Question

with the help of labelled diagram ,explain double fertilization in angiosperms.

Answer 1

The process of fusion of one male gamete with the egg along with the union of the second male gamete with the two polar nuclei or the secondary nucleus is called double fertilisation.

Out of the two male gametes, one fuses with the egg to carry out generative fertilisation or syngamy. It gives rise to a diploid zygote or oosphere.

The nucleus of the second male gamete fuses with two haploid polar nuclei or diploid secondary nucleus of the central cell to form a triploid primary endosperm nucleus (PEN). The central cell is called primary endosperm cell (PEC). This is called vegetative fertilisation or triple fusion

                 couldn't manage to get the diagram but i hope the answer helps!!

Answer 2

$\huge\mathfrak\red{Answer :}$


The fertilization in flowering plants occur through the process of Pollination .​ 

Pollination is the transfer of pollen grains from the male parts of plant to the female parts of plant.

It is necessary in plants for fertilization. It is brought by external factors like wind, insects, water etc.

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→ A flower consists of two parts. One is male part and another is female part.

* Male parts consists of long, stalk part called Filament and upper broad portion called Anther. Anther contains pollen grains.

* Female parts consists of upper broad portion called Stigma. Middle thin part called Style and the lower portion called Ovary. Ovary conatins ovule.

→ When a pollen grain reach the stigma of the flower then it secretes some liquid substance which is absorbed by pollen grain. After it they form a pollen tube which ultimately reach the ovule of the ovary.

→ Now, the two male gamates (pollen grains) start travelling through this pollen tube and reach the ovule of the ovary, which contains egg and two polar nuclei.

→ When a male gamate fuse with egg then it forms zygote by the process of fertilization and this type of fertilization in plants is known as Syngamy. And when a another male gamate fuse with two polar nuclei, it is known as triple fussion; then it form primary endosperm nucleus. 

* Since, the fusion occurs two times. So, this type of fusion is known as as Double Fusion.

→ After is the zygote develops into the embryo and the primary endosperm nucleus into endosperm which provides nourishment to the growing embryo.

* After it the ovule develops into seed and ovary into fruit.

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