Home
 
Research
 
Teachings
 
Services

CRISS Reports

2009:

Field 84: 01/2009-12/2009

Field 85: (Progress Report)

There are important engineering and crop production advantages in growing plants under hypobaric (reduced atmospheric pressure) conditions for extraterrestrial base or spaceflight environments. Advantages include reduced pay load, greater safety because of lower pressure gradients and improved plant growth. The primary objective of this research was to investigate how low pressure (hypobaria) and low oxygen (hypoxia) affect functional phytochemicals and the nutritional quality of 'Red Sails' lettuce (Lactuca sativa L.). Plants were grown under two levels of total gas pressure (reduced or ambient (25 or 101 kPa, respectively)) at three levels of O2 partial pressures (low, medium or ambient (6, 12 or 21 kPa, respectively)). Hypoxia effects on nutritional and functional phytochemicals were more pronounced than hypobaria effects. Regardless of the total pressure, hypoxia, in general, enhanced leaf anthocyanin levels, enhanced total phenolic compounds, enhanced carbohydrate concentration and enhanced free radical scavenging capacity of lettuce but reduced leaf mineral concentration. Hypoxia increased the ethylene production of plants but ethylene accumulation was not the sole reason for enhanced anthocyanin production in plants grown under hypoxia. Our results suggest that low oxygen stress induces the production of protective phytochemicals and the free radical scavenging potential in lettuce, which may in turn enhance the functional value (Rajakaske et al., 2009).

The exploration of space requires the development of Advanced Life Support Systems (ALS) that have the capacity to recycle resources and produce food (Wheeler et al., 2001). Such life support systems will likely combine biotechnology and physicochemical processes for air and water recycling. The biological component will include the use of higher plants for air and water purification, as well as providing food and psychological benefits (NASA, 1988). The National Aeronautics and Space Administration (NASA) has a research and development effort to build such systems as part of the Advanced Life Support System Program (Corey et al., 1997; Goins et al., 2003; Hangartner et al., 2004; Schwartzkopf and Mancinelli, 1991; Wheeler and Martin-Brennen, 2000), for lunar (Ming and Henninger, 1989) and Martian (Corey et al., 2002) agriculture. This is a NASA funded project in collaboration with the Department of Biological and Agricultural Engineering. [He, C., F. T. Davies Jr. and R. E. Lacey. 2009. Ethylene reduces gas exchange and growth of lettuce plants under hypobaric and normal atmospheric conditions. Physiologia Plantarum


Impact

There will not be a human presence in Lunar or Martian habitation without Horticulture. Davies, Dr. Chuanjiu He and Dr. Ron Lacey (Biological and Agricultural Engineering) have been collaborating on NASA-funded research ($908,102) since 2001. There are engineering, safety and cost advantages in growing plants under low pressure conditions. In addition they report that plants do better under low pressure (25 kPa) than earth ambient pressure (101 kPa), in part because low pressure depresses the phytohormone ethylene (which can cause senescence and irregular plant growth), plus dark respiration (at night) slows down, which leads to greater biomass production. This research also has application to controlled crop production systems, sustainable, reduced input production systems and controlled atmospheric (CA) storage systems of horticultural crops. Their research was reported in a 2007 British Broadcasting Corp (BBC)-Science in Action Report and one of their papers made the Oct 2007 cover of Physiologia Plantarum, one of the leading plant biology journals. Invited plenary talks on the NASA supported low pressure research were given at the 50th Annual Meeting of the Canadian Society of Plant Physiologists, the University of Arizona, NCERA-101 Committee on Controlled Environment Technology and Use in Cocoa Beach, Florida, and International Potato Center (CIP) and Peruvian National Agrarian University (UNALM). Further information and pdf files of publications from Davies' research group can be found at http://aggie-horticulture.tamu.edu/faculty/davies/index.html

++++++++++++++++++++++++++++++++++++++++++

Carpio, L.A., F. T. Davies, Jr., T. Fox and C. He. 2009. Arbuscular Mycorrhizal Fungi and Organic Fertilizer Influence Photosynthesis, Root Phosphatase Activity, Nutrition and Growth of Ipomoea Carnea ssp. Fistulosa. Photosynthetica. 47: 1-10. He, C., F. T. Davies Jr. and R. E. Lacey. 2009. Ethylene reduces gas exchange and growth of lettuce plants under hypobaric and normal atmospheric conditions. Physiologia Plantarum. 135: 258-271. He, C., F. T. Davies Jr. and R. E. Lacey. 2009. Hypobaria, hypoxia and light affect gas exchange, and the CO2 compensation and saturation points of lettuce (Lactuca sativa) L. Botany 87(7): 712-721. Rajapakse, N.C., C. He, L. Cisneros-Zevallos, and F. T. Davies Jr. 2009. Hypobaria and hypoxia affects growth and phytochemical contents of lettuce. Scientia Horticulturae 122: 171-178. He, Chuanjiu, F.T. Davies, Jr. and R.E. Lacey. 2009. "Hypobaria, Hypoxia and Light Affect Gas Exchange, and the CO2 Compensation and Saturation Points of Lettuce Plants". NCERA-101 Committee on Controlled Environment Technology and Use Annual Meeting. April 4 - 8, 2009 Park City, Utah. Chow, A. and A. Chau, P. Krauter, C. Bográn, F. Davies and K. M. Heinz. 2009. Manipulating fertilizer input for container production of woody and herbaceous ornamentals: a viable approach to pest management? Greenhouse Grower. Aug. 2009. http://www.greenhousegrower.com/production/?storyid=2419# He, C., F. T. Davies Jr. and R. E. Lacey. 2009. Hypobaria, hypoxia and light affect gas exchange, and the CO2 compensation and saturation points of lettuce (Lactuca sativa). HortScience.

