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1.
Summary Hemlock sawdust samples degraded by Ganoderma applanatum showed no electron-dense particles either in hyphae or in wood cell walls after aldehyde/OsO4 fixation. After KMnO4 fixation at early stage of attack, particles were in hyphae, hyphal sheath and wood cell walls. In samples prepared by a cytochemical technique which localizes cellulase activity at the ultrastructural level, particles were in hyphae, hyphal sheath and wood cell walls. The smallest diameter range of the particles lay between 3 and 7 nm which corresponds to the size of cellulases. Larger diameter particles were peresent which are probably aggregates of the smaller units. We believe that particles present in hyphal cytoplasm and hyphal sheath are cellulolytic enzymes. Whether particles present in attacked wood cell walls are enzymes or degradation products cannot be determined by this study. Nevertheles, the particles reveal the decay pattern in wood by the white-rot fungus G. applanatum.  相似文献   

2.
A normal variety of rice (Oryza sativa L.cv. Taichung 65, T65c), its isogenic dwarf line (T65d 1), and a semidwarf variety of a different line (Oryza sativa L.cv. IR8, IR8) were studied. The results were compared with those of an isogenic dwarf line (Rh i) of wheat straw, which was previously reported. Expression of the dwarf gene,d 1, on the chemical composition and the structural features of lignin present in rice internodes differs from that in an isogenic dwarf line of wheat. The differences include the lignin content, total yield of alkaline nitrobenzene oxidation products, and distribution of wall-bound hydroxycinnamic acids. There was, however, no difference in the syringyl/ guaiacyl nuclei (S/V) molar ratio and neutral sugar composition. The lignin composition of rice straw cell walls, particularly that of the dwarf variety, contained more of the condensed structure and fewer syringyl nuclei than lignin in wheat straw cell walls. It is suggested that crosslinking between lignin and polysaccharides by ester-ether bridges via ferulic acid contributes to the mechanical properties of the cell walls of rice straw. Thus the chemical and structural characteristics of lignin in rice straw differ to some extent from those of other temperate grasses, such as wheat (Triticum aestivum) and phalaris (Phalaris aquatica), as reported previously. This can probably be attributed to the water environment of rapidly growing rice seedlings, but it also depends on the genetic variety of the rice plant.  相似文献   

3.
In vitro laboratory decay tests on Ailanthus excelsa Roxb. wood revealed that I. hispidus exhibits a combination of both white-rot and soft-rot patterns of wood decay. Early stages of wood decay showed dissolution of the middle lamella as well as defibration and localized delignification of fiber walls; vessels, axial, and ray parenchyma remained unaltered. Delignification commenced from the middle lamellae at the cell corners without any marked effect on the primary and secondary wall layers. In later stages of growth, the species produces typical soft-rot decay pattern by forming erosion channels through the S2 layers of fiber walls, transverse bore holes in the cell walls, and erosion channels alongside/following the orientation of cellulose microfibrils. The rays showed signs of cell wall alterations only after the extensive damage to the fiber walls. After 120 days of incubation, the vessels also showed localized delignification, the erosion of pits, and separation from associated xylem elements. The extensive weight losses under natural and in vitro decayed wood as well as the very soft nature of severely degraded wood indicate that I. hispidus alters wood strength and stiffness.  相似文献   

