Plants that reproduce sexually are known as flowering plants, and they produce two distinct sex cells. "Male" sex cells are found in pollen, while "female" sex cells are found in the ovary. Thus, the reproduction of flowering plants is similar to the sexual reproduction of animals, with a male sex cell of one plant fertilizing the female sex cell of another plant.
Male plant sex cells (also known as male gametophytes) are found in pollen. Pollen is produced by the process of meiosis, which is when a sex cell divides itself so that exactly half of the genetic code is in a cell (the other half of the genetic code for the new organism will come from the female sex cell). A pollen grain contains two or three male gametophytes, and the pollen itself is made of a chemical substance called "exine," which is composed of different sugars.
Spread of Pollen
Pollen is grown in the anther, which is found in the exterior of the flower. Tube cells in the anther become pollen tubes, which then burst open with pollen. Pollen itself does not have any inherent ability to move; instead, flowers rely on external causes (such as animals or wind) to transport their male sex cells from one plant to another. This process is known as pollination and, thanks to the exine on the exterior of the pollen grains, pollen can survive being carried long distances.
The female gametophytes for flower plants are the ovules, and they are located in the ovaries. Much like pollen, the ovules are produced through meiosis and they contain half of the plant's genetic code. Some flowers only have female or male sex cells, though it is not uncommon for a plant to be hermaphroditic. The ovule is in the interior of the plant; pollen must travel down a tube to fertilize the flower. Once fertilized, the fused ovules and pollen produces a seed.
The ovaries are part of an overall feature of a flower called the gynoecium. In addition to the ovaries, the gynoecium also contain the stigma and style, and all three parts are connected together. This is also called the pistil or carpal, and the main purpose of this interconnected feature is to create the tube, which the pollen must travel down in order to reach the ovaries. The primary purpose for this complexity is to keep the ovaries unexposed from the surrounding environment.
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