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 language | English (US) |
|---|---|
| Pages (from-to) | 155-164 |
| Number of pages | 10 |
| Journal | Journal of Membrane Biology |
| Volume | 67 |
| Issue number | 1 |
| DOIs | |
| State | Published - Dec 1982 |
| Externally published | Yes |
Fingerprint
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 journal › Article
}
TY - JOUR
T1 - Turgor regulation in Valonia macrophysa following acute osmotic shock
AU - Guggino, Sandra
AU - Gutknecht, John
PY - 1982/12
Y1 - 1982/12
N2 - 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.
AB - 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.
KW - ion transport
KW - marine algae
KW - Osmoregulation
KW - turgor regulation
KW - Valonia
UR - http://www.scopus.com/inward/record.url?scp=0019923151&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0019923151&partnerID=8YFLogxK
U2 - 10.1007/BF01868658
DO - 10.1007/BF01868658
M3 - Article
AN - SCOPUS:0019923151
VL - 67
SP - 155
EP - 164
JO - Journal of Membrane Biology
JF - Journal of Membrane Biology
SN - 0022-2631
IS - 1
ER -