ANSWERS: 3
  • Fungi reproduce both asexually and sexually. In some fungi, during the formation of reproductive structures (asexual or sexual) the entire thallus is used up. such a case is common in lower fungi and they are called Holocarpic. In higher fungi however only a portion of the thallus produces reproductive structures so that vegetative and reproductive phases can occur together. These fungi are called Eucarpic. Holocarpic nature is considered primitive. ASEXUAL REPRODUCTION : - Asexual reproduction is a frequent occurence in fungi than sexual and it is that which accounts for the rapid distribution of fungi. Asexual reproduction takes place by a variety of methods. They are : - (1) Fragmentation (2) Fission (3) Budding (4) Spore formation (1) Fragmentation : This is of two types: (a) Accidental : The mycelium accidentally breaks up into several fragments each one will develop into a new individual. (b) Purposive : Fragmentation of the mycelium takes place as a normal means of propagation. The hypha breaks up into individual cells. Each such isolated cells called Oidium or Arthospore develops into a new individual. (2) Fission : It is the simple splitting of the cell into two daughter cells. (3) Budding : The production of a new cell by the outgrowth (bud) of a cell is called budding. As the bud is being formed, the nucleus of the parental cell divides with one of the daughter nuclei entering the bud. The bud eventually breaks from the parent cell and develops into a new individual. (4) Spore Formation : By far, the commonest method of asexual reproduction is by spore formation. Spores are formed internally or externally by the hypha. When the spores mature they get dispersed by wind or water and germinate to give rise to a new individual. SEXUAL REPRODUCTION : - Sexual reproduction in fungi is of five types. They are : - (1) Planogametic Copulation (2) Gametangial Contact (3) Gametangial Copulation (4) Spermatization (5) Somatogamy (1) Planogametic Copulation : This type is mostly seen in some aquatic fungi belonging to lower phycomycetes. This involves the fusion of two motile gametes (planogametes). The gametes may be isogametes or anisogametes. In this case the fusion is outside the gametangia. (2) Gametangial Contact : In this method, the two sex organs come in contact. Usually to effect the contact, a conjugation tube or fertilization tube is formed from the antheridium which penetrates the oogonium. This forms a passage for the migration of male nuclei into the oogonium. (3) Gametangial Copulation : In this method, the entire contents of the contacting gametangia fuse. The walls between the two dissolve and the antheridial contents flow into the oogonium. (4) Spermatization : In some higher fungi, special erect branches of the hyphae (spermatiophore) are produced which cut off uninucleate male reproductive cells called spermatia. The spermatia are carried by wind or insects to the female reproductive structure - the receptive hypha, the basal cell of which is fertile. The spermatium settles at the tip of the receptive hypha. The walls in between the two dissolve and the spermatial nucleus migrates into the receptive hypha. (5) Somatogamy : This is the most advanced type of reproduction in fungi. In this type no sex organs are formed. At the time of reproduction, two vegetative hyphae of compatible mycelia fuse. This is met with in higher ascomycetes and higher basidiomycetes.
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