Exogenous salicylic acid alleviates halosulfuron-methyl toxicity by coordinating the antioxidant system and improving photosynthesis in soybean (Glycine max Merr.)

Abstract

Halosulfuron-methyl (HSM) is an herbicide widely used in agricultural production, but it could affect the growth of non-target plants, induce plants produce excessive reactive oxygen species, disturb photosynthesis, and cause severe abiotic stress. In this study, the response of soybean seedlings to HSM stress and the mitigation effect of exogenous salicylic acid (SA) on HSM toxicity were studied. In comparison to HSM alone, SA (0.1 mM) pretreatment in combination with HSM (0.005, 0.05, 0.5 mg/L) promoted seed germination, root and shoot growth, and significantly improved the dry weight of root and shoot. The combination treatment also led to significant improvement in chlorophyll fluorescence parameters, gas exchange parameters and photosynthetic pigments content compared with HSM alone. Malondialdehyde, superoxide radical (O2·−) and H2O2 contents under HSM treatment were significantly reduced by SA pretreatment. In addition, the activities of the superoxide dismutase, peroxidase and catalase were down-regulated by SA pretreatment under HSM treatment, but the activities of ascorbate peroxidase (APX) and glutathione reductase (GR) were up-regulated. These results showed that SA could positively mitigate HSM toxicity by increasing APX and GR activities and protecting the photosynthetic system.