Secrets of a tree trunk

The pith is the very center of a tree trunk. It is composed of soft tissue made from cells that are filled with air and plasma. These cells decompose fairly quickly.

Heartwood (inner xylem) is the inner layer of the xylem that surrounds the pith. It only provides mechanical support to the tree as it is composed of dead tissue and does not conduct water or nutrients. Also, it is usually dark in color.

Sapwood (outer xylem) is the outer layer of the xylem that surrounds heartwood and is composed of living tissue layers. It transports water, minerals and other essential nutrients from the roots to the crown of a tree, and is therefore, paler and softer than heartwood. Additionally, sapwood is where substances such as sugars and starches are stored, making it an integral part of a trees life, especially during leafless periods.

The cambium is a thin layer of living growth tissue, located between sapwood and phloem. It evenly covers the entire surface of a tree, from its roots to its branches. During the growing season, this growth layer divides existing cells and produces new rings of tissue that become part of xylem or the phloem. The cambium is very well hydrated during growing seasons, at which time the outer bark is weakly bonded to the tree and can easily be torn off. If the cambium stops functioning, the tree will die.

The phloem is a layer that transports carbohydrates and proteins which have been produced by leaves. In some trees, such as linden, elms or willows, the phloem is only of use value.

Bark of a tree is composed of dead tissue and formations of cork.

Hey, Explorer!

Did you know that you can check the age of tree that has been cut down? All you have to do is count the annual rings of wood growth from the outer layer to the very heart of the trunk.