Ion leakage assay

The ion leakage of treated leaf samples was measured according to a previous report with some modifications (Zhu et al., 2017). Briefly, five leaf discs with a diameter of 5 mm were collected and floated on 5 ml of double-distilled water at 25 °C for 3 h, then the sample conductivity was measured and recorded as value A. Isolated leaf discs were treated at 95 °C for 25 min, and the value B of the corresponding samples were further measured when the solution cooled to 25 °C. The final conductivity was expressed as a percentage of the ion leakage=(value A/value B)×100.