In vitro studies of ABA and ethephon induced abscission in olive organs

Detached reproductive shoots of olive (Olea europaea L. cv. Konservolia) we re basally fed continuously with solutions of 25 ppm (0.10 mM) or 50 ppm (0 .19 mM) abscisic acid (ABA) and 25 ppm (0.17 mM) or 50 ppm (0.32 mM) (2-chl oroethyl)phosphonic acid (ET) individually or in combination, four weeks be fore full bloom. Leaf and flower abscission were counted along shoots at 24 h intervals over a 120 h period. A lag period of 72 h was needed for the f irst abscission of both organs in the control (water). By 120 h leaf abscis sion in control remained low (about 15%), although flower abscission was fo ur-fold higher (about 60%). All treatments with growth regulators reduced t he lag period for the first leaf and flower abscission to 48 h. Individual ABA or ET applications resulted in a very low leaf abscission at 48 h treat ment. The effect was increased by increase in both concentration and applic ation period, attaining maximum values after 120 h (60-95%). The combinatio n of ABA and ET at both levels showed a synergistic effect on leaf abscissi on, resulting in a considerable abscission at 48 h acid an almost complete leaf shedding even after 96 h application time (90-95%). After 48 h treatme nt, a separation layer was developed in petioles of seventh node sections o nly in the combined application of ABA and ET at 50 ppm level. ET was conti nuously more effective than ABA on olive flower abscission. Both concentrat ions of individual ABA treatments showed similar effects on olive flowers, over all the examined periods. The combined ABA and ET applications were mo re effective than single ones on flower abscission. Profiles of leaf and fl ower abscission showed decreasing trends from the basal to the upper nodes of shoots in all treatments, but the effect of combined applications extend ed with higher rates to the top of the shoot. Statistically significant dif ferences in leaf and flower abscission were found among treatments, as well as among different node positions over all the experimental time. Our resu lts showed the combination of ABA and ET to be very effective for olive lea f abscission.