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1.
Identification of anisotropic vibrational properties of Padauk wood with interlocked grain 总被引:1,自引:0,他引:1
Iris Brémaud Pierre Cabrolier Joseph Gril Bruno Clair Jean Gérard Kazuya Minato Bernard Thibaut 《Wood Science and Technology》2010,44(3):355-367
Grain deviations and high extractives content are common features of many tropical woods. This study aimed at clarifying their
respective impact on vibrational properties, referring to African Padauk (Pterocarpus soyauxii Taub.), a species selected for its interlocked grain, high extractives content and uses in xylophones. Specimens were cut
parallel to the trunk axis (L), and local variations in grain angle (GA), microfibril angle (MFA), specific Young’s modulus
(E′
L
/ρ, where ρ stands for the density) and damping coefficient (tanδL) were measured. GA dependence was analysed by a mechanical model which allowed to identify the specific Young’s modulus (E′3/ρ) and shear modulus (G′/ρ) along the grain (3) as well as their corresponding damping coefficients (tanδ3, tanδG). This analysis was done for native and then for extracted wood. Interlocked grain resulted in 0–25° GA and in variations
of a factor 2 in E′L/ρ and tanδL. Along the grain, Padauk wood was characterized, when compared to typical hardwoods, by a somewhat lower E′3/ρ and elastic anisotropy (E′/G′), due to a wide microfibril angle plus a small weight effect of extracts, and a very low tanδ3 and moderate damping anisotropy (tanδG/tanδ3). Extraction affected mechanical parameters in the order: tanδ3 ≈ tanδG > G′/ρ > > E′3/ρ. That is, extractives’ effects were nearly isotropic on damping but clearly anisotropic on storage moduli. 相似文献
2.
Anisotropy of wood vibrational properties: dependence on grain angle and review of literature data 总被引:1,自引:1,他引:0
The anisotropy of vibrational properties influences the acoustic behaviour of wooden pieces and their dependence on grain
angle (GA). As most pieces of wood include some GA, either for technological reasons or due to grain deviations inside trunks,
predicting its repercussions would be useful. This paper aims at evaluating the variability in the anisotropy of wood vibrational
properties and analysing resulting trends as a function of orientation. GA dependence is described by a model based on transformation
formulas applied to complex compliances, and literature data on anisotropic vibrational properties are reviewed. Ranges of
variability, as well as representative sets of viscoelastic anisotropic parameters, are defined for mean hardwoods and softwoods
and for contrasted wood types. GA-dependence calculations are in close agreement with published experimental results and allow
comparing the sensitivity of different woods to GA. Calculated trends in damping coefficient (tanδ) and in specific modulus
of elasticity (E′/ρ) allow reconstructing the general tanδ-E′/ρ statistical relationships previously reported. Trends for woods with different mechanical parameters merge into a single
curve if anisotropic ratios (both elastic and of damping) are correlated between them, and with axial properties, as is indicated
by the collected data. On the other hand, varying damping coefficient independently results in parallel curves, which coincide
with observations on chemically modified woods, either “artificially”, or by natural extractives. 相似文献
3.
Tian Zhang Shu-Lin Bai Sandrine Bardet Tancrède Alméras Bernard Thibaut Jacques Beauchêne 《Journal of Wood Science》2011,57(5):377-386
The radial trends of vibrational properties, represented by the specific dynamic modulus (E′/ρ) and damping coefficient (tan δ), were investigated for three tropical rainforest hardwood species (Simarouba amara, Carapa procera, and Symphonia globulifera) using free-free flexural vibration tests. The microfibril angle (MFA) was estimated using X-ray diffraction. Consistent
patterns of radial variations were observed for all studied properties. E′/ρ was found to decrease from pith to bark, which was strongly related to the increasing pith-bark trend of MFA. The variation
of tan δ along the radius could be partly explained by MFA and partly by the gradient of extractives due to heartwood formation. The
coupling effect of MFA and extractives could be separated through analysis of the log(tan δ) versus log(E′/ρ) diagram. For the species studied, the extractive content putatively associated with heartwood formation generally tends
to decrease the wood damping coefficient. However, this weakening effect of extractives was not observed for the inner part
of the heartwood, suggesting that the mechanical action of extractives was reduced during their chemical ageing. 相似文献
4.
