首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 46 毫秒
1.
We evaluated the antifungal and antitermite activities of wood vinegars produced from oil palm trunk. The wood vinegars were produced at three different pyrolysis temperatures, 350, 400, and 450 °C. Antifungal activities of vinegars were evaluated using a Petri dish bioassay with 0.5, 1.0, and 1.5% (v/v) against a white-rot fungus, Trametes versicolor, and a brown-rot fungus, Fomitopsis palustris. Antitermite activities were tested using a no-choice bioassay method for Coptotermes formosanus with 2.5, 5.0, 7.5, and 10.0% (v/v). All the wood vinegars exhibited antifungal activities against T. versicolor. In particular, the wood vinegar produced at 350 °C resulted in complete inhibition of T. versicolor growth at 1.0 and 1.5%. However, higher concentrations were required to obtain growth inhibition of F. palustris. All the wood vinegars exhibited antitermite activity to C. formosanus workers in the no-choice experiment at relatively high concentrations. For instance, 10% concentration was required to achieve 100% mortality against C. formosanus at all production temperatures. The lowest mass loss of the treated filter paper of 11.75% was obtained with a 350 °C—10.0% combination.  相似文献   

2.
A gas detection apparatus equipped with a semiconductor gas sensor was employed for qualitative and quantitative measurement of hydrogen and methane emitted by termites. A gas sample of 2.5 ml was injected into the semiconductor gas sensor through the gas detection apparatus, and the maximum voltage of the sensor was converted into gas concentration. The gas samples were collected from three distinct experiments: (1) five combinations of workers and soldiers of Coptotermes formosanus with and without a wood specimen; (2) C. formosanus under six temperature conditions; and (3) four different termite species, C. formosanus, Reticulitermes speratus, Incisitermes minor, and Zootermopsis nevadensis. The hydrogen and methane concentrations increased with an increase in the number of termites. Concentrations were higher in samples with a wood specimen than without it. Both hydrogen and methane concentrations were the highest for the samples at 35 °C and were lowest at 15 and 5 °C. The concentrations were very low at 45 °C because all the termites had died in a few hours. The concentrations of hydrogen and methane were highest for Z. nevadensis, the dampwood termite, among the four species, and no methane was detected for I. minor, the drywood termite, at 28 °C and 75 % RH.  相似文献   

3.
Termiticidal activity of wood vinegar, its components and their homologues   总被引：5，自引：0，他引：5  
The termiticidal activity of wood vinegar, its components, and their homologues have been studied. Three kinds of wood vinegar made from the mixed chips ofCryptomeria japonlca andPseudotsga menziesii (wood vinegar A),Quercus serrata (wood vinegar B), andPinus densiflora (wood vinegar C) exhibited high termiticidal activities againstReticulitermes speratus. Acetic acid, which is the largest content of wood vinegar, exhibited high termiticidal acitivity. The contents of organic fraction of wood vinegars and acetic acid might be responsible for the differences in termiticidal activities among these wood vinegars. The structure and termiticidal activity relations of phenols were studied. Phenol with some substituents revealed higher termiticidal activity than benzene derivatives, which have no hydroxyl group; an ortho substituent of phenol plays an important role in termiticidal activity. It has become apparent that high termiticidal activity cannot be obtained by a phenolic hydroxyl group alone; it can be obtained, however, by some substituents, especially an ortho substituent in addition to a phenolic hydroxyl group. The bulkiness of the substituent at the ortho position participates in termiticidal activity; activity decreases as the size of an ortho substituent increases. It is thought that the interaction at the receptor site of termites is affected by the increased size of the ortho substituent.  相似文献   

