The Role of Ethylene in the Shedding of Red Raspberry Fruit

The production of ethylene by red raspberry (Rubus idaeus L. cv. Glen Clova) fruit increased climacterically during development. The concentration of ethylene within green fruit was low but increased substantially as fruit abscission and ripening commenced. The receptacle contained higher concentrations than the drupelets at all stages measured. In the mature ripening fruit the ethylene concentrations were found to be physiologically significant, and would accelerate the abscission of large green non-abscising fruit if supplied as a fumigant. The addition of ethylene to ripe fruit did not accelerate abscission, probably because saturating levels occurred naturally within these fruit. Reduction of ethylene synthesis rates using the inhibitor of ethylene production aminoethoxyvinylglycine (AVG) reduced the rate of abscission zone weakening which occurs in detached large green fruit. The rate of ethylene production was found to be dependent on the supply of the precursor l-aminocyclopropane-l-carboxylic acid (ACC). This only accumulated to any extent in those ripe fruit with high rates of ethylene production.