EFFECT OF CADMIUM ION ON THE GROWTH, PHOTOSYNTHESIS, AND NITROGENASE ACTIVITY OF ANABAENA-INAEQUALIS

The growth of Anabaena inaequalis was significantly inhibited by Cd2+ concentrations greater than 0.02 ppm (μg/ml) and completely inhibited at 0.06 ppm (Day 12). Cadmium had no significant effect upon the lag phase of growth or the culture doubling time, but caused the retardation phase to arrive sooner. One ppm Cd2+ significantly inhibited the rates of both photosynthesis and acetylene reduction, by A. inaequalis, with complete inhibition at 4 and 20 ppm respectively. Cell sensitivity increased directly with exposure time. Cadmium caused some cell lysis of A. inaequalis and induced an increase in filament length, heterocyst frequency, and a loss of cellular contents from filament apical cells. The cellular abnormalities observed and the fact that toxicity increased with longer exposure times, suggested that metal toxicity resulted from effects of Cd2+ taken up by cells rather than Cd2+ at the cell surface. © 1979.