4.2 Thermotolerance assay
Seeds were sown on 1/2 MS plates with 0.70% agar and stratified at 4℃ for 3 d. Then the plates were moved to the long day growth chamber (16-h light and 8-h dark, 120 μmol.m–2·s–1, LED fluorescent tube) at 22℃. Priming treatment was performed as described previously with subtle modifications(Brzezinka et al., 2019). Briefly, Seedlings grown in a chamber for 5 d were subjected to priming protocol: 37°C for 60 min, followed by 120 min at 22°C, then 45 min at 44°C followed 2 d at 22℃, then seedlings were subjected to 44°C for 90 min in a constant-temperature incubator for HS triggering. For the unprimed group, triggering was applied to seedlings grown at 22°C for 7 d. After triggering, seedlings were transferred to normal growth conditions until analysis.