Question

Nitrogen fixing organisms which can be free as well as symbiotic is

• A. Anabaena
• B. Azotobacter
• C. Liverworts
• D. Mosses

Answer 1

Answer: (A)

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. Rhizobium are symbiotic nitrogen fixing bacteria live in symbiotic association with the leguminous plants in the root nodules of plants. They provide nitrogen to the plant and in return get shelter from the plant. Azotobacter are free-living nitrogen fixing bacteria. Anabaena is a free-living nitrogen fixing bacteria. However, it also forms symbiotic association with plants like mosquito fern. Hence, they are symbiotic bacteria as well.

Thus, the correct answer is 'Anabaena.'