Question

What is triple fusion? Where and how does it take place? Name the nuclei involved in triple fusion.

Answer 1

Triple fusion involves the fusion of two polar nuclei and a sperm nucleus that occurs in double fertilization and the final result is the formation of endosperm.

Complete answer:
Triple fusion is fusion which involves the fusion of two polar nuclei and a sperm nucleus which occurs in double fertilisation in a seed plant and it further results in the formation of endosperm.
This process occurs in the embryo sac of the angiosperms.

How does it take place?
In this fertilisation when the stigma comes in contact with the pollen grains then it germinates there and it gives rise to the pollen tube which enters in the ovule through the style. This pollen tube enters into one synergid as there are two synergids present so it enters in one of them and then after this two male gametes are released. From these two male gametes, one of them fuses with the nucleus of the egg cell in order to produce the zygote and this process is referred to as syngamy.

Now the other male gametes combine with the two polar nuclei which are located in the central cell then a primary endosperm nucleus which is triploid in nature is formed. This process involves fusion of three haploid nuclei and because of this it refers to as triple fusion. The end result of this process is the formation of endosperm.

During the process of triple fusion, there are three types of endosperm development:
- Cellular endosperm development : Example - Coconut meat
- Nuclear endosperm development : Liquid endosperm is developed from nuclear endosperm development such as Coconut water.
- Helobial endosperm development: Monocots

Note: Triple fusion is the fusion of the male gamete with two polar nuclei inside the embryo sac of the angiosperm. When pollen grains fall on the stigma, they germinate and give rise to the pollen tube that passes through the style and enters into the ovule.