Effects of Gravity upon Rooting and Development of Tillering Buds in Rioe Plant

As one of georeactions shown by Gramineae, phenomena of rooting and development of tillering buds in rice seedlings were exsamined. For the morphological observations the seedlings in which the 8th leaves or the 9th leaves were unfolded respectively, but in which tillers were not yet emerged, were fixed in a holizontal position with their main axes for 6 days. The roots newly formed were apparently more numerous in the horizontal plots than in the vertical. This is chietly due to the larger number of new roots on the uppermost rooting node of the seedlings in the horizontal plots. There was no significant difference in the total length of new roots per plant between both plots. Tillering buds in the horizontal plots, when macroscopically observed, were generally more elongated in comparison with those in the vertical, especially on the 4th node of the seedling with the 8th leaf expanded and on the 4th to 7th nodes of the seedling with the 9th leaf expanded. According to the histological observations which were made of the seedlings with 6 expanded leaves, growth of tillering buds and rooting primodia were markedly accelerated on the 5th node in the seedling kept horizontally in the dark for 2 days as compared with the seedling kept vertically, though little difference could be found in the initiation and development of tillering primodia and rooting primodia on the upper nodes than the 5th one in both plots