Growth, Antioxidant Enzymes Activities, and Proline Accumulation in Mustard Due to Nickel

Abstract

Leafy vegetables can accumulate high amounts of nickel (Ni) during vegetative development. A glasshouse experiment was conducted with 50, 100, 200, 300, and 400 μM of Ni to assess the Ni accumulation pattern and its influence on growth, activities of antioxidant enzymes, and proline accumulation in mustard (Brassica juncea L.), cv. T 59, plants. Visual symptoms of toxicity intensified as Ni level increased. Decreased concentrations of chlorophyll and carotenoids in leaves associated with an increase in activities of antioxidative enzymes, proline content, and lipid peroxidation indicate a strong induction of oxidative stress in mustard due to Ni. Decreased activity of catalase at >100 μM Ni indicates interference in iron metabolism of plants. The decrease in dry matter in relation to Ni level is attributed to depletion of the functional iron as ferritin. The appearance of metal-specific toxicity effects is likely the result of membrane damage as a consequence of production of reactive oxygen species (ROS), especially at >300–400 μM Ni. Increased carotenoids:chlorophyll ratio values as the Ni level increased is indicative of the development of a protective mechanism in mustard used to counter the production of ROS.

Keywords:

• Brassica juncea
• Chlorosis
• Pigments
• Lipid peroxidation
• ROS