Heartwood vs Sapwood
In both softwoods and hardwoods, the wood in the trunk of the tree is typically divided into two zones, each of which serves important functions distinct from the other. The band of lighter colored wood adjacent to the bark is called sapwood. Heartwood is the darker colored wood found in the interior of the tree, at it’s core.
See the descriptions of each zone of a tree.
Living cells of the sapwood are also the agents of heartwood formation. Biochemicals must be actively synthesized and translocated by living cells. For this reason, living cells at the border between heartwood and sapwood are responsible for the formation and deposition of heartwood chemicals, one important step leading to heartwood formation.