REDUCING INPUTS, WHILE MAXIMIZING YIELD IN GREENHOUSE VEGETABLE AND ORNAMENTAL CROP PRODUCTION

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: HATCH
• Reporting Frequency: Annual
• Accession No.: 1007085
• Project Start Date: Oct 1, 2015
• Project End Date: Oct 28, 2019
• Program Code: [(N/A)]- (N/A)

Recipient Organization
UNIV OF MINNESOTA
(N/A)
ST PAUL,MN 55108

Performing Department
Horticultural Science

Non Technical Summary
This project has three broad objectives to increase the size, profitability, and long-term viability of the controlled environment agriculture industry: 1) to increase high value controlled environment food production, 2) to reduce inputs in greenhouse food and ornamental production (and outdoor ornamental production), and 3) to increase our understanding of how high temperature affects yield/growth to accelerate breeding/development of high temperature tolerant plants/cultivars. These objectives create economic opportunity for Minnesotans and those in the Upper Midwest, and increase food safety and accessibility, and decrease the inputs required for these crops and the negative environmental impacts.

Animal Health Component

50%

Research Effort Categories

Basic

50%

Applied

50%

Developmental

(N/A)

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
203	2410	1020	80%
102	2410	1020	20%

Knowledge Area
102 - Soil, Plant, Water, Nutrient Relationships; 203 - Plant Biological Efficiency and Abiotic Stresses Affecting Plants;

Subject Of Investigation
2410 - Cross-commodity research--multiple crops;

Field Of Science
1020 - Physiology;

Keywords

greenhouse

nutrition

cold tolerant

photosynthesis

plant defenses

growth regulators

Goals / Objectives
Increasing high value controlled environment food productionReducing inputs in controlled environment crop productionIncreasing our understanding of high temperature effects on plant growthIdentifying cool temperature tolerant, and heat and/or drought tolerant vegetable and ornamentals crops

