The Silicon Effects on Antioxidant System of Wheat Cultivars under Pb Stress

Pb poses a major threat to plant growth and silicon can reduce its toxicity. This work was conducted hydroponically as a completely randomized factorial design to study the effect of Si (70 and 140 ppm) on Triticum aestivum cultivars Chamran and Shiroudi under Pb stress (150 ppm). Pb caused significant increases in the H2O2, free amino acids and proline contents of wheat cultivars and MDA content of cv. Chamran. Furthermore, Pb stimulated the activities of SOD and APX in cv. Chamran and POD in cv. Shiroudi. Si application significantly increased the free amino acid content of cultivars and proline content of cv. Chamran in absence of Pb. The protein content of wheat cultivars significantly increased at 70 ppm of Si in absence of Pb and at both levels in presence of Pb. In cv. Chamran, Si application significantly decreased the H2O2 content and the activities of SOD, POD and APX at both levels, free amino acids and proline contents at 70 ppm and MDA content at 140 ppm in presence of Pb. In cv. Shiroudi, Si application significantly decreased the proline content at both levels, H2O2 and free amino acids contents at 70 ppm and MDA content at 140 ppm.