Pericycle


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Related to Pericycle: xylem, Medullary rays

pericycle

[′per·ə‚sī·kəl]
(botany)
The outer boundary of the stele of plants; may not be present as a distinct layer of cells.
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 It might be outdated or ideologically biased.

Pericycle

 

(also pericambium), formative tissue in the roots and the stems of plants, located around the vascular cylinder. The pericycle is represented by one or more (in gymnosperms) layers of parenchymatous cells of the meristem, which are separated from the cells of the primary cortex by the endodermis. All lateral roots develop from the pericycle of the main root. In dicotyledonous plants, action of the pericyclic cells causes the cambial cells to join in a common cylinder in the roots of secondary growth. The pericycle forms broad rays in the root, in whose parenchyma metabolic products are deposited and new adventitious roots and, sometimes, root buds are formed. When the root thickens and the primary cortex atrophies, the phellogen is differentiated in the pericycle, forming the periderm on the surface of the root.

Pericycle in the stems of plants gives rise to both sclerenchyma and parenchyma (some lianas of the families Aristolochiaceae, Cucurbitaceae, and Solanaceae) or to only sclerenchyma (in monocotyledons). In many species of Compositae (viper’s grass, dandelion), segmented latex vessels are formed in the pericycle. In Umbelliferae, essential-oil passages are formed, and in Cucurbitaceae secretory cells. In some plants of the families Liliaceae, Chenopodiaceae, and Caryophyllaceae, secondary thickening of stems and roots occurs owing to the formation from the pericycle of new layers of cambial zones and vascular bundles to the periphery of the vascular cylinder. The thickening is associated with the formative function of pericyclic cells. This type of secondary thickening of axial organs of a plant is usually called anomalous growth.

I. S. MIKHAILOVSKAIA

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
Epidermis (Ep), hypodermis (Hi), exodermis (Ex), cortex (Co), endoderm (En), aerenchyma (Ae), metaxylem (MX), protoxylem (PX) phloem (Ph), pericycle (Pe) and parenchymatic marrow (Ma).
sativa roots were inhibited strongly, transverse growth was maintained regularly and was from outside to inside: root hairs, epidermis, cortex parenchyma, endodermis, pericycle, tissue conductors and parenchyma medulla.
Surrounding this region is a single layer of cells called the pericycle. Directly outside the pericycle is a single layer of cells called the endodermis.
Research in other plants has led to the identification of genes involved in the development of root cap, pericycle, lateral roots, epidermis, cortex, elongation zone, and root apical meristem (Rost and Bryant, 1996).
Hyoscyamine 6[Beta]-hydrolase, an enzyme involved in tropane alkaloid biosynthesis, is localized at the pericycle of the root.
This is evidence that the process involved in pericycle cell division during the formation of lateral roots also occurs in callus formation.
They are called root-knot nematodes, because the resulting giant cells become multinucleate (up to greater than 100 nuclei) and are surrounded by cortical and pericycle cells that divide and proliferate resulting in the development of 'galls' or 'root knots' (Gheysen and Mitchum, 2011).
In the cortical fundamental meristem, a pro-endodermis is distinguishable, and pericycle and procambium cylinder are also evident in the primary root apex (Figure 2B).
In Ceiba pentanda and Ceiba speciosa stem, the pericycle is marked by strands of fibers situated at the outer periphery of the phloem groups, phloem strands usually stratified into fibrous and non fibrous zones where primary medullary rays present between them in triangular shape with inward apex whereas the phloem in Bombax ceiba forms a continuous ring.