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(NO3)(2) concentrations. High concentrations of lead and exogenous H2O2 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 H2O2 generation was observed in germinating seeds exposed to lead. Analysis using fluorescent dye 2',7'-dichlorodihydrofluorescein diacetate showed significantly increased H2O2 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 H2O2 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. (c) 2010 Elsevier Inc. All rights reserved.