Relationship between salt accumulation and water content of dicotyledonous halophytes

Abstract

Abstract. Growth rates and levels of minerals, Na + , K + , Mg ++ , Ca ++ , and water were measured in dicotyledonous halophytes grown along a salinity gradient from fresh water to 720 mol m −3 NaCl in a controlled environment greenhouse. Ten test species from the families Chenopodiaceae, Aizoaceae, and Batidaceae exhibited growth stimulation by 180 mol m −3 NaCl and were classified as euhalophytes. Ten others from the families Chenopodiaceae, Aizoaceae, Asteraceae, Brassicaceae, Polygonaceae, Boraginaceae, Malvaceae, and Plumbaginaceae showed their best growth on fresh water and were classified miohalophytes. Salt, and particularly sodium, accumulated in all halophytes but to a significantly greater extent among euhalophytes than miohalophytes. The water content of most species increased when grown on 180 mol m −3 NaCl compared to fresh water; but at higher salinities some of the species underwent dehydration. Dehydration of the succulent S. europaca was not coupled to a proportional decrease in growth. Water content and cation accumulation in euhalophytes appeared to be coordinated to produce a constant osmotic potential gradient within the shoot tissues relative to the external salinity. In contrast, miohalophytes did not appear to regulate osmotic potential as closely as euhalophytes.