States of Stomata
Biology: Edexcel IGCSE, topic 3.2.2
State of Stomata
The state of stomata (open or closed) achieves a balance between allowing gases for photosynthesis into the leaves, and conserving water in the plant.
Abundant water
- When water is abundant (lots available) the plant can afford to lose water.
- So it opens the stomata to allow gases for photosynthesis to move freely in and out of the leaf.
Scarce water
- When water is scarce (rare), stomata close in order to prevent further water loss.
- This is achieved by guard cells returning to a limp state after they lose water.
Time of day
- At night, stomata close because, in the absence of sunlight, carbon dioxide is not required for photosynthesis.
- At this time, their only objective is to prevent water loss.
Test yourself on States of Stomata
Why do stomata close at night?
Which of the following cells are responsible for opening and closing the stomata?
At night, stomata will be...