Abstract
1. In the present paper the writer described the results of the experiments on the relation of silicic acid supply on soil to the disease outbreak in rice plants.
2. The application of silicic acid on soil increases the resistance to blast disease on pedicels of spikes of rice plants and the application of silica with boric acid er copper sulphate decreases effectiveness of silica given. Single supply of boric acid or copper sulphate on soil may cause a little suppression to the outbreak of rice blast disease.
3. The relation of the supply of silicic acid, with boric acid, or copper sulphate on soil to the outbreak of Helrminthosporium-blight on leaves is entirely similar to that of blast disease. The silicification of epidermal cell walls in adult leaves increased remarkably with the supply of silicic acid on soil. Single application of boric acid on soil resulted in a little increase of the silicification, but copper sulphate supply has the tendency to inhibit the silicification of leaves.
