REPRODUCTION AND ITS TYPES

The process through which individuals of the same kind are produced is called as reproduction. There are three types of reproduction:

A) Vegetative reproduction: Involves raising of plant using portion or fragment of plant body (Vegetative parts) e.g. Potato tuber, leaf of Bryophyllum, etc.

B) Asexual reproduction: No gametogenesis and syngamy is seen. Spores are produced.

          It is uniparental process. E.g. Mucor, Rhizopus etc.

C) Sexual reproduction: The process which involves formation (gametogenesis) and fusion of gametes (syngamy) is called as sexual reproduction.

          The process is biparental.  E.g. Jowar, Cotton etc.

 

SIGNIFICANCE OF VEGETATIVE OR ASEXUAL METHODS OF REPRODUCTION

 

a.     Homozygous nature i.e. purity of characters can be maintained.

b.   Rapid method of propagation or multiplication.

c.    Easy and cheap method of reproduction.

d.   Useful for plants which do not produce seeds or viable seeds.

       Disease resistance can be introduced.

       Flowers and fruits of superior quality can be developed.

      Combining of characters of two different plants is possible.

 

METHODS OF ASEXUAL REPRODUCTION IN LOWER ORGANISMS

 

A) Budding :- Unequal division, two unequal cells are produced. Small cell remains attached to parental cell, at maturity detaches and behaves as independent organism. e.g. Yeast.

B) Fragmentation :- Commonly found in filamentous algae and in fungal hyphae. Breaking of parent body into two or more fragments each of which develops into a new organism. E.g. Spirogyra

C) Sporulation:- Refers to spore formation, single celled thin walled, minute and serve as propagules. Algal spores are generally motile in nature called as zoospores. Flagella serve as locomotory organs. Dispersed through water.

          Conidiospores are non motile spores produced by fungi either singly or in chains. Their dispersal is generally with the help of wind.

                                

 

 

ARTIFICIAL METHODS OR HORTICULTURAL METHODS FOR

VEGETATIVE PROPAGATION

 

     1.  The Artificial methods are quick and give good results.

     2.  The different useful characters in different plants or varieties can be combined in single variety.

     3.  It is possible to develop population of genetically identical plants called as clone.

     A) Cutting:

          The method of vegetative propagation in which cut piece of any vegetative organ is used to produce new plant under favourable conditions is called as cutting.

          The small piece of any plant organ i.e. stem, root or leaf having active buds is used for propagation. Generally, stem cuttings are used for vegetative propagation. The stem cuttings are placed under soil in natural conditions (lower nodes of cutting are placed below soil surface and upper nodes are kept above soil surface)

          These lower nodes (below soil surface) give rise to adventitious roots and buds on upper nodes produce new shoot. For quick formation of roots different growth hormones can be applied. (IAA, NAA, etc.) Spring is the favourable season for cutting. The different plants which are generally propagated through cutting are as follows:

     ix) Advantages :-Large number of plants can be produced from a single plant in small space. Genetically identical plants can be developed. It is used mainly for development of ornamental plants, economically important plants. It is simple, common, cheap and successful method.

 

B) Grafting: It is an art of joining the parts of two different plants which are closely related and belong to same species to obtain desirable plant.It brings about organic union or fusion of tissues.It is practiced between two closely related dicotyledonous plants having active vascular cambium. The plant of which root system is taken is called as ‘stock’ and the other part of which shoot system is taken is called as ‘scion’. Within few days stock and scion become the composite plant and at the junction of these two parts a parenchymatous cells i.e. callus is produced. Grafting is not possible in monocot plants.

          The different types of grafting are as follows:

          a)  Tongue grafting:  In this type, the diameters of stock and scion are same. Both stock and scion are cut obliquely at same angle and notches are provided for close fitting. Scion is inserted into stock so that cambial region of both the plants will be in maximum contact. The two plants are coated with wax at exposed surface.

          Ex: - Citrus, rose, apple, mango etc. It is also called as whip grafting.

          (b) Wedge Grafting:In this method, stock and scion are almost same in diameter but the stock shows slightly more diameter. The V-shaped notch is given in the stock and a wedge – shaped or solid V-shaped cut is given to the scion.    The scion is inserted into the stock tight and finally wax is applied.  For Example – Apple.

          (c) Crown Grafting. In crown grafting, the diameter of the stock is larger than scion. The scion are cut into wedges.Many scions can be inserted into the cuts of stock and grafting and wax is applied.For example – Citrus

          X) Advantages:-It is used for the plants which could not propagate by any other method.Disease free or resistant plants can be developed. Poorly growing species can be developed by using stock with vigorous growth. It helps to develop useful characters in economically important plants.Grafting can be used to develop plant with desirable characters.

 

(c) Budding:                      

     In this method scion shows vegetative bud along with small portion of bark having intact cambium. The bud or scion is inserted into the slit developed in the stock. The stock and the scion are tied firmly but the bud portion is allowed to remain exposed. The method is generally practiced in rainy season. Budding is mostly applied in plants like rose, apple etc.

DISADVANTAGES OF VEGETATIVE PROPAGATION

     Plants do not show variations. Dispersal of the propagules from one place to another place is not possible which may result in overcrowding. New characters cannot be introduced. Diseased parent plant may transfer disease into newly developed plant.

Vegetative organs cannot be stored for long duration.

can you tell?

Why grafting is not possible in monocot plants.