Which is the triploid tissue in a fertilised ovule? How is the triploid condition achieved?

(N/A) The triploid tissue in a fertilised ovule is the Primary Endosperm Nucleus $(PEN)$,which develops into the endosperm.
This triploid condition is achieved through a process called triple fusion.
During this process,one of the male gametes (haploid,$n$) fuses with the two polar nuclei (each haploid,$n$) present in the central cell.
This fusion of three haploid nuclei $(n + n + n)$ results in a triploid $(3n)$ nucleus.