Thursday, September 3, 2009

Asexual Reproduction of Fungi

Fungi as like other kind of plants have two kind of reproduction; asexual reproduction and sexual reproduction.

Asexual reproduction
  1. Binary Fission of Fungi
    In its simplest form asexual reproduction is by budding or binary fission. The onset of the cellular events is accompanied by the nuclear events of mitosis.
    The first step of cell fission can be seen as the development of a ring by chitin around the point where the bud is about to appear. This reinforces and stabilizes the cell wall. Enzymatic activity and turgor pressure the act to weaken and extrude the cell wall. New cell wall material is incorporated during this phase. Cell contents are forced into the progeny cell, and as the final phase of mitosis ends a cell plate, the point at which a new cell wall will grow inwards from, forms.
    Fission of Fungi Cell:
    Separation of the bud from the parent leaves a scar. When chains of yeast cells do not fully separated this can create a pseudo-mycelium.
  2. Fragmentation
    The other kind of asexual reproduction is by fragmentation. Many fungi can reproduce by fragmentation. Any mycelium that is fragmented or disrupted, provided that the fragment contains the equivalent of the peripheral growth zone, can grow into a new colony. Many fungi are sub-cultured using this hyphal fragment technique. All of this weeks practical plates have been inoculated in this way with a cork bore taken from a colonized donor plate. Cut mycelial tips do not regenerate, but branches can form some distance from the damage point. This method of fungi reproduction often use by fungi seed producer to create a pure fungi seed.
  3. Spore Formation
    The most important type of asexual reproduction is that of spore formation. Asexual reproduction is extremely important to fungi. It is responsible for the production of large numbers of spores throughout the year. These asexual spores are formed on a phase of the fungal life cycle termed in some texts as the mitosporic, or anamorphic phase. There can be more than one mitosporic state for each species of fungus, and in some cases the mitosporic state of very different species can look very similar. This has contributed to the problems of creating taxonomy for the fungi that only possess mitosporic states. The sexual stage of the fungus can be termed the teleomorph, and the characteristics of this phase of the life cycle are much more stable and reliable for taxonomy purposes.

    The onset of asexual reproduction is controlled by many different things. Some are environmental, like nutrient levels, CO2 levels, and light levels. Others can fungi have internal time clocks and sporulate anyway in a preset part of the fungal life cycle designed to spread and maximize colonization during one season.

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