Relationship between Ethylene Evolution and Sucrose Content in Excised Leaf Blades of Rice

We examined the relationship between ethylene evolution and carbohydrate content in leaf blades excised from rice (Oryza sativa L. cv. Nipponbare) seedlings at the four-leaf stage. The rate of ethylene evolution from the excised leaf blades sampled at various times exhibited diurnal fluctuation ; it was the lowest at 5 : 00, increased to the maximum at 13 : 00, then decreased. The sucrose content in leaf blades showed the same fluctuation as the rate of ethylene evolution. Application of sucrose stimulated the evolution of ethylene and increased the contents of glucose, fructose and sucrose in the leaf blades. After the application of glucose or fructose, both the rate of ethylene evolution and sugar content increased, but glucose and fructose increased much less than sucrose. In these experiments, sucrose content was closely correlated with the rate of ethylene evolution in rice leaf blades. From these data we concluded that sucrose content regulated the rate of ethylene evolution from leaf blades in young rice seedlings.