4.
We investigated the effects of high-temperature drying schedules (120°–130°C) on decay and termite feeding of Japanese larch timbers. Thermogravimetric analysis was conducted to investigate changes of the wood components. Decay and termite feeding tests showed that specimens dried under high-temperature schedules were susceptible against a decaying fungus Fomitopsis palustris and attacks from termites Coptotermes formosanus and Reticulitermes speratus. These drying schedules changed chemical components, which were suggested by the thermal analytical result compared to the control sample. The results of this study indicated that the acceleration of termite feeding takes place even under temperatures that are comparatively lower than that used in our previous research in which 170°C steaming treatment was applied to Japanese larch wood. Decay durability against a brown rot fungus also decreased, possibly from production of low molecular weight fragments when hemicellulose decreased during the high-temperature drying processes.  相似文献   

5.
A laboratory no-choice termite bioassay was conducted to evaluate the ability of copper HDO (CX-A or copper xyligen) to protect radiata pine (Pinus radiata D. Don) wood samples from attack by two subterranean termite species, Reticulitermes speratus and Coptotermes formosanus. A series of sapwood samples were pressure treated with either 0.25%, 0.50%, 0.75%, or 1.00% copper HDO solution. Samples treated with equivalent concentrations of a benchmark preservative, CCA-C, were used as treated controls. All samples (including controls) were subjected to an artificial weathering schedule before the bioassay. The samples were exposed to 30-day R. speratus tests and 3-week C. formosanus tests. Copper HDO was shown to deter termites from significant feeding on the treated wood. At a retention of 5.8 kg/m3 (treated with 0.75% solution) or higher, the mass loss from termite feeding did not exceed 3% for both the 30-day R. speratus tests and the 3-week C. formosanus tests. At each of the retentions tested, copper HDO performed comparably with equivalent retentions of CCA-C; however, field data are needed to validate these laboratory results. The preliminary findings are that copper HDO pressure treatment has potential as a viable method of protecting wood from attack by both termite species tested.  相似文献   

6.
The relationship between the moisture content (MC) of wood blocks and the feeding activities of two Japanese subterranean termites, Coptotermes formosanus Shiraki and Reticulitermes speratus (Kolbe), was investigated with two choice tests. When three wood blocks with low MC (6%–12%), middle MC (79%–103%), and high MC (140%–182%) were exposed to workers of C. formosanus and R. speratus in a choice test, the feeding preferences were found in the middle MC blocks for C. formosanus, and the middle and high MC blocks for R. speratus, although wood blocks of low MC were also attacked. In a second choice test, wood blocks consisting of five pieces with water-impregnated (MC: 133%–191%) top, middle, or bottom piece were exposed to workers of both species. Higher consumptions were generally obtained in water-impregnated wood pieces and bottom pieces.  相似文献   

7.
Two species of Japanese subterranean termite, Coptotermes formosanus Shiraki and Reticulitermes speratus (Kolbe), were used in an investigation of the optimum temperature–relative humidity (RH) combination for their feeding activities. Daily wood consumption per worker and survivals were measured, and the protozoan fauna in the hindgut were observed under 15 temperature–RH combinations for 1 week. Five temperatures (20°, 25°, 30°, 35°, and 40°C) and three RH conditions (50%, 70%, and 90% RH) were examined. The activities of the workers were highest at around 30°C for both species, and workers died at 40°C within 5 days and 2 days for C. formosanus and R. speratus, respectively. The optimum RH condition for feeding activity was 90% RH for C. formosanus and 70%–90% RH for R. speratus. The optimum temperature–RH combinations for feeding activities were 30°C at 90% RH for C. formosanus and 30°C at 70%–90% RH for R. speratus.  相似文献   

8.
The carbonization process causes different physical and chemical transformations to wood, affecting the final properties of the charcoal produced. In Brazil, the cutting and use of Ocotea porosa (Nees & Mart. Ex Nees) L. Barroso is legally prohibited. But the difficulty of identifying the species used to produce charcoal hinders enforcement efforts to protect this and other endangered tree species. The aim of this work was to characterize the anatomy of charcoal made from O. porosa at different temperatures to provide information to facilitate differentiation of the species by the authorities in charge of suppressing illegal commerce. Samples were carbonized by direct heating and final temperatures of 350, 450 and 650 °C, besides a group under a ramp heating regime also with a final temperature of 450 °C. The qualitative characteristics of the O. porosa wood were preserved at the carbonization temperatures studied permitting the use of its anatomical structures for identification of carbonized wood to support control of the illegal trade in charcoal of this species.  相似文献   

