Hydrogen Sulfide Alleviates Aluminum Toxicity in Germinating Wheat Seedlings

Abstract

Protective role of hydrogen sulfide (H₂S) on seed germination and seedling growth was studied in wheat (Triticum) seeds subjected to aluminum (Al³⁺) stress. We show that germination and seedling growth of wheat is inhibited by high concentrations of AlCl₃. At 30 mmol/L AlCl₃ germination is reduced by about 50% and seedling growth is more dramatically inhibited by this treatment. Pre-incubation of wheat seeds in the H₂S donor NaHS alleviates AlCl₃-induced stress in a dose-dependant manner at an optimal concentration of 0.3 mmol/L. We verified that the role of NaHS in alleviating Al³⁺ stress could be attributed to H₂S/HS⁻ by showing that the level of endogenous H₂S increased following NaHS treatment. Furthermore, other sodium salts containing sulfur were ineffective in alleviating Al³⁺ stress. NaHS pretreatment significantly increased the activities of amylases and esterases and sustained much lower levels of MDA and H₂O₂ in germinating seeds under Al³⁺ stress. Moreover, NaHS pretreatment increased the activities of guaiacol peroxidase, ascorbate peroxidase, superoxide dismutase and catalase and decreased that of lipoxygenase. NaHS pretreatment also decreased the uptake of Al³⁺ in AlCl₃-treated seed. Taken together these results suggest that H₂S could increase antioxidant capability in wheat seeds leading to the alleviation of Al³⁺ stress.