INTERACTIVE EFFECTS OF ATMOSPHERIC CO2 ENRICHMENT AND LIGHT-INTENSITY REDUCTIONS ON NET PHOTOSYNTHESIS OF SOUR ORANGE TREE LEAVES

In a tong-term study of the effects of a 300 mul l-1 enrichment of the air's CO2 content on the growth of sour orange trees, a comprehensive set of net photosynthesis and light intensity data was obtained. From these measurements we derived single-leaf light response curves, which together with complementary leaf area index data allowed us to derive full-canopy light response curves. The results showed our 85% enhancement of the air's CO2 content to more than double canopy net photosynthesis at full sunlight. Our analysis demonstrated that the positive direct effect of atmospheric CO2 enrichment on net photosynthesis more than compensated for the negative self-shading effect produced by the CO2-induced proliferation of leaf area.