Abstract
The first experiment was carried out to make clear the effect of Ethrel and ethylene on the growth and development in rice plant at various growth stages. In the next one evolution of ethylene from rice plant was measured. The results obtained were as follows: 1. Elongation of the second leaf-sheath was accelerated with 50 to 10O ppm of Ethrel, while plant height after transplanting stage was retarded. 2. The plant age was slightly promoted by the application of Ethrel at young seedling stage. 3. An abnormal elongation of internode was caused by the application of Ethrel at young seedling stage. The same tendency was found at the internode elongation stage. 4. Promotion of tillering by the application of Ethrel was clearly see. For instance in Ethrel-applied seedlints tillers emerged from coleoptile and the first leaf nodes, the axillary buds of which usually remain dormant. 5. Panicle weight was decreased by the application of either Ethrel or ethylene dueing mainly to degeneration of rachis branches and spikeles. 6. Young seedlings were damaged by a high concentration of Ethrel. The degree of damage was varied among the varieties. Generally speaking, indica varieties were more susceptible than japonica ones. The same tendency was seen by ethylene treatment. 7. Ethrel as well as ethylene caused an epinastic response in rice plants. 8. Chlorophyll destruction which is related to leaf senesence was accelerated by the application of either Ethrel or ethylene. 9. It was confirmed that ethylene is evolved from rice seedlings.
