Progress 10/01/99 to 09/30/05
Outputs
This project on horticultural crop water requirement has, during it's tenure, supported research that has resulted in over 60 scientific journals and over 200 other technical publications in the general area of plant-soil-atmosphere-water relations and the technology for plant-soil-water, environmental, plant physiological, plant ecolophysiological, ecological, and other measurements. The results of this work has supported basic as well as applied horticultural and plant physiological research and directly supported horticultural practitioners in the public sector. Work supported by this projectd on the physical amendment of shallow-drained soils is particularly notworthy.
Impacts
In addition to shedding light on a classic and prevalent horticultural soil problem, the model developed from this work formed the basis for the development of soil mictures used worldwide in U.S. Golf Association Greens Section greens.
Publications
- No publications reported this period
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Progress 01/01/04 to 12/31/04
Outputs
The effect of sand amendment source on the properties of sand-soil mixtures was investigated. It was found that the physical properties of even mono-disperse amendment of the same textural classification varied sufficiently from place to place and even from the same site from time to time to require alteration of the prescribed mix recipies. General mixture guidelines can be established; however, these were found to require refinement in order to produce a consistent water-air ratio in the mix. This variation in amendment physical properties did not affect the mix stability, including compaction resistance. A simple empirical test has been developed to determine the requisite recipe changes in each situation. This will be published as a departmental fact sheet.
Impacts
A previous soil physical amendment model by the investigator formed the basis for the development of the soil mixtures recommended for worldwide use in U.S. Golf Association Greens Section Greens. It is expected that this model will improve the reliability of blending and testing soils for golf greens and other shallow-drained soils. Billions of container-grown plants are grown annually in the U.S. alone. Soils in these shallow-drained areas tend to be poorly aerated due to excess water retention. This model will improve the blending and testing of soils for containers, thereby potentially reducing crop loss due to the effects of poor soil aeration.
Publications
- Beasley, J.S., Branham, B.E. and Spomer, L.A. 2004. Seasonal canopy carbon exchange rates of trinexapac-ethyl and paclobutrazol-treated Kentucky bluegrass. CD-ROM. In: 2004 Agronomy Abstracts. ASA, Madison, WI.
- Han, S., Fermanian, T.W., Juvik, J.A. and Spomer, L.A. 2004. Total nonstructural carbohydrate storage in creeping bentgrass treated with trinexapac-ethyl. HortSci. 39(6):1461-1464.
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Progress 01/01/03 to 12/31/03
Outputs
An improved, simple linear model to predict water retention and aeration has been developed for bidisperse container and other shallow-drained soils for use in greenhouses, nurseries, roof top gardens, football or other athletic fields, and golf greens and tees. It applies to bidisperse soil mixtures where one component particle size is several magnitudes smaller than the other and thereby fits between the pore spaces of the larger particle (for example silty clay loam (small) and very coarse-textured sand (large). Inputs are bulk porosity and bulk proportions of both fractions and output is total, water retention, and aeration porosity of the mixture.
Impacts
A previous soil physical amentment model by the investigator formed the basis for the development of the soil mixtures recommended for worldwide use in U.S. Golf Association Greens Section Greens. It is expected that this model will improve the reliability of blending and testing soils for golf greens and other shallow-drained soils. Billions of container-grown plants are grown annually in the U.S. alone. Soils in these shallow-drained soils tend to be poorly aerated due to excess water retention. This model will improve the blending and testing of soils for containers, thereby potentially reducing crop loss due to the effects of poor soil aeration.
Publications
- No publications reported this period
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Progress 01/01/02 to 12/31/02
Outputs
Plant water deficit is the major factor limiting global crop We have concluded a study intended to determine Coleus x hybridus Voss. 'Goldbound' water requirement based on physiological responses most directly related to yield: expansion, stomatal conductance, net photosynthesis, dark respiraton, and survival (injury). Fully-expanded, mature leaves proved the most representative and consistent indicators of whole plant water status as measured with a pressure chamber and vapor pressure osmometer. The most consistent time for water status measurement was at night or under other low-transpiration conditions. Coleus survived dehydration up to 6 days with no perceptible injury, and 46 days based on ability to resume growth. Leaf expansion proved most sensitive to dehydration and even ceased before wilting could be perceived. Stomatal conductance and subsequent reduced intercellular CO2 level was decreased next followed by net photosynthesis, which cesed at a water
potential of -0.72 MPa. Although reduced, dark respiraton never stopped throughout the water deprivation period. Leaf abscission began at a very low water potential, with all mature leaves eventually lost at -1.05 MPa. Coleus appeared to develop morphological and physiological resistance to water deficits less than or equal to about -0.65 MPa.
Impacts
Plant water deficit is the major factor limiting global crop productivity. Yield loss caused by water stress is estimated to exceed total loss from all other causes. Moreover, availability of agricultural water is declining worldwide because of increasing demand and decreasing quality. Consequently, knowledge of plant water requirement is mandatory for increasing water use efficiency and reducingground water pollution.
