Submitted to: Plant Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/20/2014
Publication Date: 6/27/2014
Citation: Sun, J., Feng, Z., Ort, D.R. 2014. Impacts of rising tropospheric ozone on photosynthesis and metabolite levels on field grown soybean. Plant Science. DOI: 10.1016/j.plantsci.2014.06.012. Interpretive Summary: Rising atmospheric carbon dioxide concentration is widely recognized, but less appreciated is a concomitant rise in tropospheric ozone concentration. In industrialized countries, ozone has risen by 0.5 – 2.5 % per year. Tropospheric ozone is predicted to reach a global mean of > 60 part per billion by 2050 with greater averages locally. This study investigated the exposure response of soybean to elevated ozone by measuring the agronomic, biochemical, and physiological responses of two soybean genotypes to nine ozone concentrations (38–120 parts per billion) within a fully open-air agricultural field location across two years. Results show that the efficiency of photosynthesis and the profile of leaf metabolites in soybean were all negatively impacted by ozone.
Technical Abstract: The response of leaf photosynthesis and metabolite profiles to ozone (O3) exposure ranging from 37 to 116 nL L-1 was investigated in two soybean cultivars Dwight and IA3010 in the field under fully open-air conditions. Leaf photosynthesis, total non-structural carbohydrates (TNC) and total free amino acids (TAA) decreased linearly with increasing O3 levels in both cultivars with average decrease of 7% for an increase in O3 levels by 10 ppb. Ozone interacted with developmental stages and leaf ages, and caused higher damage at later reproductive stages and in older leaves. Ozone affected yield mainly via reduction of maximum rate of Rubisco caboxylation (Vcmax) and maximum rates of electron transport (Jmax) as well as a shorter growing season due to earlier onset of canopy senescence. For all parameters investigated the critical O3 level (~50 ppb) for detectable damage fell within O3 levels that occur routinely in soybean fields across the US and elsewhere in the world. Strong correlations were observed in O3-induced changes among yield, photosynthesis, TNC, TAA and many metabolites. The broad range of metabolites that showed O3 dose dependent effect is consistent with multiple interaction loci and thus multiple targets for improving the tolerance of soybean to O3.