Question

Shock movement in Touch me not plant is
A. Seismonasty
B. Photonasty
C. Chemonasty
D. Thermonasty

Answer 1

Hint: Mimosa pudica commonly known as Touch me not plant is sensitive to touch. It encloses its leaves when touched. It shows thigmonasty, which is a nastic movement having touch as a stimulus.

Complete answer: The Touch me not plant is known by so many names based on the fact that it closes its leaves when touched. It is known by names like a sensitive plant, sleepy plant, shame plant, etc. It is a creeping plant that grows annual flowers. It belongs to the pea or legume family. Its compound leaves fold inwardly and droop down when touched or shaken. These movements induce a protective response in the plant. The folding of leaves is termed as a defence mechanism and the leaves unfold or re-open after a few minutes. Plants show directional responses to certain stimuli. These are known as nastic movements. The movements may occur due to changes in turgor or growth. Temperature, humidity, light, touch, etc. acts as stimulus for these nastic movements. The nastic movements do not depend on the stimulus position as in tropic movements. The frequency of nastic movement depends on the intensity of the stimulus. Bending down a heavy flower is also a nastic movement. The Touch-me-not plant shows a specialized nastic movement where touch acts as a stimulus. It shows thigmonasty or seismonasty. Seismonasty is a response to shock.
Hence, the correct answer is option A.

Note: Various nastic movements correspond to specific species and their classification. Nyctinasty is a movement in response to night or dark. Thermonasty is a response to heat or temperature. Photonasty is a response towards light and chemonasty is a response to various chemicals and nutrients.