The Change in the Metabolic Activity of the Rice Plant Affected by Cold Water as Viewed from its Nitrogen and Carbohydrate Contents

[摘要] The rice plant when grown under cold water condition becomes undergrown as compared with that grown under normal water condition. Using such an under-grown plant (stage of elongation) as well as well-grown one for comparison an analysis was made of the nitrogen and/or carbohydrate content in their bodies on dry weight basis with the object of investigating the metabolic process of these substances. From the results obtained, it was found that the affected rice plant, besides being rich in protein-and soluble-nitrogen, is characterized by a remarkable increase in soluble-nitrogen content, and especially so in its leaf sheath. Namely, in the leaf sheath of the affected undergrown plant, ammonia-nitrogen increased in content to thrice, amino-nitrogen to five times, and amide-nitrogen to nine times as much as those nitrogens in the normal well-grown plant, respectively, while protein-nitrogen did not show so much an increase in content as compared with the other nitrogens analyzed. This finding seems to imply that protein synthesis is much repressed in its process in the affected undergrown rice plant. In the affected undergrown plant, carbohydrate in the root was substantially equal in content to that in the normal one, but total sugar and starch in both the leaf blade and the leaf sheath showed an essential increase in content, particularly the starch accumulated in the leaf blade being remarkably large in percentage content. This Should be interpreted as the result from the abnormal stagnation of starch in the leaf blade which is an assimilating organ. In the affected rice plant, the ratio of non-reducing sugar to reducing sugar was higher in the leaf sheath as compared with that in the normal plant. This fact must be an indication of a decline of hydrolytic activity for transforming sucrose into glucose, in other words, of the repres-sion of metabolic activity for sugar transformation in the leaf sheath of the affected plant. It may be stated in conclusion that nitrogen and/or carbohydrate metabolism are repressed in the undergrown (rice) plant affected by cold water, for which the repression in metabolic activity in the leaf sheath is highly responsible.

[学科分类] 农业科学（综合）