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Plants exhibit movements in… (Class 10 Science 2026, Q15)

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ScienceCBSE Class 10 · Board exam 2026, set 31/4/1 · 4 marks · Case-based

CBSE Class 10 Science 2026: question 15

Set in the CBSE Class 10 board exam of 2026, paper 31/4/1, section A, question 15, for 4 marks. Try it first; the hints and our step-by-step solution are below.

Q15 · 4 marks · Case-basedCompetency-basedControl and Coordination

Plants exhibit movements in response to various environmental stimuli to adopt and survive in their surroundings. These movements, influenced by external factors such as light, gravity, water and chemicals are regulated by specific plant hormones. For example, the differential growth of plant parts allows them to bend, grow or orient themselves in particular directions. Roots and shoots often show contrasting response to the same stimulus, highlighting the complex mechanisms involved in plant growth and development.

  1. (a)

    Why is hydrotropism essential for plants?

    0 marks
  2. (b)

    What role does auxin play in the growth of plants?

    0 marks
  3. (c)

    Differentiate between movement shown by the sensitive plant and tropic movement by plants (Two points).

    0 marks

  4. OR

    (c)

    OR: How does movement of roots differ from that of shoots in response to gravity and light?

    0 marks

Source: official question paper from cbse.gov.in (PDF). See it in the full 2026 board paper, set 31/4/1.

Hints

Open one hint at a time and try again before the next.

Hint 1

What do roots need to find in the soil?

Hint 2

Auxin works on cell length. Think of a shoot growing towards a window.

Hint 3

Compare speed, direction and the link with growth for the two kinds of movement.

Step-by-step solution

Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.

  1. (a) Hydrotropism makes roots grow towards a source of water. This lets the plant reach and absorb water and dissolved minerals, which it needs for survival.

    1 mark

  2. (b) Auxin promotes cell elongation. When light falls from one side, auxin moves to the shaded side of the shoot, and those cells grow longer. The shoot therefore bends towards light, so auxin controls tropic (directional) growth.

    1 mark

  3. (c) Sensitive plant vs. tropic movement:

    Movement in sensitive plant (Mimosa)Tropic movement
    Not directional; does not depend on the direction of the stimulusDirectional; occurs towards or away from the stimulus
    Not growth-related; caused by change in the water content of cellsGrowth-related; caused by unequal growth
    FastSlow

    (Any two points.)

    2 marks

  4. (c) OR: Roots vs. shoots:

    StimulusRootsShoots
    GravityGrow towards gravity (positively geotropic)Grow away from gravity (negatively geotropic)
    LightGrow away from light (negatively phototropic)Grow towards light (positively phototropic)

Answer: (a) It lets roots reach and absorb water and minerals. (b) Auxin promotes cell elongation and causes bending towards light. (c) Sensitive-plant movement is non-directional, fast and not growth-related; tropic movement is directional, slow and growth-related. OR: Roots show positive geotropism and negative phototropism; shoots show negative geotropism and positive phototropism.

Where the marks are

  • States that hydrotropism helps roots reach and absorb water and minerals (1 mark)
  • States that auxin promotes cell elongation or regulates bending towards light (1 mark)
  • Gives two correct differences between sensitive-plant and tropic movements (1 + 1 marks)
  • OR: Contrasts roots and shoots correctly for gravity and for light (1 + 1 marks)

Revise the chapter

Practise this chapterBoard-style questions from Control and Coordination, one at a time, marked against the answer key and marking points.Back to the full paper2026 board paper, set 31/4/1: every question, by section.

The question is transcribed from the official paper; figures are described in words. The solution, hints and chapter tag are ours. Spotted an error? Write tosupport@questionbuddy.in.