The leaves of a touch-me-not (chhui-mui) plant fold up and droop when touched. (i) Name the type of movement shown by this plant. (ii) Is any growth involved in this movement? Give a reason for your answer.
Generated by claude-sonnet-4-6 · 2026-06-26 00:59 · grounding rag
Model Answer
(i) The movement shown by the touch-me-not plant is called nastic movement (or immediate response to stimulus / seismonasty).
(ii) No, no growth is involved in this movement.
Reason: The leaves move in response to touch by changing the amount of water in their cells, causing the cells to swell or shrink and thus change shape. This is a rapid response that does not depend on cell division or elongation (growth). If the plant were prevented from growing, this movement would still occur.
Source: Chapter 6, Section 6.2 and 6.2.1
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Explanation
- Examiners expect the term "nastic movement" or at minimum a clear statement that it is movement independent of growth; some marks go to the correct naming.
- The key distinction CBSE tests here: seismonastic/nastic movement = no growth; tropic movement (e.g., bending toward light) = growth-dependent. State this contrast clearly.
- For the reason, always mention the mechanism: change in water content → swelling/shrinking of cells → change in shape. This earns the reasoning mark.
- Avoid writing "the plant feels pain" — that is incorrect and will lose marks.