A team of scientists led by researchers at the Scripps Research Institute and the University of Glasgow investigated the marvelous mechanism by which plant cells detect harmful UV-B radiation and then send signals that activate cellular UV-B protection regimes. Without UV detection and prevention, and without all the biochemicals for photosynthesis, plants would have long ago died.
A protein in plants called UVR8 responds to light in just the UV-B range. The protein consists of two identical halves that automatically link to one another just before light hits them. Investigators learned that when UV-B light hits a particular amino acid near the center of the dual complex to change its electrical charges, the halves separate and activate the protein.You can read the rest of "Plant UV Detectors Could Not Have Evolved", in context, here.