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Introduction
It is a mechanism that occurs during angiosperm sexual reproduction.
Triple fusion occurs when a sperm nucleus and two polar nuclei fuse during double fertilisation in a seed-bearing plant, resulting in the development of endosperm.
The angiosperm embryo sac is where the fusing takes place.
When the stigma comes into contact with pollen grains during fertilisation, it germinates, forming the pollen tube, which enters the ovule through the style.
Where Does It All Begin?
Now that we’ve covered the steps of the triple fusion process, let’s talk about where it all begins.
The male gamete fuses with the nucleus of the egg cell to generate the zygote. The zygote remains inactive for a while, waiting for the endosperm to form from the primary endosperm cell that forms as a result of triple fusion.
The endosperm provides food for the expanding employo till it forms before the embryo from the zygote begins to develop.
Pollination
Pollination is the process by which the pollen particle from the male anther is transferred to the stigma of the female flower.
Pollination can be done by animals or by wind or air (abiotic agents) (biotic agents).
The pollen grains are carried by the wind, and if the pollen lands on an appropriate stigma, the pollination process is initiated.
This method necessitates additional pollen grain production, and most pollen grains remain unfertilized because to the low probability of landing on a stigma.
Because nectar-producing flowers are appealing to insects, just a few pollen grains stick to the insects, which land on the stigma of another plant when the insect drinks nectar from another plant.
The blooms are more beautiful in this situation and provide nectar for a variety of insects.
Double Fertilisation
When pollen grains land on the stigma, the pollen tube cell begins to develop, causing pollen-tube germination.
The pollen tube enters the stigma, develops towards the style, and eventually reaches the ovule’s base.
The two germ cells make their way to the ovule through the pollen tube development.
One germ cell fertilises the egg cell of the female flower in the ovule, resulting in the formation of the zygote.
Both nuclei are haploid before fertilisation, and after fertilisation, they become diploid. The zygote is the major product of fertilisation and later produces the embryo.
In angiosperms, however, a different fertilisation occurs, in which two polar nuclei and a sperm cell merge to form a triploid cell.
The event is known as Triple Fusion because it involves three cells fusing together to generate a new cell.
The Primary Endosperm Nucleus is formed as a result of the fusing of secondary nuclei.
Endosperm
Endosperm development is faster than embryo development, creating a hostile environment for the embryo’s growth.
It separates into three parts, resulting in triploid endosperm tissue. It contains reserve food components and is used to feed the embryo.
The primary endosperm nucleus divides into free nuclei in a series of nuclear divisions.
Free nuclear endosperm is the term for this stage of development. It eventually results in the formation of the cell wall.
The cellular endosperm in tender coconut is represented by the white kernel, whereas the free nuclear endosperm is represented by the water.
The Endosperm’s Purpose
After multiple fertilisation, the endosperm’s principal purpose is to provide nutrients to the developing embryo.
Embryo
The creation of a zygote is the consequence of fertilisation between the egg cell and the male germ cell of the plant.
Later, the zygote develops into an embryo, which is the primary cell that carries the information from the parent plants.
Conclusion
The merger of two polar nuclei and the sperm nucleus is known as triple fusion.
This occurs in a seed plant after double fertilisation, resulting in the formation of a triploid nucleus known as the Primary Endosperm Nucleus (PEN).
The PEN eventually becomes an endosperm. This fusion occurs largely in sexually reproducing plants known as angiosperms.
