Fruit Set in Grape Vines: The Mechanism of the CCC Effect

SummaryThe treatment of grape inflorescences with CCC before anthesis increased fruit set, but it did not increase the fertilization of ovules. CCC applied to different parts of a shoot had effects remote from the point of application. The effects included reductions in leaf expansion, internode elongation and rate of leaf emergence. The size of the effects was directly correlated with the amount of tissue treated and was inversely correlated with the amount of fruit set. If shoot tips were removed, CCC treatment was without effect on set. It has not been possible to link the data with changes in chlorophyll concentration. It is suggested that the effect of CCC on fruit set is due to a correlated inhibition of shoot growth whereby organic nutrients are diverted to the developing ovaries.