Publications
- No publications reported this period
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Progress 01/01/01 to 12/31/01
Outputs
Soil temperature and moisture are the main factors influencing soil CO2 evolution. Soil tillage affects soil physical factors such as pore size distribution, penetration resistance, bulk density etc. It is therefore important to include these factors in the equation for estimating soil CO2 evolution. To investigate the influence of these soil physical factors on CO2 evolution, principal component analysis (PCA) was implemented on three field sites which containing different levels of soil organic carbon. In each site, conventional tillage and no tillage have been applied. Soil CO2 evolution rates were measured biweekly during growing season with Li-Cor 6400. Soil temperature, moisture content, penetration resistance, bulk density and pore size distribution were measured at 0-5, 5-15, 15-30 cm depths. The first principal component is highly correlated with soil temperature, moisture and penetration resistance. The second principal component is correlated significantly
with bulk density. It suggests that soil structure has a strong influence on soil CO2 evolution and the general soil respiration model is improved if this information is included. Laboratory incubations are also being conducted to confirm the field measurements. This study required the development of a method for rapidly inducing identical, known soil moisture levels in undisturbed soil samples for the incubation. Commonly used methods are inaccurate. Two different suction plate techniques are being compared with the precise, but more difficult pressure plate equilibration to see if the moisture equilibration can be done more quickly.
Impacts
This work will provide information leading to the improvement of crop production efficiency and soil conservation.
Publications
- YOO, G., WANDER, M., SPOMER, L. and BOLLERO, G. 2001. Influence of soil physical factors on CO2 evolution in agricultural fields under different tillage. Abstract s06-yoo134721. ASA-CSSA-SSSA Ann. Meetings, Charlotte, NC, 21 Oct 2001.
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Progress 01/01/00 to 12/31/00
Outputs
A simple inexpensive suction plate apparatus was constructed from off the shelf 2 inch plastic plumbing fittings and commercially produced 0.5 bar ceramic plates. These were successfully tested and are currently being used for measuring the water retention isotherms for intact and disturbed soil samples. A commercial Soil Moisture Equipment Co. pressure plate is being used to measure the water retention isotherms of soil aggregates 0.5, 2, 4 and 8mm in diameter from prairie and cultivated soils to determine the nature of changes to soil aggregation resulting from cultivation. This data will be used in a study of soil organic matter dynamics under cultivated and non-cultivated systems. Similar measurements on commonly-used porous horticultural soil amendments will be used to assess their contribution to manufactured media soil water availability. An apparatus has been constructed in a walk-in growth chamber to determine the effect of soil water availability and lamp
type on leaf thermal balance and temperature under supplemental lighting systems. The lamp and leaf spectral properties are being measured with a spectroradiometer and integrating sphere. The measurements are being made under all the commonly-used supplemental lighting sources.
Impacts
Plants contain and use more water than any of the other raw materials contributing to their growth and function. All of this water is absorbed from the soil by the plant's roots. It is important to maintain a good soil environment and a good supply of available water in the soil. Both of these are largely determined by the nature of the soil pore system. Measurement of the water retention isotherm is the best single indicator of the nature of the soil pore system and thereby the soil's physical suitability for plant growth. Supplemental lighting is widely used in horticultural growing systems. The commonly used lamps have widely-different spectral emissions. This study is looking at the interaction between the spectral properties of the lamp and leaf and leaf water relations as determined by soil water availability.
Publications
- No publications reported this period
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Progress 01/01/99 to 12/31/99
Outputs
Soil physical amendment with coarse-textured organic or inorganic particulates is commonly used in shallow-drained horticultural soils utilized in containers, sporting areas, and landscape sites to add large pores which drain and provide adequate aeration. A wide variety of materials are used for this purpose and these have a corresponding range of efficacies for this purpose. Simple, inexpensive apparatus have been made from common plumbing parts to measure media water retention isotherms and thereby porosity, water retention porosity, and aeration porosity in the drained media. A study of one of the newer materials, LECA (light expanded clay amendment), indicated its contribution to soil physical properties when used as an amendment was similar to that of non-porous amendments such as river sand or gravel. Its internal porosity contributes nothing to soil aeration and the water retained therein is not readily available for plant use. Similar studies are underway on
other new amendments produced from waste paper, ground tires, and compost.
Impacts
Results from this work could potentially impact water use efficiency and container plant production. It could lead to better formulated container soil mixtures using less expensive components and leading to cheaper production through more controlled use of water and minerals. Moreover, this control could also result in higher quality crops.
Publications
- SPOMER, L.A. 1999. Water retention of light expanded clay amendment. Communic. Soil Sci and Plant Anal. 29 (9&10):1265-1276.
- HAN, S.W., FERMANIAN, T.W., JUVIK, J.A., and SPOMER, L.A. 1999. Total nonstructural carbohydrates in creeping bentgrass treated with trinexapac-ethyl. Crop Science (Submitted).
