Skip to content

Where are auxins synthesized… (Class 10 Science 2024, Q22)

questionbuddy.in/q/cbse-10-science-2024-31-3-1-q22-where-auxins-synthesized-how-they

ScienceCBSE Class 10 · Board exam 2024, set 31/3/1 · 2 marks · Very short answer

CBSE Class 10 Science 2024: question 22

Set in the CBSE Class 10 board exam of 2024, paper 31/3/1, section B, question 22, for 2 marks. Try it first; the hints and our step-by-step solution are below.

Q22 · 2 marks · Very short answerControl and Coordination

Where are auxins synthesized ? How do they promote phototropism ?

Source: official question paper from cbse.gov.in (PDF). See it in the full 2024 board paper, set 31/3/1.

Hints

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

Hint 1

Auxin is made at the growing tips.

Hint 2

Think about which side of the stem auxin moves to when light comes from one side, and what auxin does to cells.

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. Auxins are synthesised at the shoot tip (and root tip).

    ½ mark

  2. When light falls on one side of the shoot, auxin diffuses towards the shady side.

    ½ mark

  3. The higher auxin concentration on the shady side makes those cells grow longer than the cells on the lit side.

    ½ mark

  4. The unequal growth makes the shoot bend towards light. This is phototropism.

    ½ mark

Answer: Synthesised at the shoot tip; auxin moves to the shaded side, making cells there elongate more, so the shoot bends towards light.

Where the marks are

  • Site of synthesis: shoot tip (½ mark)
  • Auxin diffuses to the shady side (½ mark)
  • Causes greater cell elongation on the shady side (½ mark)
  • Shoot bends towards light, i.e. phototropism (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 31/3/1: 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.