Spermidine enhanced the antioxidant capacity of rice seeds during seed aging

Seed aging is a problem during long-term seed storage, affecting the commercial and germplasm value of seeds. In this study, a widely cultivated rice (Oryza sativa L.) cultivar, Huanghuazhan, was used to investigate the effects of exogenous spermidine (Spd) on accelerated aging (AA). The results showed that the speed of germination and the activities of catalase (CAT), ascorbate peroxidase (APX) and β-amylase were reduced by AA, and more H₂O₂ accumulated in aged seeds than in normal seeds. As compared with aged seeds pretreated with water, seed vigor and the gibberellic acid (GA) content in aged seeds pretreated with Spd were increased by 47% and 17%, respectively. Furthermore, antioxidant enzyme activity and related gene expression were also higher in aged seeds pretreated with Spd. It is speculated that CAT and APX are the two primary enzymes involved in the effects of Spd to AA. These results suggest that the adverse effect of AA stress on seeds may be partially alleviated by the application of exogenous Spd, which may affect the scavenging of reactive oxygen species.