Three cells grouped together at the micropylar end and constitute _____________ in the embryo sac.

Egg apparatus

The correct answer is Option (3) –Egg apparatus

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.

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, has two polar nuclei. Thus, a typical angiosperm embryo sac, at maturity, though 8-nucleate is 7-celled.

                                            Embryo Sac