Immunohistochemical localization of enzymes related to lignin biosynthesis in the primary xylem of hybrid aspen

We have investigated the spatial regulation of the accumulation of enzymes involved in the biosynthesis of shikimate and lignin during differentiation of primary xylem from the apical meristem via procambium in hybrid aspen (Populus sieboldii x Populus grandidentata). Immuohistochemical staining revealed that, in the top part of shoots, lignification began in a single or just a few adjacent vessel elements and subsequently spread to neighboring cells. The spatial localization of 3-deoxy-D-arabino-heptulosonate 7-phosphate synthase (DAHPS), which is one of the key enzymes in the shikimate pathway, was tightly correlated with the cell-specific deposition of lignin in the primary xylem. We also found that the spatial localization of enzymes in the general phenylpropanoid pathway and in the lignin-specific pathway was closely associated with the cell-specific deposition of lignin and the accumulation of DAHPS. Our data suggest that enzymes that act in the shikimate, general phenylpropanoid, and lignin-specific pathways are initially produced and function coordinately in a single or a few adjacent elements at the start of primary xylem development.     

Comparison of mechanical properties of tension and opposite wood in <Emphasis Type="Italic">Populus</Emphasis>

In this paper we focused on the differences of mechanical properties of tension and normal wood of 1-year-old poplar trees, artificially tilted. Elastic and fracture properties have been measured and linked to the anatomy. Tension wood is well known because it prevents good surface finishing and leads to difficulties with sawing. We studied three main mechanical properties: young modulus, energy of cutting and longitudinal residual strain of maturation (with strain gauges) because of their importance in wood technology. Moreover, this work takes place in a larger project of study, the phenomena of axes re-orientation in trees (allowing by the production of reaction wood), where these data are required for biomechanical modelling. The results show that tension wood has a higher young modulus, needs a higher energy to be cut and exhibited a higher level of longitudinal residual strain of maturation than those of normal wood. The results suggest that these differences require deeper analysis of the wood than anatomy: measurement of microfibril orientation in the S2 layer and also the lignin composition in monomeric units.     

6种木材白腐菌对山杨材木质素分解能力的研究

由于不同的木材腐朽菌的生理特性不同 ,所分泌的酶及酶的活性各不相同 ,因此 ,不同的腐朽菌分解木材的各种成分及相对速度就各不相同 ,而且对于木质纤维基质会有不同的中间代谢产物。本项研究选择了火木层孔菌 (Phelliusigniarius)及另外 5种木材分解能力较强的阔叶树上的白腐菌 :粗毛盖菌 (Funaliagallica)、三色革裥菌 (Lenzitestricolor)、冬拟多孔菌 (Polyporellusbrumalis)、偏肿拟栓菌 (Pseudotrametesgibbosa)和血红密孔菌 (Pyc noporussanguineus) ,研究了它们对山杨木材木质素的分解能力 ,测定了经 6种白腐菌分解一定时期的山杨木材木质素的含量 ,作为木材白腐菌对山杨木材木质素生物降解机制的初步研究 ,旨在为山杨木材生物制浆造纸提供应用基础理论研究 ,同时也可为木质素合理的生物转化为有用的化学品、生物漂白、酶处理防止机械浆的返黄、废水治理、纤维素酶解糖化的微生物前处理等提供相关的借鉴研究 ,以期在生产实践中减轻环境污染并充分利用木质素资源。在无菌的条件下 ,将山杨木片样品分别放入以上 6种白腐菌的平板培养基中受菌侵染 ,一定时间后取出 ,去除木片表面的菌丝体 ,然后分别测定未腐朽材和受菌侵染 4 0d、6 0d、80d和 12 0d时木片样品中木质素的含量 ,分析 6种白腐菌对山杨木     