9.
The structural changes of the cell wall and crystalline cellulose of Quercus variabilis wood in a pyrolysis system at several temperatures ranging from 250 to 500°C were investigated to examine the wood carbonization characteristics. The volume of the wood sample was decreased and the weight loss was increased by increasing the carbonization temperature. Vessels collapsed severely in tangential direction during the charring process above 350°C. SEM observation indicated that the layering structure of the walls in wood fibers and parenchyma cells were retained below 300°C. However, the cell walls above 350°C changed to an amorphous-like structure without cell wall layering. X-ray diffraction confirmed that the cellulose crystalline substance was still remained at the carbonization temperature of 300°C but was not detected above 350°C. It can be concluded that the transition from Q. variabilis wood to charcoal might occur at approximately 350°C.  相似文献   

10.
Constituents of tars formed during the aging of bamboo (Phyllostachys pubescens), oak (Quercus serrata), and pine (Pinus densiflora) wood crude vinegars were analyzed by pyrolysis-gas chromatography (Py-GC) and pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) to investigate their origination. The pyrolysate of tars obtained from the wood and bamboo crude vinegars were almost identical and were primarily composed of phenolic compounds and aromatic hydrocarbons. In addition, during the aging of model wood vinegar that was prepared for comparison with the wood and bamboo vinegars, a marked decrease was observed in the levels of phenolic compounds (phenol; o-, p-, and m-cresol; and syringol). Furthermore, the Py-GC-MS results of the tars produced during the aging of the model wood vinegar revealed that phenolic compounds were primarily responsible for the formation of tar during the aging of wood and bamboo crude vinegars. Pyrroles, which may be derived from the primary pyrolysate of amino acids, nitrogen-containing extracts, or both, were also partially involved in the formation of tar during the aging period.  相似文献   

11.
Here, we investigated the reaction mechanism of longifolene autoxidation and the bioactivities of its products. A longifolene sample was autoxidized at 120 °C or room temperature, and the products were analyzed by gas chromatography. Longicamphenylone, norlongilactone, isolongifolic acid, longifolic acid, and longifolene–hydroxy ketone were detected as the products in the autoxidation at 120 °C. During the reaction, longifolene was converted into the other autoxidation products via the formation of longifolene oxide as an intermediate. Anti-termite activities of the longifolene and its autoxidation products were examined against a Japanese subterranean termite (Reticulitermes speratus Kolbe) by paper disk methods in Petri dishes. Longifolene and the autoxidation products exhibited anti-R. speratus activities, and all the autoxidation products had stronger termiticidal and antifeedant activities than longifolene.  相似文献   

12.
This paper characterizes wood and charcoal made from Hymenaea aurea, Mimosa scabrella, Tabebuia capitata and Eucalyptus alba by scanning electron microscopy and near infrared for the purpose of developing a technique to identify the source of charcoal samples. Ten test samples were prepared for each species, oriented in transverse, radial and tangential section. Samples were carbonized in a muffle furnace with a final temperature of 450 °C and a heating rate of 1.66 °C/min. The microscopic structures of the wood and charcoal samples were verified by scanning electron microscopy, and spectra were obtained with a spectrophotometer, equipped with an integrating sphere and operating in transmittance mode. The spectra of the wood samples present characteristic bands of lignocellulosic material, while the spectra of the charcoal samples show small or nil absorption in the near-infrared region. The near-infrared spectroscopy technique was efficient in discriminating the four species studied.  相似文献   

