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phototonus

American  
[foh-tot-n-uhs] / 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.

phototonus British  
/ ˌfəʊtəʊˈtɒnɪk, fəʊˈtɒtənəs /

noun

  1. the condition of plants that enables them to respond to the stimulus of light

"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

Other Word Forms

  • phototonic adjective

Etymology

Origin of phototonus

First recorded in 1870–75; photo- + tonus

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.