Silicon alleviates salt stress-induced potassium deficiency by promoting potassium uptake and translocation in rice (Oryza sativa L.)

Under salt stress, plants suffer from potassium (K) deficiency caused by excess salts in growth substrate. Silicon (Si) can promote K status in many plant species under salt stress, however, the underlying mechanisms remain unclear. In this study, we assessed the effects of Si on K homeostasis in rice under salt stress and investigated the mechanisms behind using two low-Si rice mutants (lsi1 and lsi2) and their wild types (WTs). After five days' treatment with Si, plant growth was improved and salt stress-induced K deficiency was alleviated in WTs but not in mutants. Simultaneously, Si significantly enhanced K accumulation content, K uptake index and shoot K distribution rate in WTs but not in mutants. Besides, Si enhanced K concentration in xylem sap in WTs but not in mutants. Scanning ion-selected electrode technique (SIET) analysis showed net K influx rate was raised by Si addition under salt stress in WTs but not in mutants. Moreover, Si up-regulated the expression of genes responsible for K uptake (OsAKT1 and OsHAK1) and xylem loading (OsSKOR) in WTs but not in mutants. Overall, our results strongly indicate that Si can improve K uptake and translocation by up-regulating the expression of relevant genes, thereby promoting K status and alleviating salt stress in rice.