Roots, Trunk, and Branches in the Spring

What Do Roots Do?

Roots have many functions. You already know that roots absorb water from the soil. At the same time, they absorb minerals that the tree uses to grow tissue.

Roots have another very important function: they serve to anchor the tree in the soil so that the first windstorm doesn't blow it over!

Roots Are Sponges

Well, to be precise, the roots don't take up water and minerals from the soil. That's done by what we call root hairs, which grow on the roots. They act a little like sponges, absorbing the nutrients needed by the tree. Roots, which are woody like the tree's trunk and branches, transport the water and mineral salts to the tree's trunk and cells.

Very early each spring, the roots grow very quickly in order to find as much water and mineral salts as possible. The tree's development during this period is very fast and intense, so it needs lots of food.

Some trees have roots that grow near the surface of the soil, while the roots of others plunge deep into the ground. The roots of some species can be dozens of metres in length.

Oak roots extend deep into the earth.	Poplar roots remain near the surface.

City-dwelling Trees

Many towns plant trees along their streets. It's much nicer for us to stroll down a street bordered with trees than one without. It's a different matter for the trees, however. There's often not much room for roots to grow under these conditions. As the tree grows, it needs more water. The greater its need for water, the more roots it grows. The roots end up choking each other and the tree dies.

Branches

A tree grows both in height and girth each year. The branches stretch skyward to get as much light as possible. The trunk and branches grow to support an increasing number of leaves and branches. Most of this growth occurs in the spring, well before summer officially arrives, because there is an abundance of water in the soil.

Wood Cells and Annual Rings

Every spring, the tree produces a great number of wood cells, which tend to be large. Such wood is referred to as early wood.

Annual rings can also indicate past weather conditions. Annual rings started in the spring and wet summers are much thicker because the tree was able to produce an abundance of large cells. The tree has more difficulty producing cells during droughts, so that annual rings are thinner.

Although nearly all the cells in your body can reproduce, only the cell layer just under the bark can divide in trees. This layer of cells is called the cambium. It divides towards the trunk to produce wood and towards the outside to form bark. This is how cells reproduce and the tree grows.

Every spring, sap, which is made of water and minerals, is absorbed by the roots and flows upward through the trunk to the leaves. The wood in the trunk and branches is made of very long cells called vessels, which carry the sap. The sap therefore is a little like the blood that flows in your veins.

Only the cells in the rings that are three or four years old conduct sap. This part of the tree is called the sapwood or alburnum. The remainder are for reserves or for structural support. These inner layers of wood are referred to as the heartwood or duramen, which can sometimes take on a dark color.

Bark

Bark's main purpose is to protect the tree. It's a little bit like our skin. The bark protects the tree against disease, insects, fire, drought, injury, and animals.