In angiosperms, the fertilization process is unique and termed double fertilization. This involves the fusion of two sperm cells with different cells within the ovule, leading to the formation of two distinct structures.
Double Fertilization Explained
The process starts with pollination, where pollen grains are transferred to the stigma, traveling down the style to reach the ovule. The critical steps in double fertilization, according to the reference, are as follows:
- Entry of Sperm Cells: Two sperm cells enter the ovule via the synergid cell.
- Formation of Zygote: One sperm cell fuses with the egg cell, forming the zygote. This zygote will eventually develop into the embryo of the seed.
- Formation of Endosperm: The other sperm cell fuses with the central cell (containing two polar nuclei), forming the endosperm. The endosperm serves as a nutrient-rich tissue that nourishes the developing embryo.
Summary of Fertilization Events
| Fertilization Event | Sperm Cell Fuses With | Resulting Structure | Function |
|---|---|---|---|
| 1st Fertilization | Egg Cell | Zygote | Develops into the embryo |
| 2nd Fertilization | Central Cell (2 polar nuclei) | Endosperm | Nourishes the developing embryo |
The simultaneous formation of the zygote and endosperm is why it's called "double fertilization." It is a defining characteristic of angiosperms.
