Mykorrhiza

Mycorrhiza is a symbiotic association between a fungus and plant roots that enhances nutrient and water uptake in exchange for carbon from the plant. In most land plants, mycorrhizal associations are common and influential for growth and health.

There are several main types, among them ectomycorrhiza and arbuscular mycorrhiza (AM). In ectomycorrhiza, fungal hyphae form a dense mantle around the root tip and grow between root cells to form a Hartig net, while AM fungi colonize root cortical cells and produce arbuscules inside cells; AM hyphae extend into the soil, greatly increasing the absorptive surface area.

Plants supply carbon to the fungus in the form of sugars. The fungi help acquire nutrients such as phosphorus, nitrogen, and micronutrients, and improve water uptake. In exchange, plants receive increased nutrient status, better drought tolerance, and sometimes enhanced disease resistance. AM is the most widespread form and associates with the majority of herbaceous plants and many crops; ectomycorrhizal associations are common in trees and many forest ecosystems. Other forms include ericoid and orchid mycorrhizas, adapted to specific plant lineages.

Ecological significance: mycorrhizas contribute to soil structure via hyphal networks, influence plant community dynamics, and play a role in nutrient cycling. They can be affected by soil fertility, pH, and disturbance. In agriculture, inoculants and practices that preserve mycorrhizal networks aim to reduce fertilizer inputs, though colonization depends on plant species, soil conditions, and management.

History: the concept was formalized in the late 19th century by Albert Bernhard Frank, who described the fungal–plant root association that would later be termed mycorrhiza.