Biology – Structure of transport tissues | e-Consult

In a transverse section of a dicotyledonous stem, the vascular bundles are arranged in a ring. The arrangement is not uniform; the number of vascular bundles varies depending on the plant species and the position within the stem. The vascular bundles are typically closer together near the pith and become more spread out towards the cortex.

Xylem is located towards the inner side of the vascular bundles, closer to the pith. It forms a distinct, often star-shaped pattern within each bundle. The xylem vessels are typically arranged with the wider end pointing towards the pith. Phloem is located between the xylem bundles, typically towards the outer side of the vascular bundles. It is often arranged in smaller, less regular shapes compared to the xylem. The cambium layer is present between the xylem and phloem in each vascular bundle, allowing for secondary growth.

As you move outwards from the pith, the vascular bundles become more numerous and more widely spaced. This arrangement provides a robust framework for the stem and allows for efficient transport of water and nutrients throughout the plant. The arrangement also contributes to the stem's mechanical strength.