Dynamic viscoelastic properties of wood acetylated with acetic anhydride solution of glucose pentaacetate 总被引:1,自引:0,他引:1
Spruce wood specimens were acetylated with acetic anhydride (AA) solutions of glucose pentaacetate (GPA), and their viscoelastic
properties along the radial direction were compared to those of the untreated and the normally acetylated specimens at various
relative humidities and temperatures. Higher concentrations of the GPA/AA solution resulted in more swelling of wood when
GPA was introducted into the wood cell wall. At room temperature the dynamic Young's modulus (E′) of the acetylated wood was enhanced by 10% with the introduction of GPA, whereas its mechanical loss tangent (tan δ) remained almost unchanged. These changes were interpreted to be an antiplasticizing effect of the bulky GPA molecules in
the wood cell wall. On heating in the absence of moisture, the GPA-acetylated wood exhibited a marked drop in E′ and a clear tan δ peak above 150°C, whereas the E′ and tan δ of the untreated wood were relatively stable up to 200°C. The tan δ peak of the GPA-acetylated wood shifted to lower temperatures with increasing GPA content, and there was no tan δ peak due to the melting of GPA itself. Thus the marked thermal softening of the GPA-acetylated wood was attributed to the
softening of wood components plasticized with GPA.
Received: March 29, 2002 / Accepted: May 21, 2002
Correspondence to:E. Obataya 相似文献
5.
Aida Se Golpayegani Iris Brémaud Joseph Gril Marie-France Thevenon Olivier Arnould Kambiz Pourtahmasi 《Journal of Wood Science》2012,58(2):153-162
Vibrational properties of wood are affected by several parameters, of which extractives can be one of the most important ones.
Wood for European musical instruments has been often studied, but traditional Middle Eastern ones had been left unnoticed.
In this study white mulberry (Morus alba L.), the main material for long-necked lutes in Iran, was extracted by five solvents of various polarities (water included).
Free-free bar forced vibrations were used to measure longitudinal (L) loss tangent (tanδ), storage (elastic) modulus (E′) and specific modulus (E′/γ) in the acoustic range. Their anisotropy between the 3 axes of orthotropy was determined by dynamic mechanical analysis.
Native wood had a quite low E
L′/γ but its tanδ was smaller than expected, and the anisotropy of tanδ and E′/γ was very low. Removal of extractives caused tanδ to increase and moduli to decrease. Acetone, the most effective solvent on damping despite a moderate extraction yield, increased
tanδ
L by at least 20% but did not modify E′/γ as much. When used successively, its effects masked those of solvents used afterwards. Anisotropy of E′/γ was nearly unchanged after extraction in methanol or hot water, while tanδ was much more increased in R than in T direction. Results suggest that in white mulberry, damping is governed more by nature
and localization of extractives rather than by their crud abundance. 相似文献
6.
EugeneOnyekweOnuorah 《林业研究》2002,13(3):183-190
本文调查了三种耐用木材(Afzelia africana J.E. Smith; Erythrophleum suaveolens (Guill & Perr.) Brenam. Syn. E guinensis G.Don. or Milicia excelsa (Welw) C.C. Berg. Syn. Chlorophora excelsa (Welw) Benth.)的心材提取物(在60%的甲醇中风干提取)和两种专用木材防腐剂(CCA和Penta)在暴露的土壤区组设计条件下,抑制三种木材腐朽菌(Coridopsis Polyzona Klotzch; Lenzites trabea; or Trametes cingulata Fr.)对见血封喉边材的侵袭的相对潜能,并测定其阈值。提取物和防腐剂的剂量分别是8.009、24.778、48.056、96.111、144.167 kg·m-3 ,样品的暴露处理时间与ASTM D1413-72规定的一致分别是14周和18周。结果显示:在阈值范围内,任何一种心材提取物或木材防腐剂在研究中对木材腐朽菌的抑制能力在0.01的显著水平下,差异显著。这些生物杀灭剂的相对功效是取决于真菌的种类。没有任何一种心材提取物或木材防腐剂(除在用最高的存留水平处理被侵袭的非洲毒箭木的条件下)对于被处理的木材能够授予"非常持久"等级。本土树种的心材提取物相对持久力的减少的可能原因是复杂的。在最高的存留量(144.167 kg·m-3)水平下,在0.05显著水平下每种心材提取物和任一种专用木材防腐剂(CCA和Penta)之间的功效差异不显著. 相似文献
7.
