The influence of red and blue light on the rate of photosynthesis and the CO2compensation point at various oxygen concentrations

摘要

Apparent photosynthesis of attached leaves ofPhaseolus vulgaris, Vicia faba, Pisum sativum, andNicotiana tabacumat various intensities of blue and red light was measured by infrared CO2gas analyzer in a closed system. Simultaneously the CO2compensation point was measured.It was found that light-limited photosynthetic rate in blue light was equal to or more than that in red light. Inhibition of photosynthesis, which sometimes occurred at light-saturated intensities of blue light, could be avoided by addition of red light, prolonged exposure of the plants to blue light, or by lowering the O2concentration. Accordingly, the increase of photosynthetic rate due to change of O2concentration from 21 to 3 O2is higher in blue light only when photosynthesis is inhibited by blue light at 21 O2. The data on the action of blue and red light on the CO2compensation point seems to exclude the activation of photorespiration by blue light.The possible effects of blue light on apparent photosynthesis are discussed on the basis of the results presented.