Asexual Reproduction:- Biology

 12th Biology 

1.1 Asexual Reproduction:

i. Fragmentation: Multicellular organisms can break into fragments due to one or the other reasons. e.g. Spirogyra. These fragments grow into new individuals.

Fig. 1.1: Budding in Yeast

ii. Budding: It is the most common method of asexual reproduction in unicellular Protosiphon and yeast. Usually it takes place during favourable conditions by producing one or more outgrowths (buds). These buds on separation develop into new individual.

iii. Spore formation: In Chlamydomonas asexual reproduction occurs by flagellated, motile zoospores which can grow independently into new individuals.

Vegetative Reproduction:

Plants reproduce asexually through their vegetative parts. Hence, the new plants formed are genetically identical to their parents.

There are also few methods which would not occur naturally in the plants. Agriculture and horticulture exploit vegetative reproduction in order to multiply fresh stocks of plants. Artificial methods are used to propagate desired varieties according to human requirements. The various methods are as follows:

a. Cutting:

The small piece of any vegetative part of a plant having one or more buds is used for propagation viz. Stem cutting - e.g. Rose, Bougainvillea, leaf cutting e.g. Sansvieria ; root cutting e.g. Blackberry.

b. Grafting:

Here parts of two plants are joined in such a way that they grow as one plant. In this method, part of the stem containing more than one bud (Scion) is joined onto a rooted plant called stock, is called grafting. Whereas budding is also called bud grafting in which only one bud is joined on the stock, e.g. Apple, Pear, Rose, etc.

c. Tissue culture : It is a method by which a small amount of plant tissue iscarefully grown to give many plantlets. Micropropagation method is also used now a days.