The Hormone Content of Ripening Grape Berries and the Effects of Growth Substance Treatments

Berries on field-grown Vitis vinifera cv. Doradillo were treated at different times during stage II with benzothiazole-2-oxyacetic acid or 2-chloroethylphosphonic acid, and measurements were made of their growth and hormone content. The concentration of ethylene was low during stage II and declined as berries ripened. Both 2-chloroethylphosphonic acid and benzothiazole-2-oxyacetic acid caused increases in ethylene concentration, yet they had varying effects on ripening: the former applied at the start of stage II and the latter applied 1 week before the end of stage II delayed ripening, while 2-chloroethylphosphonic acid applied at the end of stage II hastened ripening.The abscisic acid content of berries increased as they ripened, and the effects of 2-chloroethylphosphonic acid and benzothiazole-2-oxyacetic acid on abscisic acid levels were correlated with the effect of these compounds on ripening. The roles of abscisic acid and ethylene in the regulation of the ripening of grapes are discussed.