Embryogeny in Monocots and Dicots MCQ - Practice Questions with Answers

• The embryo develops at the micropylar end of the embryo sac where the zygote is situated.
• Most zygotes divide only after a certain amount of endosperm is formed. 
• This is an adaptation to provide assured nutrition to the developing embryo. 
• Though the seeds differ greatly, the early stages of embryo development (embryogeny) are similar in both monocotyledons and dicotyledons.

Embryogeny in Dicots:

• In a typical dicot, the zygote elongates and then divides by a transverse wall into two unequal cells.
• The larger basal cell is called the suspensor cell. 
• The other towards the antipodal end is termed as the terminal cell.
• The suspensor cell divides transversely a few times to produce a filamentous suspensor of 6-10 cells. 
• The suspensor helps in pushing the embryo in the endosperm.
• The first cell of the suspensor towards the micropylar end becomes swollen and functions as a haustorium. 
• The haustorium has wall ingrowths similar to transfer cells.
• The last cell of the suspensor at the end adjacent to the embryo is known as hypophysis.
• Hypophysis later gives rise to the radicle and root cap.
• The embryo cell undergoes two vertical divisions (quadrant stage) and one transverse division to form eight cells arranged in two tiers (octant stage) epibasal (terminal) and hypobasal (near the suspensor). 
• The epibasal cells eventually form the two cotyledons and the plumule. 
• The hypobasal cells produce the hypocotyl except for its tip.
• Initially, the embryo is globular and undifferentiated. 
• Early embryo with radial symmetry is called proembryo. 
• It is transformed into an embryo with the development of the radicle, plumule and cotyledons.
• Two cotyledons differentiate from the sides with a faint plumule in the centre. At this time the embryo becomes heart-shaped. 
• The rate of growth of the cotyledons is very high so that they elongate tremendously while the plumule remains as a small mound of undifferentiated tissue.