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Showing papers on "Bark published in 1998"


Journal ArticleDOI
TL;DR: Results from the in vitro antiamoebic activity of some Congolese plant extracts used as antidiarrhoeic in traditional medicine indicated that of 45 plant extracts tested, 35 (77.78%) exhibited an antiamoscular activity and 10 (22.22%) were inactive.

481 citations


Journal ArticleDOI
TL;DR: This study confirms that C. polonica, an associate of the aggressive bark beetle Ips typographus, is pathogenic to Norway spruce, and shows that some nonaggressive bark beetles may vector phytopathogenic fungi.
Abstract: The pathogenicity of two isolates of each of four bark beetle-associated blue-stain fungi was evaluated after mass inoculation of about 40-year-old Norway spruce trees (Picea abies) Trees

159 citations


Journal ArticleDOI
TL;DR: Considering its timing and magnitude, this previously undescribed response may be important in modulating interactions between pine trees and bark beetles, and in addition, resin flow following treatment was greater in trees in l...
Abstract: The oleoresin produced by many conifers has a deleterious effect on numerous associated herbivores, including bark beetles (Coleoptera: Scolytidae), and may have evolved as a plant defense mechanism. Three experiments with juvenile loblolly pine (Pinus taeda L.) used mechanical wounding to drain resin reserves and assess the effects of prior bark wounding on subsequent resin flow up to 7 days post-treatment. Resin flow returned to pre-treatment values within 2 days after wounding began and, in nearly every tree in each experiment, continued to increase on subsequent days. On average, resin flow reached double the pre-treatment values (mean ± SE: 2.10 ± 0.10 vs. 1.13 ± 0.10 g/3 h and 2.28 ± 0.09 vs. 0.90 ± 0.09 g/3 h for wounded vs. pre-treatment in experiments 1 and 2, respectively). Considering its timing and magnitude, this previously undescribed response may be important in modulating interactions between pine trees and bark beetles. In addition, resin flow following treatment was greater in trees in l...

104 citations


Journal Article
TL;DR: An inoculation experiment with Heterobasidion annosum on 98 four-year-old Picea abies clones was conducted on rooted cuttings under greenhouse conditions and fungus growth and lesion length showed strong genotypic correlation.
Abstract: An inoculation experiment with Heterobasidion annosum on 98 four-year-old Picea abies clones was conducted on rooted cuttings under greenhouse conditions. One isolate of H. annosum and 10 ramets of each clone were used. After 34 days of incubation, fungal growth in sapwood and lesion length in the inner bark were measured. There were significant differences among clones in lesion length in the inner bark and in fungal growth in sapwood. Broad sense heritability was 0.35 for fungal growth and 0.27 for lesion length in the inner bark. Fungal growth and lesion length showed strong genotypic correlation. Bud-flushing index of the clones was correlated with mean fungal growth, whereas the growth termination index was not. Fungal growth in sapwood and lesion length in the inner bark of cuttings were not correlated with the mean height and provenance of 15-year-old ramets of the same clones in previously conducted field tests.

78 citations


Journal ArticleDOI
TL;DR: The results support the hypothesis that such bark beetles are adapted to recognize and avoid non-host angiosperm trees by responding to a broad spectrum of volatiles that can act in various blends with equal effect.
Abstract: Coupled gas chromatographic-electroantennographic detection (GC-EAD) analysis of the Porapak Q-captured volatiles from the bark of trembling aspen, Populus tremuloides Michx., revealed four compounds that consistently elicited antennal responses by mountain pine beetles (MPBs), Dendroctonus ponderosae Hopkins. One of these, 1-hexanol, disrupted the capture of MPBs in multiple-funnel traps baited with the aggregation pheromones trans-verbenol and exo-brevicomin and the host kairomone myrcene, a blend of semiochemicals that mediates the secondary attraction response in which beetles mass attack and kill living pines. The other three EAD-active aspen bark volatiles, benzyl alcohol, benzaldehyde and nonanal, were inactive alone, but in binary and ternary combinations contributed to a disruptive effect in an additive and redundant manner when all four aspen bark volatiles were tested in all possible binary and ternary blends. The best ternary blend and the quarternary blend achieved ≥ 80% disruption. The quarternary blend enhanced the disruptive effect of the antiaggregation pheromone verbenone in traps, raising the disruptive effect to 98%, and also enhanced the inhibition of attack on attractant-baited lodgepole pines. This is the first demonstration of specific compounds from the bark of angiosperm trees that disrupt the secondary attraction response of sympatric coniferophagous bark beetles. The results support the hypothesis that such bark beetles are adapted to recognize and avoid non-host angiosperm trees by responding to a broad spectrum of volatiles that can act in various blends with equal effect.

