Question

In an embryo sac, the cells that degenerate after fertilization are.
a. Synergids and primary endosperm cells
b. Synergids and antipodal
c. Antipodal and primary endosperm cells
d. Egg and antipodal

Answer 1

Hint: Mature embryo sac formation takes place in the stigma of female flowers. The stigma contains Megaspore Mother Cell (2n), which goes through one meiotic division to form 2 Megaspores (n) (megaspore dyad) and then 4 Megaspores (n) (megaspore tetrad) from those 2 Megaspores. These Megaspores are arranged vertically.

Complete answer:
In a developed embryo sac there are 7 cells. All these are formed after 2,4,8 nucleate stages. It leads to the formation of the typical female gametophyte or embryo sac Synergids and antipodals degenerates after fertilization. So, option B is correct.

The three cells arranged together at the micropylar end. Thus, it constitutes the egg apparatus. The egg apparatus in turn consist of 2 synergids and one egg cell.

The other three cells are at the chalazal end. These three cells are called the antipodal.
And the remaining 2 cells are called polar nuclei located at the center. The two cells fuse to form a polar nucleus.

Thus, a typical angiosperm embryo sac is an 8-nucleate structure.
The primary endosperm cell is the tissue that nourishes the embryo. It does not degenerate after fertilization. So, options A and C are incorrect.
The egg cell is produced by megagametophyte, for fertilization. So, option D is incorrect.

Hence, the correct answer is option (B).

Note: Synergids are two cells of the embryo sac which are present towards its micropylar end. Their main function is to guide the pollen tube. The male gametes from the pollen grain are released into the cytoplasm of the synergids from where they reach the egg cell and fertilization occurs. Antipodals cells do not perform a major function. They provide nourishment to the developing embryo sac. The embryo sac is also known as a female gametophyte.