Abstract
Cochliobolus miyabeanus was inoculated on the normal and "Akiochi" (autumn-decline) rice plant and the changes of nitrogen compounds, carbohydrates, reducing ascorbic acid and respiration of the plants accompanied by the infection, were examined. In both plants, soluble and insoluble nitrogens decreased by the infection, though the "Akiochi" plant showed less insoluble nitrogen from the outset. Reducing sugar, soluble cardohydrate also decreased while insoluble carbohydrate increased. Reducing ascorbic acid suddenly decreased in both plants, but the "Akiochi" plant had little amount of the acid before the infection. Qo2 increased and R·Q decreased in both plants. The decrease of R·Q was much greater in the "Akiochi" plant than in the normal one. The examination of the existence of hyphae in the spots showed that the fungus lived in every part of them. From the perthophytic action of this fungus and these results, the writer thought that the defence layer was formed and the fungus was shut out by the layer and the spread of spot was ceased.
