The Relationship Between Endogenous Ethylene and Abscission of Mature Apple Fruits1

The changes in ethylene concentration of attached, horticulturally mature ‘Lodi’, ‘McIntosh’ and ‘Golden Delicious’ apples ( Malus domestica Borkh.) were estimated by measuring the ethylene present in a tube sealed over the fruit calyx. Measurements of this gas sample [the equilibrium ethylene concentration (EEC)] were directly proportional to the internal ethylene concentration (IEC) of the fruit. In ‘Lodi’ and ‘McIntosh’, an increase in the EEC preceded abscisision by at least 3 days. The length of time to abscission after increases in EEC were noted was negatively correlated with daily mean temperature in ‘McIntosh’. ‘Golden Delicious’ fruits did not show a relationship between the EEC and abscission. The commercial harvest period of ‘Lodi’ preceded the rise in EEC. In ‘McIntosh’, ethylene accumulation occurred both during and after the commercial harvest.