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A ground tissue of plants chiefly concerned with the manufacture and storage of food. The primary functions of plants, such as photosynthesis, assimilation, respiration, storage, secretion, and excretion—those associated with living protoplasm—proceed mainly in parenchymal cells. Parenchyma is frequently found as a homogeneous tissue in stems, roots, leaves, and flower parts. Other tissues, such as sclerenchyma, xylem, and phloem, seem to be embedded in a matrix of parenchyma; hence the use of the term ground tissue with regard to parenchyma is derived. The parenchymal cell is one of the most frequently occurring cell types in the plant kingdom. See Plant anatomy, Plant physiology

Typical parenchyma occurs in pith and cortex of roots and stems as a relatively undifferentiated tissue composed of polyhedral cells that may be more or less compactly arranged and show little variation in size or shape. The mesophyll, that is, the tissue located between the upper and lower epidermis of leaves, is a specially differentiated parenchyma called chlorenchyma because its cells contain chlorophyll in distinct chloroplastids.

This chlorenchymatous tissue is the major locus of photosynthetic activity and consequently is one of the more important variants of parenchyma. Specialized secretory parenchymal cells are found lining resin ducts and other secretory structures. See Photosynthesis, Secretory structures (plant)

McGraw-Hill Concise Encyclopedia of Bioscience. © 2002 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



(1) The fundamental tissue in plants. Parenchyma is composed of cells having a polyhedral shape, with the various diameters differing very little from each other. The cells form homogeneous aggregates in the plant body and fill the spaces between other tissues. They serve as part of the conductive and mechanical tissues. As a result of functional specialization of protoplasts, parenchyma cells may perform assimilative, excretive, and other functions. The presence of intercellular substances, especially in diffuse parenchyma with vacuoles, determines the tissue’s role in gas exchange. Parenchyma cells serving support functions may be elongated, branched, or stellate; their walls are thick and often lignified. Living parenchyma cells are capable of division. Phellogen (cork cambium) or, in unusually thick plants, cambium is formed (for example, in beets and certain lianas).

(2) In animals, parenchyma is the phylogenetic precursor of true tissue. It is divided into primary parenchyma and mixed parenchyma. The former is a bond of homogeneous cells without systematic organization. The cells are not fused in a syncytium or separated by interstitial matter (as in the embryos of certain hydroids in the morular stage). Mixed parenchyma is an aggregate of heterogeneous cells distributed randomly, as in the bodies of Acoela. At times, the term “parenchyma” is used to designate the principal functional tissue of the liver, spleen, lungs, and glands. It is also used to designate striated muscle tissue.

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


A tissue of higher plants consisting of living cells with thin walls that are agents of photosynthesis and storage; abundant in leaves, roots, and the pulp of fruit, and found also in leaves and stems.
The specialized epithelial portion of an organ, as contrasted with the supporting connective tissue and nutritive framework.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
Since the CT lung image has various shapeless image boundaries, either the pixels which are present outside of the lung parenchymal region or the parenchymal boundaries were considered, to overcome the missing of nerves present in the lung parenchymal boundary.
Parenchymal phase signal intensity ratio = (Post-contrast [SI.sub.parenchymal] - Pre-contrast SI)/Post-contrast [SI.sub.parenchymal] x 100
Furthermore, the relationship between right kidney width (RKW)-NW (r=0.382, p<0.0001) and right kidney parenchymal thickness-NW (r=0.241, p<0.0001) was also statistically significant.
Diffuse parenchymal abnormalities include acute tubular necrosis, hyperacute rejection, acute rejection, chronic rejection, and drug-induced nephrotoxicity.
Renal parenchymal changes secondary to systemic diseases, such as DM and HT, increase renal cortex echogenicity, and this finding may provide us with an idea of renal functional impairment (20).
We also found that pyramidal signs were the most common neurological findings in parenchymal NBD, which is in agreement with previous studies (4, 8, 11-13, 29-31).
This highlights many important unanswered questions, that include: What is the strength of the association between pulmonary TB and PHT, across the spectrum of parenchymal abnormality in TB patients?
Normal distribution was not found for parenchymal values among diagnostic types (Shapiro-Wilk test, p<0.05); thus, the Kruskal-Wallis H test was conducted.
(A) Head ultrasound of a 23-week fetus with CTX showing lateral ventriculomegaly (bidirectional arrow), as well as periventricular and scattered parenchymal brain echogenic foci representing calcification (arrows); (B) axial abdominal ultrasound of the same fetus demonstrating hepatomegaly and intrahepatic hyperechogenicities (arrows); (C) axial abdominal ultrasound of a 25-week fetus showing multiple echogenic foci on the peritoneal surface representing areas of calcification; (D) an enlarged placenta containing hypoechogenic areas (asterisk) representing placental infarct and intervillous thrombi.
International data also supports the high utility of TBLB (6-10 bites/specimens) in the evaluation of diffuse parenchymal lung disease particularly in lymphangitis carcinomatosis, chronic eosinophilic pneumonia, sarcoidosis, rejection after lung transplantation, hypersensitivity pneumonitis and mycobacterial and invasive fungal infection6.
AIN is an inflammatory disease of renal parenchymal cells involving the tubules and interstitial regions of the kidney.