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Progress 10/01/97 to 09/30/98
Outputs
Soil physical amendment with coarse-textured organic or inorganic particulates is commonly used in shallow-drained horticultural soils utilized in containers, sporting areas, and landscape sites to add large pores which drain and provide adequate aeration. A wide variety of materials are used for this purpose and these have a corresponding range of efficacies for this purpose. A study of one of the newer materials, LECA (porous, light expanded clay amendment), indicated its contribution to soil physical properties when used as an amendment was similar to that of non-porous amendments such as river sand or gravel. Its internal porosity contributes nothing to soil aeration and the water retained therein is not readily available for plant use. Similar studies are underway on other new amendments produced from waste paper, ground tires, and compost.
Impacts
(N/A)
Publications
- Spomer, L.A. 1998. Water retention of light expanded clay amendment. Communic. Soil Sci and Plant Anal. 29 (9 & 10): 1265-1276.
- Han, S.W.; Fermanian, T.W.; Juvik, J.A. and Spomer, L.A. 1998. Growth retardant effects on visual quality and nonstructural carbohydrates of creeping bentgrass. HortScience 33(7): 1197-1199.
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Progress 10/01/96 to 09/30/97
Outputs
Shallow-drained horticultural soils utilized in containers, sporting areas, and landscape sites tend to retain excess water and thereby be poorly aerated following irrigation or precipitation. This problem is usually corrected by soil physical amendment with coarse-textured particulates to add large pores which drain and provide adequate aeration. A study of one of the newer materials used for this purpose, LECA (porous, light expanded clay amendment), indicated its contribution to soil physical properties when used as an amendment was similar to that of non-porous amendments such as river sand or gravel. Its internal retained water is not readily available for plant use. Water loss during plant tissue culture media preparation and storage was determined and found to be significantly greater than that reportedly causing culture growth effects. The growth effect is generally attributed to change in media water availability; however, sensitive suction plate measurements
indicate a 0.1 percent media solid mass increase decreases water potential by only about 1.0 cm H2O with no perceptible decrease in media water conductivity. This minute change in water availability is negligible relative to that known to affect in vivo plants indicating some other factor is involved in culture response than water.
Impacts
(N/A)
Publications
- CHEN, G.Y. 1997. Effect of airflow and carbon dioxide on growth, yield, and gas exchange of lettuce. Ph.D. Thesis, Department of Natural Resources and Environmental Sciences, University of Illinois, Urbana.
- SPOMER, L.A. and M.A.L. SMITH. 1996. Direct measurement of water availability in gelled plant tissue culture media. In Vitro Cell. Dev. Biol. Plant 32:210-215.
- SPOMER, L.A. and T.W. TIBBITTS. 1997. Humidity. Chapter 3 in Growth Chamber Handbook. (ed. R.W. Langhans and T.W. Tibbitts) USDA/CSRS North Central Regional Publication 340:43-64.
- SPOMER, L.A., T.W. TIBBITTS and W. BERRY. 1997. Plant culture in solid media. Chapter 7 in Growth Chamber Manual (ed. R.W. Langhans and T.W. Tibbitts) USDA/CSRS North Central Regional Publication 340:105-118.
- TOLEDO, J.U., L.A. SPOMER, and M.A.L. SMITH. 1997. Changes in media water status during preparation and storage. Biotronics 26:59-66.
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Progress 10/01/95 to 09/30/96
Outputs
Previous studies have indicated that seemingly insignificant change in gelled media solid concentration (on the order of 0.1% by mass) significantly affects plant tissue culture response. This effect is generally attributed to a change in media water availability. A sensitive suction plate apparatus adapted to measure media water potential indicated that a 0.1% media solid mass increase reduced water potential by only about 1.0 cm H2O and had no perceptible effect on media water conductivity. This minute change in water availability is negligible relative to that known to affect in vivo plants. A controlled atmosphere (CA) study investigating the effectiveness of low O2 or high CO2 storage atmospheres in reducing post harvest degradation of sweet corn quality (primarily sugar content) indicated very significant reductions in respiration and loss of carbohydrates, especially sugars. These results indicate that CA storage might well prove a relatively simple and useful
supplement to the traditional refrigerated storage as a method of preserving sweet corn quality. A study of the water requirement of greenhouse grown Coleus blumei indicated the plants were able to survive up to 6 weeks water deprivation but only about 6 days without permanent reduction in quality or injury. Net photosynthesis, stomatal opening, expansion growth, dark respiration, adaptation, relative water content, water potential, osmotic potential, and plant survival were all measured throughout the period of deprivation.
Impacts
(N/A)
Publications
- SPOMER, L.A. 1994. Use of planetary soils within CELSS: the plant viewpoint. Adv. Space Res. 14(11):411-416.
- HUMMEL, N., SNOW, J., LATHAN, J., BROWN, K., KUSSOW, W., and SPOMER, L.A. (USGA Greens Specification Advisory Committee). 1994. State of the Soil Physical Testing Industry and Recommendations for Standards. USGA Greens Section.
