Trees with woody stems are some of the largest living things on earth – just think of giant redwood trees – and their wood provides us with material for construction, paper, heating, tools and utensils, and much more. But wood is not a single material, rather it is a collection of the different parts that these plants need to live and grow. What is a wood composition?
Heartwood and Sapwood – If you took a slice out of a tree, like in our picture, you would normally see two thick areas of wood that are usually different colors. Each year, the tree grows by adding a layer of sapwood to its stem. This tissue helps to hold up the tree, but its main job is to transport water up the stem from the roots to the leaves. Sapwood is made of up cells that are no longer living, just like human hair! As the tree gets bigger, chemical changes take place in the older layers of sapwood and change them into heartwood, which is much more resistant to decay.
Vascular Cambium – The vascular cambium is a layer of cells that produces vascular tissues, or cells that connect to each other and transport fluids within the tree. The vascular cambium produces xylem cells which form a layer towards the inside of the stem. Xylem tissue makes up sapwood. The vascular cambium also produces phloem tissue towards the outside of the stem.
Phloem – Phloem tissue is the inner layer of bark and is used to transport nutrients, most importantly sucrose, around the tree.
Periderm – The periderm is a thick layer of outré back that forms on many woody trees and which is mostly made of cork cells. These cells form a layer of water, bacteria, and insect resistant protection to keep the tree from becoming infected.
Do you know now what is a wood composition?