Introduction to Basidium
Basidia fungi, Basidiomycota, the division of fungus known as the club fungus, includes some of the most well-known fungi. This group includes mushrooms, puffballs, and shelf fungus, as well as plant rusts and smuts. The presence of a club-shaped reproductive structure termed the basidium distinguishes this group, which encompasses roughly 15,000 recognised species. This organ is most likely derived from Ascomycota's ascus, with which it has a number of traits. Both start off as a binucleate, a dikaryotic complex that serves as a karyogamy and meiosis site. The basidium bears its spores outside of the structure, whereas the ascus keeps them inside.
What is Basidium?
Basidium Definition Biology: Upon being asked the basidium definition biology, we can say that A basidium is a small sporangium found on the hymenophore of basidiomycete fungi's fruiting bodies, sometimes known as tertiary mycelium since it develops from secondary mycelium. Tertiary mycelium is a dikaryon of heavily coiled secondary mycelium.
Basidia Definition: Basidia is the plural of Basidium, hence the Basidia definition is the same as above. However, upon being asked the Basidia meaning we can say that they are microscopic, club-shaped, spore-bearing structures that are produced/found in Basidiomycetes.
Basidium Structure
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Although most Basidiomycota have single-celled basidia (holobasidia), few taxa have multicellular basidia (a phragmobasidia). Rust fungus in the order Pucciniales, for example, have four-celled phragmobasidia that are transversely septate, while some jelly fungus in the order Tremellales has cruciate septate four-celled phragmobasidia.
A probasidium, which is a specialised cell that is not elongated like a regular hypha, can sometimes give rise to the basidium (metabasidium). It is possible for the basidium to be stalked or sessile. The basidium is often shaped like a club, with the base of the hemispherical dome at its apex being the widest point, and the base is about half the width of the largest apical diameter.
Development of Basidium
Asexual Reproduction
Basidiomycota proliferates asexually through budding or the generation of asexual spores. Budding happens when a parent cell's outgrowth is divided into a new cell. Any cell in the body has the ability to bud. Asexual spore production, on the other hand, is most commonly found in the extremities of specialised structures known as conidiophores. Terminal cell septae become fully formed, separating a random number of nuclei into separate cells. The cell walls thicken and form a protective layer. The spores that have been protected break off and disperse.
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Sexual Reproduction
A dikaryotic terminal cell of a secondary mycelium hypha develops into a basidium. A septum separates the dikaryotic terminal cell from the rest of the hypha, over which a clamp connection is frequently seen. The terminal cell of the basidium enlarges throughout development to generate young basidium, also known as basidiole.
The basidiole's two nuclei fuse to form a diploid nucleus. Meiosis occurs in the diploid nucleus, resulting in four haploid nuclei. At the apex of the developing basidium, four protuberances appear. Stigmata is the name for these protuberances. Some Basidiomycetes might be lacking these. The tips of the sterigmata grow to generate basidiospore initials when they are present. The four haploid nuclei then squeeze into each basidiospore beginning via sterigmatal transit. The basidiospore initial is then walled off, resulting in a single-nucleus basidiospore.
Heim (1931) named hilum the region of the basidiospore in touch with the sterigma, and hilar appendix or apiculus the small typically pointed protrusion at the hilum at the basal end of the basidiospore.
A tetrasterigmate basidium is one that bears four basidiospores on four sterigmata. On the sterigmata, the basidiospores might be carried symmetrically or asymmetrically. A basidium may only produce two sterigmata and two basidiospores at times. Bisterigmate basidium is the name given to such a basidium.
Each of the two spores may receive two nuclei in this circumstance, resulting in the formation of binucleate basidiospores. The basidiospores of bisterigmatic basidia may also be uninucleate. The remaining two nuclei within the basidium stay unused and eventually disintegrate. It's also possible that there are more than four basidiospores.
Basidia are commonly clavate to broadly clavate and thin. Basidia that range from spherical to elongate are also prevalent. It's possible that they're septate or aseptate. Septation is normally vertical or transverse, though it can also be oblique. The direction of the nuclear spindles during nuclear division can also change between basidia.
Basidia are classified as chiastobasidial when the nuclear spindles are orientated transversely to the basidium. The stichobasidial variety of basidia has nuclear spindles that are aligned longitudinally or obliquely.
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Main Types of Basidia
Homobasidia:
Slender, clavate to widely clavate basidia, or almost globose and aseptate basidia. There may be four or more basidiospores, with or without sterigmata. Autobasidia and holobasidia are other names for them. It's possible that the homobasidia are chiasto- or stichobasidial in nature.
The endobasidia form when the basidia mature inside a fruiting body. Basidia with symmetrical basidiospores on sterigmata are apobasidia, while those with asymmetrical basidiospores are autobasidia.
