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IGCSEBiology
Trial Class

Original practice · 5 questions · 15 marks · about 17 minutes

Transpiration Rate Factors Practice Questions

Biology editorial review is supported by the named review panel. Reviewer participation may vary by guide. Checked against Cambridge IGCSE Biology 0610 (2026–2028); last reviewed August 2026.

These questions test your ability to explain and predict how environmental conditions affect the rate of transpiration.

Before you open the answers

  • Attempt every question without notes.
  • Show working for calculations and write complete biological statements.
  • Use the suggested time as a guide, not a strict limit on the first attempt.

These are original practice questions. They do not reproduce an official Cambridge paper or official mark scheme.

  1. Question 1

    Paper 4 Both 4 marks Difficulty 3/5

    State four environmental factors that affect the rate of transpiration and describe the effect of each.

    Show model answer and marking guidance
    1. Temperature: higher temperature increases kinetic energy of water molecules, increasing evaporation rate.
    2. Wind speed: moving air removes water vapour from around the leaf, maintaining a steep diffusion gradient.
    3. Humidity: lower humidity increases the concentration gradient for water vapour, increasing transpiration.
    4. Light intensity: more light causes stomata to open wider, allowing more water vapour to escape.

  2. Question 2

    Paper 4 Extended 3 marks Difficulty 4/5

    A potometer measures the rate of water uptake by a plant shoot. Explain why this is only an estimate of transpiration rate.

    Show model answer and marking guidance
    1. Not all water taken up is lost through transpiration.
    2. Some water is used in photosynthesis / stored in cells.
    3. The potometer measures water uptake, not water loss directly.

  3. Question 3

    Paper 4 Both 3 marks Difficulty 3/5

    Explain why transpiration rate is highest on a hot, dry, windy day.

    Show model answer and marking guidance
    1. Hot: increases evaporation from mesophyll cells.
    2. Dry (low humidity): steep concentration gradient for water vapour diffusing out.
    3. Windy: removes water vapour from around the leaf, maintaining the gradient.

  4. Question 4

    Paper 2 Core 2 marks Difficulty 2/5

    A plant wilts on a hot day. Explain why.

    Show model answer and marking guidance
    1. Transpiration rate exceeds the rate of water absorption.
    2. Cells lose turgor / become flaccid: the plant cannot support itself.

  5. Question 5

    Paper 4 Extended 3 marks Difficulty 4/5

    Some plants in hot, dry climates have thick, waxy cuticles and fewer stomata. Explain how these adaptations reduce water loss.

    Show model answer and marking guidance
    1. Thick waxy cuticle is waterproof: reduces evaporation from the leaf surface.
    2. Fewer stomata means fewer openings for water vapour to escape.
    3. Both reduce transpiration, conserving water in dry conditions.

Mark the set consistently

Award a point only when the idea is clearly present in the written answer. Correct any missed point in a complete sentence, then test the same skill on a different question several days later.

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