the inner, nonliving part of a tree stem that is altered to a protective state as a result of normal, genetically controlled aging processes as cells die, and that provides mechanical support —note 1. heartwood cells have no living contents and no active or dynamic transport processes —note 2. extractives are often deposited in heartwood and these generally impart a color that is darker than the sapwood —see false heart This definition last updated 10/27/2008