Project Methods
1) Increasing High-Value Controlled Environment Food Production:Identify edible crops suited for cool temperature greenhouse crop production: Minnesota is uniquely suited for year round greenhouse crop production due to its cooler temperatures, high irradiance and/or lower humidity levels. We will screen species and cultivars/varieties of a species in both a warm temperature (conventional; 15-25C) greenhouse and a cool temperature greenhouse (temperatures ranging from 2-15C).Environmental Effects on Nutritional Value: We will determine the effect of day/night temperature, irradiance and carbon dioxide concentration on growth and nutritional value of selected vegetable, mushroom and fruit crops to maximize yield and nutritional value to compete effectively with imported plant materials. Plants will be moved among growth chambers in the morning and evening to achieve 25 day/night temperatures regimes to quickly assess day/night temperature regime effects on growth and nutritional value. In addition, crops will be grown under a range of photoperiod and irradiance treatments to determine the impact of those on nutritional value. We will focus on vitamins A, B, D and fiber. We will also determine NO3, NH4, P K, Ca, Mg, Fe, B, Cu, and Mn content in leaves and/or fruit utilizing ICP analysis.Identify Optimal Media and Tissue Levels for Greenhouse Vegetables and Fruits Production: A range of experiments will be conducted to determine the optimal fertility conditions for greenhouse vegetables and fruits under both cool temperature (2-15C) and conventional (15-25C) greenhouse crop production. Maximum growth and quality of crops (yield over time, and nutritive value) will be used as a screen to determine optimal media and nutritional levels (including electrical conductivity, pH, NO3, NH4, P K, Ca, Mg, Fe, B, Cu, and Mn).2) Reducing inputs in controlled environment crop productionOptimize Yield, while Minimizing Inputs: A LiCor LI-6400 portable photosynthesis meter to quantify the photosynthetic rates on vegetable, fruit and mushroom crops under a variety of environments (irradiance from 0 to 1200 umol m-2 s-1; temperature from 2 to 40C; CO2 from 100 to 1200 ppm). Photosynthetic rate is directly related to yield.Utilizing Natural Plant Defenses to Reduce Pesticide Use: Greenhouse environments allow for treatment of crops with volatile compounds to elicit desirable plant defense responses. We hypothesize volatile emissions from leaves following infestation with different greenhouse pests differ. In essence, we are exploring whether plants have vocabulary. We will concentrate volatiles (utilizing a air pump pulling air samples past a 'plug' to capture volatiles) and then examine volatile composition using GS-MS from the species infested with different pests (aphids, two spotted red spider mite, thrips, loopers, and whiteflies). Differences in volatile emissions would suggest pest specific response.We will also determine whether infestation of plants with different pests affects egg-laying behavior of beneficial pests differently. Lastly, we will determine reaction time in plants to infestation of different pests - expressed through volatile emissions.Maximizing PGR and Pesticide Efficacy: Environmental conditions when plant growth regulators (PGRs) and pesticides are applied affects their efficacy. We hypothesize fungicide/pesticide efficacy is associated with drying time. To test this, we will infest plants with different pests and place those infested plants in growth chambers with different temperature/humidity levels to have a wide variety of drying times. The same pesticide (and rate) will be applied to all plants. After plant leaves have dried, plants will be placed in the same environment and pest number per leaf will be determined after 7 days to quantify pesticide efficacy. We also hypothesize rewetting foliage that same day, and/or the next two days (without washing pesticide from the leaves) will increase pesticide efficacy. Pesticides will be applied and different rewetting strategies will be employed to determine their impact on the efficacy of pest control. Lastly, we found combining PGRs with different modes of action can increase efficacy. Therefore, we will determine of specific combinations of plant growth regulators (Cycocel, B-Nine, Topflor, A-Rest, Bonzi, Sumagic) can result in synergist responses thus decreasing total PGR needed.Production Strategies to Decrease Pesticides: Applying fungicides/pesticides in 'finishing' greenhouses result in significant chemical and labor costs. Application strategies that focus chemical applications on those plant parts that absorb the chemical at a specific stage in production can reduce total chemical needed and efficacy. We will assess different early application pesticide/fungicide application strategies and their efficacy in pest/disease control as a way to ultimately reduce total pesticide use.3) Understanding high temperature effects on growth and Yield and Identifying New Heat/drought Tolerant Ornamental crops:High temperature Effects on Growth, Photosynthesis and ABA: We hypothesize moderate high temperature exposure (short- and long-term) affects stomatal behavior of heat tolerant, and intolerant cultivars of ornamental/varieties differently. We also hypothesize high temperature tolerance in fruiting is associated with differences in pollen viability. We will characterize the effect of chronic and short-term high temperature exposure on photosynthesis and respiration, and pollen viability of heat tolerant and intolerant plants. We will also determine whether there is an association between high temperature tolerance of flowering and photosynthesis and stomatal behavior, carbohydrate status, abscissic acid (ABA) accumulation and/or guard cell response to ABA. We apply ABA analogs and synthesis inhibitors to heat tolerant and intolerant cultivars/varieties grown under non-stressful (20C) and stressful (35C) temperatures and assess the degree of stomatal closure using the LI-6400 portable photosynthesis meterImportance of Root Respiration on Yield: We hypothesize that a) root zone temperatures play a greater role in carbohydrate depletion that realized and b) that root zone temperatures impact root respiration. We will conduct a series of experiments where root respiration under different temperatures (5-45C) will be determined using a LiCor LI-6400 portable photosynthesis unit utilizing a respiration cuvette we have in hand. The impact of that root respiration on the total carbohydrate status of the plant (determined by also measuring the amount of total photosynthesis occurring on all leaves of a plant) will be calculated to assess the importance of root respiration on yield and growth in containerized systems (vegetables and ornamentals).Identification of Selection Criteria for Selection for Heat Tolerance: Based on research on heat tolerance above, we will develop rapid selection criteria to facilitate selection of heat tolerant plants. Criteria could include stomatal conductance, photosynthetic rate following a specific temperature treatment (i.e. 30 or 35C exposure), and root and/or leaf respiration rate affects. Damage to Photosystems I and/or II will be assessed using impacts on chlorophyll a and/or b content.Identifying Heat and/or Drought Tolerant Ornamentals Crops: We will continue continue work on cactus and succulents to determine optimal environmental conditions for production of these crops including identifying optimal photosynthetic requirements, nutritional requirements, and propagation requirements. We will also assess the cold hardiness of many cacti species under varying levels of winter protection to determine if they can become new Minnesota perennials.

