Biological responses of a non‐target aquatic plant (Nasturtium officinale) to the herbicide,tribenuron‐methyl

To assess its response to the herbicide, tribenuron‐methyl, samples of Nasturtium officinale were exposed to 0, 0.01, 0.05, 0.1, and 0.5 mg L^?1 of tribenuron‐methyl for 1, 2, 4 and 7 days. The influence of this herbicide on the relative growth rate, electrolyte leakage, lipid peroxidation, photosynthetic pigmentation, protein content, and performance of anti‐oxidant enzymes, such as superoxide dismutase (SOD), catalase, and ascorbate peroxidase (APX), was examined. The results indicated that tribenuron‐methyl, applied at 0.5 mg L^?1, affected plant growth negatively. It also was determined that chlorophyll a is the most responsive photosynthetic pigment to tribenuron–methyl exposure. Under stress conditions, the anti‐oxidant enzymes were up‐regulated compared to the control. The SOD activity was significantly stimulated, while the activity of APX was inhibited. A significant correlation was found between lipid peroxidation and SOD activity. The exposure period and herbicide concentration had significant effects on the biological responses against tribenuron‐methyl stress. These results may be useful for clarifying the effect of herbicides on non‐target aquatic plants.