Hiroshi Kurooka

The Role of Glutathione on the Onset of Endodormancy of Grape Buds

The role of glutathione, which maintains protein thiol groups in the reduced state in living cells, on the onset of endodormancy (rest) of grape buds was investigated. When potted grapevines were exposed to 30°C/25°C (high), day/night, or 20°C/15°C (low), day/night, before the onset of bud dormancy, buds administered low temperature became dormant, but those treated with high temperature did not. On shoots treated with low temperature, endogeneous ABA levels increased soon after treatment, whereas ABA levels in shoots treated with high temperature remained low. Reduced glutathione (GSH) content in the shoots treated with high temperature increased, whereas in shoots treated with low temperature, it decreased gradually. Oxidized glutathione (GSSG) content in the shoots treated with high temperature remained almost constant during the experimental period, whereas under the low temperature treatment it increased. GSSG content increased in shoots induced to dormancy by the ABA treatment. Furthermore, exogenous treatment with GSSG inhibited budbreak. Therefore, we conclude that glutathione is one of the potent factors in controlling grape bud dormancy.