77 citations


Journal ArticleDOI
TL;DR: Investigation of the bark from Terminalia macroptera led to the isolation of two novel esterified triterpenes, identified as 23-galloylarjunolic acid and its β- d -glucopyranosyl ester.

66 citations


Journal ArticleDOI
TL;DR: Wood inhabiting fungi were investigated in a stand of Picea abies (L.) Karst.

65 citations


Journal Article
TL;DR: The methylation of two hydrozyl groups in the Ficus flavonoids might have slowed down their antioxidant action as compared to quercetin, which may be attributed to their polyphenolic nature.
Abstract: Two flavonoid compounds, viz 5,7-dimethyl ether of leucopelargonidin 3-0-alpha-L rhamnoside and 5,3'-dimethyl ether of leucocyanidin 3-0-alpha-D galactosyl cellobioside obtained from the bark of F bengalensis were evaluated for their antioxidant action in hyperlipidemic rats The results were compared with the activity of a structurally similar flavonoid, quercetin, a known antioxidant The Ficus compounds showed significant antioxidant effects which may be attributed to their polyphenolic nature The methylation of two hydrozyl groups in the Ficus flavonoids might have slowed down their antioxidant action as compared to quercetin

60 citations


Journal ArticleDOI
TL;DR: Through bioassay-guided chromatographic fractionation, liriodenine, an oxoaporphine alkaloid, was isolated from the bark extracts as the bioactive compound.
Abstract: Extracts obtained from leaves, seeds and bark of Unonopsis lindmanii were evaluated by means of Brine Shrimp Lethality test (BSL). Through bioassay-guided chromatographic fractionation, liriodenine, an oxoaporphine alkaloid, was isolated from the bark extracts as the bioactive compound. Two additional inactive known alkaloids, unonopsine and lysicamine were also isolated from the bark extracts.

55 citations



Journal ArticleDOI
TL;DR: In this article, the relationship between the concentration of Al and other elements in leaves and the other five elements, such as Ca, Mg, P, S, and Si in trees in a tropical rain forest in West Sumatra were studied.
Abstract: Mineral composition including AI, Ca, Mg, P, S, and Si and relationships between Al and other elements such as Ca, Mg, P, S, and Si in leaves and bark of trees in a tropical rain forest in West Sumatra were studied. Sixty five tree species and 12 unidentified trees were referred to as AI accumulators based on Chenery\s's definition (more than 1 g kg-1 Al in leaves). For most of the Al accumulators, Al concentration in leaves was higher than in bark. However, some members of Euphorbiaceae, Melastomataceae, and Ulmaceae families showed a reverse trend. Most of the non-accumulators also showed a higher Al concentration in bark than in leaves. These results indicated that there was a difference in the mechanism of Al accumulation in tree bodies. Some of the Al accumulators showed an extremely high Al concentration (more than 10 g kg-1) not only in the mature leaves, but also in the new leaves. Analysis of the relationships between the concentration of Al and the other 5 elements in leaves, revealed t...


Journal ArticleDOI
TL;DR: In this paper, the core and bark of kenaf (Hibiscus cannabinus), variety Salvador, were characterized by 13 C and 1 H NMR, FTIR, and UV spectroscopies, permanganate oxidation, and alkaline hydrolysis followed by GC and GC-MS analysis of the released products.
Abstract: Dioxane and milled wood lignins were isolated from the core and bark of kenaf (Hibiscus cannabinus), variety Salvador. These lignins were characterized by 13 C and 1 H NMR, FTIR, and UV spectroscopies, permanganate oxidation, and alkaline hydrolysis followed by GC and GC-MS analysis of the released products and by functional groups analysis. The permanganate oxidation and alkaline hydrolysis was also applied to “in situ” lignins. Isolated and “in situ” lignins showed significant differences in composition and structure. Strong structural differences were observed between bark and core lignins, suggesting their different biosynthetic routes. The ‚-O-4 type linkages are the main interunit linkages and are more abundant in bark than in core lignin. The core lignin is more “condensed” and shows higher contents of ‚-‚ plus ‚-5 linkages than those in the bark lignin. Permanganate oxidation showed that both core and bark “in situ” lignins are HGS-type lignins with HGS proportions of 15:66:19 and 12:56:32, respectively (H including coumarate structures in the case of core lignin). Coumarates represent about 50% of the H units of core lignin and are absent in bark lignins. The presence of suberin-like aliphatic chains covalently bound to lignin was suggested for bark lignin.

