Question

The egg apparatus consists of
A) Egg and antipodal cells
B) Egg and central cells
C) Egg and two synergids
D) Egg and one synergid

Answer 1

Egg apparatus is a group of three cells at the micropylar end of the embryo sac in seed plants. It is present to the micropyle which is the opening through which the pollen nuclei enters the ovule.

Complete Answer:
An egg apparatus is a group of three cells in the seven celled embryo sac of an angiosperm(seed plants). It comprises an egg cell and two associated cells called synergids. The Egg apparatus is located at the end of the embryo sac closer to the micropyle.

Option A: Antipodal cells are the three haploid cells in the mature embryo sac of flowering plants that are situated at the opposite end to the micropyle. These are not part of the egg apparatus. Therefore, this is an incorrect option.
Option B: The egg apparatus comprises egg cells and two associated cells called synergids. The central cell is a binucleate cell. Upon fertilization with one of the two sperm cells, it forms triploid endosperm to nourish embryo development. Therefore, this is an incorrect option.
Option C: The ovule is a megasporangium that contains female reproductive cells. The functional megaspore undergoes three mitotic divisions. During the first division, it produces an oval-shaped embryo sac. The two nuclei shift to the two ends and divide there twice forming four nucleates and then eight nucleate structures. One nucleus from each side moves to the middle. They are called polar nuclei. The three nuclei at the micropylar end form egg apparatus. It contains one egg and two associated cells called synergids cells. The remaining three antipodal cells are present at the chalazal end. Therefore, this is the correct option.
Option D: The egg apparatus comprises egg cells and two associated cells called synergids. Therefore, this is an incorrect option.

Hence option ‘C’ is the correct answer.

Note: The cells of an unfertilized ovule are 8 in number and arranged in the form of 3+2+3 (from top to bottom) i.e. 3 antipodal cells, 2 polar central cells, 2 synergids & 1 egg cell