vascular bundle

The fluid-carrying tissue of most plants is normally arranged in units called vascular bundles. The vascular tissue is of two types: xylem and phloem. The xylem carries water up through the plant; the phloem distributes food made in the leaves to all parts of the plant.

The veins of a maple (Acer) leaf. As in most plants, the leaf is the primary food-manufacturing organ of the maple. The veins act as a skeletal structure and transport materials to and from the leaf tissue. In the autumn, the green chlorophyll breaks down, revealing the striking yellow, orange, and red pigments in the leaf.

In botany, strand of primary conducting tissue (a ‘vein’) in vascular plants, consisting mainly of water-conducting tissues, metaxylem and protoxylem, which together make up the primary xylem, and nutrient-conducting tissue, phloem. It extends from the roots to the stems and leaves. Typically the phloem is situated nearest to the epidermis and the xylem towards the centre of the bundle. In plants exhibiting secondary growth, the xylem and phloem are separated by a thin layer of vascular cambium, which gives rise to new conducting tissues.