13.
The effect of selective removal of extractives on termite or decay resistance was assessed with matched samples of Thuja plicata Donn ex D. Don and Chamaecyparis nootkatensis (D.Don) Spach heartwood. Samples were extracted using a variety of solvents and then exposed to the subterranean termite Coptotermes formosanus Shiraki in a no-choice feeding test or to the brown-rot fungus Postia placenta (Fr.) M. Larsen & Lombard in a soil bottle test. At the same time, the effect of naturally occurring variations in heartwood extractives on termite or decay resistance was evaluated by testing samples from the inner and outer heartwood of five trees of each species against C. formosanus and P. placenta and analyzing matched wood samples for their extractive content. The results suggest that the methanol-soluble extractives in T. plicata and C. nootkatensis play an important role in heartwood resistance to attack by C. formosanus and P. placenta. Total methanol-soluble extractive content of the heartwood was positively correlated with both termite and decay resistance; however, there was much unexplained variation and levels of individual extractive components were only weakly correlated with one another. Further studies are under way to develop a better understanding of the relationships between individual extractive levels and performance.  相似文献   

14.
The effect of gamma irradiation at 100 kGy and at lower levels on termite resistance was examined in the laboratory by no-choice and choice feeding termite tests (Coptotermes formosanus Shiraki) using four wood species: sapwood of Cryptomeria japonica D. Don, and heartwoods of Pseudotsuga menziesii (Mirbel) Franco, Larix kaempferi (Lambert) Carriere, and Chamaecyparis obtusa Endl. The wood consumption rates in C. japonica and P. menziesii specimens were likely to increase with increases in gamma-irradiation levels, whereas little effect of gamma irradiation was seen in L. kaempferi and C. obtusa. Similar results were obtained in the two-choice test. The current results indicated that in the two-choice test with C. formosanus, 100-kGy-irradiated C. japonica and P. menziesii, which are not rich in antitermite substances, were eaten more than other wood samples with or without gamma irradiation. However, only C. japonica showed significant difference in termite feeding activity. The mass loss in 100-kGy-irradiated C. japonica was significantly higher in the multichoice test.  相似文献   

15.
The essential oils of eighteen Egyptian plants were extracted by hydrodistillation and their chemical compositions were analyzed by GC-MS. The antifungal activity of the isolated oils was evaluated against two wood decay fungi Hexagonia apiaria and Ganoderma lucidum in vitro. The essential oil of Artemisia monosperma showed the highest inhibitory effect against H. apiaria (EC50 = 31 mg L?1) and G. lucidum (EC50 = 53 mg L?1). The results of in vitro tests indicated that the essential oils of Cupressus sempervirens, Citrus limon, Thuja occidentalis, Schinus molle, A. monosperma and Pelargonium graveolens were the most potent inhibitors against both fungi. These six oils caused significant reduction of wood mass loss of Scots pine sapwood after 6 weeks of fungal exposure. The oil of C. limon revealed the highest reduction of wood mass loss caused by H. apiaria, while A. monosperma oil displayed the highest reduction of wood loss caused by G. lucidum. These results support the potential use of essential oils for wood protection against decay fungi.  相似文献   

16.
  • ? Tree age is one of the most important factors to affect the natural durability of wood.
  • ? The purpose of this study was to determine the natural termite resistance of heartwood and sapwood of teak (Tectona grandis Linn. fil.) for trees aged 8, 30 and 51 years. Reticulitermes speratus Kolbe was employed as a test termite using a no-choice feeding method.
  • ? The heartwood and sapwood of all of the trees tested exhibited antitermitic activity. Based on the mean mass loss due to termite activity, the sapwood and heartwood regions of 8-year-old trees are the most susceptible to termites while the heartwood regions of the 30-year-old trees showed termite resistance similar to the termite resistance of 51-year-old trees.
  • ? The mass loss is moderately correlated with n-hexane extractive content, total extractive content, brightness and redness of the wood.
    •   相似文献   

