Transpiration & translocation
Edexcel GCSE Biology revision on Transpiration & translocation. Aligned to the Pearson Edexcel GCSE Biology 1BI0 specification. This bank has 25 practice questions on this topic.
Sample questions (3 of 25)
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Question 1
Which environmental factor directly causes the closure of stomata to reduce water loss?
- A) High light intensity
- B) Low water availability
- C) Increased wind speed
- D) Rising ambient humidity
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Answer: Low water availability
When soil water levels are low, guard cells lose turgor pressure and become flaccid. This causes the stomatal pore to close, which is a vital adaptation to conserve water and prevent wilting under drought conditions.
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Question 2
Which tissue is responsible for the bidirectional transport of dissolved sugars in plants?
- A) Xylem vessel elements
- B) Phloem sieve tubes
- C) Spongy mesophyll cells
- D) Root hair cell walls
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Answer: Phloem sieve tubes
Translocation occurs within the phloem, where sieve tube elements move glucose produced during photosynthesis. Unlike xylem, which only carries water upwards, phloem can transport sugars to any part of the plant requiring energy or storage.
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Question 3
Why does an increase in air temperature typically lead to a faster rate of transpiration?
- A) Water molecules move faster
- B) Stomata open more widely
- C) Diffusion gradient steepens
- D) Xylem vessels widen slightly
Show answer
Answer: Water molecules move faster
As thermal energy increases, the kinetic energy of water molecules inside the leaf increases. This causes them to evaporate from the mesophyll cells into the air spaces more rapidly, subsequently increasing the rate of diffusion out of the stomata.
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