The pollen grain enters the stigma of the pistil and attaches to it due to the peculiarities of the structure of the shell, as well as the sticky sugary secretions of the stigma, to which the pollen adheres. The pollen grain swells and grows, turning into a long, very thin pollen tube, which grows between the cells of the stigma and the column, and then grows into the cavity of the ovary.
In the pollen tube, two sperm (male gametes) are formed from the pollen grain.
When the pollen tube enters the embryo sac through the pollen duct, one of the sperm fuses with the egg. Fertilization occurs and a zygote is formed.
The second sperm is fused with the nucleus of the large central cell of the embryo sac.
Thus, in flowering plants, double fertilization occurs during fertilization: the first sperm fuses with the egg, the second with a large central cell.
This process was discovered in 1898 by the Russian botanist, academician S. G. Navashin.
Double fertilization is typical only for flowering plants.
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