Biology – Structure of transport tissues | e-Consult

In a transverse section of a dicotyledonous root, the vascular bundles are arranged in a ring around a central pith. The xylem and phloem are found within these vascular bundles. Each vascular bundle is typically composed of xylem and phloem, often separated by a layer of cambium. The arrangement is not uniform throughout the root; it is more concentrated in the centre of the vascular cylinder.

Xylem is located towards the centre of the vascular bundle, closer to the pith. It forms a star-shaped or wedge-shaped pattern within the bundle. The xylem vessels are typically arranged with the wider end pointing towards the pith. Phloem is located between the xylem vessels, typically towards the periphery of the vascular bundle. It is often arranged in smaller, less regular shapes compared to the xylem. The cambium layer, which is responsible for secondary growth, lies between the xylem and phloem. The arrangement of vascular bundles in the root allows for efficient transport of water and minerals from the soil to the rest of the plant.