Transfer of pollen grain from anther to the stigma of same or different flower.
It is of two types:
1.Self pollination
2. Cross pollination
Self pollination is of two types:
(a) Autogamy : When the pollen transfer to the stigma of same flower. It is of three types:
1. Cleistogamy : In closed flower pollen transfer to the stigma of same flower this is known as cleistogamy. Ex. Oxalis
2. Homogamy : Anther and stigma of a flower mature at same time and they brought together by growth or folding to ensure self pollination. Ex. Sunflower
3. Bud pollination: Anther and stigma of flower mature before bud opening to ensure self pollination. Ex. Wheat.
(b) Geitonogamy :Pollen from anther of one flower transfer to the stigma of different flower born on the same plant.
Characteristics of flower showing self pollination
1.Flower are bisexual that is androecium and gynoecium on the same flower.
2. They are conspicuous.
3.Do not produce nectar and have no scent.
4.Do not Produce large no. of pollen grain.
5.Maintain purity in race.
DISADVANTAGE : Less chances of production of new varieties.
CROSS POLLINATION:
Transfer of pollen grain from anther of one plant to the stigma of other plant. It is also called xenogamy or allogamy.
Characteristics of flower showing cross pollination:
1.Flower may be unisexual or bisexual.
2.Flowers are large and showy
3.Nectar and scent is present in the flower.
4.Produces large no. of pollen grains.
Advantages:
1.Produces new varieties.
2. Healthy and strong offsprings.Hybride varieties produced
3.High yield and disease resistant varieties are produced Disadvantage: Large no of pollen grains are produced causes wastage
Reasons of cross pollination in some plants:
1.Herkogamy: Mechanical barrier on stigma of some flowers to avoid self pollination .Ex.Calotropis
2.Heterostyly: Stamen and style of some plants are of different lengths so self pollination avoided.Ex.Linum
3.Dichogamy : Androecium and gynoecium of same flower mature at different time. Protandry : When androecium matures first.Ex.Maize Protogyny: When gynoecium matures first.Ex.Aristolochia
4.Male sterility : Pollens of some plants are not functional
5. Dioecism: When flowers are unisexual or dioecious having either gynoecium or androecium Ex Papaya
6. Self incompatibility: When pollen shed on stigma of same flower are fail to bring about self pollination.