Figure 4.

Melatonin decreased the hydrogen peroxide level induced by cadmium stress and prevented the toxicity of exogenous hydrogen peroxide to the root. (A) In situ detection of hydrogen peroxide after cadmium (0.2 mM), melatonin, or cadmium + melatonin treatment. (B,C) Hydrogen peroxide content was analyzed at 2 d after cadmium (0.2 mM), cadmium + melatonin treatments, separately in the shoot and root (n = 5). (D) Root growth at 2 d after 0.3% H₂O₂, or 0.3% H₂O₂ + melatonin treatment. (E) Relative H₂O₂ content in the culture medium at 2 d after treatment (n = 3). (F,G) Plant height and adventitious root number were separately calculated at 5 d after treatment (n = 20). For determination of plant fresh and dry weight, three seedlings were mixed as one sample. Values are mean ± SE. Means with different letters (a, b and c) are significantly different at p < 0.05 using Tukey’s test. Bars = 1 cm.