Tree - Tree Taxonomy, History Of Taxonomy, Modern Taxonomy, Cell Layers In A Tree Trunk, Growth Rings - Secondary growth
tissues provide cambium trees
A tree is a woody plant which has three principle characteristics: (a) the potential to grow to 20 ft (6.1 m) or more in height; (b) the formation of one or more trunks arising from the ground; and (c) the ability to stand on its own without support. Trees provide many products which are important to humans, such as timber, fruits, and nuts. They are also the dominant plants in the world's forests, and thus provide critical habitats for the other species which live there.
Most trees increase in thickness due to cell division in two special layers of undifferentiated tissues near the outside of their stems. This is known as secondary growth. The two tissues are referred to as the vascular cambium and the cork cambium. In contrast, herbs do not have secondary growth, and they stop growing once their primary tissues have matured.
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Carl von Linné of Sweden began the modern study of taxonomy in the mid-1700s. He classified trees and other plants according to the morphology of their reproductive structures, such as the flowers and fruits of Angiosperms, and the cones of Gymnosperms. Many religious leaders of his time considered it immoral to study the reproductive structures of plants. However, modern taxonomists still …
In a typical, sawed-off sector of a tree trunk, one encounters layers of different cells and a series of concentric, annual growth rings going from the outside toward the inside. The cork of bark is on the external surface of the trunk, and consists of dead cells which are impregnated with suberin, a waxy substance which inhibits evaporation of water through the bark. The cork cambium lies just in…
Trees are the dominant organisms of forests. Climate and other factors determine which tree species grow in a forest. Forest ecologists have classified the forests of the world according to the species of trees that grow there. One classification scheme is described below. Coniferous forests are characteristic of the boreal forests of cold regions of the northern hemisphere. The boreal forest is f…
Most plant physiologists now accept the "cohesion-tension theory" as an explanation for the ascent of sap. According to this theory, water moves up the trunk of a tree in narrow, elongated cells near the periphery of the trunk, referred to as the xylem, and does not require the expenditure of metabolic energy. The movement of water only depends upon three important physical-chemical …
Trees have great economic significance to humans as a source of food, building materials, and paper. Almond, coconut, cherry, prune, peach, pear, and many other tree species are grown in orchards for their fruits and nuts. The apple tree is the orchard tree of greatest economic significance, and there are several hundred different varieties of apples. (Many of North America's best apples gr…
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