FIGURE 9.

Effects of heat priming and post-anthesis heat stress on the superoxide anion radical (${\mathrm{O}}_{\mathrm{2}}^{\mathrm{•–}}$) production rate (A,B), malondialdehyde (MDA) content (C,D), superoxide dismutase (SOD) activity (E,F), peroxidase (POD) activity (G,H) in flag leaves of Yangmai 18 and Yannong 19 at the grain-filling stage from 2016 to 2017. NN refers to no heat priming + no heat stress at the grain-filling stage (control); NH refers to no heat priming + heat stress at the grain-filling stage; P_SH refers to heat priming at the stem-elongation stage + heat stress at the grain-filling stage; P_BH refers to heat priming at booting + heat stress at the grain-filling stage; P_AH refers to heat priming at anthesis + heat stress at the grain-filling stage. The data are means ± SE (n = 3). Lowercase letters refer to significant differences between the treatments (P < 0.05). Whiskers above the bars indicate the standard error.