Tropic Movements vs Nastic Movements
Difference between Tropic and Nastic Movement: Tropic movements and Nastic movements are the two types of induced or paratonic movements of curvature in plants.
Tropic movements: The paratonic (induced) movement of growth is called tropic movements. Here the stimuli are external and unidirectional. Example: phototropic movements (movement towards the light) geotropic movements (movement towards gravity), chemotropic movements (movement towards chemicals) etc.
Nastic movements: The paratonic movements of variations are called nastic movements. Here the stimuli are external and diffused (not unidirectional). Example: nyctinastic movements (movements in response to darkness), Seismonastic movements or Thigmonastic movements (movements in response to touch) etc.
The present post discusses the Similarities and Differences between Tropic Movements and Nastic Movements in Plants with a Comparison Table.
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Similarities between Tropic and Nastic Movement
Ø Both tropic movements and nastic movements are vital movements.
Ø Both are the movements of curvature.
Ø Both are paratonic (induced) movements.
Ø Both types of movements are induced by external stimuli.
Difference between Tropic and Nastic Movement
Sl. No. Tropic Movements Nastic Movements 1 Tropic movements are paratonic movements of growth. Nastic movements are paratonic movements of variations. 2 Example: Movement of shoot towards the sunlight (phototropic movement). Drooping of the leaves of Mimosa pudica due to touch (Thigmonastic movement). 3 Tropic movements are shown by plant organs with radial symmetry (such as root and stem). Nastic movements are shown by plant organs with bilateral symmetrical (flat) such as leaves and stomata. 4 Stimuli for the tropic movements are unidirectional and never diffused. The stimuli for the nastic movements may be unidirectional or diffused. 5 The tropic movements are related to the direction of stimuli. Nastic movements are NOT related to the direction of stimuli. 6 Tropic movements are comparatively slow movements. Nastic movements are quick movements. 7 Tropic movements are caused by the cell divisions in the organ. The nastic movements are caused by the change in the turgor pressure of the cells in the organ.
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