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IGCSEBiology
Trial Class

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

Tropisms and Plant Hormones 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 understanding of how plants respond to stimuli using hormones, particularly auxin.

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 Extended 3 marks Difficulty 3/5

    Define the terms "phototropism" and "gravitropism".

    Show model answer and marking guidance
    1. Phototropism: a growth response of a plant to the direction of light.
    2. Gravitropism (geotropism): a growth response of a plant to the direction of gravity.
    3. Positive tropism = growth towards the stimulus; negative tropism = growth away from it.

  2. Question 2

    Paper 4 Extended 4 marks Difficulty 4/5

    Explain how auxin causes a shoot to bend towards a light source (positive phototropism).

    Show model answer and marking guidance
    1. Light causes auxin to move to the shaded side of the shoot tip.
    2. Higher concentration of auxin on the shaded side.
    3. Auxin promotes cell elongation in shoots.
    4. Cells on the shaded side elongate more than those on the lit side: causing the shoot to bend towards the light.

  3. Question 3

    Paper 4 Extended 3 marks Difficulty 3/5

    Explain why roots grow downwards (positive gravitropism) while shoots grow upwards (negative gravitropism).

    Show model answer and marking guidance
    1. Gravity causes auxin to accumulate on the lower side of both roots and shoots.
    2. In shoots, high auxin concentration promotes cell elongation: lower side grows more, bending the shoot upward.
    3. In roots, high auxin concentration inhibits cell elongation: upper side grows more, bending the root downward.

  4. Question 4

    Paper 2 Core 2 marks Difficulty 2/5

    Name the plant hormone responsible for controlling growth responses.

    Show model answer and marking guidance
    1. Auxin.
    2. Auxin is produced in the tips of shoots and roots.

  5. Question 5

    Paper 4 Extended 3 marks Difficulty 4/5

    A seedling is placed on its side in the dark. Predict and explain the direction of growth of the shoot and root after two days.

    Show model answer and marking guidance
    1. The shoot will curve upward (negative gravitropism): auxin accumulates on the lower side, promoting elongation there.
    2. The root will curve downward (positive gravitropism): auxin accumulates on the lower side, inhibiting elongation there.
    3. Both responses happen in the dark, showing they are gravitropic, not phototropic.

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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