SODIUM TRANSPORT IN ENTEROMORPHA INTESTINALIS (L.) LINK
Article first published online: 2 MAY 2006
Volume 97, Issue 3, pages 347–362, July 1984
How to Cite
RITCHIE, R. J. and LARKUM, A. W. D. (1984), SODIUM TRANSPORT IN ENTEROMORPHA INTESTINALIS (L.) LINK. New Phytologist, 97: 347–362. doi: 10.1111/j.1469-8137.1984.tb03600.x
- Issue published online: 2 MAY 2006
- Article first published online: 2 MAY 2006
- (Accepted 10 February 1984)
- Enteromorpha intestinalis;
- ionic relations;
- low salinity;
- sodium transport
Sodium transport was studied in the marine euryhaline alga, Enteromorpha intestinalis in seawater (465 mM Na+ and in low salinity medium [Artificial Cape Banks Spring Water (ACBSW), 25.5 mM Cr, 20.4 mM Na+, 0.5 mM K+]. The intracellular Na+ concentration ([Na+1]) of E. intestinalis was so low that it was difficult to detect using chemical and 22Na+ methods. Consequently, intracellular Na+ fluxes were also difficult to measure. Most of the Na+of the Enteromorpha tissue was bound to the fixed negative charges of the cell wall and this binding has, in previous studies, led to great overestimates of the intracellular Na+ of this plant-Data of 22Na+ labelling gave lower estimates of the Na+1] than a rinsing technique using isotonic Ca(NO3)2. The overall mean [Na+1] of seawater plants was only 5.5 ± 1.4 mM, with a value of 0.623 ± 0.163 mM Na+ in ACBSW plants. With one exception, all the seawater 22Na+ experiments indicated a single intracellular exchange phase, i.e. a separate vacuolar phase could not be detected. The data on plants grown at low salinity could be interpreted as having either a single intracellular phase or two intracellular phases because of the problem of cell wall Na+ exchange. No significant difference was found in total 22Na+ uptake or exchange fluxes in the light and dark in seawater-grown plants but there may have been a light effect on low salinity plants. The Na+ flux in Enteromorpha plants in seawater was about 3 nmol m−2 s−1 and in low salinity plants was about 0.2 nmol m−2 s−1.
Sodium in Enteromorpha is far from electrochemical equilibrium (more than –100 mV) in plants in both seawater and ACBSW medium so that Na+ is actively excluded from the cells. The plasmalemma has a very low Na+ permeability (seawater, 3 pm s−1; ACBSW plants, either 3 or 100 pm s−1 depending on which compartmentation model is accepted).