 

2008:

Field 84: 01/2008-12/2008

Field 85: (Progress Report)

There are important engineering and crop production advantages in growing plants under hypobaric (reduced atmospheric pressure) conditions for extraterrestrial base or spaceflight environments. Advantages include reduced pay load, greater safety because of lower pressure gradients and improved plant growth.  Elevated levels of ethylene occur in controlled environment agriculture and in spaceflight environments, leading to adverse plant growth and sterility. The objectives of this research were to characterize the influence of ethylene on carbon dioxide (CO2) assimilation (CA), dark-period respiration (DPR) and growth of lettuce (Lactuca sativa L. cv. Buttercrunch) under ambient and low total pressure conditions. Lettuce plants were grown under variable total gas pressures of 25 kPa (hypobaric) and 101 kPa (ambient) pressure. Endogenously produced ethylene accumulated and reduced CA, DPR and plant growth of ambient and hypobaric plants. There was a negative linear correlation between increasing ethylene concentrations [from 0 to around 1000 nmol mol-1 (ppb)] on CA, DPR and growth of ambient and hypobaric plants. Declines in CA and DPR occurred with both exogenous and endogenous ethylene treatments. CA was more sensitive to increasing ethylene concentration than DPR. There was a direct, negative effect of increasing ethylene concentration reducing gas exchange, as well as an indirect ethylene effect on leaf epinasty, which reduced light capture and CA. While the CA was comparable, there was a lower DPR in hypobaric than ambient pressure plants -- independent of ethylene and under non-limiting CO2 levels (100 Pa pCO2, nearly 3-fold that in normal air). This research shows that lettuce can be grown under hypobaria (@ 25% of normal earth ambient total pressure), however, hypobaria caused no significant reduction of endogenous ethylene production.

                        The exploration of space requires the development of Advanced Life Support Systems (ALS) that have the capacity to recycle resources and produce food (Wheeler et al., 2001). Such life support systems will likely combine biotechnology and physicochemical processes for air and water recycling.  The biological component will include the use of higher plants for air and water purification, as well as providing food and psychological benefits (NASA, 1988). The National Aeronautics and Space Administration (NASA) has a research and development effort to build such systems as part of the Advanced Life Support System Program (Corey et al., 1997; Goins et al., 2003; Hangartner et al., 2004; Schwartzkopf and Mancinelli, 1991; Wheeler and Martin-Brennen, 2000), for lunar (Ming and Henninger, 1989) and Martian (Corey et al., 2002) agriculture. This is a NASA funded project in collaboration with the Department of Biological and Agricultural Engineering. [He, C.,  F. T. Davies Jr. and R. E. Lacey. 2009. Ethylene reduces gas exchange and growth of lettuce plants under hypobaric and normal atmospheric conditions. Physiologia Plantarum. In press.]            

Impact

There will not be a human presence in Lunar or Martian habitation without Horticulture. Davies, Dr. Chuanjiu He and Dr. Ron Lacey (Biological and Agricultural Engineering) have been collaborating on NASA-funded research ($908,102) since 2001. There are engineering, safety and cost advantages in growing plants under low pressure conditions. In addition they report that plants do better under low pressure (25 kPa) than earth ambient pressure (101 kPa), in part because low pressure depresses the phytohormone ethylene (which can cause senescence and irregular plant growth), plus dark respiration (at night) slows down, which leads to greater biomass production. This research also has application to controlled crop production systems, sustainable, reduced input production systems and controlled atmospheric (CA) storage systems of horticultural crops. Their research was reported in a 2007 British Broadcasting Corp (BBC)-Science in Action Report and one of their papers made the Oct 2007 cover of Physiologia Plantarum, one of the leading plant biology journals. Invited plenary talks on the NASA supported low pressure research were given at the 50th Annual Meeting of the Canadian Society of Plant Physiologists, the University of Arizona, NCERA-101 Committee on Controlled Environment Technology and Use in Cocoa Beach, Florida, and International Potato Center (CIP) and Peruvian National Agrarian University (UNALM). Further information and pdf files of publications from Davies’ research group can be found at http://aggie-horticulture.tamu.edu/faculty/davies/index.html


++++++++++++++++++++++++++++++++++++++++++


Alarcon, A., F. T. Davies Jr., R. L. Autenrieth and D. A. Zuberer. 2008. Arbuscular
Mycorrhiza and Petroleum-Degrading Microorganisms Enhance Phytoremediation of Petroleum-Contaminated Soil. International Journal of Phytoremediation. 10(4): 251-263.

