ectomycorrhizal

Ectomycorrhizal (ECM) refers to a symbiotic association between certain fungi and the roots of many trees and woody shrubs. In ECM relationships, fungal hyphae form a mantle around the root tip and extend into the outer root cortex to create a Hartig net, while extensive external mycelium grows through the soil. This arrangement increases the root's surface area for nutrient uptake without penetrating plant cells.

ECM fungi are primarily basidiomycetes and some ascomycetes. They include genera such as Amanita, Cortinarius, Suillus, Rhizopogon, Paxillus, Russula, Laccaria, and Cenococcum geophilum. ECM associations are common on temperate and boreal trees, including pines, oaks, birches, spruces, firs, and beeches. Many ECM fungi produce fruiting bodies, or mushrooms, which contribute to forest litter and nutrient cycling.

Nutritionally, the plant provides carbon to the fungus, and in return ECM fungi supply minerals such as nitrogen and phosphorus and sometimes other micronutrients. They can access organic nutrient pools and assist with nutrient uptake under nutrient-poor conditions. ECM also often improves drought tolerance and resistance to certain root pathogens. Through networked mycelia, ECM fungi can connect neighboring plants, enabling potential carbon transfer and interplant signaling.

ECM is a key factor in seedling establishment and forest productivity and is influenced by soil chemistry, moisture, and disturbance. It is distinguished from arbuscular mycorrhiza by not penetrating root cells and by forming Hartig nets instead of intracellular arbuscules.