Glycinebetaine (GB) is a very important organic osmolyte that accumulates in a number of diverse groups of plants in response to environmental stress. In some plants, increased resistance to drought, salinity and low temperature has been achieved through exogenous application of GB. In this study, the effect of exogenously applied GB (8 mM) on the ability of vinal (Prosopis ruscifolia G.) plants to withstand NaCl stress was investigated. The dry biomass of vinal showed a decrease under salt stress, but in GB-treated plants exposed to the same stress, this reduction was mitigated. Sodium accumulated in the leaves of plants grown under saline conditions, but the addition of GB to salt-grown plants reduced Na+ content by 40%. Salinity significantly reduced the K+ concentration in leaves to 65% that of non-salinized controls. In the presence of GB, leaf K+ was comparatively higher, reaching as much as 90% of the control concentration. The sodium: potassium ratio in leaves was significantly higher in salt-stressed plants, but this ratio was lowered significantly by the addition of GB. When compared to control plants, NaCl stress increased malondialdehyde (MDA) concentrations by 95%, but GB application reduced the MDA concentration in these same NaCl-treated plants. In comparison to control plants, the activity of superoxide dismutase (SOD) increased by 52% in salt-stressed plants. The addition of GB to salt-treated plants stimulated SOD activity twice that of the non-salizined control. These results suggest that, in addition to protecting membranes, GB-enhanced salinity tolerance in vinal may involve an antioxidant mechanism involving enhanced SOD activity and improving the ion homeostasis under conditions of high salinity.
lipid peroxidation; salt stress; superoxide dismutase
