Juncus subulatus of the Mediterranean coast, one of the species which tolerates the highest concentrations of salt, develops only in a humid habitat. When the soil dries, it begins to suffer and increase its osmotic concentration from 19.6 to 50 atmospheres, at which point the plant yellows and dies. These species can by no means be regarded as xerophytes, as Schimper assumed. In Faber’s experiments the mangroves gave evidence of the fact that the increase of osmotic pressure in plants grown in highly concentrated nutritive solutions (NaCl, MgSO4, KNO3) is alone sufficient to cause an increase of water-storage tissue and thereby a thickening of the leaves. Accordingly, the succulence of the mangrove would be a case of hypertrophy caused by high turgor pressure. Keller (1925) arrives at similar results in experiments with S. herbacea. An addition of very small quantities of sodium and potassium chloride to the nutritive solution brought about a more vigorous growth as well as an increase of succulence. Sodium sulphate has a similar effect, while magnesium sulphate, according to the experiments of Batahn (cited in Keller, 1925), caused no noticeable increase of succulence as compared with plants of unsalted soils. (Braun-Blanquet 1932:193)
BRAUN-BLANQUET, Josias. 1932. Plant sociology: the study of plant communities. (Trans.: George D. Fuller; Henry S. Conard) New York: McGraw-Hill Book Company.