Question:
Which of the following Cyanobacteria is found associated with both the lichens and the plants like Cycas and Azolla?
Which of the following Cyanobacteria is found associated with both the lichens and the plants like Cycas and Azolla?
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Symbiosis trick: Anabaena = Azolla + Cycas + Lichens (Nitrogen fixer).
Updated On: May 4, 2026
- Oscillatoria
- Tolypothrix
- Plectonema
- Anabaena
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The Correct Option is D
Solution and Explanation
Concept:
Certain cyanobacteria form symbiotic associations with other organisms. These associations are important for nitrogen fixation.
Step 1: Understand symbiotic associations.
• In Azolla (aquatic fern) → Anabaena is present in leaf cavities
• In Cycas → Anabaena is found in coralloid roots
• In lichens → Cyanobacteria like Anabaena act as phycobionts (photosynthetic partners)
Step 2: Identify the common cyanobacterium. Anabaena is well known for forming symbiotic relationships in all the above cases and also fixes atmospheric nitrogen.
Step 3: Analyze the given options.
• (A) Oscillatoria → Free-living cyanobacteria $\times$
• (B) Tolypothrix → Not commonly associated with all listed symbioses $\times$
• (C) Plectonema → Not involved in these associations $\times$
• (D) Anabaena → Forms symbiosis with Azolla, Cycas, and lichens \checkmark
Step 4: Conclusion. Thus, the correct cyanobacterium is: \[ \text{Anabaena} \]
Certain cyanobacteria form symbiotic associations with other organisms. These associations are important for nitrogen fixation.
Step 1: Understand symbiotic associations.
• In Azolla (aquatic fern) → Anabaena is present in leaf cavities
• In Cycas → Anabaena is found in coralloid roots
• In lichens → Cyanobacteria like Anabaena act as phycobionts (photosynthetic partners)
Step 2: Identify the common cyanobacterium. Anabaena is well known for forming symbiotic relationships in all the above cases and also fixes atmospheric nitrogen.
Step 3: Analyze the given options.
• (A) Oscillatoria → Free-living cyanobacteria $\times$
• (B) Tolypothrix → Not commonly associated with all listed symbioses $\times$
• (C) Plectonema → Not involved in these associations $\times$
• (D) Anabaena → Forms symbiosis with Azolla, Cycas, and lichens \checkmark
Step 4: Conclusion. Thus, the correct cyanobacterium is: \[ \text{Anabaena} \]
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