Invisible to humans electromagnetic radiation with wavelengths shorter than the "normal" and visible light and is beyond the violet. Ultraviolet radiation causes chemical reactions in many substances. She is also involved in the formation of ozone involved in the atmosphere. In living things, this can lead to harmful changes and prolonged influence mutations to lead. The Italian Pomologist Alberto Pirovano (1884-1973), by the way, experimented with UV light as early as 1912, in order to consciously bring about changes in the cell material.
Different plants as well as the Rebstock form as a defense mechanism against UV light phytoalexins how resveratrol, which in higher quantity especially in dark grapes is included. Vineyards at high altitude are exposed to more UV light. This can positively enhance the color in red wines. Due to the influence of UV rays, the wine can not be stored under dark bottles Käseln (Light taste) are caused. That's why mainly bottles with darker bottles of Color (brown, green, black) used.