What is triple fusion? Where and how does it take place? Name the nuclei involved in triple fusion.

(N/A) Triple fusion is the fusion of one male gamete with two polar nuclei inside the embryo sac of an angiosperm.
This process takes place inside the central cell of the embryo sac.
When pollen grains land on the stigma,they germinate to form a pollen tube that grows through the style and enters the ovule. The pollen tube enters one of the synergids and releases two male gametes. One male gamete fuses with the egg cell to form a diploid zygote (syngamy). The second male gamete moves towards the central cell and fuses with the two polar nuclei to form a triploid primary endosperm nucleus $(PEN)$. This process is called triple fusion because it involves the fusion of three haploid nuclei. It leads to the development of the endosperm.
The nuclei involved are one male gamete nucleus and two polar nuclei.