Fertilization in flowering plants, also known as angiosperms, is a fascinating process that involves several key steps. It begins with pollination, where pollen grains from the male part of the flower (the anther) transfer to the female part (the stigma) of the same or another flower. This can happen through various agents such as wind, water, or animals, particularly insects.
Once a pollen grain lands on a compatible stigma, it begins to germinate. The pollen grain forms a pollen tube that grows down the style towards the ovary, which contains the ovules. Meanwhile, within the ovule, the process of fertilization starts to unfold.
As the pollen tube reaches the ovule, it releases two sperm cells. One of these sperm cells fuses with the egg cell to form a zygote, which is the first step in developing a new plant. The other sperm cell fuses with two polar nuclei to form the triploid endosperm, which will later provide nourishment to the developing embryo.
This double fertilization process is unique to flowering plants and is critical for the development of seeds. After fertilization, the zygote develops into an embryo, and the surrounding ovule becomes a seed, while the ovary matures into a fruit. This whole process not only leads to the formation of new plants but also contributes significantly to the biodiversity we see in flowering plants today.