A plant's "eyes," or light-sensitive proteins, signal whether it is day or night, according to recent research published in the journal Nature.

An international team of researchers found that the responsible light-sensitive proteins are part of the "phytochrome" family, and are found in all pant leaves. When they detect sunlight, it triggers a change in their cells so that the plant can known whether it's in the sun or shade.

"You can think of them as the plant's 'eyes,'" Sebastian Westenhoff at the Department of Chemistry and Molecular Biology at the University of Gothenburg explained in a statement.

Most plants try to avoid darkness and instead reach for the sun's rays, so that they can, among other things, consume more carbon dioxide via photosynthesis.

Phytochromes control this light-detecting process when they change in composition. This protein has a three-dimensional molecular structure (like most proteins do), and its structure changes through light radiation, and signals are then passed onwards to the cells.

"We already knew that some form of structural change was taking place, since the light signals must be transferred onwards to the cell. What we didn't know, however, was how the structure changed, and this is what we have revealed," Westenhoff explained.

Westenhoff and colleagues used laser light and then X-rays to initiate and then create an image of the structural change in phytochromes of bacteria.

Scientists are excited by this discovery because it could in turn lead to more efficient crop production.

"Proteins are the factories and machines of life, and their structures change when they carry out their specific tasks. At the moment, it's usually not possible to determine these changes. But I believe that we can use similar experiments to determine many important structural changes in phytochromes and other proteins," Westenhoff added.