After fertilisation many changes takes place in the embryo sac ovule, ovary and flower. These changes are called post fertilisation changes. The sepals, petals, stamens, styles and stigmas fall off. Ovary stores food materials and develops into a fruit. The fertilized ovules develop into seeds. The various changes that occur in the ovule are as follows :
`{:("The parts of ovule and embryo sac",,"Changes occurring after fertilization"),("1. Funiculus",-,"Stalk of the seed"),("2. Outer integument",-,"Testa (outer seed coat)"),("3. Inner integument",-,"Tegmen (inner seed coat)"),("4. Micropyle",-,"Seed pore"),("5. Zygote",-,"Embryo"),("6. Synergids",-,"Degenerate"),("7. Antipodals",-,"Degenerate"),("8. Primary endosperm nucleus",-,"Endosperm"),("9. Hilum",-,"Scar of the seed"):}`
Endosperm : In majority of angiosperms, endosperm is triploid and formed after fertilisation. In gymnosperms, endosperm is haploid and formed from female gametophyte before fertilisation.
In certain plants, the developing embryo utilises the endosperm completely. The seed contains only embryo. Endosperm is absent. Such seeds are called the non-endospermic seeds or ex-albuminous seeds. E.g. : Dolichos, Cicer, capsella etc.
In certain plants the developing embryo utilises the endosperm partially and the seed contains some amount of endosperm. Such seeds are called the endospermic seeds at albuminous seeds.
E.g. : Ricinus, Datura, Cocos etc.
In members of Orchidaceae endosperm is not formed (Podestamaceae).
Perisperm : As the embryo and endosperm are developing in the embryo sac, this embryosac grows by absorbing the nutrients from the nucellus. Hence Nucellus gets depleted when the seed reaches maturity. But in some seeds, some amount of nucellus is left out called perisperm. E.g. : seeds of Piperaceae, Nymphaeaceae, Coffee seeds etc.