Progress 10/01/15 to 10/28/19

Outputs
Target Audience:Commercial greenhouse flower and vegetable growers. Commercial outdoor flower and ornamental nursery crop growers. Undergraduate and graduate students. General public. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?1) Training occurred at commercial grower facilities to decrease losses and increase yield and crop quality. 2) Training occurred at both commercial and scientific conferences. 3) Training occurred through undergraduate and graduate student research, teaching and extension activities. How have the results been disseminated to communities of interest?Through commercial and scianetific conferences. Through publication in scientific journals articles and book chapters. Through teaching in teh classroom. Through website publication. What do you plan to do during the next reporting period to accomplish the goals?This report represents the final report associated with this project.

Impacts
What was accomplished under these goals? 1) Tomato root respiratory depression and electrolyte leakage occurs between 50-52.5oC,and 55-57oC, respectively, on tomato varieties that vary in above ground heat tolerance. 2) Increased root temperature (above 50oC) decreases leaf photosynthesis in tomato. 3) Pepper varieties vary considerably in photosynthesis and water use attributes and that variation is associated with the indigenous environment of species from which a variety originated. 4) Species with horticulture significance vary in their survival and proliferation on a green roof in cool, dry climates and the major limiting factor in survival is drought. 5) The growth regulator abscissic acid is associated with photosynthteic heat tolerance.

Publications

• Type: Journal Articles Status: Published Year Published: 2019 Citation: Erwin, J., Hussein, T., and Baumler, DJ. 2019. Pepper photosynthesis, stomatal conductance, transpiration and water use efficiency differ with variety, indigenous habitat and species of origin. Hortscience, 54(10):1662-1666.
• Type: Journal Articles Status: Published Year Published: 2019 Citation: Erwin, J., and J. Hensley. 2019. Evaluation of species with horticultural attributes foe green roofs in a cool, dry climate. Hortscience, 54(10):1703-1711.
• Type: Journal Articles Status: Published Year Published: 2019 Citation: Lahijani, M.J.A., M. Kafi, A. Nezami, J. Nabati and J.E. Erwin. 2019. Effect of CO2 enrichment on gas exchange, biochemical traits, and minituber yield in potato (Solanum tuberosum L.) cultivars. Journal of Agricultural Science and Technology, 21(4):883-894.
• Type: Book Chapters Status: Under Review Year Published: 2019 Citation: Erwin, J. 2019. Environmental physiology of ornamental crops. In: Advances in Ornamental Horticulture. Ed. M Reid. Cambridge Press.
• Type: Theses/Dissertations Status: Published Year Published: 2019 Citation: Guenthner, George. 2019. High root temperature: A buried threat to plant growth. MS Thesis. University of Minnesota.

Progress 10/01/17 to 09/30/18

Outputs
Target Audience:Commercial flower and vegetable crop producers Scientists and researchers Undergraduate and graduate college students Consumers Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?1) Training has occurred at commercial grower facilities to increase yield while reducing inputs. 2) Training has occurred at conferences - both commercial and scientific. 3) Training has occurred through graduate student and postdoctoral conducted research, and 4) Training has occurred in the undergraduate student classroom. How have the results been disseminated to communities of interest?Through commercial and scientific conferences, in the classroom, and through published abstracts and journal papers. What do you plan to do during the next reporting period to accomplish the goals?We are develop temperature root respiration response curves to better understand the limits of root respiration of different economically significant crops and survival of those crops in containerized production. We are inoculating media with different microbes in an effort to determine whether inoculation incraeses root heat tolerance. Preliminary data show that it does. Thsi work will also be conducted in hydroponic solutions to determine whether such inoculation can increase vegetable greens yield in greenhouse-produced leafy greens. We are going to further study how root respiration rate is related to plant postharvest performance of seedlings, bedding plants and flowering potted plants. We are going to explore the potential of irradiating plants in an effort to incraese postharvest performance while decreasing pest and diseases and application of pesticides/fungicides to control them.

Impacts
What was accomplished under these goals? 1) We found root temperature and respiration significantly impact leaf photosynthesis and crop yield. As part of that work, we determined the impact of temperature (especially warm temperature >25C) on tomato root respiration rate and showed that root respiration responses were associated with reported heat tolerance or intolerance with respect to yield of tomato varieties. We determined root respiration varies with herbacous crop species and that it is associated with the ease in shipping of plants. Lastly, we developed a new novel technique to measure root respiration utilizing a novel oxygen sensor. Our findings will help to increase containerized food production, reduce inputs, increases our understanding of high temperature impacts on plant growth and will facilitate teh development of new heat tolerant varieties. 2) We found the plant growth regulator benzylaminopurine can be used to facilitate potato plant establishment, and improve yield in the field, and increase minituber production in the lab. In so doing, we can improve production efficiancy and yield while reducing inputs. 3) We showed that irradiance and carbo dioxide levels in tissue culture vessels were substantially below saturating levels for photosynthesis and that increasing either or both dramatically increases photosynthesis. These data rea already being used to increase tissue culture plantlet yield allowing for more rapid, efficiant and economical asexual propagation of plantlets in tissue culture labs.

