Double fertilisation in the flowering plant

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2. Fertilisation
•When a pollen grain reaches the stigma, a
small tube grows out of it.
•This tube, called the pollen tube, carries
two male gametes and enters the ovule.
•One of the male gametes fuses with the
female gamete (the egg cell) and form a
single cell called a zygote.
•This process is called fertilisation.

3. Stigma
Style
Ovary

4. Pollen Grain

5. Pollen Tube

6. Tube Nucleus
Generative Nucleus

8. Tube nucleus
disintegrates
Mitotic division
of generative
nucleus to form
2 male gametes

10. 1 Male gamete fuses
with the 2 polar nuclei
to form the triploid
endosperm nucleus
1 male gamete
fuses with the egg
nucleus to form the
diploid zygote

11. 3N endosperm
nucleus
2N Zygote
Double
fertilisation

12. •In many flowers, the ovary swells after fertilisation to
become the fruit.
•In some plants like the pea, the ovary hardens to form the
pod.
FLOWER TO FRUIT

13. Ovule to Seed
•The walls of the ovules become hard and the ovules
become seeds.
•The zygote divides repeatedly and forms the embryp inside
the seed.
•The petals,sepals and other parts of the flower usually dry
up and fall off.