Use of persistent analogs of abscisic acid as palliatives against salt-stress induced damage in citrus plants

The effectiveness of several abscisic acid (ABA) analogs as palliatives against salt stress in intact citrus plants has been tested in this work. The effect of ABA, 8'-methylene ABA, 8'-acetylene ABA, ABA methyl ester, 8'-methylene ABA methyl ester, and 8'-acetylene ABA methyl ester on citrus responses to salt stress was studied on 2-year-old grafted plants. Leaf abscission, chloride accumulation, ethylene production, and net photosynthetic rate were the parameters used to characterize the performance of plants under stress. Data indicate that 8'-methylene ABA was the most effective compound in delaying the deleterious effects of high salinity on citrus plants. Its regular application reduced leaf chloride concentration, ethylene production, and leaf abscission. Furthermore, it delayed the depletion of CO2 assimilation under these adverse conditions. Abscisic acid and 8'-acetylene ABA also reduced salt-stress induced injuries in citrus, although to a lower extent. Neither ABA methyl ester nor its 8'-C modified analogs showed biological activity in these assays.