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1.
Summary Enzyme assay showed that the commercial cellulase from Trichoderma reesei degraded several polysaccharide substrates; highest activity was on xylan. Transmission electron micrographs showed that the T. reesei cellulase degraded nondecayed wood extensively; the attack always progressed from the point of contact into the cell wall. Cytochemically prepared wood that had been decayed by Poria placenta showed uniform distribution of electron-dense particles throughout the walls; the same results were observed with added T. reesei cellulase. In wood decayed by Ganoderma applanatum without or with added T. reesei cellulase, the progress of degradation was similar to that in nondecayed wood. Negatively stained T. reesei cellulase had 3–7 nm diameter for the smallest particles; the smallest diamaters of electron-dense particles in wood ranged from 3–7 nm. This suggests that the electron-dense particles probably are cellulase molecules. 相似文献
2.
The hyphal sheath is a morphological feature of many kinds of fungi. Although the fine structures of the sheath have been
studied in detail by a number of electron microscopy techniques, the function and physiology of the hyphal sheath are not
yet clarified. One reason for this is that the hyphal sheath is a colorless, mucilaginous, and delicate material so that it
is not easily identified. We developed a simple method to visualize and identify the hyphal sheath of the white-rot fungus
Phanerochaete crassa WD1694. The small mycelial pellets in shaken liquid cultures of P. crassa WD1694 were stained directly with phloxine B. Both the hyphae and the hyphal sheath that filled the gaps between each of
the hyphae were visualized and observed by light microscopy. The stained hyphae were further studied by transmission electron
microscopy, atomic force microscopy, and fl uorescence microscopy. Based on these observations, we confirmed that the staining
of the hyphae was also due to the presence of the hyphal sheath that closely covered the fungal cell wall. These results clearly
showed that the hyphal sheath was selectively stained with phloxine B and could be observed and identified by conventional
light microscopy.
Part of this report was presented at the 50th Lignin Symposium, Nagoya, October 2005 相似文献
3.
The occurrence and accumulation of β-1, 3-glucanase and chitinase in seedling roots of spruce (Picea abies) following challenge by the root-rot pathogen Heterobasidion annosum were studied. Chitinase activity increased 2–3 fold following inoculation, whereas no significant increase in the activity levels of glucanase was recorded during infection. With TEM immunogold labelling, the enzymes were localized in protein aggregates in host tissues and in the cell walls of intercellular hyphae. Gold particles were sparse and irregularly distributed within host-cell walls. Only minor labelling was observed on hyphal walls coated with electron-dense materials. The labelling intensity increased with infection time and was always higher than in non-infected seedling roots. When this experiment was repeated using root samples inoculated with the saprophyte Phlebiopsis gigantea, a similar labelling pattern was observed. The cross reactivity of antisera raised against sugar-beet chitinase and glucanase with spruceroot enzyme extracts was demonstrated using dot-blot assays and ELISA. 相似文献
4.
A fraction containing low-molecular-weight peptides that catalyzes redox reactions between electron donors and O2 to produce ·OH, was partially purified from wood-decaying cultures of the brown-rot fungusTyromyces palustris. Polyclonal antibodies raised to the fraction were used for immunogold labeling of transverse sections of sapwood of spruce in various stages of degradation byT. palustris to demonstrate the cellular localization of the ·OH-producing substance. Initially, the wood cell wall was attacked primarily by fungal hyphae growing in the cell lumen. During the early stages of degradation, the gold label was localized in the fungal cytoplasm and cell wall and in the extracellular slime sheath surrounding the fungal cell wall. The gold label also was found throughout the wood cell wall, although the cell wall remained almost intact so long as the fungal hyphae remained in the lumen. Thus, the ·OH-producing substance is secreted by the hyphae into the lumen, and it diffuses through the S3 layer into the S2 layer and the middle lamella. The role of this ·OH-producing system in wood degradation byT. palustris is discussed. 相似文献
5.
Sooty moulds on crape myrtle leaves were investigated using light and electron microscopy. The adaxial leaf surface was distinctly covered with soot‐like masses of dark brown hyphae and conidia. The main characteristics of the sooty moulds included stauroconidia, conidial clusters, hyphal degeneration and extracellular melanin depositions. Some conidia were round, measured ~10 μm in diameter, and mostly one‐septate; others were branched and multiseptate (stauroconidia). Based on their morphology, the sooty moulds were determined to consist of several component fungal species belonging to genera such as Antennaria, Metacapnodium and Tripospermum. Enclosed in electron‐dense melanin layers, hyphae and conidial clusters had concentric bodies exhibiting electron‐transparent cores and electron‐dense shells with fibrillar sheaths. Concentric bodies are hypothesized to function as multilayer lipid‐encapsulated nanobubbles or eukaryotic gas vesicles for cytoplasmic volume control. Intrahyphal hyphae possessed electron‐dense cytoplasm and lipid globules. These results suggest that sooty moulds are equipped with melanized cell walls, multicelled resting structures, hyphal regeneration, intrahyphal growth and gas vesicles to adapt to their xeric phylloplane environment. Condensed and elongated starch granules in the chloroplasts of mesophyll tissues may indicate the acclimation of the sooty leaf regions to light reduction and temperature increase. 相似文献
6.
