How plants tell time of day

Washington: Researchers studying how plants are able to set and maintain this internal clock have found that they use sugars to tell the time of day. Plants, like animals, have a 24 hour `body-clock` known as the circadian rhythm. This biological timer gives plants an innate ability to measure time, even when there is no light. Plants produce sugar via photosynthesis; it is their way of converting the sun`s energy into a usable chemical form needed for growth and function. Scientists from the University of Cambridge Department of Plant Sciences showed that these sugars also play a role in circadian rhythms. Researchers studied the effects of these sugars by monitoring seedlings in CO2-free air, to inhibit photosynthesis, and by growing genetically altered plants and monitoring their biology. The production of sugars was found to regulate key genes responsible for the 24 hour rhythm. Dr Alex Webb, lead researcher at the University of Cambridge, said that the research showed 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. The research shows that photosynthesis has a profound effect on setting and maintaining robust circadian rhythm s in Arabidopsis plants, demonstrating a critical role for metabolism in regulation of the circadian clock. Dr Mike Haydon, who performed much of the research and is now at the University of York, added that the accumulation of sugar within the plant provides a kind of feedback for the circadian cycle in plants- a bit like resetting a stopwatch. Haydon said that he thinks this might be a way of telling the plant that energy in the form of sugars is available to perform important metabolic tasks. The study is published in journal Nature.