The structures formed through the close association of plant roots and fungi are called mycorrhizae.
One of the oldest types is arbuscular mycorrhizae (AM), also known as endomycorrhizae, in which fungal hyphae enter the root and form connections within its tissues.
It is thought that the ancestors of plants that first moved from the oceans onto land developed this relationship to obtain nutrients and water.
By contrast, fungi that form ectomycorrhizae surround the outside of plant roots with a sheath of fungal hyphae. This is often compared to a “sock” wrapped around the root.
Another characteristic of ectomycorrhizal fungi is that they produce mushrooms.
The fungi that form arbuscular mycorrhizae produce neither these root sheaths nor mushrooms.
Which type of mycorrhizal relationship a plant forms is largely determined by the plant species. The type of forest itself is also closely connected to these underground partnerships.
