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Perennial woody plant

Tree (lat. árbor) is a life form of woody plants with a single, clearly expressed, perennial, in varying degrees, woody, surviving throughout life, branched (except palms) main axis - trunk.

The total number of trees on planet Earth in 2015 was estimated at 3 trillion. On the territory of Russia there are 640 billion trees (first place in the world). The territories of Canada and Brazil each have 300 billion. Every year the number of trees on the planet decreases by about 15 billion as a result of both deforestation and climate change. Tree cutting is done primarily to obtain wood, which is a fairly common building material and is also used to make paper.


Conifers are usually characterized by stiff evergreen (rarely summergreen) needle-like or scaly leaves called needles, or needles, form cones or juniper berries. This group includes, for example, pines, spruces, firs, larches, cypresses, and sequoias.

Broad-leaved trees have broad and flat leaves - which are much less thick than their length and width, usually falling off once a year. Broadleaf (or just deciduous) trees usually flower and bear fruit. This group includes maples, beeches, ash trees, eucalyptus trees, and others.

In addition to classification by leaf type, trees are divided by leaf life span - into deciduous and evergreen.

Deciduous trees have a clear change of foliage: all leaves on the tree lose their green color and fall, for some time (in winter) the tree stands without leaves, then (in spring) new leaves grow from the buds.

Evergreen trees do not have a clear change of foliage: the leaves are on the tree at any time of the year, and the change of leaves occurs gradually, throughout the life of the tree.

In addition to the biological classification, trees are also divided according to other characteristics: for example, fruit trees (whose fruits are used by humans for food), valuable trees (whose timber is used for industrial purposes), ship trees (used in shipbuilding), tropical trees (whose range is close to the equator), northern trees (whose range is far from the equator), and so on.


The root of a tree is usually the underground part of the plant. Its main functions are to keep the tree upright, absorb nutrients from the soil and transfer them to the trunk. Roots are long: they can go as deep as 30 meters and extend up to 100 meters to the sides. Some trees have aerial roots, which are above the surface of the ground, and their function is similar to that of leaves.

The trunk of the tree acts as a support for the crown and also transfers substances between the roots and the crown. In winter, it acts as a storehouse of moisture and nutrients. The tree trunk consists of the heartwood, the wood that grows from the cambium inward to form annual rings - dark and light areas visible on the cross-section of the tree. The number of annual rings in temperate forests corresponds to the age of the tree, and their thickness corresponds to the living conditions of the tree in each particular year. In arid areas, trees may develop false rings after rainfall. The outside of the trunk is covered by bark. During its lifetime, a tree usually has a single trunk. When the main trunk is damaged (cut down), some trees may develop sister trunks from dormant buds. The part of the trunk from the base to the first limbs is called the stem.

The crown of a tree is the set of branches and leaves at the top of a plant that continues the trunk from the first branch to the top of the tree or shrub with all the lateral branches and foliage. A distinction is made between crown shape, from column-shaped to spreading, and crown density, from dense to sparse, openwork. Photosynthesis produces essential substances in the leaves as a result of light.


Further Resources


Lecture 5 Tree Anatomy and Physiology Part 1 Video


August 11, 2017

Tree Biology


January 17, 2022

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