Journal ArticleDOI
TL;DR: The volatile fractions, obtained by water distillation from the leaves and bark of Hamamelis virginiana L. virginiana were analysed in detail by GC-MS and the chemical composition of the volatiles emphasizes the definition "volatile fraction" rather than "essential oil".
Abstract: The volatile fractions, obtained by water distillation from the leaves and bark of Hamamelis virginiana L. were analysed in detail by GC-MS. About 175 (leaves) and 168 (bark) compounds have been identified or at least partly characterized on the basis of a computerized database (SeKoMS). The dominating substances were represented by a homologous series of alkanes, alkenes, aliphatic alcohols, related aldehydes, ketones, and fatty acid esters. Importantly, significant differences in the terpenoid and phenylpropanoid patterns of the products obtained from the bark and leaves are apparent: whereas the product of bark distillation was found to typically contain phenylpropanoids and mainly sesquiterpenoids, that obtained from the leaves included some distinct monoterpenoids detected in comparably higher amounts. The chemical composition of the volatiles, when taken together with the absence of specific accumulation sites of lipophilics, emphasizes the definition "volatile fraction" rather than "essential oil".

Journal ArticleDOI
TL;DR: Three new naphthalenes, designated as Syriacusins A-C, were isolated from the root bark of Hibiscus syriacus and showed cytotoxicity against some human cancer cell lines with an ED50 of 1.5-2.4 micrograms ml-1.

Journal ArticleDOI
TL;DR: Eight daphnane-type diterpenoids, wikstroelides H-O, were isolated from the bark and stem, and their structures established, and Cytotoxicity was assayed on some wik Stroelides.

Journal ArticleDOI
TL;DR: The root bark of Newbouldia laevis afforded withasomnine, 4'-hydroxywithasomNine, 4-methoxywithasOMnine, newbouldine, 4'hydroxynewbouldines, and 4'-methoxynewBouldine are new natural products.
Abstract: The root bark of Newbouldia laevis afforded withasomnine, 4'-hydroxywithasomnine, 4'-methoxywithasomnine, newbouldine, 4'-hydroxynewbouldine, and 4'-methoxynewbouldine. 4'-Methoxywithasomnine and 4'-methoxynewbouldine are new natural products.

Journal ArticleDOI
TL;DR: An increase in the nutritional quality of bark following wounding appears to be the main factor influencing attacks on wounded trees by D. micans, confirming the importance of lignin as a preformed defence in living trees.
Abstract: The effect of lignified stone cell masses (lignin) and mechanical wounding of bark on gallery formation and oviposition by the spruce bark beetle, Dendroctonus micans, was determined in plantations of Norway and Sitka spruce. When beetles were implanted onto trees that varied in bark lignin concentration, there was a significant negative relationship between lignin and adult gallery size. Only a few larval galleries were established, all of them on trees with a low lignin concentration. Results confirm the importance of lignin as a preformed defence in living trees. Adults excavated significantly larger galleries in wounded than unwounded bark. Most larval galleries were also established in wounded bark. The concentrations of nitrogen, carbohydrate, and resin and the moisture content of wounded and unwounded bark were measured at the beginning of the experiment. A number of significant changes were induced by wounding, including an increase in the concentration of nitrogen and starch, and decreases in the moisture content and the concentration of free sugars. There was no overall effect of wounding on resin content of bark, although concentrations were significantly lower in new than old wounds. An increase in the nutritional quality of bark following wounding appears to be the main factor influencing attacks on wounded trees by D. micans.

