Hydrogen peroxide (H2O2) analysis
To observe H2O2 production in leaf tissues of the sitl1 and WT, histochemical DAB staining was conducted as described (Hacham et al., 2011). After salinity stress treatment for 1 weeks, detached leaves were incubated in DAB (3,3′-diaminobenzidine) staining solution at 25 °C for 5 h. Bleaching solution was used to remove chlorophylls of the leaf samples and images were captured by light microscopy (DM500, Leica, Germany). H2O2 content in root and leaf tissues was quantitated as described in Gay and Gebicki (2012). The absorbance was measured at 560 nm using a SPECTROstarNano. A standard curve of H2O2 using linear regression analysis was used to calculate the sample H2O2concentration.