Pollination leads to fertilization by facilitating the delivery of pollen grains to the pistil, which then allows the male gametes within the pollen to reach and fuse with the egg cell inside the ovule.
Here's a breakdown of the process:
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Pollination: This is the transfer of pollen grains from the stamen (the male part of the flower) to the pistil (the female part of the flower). Pollination can occur through various means, including wind, water, insects, birds, or other animals.
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Pollen Grain Germination: Once a pollen grain lands on the stigma (the receptive surface of the pistil), it germinates if the stigma is receptive and the pollen is compatible. This germination involves the pollen grain forming a pollen tube.
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Pollen Tube Growth: The pollen tube grows down through the style (the stalk of the pistil) towards the ovary, which contains the ovules. The pollen tube serves as a pathway for the sperm cells to reach the egg cell.
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Entry into the Ovule: The pollen tube eventually reaches an ovule and enters it, typically through a small opening called the micropyle.
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Fertilization: Inside the ovule, the pollen tube releases two sperm cells. One sperm cell fuses with the egg cell, forming a zygote. This fusion is fertilization. The other sperm cell fuses with the polar nuclei, forming the endosperm, which provides nourishment to the developing embryo. This double fertilization is a unique characteristic of angiosperms (flowering plants).
In summary, pollination is the precursor to fertilization. It gets the pollen to the right place. The pollen tube then enables the male gametes to reach the egg and fertilize it within the ovule.
