What is meant by double fertilization? Explain.

$\rightarrow$ Pollen grain after dispersal from the anthers, are carried by wind or various other agencies to the stigma of a pistil. This is termed as pollination.

$\rightarrow$ The pollen grains germinate on the stigma and the resulting pollen tubes grow through the tissues of stigma and style and reach the ovule. The pollen tubes enter the embryo-sac where two male gametes are discharged.

$\rightarrow$ One of the male gametes fuses with the egg cell to form a zygote (Syngamy). The other male gamete fuses with the diploid secondary nucleus to produce the triploid primary endosperm nucleus (PEN). Because of the involvement of two fusions, this event is termed as double fertilisation an event unique to angiosperms.