Oxidative stress in herbicide-treated broad bean and maize plants

Treatments of broad bean and maize seedlings with fluometuron, atrazine or rimsulfuron affected some parameters of oxidative stress. Fluometuron significantly reduced activity of Hill reaction (PSII), chlorophyll a+b contents and activity of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco, EC 4.1.1.39) in leaves of both species and significantly increased contents of H2O2, lipid peroxides and carbonyl groups during the whole experiment. There were, moreover, significant inhibitions in activities of superoxide dismutase (SOD; E.C. 1.15. 1.1), catalase (CAT; E.C. 1.11. 1.6), ascorbate peroxidase (APX E.C. 1.11. 1.11) and guaiacol peroxidase (GPX; E.C, 1.11. 1.7). Response to atrazine was, to some extent, similar to fluometuron throughout the entire experiment in broad bean and up mostly to the 12(th) day of the experiment in maize. The herbicide effect was more pronounced in broad bean than maize. These results point to indicate an occurrence of oxidative stress in both species by fluometuron and only in broad bean by atrazine. The increase in H2O2 content accompanied with drop in activities of SOD, CAT and peroxidases indicates a decline in its detoxification rather than increase in its synthesis. On the contrary, rimsulfuron seemed to have no effect on most of the tested parameters although there were transient significant increases in H2O2, lipid peroxides and carbonyl groups as well as activities of SOD, CAT, APX and GPX. These findings, based on the recovery in oxidative stress, indicate that fluometuron is involved in oxidative stress generation in both species but atrazine Only in broad bean while rimsulfuron is not in both species.