Alleviation of nickel toxicity by molybdenum in wheat

Heavy metal contamination in soil adversely affects wheat productivity. Trace amounts of nickel (Ni) and molybdenum (Mo) are required in the soil for plant metabolism and growth. At high concentrations, Ni is strongly toxic to acidic plants. Present study investigated the effects of Ni (25–200 µM) and combination of Ni (100 µM) with Mo (0.5; T₄ and 2 µM; T₅) on antioxidative parameters under acidic conditions (pH 5.0) using Triticum durum var. HI8737 seedlings. A supply of 25–200 µM NiCl₃ resulted in a significant reduction of fresh tissue weight, which was more substantial for the former. Furthermore, Ni treatment led to enhanced oxidative stress, as reflected by increased MDA and H₂O₂ levels in the tissue. In addition to CAT, antioxidant enzymes respond well to stress, up to 100 µM Ni in roots. SOD and APX increased significantly from 25 to 100 µM, while a significant increase in Gu-POX activity was observed only at 100 µM. For the shoots, a significant decrease was observed, while that of APX was not significantly different. The application of Mo with Ni resulted in a significant increase of plant growth in terms of fresh weight. Significant reductions in lipid peroxidation and H₂O₂ content were also observed in T₄ and T₅. The interactive effect of Ni-Mo had intermediate effects on SOD and APX activities in T₄ treatment and on CAT activity in T₅ treatment. A significant increase in NO content and increased NR activity in the roots suggests the role of Mo in overcoming Ni stress.