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Vascular bundle

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Longitudinal strand of vascular tissue in the roots, stems & leaves, of higher plants.

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**Types of Vascular bundles**
(blue: Xylem, green: Phloem, white: Cambium)
A concentric, periphloematic(Hadrocentric)
B concentric, perixylematic(Leptocentric)
C radial with inner xylem, here with four xylem-poles, left closed, right open
D collateral closed
E collateral open
F bicollateral open

Cross section ofcelery stalk, showing vascular bundles, which includes both phloem and xylem

Detail of vascular bundle: closed, collateral vascular bundles of the stem axis ofZea mays

Vascular bundle in theleaf ofMetasequoia glyptostroboides

The vascular bundle of pine leaf showing xylem and phloem

Avascular bundle is a part of the transport system invascular plants. The transport itself happens in thestem, which exists in two forms:xylem andphloem. Both these tissues are present in a vascular bundle, which in addition will include supporting and protective tissues. There is also a tissue between xylem and phloem, which is thecambium.

The xylem typically lies towards the axis (adaxial) with phloem positioned away from the axis (abaxial). In a stem or root this means that the xylem is closer to the centre of the stem or root while the phloem is closer to the exterior. In a leaf, the adaxial surface of the leaf will usually be the upper side, with the abaxial surface the lower side.

The sugars synthesized by the plant with sun light are transported by the phloem, which is closer to the lower surface.Aphids andleaf hoppers feed off of these sugars by tapping into the phloem. This is why aphids and leaf hoppers are typically found on the underside of a leaf rather than on the top. The position of vascular bundles relative to each other may vary considerably: seestele. The vascular bundle are depend on size of veins

Cross section of a leaf showing parts of a vascular bundle

Bundle-sheath cells

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The bundle-sheath cells are the photosynthetic cells arranged into a tightly packed sheath around the vein of a leaf. It forms a protective covering on the leaf vein and consists of one or more cell layers, usuallyparenchyma. Loosely-arrangedmesophyll cells lie between the bundle sheath and the leaf surface. TheCalvin cycle is confined to thechloroplasts of these bundle sheath cells inC₄ plants.C₂ plants also use a variation of this structure.^[1]

References

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^Sage, Rowan F.; Khoshravesh, Roxana; Sage, Tammy L. (1 July 2014)."From proto-Kranz to C4 Kranz: building the bridge to C4 photosynthesis".Journal of Experimental Botany.65 (13):3341–3356.doi:10.1093/jxb/eru180.PMID 24803502.

External links

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Curtis, Lersten, and Nowak cross section of a vascular bundle
Mauseth another cross section of a vascular bundle

Botany

Subdisciplines

Plant groups

Plant anatomy

Plant morphology
(glossary)

Plant cells	Cell wall Phragmoplast Plastid Plasmodesma Vacuole
Tissues	Cork Ground tissue Mesophyll Meristem Storage organs Vascular tissue Vascular bundle Wood
Vegetative	Bulb Root Rhizoid Rhizome Shoot Bud Leaf Cataphyll Petiole Sessility Stem
Reproductive (incl. Flower)	Archegonium Antheridium Androecium Pollen Stamen Anther Filament Staminode Tapetum Flower Aestivation Flower development Floral diagram Floral formula Floral symmetry Whorl Fruit Anatomy Berry Capsule Nut Pyrena Seed Dispersal Endosperm Gametophyte Gynandrium Gynoecium Carpel Ovary Locule Ovule Stigma Style Hypanthium (Floral cup) Inflorescence Bract Pedicellate Raceme Umbel Perianth Tepal Petal Sepal Plant embryo Receptacle Sporophyll Sporophyte
Surface structures	Cuticle Epicuticular wax Epidermis Nectar Stoma Thorns, spines, and prickles Trichome