Takanori Imai Sousuke Inoue Naomi Ohdaira Yasuyuki Matsushita Rie Suzuki Mariko Sakurai José Manoel Henriques de Jesus Salete Kiyoka Ozaki Zenesio Finger Kazuhiko Fukushima 《Journal of Wood Science》2008,54(6):470-475
Heartwood extracts from Amazonian trees cumaru-ferro (Dipteryx odorata), jatoba (Hymenaea courbaril), and guarita (Astronium lecointei) exhibit antioxidant activities comparable with that of α-tocopherol, a well-known antioxidant. This article reports the characterization of the antioxidant compounds in the extracts
of the three heartwoods. Silica gel column chromatography of the cumaru-ferro EtOAc extract yielded (−)-(3R)-7,2′,3′-trihydroxy-4′-methoxyisoflavan and (+)-(3R)-8,2′,3′-trihydroxy-7,4′-dimethoxyisoflavan. Silica gel column chromatography followed by preparative high-performance liquid
chromatography of the jatoba EtOAc extract yielded (−)-fisetinidol and (+)-trans-taxifolin. Chemical structures were assigned using electron-ionization mass spectrometry, 1H and 13C nuclear magnetic resonance (NMR) spectroscopy including nuclear Overhauser effect spectroscopy (NOESY), as well as optical
rotation and circular dichroism. Gas chromatography-mass spectrometry demonstrated that the isolated compounds were predominant
in the EtOAc extracts. In the guarita EtOAc extract, catechin and gallic acid were identified by comparing their retention
times and mass fragmentation patterns with those of authentic samples. Antioxidant activity determined by the 1,1-diphenyl-2-picrylhydrazyl
assay demonstrated that all these compounds had activities comparable with that of α-tocopherol.
Part of this report was presented at the 57th Annual Meeting of the Japan Wood Research Society, Hiroshima, August 2007 相似文献
8.
Eucalyptus globulus sapwood and heartwood were delignified at 130°, 150°, or 170°C by kraft pulping. Pulp yields of heartwood were lower than
those of sapwood (46.5% vs. 50.4% at 170°C). Delignification was modeled using consecutive and simultaneous kinetic models.
The modeling was similar for heartwood and sapwood, and either approach could be used, with both yielding good correlations
between experimental and model data. The consecutive model identified two delignification phases with similar reaction rates
and activation energies for heartwood and sapwood at 150° and 170°C. At 130°C only one phase was identified. Three reactive
types of lignin fractions were identified using the simultaneous model, without differences between heartwood and sapwood.
Their reaction rates were 0.152, 0.138, and 0.003 min−1 at 170°C, and the activation energies were 132, 119, and 102 kJ.mol−1. The presence of heartwood did not influence the kinetic development of delignification. The negative impact of heartwood
in pulping is related to the higher content of extractives (9.8% vs. 3.9% in heartwood and sapwood) and to their influence
on the process, namely in the heating-totemperature phase when a substantial mass loss occurs (30% vs. 20% for heartwood and
sapwood). 相似文献
9.
MD. Atiar Rahman Takeshi Katayama Toshisada Suzuki Yuka Yoshihara Takashi Nakagawa 《Journal of Wood Science》2007,53(2):114-120
To clarify the biosynthetic pathway for syringyl lignans, especially syringyl tetrahydronaphthalene lignans and formation
of the C2–C7′ linkage, production of (+)-lyoniresinol (LYR) and its predicted intermediates [syringaresinol (SYR), 5,5′-dimethoxylariciresinol
(DMLR), and 5,5′-dimethoxysecoisolariciresinol (DMSLR)] in Lyonia ovalifolia var. elliptica was investigated by means of feeding experiments with radiolabeled precursors. Following individual administration of l-[U-14C]phenylalanine (Phe), [8-14C]sinapyl alcohol (SA), and [8,8′-14C]SYR to excised young shoots of L. ovalifolia and their subsequent metabolism, free [14C]lignans and [14C]lignan glycosides were extracted with methanol from stems and leaves and were divided into ethyl acetate-soluble fractions
(lignans) and aqueous fractions (lignan glycosides), respectively. Using a combination of xylanase, cellulase, and β-glucosidase, the glycosides were hydrolyzed to liberate [14C]lignans as aglycones. l-[U-14C]Phe was incorporated into (+)-[14C]SYR [stem 0.38%, 8% enantiomeric excess (e.e.)], (−)-[14C]SYR (leaves 2.75%, 72% e.e.), (+)-[14C]DMLR (stem 0.07%, 18% e.e. and leaves 0.009%, 58% e.e.), (−)-[14C]DMSLR (stem 0.03%, 46% e.e. and leaves 0.05%, 20% e.e.), (+)-[14C]LYR (leaves 0.013%, 22% e.e.) and glycosides of (+)-[14C]LYR (stem 0.036%, 50% e.e.) in 24h. Based on the percent incorporation and enantiomeric composition of the lignans, the
biosynthetic pathway of (8R,8′R)-(+)-LYR was proposed as follows: a nonselective dehydrogenative dimerization of sinapyl alcohol yields (±)-SYR, which is
reduced with low specificity to give (8R,8′R)-(+)-DMLR. This is cyclized to directly give (+)-LYR as well as reduced again to (8R,8′R)-(−)-DMSLR. Although further transformation of (−)-DMSLR also leads to the formation of (+)-LYR, cyclization could be a main
pathway for (+)-LYR biosynthesis.
