Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: September 6, 2006
Publication Date: October 10, 2006
Citation: Booker, F.L., Fiscus, E.L. 2006. Interactive effects of atmospheric carbon dioxide and ozone on gas-exchange, biomass, and yield of essex soybean: a compilation of studies from ten growing seasons. ASA-CSSA-SSSA Annual Meeting Abstracts. Technical Abstract: Current levels of pollutant ozone in industrialized regions worldwide suppress the growth and yield of many agronomically important crops. Meanwhile, atmospheric concentrations of CO2 continue to increase, due in large part to the same activities leading to elevated tropospheric ozone production, combustion of fossil fuels. Elevated CO2 is an aerial fertilizer for many crop species, and its metabolic and physiological effects have the potential to lessen ozone -induced stress. To investigate interactive effects of these gases on the physiology and productivity of soybean [Glycine max (L.) Merr., cv. Essex], container- and ground-grown plants were treated with reciprocal combinations of elevated ozone and CO2 over ten growing seasons in open-top field chambers. Results showed that detrimental effects of ozone on net photosynthesis, biomass, and yield were usually attenuated by elevated CO2. Twice-ambient CO2 concentrations reduced seasonal average leaf conductance and ozone uptake by 40% and increased net photosynthesis during reproductive growth by 22%. Added ozone suppressed biomass and yield by about 30% at ambient CO2, but these effects were almost entirely reversed as atmospheric CO2 concentration increased to twice-ambient levels. Elevated CO2 effects on ozone flux and net photosynthesis were the clearest mechanistic explanations for diminished ozone symptoms. Additional effects of elevated CO2 on antioxidant capacity, leaf morphology, and as yet, undetermined factors, possibly aided in countering ozone toxicity as well. However, it is likely that tropospheric ozone pollution will continue to detract from the aerial fertilization effect of elevated CO2 in the foreseeable future.