What is double fertilization in plants?

Double fertilisation in plants is a unique process where two sperm cells fertilise two different cells in the ovule.

Double fertilisation is a complex but fascinating process that occurs in angiosperms, or flowering plants. It involves two sperm cells, one of which fertilises the egg cell to form a zygote, while the other fertilises the central cell to form the endosperm. This process is unique to angiosperms and is a key factor in their evolutionary success.

The process begins when a pollen grain lands on the stigma of a flower. The pollen grain germinates and forms a pollen tube that grows down through the style towards the ovule. The pollen tube carries two sperm cells with it. When the pollen tube reaches the ovule, it penetrates through the micropyle, an opening in the ovule, and releases the two sperm cells into the embryo sac.

Inside the embryo sac, one sperm cell fuses with the egg cell to form a diploid zygote. This zygote will eventually develop into the embryo of the new plant. The other sperm cell fuses with the central cell, which contains two polar nuclei, to form a triploid cell. This triploid cell will develop into the endosperm, a tissue that provides nourishment to the developing embryo.

This process of double fertilisation ensures that the endosperm only develops in ovules where the egg cell has been fertilised, thereby preventing the wastage of resources. It also results in the formation of a seed that contains an embryo (the future plant) and endosperm (the food supply for the embryo), both of which are crucial for the survival and growth of the plant.