4.
Summary Microscopic and electron microscopic examination of the resin canal complex isolated from slash pine chlorite holocellulose showed it to be composed of thin-walled, unlignified tissue apparently without secondary thickening. The mature structure consisted of a central canal surrounded by three cellular layers. Epithelium forms the inner layer while the middle and outer layers consist of short (intermediate) and elongated (outer) parenchyma cells, respectively. In contrast to previous concepts, the middle lamella of these tissues is a complex structure which contains intercellular membranes and cellulosic and noncellulosic (probably galacturonan) intercell wall fibrils. Intercellular membranes encapsulate two or more cells and consist of one or more intact ancestral walls The number and total thickness of ancestral walls in the mature middle lamella vary with the number of cell divisions and the location of the cell plates within a fusiform cambium daughter cell. The development of the canal complex and of the ray tissue associated with it can be traced by studying the cell wall ultrastructure.Symbols used in Figures A Canal complex axis - Ar Artifact - C Cytoplasmic remnant - CS Canal complex surface - D Canal - E Epithelial cells - F Intercell-wall fibrils - I Intermediate cells - L Cell lumen - M Intercellular membrane - M 1 Intercellular membrane - M 2 Intercellular membrane - M 3 Intercellular membrane - ML Middle lamella - O Outer cell - P Primary cell wall - PL Part of an ancestral wall partially pulled from the canal complex surface - T Thin-walled portion of an epithelial cell - x Cleavage within middle lamella - y Cleavage along middle lamella-primary wall boundary The authors thank Drs. I. H. Isenberg and L. L. Winton, members of the thesis advisory committee, for their assistance in the conduct of the research, Miss Olga Smith for assistance in electron microscopy and for drawing Figs. 1, 5, and 7, and J. D. Hankey for assistance in photomicroscopy.  相似文献   

5.
Summary Anatomical features of reaction wood formed in two Magnolia species, M. obovata Thunb. and M. kobus DC. which are considered to be among the primitive angiosperms, were observed. In addition, the distribution of guaiacyl and syringyl units of lignins in the cell walls of normal and reaction wood was examined using ultraviolet (UV)- and visible light (VL)- microspectrophotometry coupled with the Wiesner and M?ule reactions. The two Magnolia species formed a tension-like reaction wood without possessing the typical gelatinous layer (G-layer) on the upper side of the inclined stem or branch, in which a radial growth promotion occurred. Compared with the normal wood, the reaction wood had the following anatomical features: (1) the secondary walls of fiber tracheids lacked the S3 layer, (2) the innermost layer of fiber-tracheid walls showed a small microfibril angle, a fact being similar to the orientation of the microfibril angle of the G-layer in tension wood, and (3) the amounts of lignin decreased in the cell walls of fiber tracheids, especially with great decrease in proportion of guaiacyl units in lignins. In addition, VL-microspectrophotometry coupled with the Wiesner and M?ule reactions adopted in the present study showed potential to estimate the lignin contents in the cell walls and the proportion of guaiacyl and syringyl units in lignins. Received: 15 July 1998  相似文献   

6.
Degradation of cell walls in elm wood tissue (Ulmus americand) by aggressive and non-aggressive isolates of Ophiostoma ulmi was studied by scanning electron microscopy. Xylem vessel walls were much more affected after infection with the aggressive isolate than after infection with the non-aggressive one.  相似文献   

7.
Summary A study of the wood-inorganic composites prepared by the sol-gel process with a metal alkoxide indicated that an inorganic modification of wood with TiO2 gels from tetraisopropoxytitanium (TPT) can not improve its properties due to the formation of the gels in the cell lumina by high hydrolysis rate of TPT. In this study, therefore, titanium alkoxides or titanium chelates which have the lower rate of hydrolysis and subsequent polycondensation than TPT were used for preparing TiO2 wood-inorganic composites to study the topochemical effects of the TiO2 gels for the property enhancement of wood. As a result, it was found by SEM-EDXA analysis that the TiO2 gels deposited within the cell walls could improve the properties of wood in dimensional stability and fire-resistance, whereas for the gels in the cell lumina, property enhancement could not be achieved, as observed in SiO2 wood-inorganic composites.This research has been performed in Dept. of Wood Sci. & Technol., Kyoto UniversityThis research was supported by a Grant-in-Aid for Scientific Research (B) (No. 06453176, 1994.4–1996.3) from the Ministry of Education, Science, and Culture, Japan. The authors were grateful to Nippon Soda Co., Ltd. for providing titanic reagents.  相似文献   