Journal ArticleDOI
01 Feb 1998-Botany
TL;DR: Yeasts and filamentous fungi associated with smooth (non-lenticel) and lenticel bark of young and scaffold branches of peach (Prunus persica) were monitored using bark washing and direct or impression plating techniques and scanning electron microscopy during potential Cystospora canker infection periods.
Abstract: Yeasts and filamentous fungi associated with smooth (non-lenticel) and lenticel bark of young and scaffold branches of peach (Prunus persica (L.) Batsch) were monitored using bark washing and direct or impression plating techniques and scanning electron microscopy during potential Cystospora canker infection periods. Total populations of fungi were high in the fall but dropped in the winter and increased during the spring. Yeasts and yeast-like fungi predominated in the spring and fall samples. The principal yeasts were Basidiomycetes in the form genera Cryptococcus, Rhodotorula, and Sporobolomyces. The yeast-like fungi were Aureobasidium and Taphrina. The principal filamentous fungi were in the form genera Alternaria, Epicoccum, Cladosporium, Coniothyrium, and Libertella. The canker pathogens, Leucostoma persoonii (Nits.) Hohn. and Leucostoma cincta (Pers. & Fr.) Hohn., were observed mainly in the spring sampling. Lenticels supported greater fungal populations than smooth (non-lenticel) bark surfaces. Th...

Journal ArticleDOI
TL;DR: Two spirobiflavonoids, daphnodorins M and N, were isolated from the roots and the bark of Daphne acutiloba and their structures established by spectral and chemical means.

Journal ArticleDOI
TL;DR: In this paper, a method was proposed to accurately and rapidly determine the gravimetric bark content of a cotton sample. But, the method is not suitable for coarse-grained textured textured images and it has an estimated error of 0.46%.
Abstract: A method is needed to accurately and rapidly determine the gravimetric bark content of a cotton sample. Gravimetric bark content represents the percent bark mass through out the volume of a cotton sample. The current method for measuring gravimetric bark content is a labor intensive, lengthy process. Machine vision, on the other hand, is a fast, inexpensive method to measure this bulk cotton property. Ten acquired images of surfaces throughout each sample are used. Classical digital image processing tech niques isolate foreign matter regions in monochrome video images. Geometric prop erties (area and perimeter) are used to identify which foreign matter is bark and to predict the gravimetric bark content in forty-eight cotton samples with varying bark and total foreign matter content. We suggest a model with six features and intercept, which has an estimated error of 0.46% bark mass.

Journal Article
TL;DR: The effects of water salinity on Phalaenopsis orchids grown in 100% fine-grade fir bark or a combination of 80% bark and 20% sphagnum peat were studied and flower diameter decreased slightly as salinity increased, but had fewer flowers than those grown in bark/peat.
Abstract: The effects of water salinity [0.05, 0.40, 0.75, 1.10, and 1.40 dS.m -1 of electrical conductivity (EC)] on Phalaenopsis orchids grown in 100% fine-grade fir bark or a combination of 80% bark and 20% sphagnum peat were studied. In both media, flower diameter decreased slightly as salinity increased. Plants in bark had more flowers as salinity increased, but had fewer flowers than those grown in bark/peat. In either medium, salinity had no effect on the number of new leaves produced. As salinity increased, plants in bark had increasingly larger total leaf area, with a maximum at EC = 1.10 dS.m -1 . Leaf area of plants in bark/peat was greater than that of those in bark, but was unaffected by salinity. Root fresh mass was lower with increasing salinity in both media. Media had no effect on mineral concentration in the leaf. In bark, increasing salinity increased the Ca and Na concentrations but had no effect on the concentration of other minerals in leaves. As salinity increased in the bark/peat medium, leaf concentrations of P, Fe, and Cu decreased and those of K, Ca, Mg, Na, and Zn increased, but the concentration of N was unaffected by salinity. Leachate from bark/peat had twice the EC and lower pH (4.9) than bark (5.7).

Journal ArticleDOI
TL;DR: Two new triterpenes were isolated from the leaves of Larix kaempferi together with two known compounds, 24- methylenecycloartanone and 24-methylenecYcloArtanone, and these new compounds were characterized as cycloarts-3,24-dione and lanost-9(11)-en-3alpha,24S,25-triol on the basis of chemical and spectroscopic evidence.

