Hydrogen Sulfide Alleviates Aluminum Toxicity in Germinating Wheat Seedlings

Protective role of hydrogen sulfide (H(2)S) on seed germination and seedling growth was studied in wheat (Triticum) seeds subjected to aluminum (Al(3+)) stress. We show that germination and seedling growth of wheat is inhibited by high concentrations of AlCl(3). At 30 mmol/L AlCl(3) germination is reduced by about 50% and seedling growth is more dramatically inhibited by this treatment. Pre-incubation of wheat seeds in the H(2)S donor NaHS alleviates AlCl(3)-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 Al(3+) stress could be attributed to H(2)S/HS(-) by showing that the level of endogenous H(2)S increased following NaHS treatment. Furthermore, other sodium salts containing sulfur were ineffective in alleviating Al(3+) stress. NaHS pretreatment significantly increased the activities of amylases and esterases and sustained much lower levels of MDA and H(2)O(2) in germinating seeds under Al(3+) 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 Al(3+) in AlCl(3)-treated seed. Taken together these results suggest that H(2)S could increase antioxidant capability in wheat seeds leading to the alleviation of Al(3+) stress.