Studies on Growth of Leaves of Paddy Rice Plant. : 2. Seasonal Changes of Starch Content in Leaf-Sheath.

Abstract

This experiment was carried out to make sure the seasonal changes of starch content in leaf-sheath according to the leaf orders with the same object as shown in Report I, especially in relation to the developing process of rice grain. The results obtained are summarized as follows: 1. Starch content in sheath of the sucessive leaves is changed regularly according to the leaf order as shown in Fig. 1. The content was rather much in the 6th sheath, minimum in the 8th one and successively increased in upper ones up to the 13∼14th orders which showed the maximum content. Above the 15th sheathes the content showed decending tendency again. The 16th sheath (the uppermost leaf) showed far smaller content. 2. The minimum content of starch in the 8th sheath might be due to the vigrous growth of vegatative parts and to the high nitrogen content of the leaves in the unavailable tillering stage; and the maximum content of starch, put in temporary storage in the 13∼14th sheaths was correlated with the highest cabohydrate assimilation and immature stage of ear which should later induce the translocation of starch. Small content of starch in the 16th sheath is caused by the direct translocation of carbohydrates to ear in develsping period of grain. 3. Starch content in each leaves changed with their life process, and increased according to the development of sheath and decreased with the decaying. 4. Changes of starch content per plant were shown minimum at early unavailable tillering stage and gradually increased immediately before earing time which showed maximum content of starch, and later decreased gradually again. The investigation of the starch content in the culm must be the subject of future research to obtain a conclusion.