Parenchyma

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Parenchyma

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)

Parenchyma

 

(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.

parenchyma

[pə′reŋ·kə·mə]
(botany)
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.
(histology)
The specialized epithelial portion of an organ, as contrasted with the supporting connective tissue and nutritive framework.
References in periodicals archive ?
Chlorenchyma (C)###0516-2###One to three layers of irregularly arranged parenchymatous cells containing chloroplasts, which was###Fig.
part of the parenchymatous bundle sheath or the outer layer of the
Fritschiella, a terrestrial green alga (sometimes found on tree bark), with a growth form varying from filamentous to parenchymatous, has also been postulated as a land-plant progenitor (Cronquist, 1961).
Distinguishing features: Polyxylic stem with a persistent armor of leaf bases [ILLUSTRATION FOR FIGURES 3B & 4D OMITTED] and a parenchymatous pith with anastomosing collateral bundles and mucilage channels.
Epicotyl consists of a uniseriate and hairy epidermis, and collenchymatous and parenchymatous cortex, without typical endodermis.
These results may be triggered by decreases in the radial volume of parenchymatous cells, and reductions in the amount of sclerenchyma fibers in sugarcane (Martins & Castro, 1999).
The histological manifestations include parenchymatous necrosis, small vessel vasculitis and granulomatous inflammation not vernix (2).
Stages of neurosyphilis Stage Symptoms Asymptomatic None Symptomatic Early Meningeal Meningovascular Late Gummatous Cerebral Spinal compression Parenchymatous General paresis Tabes dorsalis Optic atrophy Table 2.
The excessive use of chemical-containing drugs leads to the formation of a large number of resistant strains of microorganisms that significantly reduces the therapeutic effect of the antimicrobial agents as well as promotes the manifestation of toxic and allergic reactions in humans and animals, which are accompanied by severe lesions of the parenchymatous organs and the nervous system.
Vascular bundles contain of bundle sheath one layered, thin walled and without chloroplast parenchymatous cells.
However, in palmipeds, the liver is where most fat is formed, being very sensible to fat degeneration, consisting in an abnormal fat reserve in the cytoplasm of parenchymatous cells.