Abstract
In the studies on the influence of cephalothecin upon the secretion of carbohydrases and the absorption of NH4-N by the blast fungus, it was pointed out by the writer that S:N, i. e., Relative Secretion Value (Yoshii 1953), and N:H, i. e., Reiative Absorption Value (Yoshii 1953), of the culture on media supplied with cephalothecin were far larger that of check. These figures show that the increase in dry weight of the mycelium per unit amount of carbohydrates and NH4-N consumed in cultures supplied with cephalothecin is much less than that of check.
The poorer the development of the fungus in the tissue of the host is, the smaller the spot on the plant is. The spread of the fungus in the host tissue hasa certain connection with the resistance of the plant. In view of this, the sheath inoculation method (Sakamoto 1951) was applied to the earneck tissue presoaked with cephalothecin in order to determine if cephalothecin impedes the invasion processes of the blast fungus in the cells of rice plant.
The results of the observations showed that the inhibitory effects of cephalothecin on the development of the fungus were also remarkably recognized in the cells of the tissues treated with cephalothecin. So it may safely be concluded that the resistance of the treated rice plant to the blast disease is chiefly due to cephalothecin sucked in the tissue.
