Transcription factor that binds specifically to a 5'-AA[AG]G-3' consensus core sequence (By similarity). Transcriptional repressor of 'CONSTANS' expression (By similarity). Regulates a photoperiodic flowering response. Expressed in the vasculature of cotyledons and hypocotyls, leaves and roots. Circadian-regulation. The transcript level rises progressively from dawn and decreases during the night.