photoperiod(redirected from photoperiodical)
Also found in: Medical.
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
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014
pho•to•pe•ri•od(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.
Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.