Abstract
The present paper deals with some physiological observations on the normal and the Akiochi (autumn-decline) rice plants affected with Cochliobolus miyabeanus. 1. Healthy and affected leaves of the both plants were immersed in the culture filtrate of C. miyabeanus, and the change of their weight and the amount of nitrogen dissolved in media were measured. Healthy leaves of normal plant and affected leaves of Akiochi plant showed the decrease of leaf weight as well as the much amount of soluble nitrogen, but affected leaves of normal plant was not. The nitrogen in diseased part of normal rice plant, therefore, seems to be changed in the insoluble form. 2. Changes of thiamine contents and thiamine-destroyed substances in rice plant accompanied with the infection were observed. Thiamine, which is the essential substance for the growth of C. miyabeanus, is much contained in the Akiochi leaves, but in the normal leaves it is remarkably destroyed at the early stage of the infection. There is a little destruction of thiamine in Akiochi rice leavei. 3. Accompanying with the infection, respiration is increased in the both plants. In normal rice leaves the oxidative phosphorylation caused by respiration takes place more effectively, but in Akiochi leaves it is not so effective and substrates of respiration are uselessly consumed. 4. Diseased spot is not enlarged, when it is kept in the oxygen free condition.