杨木应拉木微区结构可视化及化学成分分析

木材微区结构与木材宏观性质密切相关,杨木应拉木与对应木宏观性质存在较大差别,探究杨木应拉木和对应木微区结构和化学成分,可为了解杨木应力木的宏观性质提供理论根据。借助光学显微镜、荧光显微镜、显微拉曼成像光谱仪、透射电镜对杨木应拉木微区结构进行可视化研究,并借助X射线衍射技术和美国可再生能源实验室方法,分析杨木应拉木的微晶尺寸、结晶度以及化学成分。结果表明:杨木应拉木中应拉区和对应区纤维细胞微区结构差异显著。光学显微镜下显示应拉区木纤维中胶质层清晰可见,荧光显微镜和拉曼显微镜下显示胶质层的木质素浓度比对应区低。透射电镜下显示应拉区木纤维细胞壁结构由初生壁、次生壁和胶质层组成,未见次生壁外层,各层的平均厚度分别为0.61,1.22和2.53μm。对应区木纤维为典型的初生壁和次生壁结构,次生壁各层平均厚度分别为0.33,2.28和0.14μm。杨木应拉区纤维素含量(58.91%)比对应区(41.53%)高,木质素含量和半纤维素含量均比对应区的低,应拉区木质素和半纤维素含量分别为21.99%和12.01%,对应区分别为28.10%和17.08%。杨木应拉区结晶度(48.06%)比对应区(41.01%)高,应拉区晶区宽度为2.66 nm,长度为8.84 nm;对应区晶区宽度为2.65 nm,长度为9.87 nm。     

Occurrence and significance of bacteria in living trees of Populus nigra L.

On the occurrence and significance of bacteria in living trees of Populus nigra L. Eleven strains of bacteria were isolated from sapwood and heartwood of living poplar trees (Populus nigra L.) and identified mostly as Erwinia, Xanthomonas, Agrobacterium and Acinetobacter. Most of them were able to attack milled wood and the wood components pectin, hemicelluloses and holocellulose; α-cellulose and lignin were not consumed. The capillary liquid in the xylem of poplar served as a nutrient for the isolated bacteria. The significance of these bacteria for wetwood formation is discussed.     

林下耕作对滩地杨树木材物理力学性质的影响研究

本文对长江滩地这一特定立地条件下经过人为耕作与非耕作模式下的杨树木材物理力学性质及应力木分布情况与力学性质间的关系进行了比较研究。结果表明：林下耕作可提高杨树木材密度,与对照木相比,基本密度和气千密度差异性分别达显著与极显著水平;能够减少应拉木的产生,与对照木相比差异百分率达24．82％,进而使木材的差异干缩减小,木材尺寸稳定性提高;各项力学指标均优于对照杨树,且与应力木的量呈线性负相关,其中抗弯强度与抗弯弹性模量与其相关性显著。     

Reaction wood anatomy and lignin distribution in <Emphasis Type="Italic">Gnetum gnemon</Emphasis> branches

This study investigated the anatomical and chemical characteristics of the reaction wood of a gymnpsperm species, Gnetum gnemon, and discussed on contributing factor for the type of reaction wood in this species. Cell morphology, microfibril angle (MFA) of the S₂ layer and lignin distribution in secondary walls of tracheary elements, and lignin content were examined on three branches. Observations included no G-layer formation, significant decreases in vessel frequency, and altered MFA, and visible-light absorbance after lignin colour reactions in tracheid and fiber tracheid walls on the upper side in almost all samples. These results suggest that reaction wood in G. gnemon was similar to that in ‘tension-wood-like-reaction wood’ in angiosperms. On the other hand, reaction wood showed decrease in the lignin concentration in the fiber tracheid walls compared to the tracheid walls. In addition, the lignin in the tracheid and fiber tracheid walls was originally rich in syringyl units, suggesting that changes in the anatomical and chemical characteristics of secondary xylem due to reaction wood formation might relate to the ratio of the syringyl to guaiacyl units in lignin in the cell walls which function for mechanical support.     

Fluid permeability in poplar tension and normal wood in relation to ray and vessel properties

The impact of ray and vessel features on the radial air permeability and liquid penetration was compared between poplar (Populus nigra) tension and normal wood. Air permeability was measured by the falling-water volume-displacement method. To measure liquid penetration, specimens were saturated with safranin solution by the full-cell process at low pressure, and the pattern of red color penetration was then examined. Results revealed no significant difference in vessel frequency, intervessel and vessel-ray pit diameter between tension and normal wood, whereas porosity and average vessel lumen area in normal wood were significantly greater than those in tension wood. Regarding rays, their length was not different between normal and tension wood, but the latter had more frequent rays per millimeter. Since xylem rays are important flow conduits in lateral movement of fluids, it could be hypothesized that a larger number of rays in tension wood would lead to improved radial permeability. However, neither air permeability nor liquid penetration varied significantly in the studied specimens. Consequently, the results proved that ray frequency has no determining role in radial fluid flow in poplar tension and normal wood and that the share of intervessel and vessel-ray pits in radial permeability is more important.     

