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Lesson 29 How does fertilization occur?

Lesson 29 How does fertilization occur?. A pollen grain has just landed on the pistil of a flower. It can’t move by itself, so how does it get to the ovary to fertilize the egg?. The top part of the pistil is sticky. It is called the stigma.

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Lesson 29 How does fertilization occur?

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  1. Lesson 29 How does fertilization occur?

  2. A pollen grain has just landed on the pistil of a flower. It can’t move by itself, so how does it get to the ovary to fertilize the egg?

  3. The top part of the pistil is sticky. It is called the stigma. The pollen grain sticks to the stigma when it falls on it.

  4. The nucleus of the pollen grain divides into 3 parts. - The tube nucleus digests its way through the material in front of it.

  5. The two sperm nuclei now move freely down the tube, to the ovary.

  6. The sperm nuclei are now able to get to the ovary, where the egg is stored. Only one sperm nuclei fertilizes the egg.

  7. The fertilized egg is called an embryo. This embryo may develop into a new plant.

  8. The second sperm nucleus joins the rest of the ovule and makes the endosperm, which will feed the embryo when it grows.

  9. The embryo and endosperm are surrounded by a tough outer shell covering. This shell covering is formed by the ovule wall. The embryo, endosperm, and the shell covering make up the seed.

  10. endosperm embryo shell covering

  11. The seed may not grow right away. It can remain dormant for a long time. What do you think dormant means? Dormant means a resting stage.

  12. When conditions are right, the seed will “wake up”. It will sprout and start to grow. The embryo will use the food stored in the endosperm until it can make its own food.

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