Davies, F.T. Jr. and A. Alarcon. 2008. Enhancing Phytoremediation of Heavy Metals with Arbuscular Mycorrhizal Fungi. In: A. Alarcón and R. Ferrera-Cerrato (Eds.), Bioremediation of Soils and Water Contaminated by Organic and Inorganic Compounds. Mexico City: Mundi-Prensa S.A. de C.V. (Book Chapter).

Estrada-Luna, A. A. and F. T. Davies Jr. 2008. Nutrient status and growth of micropropagated prickly-pear cactus (Opuntia albicarpa Scheinvar cv. “Reyna”) plantlets colonized with three-selected endomycorrhiza isolates. In: Arbuscular Mycorrhizae in Arid and Semi-Arid Ecosystems. N. Manuel Montaño Arias, S. Lucía Camargo Ricalde, R. García Sánchez and A. Monroy Ata (Eds.) Mundi-Prensa México, S. A. de C. V. pp. 33-44.  (Book Chapter)

 

He, Chuanjiu, F.T. Davies, Jr. and R.E. Lacey. Hypobaria, Hypoxia and Ethylene Influence Gas Exchange and Growth of Lettuce Plants.  2008 International Meeting on Controlled Environment Agriculture. Mar 8-12, 2008, Cocoa Beach, Florida. p. 28. (Symposium Proceedings)

 

Davies, F.T., Jr. 2008. Invited & sponsored presentation: “Challenges in NASA Low-Pressure Crop Production Systems -- Separating the Effects of Hypobaria and Hypoxia on Lettuce.”  Canadian Society of Plant Physiology – 50th Anniversary Meeting. Ottawa, Ontario, Canada. June 2008.  (Symposium Proceedings)

 

Spiers, J.D.,  F.T. Davies, Jr., C. He, K. M. Heinz, C. E. Bográn, and Terri W. Starman. 2008.
Do Insecticides Affect Plant Growth and Development? – (Research tests foliar insecticides to determine whether applications affect development in gerbera daisies). Greenhouse Grower. Feb. Vol 2. http://www.greenhousegrower.com/grower_tools/200802_insecticides.html   

Amaya-Carpio, L., F. T. Davies, Jr., T. Fox, and C. He. 2008. Arbuscular Mycorrhizal Fungi and
Organic Fertilizer Influence Photosynthesis, Growth, Nutrient Uptake and Root Phosphatase Activity of  Ipomoea Carnea subsp. Fistulosa. SNA Research Conference Proceedings. 53: In press.

He, C., F. T. Davies Jr. and R. E. Lacey. 2008. Ethylene Reduces Gas Exchange and Growth
of Lettuce Plants Under Hypobaric and Normal Atmospheric Conditions HortScience.
43(4): 124.

Davies, F.T., M. Lamberts, T. Ferriss, G. Fitzpatrick, S. L. Steinberg, K. Panter, J. Cole, M. Neff and R.Talke. 2008. Opportunities for Industry, the Public, and the Profession of Horticulture with the ASHS-Certified Horticulturist (ASHS-CH) Program. HortScience 43(4):

 

Davies, Jr., F.T. 2008. Opportunities Down Under – How Mycorrhizal Fungi Can Benefit Nursery Propagation and Production Systems Combined Proceedings of International Plant Propagators’ Society.  58: in press

2007:

Field 84: 01/2007-12/2007

Field 85: (Progress Report)

