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Science · 2025 · 4 marks
CBSE 2025 · Region 6 · Set 1 · Q38
The growth movements of plant parts in which the direction of the stimulus determines the direction of the response is known as tropic movements or…
The growth movements of plant parts in which the direction of the stimulus determines the direction of the response is known as tropic movements or tropism. Plants also have non-directional movements which may not be growth dependent.
(I)
Name the movement which causes 'X' and 'Y' to grow downwards and upwards respectively. (Refer above figure)
(II)
Write the name of a hormone that plays a major role in (i) falling of leaves (ii) rapid cell division
(III)
(a)
Leaves of the sensitive plant move very quickly in response to 'touch'. How is this stimulus of touch communicated and explain how the movement takes place.
OR
(b)
Name the plant hormone which is synthesized at the shoot tip. How does this hormone helps the plant to bend towards light ?
Marking-scheme solution
(I)
'X' - Positive geotropism/ Negative Phototropism
'Y' - Negative geotropism / Positive Phototropism
(II)
(i)
Abscisic acid
(ii) Cytokinin
(III)
The plants use electrical- chemical means to convey information (touch) from cell to cell.
Plant cells change shape by changing the amount of water in them, resulting in swelling /shrinking of cells.
Auxin
When light is coming from one side of the plant, auxin diffuses towards the shady side of the shoots. This concentration of Auxin stimulates the cells to grow longer, on the side of the shoot which is away from light. Thus the plant appears to bend towards light.
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CBSE Class 10 Science past-paper question from the 2025 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.