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The daily duration of light and dark to which an organism is exposed, considered especially with regard to its effect on growth and development.

pho′to·pe′ri·od′ic (-ŏd′ĭk) adj.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.


(Botany) the period of daylight in every 24 hours, esp in relation to its effects on plants and animals
ˌphotoˌperiˈodic adj
ˌphotoˌperiˈodically adv
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014


(ˌfoʊ təˈpɪər i əd)

the interval in a 24-hour period during which an organism is exposed to light.
pho`to•pe`ri•od′ic (-ˈɒd ɪk) adj.
pho`to•pe`ri•od′i•cal•ly, adv.
Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.
References in periodicals archive ?
The SD photoperiod treatments reduced the yield components and yield, but not affected significantly the yield components and yield under SD-12 h treatment compared with SD-8 h treatment.
edulis broodstock may be improved by manipulating several external factors such as temperature, food supply, and photoperiod; however, few studies have reported the effect of these parameters on 0.
It is a known matter that fish life activities are influenced by seasonality, particularly in temperate and cold climates where the photoperiod range changes along the year are greater and has a relevant influence on fish biology (Pankhurst and Porter, 2003).
The aeration was constant, and the photoperiod was 12 h of light and 12 h of darkness (12L: 12D), controlled by a Fox lux digital timer.
The growth progress of cashmere in goats is affected by photoperiod, nutrition, management, and environmental and genetic factors [2-6].
Maturation can be controlled by multiple techniques like monosex culture (Devlin and Nagahama, 2001) and manipulation of temperature and photoperiod (Choi et al., 2010; Miguad et al., 2010; Leclercq et al., 2011).
This indolamine, unlike melatonin, is photoperiod dependent and oscillates in the daytime, whereas its levels in blood are inversely proportional at nighttime (1).
The seeds were kept in coveredPetri dishes, sealed with Parafilm[R] (BRAND, Germany) in order to reduce moisture loss, and stored in a Biochemical Oxigen Demand (BOD) type germinator at 25[degrees]C with a 12-hour photoperiod of daily light and simulating the conditions of germination; and in the absence of a light simulating environment under soil cover, under no-tillage conservation management conditions, for fourteen days.
We then grew these populations under differing photoperiod conditions, as it has previously been shown that DNA demethylation via 5-azaC can impact flowering under differing light conditions [31].
Outside of the tropics (where day length remains relatively consistent throughout the year), the changing photoperiod is a reliable and predictable seasonal signal that presents an opportunity for organisms to adapt to seasonal changes in factors such as temperature and resource availability in an anticipatory fashion.