Figure 1.

Effect of H₂O₂ on the chilling tolerance of cucumber seedlings. (a) Phenotype characterization of cucumber seedlings pretreated with H₂O₂ or deionized water under chilling stress (8/5 °C) for 48 h. Deionized water-treated seedlings before chilling stress were used as the control. The experiments were repeated three times with similar results. A typical picture is shown here. (b) Image of F_v/F_m and Φ_PSII in seedlings before (control) and after chilling stress for 24 h. The false color code depicted at top of the image represents the degree of photoinhibition at PSII. (c) CI of seedlings before (control) and after chilling stress for 72 h. (d) EL of seedlings before (control) and after chilling stress for 48 h. (e) Pn of seedlings before (control) and after chilling stress for 24 h. Two-leaf stage cucumber seedlings were foliage sprayed with 0, 0.01, 0.1, 1.0, 2.0 and 3.0 mM H₂O₂ solution for 24 h and subsequently were exposed to 8/5 °C (day/night). The data represent the mean ± SD of three biological replicates. Different letters indicate significant differences (p < 0.05), according to Duncan’s new multiple range test.