Sapwood

Upon maturation of both softwoods and hardwoods, the parenchyma cells at the core die. This portion of the wood is called heartwood and often contains polyphenols, davones, and other colored compounds that do not occur in the contrasting sapwood. A clear, visual distinction usually exists between heartwood and sapwood, depending on the species. Heartwood compounds, eg, dihydro quercetin (taxifofin,... 

Another form of equalizing stains is through the use of sap stain. Color differences between the sapwood and late-growth area of the lumber can be made uniform by using this type of stain. Sap stains are usually alcohol-based dye stains that tie lighter areas of the wood into darker areas. Transparency of sap stain and equalizers is important to ensure a natural, nonpainted appearance. 

Just under the bark of a tree is a thin layer of cells, not visible to the naked eye, called the cambium. Here, cells divide and eventually differentiate to form bark tissue outside of the cambium and wood or xylem tissue iaside of the cambium. This newly formed wood on the iaside contains many living cells and conducts sap upward ia the tree, and hence, is called sapwood. Eventually, the inner sapwood cells become iaactive and are transformed iato heartwood. This transformation is often accompanied by the formation of extractives that darken the wood, make it less porous, and sometimes provide more resistance to decay. 

Softwoods are generally more resistant to acids than are hardwoods because they have high lignin and low hemiceUulose contents. In general, heartwood is more resistant to acids than sapwood, probably because of heartwood s higher extractive content and slower movement of Hquid into the heartwood. For these reasons, the heartwood of certain conifers has been widely used in the chemical industry. 

Eor practical purposes, the sapwood of all species may be considered to be susceptible to biodeterioration. The heartwood of some species, however, contains toxic extractives that protect it against biological attack. Among the native species that have decay-resistant or highly decay-resistant heartwood are bald cypress, redwood, cedars, white oak, black locust, and black walnut (60). Douglas-fir, several of the pines, the larches, and honey locust... 

The moisture content of freshly cut wood varies between species and portions of the tree. Between species, it can be 30—70% on a total weight basis (65) commonly, it is 45—50%. Within a tree, the heartwood generally has lower moisture content than the sapwood. For hardwood species, this difference is usually small for softwood species such as Douglas-fir, the difference can be as great as 30% for heartwood compared with 50% for sapwood. 

Splint, m. sap, sapwood pin, peg, key splint, splifltfrei, a. free from sap, sapless. 

Splint-holz, n. sapwood, sap. -kohle, /. sphnt coal. 

Most wood species are subject to some form of biological attack, a hazard not encountered by most other constructional materials. Fungal decay and attack by termites and other insect borers and marine borers are the main problems. The heartwood of many timber species and the sapwood of most species can be impregnated with wood preservatives to prevent these problems. 

The sapwood of all timber species is susceptible to attack, so the use of a durable species usually requires the removal of the sapwood. However, since sapwood can usually be fully penetrated with preservative by an impregnation treatment, an overall durable product can be obtained from the timber of small trees of a durable species containing a high proportion of sapwood. 

Impermeable timbers have a good resistance to polluted atmospheres where acid fumes rapidly attack steel. Wood has given excellent service in the buildings of chemical works and railway stations. Permeable wood species and sapwood can suffer defibration problems caused by the sulphur dioxide of industrial atmospheres. Tile battens are particularly vulnerable. The heartwood of Douglas fir, pitch pine, larch, Scots pine/European redwood and many tropical hardwoods give good service in these conditions. 

Wood in chemical applications gives remarkably good service in the most severe conditions. Impermeable woods give the best results as any chemical degradation is confined to the surface, and the breakdown products are generally less harmful than metal corrosion products. Because of its permeability all sapwood must be removed. The low heat conductivity of wood is a property of considerable advantage for conserving heat and wood is commonly used for hot wells. 

Powder-post beetle (Lyctus spp.) sapwood of ring-porous hardwoods. 

Plant Material - The yellow heartwood was separated from the sapwood of JL, tullplfera and air dried before grinding. Other plant parts (leaf, stem bark, root bark, root, fruit, and flower) were collected, but alcoholic extracts showed no antimicrobial activity. 

The last example of ToF-SIMS analysis of natural fibres is of a structural characterization of wood species for an eventual dendrochronological study [Saito et al. 2008], The aim of this research was to develop a new method to differentiate heartwood and sapwood. In dendrochronology, when bark is not present on the samples, the presence of sapwood is the key to determining felling date. Usually, heartwood and sapwood can easily been differentiated by their colour, with heartwood being much darker. Nevertheless, in the case of... 

The radial distribution of the extractives in the wood from recently felled trees was then studied. It was shown that their concentration is low in the sapwood and increases just before the heartwood/sapwood boundary. Concentrations were then higher in the heart-wood. The increase in the concentration of the extractive is then a good means to find the boundary (Figure 15.8a). 

K. Saito, T. Mitsutani, T. Imai, Y. Matsushita and K. Fukushima, Discriminating the indistinguishable sapwood from heartwood in discolored ancient wood by direct molecular mapping of specific extractives using time of flight secondary ion mass spectrometry, Analytical Chemistry, 80, 1552 1557 (2008). 

D. Ganser, M. Burgdorf, R. Losch (2001) A novel approach to the in situ measurement of oxygen concentrations in the sapwood of woody plants. Plant, Cell and Environment, 24 1055-1064... 

It is possible that there will be differences in the reactivity of heartwood and sapwood, or between juvenile and mature wood in acetylation reactions. As a consequence, larger-dimension wood specimens containing both heartwood and sapwood, or mature and juvenile wood, could be liable to distortion when modified. Considering the importance of this to any commercial acetylation operation, it is surprising to see that there is, in fact, very little literature dealing with this issue. 

Figure 3.8 The relationship between WPG and weight loss due to decay by Coniophora puteana for Corsican pine sapwood modified with a variety of linear chain anhydrides (from data of Hill etaf, 2003).

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