1:5 molar ratio. These treatments were grown either at low or high PPF as fluorescent + incandescent radiation and at ambient or 1500 (mu)1 1(superscript -1) CO(subscript 2). NH(superscript +)(subscript 4) and CO(subscript 2) enrichment increased leaf number and dry weight separately and synergistically, especially at high PPF. Nitrogen as NH(superscript +)(subscript 4) increased protein content of leaves from the 22% of leaf dry weight typical of the field to 36% under high or low PPF, but cut starch content in half. Free sugar content was 2-4 fold greater than that of starch. Food composition as well as growth can be manipulated by major environmental factors that affect photosynthesis and nitrogen assimilation. The growth response of dark-grown pea (Pisum sativum L. cv. Alaska) to mechanical stress was monitored with a position-sensing transducer. The response to brief thigmic (stem rubbing) treatment was an immediate growth inhibition. Although recovery of growth rate began 4-6 minutes after cessation of stress, it was only 70% of control 28 min after treatment, and cumulative growth was only 47% of control 24 hours later.

Impacts
(N/A)

Publications

Progress 01/01/87 to 12/30/87

Outputs
The dark-grown soybean (Glycine max (L.) Merr.) seedling has been used as a sensitive model system to study the physiological basis for inhibition of plant cell enlargement by mechanical stresses (MS). Up to 50% inhibition of hypocotyl elongation occurred 24 h after application of a single episode of thigmic stress (20 upward strokes applied to the hypocotyl hook between the thumb and forefinger). Exogenous calcium salts mimicked MS-induced dwarfing in the concentration range from 1 to 10 mM when applied as ten 1-mu l drops to the hypocotyl hook, provided that the calcium was applied in solution containing 100 mu M Ca ionophore A23187. Equimolar Ca chelator EGTA completely prevented Ca-induced dwarfing when applied simultaneously. EGTA at 4 mM reduced MS dwarfing as much as 36%, whereas CDTA, another Ca chelator, negated it by 29%. The more general chelator, EDTA, was ineffective in negating MS growth inhibition. Chlorpromazine (25 mu M), 48/80 (400 mu Mg/ml), or calmidazolium (1 mu M), different inhibitors of calmodulin, negated MS dwarfing up to 35%. Although Ca and calmodulin seem to play a role in MS dwarfing, the partial success of chemical probes to negate the dwarfing suggests that other factors also contribute to the response.

Impacts
(N/A)

Publications

Progress 01/01/86 to 12/30/86

Outputs
Research centered around projects related to flood stress tolerance, optimum productivity of controlled environment lettuce and mechanical stress effects on crop productivity. Sixty different tomato breeding lines from international sources were screened for relative flood tolerance. Two lines were identified for further experimental work. They include Lycopersicon esculentum PI 406966 and Lycopersicon peruvianum PI 128644. The former proved tolerant to anaerobic stress in the root system while the latter was intolerant. The tolerant line 406966 developed massive numbers of adventitious roots from the lower stem following flooding while the intolerant line 406966 did not. The tolerant line also exhibited internal shoot aeration characteristics in contrast to the intolerant line. Survival of the tolerant tomato line appears to depend on the formation of a replacement root system near the flood line. Studies were conducted to optimize biomass production for hydroponic lettuce in controlled environments by varying nutrition, CO(2), temperature and light intensity. Biomass production obtained was significantly in excess of that reported in previous literature. Experiments were conducted to determine the impact of mechanical stress on plant growth in greenhouses compared to outdoor environments. Results indicate that mechanical stress reduces plant growth more markedly under greenhouse conditions or outdoor windless environments than in an outdoor windy environment.

Impacts
(N/A)