Heterobasidia:
The basidia are either highly lobed or septate. Phragmobasidia and metabasidia are other names for them.
Neuhoff (1924) named the expanded basal region of the adult basidium in which nuclear fusion occurs as hypobasidium, which bears the epibasidium but not the sterigmata directly in heterobasidia. A heterobasidium, according to Neuhoff, is made up of the hypobasidium and the epibasidium.
Linder (1940) favoured the terms probasidium and basidium for hypobasidium and epibasidium, respectively.
Heterobasidia may again be:
Transversely septate
Longitudinally septate
Deeply lobed
Characteristic of Basidiomycetes
Except for Basidiomycota-yeast, these are filamentous fungi composed entirely of hyphae.
They reproduce sexually by forming basidia, which are club-shaped end cells that normally carry external meiospores (usually four). Basidiospores are the name for these unique spores.
Some Basidiomycota species reproduce asexually.
The majority of Basidiomycetes are saprophytes, meaning they help to decompose litter, wood, and dung.
In nature, basidiomycetes are restricted to only living host plants.
It has a well-developed, branching, and septate mycelium that can be classified as primary, secondary, or tertiary in nature.
Chitin and glucans with 1,3 connected and 1,6 linked B- D glucosyl units make up the cell wall.
Some live in trees as symbionts with mycorrhizae, while others are destructive parasites that destroy a variety of woody and herbaceous plants.
A well-developed, septate, filamentous mycelium makes up the somatic stage, which divides into two stages: Primary mycelium and Secondary or dikaryotic mycelium.
The germination of a basidiospore produces primary mycelium, which has a single haploid (n) nucleus in each cell. There are no sex organs, basidia, or basidiospores visible. It is only temporary.
Chitin and glucans with 1,3 connected and 1,6 linked B- D glucosyl units make up the cell wall.
Some live in trees as symbionts with mycorrhizae, while others are destructive parasites that destroy a variety of woody and herbaceous plants.
A well-developed, septate, filamentous mycelium makes up the somatic stage, which divides into two stages: Primary mycelium and Secondary or dikaryotic mycelium.
The germination of a basidiospore produces primary mycelium, which has a single haploid (n) nucleus in each cell. There are no sex organs, basidia, or basidiospores visible. It is only temporary.
The major food absorption phase is formed by secondary or dikaryotic mycelium, which is made up of cells with two haploid nuclei (n+n). It has a lengthy lifespan and plays an important function in the life cycle.
Secondary or dikaryotic mycelium in the Homobasidiomycetidae can grow for years, producing fructifications every year through the interweaving of hyphae. Basidia and basidiospores are found in the fructifications.
Secondary or dikaryotic mycelium in the Heterobasidiomycetidae produces teleutospores or brand spores, which germinate to become basidia containing basidiospores.
The septal pore in Basidiomycetes is quite complicated (except for rusts and smuts). The parenthesome kind is dolipore.
There are no motile cells in this life cycle.
Clamp connections were formed by the majority of Basidiomycetes.
Dolipore septa are found in the majority of genera.
Asexual reproduction with the generation of spore plays a vital function in the life cycle. Homobasidiomycetidae lacks asexual spores, but Heterobasidiomycetidae creates them in the dikaryotic mycelium. In rusts, the latter creates uredospores and aeciospores.
Sex organs are not found in Basidiomycetes. Plasmogamy and karyogamy are used for sexual reproduction, and karyogamy is followed by meiosis.
Basidium is the major reproductive organ of Basidiomycetes. Both karyogamy and meiosis occur here.
FAQs on Basidium
1. Mention the Significance of Basidiomycetes.
Ans) Several Basidiomycetes cause illnesses in cereals and other economically important plants, causing significant production problems and possibly causing starvation in some regions of the world. Rusts and smuts are major pathogenic Basidiomycetes.
Mushrooms have been a popular cuisine in recent years due to their flavour. Different Mushrooms, such as Agaricus, Pleurotus, and Volvoriella, are now farmed all over the world.
Some mushrooms, such as Amanita spp., are extremely poisonous. Psilocybe spp., for example, produces hallucinogenic chemical compounds.
As parasites, the polypores cause significant damage to forest trees, as well as to lumber like saprophytes.
Basidiomycetous fungi's mycelia are important in the breakdown of organic matter and the recycling of nutrients. It's because they can manufacture a variety of extracellular enzymes that help break down complicated compounds like cellulose and lignin.
2. How are Basidiomycetes and Ascomycetes Similar?
Ans) The fundamental distinction between these two groups is how their minuscule spores are produced. The spores are formed externally in the Basidiomycetes, on the ends of specialised cells called basidia. Spores are produced internally in Ascomycetes, in a sac called an ascus.