Infection and Deterioration of Spruce Root Wood by Fornes annosus . The paper describes the mode of infection and subsequent deterioration of spruce root wood by Fornes annosus using light and electronmicroscopic observations. In the secondary xylem the overall penetration of cell walls is effected by means of microhyphae which produce boreholes. The degradation of cell walls is initiated in the S2 layer by diffusion of enzymes along the cellulose fibrils with subsequent hydrolysis of the amorphic incrusting substances. 相似文献
7.
A histological investigation of Oriental beech wood decayed by Pleurotus ostreatus and Trametes versicolor 
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下载免费PDF全文 Chemical, light and electron microscopic studies were carried out on wood of Oriental beech (Fagus orientalis Lipsky) decayed by the white‐rot fungi Pleurotus ostreatus and Trametes versicolor for 30, 60 and 120 days according to the modified European standard EN 113. Mass loss as well as lignin, cellulose and carbohydrate content were determined before and after fungal attack. There were no significant differences of wood mass loss and chemical composition between both fungi at the end of incubation. After each incubation period, small specimens were stained for microscopic studies. The micromorphology of fungal cell wall degradation was rather similar for both fungi. Both decreased the cell wall thickness to the same extent. The accumulation of hyphae as well as the rupture of cell walls was also similar. The occurrence of hyphae, cavities in the pits and vessel walls followed nearly the same patterns. The parenchyma cells were completely destroyed. Altogether, both fungi produced a simultaneous white rot in Oriental beech wood. 相似文献
8.
N. Yoshizawa A. Inami S. Miyake F. Ishiguri S. Yokota 《Wood Science and Technology》2000,34(3):183-196
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
9.
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
10.
Summary Observations made on ponded white spruce wood with the electron microscope revealed that initial branching of perforation hyphae of soft rot fungi did not parallel microfibrillar orientation in the S2 wall layer but rather occurred perpendicular to this alignment. In the absence of structural evidence suggesting mechanical entry it appeared that cell wall pencetration was accomplished through enzymatic activity at the hyphal apex.The authors wish to express their thanks to Miss S. Godkin and Mr. G. Chauret for technical assistance. 相似文献
11.
Rina D. Koyani S. Pramod Isha M. Bhatt K. S. Rao 《Journal of Sustainable Forestry》2013,32(5):502-515
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
12.
Scanning electron micrographs of the hyphae of Piptoporus betulinus in timber of Betula pendula. Hyphae of Piptoporus betulinus (Bull, ex Fr.) Karst. were photographed in naturally infected timber of Betula pendula Roth by means of scanning electron microscopy. The hyphae had an average diameter of 3μm and a cell wall thickness between 0.4 and 0.7 μm. The dissolution of the cell wall by specific fungal enzymes can be extremely well studied using scanning electron microscopy. 相似文献
13.
Interspecific interactions between fungi that colonize stumps of Picea sitchensis in Scotland were tested in dual cultures on Norkrans agar, spruce sawdust and in autoclaved blocks cut from roots. Isolates were ranked according to competitive ability on the different media, based on their ability to overgrow competitors or to form deadlock interactions. On the defined medium, Phaeolus schweinitzii was the species most able to overgrow competitors, followed by Stereum sanguinolentum and Heterobasidion annosum; Resinicium bicolor was the least able to overgrow competitors on this medium. By contrast, R. bicolor was the most competitive on spruce sawdust medium. Deadlocking interactions were formed most often in dual cultures on Norkrans agar. Observation of hyphal interactions on Norkrans agar under the microscope identified several different response types including growth of thin hyphae compared to control cultures, hyphal coiling, vacuolation of hyphae, hyphal lysis of one competitor and deposition of crystals in the agar. Hymenomycetes caused varying amounts of decay in autoclaved root blocks. Resinicium bicolor was able to replace other species in most co‐inoculations. Stereum sanguinolentum appeared to be the least competitive species in root block inoculations, being replaced by Melanotus proteus and R. bicolor, although interactions with H. annosum varied widely. These results indicate that substrate has a marked effect on interspecific fungal interactions, with wood‐based, particularly intact woody tissues closely matching competitive behaviour displayed in the field. 相似文献
14.
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
15.
Rina D. Koyani Isha M. Bhatt Hiral R. Patel Ajit M. Vasava 《Wood material science & engineering》2016,11(1):46-56
Lignin biodegradation potential of Schizophyllum commune Fr. is studied by using sound wood blocks of Ailanthus excelsa, Azadirachta indica, Tectona grandis, Eucalyptus sp. and Leucaena leucocephala. Initially, in vitro wood decay test showed minor weight loss, but it became rapid after one month. After 120 days of incubation, weight loss was minimum in T. grandis (24.05%) whereas it was maximum in A. excelsa (34.44%). Treated test blocks were characterised by enlargement of pits on ray cell wall, formation of additional boreholes in rays, separation of fibres and cell wall thinning and formation of ‘U’-shape notches. Fungal hyphae moved through the xylem cell lumen, and intercellular spaces formed in response to separation of fibres. Hyphae traverse in adjacent cell through the cell wall pits or by making additional boreholes. In all the species studied, xylem fibres and parenchyma (axial and ray) cells were more susceptible while vessels were resistant to fungal attack. In advanced stage of decay, fibres and axial parenchyma lost their rigidity while vessel walls showed uneven thinning. In the tension wood, G-fibres remained unaffected initially but loosening and separation of gelatinous layer facilitated fungal action and showed similar pattern of cell wall deterioration. Among the wood of different species studied, Tectona was more resistant whereas Ailanthus was more susceptible to fungal attack. 相似文献
16.
