A. S. Ahluwalia
Phycology Laboratory, Department of Botany, Panjab University, Chandigarh-160014 - 160 014
The blue-green algae (cynobacteria) have attracted considerable attention because of their unique position among prokaryotes. Despite their primitive cellular organization, the photosynthesis operating in these organisms is characteristic of higher plants. These algae possess a rare combination of oxygen evolving photosynthetic and oxygen sensitive nitrogen fixing systems. The process of nitrogen fixation is carried out by specialized cells known as heterocysts. Heterocysts contain an active nitrogenase and are differentiated at regular intervals in the algal filaments. Many morphological and physiological changes occur during differentiation of a heterocyst from a vegetative cell. Recently role of various genes involved in differentiation and pattern formation has been elucidated.
Key words: Blue-green algae, cyanobacteria, heterocyst, differentiation.