(redirected from pericyclic)
Also found in: Dictionary, Medical.


The outer boundary of the stele of plants; may not be present as a distinct layer of cells.



(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.


References in periodicals archive ?
Mat-forming shrubs, stem lacking pericyclic sheath of fibers, with homogeneous pith.
Resin cure chemistry is dominated by `ene' reactions (otherwise known as pericyclic or electrocyclic reactions).
Barriault's research involves the development of novel strategies using tandem pericyclic reactions to construct complex bio-active natural products.
Pericyclic reactions, the third reaction mechanism are not common in this discussion.
He describes quantum mechanics for organic chemistry, fundamentals of organic chemistry, pericyclic reactions, diradicals and carbenes, organic reactions of anions, solution-phase organic chemistry, and organic reaction dynamics, all of which he punctuates with personal interviews with leading lights in the field.
Ron Childs, FCIC, has an international reputation for his studies of homoaromaticity and thermal and photochemical pericyclic reactions of carbenium ions.
Given the broadened nature of the subject, they have reorganized the material on the basis of functional groups and offer 12 chapters that parallel most classical organic chemistry textbooks in their coverage of alkanes, alkenes, alkynes, alcohols and ethers, organic halides, aromatics, aldehydes and ketones, carboxylic acid and derivatives, conjugated carbonyl compounds, amines, and pericyclic reactions.
The remaining chapters examine different types of acid-base, substitution, addition, elimination, pericyclic, and photochemical reactions.
Functionality and Pericyclic Reactions: Nitrogen Heterocycles by Cycloadditions and Sigmatropic Rearrangements