Salt Tolerance in Suaeda maritima (L.) Dum: The effect of sodium chloride on growth, respiration, and soluble enzymes in a comparative study with Pisum sativum L

The effect of sodium, chloride on the growth of a halophyte, Suaeda maritima (L.) Dum., was compared with its effect on Pisum sativum L. cv. Alaska under controlled environmental conditions. The salt stimulated the growth of Suaeda maximally at concentrations of 170 to 340 mM while the growth of Pisum was inhibited even by 100 mM. Both species accumulated ions in the tops and the maximum concentrations of Na+ and Cl- rose in Suaeda to 860 mM (based on the water content) and 730 mM and in Pisum to 170 mM and 300 mM respectively. Respiration in both species was inhibited as the NaCl level in the culture solution was raised. Four supernatant enzymes (malic dehydrogenase, glucose-6-phosphate dehydrogenase, peroxidase, and acid phosphatase) prepared from Pisum and from Suaeda (grown either in the absence of added NaCl or in the presence of 340 mM NaCl) were assayed in various levels of sodium chloride. The dehydrogenases were markedly inhibited by increasing salt concentrations while there was a smaller effect on the peroxidase and acid phosphatase. There was no difference in the effect of salt on the enzymes prepared from the two species although one is halophilic and the other halophobic.