flowering plants undergo a unique reproductive process where there are two fertilization events this double fertilization event occurs between the male reproductive organ the male geophy and the female reproductive organ the female geophy before the fertilization event can occur the ovule has to undergo some changes at present the OVU contains one reproductive cell known as the megaspore or Mother cell this cell is deployed and under goes meiosis producing four haid megaspores in the majority of species three of these megaspores degenerate leaving only one surviving megaspore this surviving megaspore expands and undergo three rounds of mitosis to produce eight hloy nuclei as the nuclei have not developed any individual division they initially share the same cytoplasm this complete structure is known as the embryo sac within the established embryo sac cell walls begin to form between most of the nuclei three cells named antipodal cells form opposite the opening of the OVU known as the micropile another three cells form above the micropile two of these are cids and the other is the egg cell this leaves two nuclei in the center of the ovule these Central nuclei remain together in one large cell it is the egg cell and this Central nucleate cell which will eventually become part of the double fertilization event in order for the double ferti ization event to occur the male gametes the sperm must travel from the anther to the embryo sac within the female reproductive [Music] organ the pollen grain contains two main cells a cell named the tube cell makes up the bulk of the pollen grain and the sperm cell which at this stage is known as the generative cell to reach the embryo sac a pollen grain must land on the stigma once landed it begins to germinate the tube cell forms a long structure down the style and into the ovary the generative cell travels behind the tube cell nucleus once near the ovary it divides by mitosis to produce two haid sperm cells the pollen tube reaches the micropile and releases the sperm cells into the embryo saac one of the two sperm cells fertilizes the egg cell this produces a diploid zygote which will become the embryo the other sperm cell moves up and fuses with both of the central nuclei forming a triploid cell this unusual triploid cell develops into an endosperm and serves as the embryo's food supply during early development it is only angiosperms flowering plants which have this double fertilization characteristic where a diploid zygote and a triploid endosperm form gymnosperms Pines tracheophytes Ferns and non- tropes mosses lack this double fertilization feature