DIFFERENCES BETWEEN TROPIC and NASTIC MOVEMENTS BSC part III BASIS OF TROPIC MOVEMENTS NASTIC MOVEMENTS COMPARISION Description Tropic movement is a directional This movement is a non-directional movement displayed by a plant in response displayed by plants to response to any external stimuli. external stimuli. External stimuli may External stimuli can be-light, gravity, include: temperature, light, chemical, touch, temperature, chemical, touch, changes in day and moisture/water. night. Nature Of Stimuli Stimuli for the tropic movements are The stimuli for the Nastic unidirectional and never diffuse. movements may be unidirectional or diffuse. Nature In tropism, the effect is more or less Most Nastic movements are permanent. temporary and reversible. Types Types of Tropic Movements include: Types of Nastic movements include: Geotropism, Phototropism Photonasty, Chemonasty, Thigmotropism, Chemotropism Thermonasty, Thigmonasty Hydrotropism, Thermotropism Specialization in Tropic movements are less specialized More specialized Function and in function and distribution than tropic Distribution movements. Response To In tropic movements, there is The direction of a Nastic movement Stimuli directional growth of a plant or part of is independent of where the a plant, in response to an external stimulus comes from. It is only the stimulus such as gravity or light and quality and not the direction of the therefore, the direction of the stimulus stimulus that trigger a response. controls the orientation of growth. Underlying Cause These are caused by the cell divisions in They are caused by the change in the organ. the turgor pressure of the cells in the organ. 1 DIFFERENCES BETWEEN TROPIC and NASTIC MOVEMENTS BSC part III Rate of response It is slow, delayed response as takes The response is fast, quick and place because of cell divisions and usually rhythmic as takes place due growth. to changes in turgor pressure. Occurrence Shown by all plants. Occur in special plants (like insectivores) or parts of plant Shown mostly by radial parts of plant (pulvinus). like roots, shoots etc. Shown mostly by dorsiventral parts of plants (like leaves) and flowers. By: Dr. Jyoti Pandey 2 .