Question

Explain the development of the zygote into an embryo and of the primary endosperm nucleus into endosperm in a fertilized embryo sac of a dicot plant.

Answer 1

The development of embryo is endoscopic .the zygote divides into two un equal cells a larger suspensor cell towards micropyle and a smaller embryonal cell ( or terminal cell) towards the antipodal region .the suspensor cell undergoes transverse divisions forming 6 to 10 celled long suspensor .the first cell of the suspensor is known as hypophysis . it forms the radicle tip.
The embryonal cell divides twice vertically and once transversaly to produce a two tiered eight celled embryo. the epibasal tier forms two cotylendons and a plumule while the hypobasaltier produces only hypocotyl and most of the radicle for this the octant embryo undergoes periclinal divisions producing proderm procambiam and ground meristem .it is intially globular but with the growth of cotylendons .it becomes heart shaped and then assumes the typical shape.

Answer 2

The fertilization takes place through endosperm.

Zygote now divides by mitosis and results in pro embryo.

Now globular embryo is formed which later results into a mature one.

It will look like a horse shoe shape.

In dicot there are two cotyledons and an axis.

The part above the axis ends at the plumule.

The below one is attached to the radicle.