The movement of plant parts in response to non-directional stimuli. The stimulus may be external, such as the movement of Mimosa leaves when touch (thigmonasty), or internal, such as the sudden movement of plant parts due to changes in turgor pressure (seismonasty). Nyctinasty is the movement of organs, such as the opening of flowers during the day and closing at night, in response to the diurnal cycle.