The anatomy of a tree would really interest even the most apathetic person. This is because trees are complex parts of nature that provide an endless list of benefits and an even greater amount of value. There are thousands of species of trees in the world, all in different shapes, sizes, colors, crops, and more. But one thing they all have in common: a trunk. All trees, both deciduous and coniferous, have a tree trunk in one form or another. And one of the most interesting facts about tree trunks is that they have 5 different layers! Read on to learn more about each layer of tree trunk and the purpose they serve.
Tree trunks
As mentioned, the tree trunks have 5 separate layers. They are the outer crust, the inner crust (bast), the layer of cambium cells, sapwood and heartwood. Each layer has its own purpose, but in general, the trunk’s main job is to protect and support the tree. Look below to review each layer and what they do.
Outer crust:
Like a shield, the outer bark of a log is there to protect the tree from its outside environment, including inclement weather, wildlife, pests, and more. It also controls humidity, preventing excess moisture in rain and snow and retaining sufficient moisture levels during dry seasons. It also provides insulation in cold climates and protects against sunburn in summer.
Phloem (inner bark):
The phloem, or inner layer of the bark, is the place where food and nutrients pass through the tree. This layer has a very important job, but a very short life. Eventually it dies, turns into cork and becomes part of the outer layer of the bark.
Cambium cell layer:
The cell layer of the cambium is interesting because it is the part of the trunk that grows. Each year, this layer produces more bark and wood in reaction to hormones that are transmitted from the leaves along the food pipe. These hormones are called auxinsAnd they are very important because they stimulate the growth of new cells!
Sapwood:
Sapwood is new wood and plays an important role as a tree’s water pipe, delivering water to the entire tree. And as new sapwood is created, the inner cells lose their vigor and become heartwood.
Heartwood:
The heartwood is the innermost part of the trunk. It plays an important role in a tree’s balance, stability, and safety. Technically, the heartwood is dead, but it does not atrophy or rot (unless the outer layers are in danger). It is made up of hollow, needle-shaped cellulose fibers that are held together by a glue-like chemical called lignin.
