Pollination and Fertilisation

Pollination and Fertilisation

6.3

Pollination and Fertilisation

Pollination is a process where a mature pollen is transferred from an anther to a stigma
Pollination can be occured by pollination agents such as insects,wind and animals
Two types of pollination:
1. Self pollination
2. Cross pollination

After fertilisation,the pollen grains starts to germinate:

1.	Pollen grain contains tube nucleus and generative nucleus attached to stigma The pollen grain starts to germinate to from pollen tube downward the style

2.	Tube cell forms pollen tube towards ovule The generative cells at the back of tube cell undergoes mitosis to form two male gametes

3.	When arrives at embryo sacs,the pollen tube breaks the micropyle.The tube cell degenerates The two male gametes enter embryo sac One male gamete fuses with an egg cell to form a diploid zygote (2n).Another male gamete fuses with two polar nuclei to form a triploid endosperm nucleus (3n) The fertilisation occured that involving two fusions of gametes is known as double fertilisation.

Double fertilisation:

Produces the diploid zygote to ensure the species genetic content is maintained
Produces triploid endosperm nuclei to store nutrients for germination
Create variation through meiosis and fertilisation of gametes
Ensure development of endosperm tissue only in the fertilised ovule