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These studies were undertaken to identify photosynthetic traits of the cultivated peanut (Arachis hypogaea L.) that might be used in breeding programs designed to increase yield. Net photosynthesis (Pn), CO2 compensation point (Γ), stomatal diffusion resistance to water vapor and stomatal frequency were measured on 32 diverse genotypes. Pn was measured on 3 and 4 week old plants in a semi-closed compensating system, Γ by initial introduction of CO2-free air and equilibration thereof, and stomatal resistance with a diffusion porometer; photorespiration and mesophyll diffusion resistance to CO2 were calculated. At high light (1400 μE m−2s−1PAR) eight genotypes had Pn rates of 20 to 30, seventeen 31 to 40 and seven 41 to 43 mg CO2 dm−2h−1. At any given light level tested Pn rates of a given genotype were significantly different from other genotypes. Only three genotypes showed any tendency toward photosaturation at 1400 μE m−2s−1PAR. Photosynthetic rate and photorespiration were positively correlated (r = 0.92, P |
