INTERACTIVE EFFECTS OF ATMOSPHERIC CO2 ENRICHMENT AND LIGHT-INTENSITYREDUCTIONS 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, whic h together with complementary leaf area index data allowed us to deriv e full-canopy light response curves. The results showed our 85% enhanc ement of the air's CO2 content to more than double canopy net photosyn thesis at full sunlight. Our analysis demonstrated that the positive d irect 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.