Wood can be broadly divided into tree rings, heartwood and sapwood, and bark.
(1) Tree annual rings
New cells are created on the trunk of trees every year. When these cells are formed, the size and shape of the cells vary according to the season. Cells formed in spring and summer are large, and the cell membrane is thin and flexible.
This is called spring. In autumn and winter, on the contrary, the cells are small, and the cell membrane is thick and firm. This is called autumn wood. Spring and autumn appear as concentric circles centered on the depth of the water. This is the annual ring. Tree rings indicate the number of years a tree has grown, and at the same time serve as a standard for strength.
It refers to the darkly colored part in the middle when the tree trunk is cut in cross-section. And since it is dead tissue, it has no physiological role and is responsible for supporting the tree. (Since growth has almost stopped, the wood is hard) Because there is almost no starch, it is more resistant to bacteria and insects than sapwood and has good durability.
It refers to the part with a relatively light color on the outside of the heartwood on the cross-section of the stem. As a cell that continues to grow, the wood is soft. And because of the high moisture content, deformation occurs a lot. So the material is not good.
The bark consists of two structures: outer bark and inner bark. The cells in this bark are loosely arranged, allowing access to oxygen and carbon dioxide required by the cells. The outer bark is formed by the cork cambium and has various shapes such as round or oval. The inner Bark serves to transport nutrients between the roots and leaves, and the outer bark serves to protect the inner tissues.