Abstract
In order to investigate experimentally the mechanism of injurious effects of sulfur dioxide on crop plants, an apparatus was assembled for fumigating the plants with sulfur dioxide in various concetrations determined by an SO2-analyzer of self-recording system. The apparatus was effective to corroborate the relation between the concentration of sulfur dioxide and the degree of leaf injuries caused by the gas. The resulfs obtained were as follows: 1. In tobacco plant, both dry weight and area of injured portion of the leaf increased with an increase of the concentration of sulfur dioxide to which the plants were exposed. 2. Tobacco plant and barley showed a higher percentage of dry weight of injured portion of the leaf at the flowering stage than at the vegetative stage, especially the leaf of the former plant being severely damaged. 3. In paddy rice, no significant difference in the susceptibility was observed between the highest tillering stage and the booting stage. 4. A relative resistance of crop plants to sulfur dioxide was expressed by the following order; in the vegetative stage, paddy rice> barley> tobacco plant> orchard grass> alsike clover and in the reproductive stage, paddy rice> barley> tobacco plant. 5. Two kinds of typical symptoms of injuries caused by sulfur dioxide were observed on the leaf-blade and-sheath of paddy rice : The one was countless spots of brown and brownish red color, and the other was lesions of white color, these symptoms being observed at the tip of the leaf-blade, interveinal and, sometimes, marginal parts of the leaf-blade and-sheath of paddy rice.
