Fig 4. Effect of melatonin addition on histochemical localization of H₂O₂ (A) by the DAB uptake method and of O2·- (B) by NBT staining at V3 stage during water deficit stress treatment.

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.