PARENT SESSION
Organized Oral Session 1: Understanding the impacts of oxidative stress in plants: From molecules to ecosystems
Organizer(s): HS Neufeld and N Grulke
Monday, August 8, 8:00 AM - 11:30 AM, Meeting Room 510a, Level 5, Palais des congrès de Montréal
Alleviation of ozone-induced oxidative stress by elevated CO2 in crop plants.
Booker, Fitzgerald*,1, 2, 1 U.S. Department of Agriculture - Agricultural Research Service, Raliegh, NC, USA2 Department of Crop Science, Raleigh, NC, USA
ABSTRACT- Current ambient ozone concentrations in many regions of the world suppress yields of susceptible crops such as soybean, peanut, cotton, rice, and wheat by 5 to 15% annually. However, rising concentrations of atmospheric CO2 may lessen the detrimental effects of ozone pollution in part by reducing ozone uptake by crop plants. Field studies using open-top chambers indicate that twice-ambient levels of CO2 reduce ozone uptake by 27 to 42% in soybean as determined by measurements of midday leaf conductance, whole-plant transpiration, and ozone concentrations. The reduction in ozone flux was associated with the lack of ozone-induced reductions in net photosynthesis, biomass production, and yield in soybean treated concurrently with elevated CO2 and ozone. The response in soybean appeared unrelated to changes in antioxidant metabolism except possibly ascorbic acid. Total ascorbic acid concentration in lower canopy leaves increased by 28 to 64% in elevated CO2 and ozone but not in upper canopy leaves. Increasing concentrations of atmospheric CO2 will likely ameliorate ozone damage to many crops due to reduced ozone uptake and as yet undetermined additional factors. While this might be seen as a fortunate coincidence, it is difficult to predict how interactions between these factors and other possible changes in global climate will play out. At present, it is reasonable to conclude that ambient ozone detracts from crop productivity possible in clean air in many regions of the world and suppresses the amount of carbon that could be fixed in a CO2-enriched atmosphere.
Key words: ozone, carbon dioxide, flux, soybean