Plants rely on sunlight to make their food, but they also need protection from its harmful rays, just like humans do.
Harsh ultraviolet radiation plants are exposed to daily can cause serious damage to plant DNA and, as a result, hinder plant growth.
Timothy Zwier and colleagues at Purdue University, decided to look further into the protection process and discovered a group of molecules in plants called sinapate esters that are produced and sent to the outer layer of the leaves to protect themselves from sun damage.
"This molecule is a fantastic sunscreen and can absorb a remarkably broad spectrum of UV-B light – the entire spectrum," says Zwier, Purdue University's M.G. Mellon Distinguished Professor of Chemistry.
"It also is incredibly good at soaking up those rays, with each molecule capturing an impressive amount of UV-B light."
Intrigued by the work of a Purdue colleague, Clint Chapple, who discovered that these sinapate esters act as a plant sunscreen, Zwier and his team wanted to explore why these particular molecules were being used by the plants and uncover what makes them special in a new way.
In the study, the researchers coaxed the molecules into the gas phase and exposed them to UVB radiation from a laser in the laboratory.
They found that the particular sinapate ester that plants use as a screen against UVB was inherently capable of soaking up radiation at every wavelength across the UVB spectrum.
Thus, it is remarkably efficient at absorbing harsh radiation that could otherwise damage the plant.
Their findings further shore up the idea that this class of molecules does indeed comprise plant-made sunblock, the researchers say.
"This molecule absorbs all wavelengths of UV-B radiation with no gaps in coverage," adds Zwier.
"Other molecules that are very similar to sinapoyl malate have gaps in their spectra that let some of the UV-B light slip through. This broad spectrum is exactly what is needed for a good sunscreen, that all wavelengths of harmful radiation are absorbed with high efficiency."
In addition to Zwier, co-authors of the paper include graduate students Jacob Dean and Patrick Walsh and visiting scholar Ryoji Kusaka from Purdue’s Department of Chemistry, and Florent Allais from AgroParisTech in France. It received funding from the Department of Energy Basic Energy Sciences and is published in the Journal of the American Chemical Society.