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Basidium, the plural form being basidia, is a microscopic, spore-producing structure found on the basidiocarp (mushroom, fruiting body, basidioma) of basidiomycete fungi. The presence of basidia is one of the main characteristic features of the group. The basidium is a club-shaped structure with 2–4 apical sterigmata that bear basidiospores. The basidiospores are forcibly expelled from the basidium, which is the site of karyogamy and meiosis, where sex cells fuse, exchange nuclear material, and divide to reproduce basidiospores.
| Characteristics | Values |
|---|---|
| Definition | A basidium is a microscopic, spore-producing structure found on the basidiocarp (mushroom, fruiting body, basidioma) of basidiomycete fungi. |
| Shape | Club-shaped |
| Number of spores | 2, 4 or 8 |
| Spore expulsion | Basidiospores are forcibly expelled due to a sudden change in the center of gravity of the discharged spore. |
| Spore dispersal | Spore dispersal occurs through forcible expulsion or other means such as insect vectors, splash cup mechanisms, or disturbance of basidiocarps. |
| Mating strains | Two different mating strains are required for the fusion of genetic material in the basidium. |
| Dikaryotic stage | The dikaryotic stage is dominant in the basidiomycete life cycle, where the fungus remains until a basidiocarp (mushroom) is generated. |
| Basidiocarp | The basidiocarp is the fruiting body of a mushroom-producing fungus, bearing the developing basidia on the gills under its cap. |
| Examples | Mushrooms, shelf fungi, smuts, rusts, and toadstools. |
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What You'll Learn
Basidium is a microscopic, spore-producing structure
A basidium is a microscopic, spore-producing structure found on the basidiocarp (mushroom) of basidiomycete fungi. The presence of basidia is one of the main characteristics of the Basidiomycota phylum, which includes approximately 23,000 species of fungi, many of which are common macroscopic forest fungi such as mushrooms and shelf fungi. Basidia are the reproductive organs of these fungi and are often contained within the familiar mushroom.
Basidia are club-shaped cells that bear sexual spores called basidiospores. Each basidium usually has four sterigmata, which are small projections at the tip of the basidium that bear the basidiospores. The number of sterigmata can vary from two to eight. Basidiospores are produced through the fusion of nuclei from two different mating strains of mycelia, followed by meiosis. The basidiospores are then forcefully expelled from the basidium due to a sudden change in the centre of gravity caused by the buildup of fluid at the tip of each spore.
Basidiomycetes can be further classified into two groups based on the morphology of the basidium: Phragmobasidiomycetes (Heterobasidiomycetes) and Homobasidiomycetes (Holobasidiomycetes). Fungi possessing septate basidia, or divided cells, are assigned to the Phragmobasidiomycetes, while fungi with non-septate basidia are classified in the Homobasidiomycetes. Gilled mushrooms, boletes, polypores, chanterelles, and certain types of crust fungi have a type of basidium called a homobasidium. Other basidiomycetes, such as jelly fungi, rusts, smuts, and the genus Tremella, have different types of basidia called phragmobasidia or heterobasidia.
Basidiomycetes typically have a prolonged stage in their life cycle where two nuclei (dikaryon) are present in the hyphae. This is known as the dikaryotic stage, during which the fungus remains haploid until the formation of the basidium. The secondary mycelium, which is formed by the combination of mycelia of different mating strains, supports the development of the basidium. The basidiocarp, or the fruiting body of the mushroom, bears the developing basidia on the gills under its cap.
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Basidiospores are forcibly expelled
Basidiospores are the sexual spores of basidiomycete fungi, which include many common macroscopic forest fungi, such as mushrooms, shelf fungi, smuts, rusts, and toadstools. Most edible fungi belong to the phylum Basidiomycota, but some basidiomycetes produce deadly toxins. Basidiospores are typically single-celled and range from spherical to oval to oblong, to ellipsoid or cylindrical. They are of various colours, shapes, sizes, and arrangements, and are one of the most useful features in mushroom taxonomy.
The forcible discharge of basidiospores is derived from a sudden change in the centre of gravity of the discharged spore. This occurs when two bodies of water, one in the form of Buller's drop, a large, almost spherical water droplet at the tip of the spore, and another in the form of condensation on the stalk-facing part of the spore, combine. The release of surface tension and the sudden change in the centre of gravity lead to the forceful expulsion of the basidiospore. The initial acceleration of the spore is estimated to be about 10,000 g.
Basidiospores are considered ballistospores, serving as the main air dispersal units for the fungi. They are released during periods of high humidity and generally have a night-time or pre-dawn peak concentration in the atmosphere. When basidiospores encounter a favourable substrate, they may germinate, typically by forming hyphae. Some basidiospores germinate repetitively by forming small spores instead of hyphae.
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Basidiomycetes have both sexual and asexual spores
A basidium (plural: basidia) is a microscopic, spore-producing structure found on the hymenophore of reproductive bodies of basidiomycete fungi. The presence of basidia is one of the main characteristic features of the group. The basidium is a club-like structure with 2–4 apical sterigmata that bear basidiospores. The word "basidium" means "little pedestal", referring to the way the basidium supports the spores. However, some biologists suggest that the structure looks more like a club.
