Question

mention the reason for difference in ploidy of zygote and pen in an angiosperm. name both the events also.

Answer 1

pollen grain actually contain two male gametes .zygote is formed by fusion of one of the  male gamete of pollen grain (n)and female gamete -egg(n).so zygote is diplod .while primary endosperm nucleus PEN is formed by the fusion of other male gamete(n) with polar nuclei(2n) so PEN is triploid. zygote formation is syngamy(fertilization) and PEN formation is triple fusion (double fertilization).