Question

Explain embryo development in angiosperms.

Answer 1

The development of embryo in angiosperms involves the following steps:

1. Embryo develops from the diploid zygote.
2. The diploid zygote divides and redivides by mitosis to form a group of diploid cells called embryo.
3. Initially, the zygote undergoes a transverse division to form a two-celled proembryo consisting of an upper central terminal cell and a lower basal cell.
4. The central terminal cell lies towards the micropylar end, while the basal cell lies towards the centre.
5. The basal cell undergoes repeated divisions to form a multicellular structure called suspensor.
6. The suspensor pushes the embryo towards the endosperm and thereby provides nourishment to the developing embryo.
7. The upper terminal cell divides repeatedly to form the embryo proper.
8. The fully developed embryo consists of radicle, plumule and one or two cotyledons.
9. The embryo having two cotyledons is called dicot embryo.
10. The embryo with only cotyledon (scutellum) is called monocot embryo.
11. In monocot embryo, radicle is covered by protective covering called as coleorhiza and plumule is covered by coleoptile.