8.
The decay pattern in bamboo fibers caused by a brown rot fungus, Gloeophyllum trabeum, was examined by microscopy. The inner part of the polylaminate secondary wall was degraded, while the outer part of the secondary wall remained essentially intact. Degradation in bamboo fiber walls without direct contact with the fungal hyphae was similar to wood decay caused by brown rot fungi. Degradation in polylaminate walls was almost confined to the broad layers whereas the narrow layers appeared resistant. The p-hydroxylphenyl unit lignin in middle lamella, particularly in the cell corner regions, was also degraded. The degradation of lignin in bamboo fibers was evidenced by Fourier transform infrared spectra. The present work suggests that the decay of bamboo fiber walls by G. trabeum was influenced by lignin distribution in the fiber walls as well as the polylaminate structures.  相似文献   

9.
Microscopic examination showed the cell wall decay pattern produced by the brown-rot fungus Coniophora puteana to be different from the degradation pattern known to be typical for brown-rot fungi. Erosion and thinning of cell walls in patterns considered to be characteristic of white-rot decay were observed. In particular, the fungal strain COP 20242 degraded secondary cell wall layers extensively, and also degraded lignin-rich middle lamellae. Some strains of C. puteana produced soft-rot type cavities in the S2 layer. All strains of C. puteana employed in the present work showed a positive reaction to tannic acid in the Bavendamm test, indicating the production of laccase. Microscopic and enzymatic studies provided evidence to suggest that the wood decay by C. puteana is unique both in terms of micromorphological and enzymatic patterns of cell wall degradation. This is because brown-rot fungi are not generally known to form cavities in the cell walls or to produce lignin-degrading enzymes. These observations suggest that lignin degradation capacity of brown-rot fungi may be greater than previously considered.  相似文献   

10.
The structural changes in the cell wall and delignification pattern caused by Trametes versicolor and Trametes hirsuta in the sap wood of Leucaena leucocephala were examined by light and confocal laser scanning microscopy. The in vitro decay test was conducted for 12 weeks. Both species of Trametes used in this study caused anatomical characteristics specific to simultaneous white rot. Formation of boreholes, erosion troughs, erosion channels with U-shaped notches in tangential sections and thinning of cell walls were evident in the wood inoculated with each of the fungal species. Cell separation due to removal of middle lamellae occurred at the early stages of infection (30 d) with T. versicolor. In contrast, middle lamellae remained intact in wood inoculated with T. hirsuta and showed cell separation due to degradation of the outer layer of the secondary wall and degradation of the middle lamellae observed only in severely decayed wood at late stages. Confocal microscopy revealed the delignification pattern particularly from cell corners and vessel walls at an advanced stage of decay, indicating strong ligninolytic activity of both species in the sapwood of L. leucocephala.  相似文献   

11.
To investigate micropores and mesopores in the cell walls of dry wood, CO2 gas and N2 gas adsorption onto dry wood were measured at ice-water temperature (273 K) and liquid nitrogen temperature (77 K). CO2 gas adsorption isotherms obtained were used for determining micropore volumes smaller than 0.6 nm by the HK method (Horvath-Kawazoe method), and N2 gas adsorption isotherms obtained were used for determining the mesopore volume between 2 nm and 50 nm by the Barrett-Joyner-Halenda (BJH) method. Micropores and mesopores existed in cell walls of dry wood, and the cumulative pore volume was much larger for micropores than for mesopores. Micropores in the cell wall of dry wood decreased with elevating heat treatment temperature, and the decreased micropore was reproducible by wetting and drying. Mesopores did not decrease so much with elevating heat treatment temperature. Micropore volumes for the softwood Hinoki and the hardwood Buna were compared. A larger amount of micropores existed in hardwood Buna than in softwood Hinoki, and this relationship was considered to correspond to the difference in thermal softening properties for lignin in water-swollen Hinoki and Buna. This result probably indicates that micropores in the cell walls of dry wood relate to the structure of lignin.  相似文献   

