Fertilisation in a plant

When the pollen grain has landed on the stigma, it sticks as the stigma produces two chemicals. The stigma also produces a hormone which enables the pollen to produce an enzyme. This enzyme allows the pollen to digest part of the style and form a tube leading down to the ovaries. When the pollen grain reaches the ovaries, it fuses with a ovum. The ovum produces a hormone which directs the pollen grain in the direction to go during its journey down the style.

Fertilisation occurs as the pollen fuses with the ovum to form a zygote. After this happens, the zygote begins to divide by mitosis. As it divides, it produces a hormone which catalyses various changes in the structure of the plant.

1. The sepal and petals may wither away and fall off as no more insects need to be attracted to the plant.
2. Similarly, the stamen, style and stigma would wither away and fall off.
3. The carpel [stigma, style and ovary] may harden and form a fruit.

The resulting fruit has one job: to ensure the dispersal of the seeds is effective.

The carpel is the female reproductive organ of the plant.

Note that meiosis does not occur in asexual plants to form gametes. Mitosis only occurs to produce genetically identical cells and so all genetic data is copied.