Effects of free-air CO2 enrichment on the light response curve of net photosynthesis in cotton leaves

Abstract

Daytime measurements of leaf CO2 exchange rates in a free-air CO2 enrichment (FACE) experiment reveal that at photosynthetically active radiation (PAR) flux rates in excess of 1000 μmol m−2 s−1, cotton leaves exposed to an atmospheric CO2 concentration of approximately 500 μmol mol−1 exhibit net photosynthetic rates about 30% greater than those for leaves of similar plants growing in ambient air. As PAR flux rates drop below this value, the stimulatory effect of elevated CO2 rises, suggesting that the relative benefits of atmospheric CO2 enrichment will be greater for shaded cotton leaves that for those exposed to full sunlight.