12.
Summary Myrothamnus flabellifolia Welw., Eragrostis nindensis Fic. and Hiern, Xerophyta villosa, Th. Dur and Schinz, and Sporobolus stapfianus Gand, present a so-called resuscitation behaviour when subjected to drought and subsequent rehydration. Absence of cell wall cracking is one, if not the main cause of this behaviour. Polyflavonoid tannins content of Myrothamnus flabellifolia is high and increases under drought-induced stress. It does not increase in the other plants where a surge of the content of the amino acid proline occurs instead. The authors now present the hypothesis and circumstantial evidence that the helicoidal tridimensional structures of these tannins function as the springs disallowing cracking of the cell walls and rendering possible the resuscitation characteristics of Myrothamnus flabellifolia and of the other plants through two slightly different mechanisms. This explains why many trees originally of Southern Africa, a drought area, are high producers of tannins. It infers that tannins are structural wood components just as much as cellulose, hemicelluloses and lignin.  相似文献   

13.
For enhancing fire-resistant properties, a binary system to prepare wood-inorganic composites was studied by adding sodium methoxide (SM) or sodium acetate (SA) to a reaction system for SiO2 composites. Compared with the SiO2 composites, both the Na2O-SiO2 composites prepared could be greatly improved up to 600°C-700°C (glowing). From scanning electron microscopic observations, this enhanced fire resistance was assumed to be due to chemical and physicochemical effects, such as dehydration and carbonization of wood by Na2O gel. The glassy layer and intumescent structure formed over the cell walls were thought to prevent oxidation and heat transfer from proceeding into the inner portion of the wood cell walls. However, the reaction medium with SM to prepare Na2O-SiO2 composites was basic, whereas that with SA was rather neutral. In addition, in the latter composites, most of the inorganic gel was formed within the cell wall, retaining the porous structure characteristic of wood. Therefore, the Na2O-SiO2 composites prepared with SA can be concluded to be preferable for practical purposes.Part of this report was presented at the 50th annual meeting of the Japan Wood Research Society, Kyoto, April 2000  相似文献   

14.
Summary There is evidence showing that lignification causes both an increase in the thickness of the walls, and changes in the overall width or circumference of wood cells. Although data are not available on changes in length during lignification, it can be deduced that these must also tend to occur. As lignin occupies sites in the cell walls corresponding to those occupied by water, the theory of anisotropic shrinkage of wood may be used to predict the proportional dimensional changes tending to occur as each wall layer in a compression wood cell is lignified. Taking account of the microfibril angles in those layers, it is shown that if the angle for S2 is more than about 45°, inevitably S2 will tend to develop deep helical fissures or splits of the form of those reported in the literature.  相似文献   

15.
 Relationships between cell and pulp properties were investigated by examining the within-tree property variations in Eucalyptus camaldulensis and Eucalyptus globulus. Properties investigated included proportions of ray and axial parenchyma, thickness of cell walls and cell wall percentages. The characteristics of the ray and axial parenchyma (their proportions and wall thickness) were found to have a significant influence on all measured pulp properties, including paper strength properties. Multiple regression of pulp properties in relation to cell properties revealed that nearly all measured pulp properties were explained by cell properties at the 1% significance level. It was concluded, therefore, that all cell types are important for predicting pulp properties, and it is strongly recommended that tree breeding programs for Eucalyptus include the measurement of all cell types. Received 6 July 1999  相似文献   

16.
Polygalacturonase, Xylanase and Cellulase in Seiridium cardinale grown on cypress cell walls and on infected cypress shoots were detected. Isoenzymes were resolved by isoelectric focusing and differences were found between “in vivo” and “in vitro” patterns.  相似文献   

