CBSE Class 10 Science 2019 · Paper 31/4/1 · Question 13
- (a)Plants do not have any nervous system but yet, if we touch a sensitive plant, some observable changes take place in its leaves. Explain how could this plant respond to the external stimuli and how it is communicated.
- (b)Name the hormone that needs to be administered to (i) increase the height of a dwarf plant. (ii) cause rapid cell division in fruits and seeds.
Answer
The touch signal passes cell to cell and cells at the leaflet base lose water and shrink; the hormones are gibberellin and cytokinin.
(a) When the sensitive plant (touch-me-not) is touched, its leaflets fold up and the leaf droops. The cells at the point of touch detect the stimulus and pass the information on from cell to cell by electrical-chemical means, since plants have no nerves or other specialised tissue for conducting information. The cells at the base of the leaflets and of the leaf then change shape by changing the amount of water in them: they lose water and shrink, so the leaves fold. This movement is brought about by swelling and shrinking of cells, not by growth.
(b)(i) Gibberellin (auxin also earns credit).
(b)(ii) Cytokinin.
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