| Tick Tock:Plant Clocks |
| Friday, 30 September 2005 | |
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The circadian clock that governs key biochemical activities within plant cells enables plants to optimize their rates of photosynthesis and metabolism, according to research from the Department of Plant Sciences. Plants possess an internal molecular clock which ensures that various physiological processes, such as stomatal opening, are cyclic, with a period of approximately one day-night cycle.This particular length of cycle was expected to hold a selective advantage on the basis that it would be optimal for plant metabolism. Researchers at the University of Cambridge decided to directly test this concept using plants with mutations in genes controlling periodicity. By growing wild-type, ‘long-period’ and ‘short-period’ mutants of the cress Arabidopsis thaliana under light-dark cycles of varying length, they measured the impact of periodicity on plant fitness. Fitness was assessed using indicators such as chlorophyll concentration, photosynthetic rate and degree of biomass accumulation. It was found that plants thrived best when the intrinsic biological rhythm of the plant matched that of the external light-dark cycle, a condition known as circadian resonance. The fitness benefits of circadian resonance were also evident in competition experiments, in which ‘long-period’ mutants out-competed ‘short-period’ mutants under long lightdark cycles and vice versa. The molecular pathways through which the circadian clock controls the processes in question have yet to be elucidated. Further research in this area is likely to provide insights into ways of maximising crop yield and of increasing productivity in situations where lightdark cycles may vary.WD Further information can be found in Dodd et al., Science. 309: 630-633 (2005) |
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