Hyphae

Hyphae are the thread-like filaments that make up the body (mycelium) of most fungi. They are typically microscopic and grow by extending tips, branching to explore new substrates. Hyphae are the main means by which fungi absorb nutrients, secreting enzymes into their surroundings and taking up small molecules through their membranes.

Most fungi have septate hyphae, which are divided into compartments by cross-walls called septa that have pores allowing cytoplasm, organelles, and sometimes nuclei to move between compartments. Some fungi have coenocytic hyphae, which lack septa and are essentially multinucleate tubes. The cell wall of hyphae is primarily composed of chitin and glucans. Growth at the tip is guided by a vesicle-rich region called the Spitzenkörper, which coordinates extension and branching.

Hyphae can be organized into different structural forms. In monomitic species one type of hypha is present; dimitic species have two types (often generative plus skeletal or binding hyphae), and trimitic species have three. Generative hyphae are typically thin-walled and capable of forming reproductive structures; skeletal hyphae provide rigidity; binding hyphae form dense networks that help consolidate the structure.

Ecologically, hyphae enable fungi to decompose organic material and form mutualistic associations such as mycorrhizae with plant roots. They also participate in pathogenic interactions with plants and animals. Hyphae frequently grow into aerial structures that produce spores for reproduction, and networks can undergo hyphal fusion (anastomosis) to connect separate mycelia and share resources. In many fungi, the hyphal state includes diverse nuclear conditions, from haploid to dikaryotic phases, depending on the species and life cycle stage.