vascular bundle


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vascular bundle,

in botany, a strand of conducting tissue extending lengthwise through the stems and roots of higher plants, including the ferns, fern allies, gymnosperms, and angiosperms. The vascular bundle consists of xylem, which conducts water and dissolved mineral substances from the soil to the leaves, and phloem, which conducts dissolved foods, especially sugars, from the leaves to the storage tissues of the stem and root. The structure of vascular bundles varies among the different plant groups. See woodwood,
botanically, the xylem tissue that forms the bulk of the stem of a woody plant. Xylem conducts sap upward from the roots to the leaves, stores food in the form of complex carbohydrates, and provides support; it is made up of various types of cells specialized for each of
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Vascular Bundle

 

in plants, the aggregate of elements of the vascular tissue. The vascular bundle appears in the sprout from the apical meristem or, more precisely, from the procam-bium. It comprises the xylem, the phloem, mechanical tissues, and cells of the living parenchyma. A vascular bundle may be complete or incomplete; that is, in the latter case it may consist of only phloem or only xylem. Dicotyledons are marked by open vascular bundles; in other words, part of the procambium is not differentiated into vascular tissue and remains in the form of cambium. Monocotyledons have closed bundles, without a cambium.

In a collateral bundle, the phloem occurs along one side of the stem, outside the xylem. The presence of phloem along both sides of the xylem makes the bundle bicollateral. A concentric bundle is one that is either amphibasal, with the xylem surrounding the phloem, or amphicribral, with the phloem surrounding the xylem. The structure of a vascular bundle may vary at different points along the stem.

In roots the vascular bundles form radial structures consisting of individual alternating sections of xylem and phloem along the radii of the vascular cylinder.

vascular bundle

[′vas·kyə·lər ′bənd·əl]
(botany)
A strandlike part of the plant vascular system containing xylem and phloem.
References in periodicals archive ?
Large cortical cell area, epidermal thickness, midrib thickness, vascular bundle area, metaxylem area and spongy cell area in leaves increased in all Rosa species as contamination increased in irrigation waters and R.
Distance between vascular bundles and the proportion between xylem and phloem were estimated.
They reported that a vascular bundle is longest and smallest at the outer zone but shorter and bigger towards the inner zone.
The parenchyma cells adjacent to vascular bundles have considerably thickened walls with distinctly visible pits (Barkley, 1924).
SB = Stylet bundle, Ep = Epidermis, PP = Palisade parenchyma, VB = Vascular bundle.
These authors showed that five following characters are likely to be useful for comparison between and within subfamilies: a) whether the inner integument is thick or thin; b) the presence or absence of vascular bundles in the inner integument; c) whether ovules or seeds are pachychalazal or not; d) whether seeds are arillate or not; and e) whether an exotegmen is fibrous or not.
Separating the cortex from the pith (both ground tissues) is a ring of vascular bundles (see Figure 7-10), the number of which is determined by the complexity of the tissue.
Quantitatively evaluated were the following: (1) thickness of the foliar mesophyll; (2) thickness of the group of fibers from the foliar rib; (3) average diameter of the central vascular bundle of the foliar blade; (4) thickness of the cuticle; (5) size of the bulliform cells; (6) root diameter; (7) thickness of the root epidermis; (8) count of the poles of protoxylem; and (9) the diameter of the vascular cylinder of the root.
9 anatomical characters of the leaves and scape (micropapillae in cuticle, papillae in upper and lower epiderma, margin extensions, mesophyll structure, vascular bundle types, cavities, crystal types, vascular bundles in the periphery of scape and vascular bundles at the middle of scape) were used for distinguishing of investigated taxa (Table 2).
A) Dorsiventral mesophyll; (B) Detail of the cells of stomata (arrow); (C) Idioblasts in the mesophyll with crystals (arrow) and oil (arrowhead); (D) Blade edge; (E) Midrib showing cylindrical main vascular bundle, sclerenchyma sheath (arrowhead) and small amphicribal bundle (arrow); (F) Detail of small amphicribal bundle; (G) Detail of midrib; (H) Sclerified cells (arrow).
incognita inoculated plants because it blocked the vascular bundle and retarded the uptake of nutrients and water.