Biochemical and physiological adaptations of the halophyte Sesuvium portulacastrum (L.) L., (Aizoaceae) to salinity

Sesuvium portulacastrum is a dicotyledonous halophyte. The responses of different clones of Sesuvium to salinity were analysed by measuring changes in growth, biomass accumulation, water content, osmolytes accumulation, oxidative damage, antioxidant enzymes and inorganic ions. In addition, microscopic observations were made to discern any changes in the stem anatomy of Sesuvium under salt stress. Reduced growth, biomass accumulation and tissue water content correlated with an increase in NaCl concentrations (200-800 mM), except at 200mM NaCl, where an improvement in the parameters was observed among all clones, specifically in MH1 (Maharashtra). Increased osmolytes (proline, glycine betaine and total soluble sugars) and the accumulation of Na+ ions, without affecting K(+)content, were recorded in all clones. Higher malondialdehyde content and greater relative electrolyte leakage were evident in addition to increased catalase and superoxide dismutase activities under salt stress. Increased cortical cell size and cortex diameter of the stem were observed upon 200-400mM NaCl stress; decreased thickness was seen at higher NaCl concentrations. This study suggests the differential behaviour of Sesuvium clones which might be useful in the rapid selection of a potent clone (such as MH1) for the restoration of wetlands and desalination of saline soils.