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The pollen grain absorbs liquid from the moist surface of the stigma and the intine protrudes out through a germ pore. After the emergence of the pollen tube from the pollen grain, the pollen tube may enter the ovule either through the micropyle or by some other route. After entering the wall of the embryo sac the pollen tube during its entry into the embryo sac passes through the nucellar cells and the synergids. After the discharge of the contents of the pollen tube into the embryo sac, one male gamete fuses with the egg (syngamy) and the other with the two polar nuclei (triple fusion). In normal case one male gamete unites with the egg to form the zygote and the second travels a little farther and unites with the secondary nucleus. This process is known as double fertilisation. With the result of syngammy a zygote (2n) is formed, whereas the triple fusion results in the formation of endosperm nucleus (3n).
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