Bacteria showing loose association with root of certain grasses

Options

A. Rhizobia
B. Frankia
C. Azospirillum
D. Spirulina

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for the type of bacteria that shows a loose association with the roots of certain grasses. This implies we are looking for bacteria that are not strictly symbiotic but still interact with grass plants.

2. **Analyzing the Options**:
- **Option 1: Rhizobia**: Rhizobia are known for their symbiotic relationship with legumes, where they form root nodules and fix nitrogen. They do not associate with grasses, so this option is incorrect.
- **Option 2: Frankia**: Frankia is another nitrogen-fixing bacteria, but it also forms symbiotic relationships primarily with actinorhizal plants, not grasses. Therefore, this option is also incorrect.
- **Option 3: Azospirillum**: Azospirillum is known to form a loose association with the roots of various grasses and is involved in nitrogen fixation. This makes it a suitable candidate for the question.
- **Option 4: Spirulina**: Spirulina is not a bacteria associated with plant roots; it is a cyanobacterium used as a dietary supplement. Thus, this option is incorrect.

3. **Conclusion**: After analyzing all the options, the correct answer is **Option 3: Azospirillum**, as it is the only bacteria that shows a loose association with the roots of certain grasses.

**Final Answer**: The bacteria showing loose association with the root of certain grasses is **Azospirillum**.

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