Basidiomycetes are a group of fungi that produce spores from a basidium. The Basidiomycota is a taxonomic division within the kingdom Fungi, including approximately 23,000-30,000 species of fungi. Most edible fungi belong to this phylum, but some basidiomycetes produce deadly toxins. The group is characterized by having meiospores (basidiospores) that are produced on club-shaped cells or basidia. The morphology of the basidium has played a central role in past classifications of the Basidiomycota.
Basidiospores are forcibly expelled from the basidium when the spores reach full growth. The propulsive force is derived from a sudden change in the center of gravity of the discharged spore. Important factors in forcible discharge include Buller's drop, a drop of fluid that builds up at the tip of each basidiospore; the offset attachment of the spore to the extending narrow prong; and the presence of hygroscopic regions on the basidiospore surface. Basidiospore discharge can only succeed after sufficient water vapour has condensed on the spore.
Some basidiomycetes do not have a means to forcibly expel their basidiospores, but they still form them. In these cases, spore dispersal occurs through other means. For example, members of the order Phallales (stinkhorns) rely on insect vectors for dispersal, while the dry spores of the Lycoperdales (puffballs) and Sclerodermataceae (earth balls) are dispersed when the basidiocarps are disturbed.
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Basidiomycota is the second-largest phylum of Kingdom Fungi
Basidia are borne on fruiting bodies (basidiocarps), which are large and conspicuous in all but the yeasts, rusts, and smuts. The mushroom basidiocarp consists of a cap (pileus) and a stalk (stipe). The pileus is lined with gills, which in turn are lined with basidia. The stipe of some basidiocarps has a volva (a remnant of the universal veil that once enveloped the entire developing mushroom) at the base. The basidiomycota includes smuts and rusts, which are important plant pathogens, and toadstools. Most edible fungi belong to the Phylum Basidiomycota; however, some basidiomycetes produce deadly toxins.
Basidiomycetes often produce large, spectacular fruiting structures; others are known for their hallucinogenic properties. Like ascomycetes, basidiomycetes occupy a variety of niches. Mushrooms are classified in this phylum, as are highly important plant pathogens, the rust and smut fungi. Basidiomycetes have a well-developed septate mycelium that has chitin in the cell wall. These organisms may spend a majority of their life cycle as dikaryotes, where each cell contains two different haploid nuclei.
Basidiomycete yeasts are known to be lichen symbionts, together with unrelated fungi (typically ascomycetes) and green algae or cyanobacteria. These yeasts are found in the cortex of many macrolichens. Basidiomycota can reproduce asexually. Basidiomycota that reproduce asexually can typically be recognized as members of this division by gross similarity to others, by the format of their microscopic morphological differences, and variations in life cycles.
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Basidiocarp is the fruiting body of a mushroom-producing fungus
A basidium is a microscopic, spore-producing structure found on the basidiocarp (mushroom) of basidiomycete fungi. The basidium is a club-like structure with 2–4 apical sterigmata that bear basidiospores. The basidiospores are forcefully expelled at full growth. The presence of basidia is one of the main characteristic features of the Basidiomycota phylum of fungi.
Basidiomycota is the second-largest phylum of Kingdom Fungi, with approximately 23,000 species. The group is characterised by having meiospores (basidiospores) that are produced on club-shaped cells or basidia. The morphology of the basidium has played a central role in past classifications of the Basidiomycota, with fungi possessing septate basidia assigned to the Phragmobasidiomycetes (Heterobasidiomycetes) and fungi with non-septate basidia classified in the Homobasidiomycetes (Holobasidiomycetes).
Basidiocarps are the fruiting bodies of members of the subphylum Agaricomycotina in which spore-producing hymenia are borne and form the typical mushroom-shaped structures commonly seen in nature. Basidiocarps are characteristic of the hymenomycetes; rusts and smuts do not produce such structures. As with other sporocarps, epigeous (above-ground) basidiocarps that are visible to the naked eye are commonly referred to as mushrooms, while hypogeous (underground) basidiocarps are usually called false truffles. All basidiocarps serve as the structure on which the hymenium is produced. Basidia are found on the surface of the hymenium, and the basidia ultimately produce spores.
Basidiocarp morphology has been used in traditional classifications of homobasidiomycetous fungi, with a particular focus on the spore-producing region or hymenophore. For example, all mushrooms and their gilled relatives were grouped in the Agaricales, while all poroid forms and their relatives were grouped in the Aphyllophorales. However, phylogenetic analyses of molecular data from both nuclear and mitochondrial genomes do not support these classifications.
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Frequently asked questions
A basidium is a microscopic, spore-producing structure found on the basidiocarp (mushroom, fruiting body, basidioma) of basidiomycete fungi.
The basidium is a club-like structure with 2-4 apical sterigmata that bear basidiospores.
Basidiomycetes are fungi of the phylum Basidiomycota, which produce sexual spores on a basidium.
Basidiospores are the sexually reproduced bodies produced on the basidium. They are forcibly expelled when the basidiospore reaches maturity.
A basidiocarp is a mushroom or a fruiting body that protrudes from the ground. It bears the developing basidia on the gills under its cap.
