photoperiodism

[foh-tuh-peer-ee-uh-diz-uh m]
noun Biology.
  1. the response, as affecting growth or reproduction, of an organism to the length of exposure to light in a 24-hour period.

Origin of photoperiodism

First recorded in 1915–20; photoperiod + -ism
Also called pho·to·pe·ri·o·dic·i·ty [foh-toh-peer-ee-uh-dis-i-tee] /ˌfoʊ toʊˌpɪər i əˈdɪs ɪ ti/.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

British Dictionary definitions for photoperiodicity

photoperiodism

noun
  1. the response of plants and animals by behaviour, growth, etc, to photoperiods
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for photoperiodicity

photoperiodism

n.

1920, from photoperiod (1920, from photo- + period) + -ism.

Online Etymology Dictionary, © 2010 Douglas Harper

photoperiodicity in Medicine

photoperiodism

[fō′tō-pîrē-ə-dĭz′əm]
n.
  1. The response of an organism to changes in its photoperiod, especially as indicated by vital processes.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

photoperiodicity in Science

photoperiodism

[fō′tō-pîrē-ə-dĭz′əm]
  1. The response of an organism to changes in its photoperiod, especially as indicated by vital processes. For example, many plants exhibit photoperiodism by flowering only after being exposed to a set amount of daylight, as by requiring either a long or short day to flower. Plant growth, seed germination, and fruiting are also affected by day length. Photoperiodic responses in plants are regulated by special pigments known as phytochromes. In animals, migration, mating, amount of sleep, and other behaviors are also photoperiodic. In many animals, photoperiodism is regulated by the hormone melatonin.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.