Which of the following is non-symbiotic biofertilizer

Options

A. (a) Azotobacter
B. (b) Nostoc
C. (c) Rhizobium
D. (d) frankia

Answer

**Step-by-Step Solution:**

1. **Understanding Biofertilizers**: Biofertilizers are natural fertilizers that contain living microorganisms. They enhance the availability of nutrients to plants through biological processes.

2. **Types of Biofertilizers**: Biofertilizers can be classified into two categories: symbiotic and non-symbiotic.
- **Symbiotic biofertilizers** form a mutual relationship with plants, where both organisms benefit.
- **Non-symbiotic biofertilizers**, on the other hand, do not form such relationships; they help in nutrient fixation without receiving any benefits in return.

3. **Analyzing the Options**:
- **Option A: Azotobacter**: This is a free-living nitrogen-fixing bacterium. It does not form a symbiotic relationship with plants, meaning it is a non-symbiotic biofertilizer.
- **Option B: Nostoc**: This bacterium is known to form symbiotic relationships with certain plants, such as liverworts and ferns, thus it is not a non-symbiotic biofertilizer.
- **Option C: Rhizobia**: These bacteria form symbiotic relationships with leguminous plants, aiding in nitrogen fixation while receiving nutrients in return. Hence, they are also not non-symbiotic biofertilizers.
- **Option D: Frankia**: Similar to Rhizobia, Frankia forms symbiotic relationships with actinorhizal plants, which means it is not a non-symbiotic biofertilizer.

4. **Conclusion**: After analyzing all the options, the only non-symbiotic biofertilizer is **Azotobacter**.

5. **Final Answer**: The correct answer is **A: Azotobacter**.

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