alburnum

Alburnum, in botanical wood anatomy, is the portion of the woody stem or root that remains the living, conducting part of the xylem. It is commonly equated with sapwood and lies between the cambium and the heartwood (duramen). The alburnum is typically lighter in color than the heartwood and consists of living parenchyma and ray cells, along with the conducting elements of the xylem, which are dead at maturity but form the main conduits for water and mineral transport from roots toward the shoots.

The alburnum is responsible for short-term storage of nutrients and for radial transport within the xylem. In young trees or healthy individuals, the alburnum remains actively functional; in older trees, portions may gradually become heartwood as extractives are deposited and the tissue loses its conductive role.

Heartwood is darker and more resistant to decay due to these extractives, while the alburnum remains the more vulnerable sapwood. The boundary between alburnum and duramen can be well defined in some species but is diffuse in others. In timber assessment, the proportion and condition of sapwood influence durability, workability, and aesthetic properties. Etymologically, alburnum derives from Latin and historically denotes white or pale wood. Modern terminology often prefers sapwood, but alburnum remains a recognized term in wood anatomy.