Hormogonia mass differentiation from Nostoc sphaeroides Kütz. (cyanobacterium) and the comparison of structural characteristics between hormogonia and vegetative filaments

It was found that, after colonies of Nostoc sphaeroides Kütz. in exponential phase of growth were transferred to fresh complete BG‐11₀ medium, the hormogonia differentiated independent of the type of preculture used. This provided evidence that the hormogonia differentiation was not directly related to phosphorus and potassium status, nor to the osmotic effect of the media. In contrast, all the cultures in the stationary growth phase had no hormogonium differentiation after being transferred to fresh medium. However, the incomplete media for preculture seemed to favor the liberation of hormogonia from colonies to the medium. The result showed that the morphology and ultrastruc‐tures of the vegetative filament, the main stage of Nostocacean life history, determine its adaptability in changing environments, while the hormogonium remains as a propagule of the species.