Question

Which nitrogen-fixing bacteria forms a symbiotic relationship with the water fern Azolla?

• A. Rhizobium
• B. Azotobacter
• C. Anabaena
• D. Clostridium

Hint:

Azolla + Anabaena → Symbiotic nitrogen fixation → Used as biofertilizer.

Answer 1

The Correct Option is C

Concept: Nitrogen fixation is an essential biological process in which atmospheric nitrogen is converted into a usable form like ammonia. Certain microorganisms form symbiotic relationships with plants to carry out this function.
Step 1: Understanding Azolla symbiosis.
Azolla is an aquatic fern that forms a symbiotic association with nitrogen-fixing microorganisms.
Step 2: Identifying the microorganism.
Anabaena, a cyanobacterium (blue-green algae), resides in the leaf cavities of Azolla and fixes atmospheric nitrogen.
Step 3: Significance of this relationship.

• Enriches soil with nitrogen
• Widely used as a biofertilizer in paddy fields

Step 4: Eliminating other options.

• Rhizobium: Symbiotic with leguminous plants
• Azotobacter: Free-living nitrogen fixer
• Clostridium: Anaerobic nitrogen fixer

Step 5: Conclusion.
Thus, Anabaena forms a symbiotic relationship with Azolla.