Blog 2: Double Fertilization

Flowering plants have the ability to reproduce asexually and sexually. When they do produce sexually, they undergo a process called double fertilization. A flowering plant has a female part and male part if they are a perfect flower. The female part consists of the stigma, style, ovary, and ovule, while the male parts consist of the stamen, that has the anther and the filament. We first begin with what happens in the female part of the flower, the ovule has a reproductive cell called the megaspore (the cell is a diploid and undergoes meiosis and produces 4 haploid spores). In most cases, 3 of the haploid spores degenerate and only leave one. The remaining haploid spore goes through 3 rounds of mitotic division and produces 8 haploid nuclei. Then, cell walls form between the nuclei and 3 nuclei move up while 3 move towards the ovule the remaining two stay in the middle and are called polar nuclei. Now begins the processes in the male parts of the flower, pollen grain lands on the stigma and begins to germinate and sends a long pollen tube through the style and ovary. The cell that traveled through the tube undergoes mitosis and produces 2 haploid sperm cells. One of the sperm cells fertilizes with the egg producing a zygote and the other sperm combines with the polar nuclei making a triploid which later becomes the endosperm. The endosperm provids food for the embryo.

Sources: http://bcs.whfreeman.com/thelifewire/content/chp39/3902001.html