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.

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

References in periodicals archive ?
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.
The vascular bundle is surrounded externally by the monostratified endodermis with thickening on the radial walls and a pericycle consisting of (1-)2-3 cell layers surrounding the phloem and xylem (Fig.
In the central cylinder of all of the species, the uniseriate pericycle with cells with fine walls, come with variations in the size and cellular form, in Polygonum ferrugineum (Figure 3D), P.
Meristematic activity of the endodermis and the pericycle in the primary thickening in monocotyledons.
ARL1 is an auxin-responsive factor involved in auxin-mediated cell dedifferentiation, and that it promotes the initial cell division in the pericycle cells adjacent to the peripheral vascular cylinder in the stem (Liu et al.
The tobacco hydroxyproline-rich glycoprotein HRGPnt3 is specifically expressed in subsets of the pericycle and endodermal cells from which the lateral root are initiated and is considered to be involved in the hardening of the cell wall at the root tip, providing the mechanical strength required for penetrating through the cortex and epidermis of the main root (Keller & Lamb, 1989).
2] diffusion (Hirsch, 1992), and ENOD40, which alters the cytokinin/auxin balance in the root pericycle leading to cortical cell divisions (Mylona et al.
It was not then appreciated that, early in development, the pericycle is not clearly delimited from the first phloem tissue.
The pericycle cells between the lateral root primordium and the parent root stele give rise to the vascular connection between the roots.