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CROP PHYSIOLOGY & METABOLISM

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

USDA-ARS, Plant Science Research Unit, and Dep. of Crop Science, North Carolina State Univ., 3127 Ligon St., Raleigh, NC 27607. Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the USDA or the North Carolina Agric. Res. Serv

^* Corresponding author (fitz.booker{at}ars.usda.gov).

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 (g_s) 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 g_s 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.

Abbreviations: A, net photosynthetic rate • AA, ambient air • CF, charcoal-filtered • g_s, stomatal conductance • LMPA, leaf mass per unit leaf area • NF, nonfiltered • OZ, 1.56 x ambient O₃ • PPFD, photosynthetic photon flux density • WAP, weeks after planting • WUE, water use efficiency