Question

Specialized cells for fixing atmospheric nitrogen in Nostoc are

(a) heterocysts

(b) hormogonia

(c) nodules

(d) akinetes.

Answer 1

Ans : (a) heterocysts

Explanation:

Certain species of cyanobacteria (Nostoc) possess some special cells called heterocysts which occur in terminal, basal and intercalary positions. Heterocysts are yellowish in colour and contents are homogenous. Heterocysts are now known as sites of nitrogen fixation. Atmospheric nitrogen is made available in the form of ammonia by cyanobacteria.