Modulation of growth and oxidative stress by seed priming with salicylic acid in Zea mays L. under lead stress

Lead is an important environmental pollutant, extremely toxic to plants and other living organisms. In the present study, possible ameliorating effects of salicylic acid (SA) were investigated at biochemical levels in maize exposed to lead stress. The elevation in hydrogen peroxide and malondialdehyde contents and the decline in protein thiol (PT) level were revealed under lead stress. The SA pretreatment prevented a lead-induced decrease in chlorophyll and PT contents, as well as an increase in lipid peroxidation and hydrogen peroxide levels. Lead stressed plants which are pretreated with salicylic acid accumulated more ascorbic acid, glutathione and stimulated more antioxidant enzymes activity than plants treated with lead alone. In addition, SA pretreatment of seed enhanced l-cysteine desulfhydrase activity and endogenous hydrogen sulfide content. The results indicate that SA regulates the response of plants to lead stress and suggest hydrogen sulfide as a downstream signal molecule which might be involved in SA-induced lead tolerance.