The Journal of Membrane Biology

, Volume 24, Issue 1, pp 183–200 | Cite as

Osmotic regulation in the marine alga,Codium decorticatum

I. Regulation of turgor pressure by control of ionic composition
  • Mary A. Bisson
  • John Gutknecht


Codium decorticatum regulates its internal ionic composition and osmotic pressure in response to changes in external salinity. Over a salinity range of 23 to 37‰ (675 to 1120 mosmol/kg)Codium maintains a constant turgor pressure of 95 mosmol/kg (2.3 atm), observed as a constant difference between internal and external osmotic pressures. The changes in internal osmotic pressure are due to changes in intracellular inorganic ions. At 30‰ salinity the major intracellular ions are present in the following concentrations (mmol/kg cell H2O): K+, 295; Na+, 255; Cl, 450. At different salinities intracellular ion concentrations remain in constant proportion to the external ion concentrations, and thus the equilibrium potentials are approximately constant. The potential difference between the vacuole and seawater (−76 mV), which is predominantly a K+ diffusion potential, is also constant with changing salinity. Comparison of the equilibrium potentials with the vacuole potential suggests that Cl is actively absorbed and Na+ actively extruded, whereas K+ may be passively distributed between the vacuole and seawater. Turgor pressure does not change with environmental hydrostatic pressure, and increasing the external osmotic pressure with raffinose elicits a response similar to that obtained by increasing the salinity. These two results suggest that the stimulus for turgor regulation is a change in turgor pressure rather than a change in internal hydrostatic pressure or ion concentrations.


Hydrostatic Pressure Osmotic Pressure Raffinose Equilibrium Potential Turgor Pressure 
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  1. Barnes, H. 1954. Some tables for the ionic composition of seawater.J. Exp. Biol. 31:582Google Scholar
  2. Cram, J. 1975. Negative feedback regulation of transport in cells. The maintenance of turgor, volume and nutrient supply. Encyclopedia of Plant Physiology (in press)Google Scholar
  3. Gage, P.W., Eisenberg, R.S. 1969. capacitance of the surface and transverse tubular membrane of frog sartorius muscle fibers.J. Gen. Physiol. 53:265PubMedGoogle Scholar
  4. Graves, J.S. 1974. Ion transport and electrical properties of the marine alga,Halicystis parvula. Ph.D. Thesis, Duke University, Durham, N.C.Google Scholar
  5. Griswold, B.L., Humoller, F.L., McIntyre, A.R. 1951. Inorganic phosphate esters in tissue extracts.Anal. Chem. 23:192Google Scholar
  6. Gutknecht, J. 1968. Salt transport inValonia: Inhibition of potassium uptake by small hydrostatic pressures.Science 160:68PubMedGoogle Scholar
  7. Hastings, D.F., Gutknecht, J. 1974. Turgor pressure regulation: Modulation of active potassium transport by hydrostatic pressure gradients.In: Membrane Transport in Plants. U. Zimmerman and J. Dainty, editors. p. 79. Springer-Verlag, New YorkGoogle Scholar
  8. Kedem, O., Katchalsky, A. 1958. Thermodynamic analysis of the permeability of biological membranes to non-electrolytes.Biochim. Biophys. Acta 27:229PubMedGoogle Scholar
  9. Kesseler, H. 1964a. Die Bedeutung einiger anorganischer Komponenten des Seewassers für die Turgorregulation vonChaetomorpha linum (Cladophorales).Helgol. Wiss. Meeresunters.10:73Google Scholar
  10. Kesseler, H. 1964b. Zellsaftgewinnung, AFS (apparent free space) und Vakuolenkonzentration der osmotisch wichtigsten mineralischen Bestandteile einiger Helgolander Meeresalgen.Helgol. Wiss. Meeresunters. 11:258Google Scholar
  11. Kesseler, H. 1965. Turgor, osmotisches Potential und ionale Zusammensetzung des Zellsaftes einiger Meeresalgen verschiedener Verbreitungsgebiete.Botanica Gothoburgensia III:103Google Scholar
  12. McNamara, A.L., Meeker, G.B., Shaw, P.D., Hageman, R.H. 1971. Use of a dissimilatory nitrate reductase fromEscherichia coli and formate as a reductive system for nitrate assays.J. Agri. Food Chem. 19:229Google Scholar
  13. Morris, I. 1967. An Introduction to the Algae. Hutchinson and Co., Ltd., LondonGoogle Scholar
  14. Nakagawa, S., Kataoka, H., Tazawa, M. 1974. Osmotic and ionic regulation inNitella.Plant Cell Physiol. 15:457Google Scholar
  15. Ray, P.M., Green, P.B., Cleland, R. 1972. Role of turgor in plant cell growth.Nature 239:163Google Scholar
  16. Silva, P.C. 1960.Codium (Chlorophyta) in the tropical western Atlantic.Nova Hedwigia 1:497Google Scholar
  17. Steudle, E., Zimmermann, U. 1971. Zellturgor und selektiver Ionentransport beiChaetomorpha linum.Z. Naturforsch. 26:1271Google Scholar
  18. Zimmermann, U., Steudle, E. 1971. Effects of potassium concentration and osmotic pressure of seawater on the cell-turgor pressure ofChaetomorpha linum.Marine Biol. 11:132Google Scholar
  19. Zimmermann, U., Steudle, E. 1974. The pressure-dependence of the hydraulic conductivity, the membrane resistance and membrane potential during the turgor pressure regulation inValonia utricularis.J. Membrane Biol. 16:331Google Scholar

Copyright information

© Springer-Verlag New York Inc. 1975

Authors and Affiliations

  • Mary A. Bisson
    • 1
  • John Gutknecht
    • 1
  1. 1.Departments of Botany and of Physiology and PharmacologyDuke University and Duke University Marine LaboratoryBeaufort

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