Question

Pollen tube usually enters the embryo sac through?
a. One of the synergids
b. Directly penetrates the egg
c. Between one synergid and central cell
d. By knocking of antipodal cells

Answer 1

Hint: A pollen tube is part of the male gametophyte of seed plants. It acts as a conduit to transport the male gamete cells from the pollen grain, either from the stigma (in flowering plants) to the ovules at the base of the pistil, or directly through ovule tissue in some gymnosperms. A pollen tube usually enters the embryo sac through one of the synergids.

Complete answer:
 It penetrates through the filiform apparatus into one of the synergids. The eight nucleate female gametophytes of flowering plants have an egg apparatus at the micropylar end which in turn has one egg cell and two flanking cells. The flanking cells are known as synergids and have finger-like projections of the wall in their cytoplasm, the filiform apparatus. They serve as a site for entry of pollen tubes into one of the synergids followed by disintegration of later. The pollen tube pierces through the nucleus and traverses the wall of the embryo sac between egg and synergids. Filiform apparatus guide the pollen tube to the egg nucleus and thereby facilitate syngamy.

Hence, the correct answer is option (C)

Note: Pollen tube entry into the synergid cell of Arabidopsis is observed at a site distinct from the filiform apparatus. In some species that do not have synergids, like Plumbago zeylanica, the pollen tube approaches the embryo sac at the micropylar side and it delivers the sperm cells without distortion of the egg cell and the central cell.