Silicon enhances the submergence tolerance of rice by regulating quiescence strategy and alleviating oxidative damage

The safety of rice production under submergence is one of the research hotspots worldwide. Although the effects of silicon (Si) on enhancing plant stress tolerance have been widely investigated, the underlying mechanisms mediated by Si under submergence remains poorly understood. In this study, wild type (WT) and Si-defective mutant (lsi1) rice were chosen to investigate the mechanisms of Si-mediated rice resistance to submergence. Our results showed that Si addition effectively mitigated oxidative damages under submergence by reducing the content of hydrogen peroxide (H₂O₂) and superoxide (O₂^.-) in WT rice plants. Moreover, Si treatment increased rice yield by 21.5% for WT rice under submergence. The application of Si significantly inhibited the elongation and internode length in WT rice under submergence, through the synergistic regulation of endogenous hormones ethylene (ET), gibberellic acid (GA) and jasmonic acid (JA). Further investigation showed that the ethylene-responsive factor (ERF) SUB1A gene was expressed under submergence in WT and lsi1 rice, but Si addition did not influence the expression of SUB1A. Interestingly, exogenous Si down-regulated the relative expression levels of Si transporter genes Lsi1 and Lsi2 in WT rice roots by 51.7% and 48.0%, respectively. However, the physiological characteristics and genes expression of lsi1 rice were not affected by Si application regardless of submergence. The present study indicated that Si enhances the submergence tolerance and reduce the adverse effects of yield loss through the removal of reactive oxygen species and the adjustment of quiescence strategy.