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United States Department of Agriculture

Agricultural Research Service

2009 Annual Report

1a.Objectives (from AD-416)
Identify effects of atmospheric CO2, solar radiation, temperature and/or soil moisture on putative phytonutrients in crops; assess implications of environmental stress, weather, and global change on crop nutritional value; develop improved methods to measure the content of phytonutrients and their breakdown or metabolic products.

1b.Approach (from AD-416)
Interactions between atmospheric CO2 and other environmental parameters will be investigated in controlled environments (growth chambers and greenhouses), raising crops to seed while regulating and monitoring atmospheric CO2, temperature, soil moisture and nutrition, and photosynthetically- as well as photomorphogenetically-active radiation. Growth chambers will simulate natural conditions. In addition, crops will be raised in the field; environmental conditions at various developmental stages will monitored and compared to those in controlled environments. In some cases, atmospheric CO2 will be regulated in the field (FACE, Free-Air CO2 Enrichment). Work will concentrate on soybeans, rice and peanuts. Seeds will be harvested and analyzed by HPLC for important biologically-active constituents, such as flavonoids, tocopherols, tocotrienols, sterols, saponins, and/or phylloquinone. Effects of environment on biosynthetic pathways will be evaluated.

3.Progress Report
Previous observations indicated that drought treatments were not as effective in changing soybean seed tocopherol and isoflavone concentrations when studies were conducted in controlled environment chambers compared to drought studies in greenhouse or field conditions. Although the controlled environment chambers were programmed with seasonal changes in daylength as well as average temperature and light level, the chambers were not programmed with diurnal changes in air temperature such as occur naturally and also in greenhouses. Diurnal temperature ramping was not used because it was previously shown that average temperature during seed development controlled soybean seed tocopherol metabolism, regardless of whether plants were exposed to constant temperature or temperatures that fluctuated with a 10 deg. C range. However, the effect of drought may be exacerbated by ramping treatments that create elevated midday temperatures (even though daily average temperatures are identical to those when plants are grown at constant temperature). This possibility is currently being tested with diurnal temperature ramping superimposed on previously used protocols that simulate seasonal changes with soybeans emergence at the summer solstice and physiological maturity and harvest 90 days later at the autumnal equinox. In addition, a more realistic simulation of environmental stress exposure is being tested. At defined stages of seed development, plants are probed with short-term drought (50% reduction in water for 10 days) and heat stress (7 deg. C increase in temperature for 7 days starting 3 days after the initiation of water withholding). Furthermore, all treatments are conducted at ambient and elevated atmospheric CO2 to determine if changes in this parameter affect plant stress effects on soybean seed phytochemical composition.

Review Publications
Britz, S.J., Kremer, D.F., Kenworthy, W. 2008. Tocopherols in soybean seeds: genetic variation and environmental effects in field-grown crops. Journal of the American Oil Chemists' Society. 85(10):931-936.

Last Modified: 12/21/2014
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