Introduction:
Mycorrhiza is a functional association between fungi and the roots of higher plants. It is considered as a mutualistic symbiotic relationship where both parties benefit from the association.

Explanation:
Mycorrhiza plays a crucial role in enhancing the plant's ability to absorb nutrients and water from the soil. Here is a detailed explanation of the benefits of mycorrhizal association:

1. Nutrient uptake:
Mycorrhizal fungi form a network of fine filaments called hyphae, which extend into the soil and increase the surface area for nutrient absorption. These hyphae have a higher efficiency in extracting nutrients such as nitrogen, phosphorus, and micronutrients from the soil. The fungi transfer these nutrients to the plant roots, enhancing their nutrient uptake capacity.

2. Water absorption:
The extensive network of mycorrhizal hyphae also helps in increasing the plant's ability to absorb water from the soil. The hyphae can penetrate small pores and cracks in the soil, reaching water sources that are inaccessible to plant roots alone. This improves the plant's drought tolerance and water absorption efficiency.

3. Disease resistance:
Mycorrhizal association enhances the plant's defense mechanisms against pathogens. The fungi produce antifungal compounds that can inhibit the growth of pathogenic organisms in the soil. They also stimulate the plant's immune response, making it more resistant to diseases.

4. Soil structure and aggregation:
Mycorrhizal fungi play a significant role in improving soil structure and aggregation. The hyphae form a network that binds soil particles together, creating stable aggregates. This improves soil porosity, aeration, and water infiltration, leading to better root growth and nutrient availability.

5. Environmental stress tolerance:
Plants with mycorrhizal association have shown increased tolerance to various environmental stresses such as drought, salinity, heavy metals, and extreme temperatures. The fungi help the plant in coping with these stress conditions by improving nutrient uptake, water absorption, and overall plant health.

Conclusion:
Mycorrhizal association is a beneficial functional association between fungi and the roots of higher plants. It enhances nutrient uptake, water absorption, disease resistance, soil structure, and environmental stress tolerance. This association plays a crucial role in improving plant growth, health, and overall ecosystem functioning.