Abstract
In this study, authors tried to compare the rice plants grown in normal and "Akiochi" paddy fields, with resdect to the seasonal changes of starch content in their sheathes. In "Akiochi" plant, the changes of strch content in each sheath showed the same tendency as in normal one, but there was evident difference quantitatively. In the 6-9th leaf sheathes, there was no evident difference between the starch content in them, but from the 1Oth order upwards starch content was lower in "Akiochi" plant than healthy plant, and the difference became greater according to the leaf order. This fact seems to be connected with poor development of grains in "Akiochi" plant. Since the stage when starch had begun to accumulate in the 1Oth sheath (unavailable tilling stage), "Akiochi" plant became to be poor in its nutritive condition and this stage, also, was corresponding to the appearance of Helminthosporium spots. So, in this case, initiation of this disease can be recognized as the first indication of "Akiochi" phenomenon. The decreasing rate of sheath dry weight from the maximum in "Akiochi" plant was also smaller than the normal one. The main reason for this difference is supposed to be the difference of starch content between them.
