The osmotic role of mannitol in the Phaeophyta: an appraisal

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Abstract
Natural abundance 13C nuclear magnetic resonance spectroscopy (NMR) has shown mannitol to be the only major low molecular weight organic compound present in osmotically significant amounts within cells of the following marine brown algae: Alaria esculenta, Ascophyllum nodosum, Ectocarpus siliculosus, Fucus serratus, F. spiralis, F. vesiculosus, Halidrys siliquosa, Laminaria digitata, L. hyperborea, L. saccharina and Pilayella littoralis. Samples of the top-shore alga Pelvetia canaliculata were found to contain volemitol in addition to mannitol. Quantitative gas-liquid chromatographic analyses have confirmed the presence of mannitol, at concentrations ranging from 83.3 to 314.0 mmol kg−1 (expressed in terms of intracellular water content) for plants maintained in a full-strength (100%) sea water medium. A study of the changes in intracellular mannitol concentration of six marine brown macroalgae immersed in hyposaline and hypersaline media (20–150% EA 1 sea water medium) showed that mannitol conce...