Heartwood and Sapwood: In old dicot trees the greater part of the secondary wood in the center of the stem is filled with gums, resins, tannins, tyloses, etc., which makes it hard and non-functional. This region is known as Heartwood or Duramen. The narrower outer region of the secondary wood remains light-colored and is called Sapwood or Alburnum. Sapwood helps in inorganic translocation.