Nickel toxicity mitigation by supplementation of acetylcholine in wheat: Growth, photosynthetic and antioxidant activities

Abstract

Influence of exogenous treatment of acetylcholine (ACh; 5 and 10 µM) was studied on the growth, photosynthesis and nitrate reductase activity in wheat under nickel (500 µM Ni) stress. Plant height, fresh and dry weight of shoot showed a decline of 36%, 23% and 40% respectively while as increased by 35%, 44% and 47% due to 10 µM ACh over control. Treatment of ACh, at both concentrations, alleviated the decline with obvious effects at higher (10 µM) concentrations. Treatment of ACh resulted in increased content of total chlorophylls, carotenoids and photosynthesis, intercellular carbon dioxide, transpiration and PSII activity, which were however significantly reduced by Ni stress. Exogenous application of ACh alleviated the Ni stress mediated decline in the activity of nitrate reductase. Wheat plants treated with Ni showed increased production of hydrogen peroxide resulting in increased lipid peroxidation and electrolyte leakage, however treatment of ACh reduced these parameters significantly reflecting in alleviation of oxidative damage. Activity of antioxidant enzymes assayed (SOD, CAT, APX, DHAR and GR) and the content of ascorbic acid and reduced glutathione increased significantly in ACh treated plants under normal and Ni stress. Activities of SOD, CAT, APX, DHAR and GR was increased by 162%, 108%, 70%, 107% and 87% respectively in Ni + 10 µM ACh treated plants. In addition, the content of phenols and flavonoids increased due to application of ACh. Content of nitrogen, potassium and calcium increased due to ACh and also alleviated the decline induced due to Ni stress while as the content of Ni was reduced in plants treated with ACh.