Figure 2.

Accumulation of hydrogen peroxide and superoxide anion as affected by melatonin in poplar leaf discs exposed to MV. (A) H₂O₂ level; (B) O₂⁻ level. Poplar leaf discs were pretreated with 150 μM melatonin in the dark for 12 h, and then, leaf discs were exposed to 50 μM methyl viologen in the light for 24 h. Leaf discs were collected at 0, 12 and 24 h following MV treatment. The values presented are means ± SDs (n = 3). Different letters indicate significant difference at p < 0.05 among treatments.