ABSCISIC-ACID EFFECTS ON ETHYLENE PRODUCTION AND RESPIRATION RATE IN DETACHED APPLE FRUITS AT DIFFERENT STAGES OF DEVELOPMENT

Apple fruits (Malus domestica. Borkh. c.v. Red Winesap) collected at d ifferent stages of development (92, 120 and 147 days after full bloom, a.f.b.) were treated by injection with 1 mM ABA. This treatment induc ed an increase in respiration and ethylene production compared to cont rols treated with water or untreated, and ripening was advanced. This effect was especially pronounced in the youngest fruits (92 days a.f.b .) in which the control did not show any change related to ripening du ring three weeks. Treatments by infiltration gave rather similar resul ts although less pronounced. These results suggest that the capacity o f the fruit to produce ethylene and to ripen is related to the ABA con tent. ABA treatment is able to induce ripening even in rather young fr uits.