Why is the folding up of the leaves of a sensitive plant on touching with a finger not a tropism ?

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Solution

•The folding up of the leaves of a sensitive plant on touch with a finger is not a tropism as it is a form of non-directional movement with respect to the stimulus.
•This form of movement is depicted as a nastic movement that is not dependent on the direction of the stimulus
•The non-directional movement of the plant in response to the touch of an object is known as thigmonasty.

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Why is the folding up of the leaves of a sensitive plant on touching with a finger, not a tropism?

Q. Which of the following are not tropisms?
(i) growing of pollen tube in response to a sugary substance
(ii) folding up of leaves of sensitive plant in response to touch
(iii) winding of tendril around a support in response to touch
(iv) opening up of the leaves of a daisy flower in response to light
(a) (i) and (ii) (b) (ii) and (iii) (c) (i) and (iv) (d) (ii) and (iv)

When the leaves of a sensitive plant are touched with a finger, they fold up and when the light fades at dusk, the petals of a dandelion flower close.

(a) State one way in which the above two processes are similar.

(b) State two ways in which the above two processes differ.

Q. When the leaves of a Mimosa pudica plant are touched with a finger, they fold up quickly. This is an example of :
(a) chemotropism
(b) thigmonasty
(c) photonasty
(d) thigmotropism

Q. Which of the following is not caused by a growth movement?
(a) bending of the shoot of a plant in response to light
(b) closing up of leaves of a sensitive plant on touching with an object
(c) climbing up of a plant on an object by using tendrils
(d) movement of the root of a plant towards a source of water

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