There are important engineering and crop production advantages in growing plants under hypobaric (reduced atmospheric pressure) conditions for extraterrestrial base or spaceflight environments. Advantages include reduced pay load, greater safety because of lower pressure gradients and improved plant growth.  Objectives of this research were to determine the influence of hypobaria and the partial pressure of oxygen (pO2) on carbon dioxide (CO2) assimilation, dark respiration and growth of lettuce (Lactuca sativa L. cv. Buttercrunch). Lettuce plants were grown under variable total gas pressures [25 and 101 kPa (ambient)] at 6, 12 or 21 kPa pO2. While plant growth was comparable between ambient and low pressure lettuce during the 10-day study, growth was lower at 6 kPa pO2 than 12 or 21 kPa pO2. The specific leaf area (SLA) of 6 kPa pO2 plants was lower than 12 or 21 kPa pO2 lettuce, indicating thicker leaves associated with plant stress. Greater carbon partitioning into above ground dry mass (higher leaf/root ratio) occurred with 6 kPa pO2 plants.  Leaf chlorophyll levels were greater at low than ambient pressure. Relative water content (RWC) was the same among treatments, indicating that hypobaria and pO2 did not adversely affect plant water relations. There was about a 10% lower CO2 assimilation (net photosynthesis) and 25% lower dark respiration rate in low (25/12 kPa pO2) than ambient (101/21 kPa pO2) pressure plants. The ratio of CO2 assimilation/dark respiration was higher at low than ambient total pressure, particularly at 6 kPa pO2 ¾ indicating a greater efficiency of CO2 assimilation/dark respiration with low pressure plants. Hypobaric plants were more resistant to hypoxic conditions (6 kPa pO2) that reduced gas exchange and plant growth.  The considerably lower dark respiration rates (reduced consumption of metabolites) could lead to greater plant growth (biomass production) under low pressure than under ambient conditions during longer crop production cycles.  

            The exploration of space requires the development of Advanced Life Support Systems (ALS) that have the capacity to recycle resources and produce food (Wheeler et al., 2001). Such life support systems will likely combine biotechnology and physicochemical processes for air and water recycling.  The biological component will include the use of higher plants for air and water purification, as well as providing food and psychological benefits (NASA, 1988). The National Aeronautics and Space Administration (NASA) has a research and development effort to build such systems as part of the Advanced Life Support System Program (Corey et al., 1997; Goins et al., 2003; Hangartner et al., 2004; Schwartzkopf and Mancinelli, 1991; Wheeler and Martin-Brennen, 2000), for lunar (Ming and Henninger, 1989) and Martian (Corey et al., 2002) agriculture. This is a NASA funded project in collaboration with the Department of Biological and Agricultural Engineering. [He, C.,  F. T. Davies Jr. and R. E. Lacey. 2007. Separating the effects of hypobaria and hypoxia on lettuce: growth and gas exchange. Physiologia Plantarum 131: 226–240.]
Impact

There will not be a human presence in Lunar or Martian habitation without Horticulture. Davies, Dr. Chuanjiu He and Dr. Ron Lacey (Biological and Agricultural Engineering) have been collaborating on NASA-funded research ($808,102) since 2001. There are engineering, safety and cost advantages in growing plants under low pressure conditions. In addition they report that plants do better under low pressure (25 kPa) than earth ambient pressure (101 kPa), in part because low pressure depresses the phytohormone ethylene (which can cause senescence and irregular plant growth), plus dark respiration (at night) slows down, which leads to greater biomass production. This research also has application to controlled crop production systems, sustainable, reduced input production systems and controlled atmospheric (CA) storage systems of horticultural crops. Their research was reported in a 2007 British Broadcasting Corp (BBC)-Science in Action Report and one of their papers made the Oct 2007 cover of Physiologia Plantarum, one of the leading plant biology journals.  A Visiting Professor, Dr. Nihal Rajapaske, on sabbatical leave from Clemson University conducted research in 2007 in Davies’ Lab on “Effect of oxygen concentration in the growing environment on phytochemical composition and functional quality of lettuce plants”, in collaboration with Drs. Luis Cisneros, Ron Lacey and Chuanjiu He. Further information and pdf files of publications from Davies’ research group can be found at http://aggie-horticulture.tamu.edu/faculty/davies/index.html



2006:
Field 84: 01/2006-12/2006

Field 85: (Progress Report)

The exploration of space requires the development of Advanced Life Support Systems (ALS) that have the capacity to recycle resources and produce food. Such life support systems will likely combine biotechnology and physicochemical processes for air and water recycling.  The biological component will include the use of higher plants for air and water purification, as well as providing food and psychological benefits. The National Aeronautics and Space Administration (NASA) has a research and development effort to build such systems as part of the Advanced Life Support System Program for lunar and Martian agriculture.

Plants can respond adversely even to very low ethylene levels. Elevated levels of ethylene have been reported in enclosed environments and implicated in microgravity — spaceflight experiments. Wheat grew poorly in an ambient (101 kPa) chamber with ethylene at 100–200 nmol mol-1 (ppb). Wheat plants grew normally when the ethylene was removed by an activated alumina column. Chronic exposure to ethylene levels of 50 to 100 nmol mol-1 reduced growth of lettuce and Easter lilies. On the Russian space station, Mir, ethylene ranged from 1000 to 1700 nmol mol-1, about 1000x to 1700x greater than ethylene in terrestrial, open field agricultural conditions, leading to abnormal growth and sterility. Ethylene levels are maintained around 50 nmol mol-1 on the international space station (ISS), but even these levels can have adverse effects on plant growth and sterility. Under hypoxia (low oxygen) one would expect that higher (rather than lower) levels of ethylene occur, as is common during anaerobic conditions when plants experience flooding. It would be profoundly interesting to characterize ethylene levels and other volatile organic compounds, particularly with the expected differences in gas diffusion rates at low pressure. Hence, the objectives of this research were to characterize the influence of hypobaria on optimal growth, plant gas exchange and ethylene evolution of lettuce (Lactuca sativa cv. Buttercrunch). 

