In the given Angiosperm, 2n= 18
therefore n= 18/2 = 09
Pollen grain is the male gamete and gametogenesis is a result of meiosis of Pollen Mother cell that is deploid.
The meiosis -I is a reduction division and leads to formation of a haploid gamete.
Thus pollen grain will have n=09 chromosomes.
Endosperm is the result of Tripple fusion during double fertilisation event in Angiosperm.
Haploid male nucleus fuses with two haploid polar nuclei. thereby forming a triploid endosperm.
n=09.
thus 9+9+9 = 27 chromosomes.