Double FERTILIZATION. ... Of the two sperm CELLS, one sperm fertilizes the egg cell, forming a diploid zygote; the other sperm fuses with the two polar NUCLEI, forming a TRIPLOID cell that develops into the endosperm. Together, these two fertilizationevents in angiosperms are known as double fertilization.
Double fertilization is a complex fertilizationmechanism of flowering plants (angiosperms). This process involves the joining of a female gametophyte (megagametophyte, also called the embryo SAC) with two male gametes (sperm).