Mycorrhiza does not help the host plant in: 1. enhancing its phosphorus uptake capacity 2. increasing its tolerance to drought 3. enhancing its resistance to root pathogens 4. increasing its resistance to insects

Options

A. enhancing its phosphorus uptake capacity
B. increasing its tolerance to drought
C. enhancing its resistance to root pathogens
D. increasing its resistance to insects

Explanation

To solve the question regarding the role of mycorrhiza in relation to host plants, we will analyze each of the options provided to determine which one mycorrhiza does not assist with.

### Step-by-Step Solution:

1. **Understanding Mycorrhiza**: Mycorrhiza refers to a symbiotic association between fungi and plant roots. This relationship is beneficial for the plant, as the mycorrhizae enhance nutrient uptake, particularly phosphorus.

2. **Analyzing Option 1**:
- **Enhancing phosphorus uptake capacity**: Mycorrhizae are well-known for increasing the phosphorus uptake capacity of host plants. They extend the root system and help in the absorption of phosphorus from the soil.
- **Conclusion**: Mycorrhiza helps in this aspect.

3. **Analyzing Option 2**:
- **Increasing tolerance to drought**: Mycorrhizae improve the water absorption capacity of plants, thus helping them tolerate drought conditions better.
- **Conclusion**: Mycorrhiza helps in this aspect.

4. **Analyzing Option 3**:
- **Enhancing resistance to root pathogens**: Mycorrhizae can help plants resist certain root pathogens, such as Fusarium, which causes root rot. They can provide a protective barrier and enhance the plant's immune response.
- **Conclusion**: Mycorrhiza helps in this aspect.

5. **Analyzing Option 4**:
- **Increasing resistance to insects**: Mycorrhizae do not provide direct resistance to insect pests. While they may improve overall plant health, they do not specifically enhance the plant's ability to resist insect attacks.
- **Conclusion**: Mycorrhiza does not help in this aspect.

### Final Answer:
Based on the analysis, the correct answer is **Option 4: increasing its resistance to insects**.

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