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How does double fertilization occur in angiosperms?
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Grandidier's baobas (Adansonia grandidieri) in Madagascar.
Double fertilization is a complex reproductive process unique to angiosperms (flowering plants) that results in the formation of both the embryo and the endosperm, a nutrient-rich tissue that supports seed development.12
The process begins after pollination, when a pollen grain lands on the stigma and germinates, sending a pollen tube down through the style toward the ovule. This tube carries two nonmotile sperm cells.32
Upon reaching the ovule, the pollen tube enters through the micropyle and releases the two sperm cells into the embryo sac:32
- Zygote formation: One sperm cell fuses with the egg cell to create a diploid zygote, which eventually develops into the plant embryo.42
- Endosperm formation: The second sperm cell fuses with two polar nuclei located in the center of the embryo sac. This fusion creates a triploid nucleus that divides to form the endosperm, which serves as a vital food-storage tissue for the developing seed.24
This dual fusion event ensures that the plant invests energy into both the offspring and its immediate nutritional support system.2