Select the mismatch

Options

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

Answer

To solve the question of selecting the mismatch from the given options related to mineral nutrition, we will analyze each option step by step.

### Step-by-Step Solution:

1. **Understanding the Options:**
- The options provided are:
- A) Francia
- B) Rhodospirillum
- C) Mycorrhiza
- D) Anabina
- E) Rhizobium
- F) Alpha-alpha

2. **Analyzing Each Option:**
- **Option A: Francia**
- Francia is a nitrogen-fixing bacterium that forms a symbiotic relationship with the plant Alnus (alders). This option is correct.

- **Option B: Rhodospirillum**
- Rhodospirillum is a facultative anaerobe that can fix nitrogen, but it does not form a symbiotic relationship with plant roots like mycorrhizae do. Thus, this option is likely the mismatch.

- **Option C: Mycorrhiza**
- Mycorrhiza refers to the symbiotic association between fungi and plant roots, which is a well-established relationship. This option is correct.

- **Option D: Anabina**
- Anabina is a filamentous cyanobacterium known for its nitrogen-fixing ability. It exists as plankton and is correctly associated with nitrogen fixation. This option is correct.

- **Option E: Rhizobium**
- Rhizobium is a genus of bacteria that forms root nodules in leguminous plants (like Alpha-alpha) and is crucial for nitrogen fixation. This option is correct.

- **Option F: Alpha-alpha**
- Alpha-alpha (Medicago sativa) is a leguminous plant that forms a symbiotic relationship with Rhizobium for nitrogen fixation. This option is correct.

3. **Identifying the Mismatch:**
- After analyzing all the options, we find that **Option B: Rhodospirillum** is the mismatch because it does not form a symbiotic relationship with plant roots, unlike mycorrhizae.

### Final Answer:
The mismatch is **Option B: Rhodospirillum**.