This report was presented at the IAWPS 2005 International Symposium on Wood Science and Technology, Yokohama, November 2005 相似文献
10.
Kazuya Tsuruta Yayoi Yoshida Norihisa Kusumoto Nobuhiro Sekine Tatsuya Ashitani Koetsu Takahashi 《Journal of Wood Science》2011,57(6):520-525
The growth inhibition activities of essential oils obtained from Cryptomeria japonica, Chamaecyparis obtusa, and Pinus thunbergii were examined against the bacillariophyceae Skeletonema costatum, also known as red tide plankton. The essential oils were extracted from the heartwood, leaves, and bark of these typical
indigenous Japanese conifers. The essential oils from C. japonica bark and P. thunbergii heartwood possessed strong growth inhibition activity. The chemical compositions of these essential oils were analyzed by
gas chromatography/flame ionization detection (GC-FID) and gas chromatography/mass spectrometry (GC-MS). α-Terpineol and longifolene were the main components of the essential oil from P. thunbergii heartwood. The C. japonica bark essential oil was mainly composed of α-terpineol, δ-cadinene, isophyllocladene, and ferruginol. Ferruginol and longifolene showed more potent growth inhibition against S. costatum than hinokitiol (β-thujaplicine), which is known to be a strong antifungal compound among wood components. Ferruginol and longifolene were important
factors for the growth inhibition activity of the essential oils from C. japonica bark and P. thunbergii heartwood, respectively. These results suggest the possibility of using C. japonica bark and P. thunbergii heartwood for the control of red tide plankton. 相似文献
11.
An allometric model that explains the mechanism of the difference in the slope of the Reineke equation (A) among species was proposed based on the allometric relationships of mean tree height (H) to quadratic mean diameter D (H ∝ D
θ
) and stand density N (H ∝ N
δ
), i.e., A = θ/δ. The proposed model was fitted to Japanese cypress (Chamaecyparis obtusa Endl.) and red pine (Pinus densiflora) stands. The allometric exponents θ and δ were, respectively, 0.8995 and −0.5000 for cypress and 0.8612 and −0.6619 for pine. The difference between cypress and pine
was significant for δ but not for θ. Inserting the exponents into the model resulted in predicted slopes of −1.7991 for cypress and −1.3011 for pine. The difference
in the slope of the Reineke equation between the two species was produced by characteristics related to the tree crown, rather
than characteristics related to stem slenderness. The proposed model enables us to estimate the slope of the Reineke equation
from commonly measured stand attributes, such as mean tree height and quadratic mean diameter. Therefore, the proposed model
is expected to be practical and convenient for estimating the slope of the Reineke equation and for explaining the mechanism
of its variation among species. The model should be also accepted as a generalized model of the stand density versus quadratic
mean diameter relationship, whereas the original Reineke equation should be seen as a specific case of this model. 相似文献
12.
