Figure 2.

Measurement of circadian-controlled bioluminescence under a light–dark cycle and free-running conditions. A chimeric construct consisting of the clock-controlled cab2 promoter and the firefly LUC reporter is shown (Millar et al., 1995). The rhythm of bioluminescence is measured in relative luminescence units. Period, amplitude, and phase, peaking during the day, are indicated with arrows. Plants were grown in a LD cycle and then released under constant light (LL) and temperature. LD0 indicates the start of the day and LD12 the beginning of the night. Under constant light (LL), subjective days (white bars) and nights (gray bars) are highlighted. Hours indicate how long the plant has been kept under LL.