- SMITH, M.A.L. and SPOMER, L.A. 1994. Vessels, gels, liquid media and support systems. in Automation and Environmental Control in Plant Tissue Culture (ed. J.Aitken-Christie, T. Koazi, M.A.L. Smith). Kluwer Academic Publishers. 371-404.
- KUO, YU-JEN, SMITH, M.A. L., and SPOMER, L.A. 1994. Merging callus level and whole plant microculture to select salt-tolerant 'Seaside' creeping bentgrass. J. Plant Nutr. 17(4):549-560.
- BAUBLIS, A., SPOMER, L. A., and BERBER-JIMENEZ, M.D. 1994. Anthocyanin pigments: a comparative study on the stability of several extracts. J. Food Sci. 15(5):1-5.
- N. HUMMEL, SNOW, J., LATHAM, J., BROWN, K., KUSSOW, W., SPOMER, L. A., BAKER,S., WADDINGTON, D. and MCCOY, E. 1994. USGA recommendations for putting green construction. Green Section Record. March/April issue.
- BAUBLIS, A., BERBER-JIMENEZ, M.D., SPOMER, L. A., and SMITH, M.A.L. 1994. Stability of anthocyanins from in vivo and in vitro sources.Proc. INFOCOL Conf. on Natural Food Colors. Amherst, MA., June 1994.
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Progress 10/01/94 to 09/30/95
Outputs
A controlled environment study investigating the effect of airflow and CO2 levelindicated that interaction between the two parameters significantly affects net photosynthesis (lettuce). Airflow should be characterized in all controlled environment studies in order to ensure accurate interpretation of the results. Seemingly insignificant change in gelled media solid concentration (on the order of 0.1% by mass) have been reported to significantly affect plant tissue culture response. This is much less than change observed in this study due to water loss during media preparation and storage. The growth effect is generally attributed to change in media water availability; however, sensitive suction plate measurements indicate a 0.1% media solid mass increase decreases water potential by only about 1.0 cm H2O with no perceptible decrease in media water conductivity. This minute change in water availability is negligible relative to that known to affect in vivo plants. A
study of the water requirement of greenhouse grown Coleus blumei indicated the plants were able to survive up to 6 weeks water deprivation but only about 6 days without permanent reduction in quality or injury. Existing tissues developed resistance to subsequent water deficit. Net photosynthesis, stomatal opening, expansion growth, dark respiration, adaptation, relative water content, water potential, osmotic potential, and plant survival were all measured throughout the period of deprivation.
Impacts
(N/A)
Publications
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Progress 10/01/93 to 09/30/94
Outputs
Previous studies have indicated that seemingly insignificant change in gelled media solid concentration (on the order of 0.1% by mass) significantly affects plant tissue culture response. The effect is generally attributed to a change in media water availability. A sensitive suction plate apparatus, adapted to measure media water potential indicated that a 0.1% media solid mass increase reduced water potential by only about 1.0 cm H2O and had no perceptible effect on media water conductivity. This minute change in water availability is negligible relative to that known to affect in vivo plants. These results will be published in a 1995 M.S. thesis. A controlled atmosphere (CA) study investigating the effectiveness of low O2 or high CO2 storage atmospheres in reducing post harvest degradation of sweet corn quality (primarily sugar content) indicated very significant reductions in respiration and loss of carbohydrates, especially sugars. These results indicate that CA
storage might well prove a relatively simple and useful supplement to the traditional refrigerated storage as a method of preserving sweet corn quality. This study has been published in a 1995 Ph.D. thesis. The complete summary is available from the IAES main office.
Impacts
(N/A)
Publications
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Progress 10/01/92 to 09/30/93
Outputs
Preliminary growth chamber experiments studying the interaction between air movement and atmospheric carbon concentration and net photosynthesis indicated increase in net photosynthesis to a maximum with increased air flow at all experimental carbon dioxide levels. Most leaf or canopy photosynthesis studies, including those investigating the greenhouse effect ignore air flow. This study will establish standards for controlling air flow in growth chambers and greenhouses. Post harvest sweet corn quality (sugar content) decreases rapidly from the time it is harvested. A preliminary controlled atmosphere study substituting low oxygen atmosphere (high nitrogen or carbon dioxide) for the usual refrigerated storage of sweet corn indicated very significant reductions in respiration (metabolic activity). Preserved samples are being analyzed for carbohydrate content to determine treatment effect on stored corn quality. Seemingly insignificant changes in gelled media solid
concentration (on the order of 0.1% by mass) have been observed to significantly affect plant tissue culture response. This effect is generally attributed to solid effect on media water availability. Measured media water potential and conductivity indicate very minute changes in water availability relative to levels known to affect in vivo plants.
