pho·​tot·​ro·​pism fō-ˈtä-trə-ˌpi-zəm How to pronounce phototropism (audio)
: a tropism in which light is the orienting stimulus

Examples of phototropism in a Sentence

Recent Examples on the Web That 50-50 split makes more sense than Gagliano’s result, says Mannie Liscum, a University of Missouri expert on plant phototropism — the way plants grow toward light. Anna Funk, Discover Magazine, 28 Aug. 2019 The reason for their odd behavior is likely something common to all plants: phototropism. Nathaniel Scharping, Discover Magazine, 6 June 2017 If the tree has grown at a slant all its life, it’s probably because of phototropism, Brosius says. Samantha Chery, Washington Post, 2 Aug. 2022 The leaning effect could be a result of phototropism, where plants naturally position themselves toward sunlight. Samantha Chery, Washington Post, 2 Aug. 2022 The fungus grows toward the hottest and most radioactive places, like phototropism but for deadly toxins. Caroline Delbert, Popular Mechanics, 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, 7 Nov. 2019 See More

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'phototropism.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History


International Scientific Vocabulary

First Known Use

1899, in the meaning defined above

Time Traveler
The first known use of phototropism was in 1899

Dictionary Entries Near phototropism

Cite this Entry

“Phototropism.” Dictionary, Merriam-Webster, Accessed 1 Oct. 2023.

Kids Definition


pho·​tot·​ro·​pism fō-ˈtä-trə-ˌpiz-əm How to pronounce phototropism (audio)
: a movement or growing in a particular direction that is made by a living thing in response to light

Medical Definition


: a tropism in which light is the orienting stimulus see heliotropism
: 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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