Hydrogen Peroxide Alleviates Hypoxia during Imbibition and Germination of Bean Seeds ( Phaseolus vulgaris L.)

Abstract

Bean seeds (Phaseolus vulgaris L. cv. Tendergreen) were imbibed in water to examine the effects of hypoxia during imbibition and subsequent germination. Hypoxic conditions occurred when seeds were imbibed in water for 24 h or longer and resulted in severe reduction of hypocotyl elongation and stem growth during subsequent germination under non-limiting oxygen condi-tions. Under continued hypoxic conditions, bean seeds failed to germinate, however, this was re-versed in the presence of hydrogen peroxide (20 mM) in the medium. Furthermore, imbibition of seeds in the presence of hydrogen peroxide overcame the adverse hypoxic effects on hypocotyl elongation and stem growth. Exogenous hydrogen peroxide increased the dissolved oxygen levels in the germinating medium, and catalase and transition metal ions such as Fe 2+ , Cu 2+ and Mn 2 helped to facilitate the production of oxygen from hydrogen peroxide. In these catalysts, catalase played a major role in the decomposition of hydrogen peroxide as demonstrated by the use of a catalase inhibitor, 3-amino-1, 2, 4-triazole, which reversed the positive effects produced by hy-drogen peroxide on germination of seeds under hypoxic conditions. The results show that imbibi-tion is sensitive to oxygen deficits which affect subsequent hypocotyl growth and seedling per-formance. The adverse effects of hypoxia on germination of bean seeds can be overcome by ex-ogenous hydrogen peroxide.