Elevated Carbon Dioxide and Ozone Effects on Peanut: I. Gas‐Exchange, Biomass, and Leaf Chemistry

The effects of elevated CO2and ozone (O3) on net photosynthetic rate (A) and growth are generally antagonistic although plant responses are highly dependent on crop sensitivity to the individual gases and their concentrations. In this experiment, we evaluated the effects of various CO2and O3mixtures on leaf gas‐exchange, harvest biomass, and leaf chemistry in peanut (Arachis hypogaeaL.), an O3–sensitive species, using open‐top field chambers. Treatments included ambient CO2(about 375 μmol mol−1) and CO2enrichment of approximately 173 and 355 μmol mol−1in combination with charcoal‐filtered air (22 nmol O3mol−1), nonfiltered air (46 nmol O3mol−1), and nonfiltered air plus O3(75 nmol O3mol−1). Twice‐ambient CO2in charcoal‐filtered air increased Aby 23% while decreasing seasonal stomatal conductance (gs) by 42%. Harvest biomass was increased 12 to 15% by elevated CO2In ambient CO2, nonfiltered air and added O3lowered Aby 21% and 48%, respectively, while added O3reduced gsby 18%. Biomass was not significantly affected by nonfiltered air, but was 40% lower in the added O3treatment. Elevated CO2generally suppressed inhibitory effects of O3on Aand harvest biomass. Leaf starch concentration was increased by elevated CO2and decreased by O3Treatment effects on foliar N and total phenolic concentrations were minor. Increasing atmospheric CO2concentrations should attenuate detrimental effects of ambient O3and promote growth in peanut but its effectiveness declines with increasing O3concentrations.