Characteristics of Fungi
(1) Fungi are found everywhere. They are mostly terrestrial, but a few are aquatic.
(2) These are heterotrophic. They live either as saprophytes, parasites or symbionts.
(3) Fungi cells grow as elongated filaments called ‘hyphae’.
(4) The cells of Fungi contains the usual, cell organelles, all similar to eukaryotes, except plastids. Cell wall is usually made up of chitin, some with cellulose and a few have both.
(5) Fungi contain reserve food materials which are in the form of glycogen and oil droplets.
(6) In lower forms of fungi the cytoplasm is continuous. It is called as ‘aseptate’ and ‘coenocytic’. In higher forms of fungi, the mycelium is septate, multicellular with usually one but sometimes more nuclei in each cell.
(7) In many fungi only a part of the mycelium is involved in the development of reproductive organs.
(8) Vegetative propagation by fragmentation and asexually by spores or conidia. Sexual reproduction is isogamous, anisogamous or oogamous or it takes place by gametangial copulation or by somatogam.y
(9) Most fungi form fruit bodies like ascocarps, basidiocarps etc.
(10) There is a gradual progression in fungi in which the interval between plasmogamy and karyogamy increases.
Asexual reproduction takes place in fungi imperfecti Oomycetes, Zygomycetes, Ascomycetes and Basidiomycetes are the major groups of fungi.
Oomycetes : The water mould are said to be the primitive fungi. The asexual reproduction is by biflagellate zoospores produced by sporangia.
In oomycetes the sexual reproduction is by oogamy in which an oospore is formed by fusion of male and female gametes. Oospore undergoes meiosis to give rise to haploid flagellated zoospores again.
Zygomycetes : Rhizopus known as bread mould comes under the group of conjugation fungi. The mycelium has non-septate hyphae. The aerial hyphae bear sporangium that produce numerous haploid spores.
Diploid zygospore formation takes place by sexual reproduction. It is formed by the fusion of + and – hyphae. Zygospore produces haploid spores by meiosis.
Ascomycetes : The sac fungi has number of haploid septate hyphae that bear chains of conidia not enclosed in a sporangium during asexual reproduction.
Fusion process takes place in sexual reproduction leading to formation of an ascus. It produces 4-8 ascospores by meiosis.
Yeast which normally reproduces by budding is a unicellular zygomycetes.
Basidiomycetes : Mushrooms, Puff balls bracket fungi etc. fall in the category of club fungi. The edible mushroom is the fruiting body or basidiocarp. Mycelium grows under the soil. Underside of a cap of a mushroom bears number of basidia which produce haploid basidiospores. The fusion of two strains produces a dikaryon and that forms the fruiting body again.
Fungi are of great economic importance for men.
Lichens are formed by symbiotic association of algae and fungi. Algae photosynthesises the food and fungi provides the attachment, water and mineral nutrients. They are the first organisms that appear in a new terrain.
Mycorrhiza : These are symbiotic associations of fungi with plant roots. The fungus gives the moisture, nitrogen and minerals and the root sugars and vitamins. Plant growth may become stunted in several plants in the absence of mycorrhiza.
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