Observe the given diagram and answer the questions given below:

Identify the correct statements with respect to the female gametophyte.

A. Three cells at the chalazal end group together to form an egg apparatus.

B. Female gametophyte is also known as embryo sac.

C. Six of the eight nuclei in the embryo sac are surrounded by cell walls and organized into cells.

D. Megaspore mother cells form four megaspores by meiotic division

Choose the correct answer from the options given below:

B, C and D only

The correct answer is Option (3) – B, C and D only

In flowering plants, the megaspore mother cell undergoes meiosis and forms four megaspores. However, only one of these megaspores is functional and develops into the female gametophyte. The other three megaspores degenerate.

Embryo sac is the female gametophyte, which is formed from a single functional megaspore and contains the egg cell and other cells necessary for fertilization and embryonic development.

The nucleus of the functional megaspore divides mitotically to form two nuclei which move to the opposite poles, forming the 2- nucleate embryo sac. Two more sequential mitotic nuclear divisions result in the formation of the 4-nucleate and later the 8-nucleate stages of the embryo sac. It is of interest to note that these mitotic divisions are strictly free nuclear, that is, nuclear divisions are not followed immediately by cell wall formation. After the 8-nucleate stage, cell walls are laid down leading to the organisation of the typical female gametophyte or embryo sac. Observe the distribution of cells inside the embryo sac.

Six of the eight nuclei are surrounded by cell walls and organised into cells; the remaining two nuclei, called polar nuclei are situated below the egg apparatus in the large central cell.

There is a characteristic distribution of the cells within the embryo sac. Three cells are grouped together at the micropylar end and constitute the egg apparatus. The egg apparatus, in turn, consists of two synergids and one egg cell. The synergids have special cellular thickenings at the micropylar tip called filiform apparatus, which play an important role in guiding the pollen tubes into the synergid.

Three cells are at the chalazal end and are called the antipodals. The large central cell, as mentioned earlier, has two polar nuclei. Thus, a typical angiosperm embryo sac, at maturity, though 8-nucleate is 7-celled.