The growth movements of plant parts in which the direction of the stimulus determines the direction of the…
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) [1]
(II) Write the name of a hormone that plays a major role in (i) falling of leaves (ii) rapid cell division [1]
(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. [2]
Solution
(I) 'X' – Positive geotropism/ Negative Phototropism
'Y' – Negative geotropism / Positive Phototropism
(II) (i) Abscisic acid
(ii) Cytokinin
(III) (a) 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.
