Definitions

from The American Heritage® Dictionary of the English Language, 4th Edition

  • n. Growth or orientation of a sessile organism, especially a plant, toward or away from the light of the sun.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. The property of some plants of turning under the influence of light; either positively (towards the light) or negatively (away from the light)

from the GNU version of the Collaborative International Dictionary of English

  • n. The phenomenon of turning toward the light, seen in many leaves and flowers.

from The Century Dictionary and Cyclopedia

  • n. In botany, the tendency of growing organs to bend toward or in some cases away from the light, due in the former case to the retarding influence exerted by the light upon their growth on the side of the highest illumination.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • n. an orienting response to the sun

Etymologies

helio- +‎ tropism (Wiktionary)

Examples

  • Besides the algae in their skin, they had altered hormone levels with predispositions toward heliotropism and nudity, plus numerous other "improvements."

    Asimov's Science Fiction

  • His very geographical situation was sufficient to turn the mind towards him, but the particular reason for that heliotropism on the part of his feminine neighbors was that he was an easy man for a woman to ask.

    The Wrong Woman

  • Since plants possess no nerves, this identity of animal with plant heliotropism can offer but one inference -- these heliotropic effects must depend upon conditions which are common to both animals and plants.

    Introduction to the Science of Sociology

  • I tiptoed religiously by it, went on up to the big house where the three women slept, as if drawn to their abode by a sort of heliotropism.

    Tramping on Life

  • They give the quintessence of laboratory experiments as to what are the effects of different energies such as light (heliotropism), electricity (galvanotropism), gravity (geotropism), etc., in their reaction and influence upon the movements and actions of living organisms.

    Manhood of Humanity.

  • Are we to suppose that the upper half of the body or eye had a positive heliotropism and the lower half a negative heliotropism?

    Hormones and Heredity

  • The sensitiveness belonging to living substance, known by the names heliotropism, chemotropism, etc., is like a sketch of sensation and of the reactions following it; organic memory is the basis and the obliterated form of conscious memory.

    Essai sur l'imagination créatrice. English

  • Vienna (who has lately published a great book on heliotropism) finds that an intermittent light, say of 20 minutes, produces the same effect as a continuous light of, say 60 m.

    More Letters of Charles Darwin — Volume 2

  • Wiesner's papers on heliotropism are in the "Denkschriften" of the Vienna Academy, Volumes

    More Letters of Charles Darwin — Volume 2

  • And, yes, many sunflowers do follow the sun in the bud stage, with the young blooms turning east to west daily in a process called heliotropism.

    Evansville Courier & Press Stories

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