Question

Compare the nastic and tropic movements in plants.

Answer 1

Paratonic movements:

1. Paratonic movements are also called induced movements. These growth-dependent movements occur due to the differential growth of a plant organ in response to an external stimulus.
2. Paratonic movements in plants are of two types: tropic and nastic movements.

Comparison of nastic movement and tropic movement in plants:

Nastic Movements	Tropic Movements
Nastic movements are non-directional movements.	Tropic movements are directional movements.
Nastic movements are independent of the direction of the stimuli.	Tropic movements are dependent on the direction of the external stimuli.
Nastic movements are either growth movements or can be caused due to turgor changes.	Tropic movements are curvature movements that occur due to unidirectional growth or cell division.
These movements are reversible and occur comparatively quickly.	These movements are irreversible and occur slowly.
Nastic movements may be scismonastic, photonastic and thermonastic.	Tropic movements include phototropism, geotropism, hydrotropism, chemotropism and thigmotropism.
E.g., drooping of the leaves of touch-me-not plant when touched.	E.g., the movement of a sunflower in the direction of sunlight.