What process describes the sexual reproduction in plants when pollen enters the pistil of a flower?

The process being described is pollination, which is the transfer of pollen from the male anther of a flower to the female pistil. This is a crucial step in sexual reproduction for flowering plants. When pollen grains reach the pistil, they can germinate, leading to fertilization if successful.

Pollination is essential for the fertilization process because it ensures that the male gametes (contained within the pollen) come into contact with the female gametes (located in the ovules within the pistil). This is the first step that leads ultimately to the formation of seeds and fruits, which are critical for the continuation of plant species.

The term "pollenation" does not exist in botanical terminology, while fertilization refers to the union of male and female gametes, occurring after pollination. Germination, on the other hand, is the process whereby a seed develops into a new plant, which occurs later in the life cycle following fertilization and seed development.