Collateral Bundle

Also found in: Medical.

collateral bundle

[kə¦lad·ə·rəl ′bənd·əl]
A vascular bundle in which the phloem and xylem lie on the same radius, with the phloem located toward the periphery of the stem and the xylem toward the center.

Collateral Bundle


a bundle of conducting tissues of xylem and phloem in the stems and leaves of plants. In stems the exterior side of the collateral bundle consists of phloem, and the interior of xylem. Collateral bundles may be closed or open. Closed collateral bundles lack secondary growth, because they contain no cambium. Closed collateral bundles are present in almost all monocotyledonous plants. In open collateral bundles, which are characteristic of the stems of dicotyledonous, gymnospermous, and some pteridoid plants, there is a layer of cambium cells between the phloem and the xylem. As a result of cell division in this layer, new elements of the phloem and xylem are formed (secondary thickening of the stem).

References in periodicals archive ?
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.
The parenchymatous pith has free collateral bundles and mucilage channels.

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