Nitric oxide production and antioxidants responses in maize under lead stress

Lead pollution is an important issue in the world. In this research, maize plants were treated with different concentrations of Pb (0, 0. 25, 0.75, 1, 1.5, 2.5 and 5 mM) as lead (II) nitrate for 10 days. The results showed that an increase in lead concentration leads to a reduction in growth, chlorophyll a and b content and an increase in oxidative damages. Application of Pb caused a progressive increase of hydrogen peroxide content, which was followed by a significant level of lipid peroxidation. These changes were accompanied by an increase in nitric oxide content at the low and its reduction at the high concentrations of Pb. The small increase in the generation of hydrogen peroxide and nitric oxide are envisaged as messengers in signaling pathways that may act in triggering defense functions to detoxify lead. Therefore, plant stress tolerance variables, including proline, ascorbic acid, flavonoids and anthocyanins content and activity of antioxidant enzymes, enhanced under different lead applications.