Journal ArticleDOI
TL;DR: Fungi present in the inner bark of the yew tree Taxus yunnanensis were studied for the capability to biotransform natural taxoids and were revealed to be able to selectively hydrolyze and epimerize two taxoids.
Abstract: Fungi present in the inner bark of the yew tree Taxus yunnanensis were studied for the capability to biotransform natural taxoids. On the basis of screening, three fungi, Microsphaeropsis onychiuri, Mucor sp. and Alternaria alternata, were revealed to be able to selectively hydrolyze and epimerize two taxoids, 10-deacetyl-7-epitaxol (1) and 1β-hydroxybaccatin I (2), previously isolated from the bark of the same yew species. After preparative-scale incubation of 10-deacetyl-7-epitaxol with M. onychiuri and Mucor sp., three metabolites were isolated and characterized as 10-deacetylbaccatin V (3), 10-deacetyltaxol (4), and 10-deacetylbaccatin III (5). Incubation of 1β-hydroxybaccatin I with A. alternata, on the other hand, gave 5-deacetyl-1β-hydroxybaccatin I (6), 13-deacetyl-1β-hydroxybaccatin I (7), and 5,13-dideacetyl-1β-hydroxybaccatin I (8).

Journal ArticleDOI
TL;DR: In this paper, screening and isolation of angiotensin I-converting enzyme (ACE) inhibitors from Japanese cedar (Cryptomeria japonica) based on the in vitro ACE inhibitory assay were attempted.
Abstract: Screening and isolation of angiotensin I-converting enzyme (ACE) inhibitors from Japanese cedar (Cryptomeria japonica) based on the in vitro ACE inhibitory assay were attempted. The ethanol extract from outer bark showed the highest inhibitory activity (IC50 is 16μg/ml) among 24 extracts prepared from roots, leaves, heartwood, sapwood, inner bark, and outer bark by successive extraction with four solvents. The fractionation of the outer bark ethanol extract followed by the bioassay resulted in the isolation of two strong ACE inhibitors, catechin and dimeric procyanidin B3. The bioassay of three flavan-3-ols including (+)-catechin and six flavones revealed that most of these compounds have high ACE inhibitory activity. The results suggest that the phenolic hydroxyl group at the C7 position and heterocyclic oxygen atom of these compounds are important for expressing the inhibitory activity.

Journal ArticleDOI
TL;DR: The cambial region is the major source of endogenous ethylene in the 1-year-old shoot and Ethrel-induced increase in tracheid number and bark radial width at the application point is positively related to ethylene evolution from the cambia region and the cortex + periderm, respectively.
Abstract: The terminal (1-year-old) shoot of quiescent, 2-year-old Abies balsamea (L.) Mill. seedlings was either left untreated or ringed with 0, 1 or 10 mg Ethrel g −1 lanolin. After 5 weeks of culture under environmental conditions favorable for growth, the shoots were harvested to measure ethylene evolution and carbohydrate concentrations by gas chromatography, and tracheid number and bark radial width by microscopy. In untreated shoots, the basal rate of ethylene evolution followed the order: cambial region > cortex + periderm = xylem + pith = needles. Wound-induced ethylene production was not detected until at least 4 h after excision, but was evident in all fractions 24 h after excision; the increase in wound-induced ethylene evolution followed the order: cambial region > cortex + periderm > xylem + pith > needles. Compared with untreated controls, the application of plain lanolin, which involved the removal of needles and periderm, increased bark radial width and wound-induced ethylene production by the cambial region and the cortex + periderm, but decreased cambial region concentrations of fructose, glucose and starch at the application point. At the application point, Ethrel concomitantly increased ethylene evolution from the cambial region and the cortex + periderm, tracheid number, bark radial width, and the cambial region concentrations of fructose, glucose, sucrose and starch. No effects of Ethrel treatment were detected above or below the application point, with the exception that the 10 mg g −1 Ethrel treatment stimulated ethylene evolution and decreased starch concentration of the cambial region. The results indicate that: (1) the cambial region is the major source of endogenous ethylene in the 1-year-old shoot; (2) the magnitude of the difference in ethylene evolution between particular shoot fractions is different before and after the start of wound-induced ethylene production; (3) the Ethrel-induced increase in tracheid number and bark radial width at the application point is positively related to ethylene evolution from the cambial region and the cortex + periderm, respectively; and (4) ethylene derived from Ethrel applied laterally to a woody stem can mobilize carbohydrates to the application point.

