AP BIOLOGY

Detailed explanation-1: -Pollen grains are small structures that contain androecium, a flower’s male reproductive organ. The tube cell turns into a pollen tube and the generative cell releases the sperm nuclei in the interior region of the pollen grain, which contains cytoplasm.

Detailed explanation-2: -There is no sperm present in a pollen grain. A pollen grain is a tiny male plant, a male gametophyte (gamete-forming plant). He is a multicellular organism (usually two cells in flowering plants, but more in the case of gymnosperm pollen) capable of producing sperm if he gets an opportunity.

Detailed explanation-3: -The male parts of a plant, called stamens, make pollen grains. These grains contain sperm cells. The female parts of a plant, called pistils, contain egg cells. During pollination, pollen grains travel from the male parts to the female parts.

Detailed explanation-4: -In the pollen grain, the generative cell gives rise to the sperm, whereas the vegetative cells have a tube cell that grows the pollen tube.

Detailed explanation-5: -The two sperm cells arise from the generative pollen cell either within the pollen grain or after germination inside the pollen tube.