The sensitive plant Mimosa pudica, also known as "touch me not," moves its leaves in reaction to touch or contact stimuli. This is a nastic movement of some sort. This sort of thing happens because of differences in turgor pressures in leaf cells. Growth has no bearing on this movement. These are asymmetrical movements. Phototropism is the migration of a shoot towards light. These trophic changes occur as a result of growth in one direction. As a result, this form of movement is directed and depends on growth. The migration of a sunflower in the direction of the sun is an example of phototropism.