Transfer of pollen grain from the anther of a flower to stigma is termed as pollination.
Based on the transfer of pollen grains between plants, pollination can be of two types:
- Self Pollination: When pollen of a plant is transferred to the stigma of a flower on the same parent plant then it is termed as self-pollination.
- Cross Pollination: When pollen of a plant is transferred to the stigma of a flower of a plant different from the one from which pollen is obtained then it is termed as cross-pollination.
Some of the most common agents of pollination that helps in carrying the pollen from the anther to the stigma of a flower are insects and wind.
As the pollen of the right type is deposited on to the stigma of the flower of the same species, quite often it leads to germination of pollen grain as a result of a chemical cross-talk between the pollen and the carpel. Germination leads to the growth and extension of the pollen tube through the style of the flower to its ovary. The pollen tube carries the male gametes all the way to the ovule inside the ovary, leading to fertilisation of male gamete with the female gamete inside the ovule,