Soil contamination with lead (Pb) represents a common heavy metal stress for cultivated plants. In the current study, effects of Pb stress on wheat (Triticum aestivum) plants were evaluated, and alleviating roles of purslane and chard natural weed extracts were assessed. The results showed that Pb treatment (100 mM) significantly reduced the growth of wheat seedlings and diminished plant yield parameters. Moreover, Pb stress inhibited photosynthetic activity measured as Fv/Fm. The levels of various stress markers increased under Pb stress as was verified by the increased electrolyte leakage, malondialdehyde (MDA) content, H2O2 and .OH radical content. Pb stress increased the activity of peroxidase (POX), catalase (CAT), superoxide dismutase (SOD), as well as raised the content of the antioxidant compound ascorbic acid. A remarkable induction in some genes was reported under Pb stress. The ameliorative role achieved by seed priming of wheat in purslane and chard weed extracts was demonstrated by the increase in growth parameters in seedling and yield stages. In the meantime, the priming treatments increased the Fv/Fm value. In addition, the activities of the antioxidant enzymes POX, CAT and SOD were reduced by seed priming. Data presented in the current work provide strong evidence that natural weed extracts are efficient to alleviate damaging effects of abiotic challenges such as heavy metal stress imposed by high soil Pb concentrations, and thus possibly could represent a valuable ecofriendly and commercial values for plant farmers.
Key words: Triticum aestivum, purslane and chard, heavy metal, lead stress, weed extracts, seed priming, antioxidants
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