Superoxide ions (O^2-) and hydrogen peroxide (H₂O₂) are the reactive oxygen species (ROS) that play a significant role in regulation of many plant processes. The level of O^2- ions is determined qualitatively using nitrobluetetrazolium (NBT) assay while the H₂O₂ is qualitatively estimated using 3,3-diaminobenzidine (DAB) and 2’,7’-dichlorodihydrofluorescein diacetate (H₂DCFDA) assay. Further the aqueous content of H₂O₂ is estimated quantitatively using ferrous oxidation-xylenol orange (FOX) assay.