Lignification and peroxidase in tension wood ofEucalyptus viminalis seedlings

Seedlings ofEucalyptus viminalis were grown for 50 days with their stems bent so tension wood would form. Every 10 days the lignin content, monomeric composition, and peroxidase activity in the tension wood were compared with those in the lower side (opposite wood) and in vertically grown controls. The lignin content in the developing tension wood started to decrease after 10 days of bending and kept decreasing for 50 days, whereas those in control plants and opposite wood remained almost unchanged. The yields of syringaldehyde from tension wood by nitrobenzene oxidation increased, and consequently the syringyl/ guaiacyl ratio of the lignin was higher in tension wood than in opposite wood and control plants. The peroxidase ionically bound to the cell walls (IPO) catalyzed oxidation of guaiacol and syringaldazine. The syringaldazineoxidizing activity of IPO from tension wood increased, whereas the activities of IPO from opposite wood and control plants did not show any marked change. In tension wood the increase in syringaldazine-oxidizing activity of IPO was consistent with an increase in the syringaldehyde yield. This suggests that IPO contributes to syringyl lignin deposition as other enzymes involved in the monolignol biosynthesis do in tension wood formation.This study was presented at the 50th Annual Meeting of the Japan Wood Research Society, Kyoto, April 2000     

生物处理杨木制浆造纸的初步研究

利用白腐菌对杨木片进行生物处理并制浆造纸，研究结果表明，白腐菌Ｃ．ｖ．Ｎｏ．１、Ｃ．ｖ．－Ｎｏ．２对杨木片显示出较强的木素分解能力，经生物处理后的木片用于制浆造纸，纸的物理性能，如白度，裂断长，伸长率等项指标都高于未经生物处理木片抄纸的指标，同时用生物处理的杨木木片的化学浆时其蒸煮时间仅为未处理木片蒸煮时间的一半。     

Lignin deposition during earlywood and latewood formation in Scots pine stems

Lignin deposition at consecutive secondary wall thickening stages of early and late xylem cells during annual ring wood formation in Scots pine (Pinus sylvestris L.) stems was studied. Lignin patterns, isolated by thioglycolic acid method, consisted of alcohol-soluble (LTGA-I) and alkali-soluble (LTGA-II) fractions. The sum of two fractions, being the total lignin content, gradually increased in the course of lignification. However, the increments of lignin amount at each development stage of early and late tracheids were different. The intensity of lignin deposition increased in the course of earlywood tracheid maturation and decreased toward the end of latewood cell differentiation. The deposition of two lignin fractions in each layer of forming wood also occurred oppositely. The increment of LTGA-I descended, whereas that of LTGA-II increased from the beginning to the end of early xylem lignification. In contrast, LTGA-I increment dropped, whereas LTGA-II rose during late xylem lignification. Gel permeation chromatography showed that the lignins, formed at the beginning of lignification, were more homogeneous and had higher molecular weight compared with the lignins at the end of cell differentiation. Besides, the content of cellulose, estimated as the residue after lignin isolation, and of cell wall substances, presented as cell wall cross-section areas, at consecutive maturation stages of early and late xylem cells have been found to be different. The data show that lignin deposition occurred in different conditions and with opposite dynamics during early and late xylem formation.     

A statistical analysis of the impact of nematode attack symptomatology on the mechanical behaviour of <Emphasis Type="Italic">Pinus pinaster</Emphasis> Ait. wood

An appraisal was made about the impact of pinewood nematode (Bursaphelenchus xylophilus, Nickle) attack symptomatology on the mechanical behaviour of wood from Pinus Pinaster Ait. Two sets of 200 wood specimens were obtained for the study of both mechanical and other physical properties. The specimens, about half of which presented symptoms of nematode, were obtained from a set of 66 wood planks, cut from an equal number of trees, originating from the Setúbal Peninsula (Portugal). Logistic analysis using symptomatology as a binary dependent variable showed adequacy of models containing compression tension to rupture and number of wood rings per unit radial length for the prediction of nematode attack. Analysis of variance revealed that the presence of the disease symptoms was correlated to static bending rupture, modulus of elasticity, work to maximum bending load, and axial compression rupture, causing their decrease at a significance level of 5%.     

