Question

Name the cell which is responsible for nitrogen fixation in cyanobacteria.

Hint:

Heterocysts differentiate under nitrogen-limiting conditions and are interconnected to vegetative cells via plasmodesmata for nutrient exchange.

Answer 1

Heterocysts are specialized, thick-walled cells in filamentous cyanobacteria (e.g., Anabaena) that provide an anaerobic microenvironment for nitrogenase enzyme activity. They lack photosystem II to avoid oxygen production, which inactivates nitrogenase, and fix atmospheric N$_2$ into ammonia.