DROUGHT RESISTANCE, RECOVERY CAPACITY, AND PHYTOHORMONE CONTENT IN POLYPLOID PLUM LEAVES

Changes in water relations and phytohormone content in diploid and tet raploid plum (Prunus salicina Lindl.) trees were studied. Both the wat er content and water-retaining capacity were higher in tetraploid leav es, irrespective of their water regime (dehydrated or dehydrated-rehyd rated). The transpiration rate in tetraploid plant leaves decreased un der drought conditions to a greater extent, but recovered after subseq uent rehydration more rapidly, as compared to diploid plants under the same conditions. The accumulation of abscisic acid (ABA) in water-str essed tetraploid leaves began later, but finally exceeded the ABA cont ent observed for water-deficient diploid leaves. Cytokinin activity in water-deficient tetraploid plants markedly increased, unlike that in diploid plants. It was concluded that the adaptability of tetraploid p lants to varied water supply is higher than that of diploid plants. It was suggested that ABA as well as cytokinins are directly involved in the induction of protective responses under water stress.