Journal ArticleDOI
TL;DR: Media components differ greatly in their influence on paclobutrazol activity and the bioassay procedure may serve as a useful tool for predicting media-paclobUTrazol interactions.
Abstract: Three experiments were conducted to evaluate media component effects on paclobutrazol activity. In Expts. 1 and 2, a broccoli (Brassica oleracea var. botrytis L.) seedling bioassay was used to compare the activity of paclobutrazol at six concentrations (0-0.32 mg.L -1 ). Results from Expt. 1 indicated that an average of 4-, 5-, and 10-fold higher concentrations were required in old composted pine bark, fresh pine bark, and composted pine bark samples, respectively, to achieve the same activity observed in sphagnum peatmoss (peat) samples. Activity in coir was similar to that in peat while activity in vermiculite and perlite was greater than that in peat. Activity in a fibrous peat sample was greater than in two less-fibrous peat samples. Results from Expt. 2 indicated that paclobutrazol activity was reduced more in the fine ( 4 mm) fractions. In Expt. 3, petunia (Petunia hybrida Vilm. 'Madness Red') was grown in a mixture of either 60% composted pine bark: 0% peat or 0% composted bark: 60% peat. The paclobutrazol concentration required to achieve the same size control was 14 times higher in the former mixture than in the latter. Thus, media components differ greatly in their influence on paclobutrazol activity and the bioassay procedure may serve as a useful tool for predicting media-paclobutrazol interactions. Chemical name used: (±)-(R * ,R * )-β-[(4-chlorophenyl)methyl]-α-(1,1-dimethyl)- 1H-1,2,4-triazole-1-ethanol (paclobutrazol).

Journal ArticleDOI
TL;DR: Analysis of archaeological bark samples forms another promising application besides pollen data from soil samples, which provide useful information on vegetation composition, and the possible effect of wind direction.

Journal ArticleDOI
TL;DR: The novel diarylheptenone 1-(3',4'-dihydroxyphenyl)-7-(4''-hydroxypenyl)-4- hepten-3-one and 1,7-bis( P-hydrogen-3,4,4-heptene-2-one were isolated from Alnus rubra bark and their structures elucidated by spectrometric techniques.
Abstract: The novel diarylheptenone 1-(3',4'-dihydroxyphenyl)-7-(4''-hydroxyphenyl)-4-hepten-3-one and 1,7-bis( P-hydroxyphenyl)-4-hepten-3-one were isolated from Alnus rubra bark and their structures elucidated by spectrometric techniques.

Journal ArticleDOI
TL;DR: The aims of this study are to describe the wood and bark anatomy and tree ring pattern of Prosopis alba, to analyse tree ring evolution in relation to age and orientation, to characterise sapwood, heartwood and bark width, in comparison to age, DBH (diameter at breast height) orientation, and height and to determine the main defects of the wood.
Abstract: Prosopis alba Griseb., is one of the most important Argentinean Mimosaceae. With a great distribution area, it is a common component in the Chaco Forest. Prosopis alba, "Algarrobo blanco", is one of the Argentina's legumes of more economic importance. The aims of this study are: to describe the wood and bark anatomy and tree ring pattern of Prosopis alba, to analyse tree ring evolution in relation to age and orientation, to characterise sapwood, heartwood and bark width, in relation to age, DBH (diameter at breast height) orientation, and height and to determine the main defects of the wood. The study was carried out in ten individuals from the following sites of Santiago del Estero, Argentina: Brea Pozo, San Martin Department; Las Delicias, Pellegrini Department and Sachayoj, Alberdi Department. Healthy, well formed trees, with more than 30 cm DBH were selected from the dominant-canopy. Wood samples were taken following the methodology of Helinska et al. The terminology by IAWA was used for wood descriptions, and the terminology by Roth in bark. Results obtained show that Prosopis alba has tree ring demarcated by terminal parenchyma (type 2 of Coster). Tree rings have a medium width of 4.05 mm (2.11-5.18), with a maxim between 29 and 32 years. Orientation had no influence on width. Sapwood in the trunk has a tree ring width (2-6), diminishing with age and height. The principal defect of the wood are the scars produced by fire which alter the pattern of growth. The deciduous bark is of the fibrous type, with longitudinal fissures. The thickness of total bark is 1.16 cm, the living bark 0.39 cm and rhytidome 0.74 cm. The bark increases with age and diminishes with DBH. The duraminization process begins between the years 3 to 6.