Page Banner

United States Department of Agriculture

Agricultural Research Service

Research Project: ENVIRONMENTAL EFFECTS ON PHYTOCHEMICALS IN FOOD CROPS: CONNECTING GLOBAL CHANGE AND HUMAN NUTRITION
2010 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
It was hypothesized that elevated atmospheric CO2 will have greater effect on phytochemical composition in leaves than in seeds, since leaves are exposed directly to atmospheric conditions whereas developing seeds are buffered by maternal tissue. To test this hypothesis, isoflavones and flavonols were measured in leaves of red clover raised from seed over a 4 month period in controlled environments simulating local solar equinox conditions at 400, 600, or 800 ppm CO2. Near the end of the experiment all plants in all 3 conditions were stressed for 7 days with a transient 5 degree C temperature increase while one-half the plants were stressed simultaneously with a 50% reduction in applied water. Following the transient stress, plants were allowed to recover for 2 weeks in standard conditions. While elevated CO2 clearly reduced the magnitude of the stress (as measured by soil moisture content) and the response (as measured by relative leaf water content), none of the CO2 or stress treatments affected measured phytochemical composition.

The goal of this project plan was to evaluate the effects of climate change on nutrient content; weather was used as a proxy to study climate change. It is difficult to undertake large scale simulations of the elevated temperature and altered soil moisture that are expected along with rising atmospheric CO2. However, a combination of long-term field campaigns incorporating high-stress years and controlled environment studies may help in the assessment of climate change impacts on crop yields and quality. Thus, heat and drought stress effects on field-grown soybean seed yield and composition were consistent with controlled environment studies and revealed large increases in seed vitamin E (alpha-tocopherol) but large decreases in phytoestrogens (isoflavones) under stress conditions. However, slight shifts in soybean seed development due to later and cooler conditions, accomplished with the use of later-maturing genetic lines, later planting dates, or cultivation in Central Maryland vs. the Lower Eastern Shore of Delmarva dramatically reduced the impact of environmental stress. Although the field studies did not incorporate different atmospheric CO2 levels, controlled environment studies revealed that CO2 had only small effects on seed composition and generally reduced the effects of stress. These results indicate that more attention should be given to the use of weather as a proxy to evaluate potential effects on global change on crops and, furthermore, moderate changes in cultivation practice may suffice to adapt crop production to extreme weather conditions.


4.Accomplishments
1. Heat and drought stress effects on field-grown soybean seed yield and composition consistent with controlled environment studies revealed large increases in seed vitamin E (alpha-tocopherol) but large decreases in phytoestrogens (isoflavones) under stress conditions. Slight shifts in soybean seed development due to later and cooler conditions, accomplished with the use of later-maturing genetic lines, later planting dates, or cultivation in Central Maryland vs. the Lower Eastern Shore of Delmarva dramatically reduced the impact of environmental stress. Although the field studies did not incorporate different atmospheric CO2 levels, controlled environment studies revealed that CO2 had only small effects on seed composition and generally reduced the effects of stress. These results indicate that more attention should be given to the use of weather as a proxy to evaluate potential effects on global change on crops and, furthermore, moderate changes in cultivation practice may suffice to adapt crop production to extreme weather conditions.


Last Modified: 11/21/2014
Footer Content Back to Top of Page