CBSE Class 10 Answered

When the movement is caused by presence or absence of light it is called photonastic movements. These movements are exhibited by florets and leaves which open in the morning and close at night. . These movements are popularly called as sleep movements. They are caused by changes in the osmotic potential of cells of the pulvinus

Seismonastic movements take place in response to touch, mechanical, electrical, thermal or chemical stimuli. This movement is shown by the sensitive plant, Mimosa pudica. They are caused by change in the osmotic potential of cells of the pulvinus due to the movement of K⁺ ions.