- the normal condition of sensitiveness to light in organisms or their organs.
- the irritability exhibited by cytoplasm when exposed to light of a certain intensity.
Origin of phototonus
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
- the condition of plants that enables them to respond to the stimulus of light
C19: from photo- + Greek tonos tone
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
- The state of being sensitive to or irritated by light.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.