We’ve all spent a little too much time on the beach and gotten sunburn: when our skin gets red and aches. But have you ever wondered how plants, which spend their whole life sunbathing, never get burnt? Scientists in Indiana asked themselves this same question and here’s what they found out.
For a plant to survive, it needs to carry out photosynthesis, which uses ultraviolet light as energy to drive the whole process to completion. But UV radiation is also what harms us and causes sun burns. There is an obvious problem here, because how can plants absorb UV for photosynthesis but also block it to remain healthy? This is a bit of a trick question, as there are many different types of ultraviolet radiation depending on the frequency, each one with its own properties. The one we’re interested in today is UV-B since it is the one that commonly causes sunburns.
It’s been known for a while that a group of molecules, called sinapate esters, are found on a top layer of plant epidermis, and their abilities include absorbing light energy for photosynthesis and blocking the harmful frequencies. Now, these seem like the answer to the question I posed before, right? Yes, but until now, scientists, although they knew their effects, didn’t know precisely how they worked.
Here’s when the team at Indiana, lead by Timothy Zwier, come into the picture. They decided to investigate sinapoyl malate, a certain sinapate ester that can do most of the radiation absorbing by itself. To find out what frequencies this chemical absorbed, they went through a very interesting process. It starts by cooling a sample to close to O degrees Kelvin, or absolute zero. This causes it to become gas molecules, which can be kept functional if they are surrounded by argon gas atoms. Then, a UV-B laser is shot at them and the frequencies absorbed and transmitted are ready to be measured.
The results were absolutely fascinating. This small little molecule, when covering a leaf or any plant structure, can absorb the whole of the UV-B spectrum of light, effectively blocking all common harmful light. By doing this, the interior of the plant is left unharmed and protected form the adverse effects of radiation, including mutations in the fragile DNA sequence.
It is a truly effective method, since plants are exposed to sunlight all day long and are never burnt, so some possible applications of this substance include the production of suntan lotion for us humans lacking godly molecules on our skin, or creating even more UV-protected plants in case of increased UV radiation, like that caused by the disappearing ozone layer.
If you want to read the article: http://pubs.acs.org/doi/abs/10.1021/ja5059026