pho·​tot·​ro·​pism | \ fō-ˈtä-trə-ˌpi-zəm How to pronounce phototropism (audio) \

Definition of phototropism

: a tropism in which light is the orienting stimulus

Examples of phototropism in a Sentence

Recent Examples on the Web The fungus grows toward the hottest and most radioactive places, like phototropism but for deadly toxins. Caroline Delbert, Popular Mechanics, "You Should Know About This Chernobyl Fungus That Eats Radiation," 6 Feb. 2020 The new polymer, described in a paper in the journal Nature Nanotechnology, is capable of phototropism, or the ability to follow the sun in its daily journey across the sky. Jason Daley, Smithsonian, "Tiny, Sunlight-Following Polymer ‘Sunflowers’ Could Boost the Efficiency of Solar Panels," 7 Nov. 2019

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'phototropism.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

First Known Use of phototropism

1899, in the meaning defined above

History and Etymology for phototropism

International Scientific Vocabulary

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Time Traveler for phototropism

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The first known use of phototropism was in 1899

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Cite this Entry

“Phototropism.” Dictionary, Merriam-Webster, Accessed 23 Jan. 2021.

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More Definitions for phototropism


pho·​tot·​ro·​pism | \ fō-ˈtä-trə-ˌpiz-əm How to pronounce phototropism (audio) , ˌfōt-ō-ˈtrō-ˌpiz-əm How to pronounce phototropism (audio) \

Medical Definition of phototropism

: a tropism in which light is the orienting stimulus — see heliotropism
2 : the reversible change in color of a substance produced by the formation of an isomeric modification when exposed to radiant energy (as light)

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