Time course of antioxidant enzymes in the paraquat-resistant and tolerant Heary fleabane (Conyza bonariensis) biotypes in response to ozone exposure and paraquat application

In order to investigate the molecular mechanism of oxidative stress resistance due to either paraquat or ozone in plants, two paraquat biotypes (resistant and sensitive) of Conyza bonariensis were used. We monitored some biochemical parameters (total peroxydase, guaiacol peroxydase, ascorbate peroxydase and superoxyde dismutase) following a paraquat fumigation (0.001%, 4 hours), and a pulse of elevated ozone (200 ppb, 5 hours) or intermediate ozone (50 ppb, 4 hours). The mechanisms of protection induced by ozone exposure were not similar to the pathway leading to paraquat resistance, due to a different stimulation response system to antioxidants.