What is stomata and their functions in short ?
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In botany, a stoma (also stomate; plural stomata) is a tiny opening or pore that is used for gas exchange. They are mostly found on the under-surface of plant leaves. Almost all land plants have stomata.
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What Is the Function of Plant Stomata?
Different types and how they open and close
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Illustration of the function of plant stomata
ThoughtCo / J.R. Bee
by
Regina Bailey
Updated August 15, 2019
Stomata are tiny openings or pores in plant tissue that allow for gas exchange. Stomata are typically found in plant leaves but can also be found in some stems. Specialized cells known as guard cells surround stomata and function to open and close stomatal pores. Stomata allow a plant to take in carbon dioxide, which is needed for photosynthesis. They also help to reduce water loss by closing when conditions are hot or dry. Stomata look like tiny mouths which open and close as they assist in transpiration.
Plants that reside on land typically have thousands of stomata on the surfaces of their leaves. The majority of stomata are located on the underside of plant leaves reducing their exposure to heat and air current. In aquatic plants, stomata are located on the upper surface of the leaves. A stoma (singular for stomata) is surrounded by two types of specialized plant cells that differ from other plant epidermal cells. These cells are called guard cells and subsidiary cells.
Guard cells are large crescent-shaped cells, two of which surround a stoma and are connected to at both ends. These cells enlarge and contract to open and close stomatal pores. Guard cells also contain chloroplasts, the light-capturing organelles in plants.
Subsidiary cells, also called accessory cells, surround and support guard cells. They act as a buffer between guard cells and epidermal cells, protecting epidermal cells against guard cell expansion. Subsidiary cells of different plant types exist in various shapes and sizes. They are also arranged differently with respect to their positioning around guard cells.
Types of Stomata
Stomata can be grouped into different types base on the number and characteristics of the surrounding subsidiary cells. Examples of different types of stomata include:
Anomocytic Stomata: Possess irregularly shaped cells, similar to epidermal cells, that surround each stoma.
Anisocytic Stomata: Features include an unequal number of subsidiary cells (three) surrounding each stoma. Two of these cells are significantly larger than the third.
Diacytic Stomata: Stomata are surrounded by two subsidiary cells that are perpendicular to each stoma.
Paracytic Stomata: Two subsidiary cells are arranged parallel to the guard cells and stomatal pore.
Gramineous Stomata: The guard cells are narrow in the middle and wider at the ends. The subsidiary cells are parallel to the guard cells.
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Two Main Functions of Stomata:
The two main functions of stomata are to allow for the uptake of carbon dioxide and to limit the loss of water due to evaporation. In many plants, stomata remain open during the day and closed at night. Stomata are open during the day because this is when photosynthesis typically occurs. In photosynthesis, plants use carbon dioxide, water, and sunlight to produce glucose, water, and oxygen. Glucose is used as a food source, while oxygen and water vapor escape through open stomata into the surrounding environment. Carbon dioxide needed for photosynthesis is obtained through open plant stomata. At night, when sunlight is no longer available and photosynthesis is not occurring, stomata close. This closure prevents water from escaping through open pores.