A basidium (PL: basidia) is a microscopic spore-producing structure found on the hymenophore of reproductive bodies of basidiomycete fungi. These bodies also called tertiary mycelia, which are highly coiled versions of secondary mycelia. The presence of basidia is one of the main characteristic features of the genus. A basidium usually bears four sexual spores called basidiospores. Occasionally the number may be two or even eight. Each reproductive spore is produced at the tip of a narrow prong or horn called a sterigma (PL sterigmata), and is forcefully expelled at full growth.
Diagram showing a basidiomycete mushroom, gill structure, and spore-bearing basidia on the gill margins.
The word basidium literally means "little pedestal". This is the way the basidium supports the spores. However, some biologists suggest that the structure looks more like a club. A partially grown basidium is known as a basidiole.
Most basidiomycota have single celled basidia (holobasidia), but some have ones with many cells (a phragmobasidia). For instance, rust fungi in the order Puccinales have phragmobasidia with four cells that are separated by walls along their cross section. Some jelly fungi in the order Tremellales also have phragmobasidia with four cells that are separated by walls and are shaped like a cross. Sometimes the basidium develops from a probasidium, which is not elongated like a typical hypha. The basidium may be stalked or attached directly to the hyphae.
The basidium is normally club-shaped: narrow at the stem and wide near its outer end. It is widest in the middle hemispherical dome at its apex, and its base is about half the size of the widest diameter at the highest point. Basidia with a short and narrow base are shaped like an inverted egg, and occur in genera such as Paullicorticium, Oliveonia, and Tulasnella. Basidia with a wide base are often shaped like a barrel.[1]
How basidiospores are expelledEdit
In most basidiomycota, the basidiospores are forcibly expelled. 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 nearer tip (hilar appendage) 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 vapor has condensed on the spore.
When a basidiospore matures, sugars present in the cell wall begin to serve as condensation loci for water vapour in the air. Two separate regions of condensation are critical. At the pointed tip of the spore (the hilum) closest to the supporting basidium, Buller's drop builds up as a large, almost spherical water droplet.
At the same time, condensation occurs in a thin film on the stalk-facing part of the spore. When these two bodies of water combine, the release of surface tension and the sudden change in the center of gravity suddenly expels the basidiospore. Remarkably, the initial acceleration of the spore is estimated to be about 10,000 g.[2]
Evolutionary loss of expulsion by forceEdit
Some basidiomycetes do not have a means to forcibly expel their basidiospores, although they still form them. In each of these groups, spore dispersal occurs through other means of expulsion.
Species of the Nidulariales (bird's nest fungi) use a splash cup mechanism.
In these cases the basidiospore typically lacks a hilar appendage, and expulsion by force does not occur. Each example is thought to represent an independent evolutionary loss of the forcible discharge that comes before all basidiomycetes.
ReferencesEdit
^ Donk, M.A. (1963). "A conspectus of the families of Aphyllophorales". Persoonia. 3 (3): 214.
^ Money, N.P. (1998). "More g's than the Space Shuttle: Ballistospore discharge". Mycologia. 90 (4): 547–558. doi:10.1080/00275514.1998.12026942.
Ingold, C.T. (1991). "A view of the active basidium in heterobasidiomycetes". Mycological Research. 95 (5): 618–621. doi:10.1016/S0953-7562(09)80076-2.
Pringle, A.; Patek, S.N.; Fischer, M.; Stolze, J.; Money, N.P. (2005). "The captured launch of a ballistospore". Mycologia. 97 (4): 866–871. doi:10.1080/15572536.2006.11832777. PMID 16457355. S2CID 218586848.
External linksEdit
AmericanMushrooms.com: How do fungi reproduce?
by John Webster. Mycological Society of America Lab Manual
IMA Mycological Glossary: Basidum
Spore discharge and dispersal in mushrooms by Heino Lepp, Australian National Botanic Gardens.
