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Wood in wet environments is attacked and degraded by soft rot fungi and erosion and tunnelling bacteria, which are more tolerant to high moisture and reduced oxygen conditions than basidiomycetes, such as white and brown rot fungi. Since wood decaying basidiomycete fungi are normally more aggressive and can degrade wood faster than soft rot fungi and bacteria, wood in wet environments can survive for a relatively long time. Archaeological investigations show that wood buried deep in ocean sediments can survive for hundreds and even thousands of years. In this review degradation patterns of various types of microbial wood decay are briefly described, and examples of decay type(s) in wood exposed in various wet environments presented. It is important to understand biological wood decay in wet environments in order to find appropriate ways to prolong woodʼs service life and properly restore wooden artefacts.

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In: IAWA Journal

There is little information about the ultrastructural changes taking place in the radial walls of fusiform cambial cells during differentiation into xylem derivatives. The present study reports the early events occurring in the radial walls of fusiform cambial cells (FCCs) during fiber elongation in Holoptelea integrifolia, a deciduous tropical tree with storied cambium. Serial tangential sections of active cambial zone cells demonstrate the initiation of intrusive cell wall elongation from gabled ends of FCCs during fiber development. The elongation at the tip is followed by the axial extension of the entire cell. It was evident from ultrastructural observations made on the tangential sections that the thick beaded pattern on FCC radial walls disappear following cell elongation. PATAg staining, specific for wall polysaccharides showed that, initially, the beaded structures undergo wall loosening following hydrolysis of pectic polysaccharides in the middle lamella. Then the loosened primary walls come together with the axial extension of cells. Thus the beaded nature disappears in the differentiating cambial cells. This study highlights the cell wall changes associated with the differentiation of FCCs into fibers.

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In: IAWA Journal

Transmission electron microscopy of Terminalia archaeological wood from an ancient Polynesian canoe showed vestures to be intact despite extensive degradation of the secondary wall by erosion bacteria. The vesture wall consisted of a lining wall resistant to degradation and an underlying wall which was partly degraded. These observations provide evidence for inhomogeneity in the composition of Terminalia vesture walls.

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In: IAWA Journal

Sequential changes occurring in cell walls during expansion, secondary wall (SW) deposition and lignification have been studied in the differentiating xylem elements of Holoptelea integrifolia using transmission electron microscopy. The PATAg staining revealed that loosening of the cell wall starts at the cell corner middle lamella (CCML) and spreads to radial and tangential walls in the zone of cell expansion (EZ). Lignification started at the CCML region between vessels and associated parenchyma during the final stages of S2 layer formation. The S2 layer in the vessel appeared as two sublayers,an inner one and outer one.The contact ray cells showed SW deposition soon after axial paratracheal parenchyma had completed it, whereas noncontact ray cells underwent SW deposition and lignification following apotracheal parenchyma cells. The paratracheal and apotracheal parenchyma cells differed noticeably in terms of proportion of SW layers and lignin distribution pattern. Fibres were found to be the last xylem elements to complete SW deposition and lignification with differential polymerization of cell wall polysaccharides. It appears that the SW deposition started much earlier in the middle region of the fibres while their tips were still undergoing elongation. In homogeneous lignin distribution was noticed in the CCML region of fibres.

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In: IAWA Journal

Abstract

The bacterial decay of waterlogged archeological wood (WAW, hard pine spp.) taken from Daebudo shipwreck No. 2, which was buried in the intertidal zone in the mid-west coast (Yellow sea) of South Korea approximately 800 years ago, was investigated. The maximum moisture content of the outer parts (approx. 3 cm of depth) of WAW was approximately 4.2 times higher than that of undegraded reference pine wood. ATR-FTIR and solid-state 13C-NMR analysis indicated a relative increase of the lignin concentration in WAW caused by the degradation of cellulose and hemicelluloses across the board studied (31-cm-wide and 14.5-cm-thick board). Micromorphological studies also revealed that bacterial degradation was progressed to a depth of 15 cm (vertically 7.3 cm) from the surface, which is the innermost part of the board. Erosion bacteria (EB) were identified as the main degraders of WAW. Degradation by tunneling bacteria (TB) was occasionally detected. Decay resistance to bacterial attacks in WAW varied between cell types and between cell wall regions. Axial tracheids showed less resistance than ray tracheids, ray parenchyma cells, and axial intercellular canal cells, including strand tracheids, subsidiary parenchyma cells, and epithelial cells. Decay resistance was higher in ray tracheids and strand tracheids than in ray parenchyma cells and subsidiary parenchyma-/epithelial cells, respectively. Bordered- and cross-field pit membranes and the initial pit borders showed higher decay resistance than the tracheid cell walls. Overall, the S2 layer of the axial tracheids showed the weakest resistance to bacterial attacks.

