Basidiospore

A basidiospore is a reproductive spore produced by basidiomycete fungi, a grouping that includes mushrooms, shelf fungi, rusts, and smuts. Basidiospores typically each contain one haploid nucleus that is the product of meiosis, and they are produced by specialized fungal cells called basidia. Typically, four basidiospores develop on appendages from each basidium, of which two are of one strain and the other two of its opposite strain. In gills under a cap of one common species, there exist millions of basidia. Some gilled mushrooms in the order Agaricales have the ability to release billions of spores.^[1] The puffball fungus Calvatia gigantea has been calculated to produce about five trillion basidiospores.^[2] Most basidiospores are forcibly discharged, and are thus considered ballistospores.^[3] These spores serve as the main air dispersal units for the fungi. The spores are released during periods of high humidity and generally have a night-time or pre-dawn peak concentration in the atmosphere.^[1]

When basidiospores encounter a favorable substrate, they may germinate, typically by forming hyphae. These hyphae grow outward from the original spore, forming an expanding circle of mycelium. The circular shape of a fungal colony explains the formation of fairy rings, and also the circular lesions of skin-infecting fungi that cause ringworm. Some basidiospores germinate repetitively by forming small spores instead of hyphae.^{[citation needed]}

General structure and shape

Basidiospores are generally characterized by an attachment peg (called a hilar appendage) on its surface. This is where the spore was attached to the basidium. The hilar appendage is quite prominent in some basidiospores, but less evident in others. An apical germ pore may also be present. Many basidiospores have an asymmetric shape due to their development on the basidium.^[3] Basidiospores are typically single-celled (without septa), and typically range from spherical to oval to oblong, to ellipsoid or cylindrical. The surface of the spore can be fairly smooth, or it can be ornamented.^[1] The color of the spore print is usually found in the spore wall, although in rare instances – like the yellow spores of Clavaria helicoides – the cytoplasm is responsible for the spore color.^[4]

Plages

A plage is a clear, unornamented area on the basal area of an otherwise ornamented basidiospore, next to its apiculus. It is also called a hilar depression.^[5] It plays an important role in the spore release of agarics, where it provides a place for water (called the adaxial drop) to condense on before the water merges with Buller's drop on the hilar appendix. It is characteristic of spores from the euagaric genus Galerina. It was first described by French mycologist Robert Kühner in 1926.^[6]

Plages are quite variable between different basidiomycetes. Rather than simplly a flat area above hilar appendix, some fungi have a dimple. This is called a suprahilar depression. These variations may happen because of structural differences in the gills or pores of different species, as they need different volumes of water, to disperse the spore.^[6]

There are four types of plages, based on how they react to Melzer's reagant. If the plage turns blue or black in reaction to Melzer's reagant, it can be classified as an amyloid plage. If it does not change colour, it is called an inamyloid plage. If the colour shows up only in the center, it is called centrally amyloid, respectively, if it shows up only on the outer edges of the plage, it is called distally amyloid.^[7] These characteristics can be useful in distinguishing between Lactarius species.^[8]

References

^ ^a ^b ^c Halbwachs, Hans; Bässler, Claus (2015). "Gone with the wind – a review on basidiospores of lamellate agarics" (PDF). Mycosphere. 6 (1): 78–112. doi:10.5943/mycosphere/6/1/10.
^ Li, De-Wei (2011). "Five trillion basidiospores in a fruiting body of Calvatia gigantia" (PDF). Mycosphere. 2 (4): 457–462.
^ ^a ^b Watkinson, Sarah C.; Boddy, Lynne; Money, Nicholas (2015). The Fungi. Academic Press. p. 86. ISBN 978-0-12-382035-8.
^ Donk, M.A. (1963). "A conspectus of the families of Aphyllophorales". Persoonia. 3 (3): 226.
^ Halbwachs, H (February 2015). "Gone with the wind – a review on basidiospores of lamellate agarics". Mycosphere. 6 (1): 78–112. doi:10.5943/mycosphere/6/1/10. ISSN 2077-7019.
^ ^a ^b Money, Nicholas P. (2023-01-01). "The fastest short jump in nature: Progress in understanding the mechanism of ballistospore discharge". Fungal Biology. 127 (1): 835–844. doi:10.1016/j.funbio.2023.01.001. ISSN 1878-6146.
^ Deshmukh, Sunil K.; Johri, B. N.; Satyanarayana, Tulasi, eds. (2017). Developments in Fungal Biology and Applied Mycology (1st ed. 2017 ed.). Singapore: Springer Singapore : Imprint: Springer. p. 490. ISBN 978-981-10-4768-8.
^ Verbeken, Annemieke; Walleyn, Ruben (2010). Monograph of Lactarius in tropical Africa. Fungus flora of tropical Africa. Jardin botanique national de Belgique. Meise: National Botanic Garden of Belgium. ISBN 978-90-72619-81-5.

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[Halbwachs_2015-1] Halbwachs, Hans; Bässler, Claus (2015). "Gone with the wind – a review on basidiospores of lamellate agarics" (PDF). Mycosphere. 6 (1): 78–112. doi:10.5943/mycosphere/6/1/10.

[Li_2011-2] Li, De-Wei (2011). "Five trillion basidiospores in a fruiting body of Calvatia gigantia" (PDF). Mycosphere. 2 (4): 457–462.

[Watkinson_2015-3] Watkinson, Sarah C.; Boddy, Lynne; Money, Nicholas (2015). The Fungi. Academic Press. p. 86. ISBN 978-0-12-382035-8.

[Donk_1963-4] Donk, M.A. (1963). "A conspectus of the families of Aphyllophorales". Persoonia. 3 (3): 226.

[5] Halbwachs, H (February 2015). "Gone with the wind – a review on basidiospores of lamellate agarics". Mycosphere. 6 (1): 78–112. doi:10.5943/mycosphere/6/1/10. ISSN 2077-7019.

[:0-6] Money, Nicholas P. (2023-01-01). "The fastest short jump in nature: Progress in understanding the mechanism of ballistospore discharge". Fungal Biology. 127 (1): 835–844. doi:10.1016/j.funbio.2023.01.001. ISSN 1878-6146.

[7] Deshmukh, Sunil K.; Johri, B. N.; Satyanarayana, Tulasi, eds. (2017). Developments in Fungal Biology and Applied Mycology (1st ed. 2017 ed.). Singapore: Springer Singapore : Imprint: Springer. p. 490. ISBN 978-981-10-4768-8.

[8] Verbeken, Annemieke; Walleyn, Ruben (2010). Monograph of Lactarius in tropical Africa. Fungus flora of tropical Africa. Jardin botanique national de Belgique. Meise: National Botanic Garden of Belgium. ISBN 978-90-72619-81-5.

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