Akiko Nagasaka Yu Nagasaka Kinuko Ito Tsutomu Mano Masami Yamanaka Atushi Katayama Yoshikazu Sato Andrey L. Grankin Andrey I. Zdorikov Gennady A. Boronov 《Journal of Forest Research》2006,11(5):377-382
We examined the relationship between the annual escapement of salmon and the δ
15N of willow (Salix spp.) leaves to evaluate the contribution of marine-derived nutrients (MDN) to riparian vegetation around the Pacific Northwest
and Northeast regions. Foliar δ
15N values ranged from −3.42‰ to 4.65‰. The value increased with increasing density of carcasses up to 500 fish/km and 1500
fish/km. δ
15N values were variable at carcass densities below 500 fish/km. Possible factors affecting the fluctuation of δ
15N at reference sites are: (1) denitrification; (2) the presence of N2-fixing trees, such as alder; and (3) agricultural runoff. δ
15N values at the sites with carcass densities over 500 fish/km were consistently high, while a value of δ
15N below zero was observed at only one site (Rusha River; δ
15N = −1.87‰). At this site, most adult pink salmon returned to limited locations near the estuary because steeper channel gradients
acted as a migration barrier, resulting in the negative δ
15N value. Nevertheless, we concluded that our results showed evidence of the feedback of MDN to terrestrial vegetation, although
the use of the δ
15N value as a terrestrial end member at spawning sites is limited. If the relationship between the enrichment index, which
is expressed as the values using a mixing model, and salmon abundance was estimated, the availability of MDN in riparian ecosystems
could possibly be evaluated and will lead to the establishment of escapement goals.
An erratum to this article is available at . 相似文献
13.
The effects of different planting densities (250,000, 500,000 and 750,000 plants ha−1) and cutting frequencies (45, 60 and 75 days) on the biomass production and chemical composition of Moringa oleifera was studied in a completely randomised split plot design with four blocks, in Managua, Nicaragua, located geographically
at 12°08′15′′ N and 86°09′36′′ E. The 75 day cutting frequency produced the highest fresh matter yield, 100.7 and 57.4 Mg ha−1 year−1, and dry matter (DM) yield, 24.7 and 10.4 Mg ha−1 year−1, during the first and second year, respectively. All planting densities produced the highest DM yield at 75 day cutting frequency.
In the first year, the density of 750,000 plants ha−1 produced the highest fresh matter yield, 88.0 Mg ha−1 and highest DM yield, 18.9 Mg ha−1, but in the second year the density of 500,000 plants ha−1 gave the highest yields, 46.2 Mg ha−1 and 8.1 Mg ha−1, respectively. During the first year, DM (22.8%), neutral detergent fibre (NDF) (30.8%) and ash (9.14%) contents were highest
and in vitro DM digestibility (IVDMD) (68.2%) was lowest in the longest cutting interval, while contents of crude protein (CP) (22.8%)
and acid detergent fibre (ADF) (22.8%) were not affected significantly by cutting frequency. In the second year, DM and CP
contents and IVDMD were not significantly affected by cutting frequency, whereas NDF, ADF and ash contents were lowest in
the 60 day cutting frequency. Planting density had no significant effect on chemical composition or IVDMD. These data suggest
that Moringa forage could be an interesting protein supplement for ruminants. 相似文献
14.
Yasutaka Watanabe Rie Mihara Tohru Mitsunaga Tsuyoshi Yoshimura 《Journal of Wood Science》2005,51(5):514-519
Fractions of methanol and ethanol extracts from the heartwood of white cypress pine (Callitris glaucophylla Thompson et Johnson) were investigated for their repellent activity against subterranean termite Coptotermes formosanus Shiraki worker using a two-choice semicircular filter paper test at 0.5% (w/w) concentration. Fraction CY-E2 composed of
(−)-citronellic acid, guaiol, α-, β-, and γ-eudesmol isomers as well as an unknown compound, showed the highest statistically significant repellency (97.8% ± 2.2 SEM)
of all fractions tested. Bioactivity-guided fractionations using high-performance liquid chromatography led to the isolation
of two, oxygenated eudesmane-type sesquiterpenes with α-methylene moieties, both termite-repellent compounds. These compounds were subsequently identified as ilicic acid methyl
ester (IAME) and costic acid by means of spectroscopic analyses, electron impact mass spectrometry, and nuclear magnetic resonance
spectroscopy. We report the isolation of both IAME and costic acid from C. glaucophylla heartwood for the first time.
Part of this paper was presented at the 47th Symposium on the Chemistry of Terpenes, Essential Oils, and Aromatics, Tokyo,
November 2003 相似文献
15.
