Give me some general characters of the class BASIDIOMYCETES,, in more than 100 words,, with an example
Answers
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Some General Characters of the Class Basidiomycetes
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(1).The Basidiomycetes comprise the highest group of fungi which are often noticed conspicuously occurring in fields and forest areas.
(2).The fungi commonly known as mushrooms, toadstools, puff-balls, and bracket fungi are the Basidiomycetes.
(3).Many used as food are cultivated in a large-scale for marketing
(4).The fungi of this group are characterized by the production of spores known as basidiospores resulting from karyogamy and meiosis, and are borne externally on slender protuberances, the sterigmata (sing, sterigma).
Ex. Mushrooms .
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Basidiomycetes
(i) Thallus is usually mycelial (some are yeasts called basidiomycetous yeasts). Hyphae are septate. In some cases, a number of hyphae lying parallel to one another are joined together to form thick strands enveloped in a sheath or cortex and behave as a unit or tissue. This modified hyphal form is called rhizomorph.
(ii) The mycelium of most of the Basidiomycetes passes through three distinct stages of development, which are called primary mycelium (monokaryotic and develops from the germination of sexual spore called basidiospore), secondary mycelium (dikaryotic and develops from primary mycelium after the process of plasmogamy during sexual reproduction), and tertiary mycelium (represented by well-matured secondary mycelia that compose the fruiting bodies called basidiomata of complex Basidiomycetes).
(iii) Septa in hyphae are simple or characteristic dolipore. The dolipore septum flares sharply and broadly in the middle portion forming a barrel-shaped structure with open ends, which is covered by membranous structure called paranthesome or septal pore cap.
(iv) Cell wall is made up of chitin and glucans.
(v) In all the Basidiomycetes, except the rusts, a specialized structure called clamp-connection is formed on the secondary mycelium. Clamp-connection is a device for the perpetuation of dikaryophase in the secondary mycelia in Basidiomycetes.
(vi) The asexual reproduction takes place by oidia, conidia, or chlamydospore formation. Out of the several types of spores developed in the life cycle of rusts and smuts, some function as asexual spores. The higher taxa of this class lack asexual reproduction.
(vii) No specialized sex organs develop in Basidiomycetes and sexual reproduction takes place by conjugation of nuclei of two different strains.
(viii) During sexual reproduction, the dikaryotic cell is formed by spermatization, somatogamy, clamp- connection, or Buller phenomenon.
(ix) Karyogamy does not occur just after plasmogamy because there exists a prolonged dikaryophase between plasmogamy and karyogamy. The fusion of nuclei of two different strains occurs within the basidial mother cell.
(x) Meiosis takes place just after karyogamy resulting in haploid daughter nuclei that are used in the formation of basidiospores.
(xi) Basidiospores are the characteristic haploid sexual spores of basidiomycetous fungi, which are produced exogenously on the surface of basidia after karyogamy and meiosis within nuclei lying inside basidia. If the sexual spore of a fungus is a basidiospore, the fungus is a Basidiomycete regardless of any other character. This one character distinguishes Basidiomycetes from all other fungi.
(xii) Except rusts and smuts, the Basidiomycetes usually produce fruiting bodies called basidiomata , which were earlier called basidiocarps.
→ Example - mushrooms, puffballs, stinkhorns, rusts, and smuts.