Promotion of Ethylene Evolution and Fruit Abscission in the Olive by 2-Chloroethanephosphonic Acid and Cycloheximide1

Abstract

Abstract Applications of 2-chloroethanephosphonic acid (Ethrel) at 2,250 ppm to olive (Olea europaea L.) trees under warm, low humidity conditions caused a considerable reduction in fruit removal force along with marked increases in leaf abscission and in ethylene evolution from both leaves and fruit. The addition of urea at 1.35% to the spray formulations caused a strong increase in ethylene production and in abscission effects. Definite cultivar differences appeared in response to Ethrel. An Auxin, NAA, blocked Ethrel activity, particularly if applied before, or simultaneously with, Ethrel. If applied 2 or 3 days after Ethrel, NAA reduced leaf abscission while maintaining fruit abscission. Rains following shortly after Ethrel application greatly reduced its activity in both ethylene production and abscission induction. Abscission effects from Ethrel were greater under warm than cool conditions. Cycloheximide at 50, 100, and 200 ppm applied during cool, humid weather caused ethylene production from olive leaves and fruits as well as a reduction in fruit removal force and an increase in leaf abscission. However, ethylene evolution and abscission effects were much less than those obtained with Ethrel.