Turgor regulation in Valonia macrophysa following acute osmotic shock

Sandra Guggino, John Gutknecht

Research output: Contribution to journalArticle

Abstract

The marine alga Valonia macrophysa an inhabitant of shallow subtropical waters, is subjected to sudden dilutions of external seawater during rain showers. This study describes the mechanisms involved in turgor pressure regulation following acute hyposmotic shock. Turgor regulation is 88% effective and complete within 4 hr following hyposmotic shocks of up to -10 bar. Loss of vacuolar K+, Na+ and Cl- accounts for the decrease in vacuolar osmotic pressure associated with turgor regulation. A novel mechanism of turgor regulation is exhibited by Valonia macrophysa given hyposmotic shocks greater than about -4 bar. Such an osmotic shock causes cell wall tension to increase above a critical value of about 6×105 dyne/cm, whereupon the protoplasm ruptures and the cell wall stretches irreversibly at a localized site. The protoplasm rupture is suggested by (1) a large abrupt increase in K+ efflux (as measured by86Rb+), (2) a rapid decrease in turgor pressure as measured with a pressure probe, and (3) sudden depolarization of the vacuole potential. Evidence for an increase in cell wall permeability includes efflux from the vacuole of dextran (mol wt 70,000), which normally has a very low cell wall permeability, and scanning electron micrographs which show a trabeculated scar area in the cell wall. This mechanism of turgor regulation is physiologically important because 98% of the cells regained normal growth rate and turgor following acute osmotic shock.

Original languageEnglish (US)
Pages (from-to)155-164
Number of pages10
JournalJournal of Membrane Biology
Volume67
Issue number1
DOIs
StatePublished - Dec 1982
Externally publishedYes

Fingerprint

Osmotic Pressure
Cell Wall
Shock
Vacuoles
Pressure
Rupture
Permeability
Cytoplasm
Rain
Seawater
Dextrans
Cicatrix
Electrons
Water
Growth

Keywords

  • ion transport
  • marine algae
  • Osmoregulation
  • turgor regulation
  • Valonia

ASJC Scopus subject areas

  • Physiology
  • Cell Biology
  • Biophysics

Cite this

Turgor regulation in Valonia macrophysa following acute osmotic shock. / Guggino, Sandra; Gutknecht, John.

In: Journal of Membrane Biology, Vol. 67, No. 1, 12.1982, p. 155-164.

Research output: Contribution to journalArticle

Guggino, Sandra ; Gutknecht, John. / Turgor regulation in Valonia macrophysa following acute osmotic shock. In: Journal of Membrane Biology. 1982 ; Vol. 67, No. 1. pp. 155-164.
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