[Role of sodium ions and their uptake by cells of cultured blue-green algae, Spirulina platensis and Spirulina maxima].

The growth of the blue-green algae Spirulina platensis and Spirulina maxima, cultured in complete mineral Zarouk medium containing Na+ or Na+-deficient medium, was studied over a period of 24 h. The optical densities of S. platensis and S. maxima cells, determined during the last hour of exposure to sodium deficiency, amounted to 55.6 and 32.6%, respectively, of the optical densities of the same cells grown in complete Zarouk medium. Moreover, the cultures grown in Na+-deficient medium exhibited increased ability to take up sodium (which was low in S. platensis and S. maxima cells cultured in complete mineral medium). It is concluded that the two species studied are characterized by periodic, on the order of minutes, changes in the cellular uptake and release of sodium.