pericycle

n.
A plant tissue characteristic of the roots, located between the endodermis and phloem.

[French péricycle, from Greek perikuklos, spherical : peri-, peri- + kuklos, circle; see cycle.]

pericyclic per'i·cy'clic (-sī'klĭk, -sĭk'lĭk) adj.

As commonly defined, the outer boundary of the stele of plants. Originally it was interpreted as a band of cells between the phloem and the innermost layer (endodermis) of the cortex. Such pericycle is commonly found in roots and, in lower vascular plants, also in stems. In higher vascular plants, however, a distinct layer of cells may not be present between the phloem and the cortex. The pericycle, if present, may be composed of parenchyma or sclerenchyma cells with relatively thin or heavily thickened walls. It may be one to several layers in radial dimensions.

Primordia of branch roots commonly arise in the pericycle in seed plants, most frequently outside the xylem ridges (see illustration). The first cork cambium may also arise in the pericycle of those roots that have secondary vascular tissues. In roots, a part of the vascular cambium itself (that outside the primary xylem ridges) originates from pericycle cells. See also Cortex (plant); Endodermis; Lateral meristem; Parenchyma; Phloem; Root (botany); Sclerenchyma; Stem; Xylem.

Transection of central part of sugarbeet. (From K. Esau, Hilgardia, 9(8), 1935)

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