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

摘要

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_2O_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_2O_2 generation was observed in germinating seeds exposed to lead. Analysis using fluorescent dye 2',7'-dichlorodihydrofluorescein diacetate showed significantly increased H_2O_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_2O_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.