Pla make it clear for me?difference between pollen grain and pollen tube?

Question

will u plz tell me difference between pollen grain and pollen tube in gymnosperms?from wt plant class pollen tube and pollen grain evolved

Answer 1

Pollination occurs in cone-bearing plants when the wind blows pollen from the male to the female cone. Some pollen grains are trapped by the pollen drop, a sticky substance produced by the ovule, the egg-containing structure that becomes the seed. As the pollen drop dries, it draws a pollen grain through a tiny hole into the ovule, and the events leading to fertilization begin. The pollen grain germinates and produces a short tube, a pollen tube, which grows through the tissues of the ovule and contacts the egg. A sperm cell moves through the tube to the egg where it unites with it in fertilization. The fertilized egg develops into an embryonic plant, and at the same time, tissues in the ovule undergo complex changes. The inner tissues become food for the embryo, and the outer wall of the ovule hardens into a seedcoat. The ovule thus becomes a seed—a tough structure containing an embryonic plant and its food supply. The seed remains tucked in the closed cone scale until it matures and the cone scales open. Each scale of a cone bears two seeds on its upper surface.