On the osmoregulation in Atriplex hymenelytra (Torr.) Wats. (Chenopodiaceae)

Summary Aspects of osmoregulation were studied in leaves of irrigated and nonirrigated plants of Atriplex hymenelytra (Torr.) Wats. (Chenopodiaceae) from their natural habitat in Death Valley, California. Using a set of several data concentrations of inorganic electrolytes (Na⁺, K⁺, Cl^-) and of oxalate in the mesophyll of this salt secreting species were calculated. The osmotic potential resulting from these solutes (under consideration of an empirically estimated osmotic coefficient) is in good agreement with field measurements of the overall osmotic potential in the leaf mesophyll as determined by pressure-volume curves. This indicates that these 4 electrolytes are the main osmotically active solutes. Oxalate is present in comparably high concentrations and is used to achieve ion balance.Organic solutes analyzed include soluble carbohydrates (mono-, di- and oligosaccharides), amino- and organic acids as well as glycinebetaine. Of these, organic- and amino acids (including proline) contribute only little to osmoregulation. Soluble carbohydrates and especially glycinebetaine exhibit concentrations high enough for generating considerable osmotic potentials, at least if these compounds are regarded to be restricted to the cytoplasm acting as compatible solutes.