This research shows that lettuce can be successfully grown in a hypobaric environment. Lettuce has high potential of being included in NASA’s Advanced Life Support System. Lettuce plants grown under low total pressure (50 kPa) had comparable growth to plants grown under ambient pressure conditions in a series of short-term experiments lasting up to six days. There was also a tendency for tip burn under ambient pressure, possibly due to higher levels of ethylene and potential differences in calcium mobility. Tip burn also increased under high light (600 vs. 300 mmol m-2s-1) and high CO2 (600 Pa vs. 100 Pa). Tip burn of ambient pressure plants was observed two days earlier (day 4) under high light than low light (day 6). Under ambient pressure there were higher CO2 assimilation rates and dark respiration rates (higher night consumption of metabolites) compared to low pressure.


Impact

There are important engineering and crop production advantages in growing plants under hypobaric (reduced atmospheric pressure) conditions for extraterrestrial base or spaceflight environments. Advantages include reduced pay load, greater safety because of lower pressure gradients and improved plant growth.  Elevated levels of the plant hormone, ethylene, can occur in enclosed crop production systems and in space-flight environments¾leading to adverse plant growth and sterility. Objectives of this research were to characterize the influence of hypobaria on growth and ethylene evolution of lettuce (Lactuca sativa L. cv. Buttercrunch). Growth was comparable in lettuce grown under 50 and 101 kPa (ambient) total gas pressures in a series of short-term experiments lasting up to six days. However, tip burn occurred under ambient, but not low pressure. Tip burn also increased under high light (600 compared to 300 mmol m-2s-1) and high pCO2 (600 Pa compared to 100 Pa). Under ambient pressure, there were higher CO2 assimilation rates and considerably greater dark respiration rates (higher night consumption of metabolites) compared to low pressure. This could lead to greater biomass production of plants grown in low pressure plants over longer crop production cycles. Ethylene evolution was lower under low than ambient pressure.



2005:
Field 84: 01/2005-12/2005

Field 85: (Progress Report)

Gerbera (Gerbera jamesonii) is an economically important greenhouse crop produced and sold for cut flowers, potted plants, and bedding plants. A wide variety of insecticides from different insecticide classes with diverse modes of action are frequently used on gerbera to reduce the occurrence of insecticide resistance. Often there is near zero tolerance for insect pests on ornamental crops, hence, insecticides are applied at frequent intervals to prevent insect infestation. Due to increasing concern over the use of toxic chemicals in greenhouse production, reduced-risk insecticides are used because they are less toxic to workers, have short residual properties, and have minimal adverse environmental impact. These insecticides also may have a narrower spectrum of pest activity and require frequent applications for sufficient pest control. Insecticides are evaluated for visible phytotoxicity and their impact on non-target organisms during their registration, but impacts on plant physiology and plant growth and development are not often tested.

Studies on the effects of insecticides on gas exchange have been conducted primarily on agronomic crops with varying results. Many of these studies were conducted with insecticides that are no longer commercially applied or that are not applicable to ornamental greenhouse crops. While it is generally thought that insecticides can adversely affect plants, few studies have looked at insecticidal effects on host plant physiology, in addition to plant growth and development.

The most obvious effects were observed with the 4X Triact 70 (neem oil) and Orthene TT&O (acephate) treatments. The 4X neem oil plants had significantly reduced photosynthesis and stomatal conductance - which resulted in reduced shoot and total aboveground DM, reduced flower production, later flower development, thicker leaves (lower SLA), reduced leaf area, and a reduction in plant quality. The 4X acephate plants had poorest marketablity due to severe phytotoxicity, i.e. leaf burn, which contributed to lower shoot DM and total aboveground DM. The highest quality were the plants treated with 1X or 4X Conserve SC (spinosad) or Avid 0.15 EC (abamectin). These plants experienced no negative effects from insecticidal applications and were not infested with the natural infestation of thrips that damaged control and Talstar Flowable (bifenthrin) treated plants.