Publications

Progress 01/01/85 to 12/30/85

Outputs
Cultural and environmental parameters were varied in effort to optimize the hydroponic production of leaf lettuce (Lactuca sativa L.) in controlled environments. Various cultivars were screened for growth stimulation by high irradiance lighting from fluorescent + incandescent lamps. Growth stimulation by high light was found to be cultivar dependent and to require nitrogen enrichment of the Hoagland's nutrient solution. Double-strength nitrogen as 5 mM NH+/4 + 25 mM NO-/3 stimulated lettuce productivity at photosynthetic photon flux densities (PPFDs) as high as 932 micro-mol sm of photosynthetically-active radiation. Growth response to output from various lamp types was similar at low PPFD (300 micro-mol sm), but was repressed at high PPFD (900-1100 micro-mol sm) from mixed lamp sources containing a high proportion of output from high intensity discharge lamps. Highest yield thus far obtained has been with a high proportion of output from incandescent lamps, enhancement of CO(2) to 1500 micro-1 1, and N enrichment as described. Crop growth rate under these conditions was 55-60 g dry weight edible biomass m of growing area day during the exponential growth period. Relative growth rates as high as 0.9 g g day occurred only during the first several days of exponential growth under optimizing conditions, but tapered off rapidly thereafter regardless of conditions, suggesting that energy and resources might be saved by exploiting only the most responsive times during crop development.

Impacts
(N/A)

Publications

Progress 01/01/84 to 12/30/84

Outputs
Controlled environment, hydroponic production of leaf lettuce was found to have potential for contributing vitamins and minerals to a balanced vegetarian diet, revitalizing atmosphere throughout production, and recycling nitrogenous and other wastes in a space-deployed, regenerative life support system. The Lactuca sativa L. cultivars 'Waldmann's Green' and 'Black-seeded Simpson' showed particular promise for accelerated growth under optimizing controlled environment conditions. Photosynthetic photon flux densities :900 mu mol sEPGmEy for 20 h bold center dot day EPG plus 1500 mu 1 bold center dot 1EPG CO(2) resulted in the highest growth rates over a 19-day production period from seed to harvest. Colloidally-dispersed triacontanol applied to lettuce in combination with high PPFD/high CO(2) high have resulted in relative growth rates >500 mg DW new biomass bold center dot g DWEPG bold center dot day EPG and yield rates >50 g DW bold center dot mEy of growing area bold center dot day EPG during exponential growth. When illumination was provided by a mixture of high intensity discharge lamps, better growth was obtained during a 20 h photoperiod when high pressure sodium vapor lamps were energized 14 h bold center dot day EPG than if energized 20 h bold center dot day EPG, while receiving 20 h bold center dot day EPG radiation from metal halide plus quartz iodide lamps.

Impacts
(N/A)

Publications

Progress 01/01/83 to 12/30/83

Outputs
Mechanical stress in the form of twice-daily gyratory shaking or manual stem rubbing reduced the growth and dry weight gain of soybean plants in a controlled environment room. A decline in relative growth rate of only 5 to 8% led to a 21% decline in cumulative plant dry weight relative to undisturbed controls over an 18-day treatment period. All of the decline in dry weight gain was due to lower net assimilation rate, which is a measure of photosynthetic productivity. Shaken plants transpired 17% less than controls during the first 45-minute period following a 5-minute shake at 240 rpm, and the water loss rate still averaged 15% less during the second 45-minute period after shaking. The leaf water potential of shaken soybean plants was 39% higher than that of unshaken plants 30 minutes after a shaking episode. Photosynthetic CO2 fixation rates (Pn) fell 10% during the actual 5-minute shaking period, and then continued to decline to 16% less than the control rate 20 minutes after the shake began. Pn of shaken plants still averaged 12% less than that of controls 50 minutes after shaking. The net effect of this decline in Pn after 12 days of three-times-daily treatment was a 25% decrease in whole plant dry weight and a 27% decrease in leaf area. All of these observations are consistent with a stress-induced decline in stomatal aperture, although leaf resistance analysis is in progress to determine the relative contributions of stomatal and mesophyll resistances.

Impacts
(N/A)

Publications

Progress 01/01/82 to 12/30/82

Outputs
Relative growth rate (RGR) of soybean plants either shaken or rubbed was reducedrelative to that of control plants. Virtually all of the decline in whole plant dry weight was due to reduced net assimilation rate (NAR) rather than to leaf area ratio (LAR), which relates to RGR x LAR. This reduction in photosynthetic productivity apparently is due to mechanical stress-induced reduction in stomatal aperture. We also found that flood-tolerant species such as red maple and river birch survive flood stress even if the lower stem is maintained anaerobic by gassing with humidified N(2) or wrapping with alternating layers of Parafilm and lanolin. This is negative evidence for internal aeration of flooded root tissues by the lower shoot. Formation of stem hypertrophy, lenticel intumescence, and adventitious roots were not essential for the tolerance of these species to flooding. In our study of the role of oxidative metabolism in regulating germination of 'Grand Rapids' lettuce seeds, inhibitors of cyanide-sensitive respiration (e.g., HCN) and cyanide-resistant respiration (e.g., SHAM) stimulated seed germination while inhibiting seed O(2) consumption in the absence of light. Additional inhibitors which block at specific points in the respiratory chain are being used to determine the importance of organized respiration in seed germination.

