explain the formation of mature embryo from embry sac?

The development of an embryo from a zygote is called embryogeny. The development takes place at the micropylar end of the embryo sac. Most of the zygotes divide only after a certain amount of endosperm is formed. This provides assured nourishment to the developing embryo.

Development of Embryo in Dicots:

• The zygote divides into two unequal cells, larger suspensor cell towards the micropyle and a smaller embryonal cell towards the antipodal region.
• The suspensor cell undergoes transverse division to form 6-10 celled suspensor.
• The suspensor cell towards the micropylar end is large and is called haustorium or vesicular cell.
• The suspensor cell towards the embryonal cell is called hypophysis which forms the radicle tip.
• The embryonal cell divides twice vertically and once transversely to produce a two-tiered eight-celled embryo.
• The epibasal tier forms two cotyledons and a plumule while the hypobasal tier produces only hypocotyl and most of the radicle.
• The octant embryo undergoes periclinal divisions to produce protoderm, procambium and ground meristem.
• Protoderm forms epidermis, procambium forms stele and ground meristem produces cortex and pith.
• Initially, the embryo is globular and undifferentiated and is called proembryo.
• It is then transformed into embryo with the development of radicle, plumule and cotyledons.