Neem oil, which is commonly used as both a fungicide as well as an insecticide in potted gerbera production, also acted as a growth retardant in this study. It is common practice to apply growth retardants in the production of many ornamental crops to reduce internode elongation and induce compact growth. Plants treated with neem oil at the recommended concentration had reduced plant growth and development due to reduced net photosynthesis and stomatal conductance. Neem oil plants, particularly at the 4x concentration, were not rated as marketable - due to excessively stunted growth, unwanted residue, and reduced flower quality. However, when used sparingly, neem oil may also be useful for reducing elongation in gerbera, in addition to its insect and pathogen control.
Impact

The commonly used insecticides Avid 0.15 EC, Talstar Nursery Flowable, and Conserve SC did not alter plant gas exchange, and were not detrimental to plant growth and development of gerberas—even when applied at 4X the recommended rate. Orthene Turf, Tree & Ornamental Spray 97, when applied at recommended rates, did not adversely affect plant growth and development or plant gas exchange of gerbera. However, Orthene was phytotoxic to gerbera when applied at rates above label recommendations. Triact 70 (neem oil) significantly reduced plant gas exchange, plant growth and development, and flower production, with greatest reductions occurring at the highest concentration. Insect infestations on some of the control plants and Talstar - treated plants negatively impacted their commercially acceptable value, demonstrating the importance of insect pest control. However, when using insecticides, caution and judicious use should be exercised in order to prevent plant damage, minimize development of pest resistance, and reduce production costs.



2004:
Current dogma has been that arbuscular mycorrhizal fungi (AMF) are more beneficial for organic slow release fertilizer (OSRF) than inorganic controlled-release fertilizer (ICRF). To the contrary, our research shows that AMF enhancement is better with ICRF than OSRF under stressful, high temperature production conditions. This research determined the effects of two commercial AMF inocula, OSRF and ICRF on plant growth, marketability and leachate of container-grown Ipomoea carnea N. von Jacquin subsp. fistulosa (K. Von Martinus ex J. Choisy) D. Austin (bush morning glory) grown outdoors under high temperature summer conditions (maximum container media temperature averaged 44.8 °C). Uniform rooted liners were planted into 7.6 liter pots containing a pasteurized substrate [pine bark and sand (3:1, by volume)]. The AMF treatment consisted of BioterraPLUS and MycorisePro and a noninoculated control (NonAMF). Fertilizer treatments included OSRF [Nitrell: 5-3-4 (5N-1.3P-3.3K)] and ICRF [Osmocote: 18-7-10 (18N-3.0P-8.3K)]. OSRF was tested at three rates: 8.3, 11.9 and 16.6 kg.m-3, which were respectively, 70%, 100% and 140% of manufacturer’s recommended rate, while ICRF was tested at two rates: 3.6 and 7.1 kg?m-3 which were, respectively, 50% and 100% of manufacturer’s recommended rate. The P levels were equivalent between 70% and 140% OSRF and, respectively, 50% and 100% ICRF. Greatest growth [leaf, shoot, flower bud and flower number, root, leaf, shoot and total plant dry mass (DM), growth index, leaf area], N, P and K uptake, leaf chlorophyll, and plant marketability occurred with BioterraPLUS plants at 50% and 100% ICRF rate and MycorisePro at the 100% ICRF rate. Greater plant growth occurred with increasing fertility levels; however, plants at the 140% OSRF (same P level as 100% inorganic SRF) had poorest growth, in part due to high temperature. While AMF enhanced growth of plants with OSRF at all concentrations, better growth and marketability occurred with ICRF than OSRF plants inoculated with AMF. AMF plants at the 50% ICRF had comparable or better growth, higher N, P and K and marketability than NonAMF plants at either 100% OSRF or ICRF. AMF were able to survive under high temperature and colonize plants grown from low to high fertility conditions. AMF inoculation had minimal effect on container leachate [pH and electrical conductivity (EC)]. However, the larger-sized AMF plants at 100% ICRF rate had greater total leaf tissue N, P and K, suggesting greater nutrient utilization ? thus reduced potential risk for leachate runoff.
Impact

To comply with these environmental regulations the nursery and greenhouse industries have developed best management practices (BMPs), such as more efficient fertilization systems, including inorganic controlled-release (ICRF) and organic slow-release fertilizer (OSRF) usage, reducing irrigation water volume and subsequent nutrient leaching, and capturing and treating water runoff. One of the most important challenges facing the nursery and greenhouse industries is the incorporation of practices into production systems that reduce pesticide and fertilizer usage, without reducing plant quality and marketability. Beneficial microorganisms include arbuscular mycorrhizal fungi (AMF), which establish symbiotic associations with roots of most nursery crops. High container temperature is a frequent summer problem in Southern U.S. nursery production systems, directly affecting release of nutrients from ICRF, and indirectly from OSRF, which are influenced by fungal and bacterial microbial activity.

Plants inoculated with AMF at the recommended rate (100%) of inorganic SRF had the best growth response. This work is of particular importance to commercial nurseries and greenhouse production since ICRF are much more commonly used than OSRF. Hence, lower fertilization for AMF plants could minimize leaching and runoff of fertilizer leachate. While AMF had little effect on pH or EC leachates, AMF plants were larger than NonAMF plants and subsequently absorbed a greater total amount of ions, which could potentially minimize leaching and runoff of fertilizer nutrients.



