Plants having mycorrhizal association show

Options

A. Resistance to root-borne pathogens
B. Tolerance to salinity and drought
C. Nitrogen fixation
D. More than one option is correct

Answer

### Step-by-Step Solution:

1. **Understanding Mycorrhizal Association**:
- Mycorrhiza refers to the symbiotic association between fungi and plant roots. In this relationship, the fungi colonize the root system of a host plant.

2. **Benefits of Mycorrhizal Association**:
- The mycorrhizal fungi form a network of filaments that extend into the soil, which helps in nutrient and water absorption. This network allows the plant to access nutrients and water that are beyond the reach of its roots.

3. **Resistance to Pathogens**:
- One of the significant benefits of mycorrhizal association is that it provides resistance against root-borne pathogens. The presence of mycorrhizae can enhance the plant's defense mechanisms.

4. **Tolerance to Environmental Stress**:
- Mycorrhizal plants show increased tolerance to environmental stresses such as drought and salinity. The fungi help the plants to withstand these stresses by improving water and nutrient uptake.

5. **Nitrogen Fixation**:
- It is important to note that mycorrhizae do not perform nitrogen fixation. Nitrogen fixation is primarily carried out by certain bacteria (like cyanobacteria) and not by mycorrhizal fungi.

6. **Conclusion**:
- Based on the benefits provided by mycorrhizal associations, we can conclude that plants with mycorrhizal associations show resistance to root-borne pathogens and tolerance to salinity and drought. Thus, the correct answer to the question is that more than one option is correct (options 1 and 2).

### Final Answer:
**More than one option is correct (1 and 2)**.

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