From NCERTAsked by Anonymous from Shanghai, China23 Oct 2026, 2:02 PM ISTUpdated
In one line
Stomata are tiny holes in leaves that help plants breathe and control water loss.
Stoma — In plants, a variable pore between paired guard cells A close-up view of a stoma (stomata) on a leaf, showing the guard cells that open and close the pore. Image: Wikipedia
The rule
Stomata are small openings on the surface of leaves that allow gases like oxygen and carbon dioxide to move in and out, and help control water loss through transpiration.
Let's understand it simply
Imagine you are in a crowded bus on a hot day. You open a window to let in fresh air and let out the heat. Stomata (singular: stoma) are like these windows for a leaf. They open and close to let in air (carbon dioxide) for making food and to let out oxygen and water vapor. Without stomata, the plant would not get the air it needs or could lose too much water.
How it works
Stomata are tiny pores, mostly found on the underside of leaves.
Each stoma is guarded by two guard cells that can open or close the pore.
When the plant needs carbon dioxide for photosynthesis, the guard cells open the stomata.
Oxygen (made during photosynthesis) and water vapor leave the leaf through the open stomata.
When it is very hot or dry, the guard cells close the stomata to save water.
How stomata work
Guard cells fill with water and bend, opening the stoma.
Carbon dioxide enters for photosynthesis.
Oxygen and water vapor exit through the open stoma.
When water is low, guard cells shrink and close the stoma.
The story behind it
Scientists first saw stomata under simple microscopes in the 1600s. They noticed these tiny holes and later found out they open and close. The word "stoma" comes from Greek, meaning "mouth." This fits because stomata act like mouths for the leaf.
Where you see it in real life
Morning dew on grass: Water vapor leaves through stomata at night and cools to form dew.
Wilting plants: If a plant loses too much water through open stomata, it wilts (droops).
Transpiration in trees: Big trees like banyan or neem lose lots of water through stomata, helping pull water up from the roots.
Closed windows in summer: On a very hot day, plants close their stomata, just like we close windows to keep cool air inside.
Rice fields: Farmers flood rice fields because rice plants can keep stomata open longer without drying out.
Why it matters
Stomata help plants get carbon dioxide for photosynthesis (making food).
They control how much water the plant loses, which is very important in hot or dry places.
Stomata help plants "breathe"—taking in oxygen at night and carbon dioxide during the day.
Understanding stomata helps farmers grow crops better, especially in dry areas.
Common mistakes
Thinking stomata are only for breathing. They also control water loss.
Believing stomata are always open. They open and close as needed.
Forgetting that stomata are mostly on the underside of leaves, not on top.
Remember it
Stomata are like tiny windows in leaves—opening for air, closing to save water.
Check yourself
What is the main job of stomata in leaves?
To let gases like carbon dioxide and oxygen move in and out, and to control water loss.
Why do stomata close on a hot, dry day?
To prevent the plant from losing too much water.
Where are most stomata found on a leaf?
On the underside of the leaf, to reduce water loss.
Why do plants need to open their stomata during the day?
To take in carbon dioxide for photosynthesis, which needs sunlight.
Quick recap
Stomata are tiny pores on leaves that let gases in and out.
They help plants take in carbon dioxide for photosynthesis.
Stomata control water loss by opening and closing.
