Explain double fertilisation in angiosperms.

(N/A) Double fertilisation is a complex fertilization mechanism unique to angiosperms.
$1$. Pollen deposition and tube growth: After pollination,the pollen grain germinates on the stigma to form a pollen tube. This tube grows through the style and enters the ovary,eventually reaching the ovule. Two male gametes are carried within the pollen tube.
$2$. Entry into the embryo sac: Upon entering one of the synergids,the pollen tube releases the two male gametes into the cytoplasm of the synergid.
$3$. Syngamy: One of the male gametes moves towards the egg cell and fuses with its nucleus. This fusion is called syngamy,resulting in the formation of a diploid zygote $(2n)$.
$4$. Triple fusion: The other male gamete moves towards the two polar nuclei located in the central cell and fuses with them. This fusion of three haploid nuclei $(n + n + n)$ is termed triple fusion,resulting in a triploid primary endosperm nucleus ($PEN$,$3n$).
$5$. Conclusion: Since both syngamy and triple fusion occur within the embryo sac,the process is known as double fertilisation. The central cell,after triple fusion,becomes the Primary Endosperm Cell $(PEC)$ and develops into the endosperm,while the zygote develops into the embryo.