The process from plant fertilization to seed formation involves a sequence of critical steps, ultimately leading to the development of a new plant.
Steps from Fertilization to Seed Formation
Here's a breakdown of the steps involved:
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Pollination: This is the initial step, involving the transfer of pollen grains (containing the male gametes) from the stamen (male part) to the pistil (female part) of a flower. Pollination can occur via wind, water, insects, or other animals.
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Germination of Pollen Grain: Once the pollen grain lands on the stigma (the receptive surface of the pistil), it germinates. It forms a pollen tube that grows down the style (the stalk of the pistil) towards the ovary.
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Penetration of the Ovule: The pollen tube extends through the style and eventually enters the ovule within the ovary. The ovule contains the female gamete (egg cell).
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Fertilization (Syngamy): The male gamete from the pollen grain fuses with the female gamete (egg cell) inside the ovule. This fusion is called fertilization, and it results in the formation of a diploid zygote. In angiosperms (flowering plants), a process called double fertilization occurs. One sperm fertilizes the egg cell to form the zygote, and the other sperm fuses with the polar nuclei in the ovule to form the endosperm, a nutritive tissue.
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Zygote Development: The zygote undergoes mitotic cell division to develop into an embryo. The embryo is the immature plant, containing the rudimentary root (radicle), shoot (plumule), and seed leaves (cotyledons).
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Endosperm Development: The endosperm, formed during double fertilization, develops as a food source for the developing embryo. It provides the necessary nutrients for the embryo's growth and development.
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Ovule Development into Seed: After fertilization and the development of the embryo and endosperm, the ovule transforms into a seed. The integuments (outer layers) of the ovule harden and become the seed coat (testa), providing protection for the embryo.
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Ovary Development into Fruit: While the ovule is developing into a seed, the ovary surrounding it typically develops into a fruit. The fruit serves to protect the seed(s) and aid in their dispersal.
Summary
In essence, plant fertilization leads to zygote formation. The zygote develops into an embryo with the help of endosperm. The ovule matures into a seed that contains the embryo, and the ovary develops into a fruit.
