photoperiodn.
/ˈfəʊtəʊˌpɪərɪəd/, U.S. /ˈfoʊdoʊˌpɪriəd/ Biology.
The period of daily illumination which an organism receives; (also) the length of light exposure which is most effective in stimulating a particular physiological process, such as reproduction, in a plant or other organism.
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the world > life > biology > biological processes > light-related processes > [noun] > photoregulation > period of exposure to daylight
day length1920
photoperiod1920
1920 W. W. Garner & H. A. Allard in Jrnl. Agric. Res. 18 603 The term photoperiod is suggested to designate the favorable length of day for each organism, and photoperiodism is suggested to designate the response of the organism to the relative length of day and night.
1937 Ann. Reg. 1936 58 The photoperiod of a plant can be modified by temperature.
1957 New Biol. 23 10 The profound importance which the daily photoperiod may have in controlling the time of transition from vegetative growth to flowering was discovered more than forty years ago.
1976 Nature 1 Jan. 41/1 The fish were maintained in aquaria at 22–24°C, on a light–dark (LD) 12:12 photoperiod.
2001 B. Dibra & E. Randolph CatSpeak vi. 107 All cats shed continuously in a natural cycle of hair replacement that has to do with both the photoperiod and environmental temperature.
This entry has been updated (OED Third Edition, March 2006; most recently modified version published online March 2022).
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n.1920