Superoxide and its metabolism during germination and axis growth of Vigna radiata (L.) Wilczek seeds

摘要

Involvement of reactive oxygen species in regulation of plant growth and development is recently being dem-onstrated with various results depending on the experimental system and plant species. Role of superoxide and its metabolism in germination andaxis growth was investigated in case of Vigna radiata seeds, a non-endospermous leguminous species having epigeal germination, by studying the effect of different reactive oxygen species (ROs) inhibitors, distribution of O_2ˉ and h2O2 and ROs enzyme profile in axes. Germination percentage and axis growth were determined under treatment with ROs inhibitors and scavengers. Localization of O_2ˉ and h2O_2 was done using nitroblue tetrazolium (NBT) and 3,3′,5,5′-tetramethyl benzidine dihydrochloride hydrate (TMB), respectively. apoplas-tic level of O_2ˉ was monitored by spectrophotometric analysis of bathing medium of axes. Profiles of NaDPh oxidase and superoxide dismutase (sOD) were studied by in-gel assay. Germination was retarded by treatments affecting ROslevel except h2O_2 scavengers, while axis growth was retarded by all. superoxide synthesis inhibitor and scavenger prevented h2O_2 accumulation in axes in later phase as revealed from TMB staining. activity of cu/Zn sOD1 was initially high and declined thereafter. superoxide being produced in apoplast possibly by NaDPh oxidase activity is further metabolized to Oh via h2O_2. Germination process depends possibly on Oh production in the axes. Post-germinative axis growth requires O_2ˉ while thedifferentiating zone of axis (radicle) requires h2O_2 for cell wall stiffening.