Circadian light input in plants, flies and mammals

Novartis Found Symp. 2003:253:73-82; discussion 82-8, 102-9, 281-4.


The rotation of our planet results in daily changes in light and darkness, as well as seasons with characteristic photoperiods. Adaptation to these daily and seasonal changes in light properties (and associated changes in the environment) is important to the sustained survival of higher life forms on our planet. Many organisms use their intrinsic circadian oscillator or clock to orchestrate daily rhythms in behaviour and physiology to adapt to diurnal changes. Some higher organisms use the same oscillator to monitor day length in selecting the appropriate season for reproductive behaviour. Organisms have developed irradiance measurement mechanisms to ignore photic noise (lightning, moonlight), and use the light of dusk and dawn for circadian photoentrainment. They have also devised multiple photoreceptors and signalling cascades to buffer against changes in the spectral composition of natural light. The interaction of the clock with ambient light is, therefore, quite intricate.

Publication types

  • Review

MeSH terms

  • Animals
  • Arabidopsis / physiology
  • Arabidopsis / radiation effects
  • Arabidopsis Proteins
  • Circadian Rhythm / physiology*
  • Circadian Rhythm / radiation effects*
  • Cryptochromes
  • Drosophila Proteins*
  • Drosophila melanogaster / physiology
  • Drosophila melanogaster / radiation effects
  • Eye Proteins*
  • Flavoproteins / physiology
  • Flavoproteins / radiation effects
  • Mammals
  • Mice
  • Models, Biological
  • Photobiology
  • Photoreceptor Cells, Invertebrate / physiology
  • Photoreceptor Cells, Invertebrate / radiation effects
  • Photoreceptor Cells, Vertebrate / physiology
  • Photoreceptor Cells, Vertebrate / radiation effects
  • Photosynthetic Reaction Center Complex Proteins / physiology
  • Photosynthetic Reaction Center Complex Proteins / radiation effects
  • Receptors, G-Protein-Coupled
  • Seasons
  • Signal Transduction
  • Suprachiasmatic Nucleus / physiology
  • Suprachiasmatic Nucleus / radiation effects


  • Arabidopsis Proteins
  • CRY1 protein, Arabidopsis
  • Cryptochromes
  • Drosophila Proteins
  • Eye Proteins
  • Flavoproteins
  • Photosynthetic Reaction Center Complex Proteins
  • Receptors, G-Protein-Coupled
  • cry protein, Drosophila