Review Article
Chaudhuri A, Singh KL and K
Abstract
Regulation of seed germination is quite complex and is further complicated by interaction of hormones like gibberellin (GA), abscisic acid (ABA) and ethylene. Moreover, the involvement of reactive oxygen species (ROS) in hormone signaling for such regulation is still less understood. The aim of the present study was to explore the interactive role of GA, ABA and ethylene and possible involvement of ROS in mediation of hormone action during seed germination of Vigna radiata. Seeds of V. radiata were germinated in presence of hormones, their biosynthesis or action inhibitors and in combinations with hydrogen peroxide and at intervals germination percentages were determined. Treated seeds were also tested for production of superoxide by NBT staining and analysed for NADPH oxidase (NOX) activity by in-gel assay. ABA and paclobutrazole (GA biosynthesis inhibitor) inhibited germination of non-dormant V. radiata seeds. GA recovered germination from inhibition by Ag+ (ethylene action inhibitor) whereas paclobutrazole-induced inhibition could not be recovered by ethylene. But ethylene could recover significantly ABA- inhibited germination. Treatment with H2O2 rescued germination from inhibition by ABA, paclobutrazole and Ag+ with efficiency in the order ABA> Ag+>paclobutrazole. Superoxide (O2.-) production, as revealed by NBT staining, was found mostly in the apical part of the axis in control and ethylene treated seeds and to a less extent in GA treated seeds while almost no stain was found in case of treatments with ABA, Ag+ and paclobutrazole. In-gel assay of NOX activity showed three bands in control and in case of treatments with ethylene, GA and fluridone while intensity became less for one or more bands in case of paclobutrazole, ABA and Ag+ treatment. It appears that ethylene and ABA is antagonistic to each other while GA is partially independent in regulating germination of Vigna radiata seeds through mediation of ROS.