Publications

• Type: Journal Articles Status: Published Year Published: 2018 Citation: Lahijani, MJA, M Kafi, A Nezami, J Nabati, JE Erwin. 2018. Effect of 6-Benzylaminopurine and abscisic acid on gas exchnge, biochemical traits, and minituber production of two potato cultivars (Solanum tuberosum L.). J Agr Sci and Tech, 20(1):129-139.
• Type: Journal Articles Status: Published Year Published: 2018 Citation: Lahijani, MJA, M Kafi, A Nezami, J Nabati, JE Erwin. 2018. Sprouting, plant establishment, and yield improvement of potato (Solanum tuberosum L.) minituber cultivars by foliar application of benzylaminopurine and abscisic acid. Electronic J Crop Prod., 10(4):75-90. DOI: 10.22069/EJCP.2018.12071.1929
• Type: Journal Articles Status: Published Year Published: 2018 Citation: Lahijani, MJA, M Kafi, A Nezami, J Nabati, MZ Mehrjerdi, S Shahkoomahally. 2018. Variations in assimilation rate, photoassimilate translocation, and cellular fine structure of potato cultivars (Solanum tuberosum L.) exposed to elevated CO2. Plant Phys and Biochem., 130:303-313.
• Type: Conference Papers and Presentations Status: Published Year Published: 2018 Citation: Guenthner, G, and J Erwin. 2018. Temperature effects on root respiration rate of heat tolerant and intolerant tomato varieties. Proc. Amer. Soc. Hort. Sci Annual Conf., 2018.
• Type: Conference Papers and Presentations Status: Published Year Published: 2018 Citation: Guenthner, G, P Kusuma, J Erwin, B Bugbee. 2018. A novel sensor and technique to quantify root respiration. Proc. Amer. Soc. Hort. Sci Annual Conf., 2018.
• Type: Conference Papers and Presentations Status: Published Year Published: 2018 Citation: Guenthner, G, J Erwin. 2018. Variation in root respiration rate among herbaceous ornamental plant species. Proc. Amer. Soc. Hort. Sci Annual Conf., 2018.
• Type: Journal Articles Status: Under Review Year Published: 2018 Citation: Erwin, J, T Hussein, DJ Baumler. Pepper variety photosynthetic rate, stomatal conductance, transpiration and water use efficiency differ with variety, indigenous habitat and species of origin. Hortsci (under review).
• Type: Websites Status: Published Year Published: 2018 Citation: www.plantgrower.org
• Type: Conference Papers and Presentations Status: Published Year Published: 2018 Citation: Erwin, J, and G Guenthner. 2018. Impact of irradiance and carbon dioxide concentration on photosynthetic rate of five ornamental plant species/hybrids grown in tissue culture. Proc. Amer. Soc. Hort. Sci Annual Conf., 2018.
• Type: Conference Papers and Presentations Status: Published Year Published: 2018 Citation: Guenthner, G, J Erwin. 2018. Impact of high root temperature on heat tolerant and intolerant Lycopersicon esculentum variety photosynthetic rate. Proc. Amer. Soc. Hort. Sci Annual Conf., 2018.

Progress 10/01/16 to 09/30/17

Outputs
Target Audience:Scientific Community Ornamental crop and greenhouse edible crop producers Graduate students Undergraduate students Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?This project involved 5 undergraduate students, 1 graduate student, and 1 postdoc in 2017. How have the results been disseminated to communities of interest?National, regional and state conferences for commercial ornamental crop and greenhouse edible crop prducers. Trade and scientific press. Website (www.plantgrower.org). What do you plan to do during the next reporting period to accomplish the goals?Evaluate how roots sensitivity to temperature impacts temperature tolerance in yield in ornamental and vegetable crops. Continue research on plant growth regulator synergy to further reduce chemcial application. Develop a modular LED-battery system to allow for homeowners to produce edible greens in their home. Determine the impact of UV light on mushroom yield. Determine how bacteria and fungi impact root temperature tolerance and disease susceptibility under high temperature conditions which are commonplace in containerized production.

