Short‐Term Kinetic Studies on the Inhibition of Photosynthesis by Sulfur Dioxide

Abstract Utilizing infrared gas analysis techniques, the effect of a 1‐hour exposure to 1, 3, or 5 ppm SO2 on apparent photosynthesis in the primary leaf of Pinto bean (Phaseolus vulgaris L. cv. Pinto) was studied as a function of three leaf ages. Generally, photosynthesis was reduced about 15, 70, and 90% for the respective concentrations regardless of leaf age. The initial inhibition of photosynthesis was not due to stomatal closure. Inhibition kinetics observed at 1 and 3 ppm SO2 for Pinto bean (Phaseolus vulgaris L.) were compared with those of SO2‐tolerant corn (Zea mays L.). At 1 ppm SO2, the kinetics of inhibition of photosynthesis for the two species were similar; however, at 3 ppm SO2, apparent photosynthesis in corn was inhibited less than in Pinto bean and recovered to a higher level following removal of SO2.