Fertilization
Fertilization is the union of the male and female reproductive cells of a plant. Fertilization starts when a pollen grain lands on the stigma of the flower during pollination. It absorbs water and germinates, forming a pollen tube. This tube carries the sperm cell and it grows down the style. The pollen tube reaches the ovary and enters the ovule.
The sperm cell unites with the egg cell during the process of fertilization. This forms a fertilized egg called a zygote. The zygote develops into a new young plant or embryo in a seed.
This seed is actually the hardened ovule. The ovary matures and becomes the fruit. The petals are shed off as the fruit matures and grows bigger.