Impacts
What was accomplished under these goals? 1) Increasing high value controlled environment food production: a) Evaluated over 125 different edible leafy greens crops for potential for production in controlled environment greenhouses. 2) Reducing inputs in controlled environment crop production: a) identified the impact of carbon dioxide concentration and irradiance on Swiss chard, spinach amd kale photosynthesis. b) identified optimal spectra for micro LED lights for use in controlled environment agriculture. c) Evaluated whether plant growth regulators can be combined to cause synergistic effects to ultimately reduce total chemical needed. 3) Increasing our understanding of high temperature effects on plant growth. a) Evaluated 33 pepper varieties that differed in species of origin, geographic point of origin, and climate of origin on photosynthetic rate when grown outdoors in containers. b) Evaluated the importance of abscisic acid on stomatal closure of heat tolerant and intolerant varieties of pepper. c) Initiated a project exploring the impact of high temperatures in container media effects on photosynthetic rate and yield. 4) Identifying cool temperature rolerant, and heat and/or drought tolerant vegetable and ornamentals crops: a) Evaluated over 125 edible leafy green crops for performnace in minimally heated greenhouses.

Publications

• Type: Journal Articles Status: Published Year Published: 2017 Citation: Erwin, JE, K Altman and F Esqueda. 2017. Temperature impacts on cactus and succulent development rate. HortTechnology, 27(1): 1-4.
• Type: Journal Articles Status: Published Year Published: 2017 Citation: Erwin, JE and E Gessick. Photosynthetic responses of Swiss chard (Beta vulgaris), kale (Brassoca oleracea and napus pabularia) and spinach (Spinacea oleracea) to irradiance and carbon dioxide. Hortscience, 52(5): 706-712.
• Type: Journal Articles Status: Published Year Published: 2017 Citation: Ahmadi-Lahijani MJ, M Kafi, A Nezami, J Nabita and J Erwin. Effect of 6-benzylaminopurine and abscisic acid on gas exchange, biochemical traits, and minituber production of two potato cultivars (Solanum tuberosum L.), J. Agr. Sci. Tech., 20:129-139.
• Type: Other Status: Published Year Published: 2017 Citation: Safe edible crop production. GPN Magazine, October Issue.
• Type: Websites Status: Published Year Published: 2017 Citation: www.plantgrower.org

Progress 10/01/15 to 09/30/16

Outputs
Target Audience:Scientific community Ornamental crop and greenhouse vegetable producers Graduate students Undergraduate students Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?This project has involved three undergraduate students in conducting research, and one technician. How have the results been disseminated to communities of interest?Results from this work have been presented at a variety of meetings including one international scientific conference, one national commercial greenhouse crop producer conference, one regional conference, and three local meetings/conferences. Aside from industry meetings, two peer reviewed scientific articles were published, two scientific abstracts, two additional scientific papers were submitted for publication, and two book chapters were published. Lastly, we initiated the development of a new website where information is being uploaded (www.northernhorticulture.org). What do you plan to do during the next reporting period to accomplish the goals?Conduct additional work examining the role of abscisic acid sensitivity of guard cells in heat tolerance in Arabidopsis and tomato. This may include starting a project into whether heat intolerant Arabidopsis mutants can be transformed with genes that upregulate abscisic acid synthesis or downregulate abscisic acid sensitivity to increase their heat tolerance. Complete work on identified performance of 170 different vegetable greens crops in conventional greenhouse and low temperature and light greenhouse environments. Complete validation of new LEDs for use in controlled environments. Complete the develop a new mushroom production laboratory and initiate work on the impact on nutrition and environment on specialty mushroom fruiting body induction and yield. Develop a new modular solar energy collection and storage unit that can be used with our new LEDs to grow food in homes and in small-scale greenhouses. Continuing follow up work on how beneficial organisms can be incorporated into media to increase growth or yield of vegetable, cacti and/or succulents to reduce fertilizer requirements. Continue work on how to induce natural plant defenses to reduce pesticide use.

