Endogenous gibberellins and abscisic acid-metabolites: their role for during flower bud abscission and embryo development in pistachio

Abstract

This study was carried out to determine the effect of different growth periods and possible role of gibberellins (GAs) andabscisic acid (ABA) metabolites on the alternate bearing of the pistachio (Pistacia vera L.). For this purpose, the levels of GAs and ABAin the panicles and nuts of the trees during flower bud abscission and embryo development were analyzed in the crop “on” year. Theresults showed significant differences and changes in ABA and GAs among the tissues and periods investigated. Dihydrophaseic acid(DPA) and GA19 were the dominant ABA and GAsin the pistachio concentrates analyzed in this work, respectively. The nut sampleshad higher values for almost all ABA metabolites and GAs than panicles. The ABA content of the panicles and nuts increased rapidlyduring flower development (35 DAFB) prior to flower bud abscission while the initial decrease in the ABA content remained constantat a relatively low level at the end of June (intense flower bud abscission), with the minimum levels being obtained during embryodevelopment stage (65 DAFB). However, on day 65 after full flowering, GA19 and GA44 were found to have increased. The plant growthregulator profiles of the pistachio showed delayed spikes in GA and ABA groups indicating that there is a hormone requirement duringflower bud abscission and embryo development in pistachio. As a results, GA and ABA metabolites produced in different organs play animportant role in the control of pistachios during embryo development and flower bud abscission.