basidia

Basidia are microscopic, club-shaped spore-producing cells found in the Basidiomycota, a major group of fungi that includes mushrooms, bracket fungi, and puffballs. They occur on the hymenial surface of basidiocarps (fruiting bodies), such as the gills of mushrooms, the pores of polypores, or other spore-bearing surfaces.

Each basidium typically bears four basidiospores, though the number can vary by species and sometimes within a genus. Basidia develop from dikaryotic hyphae in the basidiocarp. After karyogamy (fusion of nuclei) and subsequent meiosis inside the basidium, haploid basidiospores are produced and released. The spores are discharged through specialized projections called sterigmata and dispersed by wind or water to initiate new growth, germinating to form a new haploid mycelium that can unite with compatible mycelium to continue the life cycle.

Functionally, the basidium is the principal sexual reproductive structure of basidiomycetes, enabling the production and dissemination of sexual spores. Basidia and their spores are often visible only under a light microscope, but they are crucial for taxonomy and identification within Basidiomycota.

Ecologically, basidiomycetes play diverse roles, including wood decomposition, nutrient cycling, and forming mycorrhizal associations with plants. Some species are pathogens of plants or animals, while many others contribute to forest ecosystems as essential decomposers. Basidia thus serve as a key link in the life cycle and ecological function of basidiomycete fungi.