The Effect of Zinc excess on antioxidant enzymes, proline and soluble carbohydrates in Plantago major L.

The increase of environmental pollutants especially heavy metals derives from human industrial communities. Zinc is one of the natural elements that exist in biotic environment, plants body, and animals in different forms. Zinc has toxic and lethal effects in high concentrations on plants. Also some plants are introduced as accumulators of this element. Therefore, an investigation was carried out to consider different concentrations of Zn on Plantago major in completely random form and with three replications.  The ZnSO4.7H2O was included at 0, 50, 100, 250, 500, and 700 µmolar concentrations that were applied to the plants during 8 days. The results indicated that catalase enzyme activity increased significantly in comparison with control in root and shoot except at 50 µmolar concentration. Ascorbate peroxidase enzyme activity increased significantly only at 50 and 500 µmolar concentrations in comparison with control in shoots but it increased significantly in root with increasing metal concentration. Peroxidase enzyme activity increased significantly only at 50 and 700 µmolar concentration in shoot; however, this enzyme increased significantly in root with increasing metal concentration except at 500 µmolar concentration. The amount of proline increased significantly with increasing of zinc concentration. Soluble   carbohydrates decreased significantly in comparison with control in root and aerial organs except at 700 µmolar concentration. These results derive from plant resistance against high concentrations of Zn.