An example of a nastic movement in plants is ________.

Nastic movements are growth-independent movements. These movements are not dependent on the direction of the stimuli. These movements mainly occur due to changes in the turgor pressure. 

Nyctinasty refers to the nastic movement of leaves or petals of higher plants in response to darkness.

Hence, the correct option is nyctinasty. The rest of the options are examples of tropic movements.