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the condition of a body or system in which it has opposing physical properties at different points, esp magnetic poles or electric charge
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



the specific orientation of processes and structures in space, which is inherent in organisms and leads to the appearance of morphological and physiological differences at opposite ends or on opposite sides of cells, tissues, organs, and the organism as a whole. Polarity is manifested with particular clarity in plants. Even the multicellular strands of green algae and the hyphae of fungi are marked by polarity: their constituent cells are oriented in one direction. Polarity arises in the spores of algae, fungi, mosses, horsetails, and ferns only after an appropriate external stimulus. The cells begin to break down, giving rise to a new organism oriented in a certain plane. In seed plants, polarity is displayed even in the zygote and developing seed, where two rudimentary organs form, namely, the leaf bud and the root. In a developing plant organism, polarity appears in the predominant direction of cell divisions, growth, and differentiation. The polarization and differentiation of each cell depend on the position the cell occupies with respect to other cells.

The leading role in the polarization of cells and tissues and in the orientation of organs in space belongs to plant hormones. Thus, the implantation of a lilac bud in an undifferentiated callus tissue causes the polar formation of xylem strands. The addition of auxins to the implantation zone sharply increases the polarity. The growth of aboveground parts is activated in stem grafts by the action of gibberellins, and the establishment and growth of roots are promoted by auxins. The polarity of organs already formed generally is preserved even when their normal position is sharply disrupted (experiments on the inversion of grafts). However, in some cases it is possible to disrupt the polarity by altering ambient conditions (light, heat, moisture, chemicals). This changes the gradient of hormonal and trophic processes, which in turn determine the polarization of morphological and physiological structures.

In animals, polarity is observed both in cells and in the entire organism. In epithelial cells a distinction is made between the basal and distal parts, with a characteristic disposition of individual structures, such as the nucleus, the Golgi apparatus, and secretory granules. In nerve cells, polarity is expressed by the location of the axon and dendrites. In Protozoa, polarity is manifested in the location of organoids along the anteroposterior or dorsoventral axis. Polarity sometimes is present in an egg cell before fertilization, but it more commonly arises as a result of the penetration by a spermatozoid. The presence of physiological polarity has been established in hydrozoan polyps and worms. This enabled the British scientist C. Child to formulate the theory of physiological gradients—the variation of physiological activity and sensitivity to damaging factors along the longitudinal axis. Polarity effects also are observed during vegetative multiplication and regeneration. It has been possible in experiment to observe polarity distortion. For example, in the axolotl, transplantation of a section of an extremity may result in the formation of digits not only at the distal end of the transplanted stump but also at the proximal end.


Krenke, N. P. “Poliarnost u rastenii.” Izv. An SSSR Seriia biologiches-kaia, 1940, no. 3.
Sinnot, E. Morfogenez rastenii. Moscow, 1963. (Translated from English.)
Molotkovskii, G. Kh. Poliarnost’ razvitiia i fiziologicheskaia genetika rastenii. Chernovtsy, 1968.
Leopold, A. Rost i razvitie rastenii. Moscow, 1968. (Translated from English.)
Child, C. “Physiological Dominance and Physiological Isolation in Development and Reconstitution.” Wilhelm Roux’ Archiv Entwick-lungsmechanik der Organismen, 1929, vol. 117.




a characteristic of chemical bonds that shows the redistribution of electron density in the space near the nuclei compared to the initial density distribution in the neutral atoms forming a given bond.

The “effective charges” of the atoms are a quantitative measure of the polarity of chemical bonds; an effective charge is the difference between the electron charge concentrated in a certain region of space (of the order of atomic dimensions) near the nucleus and the nuclear charge. It is an approximate measure, since it is definitely impossible to single out regions in the molecule that relate to individual atoms and individual bonds (if there are several).

Bonds are highly nonpolar only in diatomic homonuclear molecules; in all other cases they are polar to a certain degree. Covalent bonds are usually slightly polar, whereas ionic bonds exhibit strong polarity. The polarity of chemical bonds is sometimes indicated by symbols of atomic charges (for example, H—Cl, where δ is a certain part of the elementary charge).

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.


The direction in which a direct current flows, in a teletypewriter system.
The sense of the potential of a portion of a television picture signal representing a dark area of a scene relative to the potential of a portion of the signal representing a light area.
Property of a line segment whose two ends are distinguishable.
(cell and molecular biology)
The orientation of a strand of polynucleotide with respect to its partner, expressed in terms of nucleotide linkages.
Property of a physical system which has two points with different (usually opposite) characteristics, such as one which has opposite charges or electric potentials, or opposite magnetic poles.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.


(1) The direction of charged particles, which may determine the binary status of a bit.

(2) In micrographics, the change in the light to dark relationship of an image when copies are made. Positive polarity is dark characters on a light background; negative polarity is light characters on a dark background.
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References in periodicals archive ?
Disruption of planar cell polarity signaling results in congenital heart defects and cardiomyopathy attributable to early cardiomyocyte disorganization.
Margolis, "Tight junctions and cell polarity," Annual Review of Cell and Developmental Biology, vol.
(2009) Helicobacter pylori usurps cell polarity to turn the cell surface into a replicative niche.
Duhon et al., "Mutations in planar cell polarity gene SCRIB are associated with spina bifida," PLoS ONE, vol.
Deregulation of scribble promotes mammary tumorigenesis and reveals a role for cell polarity in carcinoma.
The roots of wholeness involve the quantum dynamics of the resonant polarities in water that allow tissues and organs to be properly organized at the cell polarity leve1.
Before the first cellular division, but after the polarity-determination window, the first indication of cell polarity is migration of the nucleus down (with respect to gravity) along the proximal face of the spore (Edwards and Roux, 1994).
The research team led by Stowers Institute for Medical Research investigator Linheng Li, Ph.D., reports that Flamingo and Frizzled 8, best known for their role in establishing cell polarity, are crucial for maintaining a quiescent reserve pool of hematopoietic stem cells in mouse bone marrow.
Human and commensal cell polarity deficits are the prime force behind these ecosystem disruptions.
More recent work has shown very elegantly that perhaps even more significant than increased proliferation of tubular cells in the course of cyst formation is the deregulated planar cell polarity, thereby upsetting the normal cell division and tubule lengthening, leading instead to cystic dilatation.
In principle statolith sedimentation might be transduced into a new alignment of cell polarity in two ways.