Pollination and its types by AGRI Grovestudies

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Pollination 

The process by which pollen grains are transferred from anther to stigma is reffered to the pollination.

Pollination is two types –

1.     Autogamy or Self pollination

2.     Allogamy or Cross pollination

Autogamy – transfer of pollen grains from the stigma of same flower is known as autogamy or self pollination.

Autogamy is closed from of breeding.

Such species develop homozygous balance and do not exhibit significant inbreeding depression.

Mechanism promotes self – pollination /-

1.    Bisexually –

Presence of male and female organs in the same flower is known as

Bisexually. The presence of bisexual flowers is a must for self pollination. All the self pollinated plants have hermaphrodite flowers.

2.    Homogamy –

Maturation of anthers and stigma of a flower at the same time is called homogamy. As a rule, homogamy is essential for self- pollination.

3.    Cleistogamy –  When pollination and fertilization occur n unopened flower bud, it is known as cleistogamy. It ensures self pollination and prevents cross pollination. Cleistogmay has been reported in some varieties of wheat, barley, oats and several other grass species.

4.    Chasmogamy :-  Opening of flowers only after the completion of pollination is known as chasmogamy.

This also promotes self pollination and found in crops like wheat m barley , rice and oats.

5.    Position of Anthers /- In some species, stigma are surrounded by anthers in such a way that self pollination is ensured. Such situation found in omato and brinjal.

In some legumes, the stamens and stigma are enclosed by the such a way that self pollination is ensured. Examples are greengram, blackgram, soyabean, chickpea, and pea.

 

 

Allogamy or Cross Pollination ;-

          Transfer of pollen grains from the anther of one plant to the stigma of the another plant is called Allogamy or cross pollination.

This is the common from of the breeding. Allogamy leads to the heterozygosity. Such species develop heterozygous balance and exhibit significant inbreeding depression on selfing.

 

Mechanism of Promoting Cross – pollination –

1.    Dicliny – It refers to unisexual flowers. This is two types

a.     Monoecy – when male and female flowers are separate but present in the same plant. It is known as monoecy. In some crops, the male and flower are present the same infloresence such as in mango, castor and banana.

b.    Dioecy – When staminate and pistillate flowers are present on different plants, it is called dioecy. It include, papaya, date , palm, spinach and asparagus.

 

2.    Dichogamy – (greek word dikho- apart and gamous – marriage)

It refers to  maturation of anthers and stigma of the same flowers at different times, dichogamy promotes cross pollination even in the hermaphrodite species.

Dichogamy is of two types

a.     Protogyny :- when pistil matures before anthers, it is called protogyny such as in pearl millet.   

b.    Protandry ;- When anthers matures before pistil, it is known as protandry. It is found in maize, sugarbeet and several species.

 

3.    Heterostyly ;-

When styles and filaents in a flower are of different lengths, it is called heterostyly. It promotes cross pollination, such as linseed.

4.    Herkogamy ;-

Hinderance to self- pollination due to some physical barriers such as presence of hyline memebrane around the anther is known as herkogmay.

Such member does not allow the dehiscence of pollen and prevents self- pollination such as alfalfa.

 5. Self incompatibility

The inability of fertile pollens to fertilize the same flower is referred to as self

incompatibility. It prevents self-pollination and promotes cross pollination. Self incompatibility

is found in several crop species like Brassica, Radish, Nicotiana, and many grass species. It is of

two types sporophytic and gametophytic.

6. Male sterility

In some species, the pollen grains are non functional. Such condition is known as male

sterility. It prevents self-pollination and promotes cross pollination. It is of three types: viz.

genetic, cytoplasmic and cytoplasmic genetic. 

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