In: IAWA Journal

Two inachid crabs, Paratymolus pubescens Miers, from Geomundo and Litosus sexspinosus (Miers, ) from Jeju Island, are briefly described here. The two species are unique representatives of their respective genera in local waters. Morphological and distributional accounts of these species are discussed.

In: Crustaceana

Studies on the compression wood in tropical gymnosperms are uncommon due to their limited distribution and over-exploitation. Microscopic examination of the heartwood of two tropical gymnosperms, Agathis borneensis (local name: bindang, damar minyak) and Dacrydium elatum (local name: sempilor) growing on higher elevations in Sarawak, Malaysia showed the occurrence of mild compression wood. Intercellular spaces were present in the compression wood of A. borneensis, but not in D. elatum. Rounded shapes of tracheids, typical of severe compression wood, were not observed in any of the samples examined. In D. elatum helical cavities were present, which corresponded in location to cell wall checks seen in cross-sectional views. The S1 layer was relatively thick in both wood species but a distinct S3 layer was observable only in the mild compression wood of D. elatum. Although the main feature of the mild compression wood tracheids of both wood species was greater lignification of the outer S2 region, autofluorescence and KMnO4 staining showed the fluorescence and staining intensity in the corner middle lamella in some cases to be much stronger than that in the outer part of S2 layer.

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In: IAWA Journal

Naturally durable heartwoods, where available, continue to be used as support structures in environments considered hazardous, particularly in ground contact. However, durability of heartwoods against wood decay microorganisms varies. Therefore, it is important to evaluate heartwood products for their in-service performance in order to maximise benefits derived from this valuable natural resource of limited supply. In the work presented, wood pieces from a kempas (Koompassia malaccensis) utility pole that had been placed in service in an acidic soil in Malaysia, and in time had softened at the ground-line position, were examined by light and transmission electron microscopy to evaluate the cause of deterioration.

Light microscopy (LM) provided evidence of extensive attack on fibre cell walls by cavity-producing soft rot fungi. Transmission electron microscopy (TEM) revealed in greater detail the distribution and micromorphologies of cavities as well as their relationships to the fine structure of fibre cell walls, which consisted of a highly electron dense middle lamella, a moderately dense S1 layer and a multilamellar S2 layer with variable densities, reflecting differences in lignin concentration. The resistance of the moderately dense S1 layer to soft rot was a feature of particular interest and is the main focus of the work presented. The resistance appeared to be correlated with high lignification of the outermost region of the S2 wall, interfacing with the S1 layer, an unusual cell wall feature not previously described for normal wood.

In: IAWA Journal

ABSTRACT

This review presents information on the relationship of ultrastructure and composition of wood cell walls, in order to understand how wood degrading bacteria utilise cell wall components for their nutrition. A brief outline of the structure and composition of plant cell walls and the degradation patterns associated with bacterial degradation of wood cell walls precedes the description of the relationship of cell wall micro- and ultrastructure to bacterial degradation of the cell wall. The main topics covered are cell wall structure and composition, patterns of cell wall degradation by erosion and tunnelling bacteria, and the relationship of cell wall ultrastructure and composition to wood degradation by erosion and tunnelling bacteria. Finally, pertinent information from select recent studies employing molecular approaches to identify bacteria which can degrade lignin and other wood cell wall components is presented, and prospects for future investigations on wood degrading bacteria are explored.

In: IAWA Journal