Which of the following is a non-symbiotic biofertillizer?

Options

A. Mycorrhizae
B. Azotobacter
C. Anabaena
D. Rhizobium

Answer

To determine which of the following is a non-symbiotic biofertilizer, we need to analyze each option based on their characteristics and relationships with plants.

1. **Understanding Biofertilizers**: Biofertilizers are microorganisms that enhance soil fertility through their metabolic activities. They can be classified into symbiotic and non-symbiotic based on their relationship with plants.

2. **Identifying Symbiotic vs. Non-symbiotic**:
- **Symbiotic Organisms**: These organisms live in close association with plants and both benefit from this relationship.
- **Non-symbiotic Organisms**: These organisms do not form a close association with plants and can live independently while still providing benefits, such as nitrogen fixation.

3. **Analyzing Each Option**:
- **A. Mycorrhizae**: This is a type of fungus that forms a symbiotic relationship with plant roots. The fungus helps the plant absorb nutrients, especially phosphorus, while the plant provides carbohydrates to the fungus. Therefore, Mycorrhizae is a symbiotic biofertilizer.
- **B. Azotobacter**: This is a free-living bacterium that fixes nitrogen from the atmosphere into a form that plants can use. It does not require a symbiotic relationship with plants to function, making it a non-symbiotic biofertilizer.
- **C. Anabaena**: This is a blue-green algae that can form symbiotic relationships with certain plants (like in the case of water ferns). It also fixes nitrogen, but it is known for its symbiotic associations, so it is not a non-symbiotic biofertilizer.
- **D. Rhizobium**: This bacterium forms a symbiotic relationship with leguminous plants, fixing nitrogen in root nodules. Thus, it is also a symbiotic biofertilizer.

4. **Conclusion**: Based on the analysis, the only non-symbiotic biofertilizer among the options is **B. Azotobacter**.

### Steps Summary:
1. Define biofertilizers and their role in soil fertility.
2. Distinguish between symbiotic and non-symbiotic organisms.
3. Evaluate each option based on their relationships with plants.
4. Identify Azotobacter as the non-symbiotic biofertilizer.