Amelioration of cadmium toxicity by enhancing nitrogen assimilation and photosynthetic activity by two different nitrogen supplements in rice (Oryza sativa L.) cv. Lalat

Abstract

Rapid industrialization and over-use of agrochemicals may lead to cadmium (Cd) contamination in agricultural soil, posing serious threat to human health. In recent times, application of plant nutrients and other growth promoting substances, like, nanoparticles (nZVI), silicon, salicylic acid were reported to have ameliorated Cd toxicity, in this regard, nitrogen (N) amendment can be a promising technique to ameliorate Cd toxicity as, N is an essential macronutrient responsible for plant growth and development. In the present study, seven days old seedlings of Oryza sativa L. cv. Lalat were co-treated with 10 µM CdCl2 and two different nitrogen supplements (Calcium nitrate and Ammonium acetate) separately to evaluate its ameliorating potential. It was observed that, Cd stress impaired plant vigor, biomass, RWC, nitrogen-containing components and non-enzymatic antioxidants causing significant reduction in photosynthesis and N-assimilation, indicating sensitivity of the cultivar to Cd stress. Cd stress also enhanced lipid peroxidation, enzymatic-antioxidant activity, proline and non-protein thiol accumulation. N-supplementation to Cd stressed plants rescued plant growth, biomass, protein content and nitrogen containing compounds leading to the upregulation of photosynthesis and nitrogen assimilation. N amendment was found to downregulate lipid peroxidation, enzymatic antioxidant activity, proline and non-protein thiol content and upregulate non-enzymatic antioxidant. Agronomical parameters and yield also improved significantly by N supplementation as compared to Cd stressed plants. Supplementation with N salts also improved grain quality by enhancing grain nutrients and reduced grain Cd by decreasing bioavailable Cd in soil, thereby reducing daily Cd intake and cancer risk. Among the two N-supplements, ammonium acetate showed better ameliorating effect compared to calcium nitrate.