Olive Organ Abscission: Fruit and Leaf Response to Applied Ethylene

Abstract

Fruit-bearing olive ( Olea europaea L.) shoots were exposed to more than 100 ethylene (C 2 H 4 ) treatments to determine if C 2 H 4 -induced abscission varied between leaves and fruits in response to manipulation of treatment concentration, duration, and total amount of exogenous C 2 H 4 . Nearly three-quarters of the treatments induced greater fruit abscission than leaf abscission on a percentage basis. The potential for optimization of C 2 H 4 -induced fruit abscission relative to leaf abscission was examined by calculating the fruit-to-Ieaf (F:L) abscission ratio. Of the treatments inducing at least 75% fruit abscission, the dose range of 150 to 370 μmol C 2 H 4 gave ratios up to 13.3; however, results were highly variable and closely dependent on the interaction of concentration and duration. Response surfaces were created to depict this interaction. Desirable levels of fruit abscission occurred at durations > 30 hr and concentrations > 2 to 3 μl·liter −1 . However, excessive leaf abscission occurred at durations of 24 to 48 hr, depending on concentration. Acceptable F:L ratios were found for about 30% of the surface, with the highest ratios occurring for treatments of 3 to 5 μl·liter −1 for 28 to 34 hr.