Phenotypes and survival rates of 10-day-old Arabidopsis kai2 mutant and WT plants grown for 5 d under continuous heat stress (40°C) and control (23°C) conditions. (A) Phenotypes of the investigated genotypes after 5-day exposure to control (upper panel) and heat stress (lower panel) conditions. (B) Thermography images of the two genotypes after 24-h exposure to control (upper panel) and heat stress (lower panel) conditions. (C) Survival rates (%) of the investigated genotypes after 5-day exposure to heat stress. Values represent means and SDs calculated from three independent replicates (n = 3, 45 plants per genotype per replicate). Asterisks indicate a significantly higher survival rate of WT compared with the kai2 mutant plants (***P < 0.001; Student’s t-test). (D) Leaf surface temperatures of the two genotypes under control (WT_C and kai2_C), and 6- and 24-h heat stress (WT_H6, kai2_H6, WT_H24 and kai2_H24, respectively) conditions as calculated from three replicates (n = 3, 15 plants per genotype per replicate). Different letters indicate significant differences between the kai2 and WT plants in response to heat stress at P < 0.05, using analysis of variance (ANOVA) with post hoc Tukey Honestly Significant Difference (HSD) test. (E) EL percentages of the kai2 and WT plants after 6- and 24-h heat stress treatments. Data represent the means and SDs calculated from three replicates (n = 3, 15 plants per genotype per replicate). Asterisks indicate significantly higher EL% of the kai2 mutant compared with WT plants (**P < 0.01; Student’s t-test). ns, nonsignificant.