Question

There is a Mimosa plant grown in one of the pots in the garden. It's leaves get 'folded up' on touching it. What is this behavior called in scientific language?
(a)Photonasty
(b)Hydronasty
(c)Thermonasty
(d)Thigmonasty

Answer 1

Hint: Mimosa pudinca plants are also known as 'touch me not' plants due to their distinctive folding upon touching, shaking, warming, or blowing. Any mechanical stimulation can produce an action potential to rise up in the stems and travel to the leaf which causes them close.

Complete answer:
This mechanism is an effect of evolution as a defense mechanism against predators or even to prevent loss of water by evaporation. Herbivores would not try to eat a fast-moving plant or insects would not lodge on the plant thus, this mechanism may have evolved though the reason is not yet clear. The mechanism is very energy consuming and needs increased photosynthetic activity which is hampered by the closing up of leaves.

Additional Information: -Mimosa is not a shade tolerant plant and it needs an ample amount of light to grow properly. It doesn't quite react a lot to thermal stimulation as much as it does to a mechanical one.
-Thigmonasty is the nastic response of a plant or fungus to stimulation by touch or vibration.
-Thigmonasty is independent of the direction of stimulus which is the condition in thigmotropic.
So, the correct answer is 'Thigmonasty'

Note: Other examples of plants that exhibit thigmonastic responses are the venus flytrap as it shuts when insects land on the flower and Thistles in Asteraceae which take part in pollination. Some fungi also exhibit this property.