The circadian clock is a time-keeping mechanism to support and give organisms to prepare the metabolic and physiological processes with daily cycles of light and dark.These daily information processes also determine proper flowering time by recognizing the day-length in higher plants.In order to facilitate to isolate putative clock components,we isolated mutants of the circadian clock by screening early flowering phenotypes.One of these mutants,fiona1 exhibited extremely early flowering both in long day and short day.