Mycorrhiza

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A mycorrhiza (typically seen in the plural form mycorrhizae meaning "fungus roots") is a distinct type of root symbiosis in which individual hyphae extending from the mycelium of a fungus colonize the roots of a host plant. Different sorts of fungal structures are found in mycorrhizal trees and in roots of most herbaceous plants. These fungi belong to a group called ectomycorrhizae and endomycorrhizae respectively, forming mycorrhizal networks, which can be detected in the soil organic layers.

Mycorrhizae form a mutualistic symbiotic relationship with the roots of 95% of all vascular plants. This association provides the fungus with a renewable source of food by continuous access to plant assimilates that are mobilized from leaves to root tissues and then to the fungal partners, and allows the plant to make use of the mycelium's tremendous surface area to absorb nutrients from the soil.

Mycorrhizal fungi explore a larger volume of soil than root systems at a lower cost to the plant. Some of the earliest fossil plants show evidence of mycorrhizae associated with them. Mycorrhizal plants are generally more resistant to diseases e.g. caused by microbial soil-borne pathogens, and are also more resistant to the effects of drought.

Some mycorrhizal hyphae enter within the plant cell's wall and grow to envelop the cell. However, most mycorrhizae have a more advanced structure, in which the hypha lives inside an extensive invagination (inpocketing) of the cell membrane.