Metabolism of Isofloridoside (O-α-D-Galactopyranosyl-(1→1)-Glycerol) and Osmotic Balance in the Fresh Water Alga Ochromonas

Abstract

So far as is known, algae tend to maintain a constant turgor with the osmotic pressure in their cells higher than the osmotic pressure of the surrounding fluid. This excess osmotic pressure seems to be held constant when the osmotic value of the water changes. Little is known about the mechanisms responsible for this regulation. The assimilation or extrusion of special inorganic ions is assumed to play the chief part in this process in marine algae; in cases of low external osmotic pressure the elimination of water by contractile vacuoles provides some regulation of osmotic balance in fresh water algae¹. The experiments reported here show that the golden brown fresh water alga Ochromonas malhamensis has another mechanism for regulating turgor. Here the regulation is connected with the formation and degradation of the carbohydrate isofloridoside and further studies on the biochemistry of the osmotic balance in Ochromonas therefore seem possible.