1985 Volume 53 Issue 4 Pages 467-473
This study was carried out to clarify the difference between climacteric and nonclimacteric type fruits in their ethylene producing activity, especially in the pathway from 1-aminocyclopropane-1-carboxylic acid (ACC), during growing and ripening stages.
In tomato fruits harvested 28 and 34 days after anthesis, carbon dioxide production was stimulated when 10ppm of ethylene was applied to the fruits for 24 hours. After the ethylene treatment, the carbon dioxide production decreased temporarily; thereafter, ethylene and carbon dioxide production increased in fruits harvested 28 days after anthesis but in fruits harvested 34 days after anthesis only ethylene production increased. In cucumber fruits harvested 5, 8, and 20 days after anthesis, carbon dioxide production was stimulated during treatment with 10ppm of ethylene for 56 houus, but after the treatment, the rate was reduced to the pre-treatment level. Thereafter the rate of ethylene production only increased in fruits harvested 5 days after anthesis, which may have been due to the fruit decay.
To observe the effect of D-, L-methionine or ACC on ethylene synthesis, these reagents were fed to tissue slices of tomato and cucumber fruits at several growing or ripening stages. Ethylene forming enzyme (EFE) activity was estimated by the rate of ethylene production due to the addition of ACC. In tomato pericarp tissue the rate of ethylene synthesis was least at the mature green stage and was greater at immature and ripening stages. The addition of ACC stimulated ethylene production in tissue slices of tomato fruits at all stages. In tissue slices of cucumber fruits, ethylene synthesis was stimulated by addition of ACC, but the rate of ethylene synthesis did not vary greatly with the development stage of the fruit. When D- and L-methionine were applied, it was found that the D-isomer enhanced ethylene synthesis in cucumber tissue slices.
ACC content of tomato and cucumber fruits was measured at various stages. In tomato fruits the ACC content was least in fruits harvested 36 days after anthesis, and was greater in fruits harvested at immature or ripening stages, whereas in cucumber fruits it decreased with the advancement of fruit growth.
Propylene was administered to cucumber fruit tissue slices to elucidate whether this analogue of ethylene had any effect on the activity of EFE. After treatment with 1000ppm of propylene for 42 hours, ACC was supplied to the tissue slices. The slices treated with propylene resulted in a greater production of ethylene than the untreated controls.
These results indicate that tomato fruits at ripening stage synthesize a larger amount of ethylene, due to an increase in ACC content and to sufficient activity of EFE. Cucumber fruits at the growing stage produce only a small amount of ethylene, due to a reduced ACC content, in spite of having sufficient EFE activity.