CBSE Class 10 Science 2019 · Paper 31/3/2 · Question 4(b)

The movement of the leaves of the sensitive plant (touch-me-not) differs from the movement of a shoot towards light as follows. 1. Direction of the stimulus: the leaves fold up in response to touch, and the movement does not depend on the direction of the touch; the shoot moves in the direction of the stimulus, towards the light (phototropism). 2. Growth: the folding of the leaves is not a growth movement, since the cells change shape by losing water; the bending of the shoot is a growth movement, since auxin makes the shaded side of the shoot grow faster. 3. Speed: the leaves fold within seconds and open again later; the shoot bends slowly, over hours or days, and the bend is permanent.