To analyze the effects of lignin on the destabilization of wood due to quenching, we examined the dielectric properties of
untreated and delignified wood before and after quenching at 20°C from 50 Hz to 100 MHz. For untreated wood, the inflection
points of log ε′ and log σ vs log f and the peak of log(tan δ) vs log f were attributed to interfacial polarization before quenching, and the location of the inflection point shifted to a higher
frequency with increasing moisture content because of changes in the water cluster. After quenching, the inflection points
of log ε′ and log σ and the peak of log(tan δ ) shifted to higher frequency; however, the values of log ε′, log σ recovered to those before quenching with the passage of time. For delignified wood, dielectric relaxation was observed at
a higher frequency than for untreated wood irrespective of quenching. It was inferred that the mobility of water molecules
was influenced by the cluster surroundings because of increased number of adsorption sites in hemicellulose. Moreover, after
quenching, the recovery process did not change greatly over time; it was shown that the matrix structure was affected more
by quenching with the loss of lignin. 相似文献
16.
Gmelina arborea Roxb. is a fast-growing species and is known to have been used in traditional Indian medicine. Chemical constituents from
the bark have not been reported, although some chemical constituents from part of this plant (heartwood, leaf, and root) are
known. In this study, the bark meal was successively extracted with acetone and methanol. Fractionation of the acetone extract
with n-hexane, diethyl ether, and ethyl acetate and subsequent chromatographic separation of the fractions led to the isolation
of four compounds. The diethyl ether-soluble fraction yielded tyrosol [2-(4-hydroxyphenyl)ethanol] (1); (+)-balanophonin (2), an 8-5′ neolignan, with opposite optical rotation to known (−)-balanophonin; and gmelinol (3), a known lignan. The ethyl acetate-soluble fraction afforded a new phenylethanoid glycoside to the best of our knowledge,
which was identified as (−)-p-hydroxyphenylethyl[5′″-O-(3,4-dimethoxycinnamoyl)-β-d-apiofuranosyl(1′" → 6′)]-β-d-glucopyranoside (4). From the methanol extract, two known compounds, 2,6-dimethoxy-p-benzoquinone (5) and 3,4,5-trimethoxyphenol (6), were isolated and identified. The 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging assay of the identifi ed
compounds indicated that 3,4,5-trimethoxyphenol (6) exhibited moderate activity.
Part of this report was presented at the 57th and 58th Annual Meetings of the Japan Wood Research Society, Hiroshima and Tsukuba,
August 2007 and March 2008, respectively 相似文献
17.
Karen M. Barry Rie Mihara Noel W. Davies Tohru Mitsunaga Caroline L. Mohammed 《Journal of Wood Science》2005,51(6):615-621
The heartwood of Acacia mangium is vulnerable to heart rot and this is the first study to investigate the role of heartwood extractives in its susceptibility.
Acacia auriculiformis was compared with A. mangium because it is rarely associated with heart rot. The heartwood extracts of both species were dominated by three flavonoids
(2,3-trans-3,4′,7,8-tetrahydroxyflavanone, teracacidin, and 4′,7,8,-trihydroxyflavanone), which were purified and identified by nuclear
magnetic resonance spectroscopy. The latter compound has not been previously reported in A. mangium and evidence for melacacidin is also newly reported. The mass spectrometric (MS) behavior of these compounds is given, for
example teracacidin does not form molecular ions by either electrospray ionization or atmospheric-pressure chemical ionization.
The nature of Acacia tannins was compared to quebracho tannin (composed of profisetinidins) using oxidative cleavage to enable MS detection but
a negative reaction was obtained for both, which suggests the Acacia tannins may also be of the 5-deoxy proanthocyanidin type. The concentration of flavanones was less when A. mangium heartwood was decayed but the amount of proanthocyanidins was only slightly reduced and therefore these compounds may be
more resistant to degradation by heart rot fungi. We found that the total phenol content of A. auriculiformis was about fivefold that of A. mangium, and, while preliminary, this provides evidence for a role played by phenolic extractives in heart rot resistance of these
Acacia species. 相似文献
18.
Sugi green logs with red or black heartwood were smoke-heated, and the changes in the color of the heartwood after ultraviolet
(UV) (λ = 365 nm) radiation exposure were then observed. After UV radiation exposure, the redness and yellowness increased in both
the red and black heartwoods, whereas the brightness decreased. In the black heartwood, the resulting color turned from yellowish
white to reddish brown. Reddening in black heartwood after exposure to a combination of smoke heating and UV radiation is
thought to be due to a decrease in brightness and an increase in both redness and yellowness. However, the degree of change
in heartwood color by UV radiation exposure was not greatly affected by smoke-heating treatments of various lengths. When
methanol extracts were fractionated and exposed to UV radiation, the yellowness increased in the n-hexane-soluble portion and the redness increased in the acetone-soluble fractions from the n-hexane-insoluble portion. These results suggest that the n-hexane-soluble fraction contains the substances that allow heartwood color to change to yellow after UV radiation exposure,
and the acetone-soluble-fraction from the n-hexane-insoluble portion contains the substances that allow it to change to red.
