The process of fertilisation observed in angiosperms is called as double fertilisation. It is the combination of syngamy and triple fusion. Events during fertilisation are elucidated.
*As the pollen grain falls on the stigma of the flower, it germinates and forms a pollen tube. Pollen tube is guided by the secretions of the ovule. Pollen tube enters the micropylar region of the ovule.
*Embryo sac inside an ovule consists of antipodals, synergids, egg cell, a central cell with two polar nuclei.
*Pollen tube releases two male gametes into synergids cytoplasm. One of the male gametes fuses with the nucleus of egg cell by the process of syngamy to form diploid zygote(2n).
*The other male gamete fuses with the central cell and forms primary endosperm nucleus (PEN). This fusion is called as triple fusion. Hence, endosperm is triploid in nature.