Inorganic ions and floridoside as osmotic solutes in Porphyra umbilicalis [algae]
1981
Wiencke, C. | Laeuchli, A. (Tieraerztliche Hochschule, Hannover (Germany, F.R.). Inst. fuer Botanik)
The absolute values for the non-osmotic volume of cells of the intertidal red alga Porphyra umbilicalis increase in diluted and decrease in concentrated artificial seawater medium ASP(12). The content of various inorganic ions and organic compounds was studied in relation to osmotic regulation. Potassium (K(+)), chloride (Cl(-)) and the alpha-galactosylglycerols floridoside and isofloridoside are the main osmotically active solutes: Cl(-), floridoside and isofloridoside mainly at low hyperosmotic stress, i.e. in media from 2 to 3.5x, K(+) in the growth range, i.e. in media from 0.2 to 1.5x and also to a certain extent at low hyperosmotic stress. It is concluded that floridoside and isofloridoside are probably located in the cytoplasm, whereas Cl(-) may mainly be localized in the vacuoles. The most likely localization of K(+) is the cytoplasm in 1x medium, but cytoplasm and vacuoles in 3x medium. These conclusions take into consideration the different development of the vacuoles in 1x and 3.5x medium (4 resp. 40% of the protoplasmic volume).
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