Wood#Heartwood and sapwood
Heartwood referred on numerous tree species in the root cross-section no longer physiologically active, mostly dark, inner zone, which differs significantly from the outer, bright sapwood. It occurs due to secondary metabolic processes of dying parenchyma in the inner sapwood.
Genuine heartwood contains predominantly colored, mostly phenolic compounds ( nuclear materials ), which impregnate the cell walls and generally increase the durability of the wood. The tree also interrupts the connections between the cells by closure of bordered pits ( softwood ) or by Verthyllung the vessels ( hardwood), so that no capillary exchange is possible. Heartwood is dead wood (see also heartwood ). Hoopwood is also heartwood, but does not stand out color from the sapwood. The previously common difference in core and hoopwood is outdated. Podocarpus forms such as a light but durable hoopwood ( = heartwood ), while the spruce is a little permanent hoopwood. We speak today of mandatory and optional Verkernern. Mandatory Verkerner form real heartwood, while optional Verkerner may form a false core.
Cross section through an ash stem with optional heartwood (false core).
Cross section through a pine trunk with hoopwood (light heartwood ).
Many tree species heartwood optional and form by external influences (mostly injuries) a so-called false core. However, this has not increased durability and is distinguished by its color often not homogeneous structure. The nuclear materials are formed only in the cell lumen, remains under an impregnation of the cell walls. In the wood using the wrong core usually considered as an optical wood defects and therefore as a value- reducing. It does not affect the strength of wood but.
Mandatory Verkerner (true heartwood trees).
- The pine (Pinus spp.) Is a real heartwood tree. The core ( red ) differs significantly in pine sapwood (white- yellowish). In pine pylons the sapwood is protected with wood preservatives.
- The oak (Quercus spp. ) Is a heartwood tree, in which the split pin in the exterior may not be used untreated, as it is not permanent.
- The very hard and expensive ebony has a deep black core and a bright sapwood.
- Podocarpus is a light but durable heartwood ( hoopwood )
- Spruce (Picea spp. ) Form bright, little permanent heartwood ( hoopwood )
Optional Verkerner ( false core can form ):
- The heartwood of cherry (Prunus avium) is not a true heartwood, but a false core. There is little permanent. Since the difference in color between heartwood (red) and sapwood ( white) is very intense, the sapwood is cut away here for high quality equipment timber.
- The ash (Fraxinus excelsior) often forms an olive nucleus ( " Olive Ash ").
- The beech (Fagus sylvatica) is aged an often cloudy red heart, which was formerly completely undesirable, but today some in furniture as beech heartwood is used.
Due to the present in the heartwood of certain tree species aromatic structures, the so-called tannins / tannins, a distinguishing feature compared to the sapwood is given. This can lead to the direct visual distinctness or be exploited by performing a coupling with diazonium salts to colored products. The "classic " reagent for the detection of pine heartwood are prepared from two components, the solutions A and B.
- Solution A is prepared by mixing 5 g of 25 % HCl is initially introduced, which is prepared from 25 ml of 37% HCl and 12 ml H2O. Then, 1 g of benzidine is ( caution carcinogenic! ) Was added, filled with 200 ml of H2O and homogenized.
--- In place of benzidine should better the sulfanilic acid ( Xi - irritant ) may be used, with only a slight orange color is obtained ---
- Solution B is prepared by mixing 20 g of sodium nitrite ( NaNO2 ) and fills with H2O dissolved in 200 ml.
Directly before use equal parts of the two solutions are mixed. Once applied to the grain surfaces, the heartwood is characterized by a short time by a deep red color.