Inside which cells of the embryo sac do the pollen tubes liberate their male gametes?
Synergids
The pollen tube enters the embryo sac through one of the synergids and liberates their male gametes and other contents into the synergids. One male gamete fuses with the egg to form diploid zygote while the other male gamete fuses with two polar nuclei to form triploid primary endosperm nucleus. This process is known as double fertilization.