Select the mismatch:

Options

A. Rhodospirillum - Mycorrhiza
B. Anabaena - Nitrogen fixer
C. Rhizobium - Alfalfa
D. Frankia - Alnus

Explanation

To solve the question of selecting the mismatch among the given options, we will analyze each option one by one based on the information provided in the video transcript.

### Step-by-Step Solution:

1. **Analyze the First Option: Rhodospirillum mycorrhizae**
- **Rhodospirillum**: This is a genus of anaerobic bacteria that are known for their ability to fix nitrogen. They are free-living and do not form symbiotic relationships with other organisms.
- **Mycorrhizae**: This term refers to a symbiotic association between fungi and the roots of higher plants. Mycorrhizae are known for their mutualistic relationship with plants, aiding in nutrient absorption.
- **Mismatch**: Since Rhodospirillum does not form a symbiotic relationship (it is free-living), pairing it with mycorrhizae is incorrect. Therefore, this option is a mismatch.

2. **Analyze the Second Option: Anabina**
- **Anabina**: This refers to a genus of cyanobacteria (blue-green algae) that are known for their nitrogen-fixing capabilities. They possess the enzyme nitrogenase, which allows them to fix atmospheric nitrogen.
- **Correct Match**: Anabina is correctly identified as a nitrogen fixer, making this option correct.

3. **Analyze the Third Option: Rhizobium and Alfalfa**
- **Rhizobium**: This is a genus of bacteria that forms symbiotic relationships with leguminous plants, including Alfalfa. They live in the root nodules of these plants and are crucial for nitrogen fixation.
- **Correct Match**: The relationship between Rhizobium and Alfalfa is a well-known symbiotic association for nitrogen fixation, making this option correct.

4. **Analyze the Fourth Option: Francia and Alnus**
- **Francia**: This is another genus of nitrogen-fixing bacteria that forms a symbiotic relationship with the roots of Alnus (alder) trees.
- **Correct Match**: The association between Francia and Alnus is also a valid symbiotic relationship for nitrogen fixation, making this option correct.

### Conclusion:
The only mismatch identified is in the first option, **Rhodospirillum mycorrhizae**. The other options correctly represent nitrogen-fixing organisms and their symbiotic relationships.

### Final Answer:
**The mismatch is: Rhodospirillum mycorrhizae.**

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