The habit of some plants to move in the direction of the the adonis effect pdf was already known by the Ancient Greeks. They named one of those plants after that property Heliotropium, meaning sun turn. The Greeks assumed it to be a passive effect, presumably the loss of fluid on the illuminated side, that did not need further study.
Aristotle’s logic that plants are passive and immobile organisms prevailed. In the 19th century, however, botanists discovered that growth processes in the plant were involved, and conducted increasingly ingenious experiments. A botanist studying this subject in the lab, at the cellular and subcellular level, or using artificial light, is more likely to employ the more abstract word phototropism.
The French scientist Jean-Jacques d’Ortous de Mairan was one of the first to study heliotropism when he experimented with the Mimosa pudica plant. Heliotropic flowers track the sun’s motion across the sky from east to west. During the night, the flowers may assume a random orientation, while at dawn they turn again toward the east where the sun rises.
The motion is performed by motor cells in a flexible segment just below the flower, called a pulvinus. The motor cells are specialized in pumping potassium ions into nearby tissues, changing their turgor pressure.