Sulphur protects mustard (Brassica campestris L.) from cadmium toxicity by improving leaf ascorbate and glutathione

In a pot-soil culture ameliorative effect of sulphur (S) (0 or 40 mg S kg(-1) soil) on cadmium (Cd) (0, 25, 50 and 100 mg Cd kg(-1) soil)-induced growth inhibition and oxidative stress in mustard (Brassica campestris L.) cultivar Pusa Gold was studied. Cadmium at 100 mg kg(-1) soil caused maximum increase in the contents of Cd and thiobarbituric acid reactive substances (TBARS) in leaves. Maximum reductions in growth (plant dry mass, leaf area), chlorophyll content, net photosynthetic rate (P-N) and the contents of ascorbate (AsA), glutathione (GSH) were observed with 100 mg Cd kg(-1) soil compared to control. The application of S helped in reducing Cd toxicity, which was greater for 25 and 50 mg Cd kg(-1) soil) compared to 100 mg Cd kg(-1) soil. Addition of S to Cd-treated plants showed decrease in Cd and TBARS content in leaves and restoration of growth and photosynthesis through increase in the contents of AsA and GSH. Net photosynthetic rate and plant dry mass were strongly and positively correlated with the contents of AsA and GSH. It is suggested that S may ameliorate Cd toxicity and protects growth and photosynthesis of mustard involving AsA and GSH.