Question
What are the tropic tactic and nastic movements? Describe with an example.
Answer
- Tropic movements are directional movements of plant parts in response to external stimuli. They are caused by hormones called auxins. Examples of tropic movements are phototropism (movement towards light), geotropism (movement towards gravity), and hydrotropism (movement towards water).
- Tactic movements are directional movements of motile cells or organisms in response to external stimuli. They are caused by taxis, which is a type of movement that is directed towards or away from a stimulus. Examples of tactic movements are phototaxis (movement towards light), chemotaxis (movement towards chemicals), and thigmotaxis (movement towards touch).
- Nastic movements are non-directional movements of plant parts in response to external or internal stimuli. They are not caused by hormones. Examples of nastic movements are photonasty (movement of leaves in response to light), thigmonasty (movement in response to touch), and nyctinasty (movement in response to changes in light).
