Fertilization can be defined as the fusion of the male gametes (pollen) with the female gametes (ovum) to form a diploid zygote. It is a physicochemical process which occurs after the pollination of the carpel. The complete series of this process takes place in the zygote to develop into a seed.
Fertilization in plants occurs after pollination and germination.
Pollination occurs through the transfer of pollen which is the male microgametes of seed plants, producing the sperm – from one plant to the stigma (the female reproductive organ) of another. The pollen grain takes up water and germination occurs. The germinated pollen grain sprouts a pollen tube, which grows and penetrates the ovule (the egg structure of the plant) through a pore called a mycropyle. The sperm is then transferred through the pollen tube from the pollen. The image given below shows the picture of different parts of the plant and where the fertilisation takes place.
- In flowers, the pollen grain germinates after the pollination of the carpel and grows into the style by creating the pathway for the pollen grain to move down to the ovary.
- The pollen tube opens into the ovule through the micropyle and bursts into the embryo sac. Here, the male nucleus unites with the nucleus of an egg inside the ovule forming a diploid zygote, which later swells up and develops into a fruit.
- When a pollen grain lands on the stigma of the suitable flower, it makes a tiny tubule through style to the ovary.
- The pollen grain carries male gamete which meets the female gamete in the ovule and fertilization takes in flowers. The cell which results after fusion of the gametes is called a zygote which further develops into embryo.