A. P. de Candolle called this phenomenon in "any" plant "heliotropism" (1832). They demonstrated no diurnal heliotropism but strong seasonal heliotropism. This is considered to be turgor-mediated heliotropism. Floral heliotropism is not necessarily exhibited by the same plants that exhibit leaf heliotropism. This form of heliotropism is considered to be growth-mediated. Leaf heliotropism is the solar tracking behavior of plant leaves. Heliotropism is a response to light from the sun. Some flowers exhibit heliotropism, changing orientation to follow the sun. This tracking of the sun in young sunflower heads is called heliotropism.