Salt Tolerance in the Halophyte, Suaeda maritima (L.) Dum.: The Influence of the Salinity of the Culture Solution on the Content of Various Organic Compounds

Abstract

Plants of the halophyte Suaeda maritima were grown in tap water or in a culture solution in the presence or absence of sodium chloride and the levels of sugars, amino acids, organic acids and quaternary ammonium compounds determined in relation to the balance between cytoplasmic and vacuolar water potentials. The sugar content (some 7 μmol. g f. wt ⁻¹ ) was unaffected by the salinity of the growth medium as was the overall content of amino acids (about 4 μmol. g f. wt ⁻¹ ). The organic acid content was maximal in plants kept in tap water alone where the dominant acid was malic. Plants grown in culture solution contained the same acids, although addition of sodium chloride to the medium brought about the apparent loss of glycolic acid and the appearance of oxalic acid. Only a single quaternary ammonium compound, glycinebetaine, was apparently present in the tissues: the content of betaine doubled (to 37·5 μrmol. g f. wt ⁻ ) when sodium chloride was added to the culture solution. The content of these various compounds is discussed in relation to the relative values of the cytoplasmic and vacuolar components of the overall tissue water potential