Impacts
(N/A)
Publications
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Progress 10/01/91 to 09/30/92
Outputs
A controlled environment study of the interaction between air movement and atmospheric carbon concentration net photosynthesis has been initiated. Net photosynthesis increases to a maximum with increased air flow at a given carbon dioxide concentration. Most leaf or canopy photosynthesis studies, including those investigating the greenhouse effect ignore air flow. This leads to conflicting and confusing interpretation of the results. This study will establish standards for controlling air flow in controlled environment studies. Post harvest sweet corn quality (sugar content) decreases from the time it is picked in the field. This degradation is usually retarded through cold storage (reduces metabolic rates). A preliminary controlled atmosphere study substituting low oxygen atmosphere (high nitrogen or carbon dioxide) for refrigerated storage of sweet corn indicated the feasibility of its application to sweet corn production. Continued experiments will establish
recommendations for controlled environment storage for sweet corn. Seemingly insignificant changes in media solid concentration (on the order of 0.1% by mass) have significant effect on tissue culture response. This effect is generally attributed to differences in media water availability. Measured media water potential and conductivity indicate minute changes in water availability. Subsequent studies will measure culture water status and look for factors other than water.
Impacts
(N/A)
Publications
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Progress 10/01/90 to 09/30/91
Outputs
Many horticulture production and research applications compel visual evaluation of product yield or experimental effect. These observations are typically subjective and consequently inconsistent, inaccurate, and difficult to quantify. A technique was developed for using RGB video image analysis for measuring color appearance. This method was verified by direct comparison with spectroradiometric measurement under carefully controlled conditions. When the spectral characteristics of both systems' light sources and sensors were meticulously characterized and normalized, video image analysis color perception proved consistent with that of the spectroradiometer. The water requirement of greenhouse-grown Chrysanthemum morifolium Ramat. for various growth functions relating to ultimate yield was determined. Although leaf net photosynthesis significantly increased during early stages of deprivation, it subsequently declined dramatically as water deficit developed. Net
photosynthesis is assumed to have responded to the decline in stomatal conductance paralleling increasing tissue water stress. Intercellular CO(2), however, failed to significantly respond to water deprivation. Photosynthesis, expansion, and stomatal conductivity also mirrored the changes in leaf water status on a diurnal basis. Overall leaf area declined significantly with water deprivation (correlation, R(2)=0.85) and resulting decrease in osmotic potential.
Impacts
(N/A)
Publications
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Progress 10/01/89 to 09/30/90
Outputs
Greenhouse-grown Chrysanthemum morifolium Ramat. physiological water requirements were determined by evaluation of the consequence of water deprivation on selected yield parameters. The critical stress limits were determined for net photosynthesis, dark respiration, expansion growth, leaf abscission, and permanent wilting (survival). Chrysanthemum proved very sensitive and responsive to water deficit. Although it dynamically counteracted water stress through osmoregulation, plants grown under normal cultural conditions still exhibited relatively high (low stress) permanent wilting points (10-12 mPa water potential). Exact limits depended on rate of imposition of stress and the plant's cultural history. These studies were salient in establishment of previously unknown 'critical' water stress limits essential for conceptualizing comprehensive Chrysanthemum water requirements. An in vitro study corroborated Chrysanthemum's ability to osmoregulate; however, in vitro
adaptation to water stress was not retained when transplanted plants were grown in vivo. A technique utilizing a spectroradiometer and accompanying integrating sphere has been developed to calibrate microcumputerized video image analysis color measurements of plant tissues. The technique is being used for Zinnia flower color quantification.
Impacts
(N/A)
Publications
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Progress 10/01/88 to 09/30/89
Outputs
The water stress physiology (physiological and cultural water requirement) of greenhouse-grown chrysanthemum, Chrysanthemum morifolium Ramat. was studied. Despite the significant and immediate effect water deficit has on its growth and survival, knowledge of the water requirement of chrysanthemum is still quite nebulous. To alleviate this nescience, preliminary experiments observed the consequence of water deprivation on selected yield parameters (photosynthesis, dark respiration, expansion growth, leaf abscission, permanent wilting (survival), color, etc.) to determine the 'critical stress limits' for each of these functions. This plant was observed to be very sensitive and responsive to water deficit. Although chrysanthemum dynamically resists stress through osmoregulation, plants grown under normal cultural conditions had a permanent wilting point of 10-12 mPa water potential. Exact limits depend on the rate of imposition of stress and the plant's cultural
history. Although incomplete, these studies are salient in establishment of previously unknown 'critical' water stress limits essential for conceptualizing comprehensive chrysanthemum water requirements. A study determining the physical requirement for woody plant root growth and function has been initiated in aeroponic growing systems. A color microcomputerized video image analysis system for quantifying subtle tissue color differences is currently being developed for use in these and other studies.
