What do you mean by the development of the embryo?
Development of embryo. 1. The zygote or oospore divides by a transverse wall into an upper suspensor cell and lowers embryonal cell. 2. The suspensor cell which lies towards the micropylar end divides by transverse divisions to constitute 7-10 cells called suspensor. 3. The upper cell of the suspensor filament towards the micropylar end is called a haustorial cell, whereas the cell lying above the embryo cell is called hypophysis. 4. The haustorial cell enlarges in size and attaches the suspensor to the tip of embryo sac. 5. The embryonal cell divides by second longitudinal division at a right angle to the first and then by transverse division to form an octant or eight- celled embryo. 6. Out of these eight cells, the lower four cells of octant away from the suspensor give rise to the plumule and the two cotyledons, while the above four cells of octant near the suspensor from the hypocotyl and stele of the radicle. 7. Then this octant divides by a periclinal division to form outer single-layered dermatogen from which arises the epidermis layer. The inner cells further divide to form periblem below the dermatogen and the central plerome. 8. The periblem forms the cortex while the plerome gives stele of the embryo. 9. The lowermost cell of suspensor, which is lying just above the octant cells is known as hypophysis. The hypophysis divides to give rise to the dermatogen and periblem of the radicle. 10. A fully developed embryo of dicotyledons has an embryonal axis differentiated into plumule, two cotyledons and radicle. 11. In the beginning, the embryo is globular. When two cotyledons differentiate from the sides with faint plumule in the centre, the embryo becomes heart¬shaped. Then the embryo undergoes rest and ovule is transformed into the seed. Monocot embryo: Unlike the dicots where the embryonal mass is formed of eight cells, the anterior cells forming the plumule and the cotyledons, and the posterior forming hypocotyl, the development is much variable in monocots, i.e. grass family. In some cases, suspensor does not develop at all. Only one cotyledon appears in monocots as a terminal structure. The plumule always appears laterally from it.
