Stomata are tiny openings found mostly on the surface of leaves that allow gases to move in and out of the plant. They are surrounded by two specialized cells called guard cells, which control their opening and closing. Through this mechanism, stomata play a vital role in regulating gas exchange and water balance in plants.
Here’s how stomata regulate gas exchange:
1. Opening of Stomata (During the Day)
- When there is light, photosynthesis begins in the leaf.
- The guard cells take in water by osmosis and become turgid (swollen).
- As they swell, the inner walls (which are thicker) pull apart, causing the stomatal pore to open.
- This allows carbon dioxide (CO₂) to enter the leaf for photosynthesis and oxygen (O₂), produced during the process, to exit.
- At the same time, water vapor also escapes through the open stomata (a process called transpiration).
2. Closing of Stomata (At Night or During Water Shortage)
- In darkness or during drought, guard cells lose water and become flaccid (shrunken).
- This causes the stomatal pore to close, reducing the loss of water vapor.
- When stomata are closed, gas exchange slows down, conserving moisture inside the plant.
3. Response to Environmental Conditions
- Light: Stomata open in light and close in darkness.
- Carbon dioxide level: When CO₂ inside the leaf is low, stomata open to allow more in.
- Water availability: If the plant is dehydrated, stomata close to prevent water loss.
- Temperature and humidity: High temperature or low humidity can cause stomata to close to reduce evaporation.
In simple terms, stomata act like tiny adjustable valves. They open to let in carbon dioxide for photosynthesis and release oxygen, while also allowing water vapor to escape. By opening and closing, they help the plant maintain a proper balance between gas exchange and water conservation.