Mycorrhizae are fungi that colonise plant roots.
Mycorrhizae (ancient Greek; mykos = fungus, rhiza = root) are fungi that associate with plant roots, and form a symbiotic relationship. The plant provides the fungus with carbohydrates, and the fungus increases the plant's access to water and certain nutrients. There are several types of mycorrhizal associations, the most important being ectomycorrhiza (EM) and arbuscular mycorrhiza (AM).
The ectotrophic (external) mycorrhizal fungi form a tight hyphal coat around thick, short, slow-growing plant roots. Root hairs are supressed, as their function is taken over by the fungus.
Arbuscular mycorrhizal fungi make up the most commonly observed type of mycorrhizal interaction. More than 80 percent of land plants live in symbiosis with AM-fungi. The hyphae of endotrophic fungi (greek; endo = inner) penetrate plant roots and form an open hyphal network. The hyphal structures that are formed inside the root itself are called arbuscules due to their shape (latin; arbusculum = small tree).