A tree is one of the forms of plant life, which generally grows on land and needs varying amounts of water. Trees are generally distinguished from other plants by having roots, stems and branches, and by their relatively large size compared to other plants such as grass and algae .
It is what grows from the ground as a result of a vital process called photosynthesis (or photosynthesis ), and the elements that cause the emergence of trees are water , light and carbon dioxide
Trees play several vanguard roles, both ecologically and economically. The tree is the largest of the plants. Its height may exceed a 30-storey building. It is the largest living known neighborhood, where many trees live to much longer ages than the rest of the plants, and some live thousands of years.
People do not look at trees as they look at other plants, most of which grow for a short time and then die, but rather they look at them as fixed features in the landscape. For many years, large perennial trees shaded houses and streets, protecting them from the sun's glare, and providing protective cover for birds and other wild animals. Its buds and flowers herald the arrival of spring every year. In many temperate regions, its leaves put on a bright display of color in the fall.
Trees continue to grow throughout their lives. The leaves of the trees make the food needed to keep the tree alive and to help it grow. In areas with cold winters, many trees lose their leaves in the fall, while other trees keep their leaves during the winter, thus remaining green throughout the year. Trees that lose their leaves in the fall go into a dormant phase during the winter. With the advent of spring, new leaves and flowers sprout. The flowers grow and turn into fruits that contain the seeds from which new trees sprout. The fruits of some trees, such as apples and oranges, are sweet in taste. Fruit growers grow large quantities of these fruits for marketing purposes. Trees also grow and make new wood each year when the weather gets warm. Wood is one of the most expensive tree products.
Dwarf trees do not reach their natural size, and some of them, such as this miniature cypress tree, are preserved in this size on purpose, by pruning in a special way, but many dwarf trees grow naturally in the Arctic region.
The Great Giant Sequoia , California, USA, is one of the largest living things in the world by age and size. Some trees may be thousands of years old and reach a height of more than 60 m.
Trees differ from other plants in four main points: 1- Most trees grow to a height of no less than 4.5-6 m, 2- They have one wooden stem called the trunk, 3- The stem grows to a thickness of not less than 8-10 cm, 4- The trunk of the tree stands in his own position. And all other plants differ from trees - at least - in one of these points. For example, a plant is not a tree if it has a soft stem and a lot of juice. Most of these plants, which are called herbs, are less tall than most trees, and shrubs - like trees - also have woody stems, but most bushes have more than one stem and do not grow to the thickness and height that the trunks of trees reach. Some forest plants grow to lengths of up to 60 m, and they have a wooden stem. But this market is not strong enough to support it.
There are thousands of species of trees, but most trees belong to one of two main groups: broadleaf trees and needle-leaved trees. These two types of trees grow in Asia, Europe, North America and many other parts of the world. Most of the prevailing trees are in Australia; Such as gum trees (eucalyptus) and Australian acacia trees (acacia) are broad-leaved trees, and most of the endemic trees in New Zealand are also dominated by broad-leaved trees. Most other tree species such as cycads, ginkgo, palm species and tree ferns grow mainly in warm regions.