Changes in the activities of iaa oxidase peroxidase ascorbic acid utilization and in the endogenous level of para magnetic manganese during benzyl adenine induced growth of excised cucumber cucumis sativus cultivar long green cotyledons
Bharti, S.; Laloraya, M.M.
Biochemie und Physiologie der Pflanzen (BPP) 176(5): 447-453
Changes in the activities of IAA oxidase, peroxidase, ascorbic acid utilization (AAU) and in the level of paramagnetic Mn2+ were studied during benzyladenine (BA)-induced growth of excised cucumber cotyledons in the light and in darkness. BA exerts an inhibitory effect on the activities of IAA oxidase, peroxidase and AAU at early times of treatment, the effect being more marked in darkness. Light seems to help recover from the inhibitory effect of BA on the activities measured. Enhancement in the activities of IAA oxidase, peroxidase and AAU at later times suggests that this may not be a direct action of BA but may be due to some secondary reaction triggered by BA or its metabolic products. Cotyledon expansion is a phasic process with respect to the activities measured. Changes in peroxidase activity show close parallelism with changes in the activities of IAA oxidase and AAU suggesting the role of peroxidase in their oxidation. Changes in peroxidase activity show an inverse correlation with the changes in the level of endogenous Mn2+ in BA-treated cotyledons in the light. The absence of similar correlation in BA-treated cotyledons in darkness is primarily due to the absence of chloroplasts and secondly may be due to a paucity of phenolic substances which are largely synthesized in the light. In absence of these phenolic donors peroxidase would be unable to oxidize Mn2+. The shift in the balance of hormones congenial for BA-induced growth is brought about directly by peroxidase which may be independent of endogenous Mn.