|Ainsworth, Elizabeth - Lisa|
Submitted to: Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2012
Publication Date: 12/1/2012
Citation: Betzelberger, A.M., Yendrek, C.R., Sun, J., Leisner, C.P., Nelson, R.L., Ort, D.R., Ainsworth, E.A. 2012. Ozone exposure response for U.S. soybean cultivars: linear reductions in photosynthetic potential, biomass and yield. Plant Physiology. 160(4):1827-1839. Interpretive Summary: Ozone is a damaging air pollutant that causes significant yield loss in sensitive plants. Soybean is particularly sensitive to ozone, and this research investigated the exposure response of 7 different soybean lines to 9 concentrations of ozone. Any increase in background ozone above current concentrations caused a linear decrease in yield of ~0.5 bushels per acre per part per billionozone. In addition to decreased seed yields, elevated ozone reduced photosynthesis, canopy leaf area and individual seed size. Antioxidant metabolism within the plants was increased with exposure to ozone, suggesting a trade-off between defense and primary metabolism. This work provides further evidence that diverse soybean lines are sensitive to ozone, that any increase in ozone above today's levels will cause a significant decrease in soybean production, and also identifies multiple targets for improving soybean tolerance to ozone.
Technical Abstract: Current background ozone concentrations ([O3]) over the Northern Hemisphere’s mid-latitudes are high enough to damage crops, and are projected to increase. Soybean (Glycine max [L.] Merr.) is particularly sensitive to O3 therefore establishing an O3 exposure-threshold for damage is critical to understanding the current and future impact of this pollutant. This study aims to determine the exposure-response of soybean to elevated tropospheric O3 by measuring the agronomic, biochemical and physiological responses of seven soybean genotypes to nine [O3] (38 ppb to 120 ppb) within a fully open-air agricultural field location, across two years. All genotypes responded similarly with season-long exposure to O3 causing a linear increase in antioxidant capacity while reducing leaf area, light absorption, specific leaf mass, primary metabolites, seed yield and harvest index. Across two seasons with different temperature and rainfall patterns, there was a robust linear yield decrease of 37-39 kg ha-1 per ppb of cumulative O3 exposure over 40 ppb. The instantaneous effects of O3 on photosynthesis, stomatal conductance, and photosynthetic transcript abundance before and after initiation and termination of O3 fumigation were concurrently assessed, and there was no evidence to support an instantaneous photosynthetic response. The ability of the soybean canopy to intercept radiation, the efficiency of photosynthesis and the harvest index were all negatively impacted by O3, suggesting that there are multiple targets for improving soybean responses to this damaging air pollutant.