pollen tube

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pollen tube The tube formed from a germinating pollen grain, and down which the 2 male gametes (sperm nuclei) pass to the ovum. In flowering plants each pollen tube penetrates the tissues of stigma and style into the ovary where it grows towards an ovule, passing down the micropyle to the nucellus and finally penetrating into the embryo sac. Here the tip of the tube ruptures, releasing the 2 male gametes: one of these fuses with the nucleus of the ovum; the other fuses with the 2 polar nuclei to give rise eventually to the endosperm.

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