Submitted to: Journal of Experimental Botany
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/16/2006
Publication Date: 6/23/2006
Citation: Christ, M.M., Ainsworth, E.A., Nelson, R.L., Schurr, U., Walter, A. 2006. Putative yield loss in field-grown soybean under elevated ozone can be avoided at the expense of leaf growth during early reproductive growth stages in favorable environmental conditions. Journal of Experimental Botany. 57:2267-2275. Interpretive Summary: Atmospheric ozone is responsible for more damage to vegetation than any other air pollutant, and the concentration is predicted to increase by 20% in the next 50 years. Understanding how soybeans and other crops will respond to this increase in atmospheric ozone is an important step towards optimizing soybean productivity in the future. We investigated the effects of elevated atmospheric ozone concentration (~20% higher than current atmospheric conditions) on soybeans grown under fully open-air conditions. Leaf carbon uptake, growth and carbohydrate content were reduced during the seed-filling growth stages; surprisingly, final yield was not decreased by elevated ozone. These results indicate that the soybean variety, Spencer, avoided yield loss under elevated ozone at the expense of leaf growth and final leaf area. This single year study shows that while ozone is expected to detrimentally affect crop performance and yield, when growing conditions are optimal, yield can be maintained under moderate increases in atmospheric ozone concentration. Future soybean growers can expect that cultivars will vary in their response to rising atmospheric ozone, and in years with adequate rainfall and moderate temperature, some soybean varieties will maintain current yields.
Technical Abstract: Ozone is a powerful oxidizing agent which is responsible for more damage to vegetation than any other air pollutant. In this study, we analyzed leaf growth, photosynthesis and carbohydrate content during the seed filling growth stage of field-grown soybeans exposed to ambient air and 1.2 times ambient ozone concentration in otherwise non-stressful environmental conditions. In contrast to predictions based on controlled environment and open-top chamber studies, final yield did not differ between treatments, although the cultivar used here was clearly sensitive to ozone damage: growth and carbohydrate content of upper canopy leaves was reduced during the seed-filling stage in which an ozone-induced decrease of photosynthesis was present. The results indicate that a putative yield loss under an elevation of ozone to anticipated 2050 levels was avoided at the expense of leaf growth, as growth reserves were diverted from vegetative to reproductive organs.