Male gamete

• The formation of male gamete takes place inside the pollen, a more or less rounded structure.
• The male gamete is uninucleate and possesses a two-layered wall.
• The inner wall or the intine of the male gamete is soft and thin.
• The outer wall or the exine of the male gamete is tough and often provided with spinous outgrowth.
• Some weak spots called germ pores may be present in the exine of the male gamete.
• At the time of pollination, the stigma is viscous with a sticky substance containing sugar and other compounds.
• The sticky substance stimulates the pollen grains to germinate.
• Just before pollination, the nucleus of the pollen divides into two, the tube nucleus and the generative nucleus.
• On pollination, the pollen begins to germinate and the intine of the male gamete protrudes through the germ pore of the exine and elongates to form a pollen tube.
• The tube nucleus, carried along with the generative nucleus at the tip of the pollen tube controls the growth of the pollen tube.
• The pollen tube penetrates the stigma and grows down the style until it finally reaches the ovule.
• By the time the pollen tube reaches the ovule, the generative nucleus has already divided into two nuclei.