Abstract
The change of angle degrees between laminae and sheaths as a result of the gravity stimulus was investigated with intact and excised leaves of rice (Oryza sativa L. ). The following data have been obtained. Lamina inclination was occurred 6 to 17 hours after placing the seed-lings at gravitational fields. The stimulation was the most effective at the angle of inverted position. Effects of IAA on lamina inclination was observed in both intact and excised leaves which were placed at vertical position. But this effect did not appear before the end of lag period which requires several hours to appear. In the excised leaves placed at horizontal position no acceleration of the inclination by IAA was observed during the lag period. From the results described here and information obtained in the previous papers it is assumed that by gravitational stimulation, first, endogenous auxin is produced in the lamina joint of leaves, second, auxin induces the biochemical progress in the lag period of lamina inclination and a reversible component to develop of the cell extension in lamina joint, thus resulting in the inclination of laminae in the intact and excised leaves.
