Question

What is the function of filiform apparatus in an angiosperm embryo sac?
A. Brings about opening of the pollen tube
B. Guides the pollen tube into a synergid
C. Prevents entry of more than one pollen tube into synergid
D. None of these

Answer 1

The angiospermic embryo sac which is also called as female gametophyte of the angiospermic plants is a tiny sac that consists of eight nuclei and some cytoplasm.

Complete Answer:
The embryo sac of the angiosperms consists of synergid cells which form up the filiform apparatus by developing their cell wall into a thick structure at the micropylar end of the ovule.

Let us analyze the option to find out the correct role of this filiform apparatus.
Option A: Pollen grains are released upon opening of anthers which pass through the filiform apparatus of the synergid cells to fertilize with the female egg and form a fertilized diploid egg.Therefore, this is the incorrect option.

Option B: Filiform apparatus is an apparatus that is formed inside the embryo sac of the angiosperms by the synergid cells. This apparatus helps the pollen tube towards the egg for fertilization to happen. Thus it helps in the reproduction process of the angiospermic plants. Therefore, this is the correct option.

Option C: One of the pollen tubes with its nuclei fuses with one haploid egg forming the fertilized egg. The other egg gets fertilized with two more pollen tubes forming the endosperm. The role of the filiform apparatus is to allow the entry of pollen tubes from the synergids to the egg. Therefore, this is the incorrect option.

Option D: Since one of the above mentioned options is correct, this is the incorrect option.

Thus, the correct option is B) Guides the pollen tube into a synergid.

Note: Gymnosperms have multicellular female gametophyte and consist of thousands of cells unlike angiosperm female gametophyte. In angiosperm, the embryo sac is haploid whereas the zygote and endosperm is diploid and triploid respectively.