Plants can determine whether it is day or night due to presence of light-sensitive proteins in cells, according to a University of Gothenburg study.
Researchers said that the proteins found in leaves are part of the "phytochrome" family. They identify the presence of light and inform the cell whether it is day or night, or whether the plant is located in the shade or the sunlight.
"You can think of them as the plant's 'eyes'. Our study has shown how these eyes work at the molecular level," Sebastian Westenhoff at the Department of Chemistry and Molecular Biology said in a statement.
Most plants stay away from darkness and grow towards sun's rays in order to receive maximum amounts of carbon dioxide through photosynthesis. Phytochromes control this light-detecting process. The proteins in plants have a three-dimensional molecular structure similar to other proteins. Its structure undergoes changes based on the light radiation and the signals are then forwarded 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 said.
For the study, the researchers used laser light to trigger the structural change in phytochromes. They then used X-rays to model the structural change.
Researchers said that the finding can lead to 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 said.
The finding is published in the journal Nature.
In October 2013, University of Cambridge researchers found that plants use sugars to determine the time of day. Researchers said that plants, similar to animals, have a 24 hour 'body-clock' known as the circadian rhythm.
"Our research shows that sugar levels within a plant play a vital role in synchronizing circadian rhythms with its surrounding environment. Inhibiting photosynthesis, for example, slowed the plants internal clock by between 2 and 3 hours," researcher Dr Alex Webb said in a press release.
