Screening for Photosynthetic Efficiency1

Abstract

Maize (Zea mays L.), sorghum (Sorghum vulgare L.) and several other plants have maximum rates of photosynthesis of 50 to 60 mg CO2 dm−2 hr−1 and have CO2 compensation concentrations (Γ) near 0 ppm. In contrast, small grains and many other plants have maximum rates of photosynthesis of 20 to 30 mg CO2 dm−2 hr−1 and Γ values near 60 ppm. By growing a mixture of these high and low Γ plants together in a closed chamber, a CO2 concentration below that necessary for survival of the high Γ plants was obtained. Only low Γ plants remained alive after 5 to 8 days in the chamber. This is a rapid and simple method for screening populations of plants for high photosynthetic rates.