Ozone Exposure Response for U.S. Soybean Cultivars: Linear Reductions in Photosynthetic Potential, Biomass, and Yield

• Published in: Plant physiology (Bethesda) 2012-12, Vol.160 (4), p.1827-1839
• Main Authors: Betzelberger, Amy M., Yendrek, Craig R., Sun, Jindong, Leisner, Courtney P., Nelson, Randall L., Ort, Donald R., Ainsworth, Elizabeth A.
• Format: Article
• Language: English
• Subjects: Absorption; Antioxidants; Biomass; Chlorophylls; Dose response relationship; Fumigation; Gene Expression Regulation, Plant - drug effects; Gene Expression Regulation, Plant - radiation effects; Glycine max - drug effects; Glycine max - genetics; Glycine max - growth & development; Glycine max - physiology; Growing seasons; Leaves; Light; Linear Models; Ozone; Ozone - pharmacology; Photosynthesis; Photosynthesis - drug effects; Photosynthesis - radiation effects; Plant Leaves - anatomy & histology; Plant Leaves - drug effects; Plant Leaves - physiology; Plant Leaves - ultrastructure; Plants; RNA, Messenger - genetics; RNA, Messenger - metabolism; Seasons; Soybeans; United States
• ISSN: 0032-0889; 1532-2548; 1532-2548
• DOI: 10.1104/pp.112.205591

Current background ozone (O₃) concentrations over the northern hemisphere's midlatitudes are high enough to damage crops and are projected to increase. Soybean (Glycine max) 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 concentrations (38-120 nL L⁻¹) within a fully open-air agricultural field location across 2 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 to 39 kg ha⁻¹ per nL L⁻¹ cumulative O₃ exposure over 40 nL L⁻¹. The existence of immediate effects of O₃ on photosynthesis, stomatal conductance, and photosynthetic transcript abundance before and after the 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.