Morphological responses among crop species to full-season exposures to enhanced concentrations of atmospheric CO2 and O3
Field studies using open-top chambers were conducted at USDA-BARC involving the growth of soybeans ('89 & '90), wheat ('91 & '92), and corn ('91), under increased concentrations of atmospheric CO2 and O3. Treatment responses were compared in all cases to plants grown in charcoal-filtered (CF) air (seasonal 7-h mean = 25±3 n mol O3 mol−1) having 350 or 500 μ mol CO2 mol−1. Elevated seasonal O3 levels for the soybean, wheat, and corn studies averaged 72.2±4, 62.7±2, and 70.2 n mol O3 mol−1, respectively. Results presented were obtained for plants grown in silt loam soil under well-watered conditions. Grain yield increases in response to elevated CO2 in the absence of O3 stress averaged 9.0, 12.0, and 1.0% for soybean, wheat, and corn; respectively. Reductions in grain yields in response to the elevated O3 treatments at 350 μ mol CO, mol−1 averaged 20.0, 29.0 and 13.0% for soybean, wheat, and corn, respectively. Reductions in grain yields in response to elevated O3 at 500 μ mol CO2 mol−1 averaged 20.0, 8.0, and 7.0% for soybean, wheat, and corn, respectively. Dry biomass and harvest index in wheat were significantly reduced by O3 stress at 350 μ mol mol 1 CO2 but not at 500 u mol mol−1 CO2. Seed weight 1000−1 for scybeans and wheat was significantly increased by CO2 enrichment and decreased by O3 stress. Seed weight 1000−1 in corn was increased by O3 stress suggesting that O3 affected pollination resulting in fewer kernels per ear.
Key wordsGlobal climate change photochemical oxidants
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