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A carbohydrate component of plant cell walls; associated with sieve plates where calluses are formed.
Having hardened protuberances, as on the skin or on leaves and stems.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



a polysaccharide, insoluble in water, contained in plants and consisting of glucose-molecule residues joined in a spiral chain (as opposed to cellulose, in which the glucose molecules are joined in a straight chain).

Callose lines the tubules of the sievelike layers of phloem; asthese tubules age, the amount of callose increases and the tubulesbecome plugged and cease functioning. When a plant is injured, callose is deposited on the cell walls of the parenchyma, forminga callus. Callose is also found in the cell walls of some algae andfungi.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
Callose homeostasis at plasmodesmata: molecular regulators and developmental relevance.
AtCslA2 seems to have a membrane topology similar to that of CesA, callose synttase (CalS), and the other members of Csl family.
Microtubule involvement in the deposition of radial fibrilla callose arrays in stomata of the fern Asplenium nidus L.
When wounding of the phloem occurs, the sieve tubes apparently synthesize a polysaccharide called callose, which plugs the sieve plate and reduces the flow.
Japan Science and Technology Corporation (Saitama, Japan), National Institute of Agrobiological Sciences (Ibaraki, Japan), and Forestry and Forest Products Research Institute (Ibaraki, Japan) have patented a method for producing non-cellulosic callose fiber by using plant protoplast, which imposes less burden to the environment with reduced energy consumption compared to conventional natural fibers is provided; it comprises the addition of an inorganic ion to a plant protoplast cultivation system, which leads the plant protoplast to produce non-cellulosic callose fiber.
A reduction in large callose deposits surrounding haustoria of Peronospora parasitica infecting Arabidopsis thaliana was indirectly achieved in transgenic plants not accumulating Salicylic acid (SA) by expression of the enzyme salicylate hydroxylase (Donofrio and Delaney , 2001).
Leaves 2, reduced to tubular sheaths; upper leaf sheath up to 15 cm long, membranous-translucent, loose but not inflated, friable, often splitting adaxially, stramineous to pale grayish brown, apex obtuse to subacute, not callose, tooth-like projection (mucro) absent or very short; lower leaf sheath much shorter than upper, membranous, dark grayish brown to almost black.
Elytra moderately convex, oval-elongate, not denticulate at shoulder, more or less widened posteriorly and more or less strongly callose on preapical declivity, more or less diffusedly pubescent or nearly glabrous, usually rather dull; striae generally fine and feebly or not at all crenulate; interstices flat, rarely convex, more or less distinctly punctured; epipleura strong, elongately bristled at least at two basal thirds.
2002; 2003), changes in cell wall structure (e.g., enhanced lignification, polymer cross-linkage, and callose deposition), disruption of [Ca.sup.2+] homeostasis (Jones et al.
Aluminum resistance is usually assessed in seedling-based assays, either by quantifying root elongation or apical callose concentrations, or by staining root apices with hematoxylin (Kerridge and Kronstad, 1968; Polle et al., 1978; Ruiz-Torres et al., 1992; Llugany et al., 1994; Cancado et al., 1999).
Ultrastructural changes and localization of chitin and callose in compatible and incompatible interactions between carnation callus and Fusarium oxysporum.
After a systematic screening for Al toxicity, Cayenne and Soft Touch were selected, since they showed the most Al-resistant and Al-sensitive characteristics, respectively (through their root-growth response to Al, Al content, and callose accumulation in the root tips).