Irrigation with Magnetically Treated Water Enhances Growth and Defense Mechanisms of Broad Bean (Vicia Faba L.) and Rehabilitates the Toxicity of Nickel and Lead

Abstract

Toxicity of heavy metals leads to dramatical changes in biochemical reactions in plants. In this research, the effect of nickel (Ni) and lead (Pb) on growth and antioxidant enzymes of broad bean (Vicia faba L.) was evaluated, besides the role of irrigation with magnetically treated water (MTW) in enhancing the antioxidant defense mechanisms. Ni was applied at the rate of 0, 250, and 500 mg kg−1 of soil, and Pb levels were 0, 500, and 1000 mg kg−1 of soil in a pot experiment. The cultivated pots were subsequently apportioned into two subsets: One was irrigated with tap water, and the other was irrigated with magnetically treated water (MTW) passed through 1000 G magnet. Results implied that applied heavy metals decreased shoot and root fresh and dry weights. Photosynthetic pigment (Chla + Chlb) contents were not significantly changed except the noticed increase in plants grown in soil treated with 250 mg Ni kg−1; however, total carbohydrate content decreased significantly in all treatments. Enhanced Ni and Pb concentrations significantly increased proline and total protein content, and referring to oxidative stress, there was a significant increase in hydrogen peroxide (H2O2) level and lipid peroxidation. The activity of antioxidant system revealed a significant increase in anthocyanins; however, massive deactivation of glutathione (GSH), catalase (CAT), ascorbate peroxidase (APX), peroxidase (POX), and superoxide dismutase (SOD) has been remarked. On the other hand, MTW significantly enhanced the morphological parameters and decreased proline and total protein content in all treatments. The criteria of H2O2 and the lipid peroxidation showed a fluctuation trend among the different concentrations of heavy metals. Moreover, MTW caused a significant increase in most antioxidant activities in plants grown in soils with/without heavy metals. The present study revealed a novel role of irrigation with MTW in the adaptation of broad bean plants to toxic effects of Ni and Pb based on plant growth, physiological and biochemical criteria.