Evaluation of morpho-physiological and antioxidant responses of Moringa oleifera Lam. to lead exposure

Abstract

BackgroundLead (Pb) toxicity affects growth, mineral nutrient homeostasis, water status and yield of plants. To avoid Pb entry into humans via the food chain, remediation of contaminated sites is required. This study was focused on the evaluation of effects of Pb on Moringa oleifera, an efficient metal accumulator plant, for the prospective use in Pb mitigation from the soil. MethodsM. oleifera seedlings (10-day old) were treated with different concentrations of Pb (1, 2, 3 and 5 mM) and morphological,biochemicaland molecular parameters and Pb accumulation were analysed at 10, 20 and 30 days. ResultsThe results showed high Pb uptake by plants in a concentration- and duration-dependent manner. The maximum Pb concentration was found to be 500 mg kg−1in roots and 224 mg kg−1 in shoots, respectively at 5 mM Pb after 30 days. In response to Pb accumulation, plants depicted significant increase in the level of proline (0.49 µmol g–1 FW), polyphenol (75.83 mg g–1 FW), and metallothionein protein (93.55 µmol g-1 × 10−3). In addition, the activity of antioxidant enzymes (ascorbate peroxidase:APX, catalase:CAT and glutathione reductase:GR)was also enhanced in Pb treated plants as compared to that of control plants. The expression of genes of enzymes (APX and CAT) was also up-regulated. ConclusionIt was concluded from the present results that M. oleifera is a Pb tolerant plant species with a significant capacity for Pb accumulation.Thus, this plant can be used for plantation at Pb-contaminated sites for restoration purposes.