MODIFICATIONS OF ALGAL CELL-WALL PROPERTIES AND A TURGOR-DEPENDENT SODIUM-PUMP BY EXTERNAL CARBOHYDRATES

The presence of osmotically insignificant (6.1 mM) concentrations of D-glucose or 2-deoxy-D-glucose in culture medium strongly reduces the cell water content of the strictly autotrophic alga Hydrodictyon reticulatum. At the same time D-glucose significantly increases the apparent intracellular sodium concentration while 2-deoxy-D-glucose reduces it. The intracellular levels of sodium, potassium and chloride ions indicate that the performance of the sodium pump in the plasmalemma is affected by altered turgor pressure, which is largely determined by the elasticity properties of the growing cell walls. These are then influenced by the presence of external sugars which affect the cellulose part of the cell wall. D-mannose (6.1 mM), which seems to affect the mannan rather than the cellulose moiety of the cell wall, has a different effect: its presence increases the turgor but has no significant effect on intracellular sodium concentration.