Impacts
(N/A)
Publications
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Progress 10/01/87 to 09/30/88
Outputs
This project studied the water stress physiology (physiological and cultural water requirement of Pohtos, Epipremum aureum), and effects of osmotic stress on Tomato, Lycopersicon sp. Despite the significant and immediate effect water deficit has on its growth and survival, knowledge of the water requirement of Pothos and tomato still quite nebulous. To alleviate this nescience, project experiments observed the consequence of water deprivation on various yield related growth activities of Pothos (photosynthesis, dark respiration, expansion growth, leaf abscission, color, etc.) to determine the 'critical stress limits' for each of these functions. It was observed that, although of tropical origin, this plant is very water stress resistant. In terms of critical stress, Pothos water stress resistance is quite nebulous; exact limits depend on the rate of imposition of stress and the plant's cultural history. Although somewhat preliminary in nature, the information
acquired in these studies has been salient in the establishment of previously unknown 'critical' water stress limit spans essential to the conceptualization of comprehensive Pothos water requirement. Another significant contribution of this project has been the development of microcomputerized video image analysis as a research measurement tool.
Impacts
(N/A)
Publications
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Progress 10/01/86 to 09/30/87
Outputs
A preliminary study of Pothos water requirement has been completed. Yield components expansion growth, net photosynthesis, dark respiration, and survival were investigated as a function of plant water status. Expansion growth ceased at about -0.2 mPa and net photosynthesis at about -.025 mPa water potential. The tissue did not survive water potentials lower than about -2.0 mPa. This research will continue with an investigation into the plant's ability to adapt to water stress. A novel microcomputerized video image analysis leaf chlorophyll measurement technique was developed to enable direct comparisons of net photosynthesis despite the inconsistent and irregular leaf chlorophyll variegation in Pothos. Chlorophyll density is determined in less than a minute from a transmission video image of an intact leaf. The ability of the same image analysis equipment to precisely quantify tissue shrinking and swelling when exposed to external solutions of known water potential
was also utilized in a novel isopiestic measurement of plant tissue water status in a study of the osmolarity of tomato species. It provides an alternative technique for tissues impossible to measure with the pressure chamber and difficult to measure with the thermocouple psychrometer.
Impacts
(N/A)
Publications
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Progress 01/01/86 to 09/30/86
Outputs
A study of Pothos water requirement in which the critical stress limits for expansion growth, stomatal opening, net photosynthesis, and survival is nearly completed. Pothos critical stress limits have been observed during water deprivation studies to be more nebulous than expected, with the plants' leaves responding differently depending on their age, position on the plant, cultural history, and rate and extent of onset of water stress. This is especially so for survival because the plant dies in degrees with the older leaves senescing and abscising much before the younger leaves. The development of a microcomputer image analysis technique for measuring root extent was completed. The method's practical applications have been limited to plants with relatively small root systems with the current hardware and software, but, can potentially be extented to larger root systems through serial imaging or hardware capable of a higher degree of resolution. A second microcomputer
image analysis system has been developed for measuring in vitro cell culture growth (rapid, non- intrusive, accurate), leaf chlorophyll content (intact leaves), and isopiestic tissue water potential (immersed leaf disk method). These are all unique applications which greatly facilitate research measurements in a broad area of plant and animal research.
Impacts
(N/A)
Publications
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Progress 01/01/85 to 12/30/85
Outputs
Two different computer assisted video-image analysis systems have been developed, one to measure leaf area and root growth and the other to measure tissue culture cell growth. These image analysis systems allow rapid, objective, non-destructive, and non-intrusive measurements of previously difficult to characterize parameters. Both systems utilize off-the-shelf hardware, and IBM PC microcomputers, so they are relatively inexpensive to assemble. Although the hardware systems are working, further software development is required to facilitate data processing. The root growth measurement system is being used to characterize root growth patterns as an index to screen tomato varieties for drought resistance. It is also used as a leaf area meter in photosynthetic measurements in the investigation of greenhouse plant water requirement. The cell growth measurement system will be used in an investigation of osmolarity effects on protoplast culture growth in addition to
various other studies.
Impacts
(N/A)
Publications
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Progress 01/01/84 to 12/30/84
Outputs
Preliminary studies investigating critical water stress levels of greenhouse-grown Chrysanthemum morifolium revealed tissue permanent wilting (zero turgor) to range from about -8 to -17 x 101 Pa water potential, corresponding to a relatively constant water content of about 88% relative turgidity. The variation of permanent wilting point water potentials between tissues grown under different degrees of water stress apparently resulted from changes in tissue osmotic potentials (osmoregulation). Water potential was measured by the isopiestic thermocouple psychrometer method. A simple, inexpensive (about $10), proportional temperature controller was developed and adapted for multipurpose use. Its demonstrated precision is 0.02C in a stagnant-air chamber over 24 hours and 0.005C in a stirred water bath. This controller has been used successfully in post-harvest, water relations, seed germination, mineral nutrition, and herbicide studies.
