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- Title
SODIUM TRANSPORT IN <em>ENTEROMORPHA INTESTINALIS</em> (L.) LINK.
- Authors
Ritchie, R. J.; Larkum, A. W. D.
- Abstract
Sodium transport was studied in the marine euryhaline alga, <em>Enteromorpha intestinalis</em> in seawater (465 mM Na+ and in low salinity medium [Artificial Cape Banks Spring Water (ACBSW), 25.5 mM Cl-, 20.4 mM Na+, 0.5 mM K+]. The intracellular Na+ concentration ([Na+i]) of <em>E. intestinalis</em> 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 <em>Enteromorpha</em> 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 Nai+] than a rinsing technique using isotonic Ca(NO3)2. The overall mean [Nai+] 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 <em>Enteromorpha</em> 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 <em>Enteromorpha</em> 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).
- Subjects
SODIUM; ENTEROMORPHA; ULVACEAE; ALGAE; SALINITY; PLANTS
- Publication
New Phytologist, 1984, Vol 97, Issue 3, p347
- ISSN
0028-646X
- Publication type
Article
- DOI
10.1111/j.1469-8137.1984.tb03600.x