Effect of Salinity Stress on Growth, Proline content and Antioxidant Enzymes Activity in the halophyte Sesuvium portulacastrum L

The effect of optimal and supra-optimal concentrations (0, 250, 500 and 750 mM) of NaCl on the growth, chlorophyll, soluble carbohydrate and proline content, ion concentrations and antioxidant enzyme defence of Sesuvium portulacastrum was studied. A significant increase in growth and tissue water content was observed in the shoots exposed to 250 mM salt. Minimum damage to the membrane in terms of electrolytic leakage and better osmotic adjustment at 250 mM salt stress was coupled with the higher accumulation of sodium ions and total soluble sugars as against low proline contents. A fine tuning of antioxidant enzyme activities (superoxide dismutase and ascorbate peroxidase) was also found to be responsible for the optimum growth of shoots. In contrast, sub-optimal (0 mM) and supra-optimal concentrations (500–750 mM) of NaCl significantly affected the growth, water status and increased the electrolytic leakage of the leaves due to the accumulation of toxic concentrations of saline ions. The highest accumulation of proline in addition to antioxidant enzyme activities exhibited higher osmotic adjustment and survival of the shoots under sub- or supra-optimal concentrations of NaCl as a penalty to reduced growth.