What are nastic and curvature movements? Give one example of each.

(a) Nastic Movements: They are non-directional curvatures movements of turgor or growth where the movements are determined by the structure of the responding organ irrespective of the direction of stimulus which is generally diffuse. Ex. Drooping and folding of leaves in Sensitive Plant in response to shock (seismonasty).

(b) Curvature Movements: They are changes in orientation of some plant parts in relation to others caused by intrinsic or external stimuli. Ex. Sleep movement or nyctinasty of legume leaves, bending of stems towards light (or positive phototropism of stems).