Question

Which is the most common embryo sac in flowering plants?
A. Monosporic, 8-nucleated and 7 celled
B. Monosporic, 7-nucleated and 7 celled
C. Bisporic, 8-nucleated and 7 celled
D. Bisporic, 7-nucleated and 7 celled

Answer 1

Hint: The embryo sac is the present inside the ovary of the female plant. The cell that develops into the embryo sac is known as the megaspore. This megaspore may be monosporic or bisporic depending on how many nuclei or nucleus took part in the embryo sac development.

Complete answer:
To know the correct answer to the question, we must be well aware of the different types of embryo sac.
Embryo sac is the female gametophyte in angiosperms or flowering plants. On basis of its development it may be divided into:
Monosporic embryo sac- Megaspore mother cell divides through reduction division. When one of the four nuclei of the megaspore helps in the development of the embryo sac then the embryo sac is known as monosporic embryo sac.
Bisporic embryo sac- In this type of embryo sac, two nuclei take part in the development of the embryo sac.
Tetrasporic embryo sac- In this type of embryo sac, four nuclei take part in the development of the embryo sac.
The monosporic embryo which is 8-nucleated and 7-celled is the most common type of embryo present in most of the flowering plants.

Hence, the correct answer to this question is option a.

Note: Here it must be noted that this type of embryo sac contains an egg apparatus which has 2 synergids and 1 egg cell, 3 antipodal cells which are present at the chalazal end while one central cell. All these sum up to a total of 7 cells.
All these cells except the central cell contain 1 nucleus each. Only the central cell has 2 polar nuclei in the centre, hence the total number of nuclei adds up to 8.