Nitrogen fixation in root nodules of Alnus is brought about by:

Options

(a) Bradyrhizobium
(b) Clostridium
(c) Frankia
(d) Azorhizobium

Correct Answer:

Frankia

Explanation:

The most common symbiotic association of legume and bacteria on roots is as nodules, which are small outgrowth on the roots. The microbe Frankia is symbiotic in root nodules of several non-leguminous plants like Casurina and Alnus. Both Rhizobium and Frankia are free lilving in soil but can fix atmospheric nitrogen as symbionts.