ektomykorrhiza

Ectomycorrhiza (Czech: ektomykorrhiza) is a mutualistic symbiosis between certain soil fungi and the roots of many tree species, especially in temperate and boreal forests. In this association the fungal hyphae form a mantle around the root tip and create a network called the Hartig net between the epidermal and cortical cells, rather than penetrating the cell interiors as in arbuscular mycorrhiza.

The external mycelium extends into the surrounding soil, increasing the effective surface area for nutrient uptake. The plant supplies the fungus with carbohydrates produced by photosynthesis, while the fungus aids the host by absorbing mineral nutrients such as nitrogen and phosphorus, and improving water uptake.

Common ectomycorrhizal fungi belong mostly to Basidiomycota and some Ascomycota, including genera Amanita, Cortinarius, Russula, Suillus, Boletus, Laccaria and Paxillus. Many trees, including pines (Pinaceae), oaks (Quercus), beech (Fagus) and birch (Betula), form specific associations with particular fungal partners.

Ecologically, ectomycorrhizal symbiosis supports nutrient cycling, soil aggregation, and forest health. Mycelial networks can connect multiple plants, facilitating nutrient exchange and communication. The association is dynamic and can influence seedling establishment, competition, and responses to stress.

Fungi form fruiting bodies above ground, such as mushrooms, when conditions permit. Ectomycorrhizal relationships are distinct from arbuscular mycorrhiza, which colonizes root cortical cells intracellularly; in ectomycorrhiza the colonization is extracellular around the root tip rather than intracellular.