Stomata are the tiny openings on a plant's leaf surface. A singular opening is called a stoma. The primary function of stomata is a gas exchange, not unlike the human equivalent of breathing.
How Do Stomata Work? Stomata are akin to pores in the skin on the underside of a land-based plant leaf. Their primary function is to take in carbon dioxide and release oxygen. The stomata open and close to allow this gas exchange. The technical term for this gas exchange and water exchange is transpiration. Plants take in the carbon dioxide and separate it into carbon dioxide atoms and oxygen atoms. The plant takes in the carbon, essential to its life and growth, and then the oxygen atoms attach to free hydrogen atoms, creating water. This water and the oxygen in it are then released into the atmosphere via the stomata. However, water is essential to the plant's existence; this means a mechanism is needed to replace the water lost in transpiration.
How Do Stomata Regulate Transpiration? Behind each stomata is a pair of guard cells. These cells are thought to open and close to facilitate the intake and release of water although they may have other unknown functions. This intake and release of water is facilitated by osmotic pressure. Osmotic pressure is the pressure created by water moving across a permeable membrane such as plant leaf. Water will naturally flow towards the highest concentration of atoms, ions and molecules in a liquid. This pressure is believed to cause the guard cells to open and close. The more water the plant has the more frequently the guard cells will open. Conversely, the less water a plant has, the guard cells will open less often.
Stomata and Photosynthesis Stomata are critical to the photosynthesis process. Photosynthesis is the process of converting light energy into chemical energy to be stored within a green plant for later use. A green plant needs to take in sunlight to create its food source. The energy from light produces a chemical reaction within the plant. This chemical reaction breaks apart and rearranges the molecules, which then turns the water and carbon dioxide into glucose, a simple sugar, which in turn feeds the plant. As the glucose is created, oxygen is created and then dispersed through stomata.
Environmental Impact on Stomata Heat and cold have an impact on the function of stomata. Too much heat can result in the stomata staying open and potentially drain the plant of its water source. Too much cold can slow or reduce the stomata's process, allowing it to retain too much water, which could then crystallize into ice and kill the plant. Chemicals, such as those used in crop dusting, could potentially enter the plant through the stomata, although this has yet to be proven conclusively. As the stomata is an actual opening into the plant's internal structure it can be the passage way for pathogens to infect the plant. It is thought that the guard cells may play a role in protecting the plant from infections introduced through the stomata.