Action Mechanism of Ethylene in the Control of Sugar Translocation in Relation to Rice Coleoptile Growth I. Sucrose Metabolism

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The fate of ^<14>C-glucose fed through scutella of rice (Oryza sativa L. cv. Sasanishiki) seedling explants was investigated in relation to ethylene action on sugar translocation to growing coleoptiles and leaves. In the scutellum, sucrose, UDPglucose and F6P were rapidly labeled, and sucrose-phosphate synthase activity was higher than sucrose synthase activity. Radioactive sucrose soon appeared in both coleoptiles and leaves, and increased rapidly. Its specific activity in both tissues became almost equal to that in the scutella. The specific activities of ^<14>C-glucose in both coleoptiles and leaves changed almost in parallel to those of ^<14>C-fructose. These results suggest that sucrose was synthesized in the scutellum and exported to the coleoptile and leaf, where it was cleaved to glucose and fructose. Ethylene slightly increased the specific activities of ^<14>C-sucrose in all tissues, but markedly in-creased those of ^<14>C-glucose and -fructose only in the coleoptile. We assume that the ethylene enhancement of sucrose transport from scutellum to the coleoptile results from the activation of sucrose unloading in the growing coleoptile where imported sucrose is cleaved into glucose and fructose.
日本植物生理学会の論文