Ectomykorrhiza

Ectomycorrhiza is a type of mycorrhizal symbiosis formed between many woody plants and specialized fungi. In this association, fungal hyphae envelop the root tips with a sheath called the mantle and extend into the surrounding soil as a dense extraradical mycelium. Within the root, the hyphae do not penetrate plant cells; instead, they form a Hartig net between the epidermal and outer cortical cells.

The symbiotic exchange involves the plant supplying carbon compounds to the fungus, while the fungus enhances the plant’s access to water and nutrients. Ectomycorrhizal fungi help uptake mineral nutrients, particularly phosphorus and nitrogen, and can improve uptake of micronutrients and water, contributing to drought tolerance and disease resistance in some cases. The relationship is generally mutualistic, though the balance of benefit varies with species, soil conditions, and nutrient availability.

Many woody species form ectomycorrhizas, including pines, spruces, firs, oaks, birches, beech, and certain eucalypts in some regions. The fungal partners are mainly basidiomycetes, with notable genera such as Amanita, Cortinarius, Russula, Boletus, and Cenococcum geophilum; some ascomycetes also form ectomycorrhizas. Extraradical mycelium can connect multiple roots, influencing forest stand structure and nutrient cycling.

Ecologically, ectomycorrhizas play a central role in temperate and boreal forest ecosystems, enhancing seedling establishment, growth, and resilience. They are also used in forestry and restoration to improve transplant survival and growth by promoting robust plant–fungus partnerships.