Levels of endogenous ethylene, carbon dioxide, and soluble pectin, and activities of pectin methylesterase and polygalacturonase in ripening tomato fruits

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In 4 cultivars of tomato (Lycopersicon esculentum Mill.), the early detachment of fruits advanced ripening and considerably reduced the threshold value of endogenous C_2H_4 . This indicates a supply from the vegetative parts of (a) labile ripening-inhibiting sub-stance(s) antagonizing the action of C_2H_4. The endogenous level of CO_2 increased shortly after the rise in C_2H_4, and maximum levels of C_2H_4 and CO_2 occurred almost simultaneously. The activity of PE showed no connection with ripening, but PG activity did not occur until the onset of ripening. However, this activity increased at considerably higher C_2H_4 concentrations than the rise in WSP, and was independent of the possible presence of ripening inhibitor(s). Hence PG is considered not to be involved in the primary events leading to fruit ripening. Exposure of fruits to different C_2H_4 concentrations in the ambient atmosphere also showed PG activity to increase only after the rise in WSP had started. Other pectin degrading or synthesizing enzymes may be involved. In the non-ripening Rin mutant of cv. Rutgers, no rise occurred in C_2H_4, CO_2, WSP, and PG activity.
日本植物生理学会の論文