    17.
    Efficacy of four different essential oils against the subterranean termite, Coptotermes curvignathus Holmgren, was assessed in various bioassays. Laboratory results indicate that the highest termite mortality was found in Dipterocarpus sp. essential oil after 24 h (LC50 = 1.62 %) and the lowest in Melaleuca cajuputi (LC50 = 4.60 %). The wood consumption in the filter paper treated with Dipterocarpus sp. oil is also smaller than for the other three essential oils tested. However, the other three essential oils also inhibited termite susceptibility of the specimens. Dipterocarpus sp. (keruing oil) was the most effective insect antifeedant and repellent against C. curvignathus. The results suggest that essential oils might have some beneficial activity of economic value and are considered good candidates for the development of new chemicals (repellents or antifeedants) for termite control.  相似文献   

    18.
    Cyclocarya paliurus is a highly valued and multiple function tree species. There has been increasing interest in planting and managing C. paliurus for timber production and medical use owing to loss of harvestable acreage. Seed from six provenances was collected from the main natural range of this species. Significant variation in growth and wood properties was measured among the six provenances at age 7 years. Provenance mean height and DBH varied significantly from 730–991 and 6.7–10.0 cm, whereas provenance means of wood basic density and crystallinity ranged from 463–554 kg m?3 and 51.4–74.1 %, respectively. Mean provenance microfibril angle (MFA) at breast height ranged from 18.1° to 23.2°, while MFA at breast height varied from 11.0° to 34.5° among growth rings which showed a consistent pith-to-bark trend of declining angles. There was no significant relationship of growth rate with latitude or longitude of seed sources, however, provenances from low latitude and longitude grew faster at the trial site. Wood quality was significantly related to latitude of seed sources, showing a positive correlation for both wood basic density and wood crystallinity, but a highly negative association with MFA. Significant correlations between wood properties measured indicated that there exists a great opportunity to improve wood quality of C. paliurus through selection of juvenile trees with low MFA.  相似文献   

    19.
    Spruce wood blocks were acetylated in the presence of potassium acetate (KAc) at 20, 40, 60, 80 and 120°C. At 20°C, the weight percent gain (WPG) due to the KAc-catalyzed acetylation reached 20% in 18 days, whereas that due to pyridine-catalyzed acetylation did not exceed 8%. The hygroscopicity and dimensional stability of the KAc-acetylated wood were the same as those of conventionally acetylated wood at the same WPG, irrespective of reaction temperature. These facts suggest that the KAc enables simplified acetylation of wood at room temperature. The activation energy (E a) of the KAc-acetylation in the lower temperature range (20–40°C, 121–131 kJ/mol) was comparable to that of the acetylation of wood meal (140–146 kJ/mol). It was speculated that diffusion became a minor factor at reduced reaction rates in the lower temperature range, thus requiring a greater E a.  相似文献   

    20.
    Pulverized samples of wood, cedar and eucalyptus were treated with 5 N NaOH solutions at 25–150 °C. Hemicellulose and lignin content in the samples decreased with increasing treatment temperatures, while the recovery of glucose was maintained at nearly 90 %. X-ray diffraction analysis showed that the content of the original cellulose I structure in the samples decreased with increasing temperature, and most of the cellulose in the sample treated at 150 °C was converted to cellulose II by mercerization. Enzymatic hydrolysis of the alkaline-treated samples was carried out at 37 °C using solutions comprising a mixture of cellulase and β-glucosidase. The samples treated at higher temperatures showed better enzymatic degradability. Treatment with an alkaline solution of lower concentration (1 N NaOH) at 150 °C was also used. Despite significant quantities of hemicellulose and lignin being removed, mercerization was not induced. The enzymatic degradability was much lower than that of the sample treated with a 5 N NaOH solution at 150 °C. Thus, treatment with concentrated alkaline solution at high temperature led to not only the removal of hemicellulose and lignin, but also to modification of the cellulose structure, which resulted in high efficiency of enzymatic saccharification of the wood samples.  相似文献   

    设为首页 | 免责声明 | 关于勤云 | 加入收藏

    Copyright©北京勤云科技发展有限公司  京ICP备09084417号