In angiosperms, they have double fertilization event. Firstly, pollen goes to stigma (pollination). Following pollination, the pollen tube enters an ovule through the micropyle, and then proceeds to enter a degenerated synergid. There are two sperm cell (developt by pollen) and one of them migrates to egg cell to create a zygote and the other one migrates to central cell of embryo sec to create endosperm. These two fertilization happens nearly simultaneous. What if endosperm developed but egg and sperm cell cannot fusion event to create zygote or formation of zygote happens but other sperm cannot fertilizate endosperm or karyogamy development cannot works right (for example. sperm nucleus and one central cell nucleus merge but the other nucleus cannot like 2n+n) because of the some problem or mutation?