Explain the process of fertilisation in plants. tilFIDescribe the mode of fertilization in plants with a diagram.
1) Fertilisation is the process of fusion of male and female gametes.
2) For the fusion of male and female gametes pollen grains have to reach the surface of the stigma. This is called pollination.
3) Pollen grains received by the stigma, germinate and give rise to pollen tubes. Only one pollen tube finally reaches the embryosac.
4) This tube will have two male nuclei, which migrate to the tip of the pollen tube at the time of fertilization.
5) Usually the pollen tube enters the ovule through micropyle and discharges the two male gametes into its embryosac.
6) One male nucleus (gamete) approaches the egg and fuses with it to form a diploid (2n) zygote. This is first fertilisation.
7) The other male nucleus (gamete) reaches the secondary nucleus (2n) and fuses with it to form endosperm nucleus which will be triploid. This is second fertilization in the embryosac.
8) Thus double fertilisation occurs in embryosac which is unique in flowering plants.