mycelium

Mycelium is the vegetative part of a fungus, consisting of a vast network of thread-like filaments called hyphae. In most fungi, hyphae grow underground or within a substrate, collectively forming a mycelium that can span large areas. Hyphae are typically divided by septa and have cell walls made of chitin, although some species possess coenocytic, or aseptate, hyphae with continuous cytoplasm.

Mycelium absorbs nutrients by secreting enzymes that break down complex organic matter and then taking up the released compounds. The extensive surface area of the hyphal network enables efficient decomposition and nutrient acquisition, supporting growth and reproduction. Hyphae can aggregate into thicker cords or nutritious networks as needed, guiding exploration of distant resources. Growth occurs by tip extension and branching in response to environmental cues such as moisture, temperature, and nutrient availability.

Ecologically, mycelium plays a central role as a decomposer and nutrient recycler in ecosystems. Many fungi form mutualistic mycorrhizal associations with plants, exchanging soil minerals and sugars for improved plant growth. Mycelia can also act as endophytes within plant tissues or, in some species, as pathogens.

Humans interact with mycelium in several ways. Edible mushrooms are cultivated from mycelial networks, and mycelium-based processes and materials are studied for bioremediation, soil restoration, and sustainable composites. The fungal life cycle also includes the production of fruiting bodies, such as mushrooms, which release spores for dispersion.