Formation of male gametes from a pollen spore
i) The nucleus of a pollen spore products two nuclei by mitosis.
ii) The bigger nucleus is called tube nucleus and the smaller nucleus is known as reproductive nucleus.
Pollination and formation of male gametes:
i) Two nucleated pollen grains arc transferred to stigma through pollination.
ii) During this time exinc bunts out.
iii) The intine is extended to form a pollen tube which passes through the germpore and enters the ovule of an ovary.
iv) The tube nucleus remains at the anterior end while the reproductive nucleus lies behind it.
v) The reproductive nucleus divides through mitosis division forming two male gametes (n) and the tube nucleus is degenerated.