The activity of antioxidant enzymes in response to cadmium-zinc interactions (Cd and Zn up to levels of 80 and 800 mg.kg-1, respectively) in Brassica napus cv. Hyola was studied using a factorial greenhouse experiment in a randomized complete block design with three replications. Results indicate that the content of hydrogen peroxide (H2O2) significantly increased with the increased level of Cd at a given level of Zn, particularly at high levels of Zn. However, the H2O2 content at controls and all levels of Cd with low supply of Zn decreased. The results clearly show that with increasing the H2O2 content, the activity of antioxidant enzymes including catalase (CAT), ascorbate peroxidase (APX), glutathione peroxidase (GPX) and glutathione S-transferases (GST), significantly increased. Moreover, the content of H2O2 had a positive relationship with the malondialdehyde (MDA) content. In conclusion, the activity of antioxidant enzymes not only depends on the levels of Cd but also on the level of Zn supplementation. Low levels of Zn improved biochemical activity of Brassica napus under both low and high levels of Cd.
