Question

The correct sequence of events during double fertilization in angiosperm is
A. Triple fusion, Syngamy, Porogamy
B. Syngamy, Triple fusion, Porogamy
C. Porogamy, Syngamy, Triple fusion
D. Syngamy, Porogamy, Triple fusion

Answer 1

Hint: In the angiosperm life cycle fertilization is a distinguished feature.
They have two male gametes. One of them fertilizes the egg cell and forms a zygote (syngamy), whereas the other male gamete fuses with the diploid secondary nucleus (triple fusion).

Complete answer: Angiosperm or flowering plants have naked ovules. The pollen grains and ovules are developed in flowers.
1. In a flower, the male sex organ is known as the stamen and the female sex organ is known as the pistil or carpel. The stamen has a slender filament having a tip known as anther.
The pistil is divided into three parts- stigma, style, and ovary.
2. Pollen grains are dispersed by pollinating agents from the anther to the stigma is known as pollination. The pollen germinates on the stigma, passes through the style, and finally reaches the ovarian cavity. Here, the pollen tube enters the ovule or embryo-sac through the micropyle. This is known as porogamy.
Pollen tubes can enter the ovule through chalazal tissue also.
3. The female gametophyte or embryo sac is present within the ovule.
The embryo-sac is a haploid tissue. It consists of a three-celled egg apparatus (one egg cell and two synergids), three antipodal cells, and two polar nuclei. The polar nuclei fuse and give rise to a diploid secondary nucleus.
4. When the pollen tube enters the embryo sac, the two male gametes are released.
One of the gametes fertilizes the egg cell and results in the formation of a diploid zygote is known as syngamy. Another male gamete fuses with the secondary diploid nucleus and forms a triploid primary endosperm nucleus (PEN) involves the fusion of three haploid nuclei hence it is termed as triple fusion.
5. Due to the occurrence of two types of fusion- syngamy and triple fusion inside embryo-sac, this event is known as double fertilization. This phenomenon is unique to flowering plants.

So, the correct answer is “Option C. Porogamy, Syngamy, Triple fusion.”.

Note: The product of triple fusion- primary endosperm nucleus (PEN) after division gives rise endosperm. The endosperm contains nutrients, which helps in the development of embryos.