| 21. | A pollen tube is produced, which grows into the nucellus to provide nutrients for the developing sperm cells.
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| 22. | Plants that are self-sterile often inhibit the pollen grains from their own flowers from growing pollen tubes.
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| 23. | The presence of multiple grains of pollen has been observed to stimulate quicker pollen tube growth in some plants.
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| 24. | Stigma have been shown to assist in the rehydration of pollen and in promoting germination of the pollen tube.
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| 25. | In this example, pollen tube incompatibility and slower generative mitosis have been implicated in the post-pollination isolation mechanism.
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| 26. | The pollen tube elongates and pierces and grows through the megasporangium wall and delivers the sperm cells to the female gametophyte inside.
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| 27. | In oaks, early fertilized ovules prevent the fertilization of other ovules by inhibiting the pollen tube entry into the embryo sac.
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| 28. | Thus, kin recognition at the level of the pollen tube apparently leads to post-pollination selection to avoid inbreeding depression.
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| 29. | Exo-PGs play a role in enabling pollen tube elongation since pectin rearrangement is necessary for the growth of pollen tubes.
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| 30. | Exo-PGs play a role in enabling pollen tube elongation since pectin rearrangement is necessary for the growth of pollen tubes.
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