Salt stimulation and tolerance in an intertidal stem-succulent halophyte

Salt tolerance of Arthrocnemum macrostachyum (Moric.) C. Koch (Chenopodiaceae), a stem-succulent halophyte most commonly found in the intertidal regions of the provinces of Sind and Balochistan, Pakistan, was investigated. Plants were grown for 125 d at six sodium chloride (NaCl) concentrations from 0 to 1000 mM to determine the effects of salinity on ion accumulation, plant water status, and biomass. Shoot biomass was greatest at 200 to 400 mM NaCl, but it was inhibited at salinities of 600 mM NaCl or higher. Tissue water content (g g(-1) dry mass) of shoots under 200 to 600 mM NaCl treatments was higher than under the control nutrient solution, equal to the control at 800 mM NaCl, but significantly lower at 1000 rnM NaCl than under all other treatments, indicating an increase in shoot succulence at salinity levels up to that of seawater. Ash content increased with added salt, but was about 60% of plant dry mass under all salinity treatments. The Na+ and Cl- concentrations of shoots were significantly higher under 1000 mM NaCl than under the control treatment. These results indicate that A. macrostachyum is salt tolerant and capable of accumulating large quantities of Na+ and Cl- when treated with from 200 to 1000 mM NaCl.