Plants live, breathe and require nutrients to stay alive, but also like mammals, they have internal clocks that help them tell the time, even in the absence of light.

According to a press release, scientists have made their new discovery and reported their findings in a study, published Wednesday in the journal Nature. The researcher suggests plants use sugars to help use their 24-hour "body clock."

The researchers found that photosynthesis plays a vital role for plants in maintaining their internal clock. Through photosynthesis, plants convert the sun's energy into nutrients and chemicals necessary for growth and basic functioning. Sugar is a main product of photosynthesis and is highly important in their timekeeping system.

"Our research shows that sugar levels within a plant play a vital role in synchronizing circadian rhythms with its surrounding environment," lead researcher Dr. Alex Webb, of the University of Cambridge, said. "Inhibiting photosynthesis, for example, slowed the plants internal clock by between 2 and 3 hours."

A plant's biological clock is also known as a circadian rhythm and it is used primarily to respond to sunrise. But even without light (say a cloudy day), they use this internal timekeeper to sense what time it is. This timing mechanism is very important for keeping a competitive advantage in obtaining necessary nutrients, as well as processes like flowering, leaf movement and fragrance emissions.

For the study, the researchers monitored seedlings in a CO2-free environment in order to stop photosynthesis. They also grew biologically altered plants and found sugars were vital in regulating genes that control the 24-hour rhythm.

"The accumulation of sugar within the plant provides a kind of feedback for the circadian cycle in plants - a bit like resetting a stopwatch," said study researcher Dr. Mike Haydon, now at the University of York. "We think this might be a way of telling the plant that energy in the form of sugars is available to perform important metabolic tasks. This mirrors research that has previously shown that feeding times can influence the phase of peripheral clocks in animals."