Question

Even though each pollen grain has 2 male gametes, why at least 20 pollen grains are required to fertilize 20 ovules in a particular carpel?

Answer 1

Even though each pollen grain has two male gametes, only one male gamete is used for fertilizing an ovule, while the other fuses with the polar nuclei to form the endosperm. Therefore, 20 pollen grains are needed to fertilize 20 ovules, as each pollen grain can fertilize only one ovule.