leidingsbundels

Leidingsbundels, also called vascular bundles, are strands of conducting tissue in vascular plants that transport water, minerals, and organic nutrients between roots, stems, and leaves. They consist mainly of xylem and phloem, often accompanied by supportive and storage tissues such as sclerenchyma and parenchyma.

Structure and arrangement: In stems of dicotyledonous plants, vascular bundles form a ring surrounding the pith; in monocot stems, bundles are scattered. Each bundle typically has xylem toward the interior and phloem toward the exterior, with a cambial region between (in many dicots). In leaves, bundles run as veins, with a main midrib and smaller collateral veins forming a network. In roots, the vascular cylinder (stele) usually has xylem in the center and phloem around it, though arrangements vary by group.

Development and growth: Leidingsbundels develop from the procambium in the embryo. In many dicots, secondary growth adds vascular cambium and produces secondary xylem (wood) and secondary phloem, expanding the bundle system. In most monocots, true vascular cambium is absent or reduced, limiting secondary growth.

Functions and significance: The primary role is transport. Xylem transports water and minerals from roots to shoots; phloem distributes sugars and other assimilates from photosynthetic tissues to non-photosynthetic parts and storage sites. Bundling patterns influence mechanical strength, evaporation, and drought tolerance and aid in taxonomic identification.

See also: Vascular tissue, Xylem, Phloem, Leaf venation, Stele.