Trace and explain the steps involved in the formation of seed starting from pollination.
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1.)Once the plant reaches sexual maturity, the pollen grains present inside the anther burst open and then the process of cross-pollination or self-pollination occurs.
2.)Pollen grains on reaching the stigma of the flower, are stuck on its sticky surface. Then increasing the amount of water and minerals, the stigma attracts the pollen grains towards itself and thus the pollen tube starts to form and this tube goes all the through the style (the middle part of the flower) and reaches the micropyle ( the bottom most part of the ovary) and enters the ovary through it.
3.)Inside the ovary, on the top there are 3 antipodal cells, in the middle there is a bipolar nuclei cell and on the bottom there is the egg cell accompanied b 2 syrenoids.One of the two pollen grains fuse with the egg cell to form the embryo (this is called the process of fertilisation) and the other pollen grain fuses with bipolar nuclei cell to form endosperm which provides nutritional supplements for the development of the embryo.
First Fertilisation:
Pollen Grain (n) + Egg Cell (n) ⇒ Embryo (2n)
Second Fertilisation:
Pollen Grain (n) + Bipolar nuclei Cell (2n) ⇒ Endosperm (3n)
The process is also called triple fertilization.
4.)After the fertilization has occurred the petals and sepals fall off and the ovary becomes the fruit and the ovule become the seeds.
5.)Furthermore, this seed, on dispersion through biotic or abiotic factors and germinates, has cotyledons and the plumule (future shoot or stem) and the radicle (future roots) starts to develop over a period of time and give rise to a new plant
2.)Pollen grains on reaching the stigma of the flower, are stuck on its sticky surface. Then increasing the amount of water and minerals, the stigma attracts the pollen grains towards itself and thus the pollen tube starts to form and this tube goes all the through the style (the middle part of the flower) and reaches the micropyle ( the bottom most part of the ovary) and enters the ovary through it.
3.)Inside the ovary, on the top there are 3 antipodal cells, in the middle there is a bipolar nuclei cell and on the bottom there is the egg cell accompanied b 2 syrenoids.One of the two pollen grains fuse with the egg cell to form the embryo (this is called the process of fertilisation) and the other pollen grain fuses with bipolar nuclei cell to form endosperm which provides nutritional supplements for the development of the embryo.
First Fertilisation:
Pollen Grain (n) + Egg Cell (n) ⇒ Embryo (2n)
Second Fertilisation:
Pollen Grain (n) + Bipolar nuclei Cell (2n) ⇒ Endosperm (3n)
The process is also called triple fertilization.
4.)After the fertilization has occurred the petals and sepals fall off and the ovary becomes the fruit and the ovule become the seeds.
5.)Furthermore, this seed, on dispersion through biotic or abiotic factors and germinates, has cotyledons and the plumule (future shoot or stem) and the radicle (future roots) starts to develop over a period of time and give rise to a new plant
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51
The transfer of pollen grains from anther to the stigma of a flower is called pollination. Now the male gamete enters into the ovary where fusion of male and female gametes takes place. This process is called fertilisation.
After fertilisation of ovules various changes take place. The petals, sepsis and stamens are dried and destroyed. Only ovary remains. The ovary contains fertilised ovule. After fertilisation ovary containing a number of fertilised ovules is called fruit. The fertilised and developed ovule is called seed.
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