Scientists have discovered how plants know when to make their own sunscreen to protect themselves from harmful solar rays.
They have identified the "photoreceptor" in plants that recognises the presence of UV-B wavelengths in sunlight, stimulating the production of sunblock chemicals.
UV-B is the most powerful part of the daylight spectrum and is potentially damaging both to humans and plantlife.
University of Glasgow scientists have discovered how a protein, called UVR8, recognises UV-B light and then switches on changes in a plant's gene expression needed for it to produce its own sun block.
Gareth Jenkins, Professor of Plant Cell and Molecular Biology at the University of Glasgow and co-author on the paper, described the paper's findings as groundbreaking".
He said: "The search for this UV-B photoreceptor has been something of a holy grail for plant photobiologists.
"We have known for decades that plants can sense the presence of UV-B and that this stimulates the production of sunscreen chemicals that protect plants in sunlight, but we didn't know how plants were able to recognise the presence of UV-B. Now we do.
"We have managed to identify the photoreceptor that does this."
Plants need sunlight to harvest light energy and are therefore constantly exposed to UV-B. However, they rarely show signs of damage because they have evolved a way of protecting themselves from the sun's harmful rays by making their own sunscreen and depositing it in the outer tissues of leaves.
UVR8 is always present throughout a plant so it can respond immediately to sunlight.