Types of Pollination
Self Pollination (Autogamy) and Cross Pollination (Allogamy)
Self Pollination or Autogamy (auto = self, gamos = marriage):
Transfer of pollen grains from anther to the stigma of same flower or a different flower produced on the same plant, is called self pollination.
Self pollination may occur by three ways.
Autogamy: It is the transfer of pollen grains from anther to the stigma of same lower. It occurs in bisexual flowers only. e.g. Pea.
Geitonogamy - (Geiton - neighbour, gamos = marriage) It is the transfer of pollen grains from anther to the stigma of another flower produced on the same plant, e.g. Cucurbits.
Autogamy (auto = self, gamos = marriage):
When the pollen grains are transferred from anther of a lower produced on one plant to the stigma of another lower produced on another plant having similar genetic make-up, then this is also considered as self pollination. This is possible in plants showing vegetative reproduction.
Advantages of Self-pollination
Self pollination is nearly a sure method because least chances of failure are there, as no extenal agents are involved.
Self pollination is most economic metnod for the plant because modification like large and attractive lowers, fragrance and nectar production is not required.
Least wastage of pollen grains is there. Improved varieties of plants can be multiplied by preserving their desired characters.
Genetic stability (pure lines) can be maintained in the progeny.
Self Pollination has disadvantages as:
There is no chance of forming improved varieties like hybrids.
Undesirable characters can neither be eliminated nor can the desirable characters be introduced in the offspring.
Self pollination, if occurs continuously for many generaions then the progeny becomes weaker and susceptible to diseases. Continued self pollinaion may result in the formation of less number of seeds per fruit, less viability of seeds, less adaptability to climatic variaions, etc. It doesn't favour the variations and evolution process.
Cross Pollination or Allogamy
Cross Pollination or Allogamy (allos = different, gamos = mariage)
It is the transfer of uotlen grains from anther of a flower to the stigma of another flower produced on a different plant having dissimilar genetic makeup.
There are two types of cross pollination; Xenogamy and Hybridization.
Xenogamy: The transfer of pollen grains from anther of a flower to the stigma of another flower produced on a different plant belonging to the same species is called Xenogamy. E.g. Papaya
Hybridization: The transfer of pollen grains from anther of a flower to the stigma of another flower produced on a different plant belonging to a different variety / subspecies /species is called hybridization. For e.g. pollination between two species/varieties of cotton.
Advantages:
Cross pollination involves genetic recombination and brings variations.
The undesirable characters can be eliminated and the desirable characters can be introduced in the offspring.
Improved varieties like hybrids can be produced by hybidization methods.
The offspring formed are strong, disease resistant and better adapted to climatic variaions.
The offspring show better vigour (hybrid vigour) and vitality. It favours the process of evolution.
Disadvantages:
It has disadvantages as it depends on the external carriers; therefore, failure chances are more (not sure).
It is not an economical method because a lot of plant energy is wasted for attraction of cariers.
There is wastage of pollen grains. Due to geneic recombination, some desirable characters can get eliminated and undesirable ones may get introduced in the offspring.
Genetic purity is not maintained in the offspring.
