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United States Department of Agriculture

Agricultural Research Service

Research Project: Effects of Elevated Atmospheric Co2, Environmental Stress, and Edaphic Conditions on Bioactive Compounds in Brassica Crops

Location: Food Components and Health Laboratory

2011 Annual Report


1a.Objectives (from AD-416)
Objective 1: Determine the impact of environmental factors of anticipated climate change (e.g., elevated CO2, increased and widely varying temperature, and changes of moisture) on the amounts and types of phytochemicals at harvest, and the persistence of these compounds postharvest, such as during storage at low temperatures, for Brassica crops. • Sub-objective 1.A. Variety Testing. Evaluate genetically-diverse varieties of kale and broccoli for their responses to elevated temperatures and elevated CO2. • Sub-objective 1.B. Soil Moisture. Using kale and broccoli varieties, evaluate effects of periodic drought or periodic flooding during cultivation at ambient or elevated CO2 and ambient or elevated temperature regimes. • Sub-objective 1.C. Postharvest. Using kale and broccoli varieties, determine if elevated CO2 and/or elevated temperature during growth alter the persistence of phytochemicals during postharvest storage at low temperature.

Objective 2: Determine the extent to which soil fertility, CO2, and other environmental stresses, and their interactions, affect changes of phytochemical composition of Brassica crops. • Sub-objective 2.A. Soil Nitrogen. Using kale and broccoli varieties, evaluate effects of low, intermediate, and high soil N during cultivation at ambient or elevated CO2 and ambient or elevated temperature regimes.


1b.Approach (from AD-416)
Interaction between atmospheric carbon dioxide and other environmental parameters will be investigated in two controlled environments (growth chambers and greenhouses) by raising crops to seed while regulating and monitoring atmospheric CO2, temperature, soil moisture, nutrition, and photosynthetically as well as photomorphogenetically active radiation. Growth chambers will simulate natural conditions. Environmental conditions at various developmental stages will be monitored and compared to those in controlled environments. Work will concentrate on kale (collards) and broccoli. Seeds will be harvested and analyzed by HPLC for important biologically active constituents, including glucosinolates. Effects of environment on biosynthethic pathways will be evaluated.


3.Progress Report
Varieties of kale and collard greens were selected for study with an attempt to include as much genetic diversity as possible with the use of heirloom lines. Controlled environment chambers and greenhouses were used to evaluate these varieties and analytical methods at ambient CO2 and temperature conditions.

Elevated atmospheric CO2 may have more effect on phytochemical composition in leaves than in seeds, since leaves are the primary tissue for photosynthesis and are exposed directly to atmospheric conditions whereas developing seeds are buffered by maternal tissue. Previously this hypothesis was tested but not supported based on studies using red clover. To test this hypothesis further, flavonoids (quercetin and cyanidin) and phenolic acid esters (i.e, caftaric, chlorogenic and chicoric acids) were measured in leaves of 4 lines of red leaf lettuce, 4 lines of green leaf lettuce, and 2 lines of chicory grown at 400, 600 or 800 ppm CO2. Although elevated CO2 stimulated plant growth 15 to 66% for 8 of 10 lines, most varieties showed little or no CO2 effect on leaf chemical composition. However, phenolic acid esters, quercetin, cyanidin, and chlorophyll a+b did increase, in order, 33, 47, 73 and 27% at 800 compared to 400 ppm in one line, Dark Lollo Rossa (a red leaf lettuce), with moderate growth stimulation by elevated CO2 (+31% top dry matter). The molecular basis for the apparent unusual response in Lollo Rossa is not yet understood but it may be subject to manipulation to improve both the growth and nutritional value of produce under future conditions of elevated CO2.


Review Publications
Britz, S.J., Schomburg, C.J., Kenworthy, W.J. 2009. Isoflavones in soybean seeds: Genetic variation and environmental effects in field-grown crops. Journal of the American Oil Chemists' Society. 88(6):827-832.

Last Modified: 10/25/2014
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