What is a tree and how does it function?

We have all at least once in our lives been fascinated by the trees that we pass. Their beauty, their majesty can only inspire us.
Some are content to just watch. Others want to understand how a tree works.

Here at Bonsai Pictures we will try to answer this question, at least in part, the subject is so vast, a comprehensive study would require pages and pages.

A tree, what is it?
To bear the name, certain qualities are required. You must be a plant consisting of roots, trunk (s) and the branches. In addition, the plant must be either a dicotyledonous Angiosperms, one Gymnosperm.

But this does not prevent us from giving this name to those that we grow in pots. The growth of this plant is in height and diameter throughout its whole existence. Branches elongate, new branches are created and later converted into branches.

The growth takes place mainly in spring but also in summer. It is composed (from bottom to top) roots, a crown, a trunk and a crown or crowns.

The roots:

Most trees have a taproot more or less important. This is the first which is formed from the germination of the seed. It does not regrow if it is cut.

The roots have three functions: to anchor the tree in the soil, to gather water and food and to store nutrients.

Root growth is by elongation of roots within them. Moreover, they need to breathe. It is important that the soil contains air. The roots are covered with hairs that are designed to draw water and food in the soil.

- The collar:

This is the liaison between the roots and trunk. That is what we call the nébari.

- The trunk:

In hardwoods, it is composed of the following, from inside to outside:

Marrow: tissue a little soft in the center of the trunk. It is formed at the beginning of the growth of the tree and does not change. It has a different shape depending on the species.

The heartwood: composed of dead cells that eventually evolve. The rings mark the sapwood layers superimposed over the years. This is the support of the tree which is called also the perfect timber. The sap moves there.

The cambium: It is a thin layer between the bark and sapwood. Once this layer is supplied with sap prepared from liber, it is responsible for the manufacture of new wood.

Sapwood (or xylem) is a layer produced by the cambium. It is composed of cells more or less live to be transformed into heartwood. These cells carry the raw sap of roots to leaves. It consists of resistant fibers, arranged in the longitudinal direction, forming the backbone of vessels and allowing the flow of sap flow.

The phloem: the most internal part of the tree has canals leading the sap of leaves developed cambial cells. The rest is composed of largely deadcells .

The bark is a fabric that protects the tree from disease, insect injury, etc. As the growth of the tree continues, the bark stretches, bursts and dies. It usually takes 1 to 2 years before the phloem is renewed. Sapwood by its expansion, pushes everything outwards.

The main points to remember are: the heart (or hardwood), the sapwood, the cambium, the phloem and bark.

- Branches:

They have the same composition as the internal structure of the trunk. They decrease in size and diameter as one moves away from the trunk and up into the tree. There are main branches (scaffold), secondary, tertiary, etc. …..

- Leaves:

The leaves emerge in spring, they emerge from buds that were formed during the summer and / or the previous fall and in which they were protected for the winter.

They are composed:

On the blade, a petiole, ribs. They are of different shapes depending on the species (leaves, needles or scales).

And further, we find:

cuticle: protective varnish
epidermis higher protective and which ensures the rigidity of the leaf
Tile fabric: where the chlorophyll is.
Tissue: in which the water and gas circulates
lower epidermis: which ensures the rigidity of the leaf
stomata: where oxygen and carbon dioxide are collected/ expelled
veins: channels so that the sap can flow.
So how does it all work?

Like any living being, the tree needs to feed and it does so mainly through the leaves and roots.

Photosynthesis is a process which, through light, the cells of leaves manufacture the organic carbonaceous material from water and mineral carbon (CO2).  Known as chlorophyll, this substance in the leaves gives them their green color. The process of photosynthesis basically intercepts light energy, and then converts this energy into chemical energy.

It is the withdrawal by fall of this very dominant green pigment that allows the other colors to emerge.

The stomata are located under the leaf and absorb carbon dioxide and release air. The roots in on the other hand absorb both minerals and draw up water.

The basis of the nutrient used by the tree are Nitrogen (N), phosphoric acid (P) and potash (K) which are found in the soil.

All these elements are then transported into the tree to allow the manufacture of tissue and build up reserves.

Absorption of water in the soil occurs through evapotranspiration. In the sun, the leaves transpire. The water they contain evaporates, creating a depression in the channels carrying the sap, creating a suction in the roots.

It is therefore the sap flow, also known as sap upward, which is a solution of minerals absorbed by the roots and travels through the xylem (part of the sapwood)

The reproduction of trees

They reproduce differently depending on whether they belong to the family of angiosperms (hardwoods) and gymnosperms (conifers). The arrival at the age of reproduction is highly variable from one species to another.

Angiosperms:

They are commonly dioecious (male and female feet). Pollination is by insects. The pollinated flowers develop into fruits containing one or more seeds.

Gymnosperms:

They are usually monoecious (male and female flowers on the same foot). The eggs are simply protected by scales.

Pollination is primarily by wind. The maturation of these seeds is long, it can range from a few months to several years.

Cycles of the season

Having pushed all spring and summer, the tree will begin a process that will allow them to rest.

For hardwoods, in the shortening days, reduce the chlorophyll in the leaves due to lack of light to ensure its existence, it disappears gradually. Leaves take on colors that were previously masked by the strong presence of chlorophyll. The colors vary according to species, ranging from yellow to red, through shades of orange.
Some hardwoods retain their leaves throughout the year, such as boxwood, for example. The case of conifers is different because they do not lose their needles (or scales in some cases).

There are some genres that lose all their foliage in the fall: Larix, Pseudolarix, Glyptostrobus, Metasequoia and Taxodium. The resin circulates in their tissues to protect them from freezing.
The tree has accumulated reserves that it has stored in its roots until a new cycle can start again the following spring.