Question

The egg apparatus of angiosperm comprises
(a)An egg cell and two antipodals
(b)An egg cell and two synergids
(c)An egg cell and two polar nuclei
(d)An egg cell and the central cell

Answer 1

Hint: Double fertilization is a characteristic feature of angiosperms that involves the fusion of a female gametophyte with two male gametes. An embryo sac consists of three cells together at the micropylar end that collectively is known as egg apparatus.

Complete answer:
In angiosperms, the embryo sac has a characteristic distribution of the cells. The egg apparatus comprises two synergids and one egg cell. These synergid cells possess cellular thickenings at the micropylar tip termed filiform apparatus. This structure plays an important role in guiding the pollen tubes into the synergid. Except for the egg apparatus, three cells are also present at the chalazal end and are called the antipodal cells. There is also a large central cell with two polar nuclei. So, a typical angiosperm embryo sac has 7 cells within it that consists of 8 nuclei.
Double fertilization in angiosperm
-Pollen grains germinate on the stigma to produce a pollen tube that carries two male gametes and extends down towards the ovary via style.
-The pollen tube then enters into the ovule through the micropyle end and finally to the synergids through the filiform apparatus.
-The pollen tube releases two male gametes in the cytoplasm of synergids where one of the male gametes moves towards the egg cell and fuses with its nucleus and leads to the formation of zygote.
-The other male gamete moves towards the central cell and fuses with the two polar nuclei that produce a triploid primary endosperm nucleus (PEN).
So, the correct answer is ‘an egg cell and two synergids’.

Note: The endosperm produced from the double fertilization provides the nourishment to the developing embryo. In some plants, the endosperm is completely consumed by the developing embryo before seed maturation for example pea, groundnut, and beans.