2003:
Elevated levels of ethylene occur in enclosed crop production systems and in spaceflight environments?leading to adverse plant growth and sterility. There are engineering advantages in growing plants at hypobaric (reduced atmospheric pressure) conditions in biomass production for extraterrestrial base or spaceflight environments. Objectives of this research were to characterize the influence of hypobaria on growth and ethylene evolution of lettuce (Lactuca sativa) and wheat (Triticum aestivum). Plants were grown under variable total gas pressures [from 30 to 101 kPa (ambient)]. In one study, lettuce and wheat were direct seeded, germinated and grown in the same chambers for 28 d at 50 or 101 kPa. Hypobaria increased plant growth and did not alter germination rate. During a 10-day study, 28 d-old lettuce and 40 d-old wheat seedlings were transplanted together in the same low and ambient pressure chambers; ethylene accumulated in the chambers, but the rate of production by both lettuce and wheat was reduced more than 65 % under 30 kPa compared with ambient pressure (101 kPa). Low O2 concentrations [partial pressure of O2 (pO2) = 6.2 kPa] inhibited ethylene production by lettuce under both low (30 kPa) and ambient pressure, whereas ethylene production by wheat was inhibited at low pressure but not low O2 concentration. There was a negative linear correlation between increasing ethylene concentration and decreasing chlorophyll content of lettuce and wheat. Lettuce had higher production of ethylene and showed greater sensitivity to ethylene than wheat. The hypobaric effect on reduced ethylene production was greater than that of just hypoxia (low oxygen).
Impact

The exploration of space will require the development of Advanced Life Support Systems (ALS) that will have the capacity to recycle resources and produce food. The biological component will include the use of higher plants for air and water purification, as well as providing food and psychological benefits.

Important environmental variables that have received little research effort in relation to an Advanced Life Support System are: (i) total atmospheric gas pressure, (ii) high CO2 partial pressure, up to 70 Pa or higher, greatly in excess of the range currently studied by researchers interested in global change, (iii) wide differences in humidity and (iv) effects of trace gases - including ethylene under low pressure conditions. Hence, the objectives of this research were to characterize the influence of hypobaric conditions on growth and ethylene evolution of lettuce (Lactuca sativa) and wheat (Triticum aestivum).

To our knowledge, this is the first report that hypobaric environments per se reduce ethylene evolution of lettuce and wheat, and that lettuce is more sensitive to ethylene than wheat in sealed microenvironments. Hypobaria increased plant growth and did not alter germination rate. This research shows that plants can be successfully grown at hypobaric (as low as 30 kPa total gas pressure) and hypoxic (pO2 = 6.2 kPa O2) environments. Hypobaric conditions subsequently reduced the adverse effect of ethylene on plant growth. We found that the hypobaric (low pressure) effect on ethylene production was greater than that of just hypoxia (low oxygen).


2002:
Little is known about the role of arbuscular mycorrhiza fungi (AM) on physiological changes of micropropagated plantlets during acclimatization and post-acclimatization. Using chile ancho pepper (Capsicum annuum L. cv. San Luis), measurements were made of water relations, gas exchange, abscisic acid (ABA), plantlet growth and AM development. Plantlets had low photosynthetic rates (A) and poor initial growth during acclimatization. Relative water content (RWC) decreased during the first days after transfer from tissue culture containers to ex vitro conditions. Consequently, transpiration rates (E) and stomatal conductance (gs) declined, confirming that in vitro formed stomata were functional and able to respond ex vitro to partial desiccation — thus avoiding excessive leaf dehydration and plant death. Colonized plantlets had lower leaf ABA and higher RWC than NonAM plantlets during peak plant dehydration — and a higher A and gs as early as days 5 and 7. During post-acclimatization, A increased in all plantlets; however, more dramatic changes occurred with AM plantlets. Within 48 days, AM plantlets had greater E, A, leaf chlorophyll, N, P and K, leaf dry biomass and leaf area, fruit production and carbon allocation compared with NonAM plantlets. Rapid AM colonization enhanced physiological adjustments, which helped plantlets recover rapidly during acclimatization and obtain greater growth during post-acclimatization.
Impact

With many species, use of micropropagation is limited because of poor plantlet survival rates during acclimatization, which is the transition from in vitro to ex vitro conditions. In commercial micropropagation systems, plant losses of 10 to 40% and higher can occur. Some micropropagated plantlets may lack functional roots, are photomixotrophic and typically have leaves with low photosynthetic rates that impede growth. Transpiration rates are considerably higher in micropropagated plantlets than in vivo grown plants because of the poor stomatal control and the abnormally high cuticular water loss, which cause senescence and death of leaves and plantlets.
Acclimatization is critical because these abnormalities must be corrected to ensure survival and continued normal plant growth. Chile pepper is an important vegetable crop that is cultivated worldwide. Chile Ancho 'San Luis' is highly mycorrhiza dependent and thus a good potential model system for studying AM induced physiological effects during acclimatization. This research was conducted with a mixed isolate of Glomus spp. from Mexico (ZAC-19) that enhances drought resistance and nutrient uptake of chile ancho seedling peppers (Davies et al. 2000, 2001). Our research shows that mycorrhizal can benefit Chile Ancho water relations, gas exchange, reduce ABA, and increase growth of the micropropagated plantlets during acclimatization and post-acclimatization.


