What are stages of fertilization in a plant?

Fertilization in plants involves several key stages: first, pollen grains land on the stigma of a compatible flower, where they germinate and form a pollen tube. The pollen tube grows down the style to reach the ovule in the ovary. Once the pollen tube penetrates the ovule, it releases sperm cells, one of which fuses with the egg cell to form a zygote, while the other fuses with two polar nuclei to form the triploid endosperm. This process ultimately leads to seed development.