When you carve your initials into a tree at eye level, do the initials grow higher with the tree or stay at the eye level?
Depending on your age when you did the deed, a decade later, your eye level may have changed, but the height at which you carved your initials would not. That’s because trees grow in a linear fashion with cell upon cell growing from the stems’ tips which are called apical meristems. The meristems are the mechanism for growth in plants and are located at the tips of branches and roots.
However, a specialized type of meristem, called vascular cambium, is also at work. It expands the girth of the tree and so your initials may become distorted as the circumference of the tree changes.
Trees are far more complicated than we generally think. That sturdy trunk has many layers.
The outer layer is bark which is designed to protect the tree from such things as temperature, insects, fungi and other diseases. And not all bark is equal. It can be as thick as one foot in a Douglas fir to very thin such as the bark of birch trees which is papery and peels. Bark is formed by specialized meristems sometimes called phellem.
Also called the “bast”. This fibrous material layer is responsible for taking the sugar rich products manufactured through photosynthesis in the leaves to all parts of the tree.
Just inside the outer bark is the cambium layer, one cell thick. These are the meristem cells, which produce phloem on one side and xylem or sapwood on the other, where the rings of the tree are formed. The outside of this ring is the growth that occurs in spring. The inside is growth that occurs over summer. These are the gins we count to determine the age of the tree.
Another name for sapwood is xylem. This is the layer that draws water, nitrogen and minerals from the soil up to the leaves.
This is the dead part of the tree that provides a sturdy central core to provide structure and strength. It is often darker than the inner sapwood.
The very center of the tree made up of parenchyma cells and air spaces. These cells do a little of everything. It stores and assists with the transport of water and sugars from the xylem and the phloem layers.
Animal growth is totally different in that our cells spread out in pre-determined patterns in all directions. When you carve your initials in a person, as in tattoos, the mark grows up in height with you.