Changes in soluble sugar content and respiration rate in methyl jasmonate-treated rice leaves

The changes in respiration rate and soluble sugar content of detached rice (Oryza sativa) leaves were followed during methyl jasmonate (MJ)-promoted senescence. Increase in the respiration of detached rice leaves was observed as a consequence of methyl jasmonate (MJ) treatment for 48 h. However, MJ had no effect on photosynthetic rate in rice leaves. Sucrose and glucose contents, but not fructose content, were lower in MJ-treated rice leaves than in control leaves. KCN, an inhibitor of cytochrome c oxidase, was effective in inhibiting MJ-increased respiration rate, in reducing MJ-decreased sucrose and glucose contents, and in retarding MJ-promoted senescence of rice leaves. Exogenous addition of sucrose to MJ-treated rice leaves increased endogenous sucrose and glucose contents, but did not prevent MJ-promoted senescence of rice leaves. The role of respiration and sucrose in regulating MJpromoted senescence of rice leaves is discussed.