Mycelia

Mycelium, the plural mycelia, is the vegetative part of a fungus, consisting of a network of threadlike filaments called hyphae. This filamentous system grows by extending hyphal tips and exploring substrates such as soil, decaying wood, or plant material. Hyphae are usually reinforced with chitin and may be septate (divided by cross walls) or aseptate (lacking cross walls). Some mycelia form rhizomorphs, thick, rootlike strands that transport water and nutrients over gaps in the environment.

The primary ecological role of mycelia is nutrient acquisition. They secrete extracellular enzymes that break down complex organic matter, including cellulose and lignin, enabling the fungus to absorb nutrients. This makes fungi important decomposers in ecosystems and key players in nutrient cycling. Mycelia also engage in symbiotic relationships, most notably mycorrhizae, where fungal hyphae associate with plant roots to aid water and nutrient uptake in exchange for carbohydrates. Mycorrhizae are categorized as ectomycorrhizal, forming a sheath around roots, or arbuscular (endomycor rhizal), penetrating root cells.

Reproduction in fungi involves the mycelium as well. Asexual reproduction can occur by fragmentation of the hyphal network or by producing spores. Sexual reproduction typically leads to the formation of fruiting bodies, such as mushrooms or other structures, which generate spores for dispersal. The mycelium itself is usually not the visible reproductive stage; rather, it serves as the main growth and nutrient-absorbing body.

Humans interact with mycelia in various ways, including edible mushrooms, industrial enzyme production, and applications in bioremediation and biotechnology. Large, persistent mycelial networks can occupy extensive areas and contribute to ecosystem function.