Tropic movements, also known as tropism, are directional movements of bending or curvature that respond to an external stimulus. The direction of movement depends on the direction of the stimulus.
A tropic movement can either be positive or negative: towards the stimulus is said to be positive, and away from the stimulus is said to be negative.
Based on the nature of the stimulus, tropic movements can be of:
Phototropism- Stimulus is light,
Thigmotropism- Stimulus is touch,
Gravitropism- Stimulus is gravity.
Example:
The ‘Touch Me Not Plant’ or Mimosa pudica is an example of negative tropic movement because it moves away from the stimulus once touched.