The correct answer is option 3: seismonastic movements. Seismonastic movements, also known as thigmonastic movements, refer to the rapid plant movements that are triggered by touch or mechanical stimuli. These movements are a result of a change in turgor pressure in specific cells of the plant. When we touch the leaves of the `Touch me not` plant (Mimosa pudica), it responds by rapidly closing its leaves. This is a defense mechanism to protect itself from potential threats. Phototropism and nyctinasty, mentioned in options 1 and 2, refer to plant movements in response to light and darkness respectively, but they are not relevant in the context of the question. Chemonastric movements, mentioned in option 4, is not a scientifically recognized term and therefore an incorrect option.