Sulfur nanoparticles improved plant growth and reduced mercury toxicity via mitigating the oxidative stress in Brassica napus L.

Experiments were conducted to determine the effects of sulfur nanoparticles (SNPs) on alleviating mercury (Hg) toxicity and accumulation in Brassica napus L. in MS medium. The results demonstrated that 10 mg/L Hg severely inhibit brassica seedlings growth, whereas the addition of 300 mg/L SNPs alleviated Hg toxicity, and dry weight were improved by 42.4% (shoot) and 37.8% (root) compared to 10 mg/L Hg treatment alone. SNPs application decreased Hg accumulation in roots and shoots by 6-10 folds. Comparatively, the effect of corresponding bulk sulfur particles (BSPs) and sulfate as ionic compound for counteracting Hg toxicity and accumulation was less pronounced than SNPs treatment. Co-exposure of SNPs along with Hg also alleviated the Hg-induced oxidative stress as the MDA and H2O2 contents, antioxidant enzymes activities (SOD, POD, APX and GST) and glutathione (GSH) content in roots and shoots were decreased relative to Hg treatment alone. The macro (K, Ca, P, Mg) and micronutrients (Zn, Mn, Fe) concentrations in roots and shoots were elevated considerably by SNPs co-exposure compared to plants exposed to Hg only. Further, the expression of selected genes encoding the antioxidant enzymes and nutrient transporters also showed changes similar to the physiological and biochemical parameters. Our results showed that SNPs play a significant role in the decreasing Hg accumulation, counteracting the Hg toxicity, and enhancing plant biomass and nutrients accumulation in B. napus. These findings will be helpful in developing strategies to decrease heavy metals contamination in the food chain as well as for phytoremediation applications.