"Using a Microscope: Basidia and Cystidia" by Michael Kuo, MushroomExpert.com
October 20, 2023
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For the fictional moon in novels by Eleanor Cameron see Mushroom Planet This article includes a list of general references but it lacks sufficient corresponding inline citations Please help to improve this article by introducing more precise citations March 2013 Learn how and when to remove this template message A basidium PL basidia is a microscopic spore producing structure found on the hymenophore of reproductive bodies of basidiomycete fungi These bodies also called tertiary mycelia which are highly coiled versions of secondary mycelia The presence of basidia is one of the main characteristic features of the genus A basidium usually bears four sexual spores called basidiospores Occasionally the number may be two or even eight Each reproductive spore is produced at the tip of a narrow prong or horn called a sterigma PL sterigmata and is forcefully expelled at full growth Diagram showing a basidiomycete mushroom gill structure and spore bearing basidia on the gill margins The word basidium literally means little pedestal This is the way the basidium supports the spores However some biologists suggest that the structure looks more like a club A partially grown basidium is known as a basidiole Contents 1 Structure 2 How basidiospores are expelled 2 1 Evolutionary loss of expulsion by force 3 References 4 External linksStructure EditMost basidiomycota have single celled basidia holobasidia but some have ones with many cells a phragmobasidia For instance rust fungi in the order Puccinales have phragmobasidia with four cells that are separated by walls along their cross section Some jelly fungi in the order Tremellales also have phragmobasidia with four cells that are separated by walls and are shaped like a cross Sometimes the basidium develops from a probasidium which is not elongated like a typical hypha The basidium may be stalked or attached directly to the hyphae The basidium is normally club shaped narrow at the stem and wide near its outer end It is widest in the middle hemispherical dome at its apex and its base is about half the size of the widest diameter at the highest point Basidia with a short and narrow base are shaped like an inverted egg and occur in genera such as Paullicorticium Oliveonia and Tulasnella Basidia with a wide base are often shaped like a barrel 1 How basidiospores are expelled EditIn most basidiomycota the basidiospores are forcibly expelled 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 nearer tip hilar appendage 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 vapor has condensed on the spore When a basidiospore matures sugars present in the cell wall begin to serve as condensation loci for water vapour in the air Two separate regions of condensation are critical At the pointed tip of the spore the hilum closest to the supporting basidium Buller s drop builds up as a large almost spherical water droplet nbsp At the same time condensation occurs in a thin film on the stalk facing part of the spore When these two bodies of water combine the release of surface tension and the sudden change in the center of gravity suddenly expels the basidiospore Remarkably the initial acceleration of the spore is estimated to be about 10 000 g 2 Evolutionary loss of expulsion by force Edit Some basidiomycetes do not have a means to forcibly expel their basidiospores although they still form them In each of these groups spore dispersal occurs through other means of expulsion For example Members of the order Phallales stinkhorns rely on insect vectors for dispersal The dry spores of the Lycoperdales puffballs and Sclerodermataceae earth balls and kin are dispersed when the basidiocarps are disturbed Species of the Nidulariales bird s nest fungi use a splash cup mechanism In these cases the basidiospore typically lacks a hilar appendage and expulsion by force does not occur Each example is thought to represent an independent evolutionary loss of the forcible discharge that comes before all basidiomycetes References Edit Donk M A 1963 A conspectus of the families of Aphyllophorales Persoonia 3 3 214 Money N P 1998 More g s than the Space Shuttle Ballistospore discharge Mycologia 90 4 547 558 doi 10 1080 00275514 1998 12026942 Ingold C T 1998 Ballistosporic basidia The Mycologist 12 2 50 52 doi 10 1016 S0269 915X 98 80040 2 Ingold C T 1991 A view of the active basidium in heterobasidiomycetes Mycological Research 95 5 618 621 doi 10 1016 S0953 7562 09 80076 2 Pringle A Patek S N Fischer M Stolze J Money N P 2005 The captured launch of a ballistospore Mycologia 97 4 866 871 doi 10 1080 15572536 2006 11832777 PMID 16457355 S2CID 218586848 External links EditAmericanMushrooms com How do fungi reproduce APSnet Illustrated Glossary of Plant Pathology Basidum Demonstrating basidiospore discharge by John Webster Mycological Society of America Lab Manual IMA Mycological Glossary Basidum Spore discharge and dispersal in mushrooms by Heino Lepp Australian National Botanic Gardens Using a Microscope Basidia and Cystidia by Michael Kuo MushroomExpert com Retrieved from https en wikipedia org w index php title Basidium amp oldid 1169919537, wikipedia, wiki, book, books, library,
