Question 1 Hard
A bubble moves 75 mm in 5 minutes. Calculate the rate of uptake in mm per minute.
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Answer: 15 mm per minute
- 75 ÷ 5 = 15.
- The rate is 15 mm per minute.
Transpiration and stomata: GCSE Combined Science Biology practice questions
A second set of questions on transpiration and stomata. They are different from the ones on the topic page. Try each, then open the answer and compare your working.
More questions
Question 2 Hard
A plant loses more water than it takes in. What word describes what the plant does?
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Answer: wilts
- The cells become flaccid.
- The plant wilts.
Question 3 Hard
Why is a potometer shoot cut under water? Give the substance that must be kept out of the xylem.
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Answer: air
- Air would block the xylem.
- So the shoot is cut under water.
Question 4 Hard
Name the process by which water enters root hair cells.
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Answer: osmosis
- Water moves from the dilute soil water into the cell.
- This is osmosis.
Question 5 Easy
What are the pairs of cells that open and close a stoma called?
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Answer: guard cells
- Two cells surround each stoma.
- They are guard cells.
Question 6 Easy
Name the cells at the tip of a root that take in water.
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Answer: root hair cells
- They have long thin extensions.
- They are root hair cells.
Question 7 Medium
Does more wind increase or decrease the rate of transpiration?
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Answer: increase
- Wind blows away humid air from the leaf.
- So the gradient is steeper and the rate increases.
Question 8 Medium
Does more light increase or decrease the rate of transpiration?
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Answer: increase
- Light opens the stomata wider.
- So more water vapour escapes and the rate increases.
Quick checks
Short questions with options. Choose one before you open the answer.
Check 1
What is transpiration?
Show answer
The loss of water vapour from leaves, mainly through the stomata.
Check 2
What is the transpiration stream?
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The continuous flow of water from the roots up the xylem to the leaves.
Check 3
How does water enter a root hair cell?
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By osmosis.
Check 4
Why is transpiration useful to a plant?
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It brings mineral ions, keeps cells turgid, supplies water for photosynthesis and cools the leaf.
Check 5
What do guard cells do?
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They open and close the stomata.
Check 6
What happens to guard cells when they are turgid?
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They bend apart and the stoma opens.
Check 7
Why do stomata open in the light?
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So carbon dioxide can enter for photosynthesis.
Check 8
How does higher temperature affect transpiration?
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It speeds it up.
Check 9
How does low humidity affect transpiration?
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It speeds it up, because the concentration gradient is steeper.
Check 10
How does wind affect transpiration?
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It speeds it up by moving humid air away from the leaf.
Check 11
How does light intensity affect transpiration?
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More light opens the stomata wider, so it speeds up.
Check 12
What does a potometer measure?
Show answer
The rate of water uptake by a shoot.
Check 13
What is the equation for the rate of water uptake?
Show answer
distance moved by the bubble ÷ time.
Check 14
Why is a shoot cut under water in a potometer?
Show answer
To stop air getting into the xylem.
Check 15
What happens to a plant that loses more water than it takes in?
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It wilts, because its cells become flaccid.
Check 16
What is the trade-off in opening stomata?
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It lets in carbon dioxide but also lets water out.
Check 17
What is humidity?
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The amount of water vapour in the air.
Check 18
What is a concentration gradient?
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A difference in concentration between two places.
Check 19
Why does lower humidity speed up transpiration?
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The gradient of water vapour is steeper, so it diffuses out faster.
Check 20
What happens to guard cells when they are flaccid?
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They close the stoma.
Check 21
How does transpiration help to cool a leaf?
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Evaporating water takes energy from the leaf.
Check 22
What does the water in the xylem carry up from the soil?
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Mineral ions.
Check 23
Why do plants close stomata when short of water?
Show answer
To save water, although photosynthesis slows.
Keep going with Transpiration and stomata
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