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(i) Leaves of 'chhui-mui'… (Class 10 Science 2024, Q35b)

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ScienceCBSE Class 10 · Board exam 2024, set 31/4/1 · 5 marks · Long answer

CBSE Class 10 Science 2024: question 35(b)

Set in the CBSE Class 10 board exam of 2024, paper 31/4/1, section D, question 35(b), for 5 marks. Try it first; the hints and our step-by-step solution are below.

Q35(b) · 5 marks · Long answerControl and Coordination

(i) Leaves of 'chhui-mui' plant begin to fold up and droop in response to a stimulus. Name the stimulus and write the cause for such a rapid movement. Is there any growth involved in the movement ?
(ii) Define geotropism in plants. What is meant by positive and negative geotropism ? Give one example of each type.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2024 board paper, set 31/4/1.

Hints

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

Hint 1

Chhui-mui (touch-me-not) reacts when you touch it, and the movement is very fast.

Hint 2

A fast movement cannot be due to growth. Think about water in the cells. For geotropism, compare roots and shoots.

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. (i) The stimulus is touch.

    ½ mark

  2. Cause: the plant cells change shape by changing the amount of water in them. Cells near the base of the leaves lose water, which causes the leaves to fold and droop. Electrical-chemical signals carry the information from cell to cell.

    1 mark

  3. No, there is no growth involved in this movement.

    ½ mark

  4. (ii) Geotropism is the growth movement of a plant part in response to gravity.

    1 mark

  5. Positive geotropism: growth of a plant part towards gravity. Example: roots grow downwards.

    1 mark

  6. Negative geotropism: growth of a plant part away from gravity. Example: shoots grow upwards.

    1 mark

Answer: (i) Touch; change in water content of cells changes their shape; no growth. (ii) Geotropism is growth in response to gravity: positive (towards gravity), e.g. roots; negative (away from gravity), e.g. shoots.

Where the marks are

  • Stimulus: touch (½ mark)
  • Cause: change in the amount of water in the cells changes their shape (1 mark)
  • No growth involved (½ mark)
  • Definition of geotropism (1 mark)
  • Positive geotropism with roots as example (½ + ½ mark)
  • Negative geotropism with shoots as example (½ + ½ mark)

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 paper2024 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.