Guard Cells in Stomata
Stomata are tiny openings on the surface of leaves that allow for gas exchange. Each stoma is surrounded by two bean-shaped cells called guard cells.

Function of Guard Cells
- Guard cells control the opening and closing of stomata to regulate the exchange of gases such as oxygen and carbon dioxide.
- When the guard cells are turgid or swollen with water, the stomata open, allowing for gas exchange and transpiration.
- Conversely, when the guard cells lose water and become flaccid, the stomata close to prevent excessive water loss.

Structure of Guard Cells
- Guard cells have a thickened inner wall and a thin outer wall, which allows them to change shape as they fill with or release water.
- They contain chloroplasts, which enable them to photosynthesize and produce energy for the opening and closing of stomata.

Role in Plant Adaptation
- The ability of guard cells to regulate stomatal opening and closing is crucial for plants to adapt to changing environmental conditions such as drought, heat, and light intensity.
- By adjusting the size of the stomatal opening, plants can conserve water, prevent wilting, and optimize photosynthesis.
In conclusion, guard cells play a vital role in the functioning of stomata and are essential for plant survival and adaptation in various environments.

The bean-shaped cells of stomata are called guard cells.
Stomata are tiny openings or pores found on the surface of leaves and stems of plants. They play a crucial role in facilitating gas exchange and regulating water loss through transpiration. The guard cells are specialized cells that surround and control the opening and closing of the stomata.
Guard cells have the following characteristics:
- Bean-shaped: Guard cells have a unique shape resembling a kidney or bean, with a thicker middle portion and two curved sides.
- Pair arrangement: They are usually found in pairs, with one guard cell located on either side of the stomatal pore.
- Chloroplasts: Guard cells contain chloroplasts, which enable them to perform photosynthesis and produce energy for their functions.
- Elasticity: The inner walls of guard cells are thicker and rigid, while the outer walls are thinner and more elastic. This structural arrangement allows the guard cells to change shape and control the opening and closing of the stomata.
- Stomatal pore: The stomatal pore is the opening between the two guard cells. When the guard cells are turgid or swollen, the stomatal pore opens, allowing the exchange of gases. Conversely, when the guard cells lose water and become flaccid, the stomatal pore closes, reducing water loss through transpiration.
Importance of guard cells:
- Gas exchange: Guard cells control the opening and closing of stomata, allowing the exchange of gases such as oxygen, carbon dioxide, and water vapor with the surrounding environment.
- Photosynthesis: The presence of chloroplasts in guard cells enables them to produce energy through photosynthesis, contributing to the plant's overall metabolic processes.
- Transpiration regulation: By opening and closing the stomata, guard cells help regulate the rate of transpiration, which is the loss of water vapor through the stomata. This process is crucial for maintaining the plant's water balance and preventing excessive water loss.
In conclusion, the bean-shaped cells of stomata are called guard cells. These specialized cells play a vital role in regulating gas exchange and water loss in plants.