Question

What is embryogenesis in plants?

Answer 1

The process occurring from the fertilization of an ovule to the production of a fully developed plant embryo is known as plant embryogenesis. Plant embryogenesis produces immature plants lacking important structures such as leaves, stems, and reproductive structures. The embryo shall develop at the micropylar end of the embryo sac. The seeds of monocot and dicot plants look similar in the early stages of embryogenesis.

Complete answer:
The process of embryogenesis starts with the asymmetrical division of the zygote in a smaller apical cell and a larger basal cell. The apical-basal axial developmental pattern is formed. The apical cell goes on division to form an embryo whereas the basal cell horizontally forms a $6 - 9$ cell filament known as the suspensor cell which provides a connection between the embryo and the endosperm. The cell closest to the basal cell known as hypophysis forms the columella of the root.
The developing embryo goes through four main stages –
a. globular stage – apical cell undergoes several divisions to create an eight celled embryo to a globular shaped embryo then a flat-shaped embryo. The radial pattern is established in this stage and further develops to form the ring layers of stems and the roots. The outermost thick layer of cells forms the epidermis, the next layer forms the ground tissue meristem which develops to form the endodermis and cortex. The central layer of cells called procambium forms vascular tissue and pericycle in the root.
b. heart stage - rapid cell division is seen in each side of the embryo. The center cells of these outgrowths will form shoot apical meristem. The outgrowths will become the cotyledons. The apical region produces shoot apical meristem and cotyledons. The middle region will form the hypocotyls, root, and root meristem. The hypophysis region gives rise to the root meristem.
c. Torpedo stage - Occur due to cell elongation throughout the embryo and the cotyledon will become the shoot apical meristem.
d. maturation stage – embryo folds over within the seeds and the seed starts to lose water to get into a dormant stage.

Note. :
The endosperm produced during the double fertilization provides nutrition to the growing embryo. A typical dicot embryo consists of an embryonal axis and $2$ cotyledons. Embryos of monocot possess only one cotyledon. Cotyledon of the grass family is known as the scutellum, situated towards one side of the embryonal axis.