Mycorrhizae function

Mycorrhizae is a fungus that grows on the roots of plants. It can serve a symbiotic, or sometimes pathogenic, relationship for plants. The mycorrhizae grows on the roots of plants and helps the plants to absorb water and nutrients from the soil easier. In exchange for increasing the effeciency of the plant's root system, the mycorrhizae syphons a small portion of the plants carbohydrates that it forms during photosynthesis.  This way the mycorrhizae increases the survivability of the plant while the plant increases the survivability of the mycorrhizae. This relationship is symbiotic when the plant is able to successfully perform photosynthesis. However, the relationship can become slightly pathogenic for the plant if it is unable to perform photosynthesis. This is because while the plant is receiving the nutrients it needs, it is also being drained of what little carbohydrates it has by the mycorrhizae.