What is the term for the darker wood in the center of a tree?

What is the term for the darker wood in the center of a tree?

• A. Sapwood
• B. Bark
• C. Pith
• D. Heartwood

Answer: (D)

In tree wood anatomy, the darker wood in the center is heartwood. This form develops as the tree ages: older layers of xylem in the center stop transporting water and become impregnated with extractives such as tannins, resins, and other compounds. These substances darken the wood and give it greater durability, even though the cells are usually no longer living. The heartwood sits inside the lighter, living sapwood, which remains active in transporting water and nutrients up the stem. For contrast, the central tissue in some young stems is called the pith, which is soft and not the dark, durable core seen in mature trees. Bark, meanwhile, is the outer protective layer.

In tree wood anatomy, the darker wood in the center is heartwood. This form develops as the tree ages: older layers of xylem in the center stop transporting water and become impregnated with extractives such as tannins, resins, and other compounds. These substances darken the wood and give it greater durability, even though the cells are usually no longer living. The heartwood sits inside the lighter, living sapwood, which remains active in transporting water and nutrients up the stem. For contrast, the central tissue in some young stems is called the pith, which is soft and not the dark, durable core seen in mature trees. Bark, meanwhile, is the outer protective layer.