ROLE OF POTASSIUM AND SODIUM IN GENERATION OF OSMOTIC POTENTIAL OF THE MARINE FUNGUS DENDRYPHIELLA-SALINA

Analysis of growth and water relations of the marine hyphomycete Dendryhiella salina over a range of salinities up to 500 mM-NaCl showed that water and osmotic potentials were regulated to maintain a positive water potential gradient to allow water influx. Ion content measurements were largely confounded by the presence of large quantities of sodium and potassium bound in the hyphal wall. Efflux analysis showed that external salinity had little effect on protoplasmic potassium concentration which remained around 30-60 mM, whilst sodium concentration rose from 6 mM at 25 mM-NaCl to 74 mM at 500 mM-NaCl. Even in the presence of high concentrations of NaCl, the hyphal wall selected for potassium in preference to sodium. Results are discussed in relation to the overall role of potassium and sodium in the generation of the osmotic potential in this species.