Stomata are openings in the surface of the plant epidermis through which gases and water vapor pass. They are formed by two elongated cells whose shape is similar to bean grain or dumbbell depending on the species. These cells are called guard cells, and in their midst there is a slit called the ostiole.
The stomata make the exchanges between the external and internal environment of the plant. They regulate the size of the opening, so it is possible to increase or decrease the rate of perspiration of the plant.
Stomata are usually located at the bottom of the leaf, but in aquatic plants such as the water lily they are at the top and still in vertical growing plants on both sides.
