Question

Heterocysts occur in

• A. Chlorophyceae
• B. Phaeophyceae
• C. Cyanophyceae$/$ Cyanobacteria $/$ Nostoc
• D. Rhodophyceae

Answer 1

Answer: (C)

Cyanophyceae$/$ Cyanobacteria $/$ Nostoc

Anabaena andNostoc are Cyanobacteria/Cyanophyceae. They have the ability to fix atmospheric nitrogen. They convert nitrogen into ammonia. The heterocysts present in them are specialized for nitrogen fixation. They contain enzyme nitrogenase. Nitrogenase is inactivated by oxygen. Hence, the heterocyst creates a micro anaerobic environment.

Thus, the correct answer is 'Cyanophyceae/ Cyanobacteria / Nostoc.'