Double fertilization or triple fusion are common in angiosperms.
Let us study about double fertilisation and triple fusion
In the phenomena, one female gamete unites with two male gametes. One of the male gametes fertilizes the egg resulting in the formation of a zygote and the other unites with 2 polar nuclei for the formation of an endosperm.
Triple fusion is defined as fusion taking place between two polar nuclei and sperm nucleus. This happens during double fertilization in a seed plant, and therefore gives origin to a triploid nucleus known as the Primary Endosperm Nucleus(PEN). The PEN later evolves into an endosperm.
Double fertilization or triple fusion in angiosperms
The fusion process occurs in the embryo sac of the angiosperms. In the event of fertilization, when the stigma comes in contact with the pollen grains, it germinates, giving rise to the pollen tube which enters the ovule through the style.
- This pollen tube then penetrates into one of the synergids, post which two male gametes are released.
- One of the two male gametes fuses with the nucleus of the egg cell to produce the zygote, this process is called syngamy.
- A primary endosperm nucleus, triploid in nature is formed when the other male gamete combines with the two polar nuclei that are found in the central cell.
- Since the process involves the combining or fusing of three haploid nuclei, it is known as triple fusion.
- The end result, consequence of the process of triple fusion is the formation of the endosperm. During the process of triple fusion, endosperm development of three types are noticed, which are given below:
(i)Cellular endosperm development – Example – Coconut meat
(ii)Nuclear endosperm development – Liquid endosperm is developed from nuclear endosperm development such as Coconut water
(iii)Helobial endosperm development – Monocots
Difference between triple fusion and double fertilization
The main difference between triple fusion and double fertilization is that in double fertilization, the embryo sac and two sperm cells fuse, whereas the sperm nucleus and two polar nuclei fuse in the central cell of the embryo sac in the process of triple fusion.