Explain the events that occur, upto fertilisation, when the compatible pollen grain lands on the stigma.

Explanation

When compatible pollen grain land on stigma, the pollen grains germinate and produce a pollen tube which passes through the tissue of stigma and style and finally reaches the ovary.
In the pollen tube generative cell mitotically divides to divides to produce two male gametes during the growth of pollen tube in the stigma. In some plants pollen grains shed at the three celled stage. In such plants pollen tubes already carry two male gametes. Pollen tube after reaching ovary, enter the ovule through the micropyle and them enters one of the synergids through the filiform apparatus. One of the male gametes moves towards the egg cell and fuses with tis nucleus. The fusion of male and female gametes is called syngamy and results in the formation of zygote.