|Transfer of pollen grains from anther to the stigma of the same flower (typical self-pollination) or another flower of the same plant (adjacent self-pollination)
|Transfer of pollen grains from anther of one flower to the stigma of another flower borne on a different plant.
|Anthers and stigma mature at the same time in a flower.
|Anthers and stigmas mature at different times in a flower.
|Usually, self-pollination doesn’t require any external agent.
|It requires external agents like wind, animals, insects, water etc.
|It gives rise to pure lines after a few generations.
|It cannot give pure lines as it brings about genetic variations.
|Less number of pollen grains are produced as they are not wasted.
|Pollen grains are produced in a huge quantity as most of them are wasted.
|The plants obtained are less resistant to diseases and pests.
|Plants are better adapted and thrive being resistant to diseases and pests.
|Due to lack of variation, it doesn’t contribute towards evolution.
|It plays an important role in evolution because of variation obtained.
|Useful characters are preserved by this method.
|Useful characters are not preserved by this method because of variation.
|Undesirable or defective characters cannot be eliminated by this method.
|Undesirable or defective characters can be eliminated by this method.
|Yield of the plant falls or decreases with time.
|Yield of plant usually increases with time.