Question

Thigmonastic movement is observed in
A) Crocus and Tulip
B) Chlamydomonas and Volvox
C) Ulothrix and Cladophora
D) Drosera and Dionaea

Answer 1

Hint: Thigmonastic movement or the seismonastic movement is the nastic response produced when a plant or a fungus undergoes tactile stimuli.

Complete answer:
Tropism can be defined as plant growth in response to stimuli . There are four types,
Geotropism - Plants grown in response to gravity
Hydrotropism - Plants grow either towards or away from water/ moisture
Traumatropism - Plants modify the orientation depending on the injury
Chemotropism - Plants grow in response to chemical stimulus from the external environment

Let us analyse the options for finding the correct answer.
Option A, B and C: All of these plants do not show thigmonastic movement.
Option D: Thigmonastic movement or seismonastic movement is the nastic response a plant or fungus produces in response to the tactile stimuli. This is most commonly observed in the carnivorous plants such as Dionaea and Drosera. Both these plants exhibit the thigmonastic movement in response to the insect touch which may serve as a meal for that particular plant species. As a result of this sense of touch, the plant moves its tentacles in the inward direction so that it could easily entrap its prey. Therefore, this is the correct option.

Thus, the correct option is option ‘D’ i.e, Drosera and Dionaea.

Note: There are two types of thigmotropism,
i) Positive thigmotropism - The response is towards the touch or stimuli.
ii) Negative thigmotropism - The response is away from the touch or stimuli