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phototropism

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phototropism

 [fo-tot´ro-pizm]
1. tropism of an organism in response to light; it may be either positive (toward the light) or negative (away from the light).
2. change of color produced in a substance by the action of light. adj., adj phototrop´ic.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

pho·tot·ro·pism

(fō-tot'rō-pizm),
Movement of a part of an organism toward (positive phototropism) or away from (negative phototropism) the stimulus of light. Compare: phototaxis.
[photo- + G. tropē, a turning]
Farlex Partner Medical Dictionary © Farlex 2012

phototropism

(fō-tŏt′rə-pĭz′əm, fō′tō-trō′-)
n.
Growth or movement of a sessile organism toward or away from a source of light.

pho′to·tro′pic (fō′tə-trō′pĭk) adj.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.

pho·tot·ro·pism

(fō-tot'rŏ-pizm)
Movement of a part of an organism toward (positive phototropism) or away from (negative phototropism) the stimulus of light.
Compare: phototaxis
[photo- + G. tropē, a turning]
Medical Dictionary for the Health Professions and Nursing © Farlex 2012

phototropism

a bending growth movement of parts of a plant in response to a light stimulus. The movement produced by unequal growth is due to differences in AUXIN concentration. For example, most seedlings are positively phototropic, growing towards a light stimulus, because there is a greater concentration of auxin on the side furthest away from the light, giving greater growth on this side. Roots, on the other hand, are often negatively phototropic, growing away from a light source.
Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005

phototropism 

Reaction of certain plants and animals to move towards (positive phototropism) or away from (negative phototropism) a source of light.
Millodot: Dictionary of Optometry and Visual Science, 7th edition. © 2009 Butterworth-Heinemann
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References in periodicals archive
Botanically speaking, roots are phototropic and geotropic or, in other words, they naturally grow away from the light, vertically downwards.
What's more, edible landscaping doesn't require a move to the country or a phototropic sleep pattern.
Sunflowers are easy to grow, though it's important to remember they are phototropic plants that will twist around until they face the direction from which sunlight is strongest.
Terrariums receiving light predominately from one direction should be rotated to prevent phototropic curving toward the light.
Cragg & Crisp (1991) analyzed the results obtained by other authors and suggested that pectinid settlement is positively geotactic and negatively phototropic.
Yet if this were so, it would seem to require imputing the same grasp to phototropic plants and barometers.
Bergey's Manual of Systematic Bacteriology, 2nd Edition, Volume 1: The Archaea and the Deeply Branching and Phototropic Bacteria George Garrity, ed.
* The sunflower is phototropic when the plant is in the bud stage, meaning that it tends to follow the movement of the sun from east in the morning to west in the afternoon.
Unique Characteristics: Gives characteristics that are unique to the material, such as fragrance, airdrying capabilities, distinctive form, geotropic or phototropic properties, and toxicity.
Leaf phototropic movements, such as those of young sunflower leaves which tend to maintain a position nearly perpendicular to the beam of the sun, further increase these difficulties, particularly where upper leaves or sparse canopies are involved.
Thus, the results imply that the phototropic mechanisms underlying crown orientation are differentially responsive to direct and diffuse components of the radiation environment.
Like most biological organisms, humans are phototropic: they grow toward the light.
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