Abstract
The growth of tiller buds in floating rice plants is known to be inhibited by deep water conditions. Cytokinins promote the growth of lateral buds of plants. Two experiments were carried out to observe the effects of kinetin, a kind of cytokinin, on the growth of tiller buds under deep water conditions (Expt. 1) and after lowering of the water level (Expt. 2) in floating rice plants. Seedlings were grown in solution culture. In Expt. 1, deep water treatments were applied at the plant age of 5, and kinetin was dissolved in the culture solution for absorption from roots under deep water. In Expt. 2, deep water treatments were applied during the period from the plant age of 3 to the plant age of 6, then the water level was lowered. Kinetin was dissolved in the culture solution when the water level was lowered. Kinetin promoted the growth of tiller buds under deep water conditions, and also after lowering of the water level. Kinetin promoted the growth of the tiller buds whose growth had already ceased as well as that of the tiller buds whose growth had not ceased yet.
