Actinism

noun

1. The intrinsic property in radiation that produces photochemical activity.
2. In botany, the chemical action of sunlight on plants.
3. The radiation of heat or light, or that branch of natural philosophy which treats of the radiation of heat and light.
4. That property of light which, as may be seen in photography, produces chemical combinations and decompositions.
5. The property of radiant energy (found chiefly in solar or electric light) by which chemical changes are produced, as in photography.