Graph of bioluminescent timeseries data, showing 24-hour biological rhythms (circadian rhythms) in plants of the laboratory model species Arabidopsis thaliana. The data show the intensity of light that was measured in images that included these four transgenic seedlings, amongst many others. The faint bioluminescent signals were created by an enzyme, firefly luciferase, which was produced by a reporter gene in the plant's genome. Seedlings 61 and 62 carried a reporter for transcription of the circadian clock gene CCA1 (red and blue lines, reporter CCA1:LUC+). Seedlings 64 and 65 carried a reporter for gene TOC1 (pale grey and teal lines, reporter TOC1:LUC+). The plants were in darkness at times 12-24h, 36-48h, 60-72h and 84-96h, and otherwise in constant light except when the images were acquired. The signal from CCA1 t after lights-on (after 48h, 72h, etc), or before lights-off for TOC1 (before 36h, 60h, etc). Plants and camera were housed in a temperature-controlled growth chamber, in a research darkroom in the Daniel Rutherford Building, School of Biological Sciences, University of Edinburgh. The experiment was conducted by Adrian Thomson in Andrew Millar's research group, starting on 25 June 2007. The raw data are publicly available under CC-BY license from the BioDare2 repository as part of experiment AT0091, with BioDare2 ID 12730563219125, https://biodare2.ed.ac.uk/experiment/12730563219125.