The size and location of silver particles in K-glycerate/AgNO3 impregnated Swedish pine, green wood as well as high temperature dried, have been studied using TEM micrographs.
The diameter of the silver particles was found to be 2–20 nm in the impregnated green wood and as large as 1000 nm (major
axis) for the ellipsoid-shaped silver clusters in the impregnated dried wood. Studying the projected area of the silver particles
in impregnated green wood indicated that there are a lot of particles (40%) in the compound middle lamella with fewer particles
in the S2 (6–8%), S1 (4%) and S3 (2%) layers. The average distance between the silver particles, 50 nm (S2-layer), in impregnated green wood shows that the impregnant is distributed in the cell wall at the microfibrilar level. Experimental
results show that the fastest diffusion path into the cell wall is from the lumen over the pit membrane through the compound
middle lamella and not from the lumen through the secondary wall layer S3.
Received 11 January 1998 相似文献
17.
Haruna Aiso-Sanada Futoshi Ishiguri Denny Irawati Imam Wahyudi Shinso Yokota 《Journal of Wood Science》2018,64(6):872-879
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. 相似文献
18.
Mariko Takano Noriko Hayashi Masaya Nakamura Muneyoshi Yamaguchi 《Journal of Wood Science》2009,55(4):302-307
The distribution of an extracellular peroxidase reaction by white-rot fungus Phanerochaete crassa WD1694 was visualized by peroxidase activity staining. The extracellular peroxidase reaction occurred at the hyphal tips
and in the fungal slime filling the gaps between the hyphae. We investigated whether the peroxidase reaction occurred from
the hyphal tips or in the slime. The hyphal tips were observed by phase-contrast microscopy, which showed that slime did not
exist around the hyphal tips. Time-course observation of hyphal tips showed that peroxidase staining became thick and intense
at the tips that did not have fungal slime. Daily observation of the peroxidase staining revealed that the staining was first
observed at the hyphal tips. Furthermore, strongly stained hyphae were observed in the stained slime. These results suggested
that an active species that oxidizes a peroxidase substrate is first produced at the tips of the hyphae, and then occurs in
the slime via diffusion when slime exists around the hyphae. Our results show that the extracellular peroxidase reaction that
is important to lignin biodegradation by white-rot fungi occurs directly at the tips of the hyphae and in the slime.
Part of this report was presented at the 50th Lignin Symposium, October 19–20, 2005, Nagoya, Japan 相似文献
19.
To compare the distributions of Raffaelea quercivora hyphae within seedlings of a susceptible species, Quercus crispula, and a resistant species, Q. glauca, we examined water conductance at transverse sections. Raffaelea quercivora was inoculated into the stems of seedlings in July (summer) and October (autumn) and observed by light and fluorescence microscopy at 1 and 2 weeks after inoculation. The hyphal distribution patterns expressed as the Iδ index differed between the species at each occasion. The hyphal growth was wider in Q. crispula than in Q. glauca in July inoculation, but did not differ in October inoculation. Non‐conductive sapwood in Q. crispula in transverse section was wider than that in Q. glauca at each occasion. The differences of hyphal growth and hyphal distribution patterns between species as little as 1 week after inoculation reflect differences in host susceptibility to the fungus. 相似文献
20.
《Southern Forests》2013,75(2):147-153
Tree diameter under and over bark at breast height (dbh), wood density and bark thickness were assessed on samples from control-pollinated families of Eucalyptus grandis, E. urophylla, E. grandis × E. urophylla and E. urophylla × E. grandis. The material was planted in field trials in the coastal Zululand region of South Africa. At 75 months, between three and seven of the best trees per family were felled and wood samples collected. Genetic parameters for wood density, bark thickness and bark percentage (ratio of double bark thickness to overbark diameter) and the inter-trait correlations for the different species and hybrids were calculated. Genetic parameter estimates for wood density, bark thickness and bark percentage in the E. urophylla × E. grandis hybrids showed these traits to be under total additive genetic control. This was confirmed by the intermediate hybrid means for these traits relative to those of the parental species. There was a very low correlation between dbh and wood density for the E. urophylla × E. grandis hybrids (rG = –0.07 and rP = 0.064). Amongst the E. urophylla families there was a moderate positive and significant phenotypic correlation between wood density and bark thickness (rP = 0.391), and between wood density and bark percentage (rP = 0.442). 相似文献