First 213 words of the document:
Fertilisation in Flowering Plants
1. A pollen grain lands on the stigma of a flower. The grain absorbs water
and splits open.
2. A pollen tube grows out of a pollen grain down the style. There are three
nuclei in the pollen tube - one tube nucleus at the tube's tip and two
male gamete nuclei behind it. The tube nucleus makes enzymes that
digest surrounding cells, making a way through for the pollen tube.
3. When the tube reaches the ovary, it grows through the micropyle, and
into the embryo sac within the ovule.
4. In the embryo sac, the tube nucleus disintegrates and the tip of the
pollen tube bursts, releasing the two male nuclei.
5. One male nucleus fuses with the egg nucleus to make a zygote. This
divides my mitosis to become the embryo of the seed.
6. The second male nucleus fuses with two other nuclei (polar nuclei) at the
centre of the embryo sac. This produces a cell with a large nucleus, which
divides to become a food store (endosperm) for the mature seed.
7. So a double fertilisation had taken place (2 male nuclei have fused with
female nuclei). This only happens flowering plants.
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Here's a taster:
1. What lands on the stigma of a flower?
2. How many nuclei are found in the pollen tube, and what are their
3. What does the tube grow through when it reaches the ovary?
4. What does the pollen tube release when it is in the embryo sac?
5. What does one of the male nucleus fuses with, and what does it make?
6. What is the purpose of the endosperm?
1. A pollen grain