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 towards 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. The segment flexes because the motor cells at the shadow side elongate due to a turgor rise. Heliotropism is a response to blue light. Some solar tracking plants are not purely heliotropic: in those plants the change of orientation is an innate circadian motion triggered by light, which continues for one or more periods if the light cycle is interrupted.
The billboard will be made up of panels that begin by being flat in the east and as the sun rises as does the temperature the flaps will begin to lift. By the end of the day and as the sun has gone down the flaps will be flat once again and will display another image. The billboard will reset itself much like the sunflowers do at night. The billboard will be completely solar powered.
Above is an example of what the billboard would look like in the east or flat.
As the sun rises the panels lift revealing another image.