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Chapter: Biology: Pollination, Fertilization, And Dispersal of Fruits and seeds

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Pollination: Two types, Significance, Merits, Demerits

Pollination: Two types, Significance, Merits, Demerits
Pollination of two types: 1. self-pollination and 2. cross-pollination.

Pollination:

 

Every fertile stamen contains an anther. Inside the anther develops the pollen grains. At one time the anther bursts and pollen grains are carried and attached to the stigma (of same flower, or flower of the same plant or flower of the same species of a different plant), by insect, air or any other agent. Process by which pollen grains are transferred from anther to the stigma is called pollination.

 

Pollination of two types:

1. self-pollination and

2. cross-pollination.

 

1. Self-pollination: When pollen grains from the anther are transferred to thestigma of the same flower or a flower of the same plant is called self-pollination. In self-pollination the genotype (factors those control the characteristics of living beings) of two flowers remains alike. Self-pollination occurs in a small numbers of plants in nature. Self-pollination takes place in flower like Bean, Tomato, Commelina etc.


2. Cross - Pollination: When pollen grains are transferred from the anther tothe stigma of flowers of same species of a separate plant is called cross-pollination. In cross-pollination the genotypes of two plants have somevariation, in nature, cross-pollination occurs in most of the plants. Examples of cross - pollinated plants are Paddy, Wheat, Maize, Mustard, Silk Cotton (Shimul), Madar, Mango etc.

 

Significance of self-pollination: As this type of pollination takes placebetween two flowers having similar genotype, the genotype of the produced seeds remains unchanged. So the plants that produce from these seeds have got the character just like the mother plant. In this way the hereditary character remains similar i.e. it maintains the purity of species. This is most significant in self-pollination.

 

Merits of Self -pollination:

 

1. Pollination is ascertained.

 2. Very few pollen grains are lost.

3. Maintains the purity of species.

4. Less dependent on external agent.

 

Demerits of self-pollination:

 

1.   No new variety is produced as there is no combinations of new characters.

 

2.   Produce weaker progeny with less vitality.

 

3.   New progeny are borne with less adaptability.

 

4.   The species may extinct in future.

 

Significance of Cross -pollination :

 

Pollination occurs between two flowers having difference in genotype. Thus the seed that is produced from this have variation in genotype. Therefore the new plant grown from this seed is not identical with the mother plant. New variation may produce even a new species. Due to combinations of the most plants their adaptability increase so natural calamity (disaster) cannt extinct them easily.

 

Merits of cross pollination:

 

1.   Combination of new character occurs.

 

2.   New varieties may be originated

 

3.   Seeds become more viable and more tolerant.

 

4.   Adaptability of new plants increases.

 

Demerits of Cross - Pollination:

 

1.        l. Depends on external agent.

 

2.   Pollination is uncertain.

 

3.   There is loss of a large amount of pollen

 

4.   Purity of species is lost/destroyed


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