How do trees grow and develop?

Artículo revisado y aprobado por nuestro equipo editorial, siguiendo los criterios de redacción y edición de YuBrain.

Trees are usually present in our environment and are part of many of the landscapes that are common to us. But it is not so common that it is known what their biology is like, how they reproduce and grow and how their different parts interact. And when thinking about the biology of a tree, a fundamental aspect to consider is its photosynthetic function, a process that occurs in the leaves and which is the source of the oxygen we breathe.

As soon as it is born, a tree is a small seedling similar to many others, but its later growth will show its differences, developing a central stem with secondary branches that will produce leaves of different shapes and sizes. And in a few weeks, the small seedling transforms into a slender organism that will take the final shape of a fully developed tree.

Schematically, a tree can be divided into three parts: the roots, the trunk, and the crown or foliage. In turn, the foliage is made up of branches and leaves, and a fifth component must be considered, the flowers and fruits.

The roots

Trees are anchored to the ground by their roots, which extend underground in a similar proportion to the foliage that rises above the ground. A developed tree is composed mostly of dead or inactive cells, which make up the wood of the tree. A tree’s tissues grow in very few places on its body: at the ends of branches, in a thin layer that unfolds under the bark, and especially at the roots. The root structure of a tree can either be made up of a main root from which secondary roots unfold, or it can be made up of several roots without a predominant one. There are trees whose roots develop above the ground, a characteristic of many trees that grow in swamps or flood plains.

Roots of trees.
Roots of trees.

The main functions of the roots are the absorption of water and minerals from the soil through the root hairs. These microscopic structures extend from the roots, which can number in the millions in a tree. Water and minerals are essential for the functions of the tree; After being incorporated by the root hairs, they pass to the roots, constituting the raw sap, and are transported to the leaves through the bark of the trunk and branches.

The log

The trunk of a tree is the structure that supports its crown, and the route of transport of the raw sap to the leaves. The trunk is made up of an outer layer, the bark, and an inner body, the heartwood, made up of dead woody cells, known as wood.

The bark is the protection of the tree trunk against external threats, although it also has other functions, such as the elimination of waste from the organism, encapsulating the waste in its wood in the dead cells of the trunk, or eliminating it through the resins. The xylem of the bark transports water and salts from the roots to the leaves of the trees, while the phloem of the bark redistributes the inorganic and organic nutrients, mainly carbohydrates, produced in the places of the tree where it is produced. photosynthesis, the leaves, to all parts of the tree. The cambium is a layer a few cells thick located under the bark that generates the xylem towards the interior zone of the tree, and the phloem towards the exterior zone.

Growth rings of a tree trunk.
Visible growth rings on a tree trunk.

In some trees that grow in temperate forests, with marked seasonal differences, when the living layer of the trunk is incorporated into the wood, it marks growth rings in each year of development.

The cup

Depending on the species of tree, from a certain height, large and small branches begin to unfold from the trunk that make up the crown of the tree. From the branches grow leaves and flowers. The degree of development of the trunk and foliage differentiates a tree from a shrub.

The leaves are the food factories of the tree, where photosynthesis occurs. The energy of the trees comes from the sun and is captured using chlorophyll, the element that gives the leaves their green hue. With the incorporation of carbon dioxide from the air, carbohydrates are produced through photosynthesis. In this process the leaves produce oxygen, which is released into the air. This gas exchange is what is called tree respiration. The leaves of the trees have very different shapes and sizes, characteristic of each species, which in some cases live all year round (evergreen leaves) and in others they are born, grow and perish seasonally (deciduous leaves).

Ceibo / Seibo
Flowers in the cup of a ceibo

In the foliage of a developed tree other structures of great importance are generated, the flowers and the strobila, also called cones or cones. Flowers and strobili are the reproductive structures of trees, from which seeds are produced.

Sources

The secret of the trees . Scientific Culture Unit of the University of Zaragoza – Spanish Foundation of Science and Technology, 2018.

Gola, G., Negri, G., Cappeletti, C. Treatise on Botany . 2nd edition. Editorial Labor SA, Barcelona, ​​1965

Sergio Ribeiro Guevara (Ph.D.)
Sergio Ribeiro Guevara (Ph.D.)
(Doctor en Ingeniería) - COLABORADOR. Divulgador científico. Ingeniero físico nuclear.

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