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phototonus

[foh-tot-n-uh s] /foʊˈtɒt n əs/
noun, Biology
1.
the normal condition of sensitiveness to light in organisms or their organs.
2.
the irritability exhibited by cytoplasm when exposed to light of a certain intensity.
Origin
1870-1875
1870-75; photo- + tonus
Related forms
phototonic
[foh-tuh-ton-ik] /ˌfoʊ təˈtɒn ɪk/ (Show IPA),
adjective
Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
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British Dictionary definitions for photo tonus

phototonus

/fəʊˈtɒtənəs/
noun
1.
the condition of plants that enables them to respond to the stimulus of light
Derived Forms
phototonic (ˌfəʊtəʊˈtɒnɪk) adjective
Word Origin
C19: from photo- + Greek tonostone
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
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photo tonus in Medicine

phototonus pho·tot·o·nus (fō-tŏt'n-əs)
n.
The state of being sensitive to or irritated by light.


pho'to·ton'ic (fō'tə-tŏn'ĭk) adj.
The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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