Abstract
Changes in the respiratory rate and activities of cytochrome c oxidase, ascorbic acid oxidase, peroxidase and catalase of leaf blade as affected by the occurrence of the disease were examined using the rice plants cultured by pot experiment method with and without potassium supply, employing the actual paddy field soil on which the disease habitually occurs. Want of potassium caused the disease on lower leaves. Respiratory rate especially that of lower leaf was promoted by the occurrence of the disease and peroxidase and catalase activities were also promoted, but the activities of cytochrome c oxidase and ascorbic acid oxidase declined. These facts indicate that flavin enzymes act as terminal oxidase accompanying with production of H2O2, in place of metalic enzymes such as cytochrome c oxidase and ascorbic acid oxidase. When the ratio of QO2CO2/(QN2CO2) is near to 1 the Pasteur effect exists, and it is said that in such a case thereaction of oxidative phosphorylation might likely be active whereas the increase of this value indicates the decrease of this effect and so the oxidative phosphorylation is supposed to decline. The value QO2CO2/(QN2CO2) of the lower leaf suffered by the disease was as high as two. From these results the promoted respiratory rate due to the occurrence of the disease seems to be accompanied with conversion of terminal oxidase and is supposed to be less efficient for oxidative phosphorylation, on which the further study will be focused.
