Definition of photic in US English:



  • 1Relating to light, especially as an agent of chemical change or physiological response.

    • ‘They are therefore true deep-brain photoreceptors that bypass the eyes as a pathway for photic information.’
    • ‘Complementing the large compound eyes, locusts have three much smaller simple eyes or ocelli characterized by rapid signal transmission and high photic sensitivity but very poor spatial resolution.’
    • ‘Furthermore, extraretinal photoreceptors appear to be involved in the photic entrainment of the circadian clock.’
    • ‘Exhibiting uncharacteristic panache, John used this result to question Jacques Loeb's then popular theory of photic orientation in insects, which required paired eyes.’
    • ‘The implications of this work on thought about evolution of photic behavior in fireflies are considered.’
    • ‘To characterize this photic entrainment we examined frq expression in constant light, under which condition the mRNA and protein of this clock gene were strongly induced.’
    1. 1.1Ecology Denoting the layers of the ocean reached by sufficient sunlight to allow plant growth.
      ‘an average depth for the photic zone is about 300 feet’
      • ‘Macroalgae benefit from this relationship because fertile drift plants are retained in the photic zone where they continue to contribute to the gene pool.’
      • ‘The relatively moderate brachiopod generic diversity is consistent with a moderately restrictive environment, including one below the photic zone.’
      • ‘Stromatolites were built by photosynthesizing organisms occupying shallow-water environments within the photic zone.’
      • ‘The authors skimmed their bacteria samples from the top, or photic layer, of the Mediterranean and Red Seas.’
      • ‘Seasonal highs that pushed this euxinic layer into the photic zone would then lead to the greatly increased preservation and the TOC maxima.’