Reactive oxygen species (ROS) are produced in both stressed and unstressed cells. Resistance to environmental and chemically induced oxidative stresses has been shown to be associated with changes in catalase (CAT), peroxidase (POD) and superoxide dismutase (SOD) activities. Catalase and superoxide dismutase are major protectants against accumulation and toxicity of hydrogen peroxide (H2O2). We evaluated alterations in CAT and SOD activities in two species of Celocia vegetables namely Celocia argentea (C.a) and Celocia argentea pigmented (C.a p) when paraquat (PQ) was used at the manufacturer’s field recommended concentration (0.5mM), over a period of four weeks. A statistically significant (p < 0.05) increase in the activities of SOD and CAT was observed in the two vegetables during the treatment period when compared with the control. However, the SOD activity in C.a p was higher than that of C.a at the end of four weeks. Although, the treated vegetables showed some signs of wilting at the early stage of growth, no apparent necrotic lesion was observed. The studies suggested that apart from the inherent/endogenous protective mechanism probably via antioxidant vitamin(s) in these vegetables, presence of protective antioxidant enzymes maybe the primary basis for the paraquat mediated oxidative stress withholding capacities in these vegetables.