2001:
Chromium (Cr) is a heavy metal risk to human health, and a contaminant found in agricultural soils and industrial sites. Phytoremediation, which relies on phytoextraction of Cr with biological organisms, is an important alternative to costly physical and chemical methods of treating contaminated sites. The ability of the arbuscular mycorrhizal fungus (AM), Glomus intraradices, to enhance Cr uptake and plant tolerance was tested on the growth and gas exchange of sunflower (Helianthus annuus L.). Mycorrhizal-colonized (AM) and non-inoculated (Non-AM) sunflower plants were subjected to two Cr species [trivalent cation (Cr3+) {Cr(III)}, and divalent dichromate anion (Cr2O7--) {Cr(VI)}]. Both Cr species depressed plant growth, decreased net photosynthesis (A) and increased the vapor pressure difference; however, Cr(VI) was more toxic. Chromium accumulation was greatest in roots, intermediate in stems and leaves, and lowest in flowers. Greater Cr accumulation occurred with Cr(VI) than Cr(III). AMF enhanced the ability of sunflower plants to tolerate and hyperaccumulate Cr. At higher Cr levels greater mycorrhizal dependency occurred, as indicated by proportionally greater growth, higher A and reduced visual symptoms of stress, compared to Non-AM plants. AM plants had greater Cr-accumulating ability than Non-AM plants at the highest concentrations of Cr(III) and Cr(VI). Arbuscules, which play an important role in mineral ion exchange in root cortical cells, had the greatest sensitivity to Cr toxicity.
Impact

Heavy metals are one of the main sources of environmental pollution. Pytoremediation utilizes biological organisms for phytoextraction or removal of plant biomass containing more concentrated levels of heavy metals from polluted soils. Pytoremediation is an alternative to conventional physical and chemical methods of treating contaminated soils. Chromium (Cr) is a heavy metal risk to human health, and a contaminant found in agricultural soils and industrial sites. Phytoremediation is an important alternative to costly physical and chemical methods of treating contaminated sites. The ability of the arbuscular mycorrhizal fungus (AM), Glomus intraradices, to enhance Cr uptake and plant tolerance was tested on the growth and gas exchange of sunflower (Helianthus annuus L.). AM enhanced plant accumulation and tolerance to Cr. Under lower phosphorus conditions [to aid Cr phytoextraction] AM plants had greater vigor, greater photosynthesis and less visible Cr stress). This led to higher biomass and subsequent greater phytoextraction of Cr. Since most metal-accumulating wild plants are relatively small in size and have slow growth rates, their potential for phytoextraction is limited. Optimum plant-mycorrhizal systems for phytoextraction of Cr should not only be able to tolerate and accumulate high levels of Cr in harvestable parts, but also have a rapid growth and potential to produce high biomass in the field. Hence, the high biomass, rapid-growing sunflower-Glomus association might be an excellent candidate for phytoextraction when transplanted to the field.


2000:
New nursery production systems are being developed that emphasize the use of slow-release fertilizers, minimize the use of pesticides and soluble herbicides, and more efficiently utilize water. Research was conducted to demonstrate that mycorrhiza can survive in a commercial nursery container production system, and enhance plant productivity. Four species were used as host plants [Nandina domestica ‘Moon Bay’, Loropetalum chinense variety Rubrum ‘Hinepurpleleaf’ Plumb delight®, Salvia gregii, and Photinia fraseri]. Plants were inoculated with arbuscular mycorrhizal fungi, Glomus intraradices, and grown in a commercial nursery in Texas. For the first 5.5 months, plants were grown in #1 cans containing either 3 kg cu m or 4.2 kg cu m 24N-4P205-8K20. For the final 6.5 months of the study, plants were in larger containers, all of which contained 4.2 kg cu m 24N-4P2O5-8K2O. The commercial inoculum of Glomus intraradices only enhanced growth of N. domestica. The shoot dry mass of mycorrhizal N. domestica plants at 3 kg cu m was the same as non-colonized plants at the higher fertility level of 4.2 cu m. Intraradical hyphae development and colonization (total arbuscules, vesicles/endospores, hyphae) of L. chinense, N. domestica, and S. gregii increased at the higher fertility levels. S. gregii had the greatest mycorrhizal development and a 216% increase in hyphae development and colonization at the higher fertility level.
 

If you use any of the visual or written materials, please give credit to the source.