Studies on the Mechanism of Injurious Effects of Toxic Gases on Crop Plants : V. Effects of sulfur dioxide on photosynthesis of rice plants

This experiment was undertaken to examine an injurious effect of sulfur dioxide on photo-synthesis and absorption of sulfur into leaves of the rice plant. The results obtained were as follows: 1) Both apparrent and gross photosynthesis were depressed by the fumigation of sulfur dioxide. Apparrent photosynthesis was completely restrained one hour after the plant was exposed to the gas, when treated cotinuously at higher concentrations such as 20 and 40 ppm. 2) At the concentrations of 6, 10 and 20ppm, the depression of apparent photosynthesis caused by the fumigation of sulfur dioxide for one hour was restored to the original state almost two hours after the gas was removed, but not restored at the concentrations of 30 and 70 ppm. 3) When the rice plant was fumigated with sulfur dioxide at the concentrations up to 20 ppm, sulfur content in the leaves of this plant increased remarkably, showing only slight increase as the concentration of the gas became higher. The content of sulfur absorbed in the leaves was, however, increased in proportion to the length of fumigation period.