Internode Elongation of Rice Plant : III. Role of organs in the second internode elongation of rice seedlings

Abstract

By using the rice seedlings (Oryza sativa L.), the physiological roles of leaves, roots, endosperms and hulls in the second internode elongation were studied. The following results were obtained. 1. The endosperm consumption was suggested to be hardly affected with light irradiation or gibberellic acid (GA₃) application. 2. The elongation of the second internode was strongly diminished when the leaves were removed on the 2∼5th day before the apparent elongation occurred, but it was little affected by the removal of roots and hulls. 3. The inhibition by leaf removal was partially reversed by the GA₃ pretreatment. 4. The greater inhibition of the second internode was induced by the light irradiation to the shoot tip. 5. The substances diffused from dark-grown shoots to agar block were shown to have a stimulative effect on the internode growth of dark-grown plant, and those from light-irradiated shoots a inhibitory effect. 6. These results may suggest an important role of the leaves as a producer of the internode growth regulators, the activities of which are much affected by light conditions.