Distribution of lignin and lignin precursors in differentiating xylem of Japanese cypress and poplar

Lignin is an integral component of the cell wall of vascular plants. The mechanism of supply of lignin precursors from the cytosol into the cell wall of differentiating xylem has not yet been elucidated. The present study showed that a certain amount of coniferyl alcohol glucoside (coniferin) occurred in the differentiating xylem of Japanese cypress (Chamaecyparis obtusa), as previously reported in gymnosperms. Coniferin content peaked in the early stages of secondary wall formation and decreased during lignification. In contrast to gymnosperms, coniferin content was limited in the differentiating xylem of poplar (Populus sieboldii × Populus grandidentata). Moreover, coniferyl alcohol was not detected in all specimens. In the differentiating xylem of poplar, a higher amount of sinapyl alcohol occurred than glucoside (syringin). However, the phloem contained syringin and not sinapyl alcohol. The sinapyl alcohol content in the xylem peaked in the cells with ceasing cell wall formation, and decreased gradually towards the boundary of the annual ring, where the lignin content kept increasing. Sinapyl alcohol in the differentiating xylem of poplar may be used for the lignification of the xylem.     

Ultraviolet microspectrophotometric investigation of the distribution of lignin in Prunus jamasakura differentiated on a three-dimensional clinostat

To examine the effect of gravity on lignin content and deposition in plant cells, we used ultraviolet (UV) microspectrophotometry and chemical methods to investigate the secondary xylem of Prunus jamasakura grown on a three-dimensional (3D) clinostat, which simulates microgravity. The stem of the 3D-clinostat specimens elongated with bending and the width of their secondary phloem increased. The UV absorbance of the 3D-clinostat specimens at 278 nm was higher than that of the control specimens, which were grown on the ground, in the wood fiber cell corner middle lamella, compound middle lamella, and fiber secondary wall; the UV absorbance in the vessel secondary wall did not differ between the specimens. The lignin content in the stem, including the bark, of the 3D-clinostat specimens, as determined using an acetyl bromide method, was less than that of the control specimens. In the specimens that differentiated on a 3D clinostat, the amount of lignin in the wood fibers increased, while the proportion of the lignified xylem in the stem decreased relative to control values.     

Characterization of Brauns’ lignin from fresh and vacuum-dried birch (Betula pendula) wood

Brauns’ lignins present in the methanol extracts of fresh birch (Betula pendula) xylem and of sawn birch board subjected to vacuum drying were characterized by ¹H and ¹³C NMR spectroscopy (1D and 2D), IR spectroscopy, gel permeation chromatography (GPC) and colour measurements (CIELab) in order to find out whether Brauns’ lignin could contribute to the colour change of sawn timber that occurred during vacuum drying. The two Brauns’ lignin samples contained about equal amounts of syringylpropane and guaiacylpropane units linked with β-O-4 and β–β side-chain structures. Molecular weight of the Brauns’ lignin of vacuum-dried birch board (acetylated: 5,200 g mol⁻¹) was higher than that of the Brauns’ lignin of fresh birch wood (acetylated: 4,400 g mol⁻¹). The Brauns’ lignin of vacuum-dried wood was also clearly darker and more prominently yellow and red; between the Brauns’ lignin samples was 23.59. The differences in the molecular weights and colours suggest that the Brauns’ lignin underwent a chemical change during vacuum drying of the wood and that this change may have affected the colour of the wood.     

Study on the changes in surface characteristics of <Emphasis Type="Italic">Populus tomentosa</Emphasis> due to thermo-hydro-process

The effects of high temperature, moisture, and mechanical action during the thermo-hydro-mechanical (THM) processing, on the changes in surface properties of poplar, namely, surface color, roughness, wettability, and microstructure, were investigated in this study. The correlation between observed changes in surface properties and chemical characteristics was also analyzed. Poplar woods with high moisture content were compressed using different pressures at temperature of 160 °C for four different periods. The wood surfaces became darker and smoother, and their surface free energy decreased significantly after the THM process. THM process markedly reduced surface hygroscopicity compared to the control wood. The cell lumens of THM wood became narrow with increasing compression ratio due to the enhancing high pressure. Collapse and fractures of cell walls developed during THM treatment. Furthermore, results indicated that a series of chemical reactions in different components of wood took place during THM process, such as degradation of hemicelluloses, condensation of lignin, and decomposition of extractives. In turn, these chemical modifications contributed to the darkening of color as well as the reduction of wettability and surface free energy of THM wood.