Impacts
What was accomplished under these goals? 1) Increase high value controlled environment food production: a) Determined how 25 different day-night temperature regimes affected the nutritional contant and value (health benefits) of arugula, mustard, spinach, and mizuna. b) Initiated a research program looking at maximizing mushroom yield (specialty) in controlled environments. 2) Reducing inputs in controlled environment crop production: a) We determined how 25 different day-night temperature regimes affected mustard, arugula, spinach, cucumber, strawberry and mizuna development rate and yield (mustard, spinach, arugula and mizuna only). That work also determined how 25 different day-night temperature regimes affected the ability of cucumber, arugula, strawberry, mustard, spinach, and mizuna plant photosynthesis to respond to changes in temperature, light and carbon dioxide. b) Helped develop a new LED lighting technology that can be used to grow plants in controlled environments with reduced electrical use. c) Identified how a plant infested with aphids can communicate with non-infested adjacent plants to turn on their natural plant defenses to reduce pest proliferation. The intent is to develop techniques to turn on natural plant defenses of uninfested plants to limit preventative pesticide needs. d) Identified the difference in plant performance using different commercially available organic fertilizers to identify those fertilizers that result in the maximum benefit with the minimum input. e) Identified the impact of incorporating different beneficial microrganisms into growing media on fertilized and unfertilized basil with teh intent of exploring ways to reduce the amount of fertilizer for crop production while still producing a marketable crop. 3) Increasing our understanding of high temperature effects on plant growth: a) We completed studies comparing heat tolerant and intolerant Arabidopsis, tomato and pepper varieties under periodic heat (36-40C) and non-heat stress (23C). That work identified abscisic acid (ABA) as a plant growth hormone associated with heat tolerance in plants that is expressed through modified stomatal conductance. Work also showed that repeated high temperature exposures are often required for the expression of high temperature intolerance. Follow up work showed altering ABA synthesis can affect heat tolerance in tolerant and intolerant varieties. Work is currently under way to determine whether ABA sensitivity differs between high temperature tolerant and intolerant varieties and mutants. 4) Identifying cool temperature tolerant, and heat and/or drought tolerant vegetable and ornamental crops: a) We measured environmental differences in conventional greenhouse environments versus low-input greenhouses during the winter of 2015-2016. That data was used to manage two greenhouses starting Fall 2016. One hundred seventy different leafy green vegetable crops were identified and are currently being grown in both greenhouses to identify a) which crops require high versus low energy inputs to be successfully grown, b) the potential yield of all crops.

Publications

• Type: Journal Articles Status: Published Year Published: 2016 Citation: Erwin, J, R OConnell, K Altman. 2016. Photoperiod, irradiance, and temperature affect Echinopsis Rose Quartz flowering. HortScience, 51(12):1-4.
• Type: Journal Articles Status: Awaiting Publication Year Published: 2017 Citation: Erwin, JE, K Altman and F Esqueda. 2017. Temperature impacts on cactus and succulent development rate. HortTechnology, 27(1): 1-4.
• Type: Book Chapters Status: Awaiting Publication Year Published: 2016 Citation: Currey, C., D. Kopsell, N. Mattson, R. Lopez and J. Erwin. 2016. Chapter 15  Supplemental and sole-source lighting of leafy greens, herbs, and microgreens. In Lighting Up Profits, Eds. Runkle, E., and R. Lopez, 2nd. Ed., Meister Pub., Willoughby, OH.
• Type: Book Chapters Status: Awaiting Publication Year Published: 2016 Citation: Erwin, J., N. Mattson, and R. Warner. 2016. Chapter 10  Light effects on annual bedding plants. In Lighting Up Profits, Eds. Runkle, E., and R. Lopez, 2nd. Ed., Meister Pub., Willoughby, OH.
• Type: Conference Papers and Presentations Status: Awaiting Publication Year Published: 2016 Citation: Erwin, J. 2016. Temperature and irradiance affects photoperiodic flower induction. ISHS Symposium on Lighting in Controlled Environments, Acrt Hort.
• Type: Conference Papers and Presentations Status: Awaiting Publication Year Published: 2016 Citation: Erwin, J., Carlson, J., L. Perkus, J. Slavin, C. Rosen. 2016. Day/night temperature regime affects photosynthetic responses to irradiance and carbon dioxide, and mineral, vitamin and fiber content of several vegetable crops. ISHS Symposium on Lighting in Controlled Environments. Acta Hort.