Effect of Temperature, CO2 Concentration, and Light Intensity on Oxygen Inhibition of Photosynthesis in Wheat Leaves 1

摘要

The effect of 21% O2 and 3% O2 on the CO2 exchange of detached wheat leaves was measured in a closed system with an infrared carbon dioxide analyzer. Temperature was varied between 2° and 43°, CO2 concentration between 0.000% and 0.050% and light intensity between 40 ft-c and 1000 ft-c. In most conditions, the apparent rate of photosynthesis was inhibited in 21% O2 compared to 3% O2. The degree of inhibition increased with increasing temperature and decreasing CO2 concentration. Light intensity did not alter the effect of O2 except at light intensities or CO2 concentrations near the compensation point. At high CO2 concentrations and low temperature, O2 inhibition of apparent photosynthesis was absent. At 3% O2, wheat resembled tropical grasses in possessing a high rate of photosynthesis, a temperature optimum for photosynthesis above 30°, and a CO2 compensation point of less than 0.0005% CO2. The effect of O2 on apparent photosynthesis could be ascribed to a combination of stimulation of CO2 production during photosynthesis, and inhibition of photosynthesis itself.