Salt stress enhanced antioxidant response in callus of three halophytes (Salsola baryosma, Trianthema triquetra, Zygophyllum simplex) of Thar Desert

Effects of salinity on growth, protein content, proline, catalase and antioxidant enzyme activity in callus of three halophytes of the Thar Desert; Salsola baryosma, Trianthema triquetra and Zygophyllum simplex were evaluated. Callus tissues were cultured on Murashige and Skoog's medium containing different concentrations of NaCl (50, 100 and 200 mM). Increase in dry weight and soluble proteins were observed in the callus exposed to lower salinity (50 and 100 mM NaCl) in all the three species, whereas on the medium containing 200 mM NaCl, significant decrease in these two growth parameters was recorded. Under the salinity stress maximum proline accumulation was found in S. baryosma with parallel increase in soluble sugars. Among the three species, T. triquetra callus showed maximum CAT activity with 50 and 100 mM NaCl treatment, whereas the enzyme activity decreased at 200 mM NaCl treatment in all three species. The antioxidant potential steadily elevated under salt treatment in all the above three species using 1, 1-diphenyl-2-picrylhydrazyl (DPPH) and ferric reducing antioxidant potential (FRAP) assay. Whereas, superoxide dismutase (SOD) quenching were recorded maximum at low (50 and 100 mM) concentrations in all the three species. However, T. triquetra callus showed maximum total phenolic content (TPC) 15 mg GAE g(-1) with the elevated concentration of NaCl up to 200 mM, and S. baryosma callus showed lower TPC as compared to both species. A significant correlation between antioxidant capacity and TPC was observed indicating that phenolic compounds are the major contributors to the antioxidant potential in these halophyte species. FRAP and DPPH activity of Z. simplex showed maximum correlation (R = 0.992), as compared to other two species. We can conclude that all the three species exhibit a protection mechanism by sustaining growth parameters and antioxidant capacity. Due to high antioxidant property of all these species, the plant extracts may be included in nutraceutical formulations.