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Sapwood and Heartwood

The document discusses the differences between sapwood and heartwood in trees, defining sapwood as living cells that conduct nutrients and heartwood as the dead central wood that provides mechanical support. It outlines the structures, functions, and economic importance of both wood types, detailing how sapwood transitions to heartwood and the chemical changes involved. The economic aspects highlight heartwood's durability in timber and sapwood's applications in pulpwood and preservation treatments.

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Assignment Plant Anatomy Topic Sapwood and Heartwood Submitted to: Sir Ghulam Sarwar Submitted by: Areej Fatima Roll No:27, Session: 2013-2017 B.S (HONS.) Botany Department of Life Sciences The Islamia University of Bahawalpur
Sapwood and Heartwood Definitions of Sapwood and Heartwood Sapwood: “When a tree is young, certain cells within the wood are alive and capable of conducting sap or storing nutrients, and the wood is referred to as sapwood. The sapwood also termed as Alebernum.” Heartwood: “Heartwood also called duramen. Dead central wood of trees. As new sapwood is formed under the bark, the inner sap wood changes to heartwood. In the wood under going this change the living cells die.”
Maple tree and Black locust tree cross section The sapwood in the centre of the tree dies, forming heartwood, and as the cells die they release chemicals that change the colour of the wood, as well as making the wood stronger and more resistant to attack by insects.
Structure and Development of Sapwood and Heartwood • Sapwood is new wood and is like a pipeline which moves water through the tree up to the leaves. • The sapwood is lighted colored and formed of living cells associated with vessels and fibers. • Sapwood commonly ranges from 4 to 6 cm (1-1/2 to 2 in.) in radial thickness. • Many second-growth trees of merchantable size consist mostly of sapwood.
• Heartwood consists of inactive cells that do not function in either water conduction or food storage. • The compounds (including resins, phenols, and terpenes, sometimes referred to as extractives) not only help make heartwood more resistant to attack by insects and decay organisms but also tend to give this inner portion of the stem a distinctive darker color. • The proportion of heartwood to sapwood in the main stem does vary with species. Black locust, for example, usually has a very narrow band – often less than an inch – of functioning sapwood, whereas maple stems often can have many inches of sapwood and relatively narrow cores of heartwood.
Structure of Sapwood and Heartwood
• Sapwood is formed due to the cambial activity of the secondary xylem. • Heartwood is formed due to accumulation of different compounds, such as oils gums, and resins, etc. • The oils, resins and colouring materials infiltrate the walls, and gums and resins may fill the lumina of the cells in heart wood. • During the transformation a number of changes occur – all living cells lose protoplasts; water contents of cell walls are reduced; food materials are withdrawn from the living cells; tyloses are frequently formed which block the vessels, the parenchyma walls become lignified; oils, gums, tannins, resins and other substances develop in the cells.
Structure of Sapwood and Heartwood
Functions of Sapwood and Heartwood • Sapwood performs the physiological activities, such as conduction of water and nutrients, storage of food, etc. • The function of heartwood is no longer of conduction, it gives only mechanical support to the stem. • The heartwood part of a tree is also far more susceptible to fungus than the centre of the trunk. • Heartwood contains far less moisture than sapwood and will have far less shrinkage when it’s dried. • The sapwood in the centre of the tree dies, forming heartwood, and as the cells die they release chemicals that change the colour of the wood, as well as making the wood stronger and more resistant to attack by insects.
Economic Importance of Heartwood and Sapwood • Heartwood, as timber, is more durable than sapwood, because the reduction of food materials available for pathogens by the absence of protoplasm and starch. • The haematoxylin is obtained from the heartwood of Haematoxylin campechianum. Because of the absence of resin, gums and colouring substances. • Sap wood is preferred for pulpwood, and for wood to be impregnated with preservatives.
Red Oak Logs
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