Physiological Action of Ethylene in Crop Plants : II. The role of endosperm in elongation of rice seedlings by ethylene

Abstract

Generally ethylene inhibits the extention growth of plant. But we have reported that rice seedlings were elongated by application of Ethrel which id ethylene releasing agent. The experiments conducted to make clear the effect of Ethrel and ethylene on growth in rice seedlings. The results obtained were as follows ; 1. The stimulation of rice seedling elongation by Ethrel was closely related with the volume of endosperm of seeds. The elongation of seedlings was more stimulated in the seedlings with much volume of endosperm than in ones with less endosperm. 2. Untill the 2 nd leaf stage, the growth ef seedlings was stimulated by Ethrel application. After 3rd leaf stage, however, the growth was inhibited by Ethrel. It seems that promotion or inhibition of the growth of rice seedlings depended upon the growth stage which related to endosperm consumption. 3. The rice seedlings treated with Ethrel produced more ethylene than not-treated ones. Also ethylene production in seedlings was enhanced by application of methionine, as one of precursors of ethylene. Ethylene enhancement by Ethrel was more effective in dark than in light. On the other hand, ethylene production by methionine application was active in light. 4. In methionine solution rice seedlings produced more ethylene and carbondioxide than in water. The elongation was promoted in very early growth stage, especially in coleoptile, but inhibited in later stage by methionine application. In these experiments it became clear that elongation of rice seedlings by Ethrel had close relation with the volume of endosperm in seeds, and ethylene affected the elongation of seedlings. It was suggested that ethylene had the important function as stimulater of growth in rice seedlings at early growth stage.