Control and coordination
Tropic movement, in which movement of plants are dependent on the direction of the stimulus. If movement occurs in the direction of stimulus is called positive tropism and if the movement occurs away from the stimulus is called negative tropism. for example- Phototropism.
Whereas, nastic movements are the movements in which direction of the response is not dependent on the direction of the stimulus.
For example: When we touch the leaves of mimosapudica/ touch-me-not plant, its leaves fold inward and droop. the drooping independent of the direction from which the leaves are touched.