3. ホテイアオイ花茎の正の重力屈性におけるオーキシンの関与

抄録

There are some plants in which the stem shows the positive gravitropism at the reproductive growth. Water hyacinth (Eichhornia crassipes) is also a kind of such plants. The peduncle of water hyacinth shows the downward bending within 24 hours after full flowering. Previously it was suggested that the downward bending of peduncle in water hyacinth is the positive gravitropism using the three dimensional (3D-) clinostat. From the application of anti auxin and the quantitative analysis of endogenous IAA, it was elucidated that the downward bending of peduncle is caused by the differential growth of epidermal cells of its portion, because auxin is unevenly distributed in the convex side of the bending part of peduncle. Presently in order to investigate the relation of auxin on the peduncle bending in water hyacinth further, the influence of exogenous auxin was examined. When the inflorescence was removed, the peduncle bending was induced downward at the side of by IAA application. Moreover the plants which applied lanolin paste containing IAA were cultured on the 3D-clinostat. As a result, the peduncle bending was induced at the side of IAA application. And when IAA was applied to the peduncle in the shape of ring, the peduncle bending was not induced. From these results, it was cleared that the positive gravitropism of the peduncle in water hyacinth is caused by the differential growth of epidermal cells on its portion, because auxin supplied from inflorescence is unevenly distributed in the convex side of the bending part of peduncle. It is also though that the peduncle bending was induced by IAA application to one side of peduncle, even if there was no gravity.