photoperiod(redirected from photoperiodical)
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the period of time per day that an organism is exposed to daylight (or to artificial light). adj., adj photoperiod´ic.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.
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.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.
photoperiodthe length of daylight as compared with the length of darkness in each 24 hour cycle. see PHOTOPERIODISM.
Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005