Question

The different cells of embryo sac are
A. Central cell and antipodal cells
B. Antipodal cells and egg apparatus
C. Central cell and egg apparatus
D. Egg apparatus, central cell and antipodal cell

Answer 1

An embryo sacs are female gametophyte in flowering plants. After maturity, an embryo sac has eight nucleate and seven celled structures. These seven cells are distributed in the embryo sac. The three cells are located at the micropylar end, three cells at the opposite side of the micropylar end that is at the chalazal end and two polar nuclei at the middle of the embryo sac.

Complete answer:
A functional megaspore undergoes mitotic division and forms two-nucleate followed by four-nucleate and finally the eight-nucleate stage of embryo sac without the formation of the cell wall. This mature embryo sac has eight nucleate and seven celled structures. These seven cells are precisely arranged in the embryo sac. The group of three cells are present at the micropylar end. The two cells out of the three cells are located at the synergids and remaining one at the egg cell. The egg cell and synergids together constitute the egg apparatus. The chalazal end is opposite to the micropylar end. The three cells reside at the chalazal end and these are called antipodals. It is at the end of the embryo sac. The remaining two cells are called polar nuclei situated at the middle of the embryo sac, that is the central cell that is situated below the egg apparatus.

Therefore the correct answer is option D, that is, egg apparatus, central cell and antipodal cells are present in the embryo sac.

Note: Generally, an ovule has a single embryo sac. The embryo sac is formed from the functional megaspore. When the megaspore is formed by the megaspore mother cell, this process is called megasporogenesis. The megaspore mother cell undergoes meiosis and forms four daughter megaspores. Out of four, three degenerate and only one is functional megaspore. This functional megaspore undergoes three successive mitosis divisions and forms eight nucleate and seven celled embryo sac.