Investigation of nickel effect on growth parameters, pigments content, soluble carbohydrates, total protein, nickel accumulation and peroxidase enzyme activity of Mentha longifolia L.

Heavy metals, including nickel, are among the most important pollutants. Ni as a micronutrient is essential for plants, however, with increasing concentrations of nickel in the environment, excess of the element accumulated in plants and causing toxicity. Phytoremediation is a biotechnology, using the plant to remove or reduce environmental pollutants. In this study, to evaluate the nickel phytoremediation potential and accumulation, the effects of different levels of nickel on some growth and development characteristics of Mentha longifolia L., were studied. Various concentrations of nickel (0, 10, 50, 100 and 300 mg/l) were treated in hydroponic culture, and in this condition, the plant potential for nickel tolerance and nickel effects on some physiological and morphological characteristics of M. longifolia were evaluated. Experiments were conducted in a completely randomized design. Results analysis showed that characteristics: shoot and root length, leaf area, shoot and root dry weight, total chlorophyll, carotenoid, anthocyanins and soluble carbohydrates content of the plant were reduced by increasing the concentration of nickel in nutrient solution but total protein and shoot and root nickel content were increased. Overally, based on evaluating of the effects of nickel on vegetative and physiological characters of M. longifolia, in this study, it can be acknowledged that the plant is not resistance to nickel stress, and is not suitable for phytoremediation and removing excess amounts of nickel in the environment. Also, due to the sensitivity of the plant to nickel stress, it can be counted as an indicator of environmental nickel pollution.