Why do some trees form heartwood in their trunks?
Quick Answer
Heartwood is the older, inner wood that trees convert into a strong central support. It is usually darker because the living cells die and fill with resins, tannins, and other deposits.
The Full Story
As a tree grows, the oldest xylem in the center of the trunk stops transporting water and becomes heartwood. This inner wood is no longer living tissue, but it helps stiffen the trunk and resist decay. Many species darken as chemicals such as tannins, resins, and gums accumulate; in oaks and cedars this can make heartwood much more durable than the outer sapwood. The transition is a normal part of long-term growth in many woody plants, especially mature trees. In forestry, heartwood is prized because it is often stronger and more rot-resistant than sapwood.
Key Facts
YouTube Angle
Suggested video title for this topic:
"Inside a tree trunk: why the center changes into tougher wood"
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