Cyanobacterium Petalonema alatum BERK. ex KIRCHN. - species variability and diversity

Petalonema alatum is an interesting cyanobacterial species of subaerial calcareous habitats in gorges of the National Park Slovensky raj, Slovakia. Observation of different morphological forms in natural and culture materials is demonstrated and discussed. Cultures of P alatum differed from natural populations mainly in the width of the filament apex, massiveness of mucilage sheaths, and degree of heteropolarity. This means that these features are more likely controlled by environmental variables. Other characteristics (heteropolarity, false branching, sheath structure) were found to be stable and consequently can have taxonomical importance.