Physiological and antioxidant responses of the perennial halophyte Crithmummaritimum to salinity

Physiological behavior and antioxidant responses to salinity were studied in Crithmum maritimum, a local halophyte naturally growing on rocky coasts. The plant growth was significantly improved at moderate salt levels (50 mM NaCl), but was drastically reduced at 200 mM NaCl. The stimulation of biomass production at 50 mM NaCl was associated with enhanced root length and leaf number. Tissue hydration seemed unaffected by salinity, despite Na+ and Cl− were largely accumulated in shoots. The highest salinity (200 mM NaCl) induced mineral nutrition disturbance within the plant shoots, as their Ca2+, Mg2+, and K+ concentrations significantly declined. However, C. maritimum displayed high uptake selectivity for the latter. Monitoring lipid peroxidation showed that both root and shoot malonyldialdehyde (MDA) contents of plants cultivated at the optimal salt concentration (50 mM NaCl) were lower than control ones. This was related to enhanced activities of antioxidant enzymes, like superoxide dismutase (SOD) (EC 1.15.1.1), catalase (EC 1.111.1.6), and peroxidase (EC 1.111.1.7), especially in shoots. The limitation of the plant growth at 200 mM NaCl was concomitant with lesser efficiency of these protective enzymes, but MDA levels in both roots and shoots remained close to control ones.