Lead-induced phytotoxicity mechanism involved in seed germination and seedling growth of wheat (Triticum aestivum L.).

The mechanism of lead-inhibitory effects on seed germination and seedling growth was investigated in wheat cv. Xihan 2 subjected to different Pb(NO(3))(2) concentrations. High concentrations of lead and exogenous H(2)O(2) significantly inhibited seed germination and the growth of roots and shoots. Dimethylthiourea, catalase or diphenylene iodonium could reverse lead-inhibitory effects on seed germination. Significant elevated H(2)O(2) generation was observed in germinating seeds exposed to lead. Analysis using fluorescent dye 2',7'-dichlorodihydrofluorescein diacetate showed significantly increased H(2)O(2) level in the root tissue in response to lead treatment. Nitric oxide (NO) donor sodium nitroprusside could alleviate the Pb-inhibitory effects on seed germination and shoot growth, which was blocked by guanylyl cyclase inhibitor methylene blue. Therefore, NADH-dependent generation of extracellular H(2)O(2) is responsible for Pb-inhibitory effect on seed germination, the protection of exogenous NO against lead toxicity involved in seed germination and seedlings shoot growth may be associated with cGMP signaling pathway.