The interactive effects of cadmium (Cd) and calcium (Ca) on growth, ph
otosynthesis (O-2 evolution), nitrogenase, respiration, developmental
cycle and Cd bioaccumulation by the N-2 fixing cyanobacterium Nostoc U
AM208 have been studied. Ca was found to exert a detoxifying role towa
rds Cd inhibition of these physiological processes. Finally, the mecha
nisms by which Ca might protect the cyanobacterium against Cd toxicity
are discussed.