Effects of Fruit Detachment on Ethylene Biosynthesis and Loss of Flesh Firmness, Skin Color, and Starch in Ripening ‘Golden Delicious’ Apples

Abstract

Abstract Prior to 25 Oct., about 4-6 weeks (1983) or 3-5 weeks (1984) after the normal commercial harvest period, 1-aminocyclopropane-l-carboxylic acid (ACC), ethylene-forming enzyme (EFE), and internal ethylene concentration (IEC) in ‘Golden Delicious’ (Malus domestica Borkh.) apples attached to the tree were low. Thereafter, they began to increase rapidly. The increase in both ACC and IEC was earlier in detached preclimacteric fruit than in fruit attached to the tree. The increase of EFE coincided with that of IEC in detached fruit kept at 20°C. Attached fruit subsequently attained a higher level of ACC but a lower level of IEC as compared to the detached fruit. The results suggest that inhibitor(s) supplied from the tree not only delayed the accumulation of ACC in the fruit but also greatly inhibited its subsequent conversion to ethylene. Once the ripening process is initiated, the development of EFE precedes the development of ACC synthesis in both attached and detached fruit. Since attached fruit showed a steady loss of flesh firmness, green skin color, and starch, these changes did not appear to be related directly to the levels of ACC and internal ethylene. Detached fruit stored at 0° accumulated ACC and increased IEC slightly earlier than those stored at 20°. The magnitudes of these increases during subsequent storage at 0° were, however, smaller than those at 20°.