The physiology of salt tolerance of the salt marsh halophyte, Salicornia bigelovii



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The halophyte Salicornia biqelovii, an inhabitant of the Texas coastal salt marsh, possesses a high degree of salt tolerance. In addition, a number of other species also inhabit the salt marsh and show varying degrees of salt tolerance. Three plant communities were recognized. The study of the salt tolerance of S. bigelovii revealed that growth in hydroponic culture solution reached a maximum with the addition of 2.42% to 3.6% sea salt. Growth was very poor without the addition of sea salt to the culture solution. At salinities above 3.6% growth was greatly inhibited. Seed germination was retarded at 4.4[degrees] C., but high rates of germination eventually occurred at this temperature even in a high salinity of 3.6% Germination was inhibited in salinities above 3.6% at temperatures of 26.6[degrees] C. Ion analyses revealed that, in almost every case. Cl[raised -] exceeded Na[raised +] and K[raised +] content. The K[raised +] content was higher in the root than Na[raised +], However, Na[raised +] was higher than K[raised +] in stem and stem tip. The Mg[raised ++] content was consistently low,usually less than 2% of dry weight. Seeds were high in Na[raised +] (31.33%), lower in K[raised +] (15.0%), high in Cl[raised -] (36.31%). Growth of S. bigelovii in aseptic culture confirmed the results of growth in hydroponic solution. However, growth was not as successful in the higher salinities above 3.6%. Ion analyses of these tissues revealed that K[raised +] had a high of 10.7%, but was exceeded in every case by Na[raised +]. Cl[raised -] exceeded Na[raised +] and K[raised +]. Amino acid analyses revealed that a larger free amino acid pool existed in those plants that were not growing in tidal sea water. The bound amino acids in those plants growing on the spoil islands were also higher in every case except for the basic amino acids lysine and arginine. Enzyme analyses by means of gel electrophoresis disclosed that considerable differences existed between enzymes of root, stem and stem tip. Gas chromatographic separation of lipied and hydrocarbons in the shoot showed that the hydrocarbons were predominantly odd-chained with chain lengths of C[lowered 27], C[Lowered 29] and C[lowered 31]. In the roots, the C[lowered 24] and C[lowered 25] carbon chains were predominant. In the seed, the C[lowered 27], C[lowered 29], and C[lowered 31] were again predominant. In the shoot fatty acids, the major unsaturated acid was linoleic acid and the predominant saturated acid was palmitic acid. In the roots the major unsaturated fatty acids were oleic and linoleic acid in approximately 1:1 ratio. The predominant saturated acid was palmitic acid. The major difference in the root and shoot fatty acid distribution was the high concentration of linoleic acid (41.9%) in the shoot. The total fatty acid content of the seed lipid hydrolysates contained approximately 67.8% linoleic acid. The unsaturated acids were in larger concentration than the saturated acids. The major saturated acid was C[lowered 16].