Impacts
(N/A)
Publications
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Progress 01/01/83 to 12/30/83
Outputs
Efforts to establish the critical water stress level beyond which Epripremum aureum does not survive indicated no single critical level exists; rather water deficit and water potential declined to 80-90% and 0.6-1.0 megapascals respectively during the approximately first three weeks of water deprivation after which further declines were moderate over the next ten or so weeks. Plants were capable of recovery with little or no visible damage during the initial three weeks, after which injury increased and survival decreased with time. Leaf resistance to water loss increased four-fold during the first week of deprivation, after which measurements became uncertain due to the difficulty of sealing the porometer to the leaf's surface. The water deficit, potential, and dark respiration of excised stems were also monitored in another attempt to determine critical stress levels. Again, no definite killing stress was observed. Respiration rates declined precipitously during
the first few hours after which they increased for as long as several days as the water deficit developed, and then began a long slow decrease until death. Controlled moderate water deprivation treatments prior to the extended water deprivation increased the plant's resistance to water deprivation injury. The ability to directly monitor water status and respiration or other growth index on the same tissue would greatly enhance the reliability of this type of experiment.
Impacts
(N/A)
Publications
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Progress 01/01/82 to 12/30/82
Outputs
Primary progress on this project has been the further development and testing ofapparatus for the measurement of plant water requirement. A new isopiestic thermocouple psychrometer and improved temperature controller were constructed for plant water potential measurement. A prototype electrophytogram for monitoring plant water status was also assembled and tested; however, problems with the reference electrode necessitated a redesign of the equipment which is nearly ready for additional testing. The direct relationship between electrophytogram readings and plant water status will then be determined. A prototype, small, spring-balanced lysimeter for measuring plant water use was constructed and tested in the greenhouse. The unit required minor modification to minimize temperature effects on its suspension system and is ready for additional testing. An alternative prototype hydraulic lysimeter is also being developed. Preliminary studies into the effect of the
enhanced drainage in transplanted container soils indicate the soil water relations predicted from laboratory drainage column experiments occur in the field. Although the data indicated an effect on plant water status, its significance to plant survival and establishment is uncertain. Future studies in this area are planned to determine the significance of the enhanced drainage from container soils following transplanting.
Impacts
(N/A)
Publications
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Progress 01/01/81 to 12/30/81
Outputs
The limiting factor in plant water research is the inability to monitor water status of intact plant tissues. This project is investigating a new technique, the plant electrophytogram, which promises to solve this problem. This consists of monitoring plant electropotential relative to that of a reference electrode in the soil. Preliminary experiments with this new technique, done in cooperation with its developer, Dr. William Gensler of the Department of Electrical Engineering at the University of Arizona, indicate that the observed electropotential (which has a span of about 200 mV) follows the same diurnal and irrigation cycle patterns as does plant water status. The inserted electrode is thought to behave as a variable capacitor measuring surrounding cell wall tissue shrinking and swelling which, in turn, is a function of its water status. This theory is supported by a very close correlation between simultaneous electrophytogram and stem diameter measurements.
Experiments are underway to establish the relationship between the electrophytogram and the tissue's water status for various horticultural crop plants. If this proves direct, then this technique will be a very valuable tool in the study of plant water relations and in the practical application of the results of such studies to irrigation management.
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Progress 01/01/80 to 12/30/80
Outputs
The water requirement for corn root growth was determined by direct measurement of growth and water potential of roots experiencing different water deficits. Root growth was accurately determined over very short periods (5 to 15 min) with a radial variable transformer and water potential was immediately measured with an isopiestic thermocouple psychrometer. When water deficit was induced relatively rapidly (0 to 20 min), a nearly linear relationship between growth rate (0 to 1.6 mm per hr) and water potential was observed with growth ceasing at about -10 bars. When water deficit was increased over a longer period (6 to 7 hr), osmoregulation occurred and turgor and growth were maintained at lower water potentials (adaptation to water stress occurred). This is the first time this direct relationship has been observed and reported. It delimits the water stress level at which the root can no longer grow to new water supplies. An attempt to determine the water
requirement for the survival of pothos was inconclusive. However, the plant was observed to survive over 3 months of water deprivation by effectively stopping transpirational water loss. A sensitive, weighable lysimeter using a rotary variable displacement transformer has been constructed and is now being tested for determination of quantitative water requirements of crop plants. Studies into the water relations of transplanted container soils is also continuing.
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Progress 01/01/79 to 12/30/79
Outputs
Techniques for characterizing glasshouse and container-grown water requirements are being developed. Small, air-conditioned gas exchange chambers for measurement of intact leaf and whole plant net photosynthesis and dark respiration are being used to determine the light and water requirements of glasshouse foliage crops. Temperature, light, humidity and air flow can be controlled in these chambers. Work on control of carbon dioxide concentration and measurement of leaf water vapor exchange in these chambers is in progress. A weighable lysimeter utilizing mechanical or hydraulic counterbalance and differential transformer mass change detection systems is being developed and tested for direct measurement of water use and mass growth in situ glasshouse bench crops. A laboratory drainage column and fast response tensiometers were used to determine transplanted container soil water relations. Such soils dried out very much faster than the same soils in containers under
otherwise similar conditions. Finer textured soils, as expected, retained more water following transplanting. The significance of these phenomena on plants is now under investigation in greenhouse and field experiments.
