The process of fertilization in flowering plants involves the fusion of male and female gametes within the ovule, leading to the formation of a zygote.
Here's a breakdown of the fertilization process in flowering plants:
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Pollen Tube Growth: After pollination, a pollen tube grows from the pollen grain, down through the style, toward the ovary.
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Entry into the Ovule: The pollen tube navigates to the ovule and enters through a small opening called the micropyle. According to the provided reference, "The pollen tube opens into the ovule through the micropyle."
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Reaching the Embryo Sac: The pollen tube then penetrates the embryo sac, which is the female gametophyte located within the ovule. The reference specifies that the pollen tube "bursts into the embryo sac."
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Gamete Fusion: Inside the embryo sac, the pollen tube releases two sperm cells (male nuclei).
- One sperm cell fuses with the egg cell to form a diploid zygote. The reference clearly states, "Here, the male nucleus unites with the nucleus of an egg inside the ovule forming a diploid zygote". This zygote will eventually develop into the embryo of the seed.
- The other sperm cell fuses with the central cell, which contains two polar nuclei, forming the triploid endosperm. The endosperm serves as a food reserve for the developing embryo.
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Zygote Development: The diploid zygote undergoes cell division and differentiation to form the embryo.
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Fruit Development: After fertilization, the ovary develops into a fruit, which encloses and protects the developing seeds. The provided reference states that the zygote "later swells up and develops into a fruit."
| Step | Description |
|---|---|
| Pollen Tube Growth | Pollen tube extends from the pollen grain toward the ovule. |
| Micropyle Entry | Pollen tube enters the ovule through the micropyle. |
| Embryo Sac Entry | Pollen tube enters the embryo sac. |
| Double Fertilization | One sperm fuses with the egg (zygote formation), the other with the central cell (endosperm formation). |
| Seed Development | The ovule develops into a seed containing the embryo and endosperm. |
| Fruit Development | The ovary develops into a fruit. |
In summary, fertilization in flowering plants is a complex process that involves the growth of a pollen tube to deliver sperm cells to the ovule, where double fertilization occurs, leading to the formation of both the embryo and the endosperm. The ovary then matures into a fruit.
