Sodium hydrosulfide alleviates cadmium toxicity by changing cadmium chemical forms and increasing the activities of antioxidant enzymes in salix

Cadmium (Cd) is a highly toxic element for plant. In order to reveal the effects of NaHS on Cd uptake, physiological and molecular responses of salix to Cd toxicity, NaHS-mediated hydroponics of salix under Cd stress was performed. The addition of NaHS reduces the salix biomass reduction caused by Cd poisoning. NaHS did not obviously reduce the total Cd level absorbed by salix, but significantly reduced the soluble Cd fractions and increased the insoluble Cd fractions in salix leaves and roots. NaHS reduced the distribution of Cd in organelles and vacuoles and increased the distribution of Cd in the cell wall of salix leaves and roots. NaHS promotes the level of antioxidant enzyme activities and gene expression of salix, and reduces the accumulation of MDA and H2O2 caused by Cd. NaHS increases the content of GSH and endogenous H2S in salix leaves and roots. The addition of NaHS can reduce the toxicity of Cd to salix without obviously reducing the Cd uptake by salix, thus improving the application of salix in phytoremediation to Cd.