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Progress 01/01/78 to 12/30/78
Outputs
Methods of characterizing glasshouse and container-grown crop water requirement are being developed. Small, air-conditioned gas exchange chambers for the measurement of intact leaf and whole-plant net photosynthesis have been built and are under continued refinement. An electromechanical technique utilizing rotary variable differential transformers (RVDT) has been developed to measure expansion growth. These techniques will be used in conjunction with thermocouple psychrometric water potential measurements to characterize plant water requirement for dry matter and expansion growth. The RVDT technique has been demonstrated capable of measuring root growth over a three to five minute period in an associated study of the water relations of root growth. This allows much greater precision in correlating root water status and expansion growth than previous techniques which have required much longer periods (hours to days) to make significant root growth measurements.
The ability to make these measurements over a very short time is essential for the investigation of root water relations and growth since root water relations can change very rapidly. Gas exchange and weighable lysimetric methods for in situ water use measurements are also under development.
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Progress 01/01/77 to 12/30/77
Outputs
The current thrust of this project is to characterize the physiological (stress)and physical (quality) water requirement of selected container-grown and field-grown horticultural crops. In order to provide a basis for the development of cultural recommendations which ensure an optimal supply of water and/or the selection of water stress resistant varieties or cultivars, methods for characterizing the critical limits of water stress relative to expansion growth, dry matter growth, crop yield, crop quality, and plant survival have been developed. Methods for characterizing in situ plant and crop water use (lysimeters, evapotranspirometers) and root grwoth and permeability (environmental effects) are also under development. Most of the progress of this aspect of this project has been in the development of the methods and apparatus essential to the study. A physical model of soil mixing has been developed which allows prediction and control of soil mixture total, water
retention, and aeration, porosities. This model is being further tested with various commonly-used components in the greenhouse, nursery, and field. A related study of the water relations of transplanted container soils has shown that these soils are always drier after transplanting into a ground bed than in the same soil in the container under otherwise similar conditions (because of the deeper drainage depth).
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Progress 01/01/76 to 12/30/76
Outputs
The physical and physiological water requirement of selected glasshouse container crops is being determined. Methods of characterizing the critical limits of water stress relative to expansion growth, leaf diffusion resistance, tissue death and other growth processes have been developed and will be used to characterize crop physiological water requirement. A chamber for measuring whole plant photosynthesis and dark respiration is under construction. A weighable lysimeter to measure crop water use is under development. Mathematicaland graphical forms of a simple physical model of bidisperse mixtures were developed and tested and are currently being tested under crop conditions. Thismodel allows the design of a container media having specified physical properties based on plant requirements. The water relations of germinating seeds and tubers is also under study.
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Progress 01/01/75 to 12/30/75
Outputs
Mathematical and graphical forms of a simple physical model of bidisperse container soil mixtures have been developed and are currently being tested with a wide range on components. This model makes it possible to control and optimize container soil water and air. A polydisperse model is currently being developed. Determination of optimum soil physical conditions for various commonly-grown container plants is currently under way. A method of characterizing plant tissue water stress resistance is being developed relative to expansion growth, leaf diffusion resistance, tissue death, and other growth processes. This, combined with the results of a survey of 'typical' water stress regimes, will give some insight into the significance of water stress reduction of growth. This will also be used to select water stress resistant varieties and cultivars. The water relations of germinating seeds and tubers is also under study, there is little information on the energetics
of seed and seedling water relation. This study is being complemented by a study of the physiology of water stress in germinating seeds.
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Progress 01/01/74 to 12/30/74
Outputs
A simple physical model of bidisperse container soil mixtures has been developedfor prediction of mixture total and "aeration" porosities of any combination of the two components (from component bulk volumes and individual porosities). This highly significant advance in the science and practice of container soils makes it possible to prepare container soils physically tailored to exactly match the crop's requirement without the extensive empirical testing presently necessary. This model is being expanded to include the effects of container depth, amendment type, and amendment particle size. Development of methods for determining plant physical requirements is also in progress. Further development and testing of apparatus and techniques for measurement of plant andsoil water status have also been accomplished.
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Progress 01/01/73 to 12/30/73
Outputs
The short duration of this project has allowed primarily only the development and testing of the techniques and apparatus essential for this study. In addition, some preliminary studies of container-grown plant and soil water relations have been carried out. A laboratory thermocouple psychrometer and associated apparatus has been constructed and tested and a field psychrometer ispresently under construction. Welded wire wet loop thermocouples were used to enable both Peltier and wet loop measurements with the same apparatus. This apparatus allows the measurement of plant and soil water potentials (water stress). In addition, a suction plate, pressure plate, air pycnometer, and oxygen microelectrode have been constructed for characterizing soil physical properties. Preliminary studies have included the physical characterization of the critical limits of wilting stress in greenhouse-grown Chrysanthemum morifolium Ramat. and a brief study of the effects of
incorporating an amendmenton the physical properties of a container soil.
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