Difference between tropic movement and nastic …

Nastic movements

→ Nastic movements are non directional responses to stimuli such as temperature and heat.
→ The most important feature of this type of movement is that movements are not governed by the direction of the stimulus.
→ They may be induced by touch (seismonastic), temperature (Thermonastic), light, and chemicals.
→ Whatever be the direction of stimulus, the movements always occur in a particular direction without reference to the direction of the stimulus
→ Example of seismonastic movement is movement of Venus fly trap.

  Tropic movement
→ Tropic movement is the response to stimuli that comes from one direction.
→ It is a directional movement.
→ If the movement of the plant part is towards the stimulus, then it is known as positive tropism . If the movement of the plant part is away from the stimulus, then it is known as negative tropism .
→ For example phototropism, Geotropism etc.
Tropisms and nastic movements are both plant responses to external stimuli. however tropisms are depend on the direction of the stimulus nastic movements do not depend on the direction of a stimulus