Scientists at Purdue University have discovered the chemicals that protect plants from sunburn. They are called sinape esters, a group of molecules that can absorb ultra violet light across the entire UV-B spectrum. According to Timothy Zweir, Professor of Chemistry at Purdue, that makes them special. Similar sun-blocking molecules in plants leave gaps in the wavelengths that they absorb, letting some of the UV rays through. Not so with sinape esters, making them an ideal sunblock for plants.