Interaction between light quality and nitrogen availability in the differentiation of akinetes in the planktonic cyanobacterium Gloeotrichia echinulata

Akinete differentiation in Gloeotrichia echinulata is stimulated in batch cultures in the absence of a source of combined nitrogen. When inorganic nitrogen is available in the medium, the logarithmic phase of growth is prolonged and akinetes form at a higher culture density than when dinitrogen is supplied as the sole source of this element. Light quality also influences the timing of akinete differentiation; akinetes are formed at a lower culture density in green light in comparison to white light, particularly in the absence of combined nitrogen. These observations are interpreted in terms of the light-energy requirement for the maintenance of growth and the spectral requirements for nitrogen fixation in cultures free of combined nitrogen. The data are related to the influence of variations in underwater light climate on the development of akinetes in natural populations of planktonic blue-green algae.