Circadian clocks affect a large proportion of differentially expressed genes in many organisms. Microarray analyses suggest that ∼10% of all Arabidopsis genes regulated at the level of mRNA abundance and have identified multiple metabolic pathways under circadian control ( Harmer et al., 2000 ; Schaffer et al., 2001 ). The circadian clock is an intricate, even delicate, regulator of plant physiology, yet at least one of the selective pressures that drove its evolution is brutally simple. The nature and functioning of biological clock is … We show that a substantial photosynthetic advantage is conferred by correct matching of the circadian clock period with that … Tissue-specific hierarchies in circadian networks in mammals have been contentiously debated, whereas little attention has been devoted to the concept in plants, owing to technical difficulties. Biological Clock: The plants showing endogenous circadian rhythms have time measuring system or ‘biological clock’ inside their cells which measures the passage of time in much the same way as a pendulum. Circadian control of transcription is widespread (Dunlap, 1999), and the list of plant genes regulated by the circadian clock is extensive. In the last few years, it was determined that responses known to be regulated by the oscillator are also able to modulate clock performance. Like other eukaryotic clocks, plant clocks employ a diverse array of transcriptional and post-transcriptional regulatory mechanisms to establish a robust oscillation that is resilient in the face of environmental fluctuations, yet responsive to … Science 309, 630 –633. Below are several examples outlining these advantages: Runner bean seedlings are seen to change the position of their leaves between night and day.


Circadian clocks are believed to confer an advantage to plants, but the nature of that advantage has been unknown. Plants must be exposed to sunlight for photosynthesis, and sunlight is not available continuously. The plant circadian clock allows organisms to anticipate the predictable changes in the environment by adjusting their developmental and physiological traits. Plant circadian clocks share a common architecture with clocks of all eukaryotes: Interlocked negative feedback loops [1,154]. Plant circadian clocks increase photosynthesis, growth, survival, and competitive advantage.