London: Have you ever wondered why plants never get sunburnt? This is because plants make "sunscreen" in their leaves, say researchers who claim to have finally solved the mystery after a 15-year research.
Ultra-violet rays -- the most powerful part of the sun`s rays -- can damage both humans and plants. But plants rarely show signs of sun damage, despite being out in the open all day with no access to sunscreen or protective clothing.
Now, a team at Glasgow University has found that plants have evolved a way of making their own chemical "sunscreen" within their leaves, the `Daily Mail` reported.
A protein in their leaves, called UVR8, actually detects the presence of UV-B rays and starts off a chemical reaction that protects the leaves.
In their study, the researchers have revealed exactly how
plants "sense" UV-B light.
UVR8 is a "photoreceptor" -- a light detecting protein. Organisms use photoreceptors to sense particular regions of the daylight spectrum. Vertebrates, animals with backbones -- including human beings – have photoreceptors for vision.
Plants have photoreceptors that direct their growth towards a light source and trigger when they flower.
The team found that UVR8 is a completely new type of photoreceptor. The protein employs specific chemicals --"tryptophan amino acids" -- in its own structure to detect UV-B light. These amino acids very effectively sense UV-B.
Prof Gareth Jenkins, who led the study, has described the findings, published in `Science` journal as "groundbreaking".
He said: "The search for this UV-B photoreceptor was something of a Holy Grail for plant photobiologists and we were very pleased last year when we discovered that UVR8 was the UV-B photoreceptor. Now, we have found that UVR8 detects UV-B by an entirely novel mechanism."