Question

Which of the following movements is a nastic (non directional) movement?

• A. The bending of the shoot of a plant in response to light
• B. The closing up of leaves of a sensitive plant on being touched with an object
• C. The climbing up of a plant on an object by using tendrils
• D. The movement of the root of a plant towards a source of water

Answer 1

The correct option is B The closing up of leaves of a sensitive plant on being touched with an object

• The movement of a plant part in response to an external stimulus in which the direction of response is not determined by the direction of stimulus is known as a nastic movement.
• The stimuli may be classified as light, heat, touch or contact, etc.
• In nastic movement, from whichever direction the stimulus is applied, it affects all the parts of the organ of a plant equally and they always move in the same direction.
  
• The leaves of the sensitive plant (Mimosa) have the capability to display thigmonasty (touch-induced movement). The leaves respond to touch.

Hence, the correct option is B.