Heliotrope

Heliotrope or heliotropism, etc.
Helius was god of the sun. The Greek root trop- refers to a turning in a certain direction. Heliotropism is a biological term which refers to the growth or movement of an organism towards or away from sunlight. A heliotrope is a genus of plant that behaves in that manner. Several scientific or technical words derive for the name of the sun-god, for example: a heliostat is an instrument that uses a mirror to reflect sunlight; heliotherapy, treatment by means of the sun's rays; heliotype, a photomechanical process of printing a plate, or the printing plate itself produced in this fashion; heliograph is an instrument used to photograph the sun; and heliocentric refers to anything that has the sun as a center or is relative to the sun.