Compression Wood Tracheids Research Articles

Significance of laricinan in compression wood tracheids

After a β-D-1,3-linked glucan had been isolated from compression wood, identified, and named ‘laricinan’, other researchers suggested that it occupied the helical cavities in the S2 layer of those tracheids. They postulated that the glucan was responsible for the capacity of compression wood to generate the large forces associated with reorientation of displaced stems and branches, and also caused its severe shrinkage with drying.

Helical thickenings and helical cavities in normal and compression woods of Taxus baccata

The longitudinal tracheids in compression wood of Taxus baccata contain helical thickenings but no helical cavities. The thickenings are as frequent and well developed and have the same ropelike appearance as in normal wood of this species. They are an integral part of the S3 in normal and of the S2 in compression wood and have the same orientation as the innermost microfibrils in these layers. Except for the absence of cavities and presence of thickenings, compression wood tracheids of Taxus baccata possess all the anatomical features typical of such cells, including a rounded outline, intercellular spaces, a thick S1 layer, a highly lignified S2 (L) layer, and no S3 layer. Pronounced compression wood of Pseudotsuga menziesii contains helical cavities but no helical thickenings. Thickenings and cavities seem to be mutually exclusive in Pseudotsuga and Taxus.

A comparison of latewood pits, fibril orientation, and shrinkage of normal and compression wood of giant sequoia

Giant sequoia latewood compression wood (CW) tracheids had pit canals that flared toward the lumen with extended poorly defined inner apertures that paralleled the fibrils in the S2 walls. Boiling and drying of CW and normal wood (NW) blocks induced split extensions at the CW pit aperture grooves but not at the NW pit apertures. These split extensions of the CW pit apertures were present also in longitudinal microsections. The mean fibril angle of 21 to 25 degrees of this well-defined CW was appreciably below the 45 degrees frequently reported. The CW tangential/radial shrinkage ratio of about 1 was distinetly lower than NW (1.6 and 2.1), and appeared to be the result of much lower tangential shrinkage. Both NW and CW specimens when dried quickly in an oven at 100° C had higher shrinkage (long., tang. and rad.) than when air-dried first at lower temperature and higher relative humidity.

Studies on compression wood—part VII: Distribution of lignin in normal and compression wood of tamarack [Larix laricina (Du Roi) K. Koch

The distribution of lignin has been studied in tracheids and ray cells of normal and compression wood of tamarack [Larix laricina (Du Roi) K. Koch]. The three layers in the secondary wall of normal wood tracheids are lignified to approximately the same extent, and previous evidence that the S 3 layer should contain a higher proportion of lignin than the other regions has not been confirmed. The lignin follows closely the orientation of the cellulose microfibrils in all three layers. Compared to the tracheids, the ray cells contain a denser network of lignin in their secondary wall. Only a small proportion of the total lignin in compression wood tracheids is present in the compound middle lamella. The thick S 1 layer is only slightly lignified; the orientation of the lignin in this region is that of the transversely oriented, lamellated microfibrils. The outer portion of S 2 consists largely of lignin but also contains lamellae of cellulose microfibrils which probably have the same helical orientation as the microfibrils in the inner part of S 2. The latter region, which contains the helical cavities, consists of lamellae of cellulose microfibrils which are uniformly encrusted with lignin. The ray cells in compression wood appear to be lignified to the same extent as in normal wood. Transverse sections of the cells reveal a lateral orientation of the lignin. The orientation of the cellulose microfibrils in the S 2 layer of the first-formed springwood tracheids of compression wood is the same as in the cells which are formed later. It is suggested that for ease of reference, the outer, lignin-rich layer in compression wood tracheids be referred to as the S 2(L) layer.

Untersuchungen über Druckholzbildung—Erste Mitteilung: Die Verteilung des Lignins im Druckholz von Fichte (Picea rubens Sarg.)

Normal and compression wood from red spruce (Picea rubens Sarg.) and, to a limited extent, balsam fir (Abies balsamea (L.) Carr.) was subjected to treatment with hydrofluoric acid and decay by the brown rot fungiLenzites trabea Persoon ex Fries andLenzites saepiaria Wulfen ex Fries. The texture and distribution of the lignin remaining after these treatments were studied in transverse and longitudinal sections by electron microscopy. In agreement with previous investigations, the lignin in the secondary wall of normal tracheids was found to form a continuous network. The results obtained with compression wood tracheids showed that there was an isotropic layer with a high lignin concentration located immediately insideS 1, but that this region also contained polysaccharides which were probably oriented in a transverse direction with respect to the fiber axis. The inner part ofS 2, containing the helical cavities, had a uniform distribution of lignin in the form of a continuous network. There was no evidence for a radial distribution of lignin in compression wood tracheids nor for the absence of lignin from the inner portion ofS 2, as had been stated by earlier investigators. The polysaccharides in the cell wall of the compression tracheids, and especially those located in the outer part ofS 2, were partially inaccessible to both acids and fungi. The latter penetrated the wood both through the lumens and through the intercellular spaces.Lenzites saepiaria was by far the more efficient of the two fungi used.

The nature of reaction wood. VIII. The structure and differentiation of compression wood

The cell wall organization of tracheids of natural and chemically induced compression wood of Pinus radiata and Actinostrobus pyramidalis has been shown to be the same, and is similar to that established in previous studies of natural compression wood. In the secondary wall only two layers were present. In the second of these there was a well-developed system of helical cavities, separating ribs of cellulose. The ribs of cellulose were parallel to the direction of microfibril orientation; were complex in form; and the cellulose lamellae lay parallel with the wall surface. A well-developed wart structure was present. During the differentiation of compression wood tracheids, the intercellular spaces were formed during the phase of surface enlargement of the differentiating tracheids. At an early stage the intercellular spaces appeared to contain cytoplasmic ground substance. During the development of the layer S1 the cytoplasmic organization was similar to that of normal tracheids, the cells containing a large vacuole with a well-developed tonoplast and plasmalemma. During the development of the layer S2 the cytoplasm contained numerous small vesicles with no large vacuoles, and in many instances the plasmalemma was absent. At the conclusion of the differentiation of the cell the plasmalemma was again present and penetrated the helical cavities of the wall. Compression wood induced by 3-indoleacetic acid (IAA) alone, gibberellic acid (GA) alone, or IAA and GA in combination was identical with that formed under natural conditions. The localized lateral application of IAA to vertical stems caused conspicuous bending of the stem as well as compression wood formation.

Spiral Thickening in Normal and Compression Wood

EXAMINATION of four horizontal branches of each of Taxus baccata L. and Torreya californica Torr. showed the pith eccentric toward the upper side and on the lower side wood similar to compression wood except that the fine spiral striations typical of compression wood tracheids were not visible.