Schematic diagrams for circadian oscillator with light adaptation.

Three kinds of light induction were theoretically considered that are up-regulation of transcription by light in the form of light adaptation (A), slow response, and no adaptation (B). In the case of light adaptation, the up-regulated transcription rate remains at a maximal value, Xmax for a certain period with duration Ts. Subsequently, the transcription rate decreases over a decay time, Td, and reaches to the basal transcription rate under dark (A). In the case of slow response, the up-regulated transcription rate increases over a period Tr and reaches to the maximum (B).