1. Incompatibility: Failure of germination of pollen on the stigma of same plant or failure of fusion between the functional male gamete with the mature and functional egg is called as incompatibility or self sterility. This may be physiological or morphological and is considered as an adaptation to eliminate self-pollination and promote crosspollination
2. Development of seed: After successful fertilization, the ovule is transformed into seed by several morphological and physiological changes. After a successful act of fertilization and double fertilization, each ovule is transformed into the seed. The parts of ovule undergo morphological changes as follows:
- Funicle – Stalk of seed
- Micropyle – Gets sealed
- Nucellus – Degenerates in most cases.
- Integuments – Seed coat, (outer integument-Testa and inner integument-Tegmen).
- Fertilized egg – Embryo
- rimary endosperm nucleus – Endosperm (Present in albuminous seeds and not in exalbuminous seeds).
- Antipodals and synergids – Degenerate.
3. Development of fruit: The stimulus of pollination and fertilization induces several changes in the ovary and it is transformed into fruit. The ovary wall forms the fruit wall called pericarp and it encloses the seeds formed by the transformation of ovules.
4. Alternation of generation: In all sexually reproducing plants, there are two phases or generations in the life cycle. These two generations are haploid gametophytic (n) and diploid sporophytic (2n) phase and the two occur alternately. “This is called alternation of a generation”. In angiosperms, the prominent phase is diploid sporophyte, differentiated into root, stem and leaves. It gives rise to haploid phase by meiotic division of microspore mother cells and megaspore mother cells. The gametophytic phase produces male gametes and egg cell which by syngamy bring the diploid phase into existence. Here the gametophytic phase is short-lived and is completely dependent on the diploid sporophytic phase.
