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

Abstract

The effects of elevated CO2 and 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 CO2 and O3 mixtures on leaf gas‐exchange, harvest biomass, and leaf chemistry in peanut (Arachis hypogaea L.), an O3–sensitive species, using open‐top field chambers. Treatments included ambient CO2 (about 375 μmol mol−1) and CO2 enrichment of approximately 173 and 355 μmol mol−1 in combination with charcoal‐filtered air (22 nmol O3 mol−1), nonfiltered air (46 nmol O3 mol−1), and nonfiltered air plus O3 (75 nmol O3 mol−1). Twice‐ambient CO2 in charcoal‐filtered air increased A by 23% while decreasing seasonal stomatal conductance (gs) by 42%. Harvest biomass was increased 12 to 15% by elevated CO2 In ambient CO2, nonfiltered air and added O3 lowered A by 21% and 48%, respectively, while added O3 reduced gs by 18%. Biomass was not significantly affected by nonfiltered air, but was 40% lower in the added O3 treatment. Elevated CO2 generally suppressed inhibitory effects of O3 on A and harvest biomass. Leaf starch concentration was increased by elevated CO2 and decreased by O3 Treatment effects on foliar N and total phenolic concentrations were minor. Increasing atmospheric CO2 concentrations should attenuate detrimental effects of ambient O3 and promote growth in peanut but its effectiveness declines with increasing O3 concentrations.