Question

Nitrogen fixation is performed by

• A. Green algae and fungi
• B. Ferns and cycads
• C. Legumes and cereals
• D. Blue-green algae and bacteria

Answer 1

The correct option is D Blue-green algae and bacteria

The atmospheric nitrogen is not available to plants. There are some nitrogen-fixing bacteria which converts atmospheric nitrogen into ammonia which is readily available to plants. Azotobacter is a free-living nitrogen-fixing bacteria. Rhizobium in association with the leguminous plants carries out the process of nitrogen fixation. Blue-Green algae like Anabaena and Nostoc are free-living nitrogen-fixing bacteria. However, they are symbiotic bacteria as well.

Thus, the correct answer is Blue-green algae and bacteria.'