Despite the fact that we are surrounded by trees, there are some widespread misconceptions regarding the way that trees grow” says a tree expert at Technical Arboriculture. When how a real tree grows is studied, surprising mechanisms are revealed that evolve together in these intricate plants.
Trees can be viewed as a collection of yearly plants. Each of them grows at the end of an interconnecting, large plumbing system. These plants are called twigs. They create a tree’s fruit, flowers and leaves. They are by themselves similar to other plants. What really sets them apart is their connection with the large system. This branching system distributes the flow of sugar, water and hormones to and away from the twigs – which regulates the evolution and growth of trees into those majestic structure that all of us admire so much.
With older branches, there is just a thin outer layer right under the bark that is living tissue. The remainder of the branch is comprised of old dead cells. The cell walls is what provides a tree with the structural strength it needs in order to stand tall. Most importantly, the sponge like structure they have sucks water out of the roots and then up through each branch and finally to the leaves.
Water is used in several ways by a tree. As water is moving up through a tree’s branches, it gets filtered for its minerals and nutrients. In order to keep the flow steady so that the tree gets enough nutrients, the surface of each leaf evaporates water in the sun’s heat. This dries the sponge out and even more water gets sucked up from the soil.
Leaves use water for performing photosynthesis in addition to evaporating water. That lead us to a discussion on sugar flow. Leaves absorb energy from the sun, taking carbon dioxide and water and binding them so that sugar molecules are formed. These sugars are used by the whole tree as an energy store. The sugar flow occurs within the branches living tissue – which is the thin layer right below the bark. It continues to be filled up by the leaves and whatever connected cells need energy draw it out. Buds, branches, trunk and roots are all connected.
Both water and sugar flows are used for distributing hormones. For example the apical meristems, which are the tips of the branches where new cells grow, produce the hormone Auxin for regulating growth. The hormones tells the branches that are lower down to lay low.
We now understand how the growth of a tree is regulated on a large scale. We will take a closer look at the twigs next. Although the hormones that flow through the tree’s plumbing system give the twigs their orders, they are still quite individualistic plants. A twig’s life begins in a bud.
On the end of each of the branches and on the base of every leaf, a bud grows. The embryonic beginnings of the twig is contained there, which is encased within a protective cocoon that helps it survive winter.
A large number of twigs grow from the buds every year. Twigs are a tree’s eyes and ears. Trees are unable to hear, however, beyond that they have as many senses as animals do. The twigs depend on those senses to determine where they should grow. A tree has a sense of balance that it can use to grow against gravity. This is called gravitropism by biologists. It causes roots to grow down and the tree to grow up.
Light is the food of trees which makes it critically important. So it isn’t surprising that trees have developed superior senses when it comes to light. Many different hues of light are sensed by twigs. When a twig doesn’t see enough light, it begins vigorous growth in hopes to find it.