What is nastics movement?
Nastic movements are non-directional responses to stimuli(e.g.temperature,humidity, light irradiance), and are usually associated with plants. The movement can be due to changes in turgor or changes in growth (therefore k+ ion concentration usually controls such movement is plants).
The movements not related to growth
The movement of a plant part in response to an external stimulus in which the direction of response is not determined by the direction of stimulus is called nastic movement.