Explain Microgametogenesis and structure of male gametophyte.

A newly formed pollen grain possesses a very dense cytoplasm with a central nucleus. As the cell increases in size, the vacuole develops and the nucleus is sifted to the other side adjacent to the wall. The nucleus divided into two smaller generative towards the wall and a larger vegetative nucleus towards the center. After this generative nucleus divides into the nucleus stage. These are called sperms nuclei or male gametes. At the three called stages normally on stigma, the exine of pollen grains ruptures at the germ pore and the intine in stigma out with its contents. A tube-like structure is formed called a pollen tube. The tube nucleus enters into the pollen tube and two male gametes follow the tube nucleus. As pollen tube contains the enzymes like amylase, invertase, phosphatase, pectinase, lipase, etc. it can degrade the chemical contained in style and grows towards the ovary. In this way, a mature male gametophyte contains a pollen tube with a tube nucleus and two male gametes.