MODIFICATIONS OF ALGAL CELL-WALL PROPERTI ES 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 c ell water content of the strictly autotrophic alga Hydrodictyon reticu latum. 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 indi cate that the performance of the sodium pump in the plasmalemma is aff ected by altered turgor pressure, which is largely determined by the e lasticity properties of the growing cell walls. These are then influen ced 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 manna n rather than the cellulose moiety of the cell wall, has a different e ffect: its presence increases the turgor but has no significant effect on intracellular sodium concentration.