17.
The effect of ultraviolet-visible light irradiation on changes in surface chemistry and morphology of moso bamboo (Phyllostachys pubescens Mazel) was investigated. Fourier transform infrared (FT-IR) and FT-Raman spectroscopy were used in combination to study chemical changes induced by exposure to artificial sunlight (xenon lamp) for up to 160 h, and the resulting physical changes of cell walls of bamboo surfaces were examined by scanning electron microscopy (SEM). FT-IR results showed that significant changes occurred in the lignin component as indicated by considerable decreases in the intensities of the characteristic aromatic lignin peak at 1512 cm−1 and other associated bands. This was accompanied by formation of new carbonyl groups at 1735 cm−1, resulting in photooxidation of bamboo surfaces. The photosensitive nature of bamboo lignin was also demonstrated by FT-Raman analysis, in which obvious decreases in intensities of Raman bands at 1604 and 1630 cm−1 mainly derived from lignin and free and esterified p-coumaric and ferulic acids were observed. SEM micrographs of the irradiated cross sections of bamboo revealed that significant damage occurred to the fiber walls, whereas the parenchyma cells exhibited slight distortion and some cracks occurred in the cell walls. The structures of cell corners and middle lamellae were nearly intact after irradiation.  相似文献   

18.
Biomorphous Eu3+-doped Y2O3 was fabricated by replication of wood templates using vacuum-assisted infiltration of a water-based sol–gel mixture and subsequent calcination at 750°C. The precursor sols were prepared from (Y0.95Eu0.05)2O3 dissolved in 10 vol% nitric acid and adding citric acid as the chelating agent. X-ray powder diffraction analyses and Rietveld refinements confirmed that the calcined samples were solely composed of bixbyite Y2O3:Eu3+ phase with a mean crystallite size of 16 nm. Scanning electron micrographs and cathodoluminescence imaging showed that the cellular preform anatomy was retained and that the original wood cell walls were completely transformed into phosphor struts with pore sizes ranging from 5 to 20 μm. The optical properties of the biomorphous phosphor materials were analyzed by photoluminescence spectroscopy and assigned to the characteristic Eu3+ (4f6 → 4f6) electric dipole or magnetic dipole transitions. From fluorescence lifetime measurements, the mean lifetime was calculated as 1.62 ms.  相似文献   

19.
Summary The lignification process in different morphological regions of loblolly pine tracheids was studied by the SEM-EDXA technique. Prior to S2 layer formation, lignification was initiated in the cell corner middle lamella and compound middle lamella regions. Subsequently a rapid lignin deposition was observed in both regions, whereas secondary wall lignification was a more gradual process and initiated when the middle lamella lignin concentration was approximately 50% of maximum. Within the secondary wall, the S1 layer is lignified first. Then, lagging just behind cell wall formation, lignification of the S2 layer is initiated adjacent to the S1 layer and extends toward the lumen. Finally, the S3 layer lignified. Upon completion of lignification, the cell walls had a higher concentration of lignin in both the S1 and S3 layers than in the S2 layer.This Paper is an excerpt from the Ph.D. dissertation of Shiro Saka  相似文献   

20.
The aim of this study is to characterise the properties of juvenile and mature heartwood of black locust (Robinia pseudoacacia L.). Content, composition and the subcellular distribution of heartwood extractives were studied in 14 old-growth trees from forest sites in Germany and Hungary as well as in 16 younger trees of four clone types. Heartwood extractives (methanol and acetone extraction) were analysed by HPLC-chromatography. UV microspectrophotometry was used to topochemically localise the extractives in the cell walls. The natural durability of the juvenile and mature heartwood was analysed according to the European standard EN 350-1. Growth as well as chemical analyses showed that, based on extractives content, the formation of juvenile wood in black locust is restricted to the first 10–20 years of cambial growth. In mature heartwood, high contents of phenolic compounds and flavonoids were present, localised in high concentrations in the cell walls and cell lumen of axial parenchyma and vessels. In juvenile wood, the content of these extractives is significantly lower. Juvenile wood had a correspondingly lower resistance to decay by Coniophora puteana (brown rot fungus) and Coriolus versicolor (white rot fungus) than mature heartwood.  相似文献   

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