Involvement of stress-induced ethylene biosynthesis in fruit softening of 'Saijo' persimmon

The possible involvement of stress-induced ethylene in softening of 'Saijo' persimmon fruit with or without >95 % CO2 treatment for 16 hr at 25 degree sC, a technique widely used for the removal of astringency (Constant Temper ature Short Duration (CTSD) method) was investigated. To confirm the role o f ethylene in fruit softening, fruit were treated with 1-methyleyclopropene (MCP), a strong inhibitor of ethylene perception. The softening of treated fruit was inhibited markedly compared with non-treated fruit. Fruits, with or without CO2 treatment, were held in high (>95 % RH) or low humidity (40 -60% RH) at 20 degreesC to determine the effects of water and CO2 stresses on postharvest ethylene production and fruit softening. Without CO2 treatme nt, ethylene production and fruit softening were retarded significantly by high humidity. Whereas, with CO2 treatment, a considerable amount of ethyle ne was produced and fruit softened, irrespective of humidity. These results indicate that ethylene is involved in fruit softening and that its evoluti on is stimulated not only by water stress but also by CO2 Stress in 'Saijo' persimmon fruit.