Impacts
(N/A)

Publications

Progress 01/01/81 to 12/30/81

Outputs
Results of experiments on mechanical stress of herbaceous plant suggest that photosynthetic productivity of soybeans shaken periodically throughout the day is significantly retarded, whereas that of plants shaken continuously at low levels is either not affected or is mildly stimulated. Net assimilation rate of periodically shaken plants appears to be inhibited. In controlled-environment agriculture, leaf lettuce growth was stimulated significantly by high light levels (900 muEmEysEPG), continuous 25C during 20 hour days and 4 hour nights, and souble-strength N as NO(3)E + NH(4)RG in an 8:1 molar ratio in hydroponic culture. In studies investigating the physiology of flood tolerance in woody plants, the lower 18 inches of trunk in flood-tolerant red maple seedlings seems to be important for internal aeration f flooded root systems and contributes to tolerance. This was found in studies where lower trunks were gassed with N(2) during flooding and stress systems were increased.

Impacts
(N/A)

Publications

Progress 01/01/80 to 12/30/80

Outputs
Sensitivity of several herbaceous plant species grown in greenhouses to mechanical stress was found to be greatest in summer and least in winter. Plant dwarfing in response to shaking could be restored in summer by growing plants under at least 50% shade. Stimulation rather than retardation of plant growth in controlled environments was observed in response to low amplitude (less than 2 mm), high frequency (2000 cpm) vibration. Shaking increased the cellulose content, modulus of elasticity, and ability of stems to support shoot weight of tomato plants grown in a greenhouse during the winter. Stem strength is limiting to shoot support during the winter but not during the summer, and mechanical stress substitutes for high summer light intensity during the low light conditions of winter.

Impacts
(N/A)

Publications

Progress 01/01/79 to 12/30/79

Outputs
Mechanical vibration was found to significantly stimulate growth of tomato seedlings under conditions of rigidly controlled environments, including high humidity. Germination of seeds of a number of species was found to be inhibited by low levels of cyanide presented as HCN but not as KCN. Root respiration capacity of roots of tree species intolerant of flooding decreased greatly after several days of flooding, whereas roots of tolerant species decreased only slightly, suggesting that differential damage to the aerobic respiratory apparatus may be responsible for differential flood stress in woody plants. Herbaceous species grown in a greenhouse in the winter were prostrate and weak unless shaken for several minutes daily, after which they remained erect and strong. Similar plants grown in a greenhouse under the environmental conditions of summer retained upright growth habits without shaking treatments.

Impacts
(N/A)

Publications

Progress 01/01/78 to 12/30/78

Outputs
Six plant growth chambers have been constructed which have the following environmental control capabilities: modified atmospheres of CO(2), O(2), and C(2)H(4); hypobaric (reduced atmospheric pressure) or nonhypobaric modes of operation; close temperature and humidity control; subjection of the entire chamber and its contents to controlled mechanical disturbance. One of the many uses for this system will be to help determine the role of the volatile growth regulator ethylene in mechanical retardation of plant growth. Investigations of flood tolerance in woody plants revealed that the respiratory capacity (Qo(2)) of roots of relatively tolerant species (baldcypress, red maple) remains higher than that of less tolerant species (sugar maple) when subjected to waterlogging, even when tested under conditions of low O(2) tension. In studies of metabolic regulation of red ligh-dependent lettuce seed germination, it was found that certain combinations of inhibitors of the classical (CN-sensitive) and alternative (CN-resistant) electron transport pathways could substitute for light in stimulating full germination in darkness. In addition, seed germination of a number of crop species reputed to be insensitive to inhibitation by CN was in fact found to be inhibited by low levels of CN if supplied as gaseous HCN.

