Tropism means movement of the part of the plant either in the direction of the stimuli or away from the stimuli. Stimuli can be light, gravity, water or chemicals. For example, in case of phototropism means movement of part of the plant in the presence of light, in this two type of movement is seen shoots moves or grows in the direction of light whereas in case of roots, it grows in the direction opposite to the light. So, with different stimulus plants show different tropism or directional movement.