Ameliorative effect by calcium on NaCl salinity stress related to reactive oxygen species metabolism in Amaranthus tricolor L

Abstract

Soil salinity affects plant growth and development by way of osmotic imbalance which induces oxidative damage in plant tissues. Oxidative stress is caused by increased production of Active Oxygen Species (AOS), such as O2−, •OH, H2O2 and 1O2 these lead to lipid peroxidation, enzyme inactivation and oxidative damage to DNA. Plants have antioxidant defense systems to protect against the production and action of the AOSs. Plants with high level of antioxidants, either constitutive or induced, have been reported to produce greater resistance to this oxidative damage in plant cells. AOS synthesis and its scavenging were investigated in the control, different concentrations of NaCl and NaCl + CaCl2 stressed Amaranthus tricolor L. and Phaseolus vulgaris L.. AOS such as superoxide anion and H2O2 content showed a steady increase in the plants of all NaCl treated media compared to control. When the salinized media were supplemented with CaCl2 the AOS level drastically decreased compared to the corresponding plants grown on salt alone. Similarly, the activity of antioxidant enzymes such as superoxide dismutase, ascorbate peroxidase, catalase and glutathione reductase under salt stress were higher in NaCl + CaCl2 supplemented media than the plants on the salinized media alone. This suggested that the alleviation effect of calcium under saline condition was through modulation of the enzyme complexes that accelerate the rate of antioxidant enzymes biosynthesis under salt stress. Similarly, the level of lipid peroxidation was found to be lower in plants of all NaCl + CaCl2 media than control