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How does double fertilization work in angiosperms?
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angiosperm
Snake gourd (Trichosanthes cucumerina) in bloom.
Double fertilization is a unique reproductive process in angiosperms that involves two distinct fusion events following pollination.21
When a pollen tube reaches the ovule, it releases two nonmotile sperm cells into the embryo sac. The process proceeds as follows:21
- Zygote Formation: One sperm cell fuses with the egg to form a diploid zygote, which eventually develops into the embryo.21
- Endosperm Formation: The second sperm cell fuses with two polar nuclei located in the center of the embryo sac. This "triple fusion" creates a triploid nucleus that develops into the endosperm, a nutrient-rich tissue that provides food for the developing embryo.213
This dual process ensures that the plant simultaneously creates the next generation (the embryo) and the necessary resources (the endosperm) to support its early growth. While most angiosperms follow this pattern, some basal species may form diploid endosperm, and in certain plants like orchids, endosperm formation is suppressed entirely.12