ASEXUAL REPRODUCTION

 ASEXUAL REPRODUCTION 

  • Asexual reproduction is the production of offsprings by a single parent without the formation and fusion gametes. It is also called uniparental reproduction or somatogenic reproduction. 
  • The young ones ate genetically and morphologically similar with the parents hence they are called clones.
  • It occurs by mitotic cell division.

TYPE OF ASEXUAL REPRODUCTION 

Asexual reproduction may occur by Fission. Fragmentation, Budding, Regeneration, Spore formation and Vegetative reproduction.

Binary Fission 

Fission

Fission is the division of parental body into two or more parts. If the parental body is divided into two daughter individuals  by mitotic cell division, it is called binary fission. It may be longitudinal binary fission or transverse binary fission, e.g., Amoeba, Euglena, Paramecium, ect. If the parental body is divided into a large number of daughter individuals, it is called multiple fission of Plasmodium is called schizogony. 

Hydra Budding 

Budding 

Budding is a form asexual reproduction in which a new organism is formed from an outgrowth or bud due to mitotic cell division at a particular site. The bud grows attaching to the parent body. Then it detaches from the parent and leads independent life.Budding occurs in yeast, sponges, coelenterates, some flatworms and echinoderm larvae. In Hydra and Sycon, the budding occurs from outer surface of the body (exogenous), in a water fresh sponge, Spongilla, the bud  or gemmule is formed internally (endogenous ) . However, in yest some cells divide asymmetrically resulting a mother cell and a smaller daughter cell by budding.

Fragmentation Asexual Reproduction

Fragmentation 

Fragmentation is a type of asexual reproduction in which the parental body breaks into two or more parts or fragments. Each part grows into an organism, e.g., sponges, hydra, planaria, starfish ect.

Spore Formation 

Spore Formation 

Fungi and algae produce spores. These asexual reproductive  bodies are called zoospores (algae). The spores germinate to form new individuals . Examples of other spores are sporangiospores, chlamydospores, conidia (penicillium), ect.

Gemmae

Gemmae

In the thallus of Marchantia, specialized asexual cups developed called Gemma cup.

Vegetative Reproduction in Plants

Vegetative reproduction is a form of a sexual reproduction where a part of the plant body develops into a new plant. the meristematic tissue undergoes cellular differentiation to form a new plant. monocots have no vascular cambium like dicots, they are difficult to propagate. the vegetative reproductions may be by natural or artificial methods. 

(a) Natural Method 

  1. Stem runner : Runners are stems that grow horizontally above the ground. The birds grow from their nodes to form New plants like mint, cyanodon, oxalis. 
  2. Stem tuber : Stem tuber or potato bears many eyes on nodes. Each aye has one or more buds. New plants are produced from buds. 
  3. Rhizomes : Rhizomes reproduce vegetatively, e.g., Ginger, Banana, Turmeric.
  4. Root : Buds develops from root tubers and grows into a new plant e.g., Sweet potato, Dahlia.
  5. Leaf : Small plants or plantlets develop at the edge of leaves of some plants e.g.,  Bryophyllum.
  6. Offset : Water hyacinth (terror of the Bengal) reproduces asexually by offset.
  7. Bulb : A bulb contains an underground stem. The lateral bud of plant produces a new plant.

(b) Artificial Method

  1. Cuttings : Cuttings are parts of shoot with leaves. New leaves and shoots grow from cuttings. Growth promoters, such as indole acetic acid (IAA), IBA, NAA are used to initiate adventitious roots.
    Cuttings 

  2. Grafting : In grafting, two plants are used to develop a new plant. Share the rooted part of the plant is called stock and part of the plant above ground is called scion. The Sion attached to the stock. It has combined trait of two plants. 
    Grafting 

  3. Layering : Here is shoot of the plant is bent and covered with soil. The tip of the shoot remains free above the ground. When new roots formed, the plant can be separated, e.g., Jasmine.
    Layering 

Tissue Culture : A new plant can be grown in a culture medium from a tissue of desired plant e.g., Dahlia.

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