Impacts
(N/A)

Publications

Progress 01/01/77 to 12/30/77

Outputs
Studies on mechanical regulation of plant growth have been extended to reproductive growth and change of growth habit. Brief, daily seismic disturbance (shaking) was found to: (a) Convert greenhouse-grown soybeans from a prostrate, vining growth habit to an erect, bushy habit; (b) be mimicked by continuous exposure to outdoor hardening conditions; (c) delay fruiting and fruit development in Rutgers tomato but enhance fruit set; (d) enhance growth of tubers in potato and Jerusalem artichoke; (e) retard flowering and fruit development in Alaska pea. In another area, flood tolerance of Baldcypress was positively correlated with development of "flood roots" concomitant with death of "soil roots." These new roots, which develop under flood stress, utilize O(2) more efficiently under reduced O(2) tensions than do normal soil roots. In a third area, we have shown that phytochrome-mediated potentiation of germination in photoblastic lettuce seeds is dependent on a CN-insensitive, hydroxamic acid sensitive (alternate) process which may be linked to mitochondrial respiration.

Impacts
(N/A)

Publications

Progress 01/01/76 to 12/30/76

Outputs
Inhibition of plant growth by vibrational or tactile mechanical stimulation is accompanied by reduced dry weight gain and transitory stomatal aperture reduction, but specific photosynthetic and respiratory rates are not altered. Dry wt effect is the result of reduced leaf area. This "mechanical dwarfism" seems to have a hormonal basis, and stress applied to an intact plant specifically inhibits the auxin-dependent component of stem growth. Tactile stimulation of the shoot apex also antagonizes the ability of sections cut from subapical internodes to transport auxin in a polar manner. The volatile hormoneethylene mimics some of the effects of mechanical treatment. In another area, the transition from the dormant to the nondormant state in light-requiring lettuce seeds has been shown to require the operation of a CN-insensitive, SHAM-sensitive (alternate) respiratory pathway, which is poorer in energy transduction (ATP formation) and has a lower affinity for oxygen as a terminal electron acceptor than the classical, CN-sensitive pathway. In a related area, the roots of flood-intolerant tree species such as Sugar Maple tend to have a greater proportions of their total respiration alternate under stress conditionsthan do roots of more tolerant species such as Red Maple.

Impacts
(N/A)

Publications

Progress 01/01/75 to 12/30/75

Outputs
Mechanical stress inhibition of plant growth was mechanized this year for possible commercial application in greenhouses. Conditions were optimized for the application of motion to plant shoots to control their growth. It seems that stress applied during the night is more effective than during the day in slowing growth. Among physiological effects on plants as a result of mechanical stress such as might occur from wind action are included inhibition of translocation of photosynthate, photosynthesis, and polar auxin transport. Thereseems to be a role for the gaseous hormone ethylene in this phenomenon, althoughcause or effect is not yet clear. Shaken or rubbed plants were found to develop less leaf area, possibly accounting for the fact that stressed plants develop less dry weight than protected plants. Mechanical stress of unhardened plants isfurther characterized by a transient stomatal closure and reduced rate of transpiration, although recovery occurs within one hour. It is suggested that computer modeling of crop performance in the field based upon growth chamber studies and data collected with unhardened, indoor-grown plants may overestimateproductivity in the field. It is necessary to account for hardening factors in the field, such as wind, which may not occur to the same extent indoors.

Impacts
(N/A)

Publications

Progress 01/01/74 to 12/30/74

Outputs
Mechanical stress inhibition of plant growth was found to be a complex physiological phenomenon. In unhardened plants translocation of assimilates wasfound to be more inhibited than photosynthesis. In hardened plants the reverse is true. Mechanical stress inhibition of auxin transport seems to also play a role in dwarfing. A direct role for ethylene seems doubtful. Stomatal apertureand transpiration remain sensitive to a single mechanical disturbance for days.

Impacts
(N/A)

Publications

Progress 01/01/73 to 12/30/73

Outputs
A general dwarfing effecton vegetative plant growth was observed in a number of species in response to mechanical stress such as shaking, flexing, and rubbing. The results suggest a profound effect of wind on the morphogenesis of natural plant populations. Red light inhibits Avena plasma membrane-bound ATPase and far-red light reverses the effect. The results suggest a physiological tool forfurther investigating photoregulatory phenomena.

Impacts
(N/A)

Publications