Received: November 14, 2001 / Accepted: June 3, 2002
Acknowledgment This research was supported in part by a Grant-in-Aid for Scientific Research from the Japan Society for the Promotion of
Science.
This study was presented in part at the 51st Annual Meeting of the Japan Wood Research Society, Tokyo, April 2001
Correspondence to:N. Yoshizawa 相似文献
19.
Nitrogen inputs from biological nitrogen fixation contribute to productivity and sustainability of agroforestry systems but
they need to be able to offset export of N when trees are harvested. This study assessed magnitudes of biological nitrogen
fixation (natural 15N abundance) and N balance of Acacia mangium woodlots grown in farmer’s fields, and determined if N2 fixation capacity was affected by tree age. Tree biomass, standing litter, understory vegetation and soil samplings were
conducted in 15 farmer’s fields growing A. mangium as a form of sequential agroforestry in Claveria, Misamis Oriental, Philippines. The trees corresponded to ages of 4, 6,
8, 10 and 12 years, and were replicated three times. Samples from different plant parts and soils (0–100 cm) were collected
and analyzed for δ15N and nutrients. The B-value, needed as a reference of isotopic discrimination when fully reliant on atmospheric N, was generated by growing A. mangium in an N2-free sand culture in the glasshouse. Isotopic discrimination occurring during N2 fixation and metabolic processes indicated variation of δ15N values in the order of nodules > old leaves > young leaves > stems > litterfall and roots of the trees grown in the field,
with values ranging from −0.8 to 3.5‰ except nodules which were enriched and significantly different from other plant parts
(P < 0.0001). Isotopic discrimination was not affected by tree age (P > 0.05). Plants grown in N free sand culture exhibited the same pattern of isotopic discrimination as plants grown in the
field. The estimated B-value for the whole plant of A. mangium was −0.86‰. Mature tree stands of 12 years accumulated up to 1994 kg N ha−1 in aboveground biomass. Average proportion of N derived from N2 fixation of A. mangium was 54% (±22) and was not affected by age (P > 0.05). Average yearly quantities of N2 fixed were 128 kg N ha−1 in above-ground biomass amounting to 1208 kg N fixed ha−1 over 12 years. Harvest of 12-year old trees removed approximately 91% of standing aboveground biomass from the site as timber
and fuel wood. The resulting net N balance was +151 kg N ha−1 derived from remaining leaves, twigs, standing litter, and +562 kg N ha−1 when tree roots were included in the calculation. The fast growing A. mangium appears to be a viable fallow option for managing N in these systems. However, other nutrients have to be replaced by using
part of the timber and fuel wood sales to compensate for large amounts of nutrient removed in order for the system to be sustainable. 相似文献
20.
Sheng-Yang?Wang Jyh-Horng?Wu Sen-Sung?Cheng Chiu-Ping?Lo Hsing-Ning?Chang Lie-Fen?Shyur Shang-Tzen?Chang
Calocedrus formosana Florin (Cupressaceae) is an endemic tree to Taiwan. To evaluate the antioxidant activity of the plant extracts from heartwood, bark, and leaf of C. formosana, assays for 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and superoxide anion scavenging activities, as well as prevention of DNA strand cleavage were performed in this study. Similar IC50 values against the DPPH radical were found for the heartwood and bark extracts at approximately 23µg/ml. Moreover, the heartwood extract exhibited the highest inhibitory activity against superoxide radicals among the test samples; a 2.3-fold lower value of IC50 for superoxide radical inhibition was found in the heartwood extract relative to that of (+)-catechin. Much less effect on inhibition of DPPH and superoxide radicals was found from the leaf extract of C. formosana. More than 70% of superoxide radicals were inhibited in the presence of 10µg/ml heartwood extract, whereas only 15% inhibition was obtained from the leaf extract. The heartwood extract, at a dose of approximately 0.5mg/ml, apparently completely prevented the X174 supercoiled DNA cleavage induced by ultraviolet photolysis of H2O2, as judged by agarose gel electrophoresis. This report also suggests that the antioxidant activities of the plant extracts of C. formosana are in good correlation with their phenolic contents. 相似文献