What are Stomata?

About Stomata:

• They are tiny openings or pores in plant tissue that allow for gas exchange. They are typically found in plant leaves but can also be found in some stems. 
• They 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 currents. 
  • 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.
  • A stomate opens and closes in response to the internal pressure of guard cells. These cells enlarge and contract to open and close stomatal pores.
  • Guard cells work to control excessive water loss, closing on hot, dry, or windy days and opening when conditions are more favourable for gas exchange. 
  • 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.
• For most plants, dawn triggers a sudden increase in stomatal opening, reaching a maximum near noon, which is followed by a decline because of water loss.