Fig 3. Effect of melatonin addition on hydrogen peroxide (H₂O₂) content (A) and superoxide anion (O2·-) production rates (B) of soybean leaves under osmotic stress.

WW: half-strength Hoagland’s nutrient solution alone; WW+ML: half-strength Hoagland’s nutrient solution and 100 μmol/L melatonin by leaf; WW+MR: half-strength Hoagland’s nutrient solution and 100 μmol/L melatonin by root; PEG: half-strength Hoagland’s nutrient solution plus 15% PEG 6000 treatment; PEG+ML: half-strength Hoagland’s nutrient solution plus 15% PEG 6000 treatment and 100 μmol/L melatonin by leaf; PEG+MR: half-strength Hoagland’s nutrient solution plus 15% PEG 6000 treatment and 100 μmol/L melatonin by root. The data represent the mean ± SE of five replicate samples. * indicate significant differences according to Duncan’s multiple range test (P<0.05).