Showing papers on "Bark published in 1993"

Identification of an adhesive used to repair a Roman jar

Abstract: A combination of micro-analytical techniques, including thin layer chromatography (TLC), gas chromatography (GC), and combined gas chromatography/mass spectrometry (GC/MS), was employed to study the lipid composition of an adhesive used to repair an Ecton ware jar, recovered from Roman sediments of the River Nene at West Cotton (Rounds, Northamptonshire, U.K.). GC of the total lipid extract of the adhesive showed a complex pattern which was difficult to interpret. TLC was used to fractionate the extract. The fractions were then trimethylsilylated and submitted to GC and GC/MS. Betulin, lupeol, lupenone, allobetul-2-ene, and several other pentacyclic triterpenoid compounds were shown to be present in the ancient material. The similarities between the lipid compositions of the adhesive and of contemporary birch bark tar and a birch bark total lipid extract led to the conclusion that the adhesive was derived largely from birch bark, thus providing the first firm evidence for the use of birch bark tar in ancient Britain.

Taxol and related taxanes. I. Taxanes of Taxus brevifolia bark.

Abstract: The published procedures for the isolation of taxol from the Pacific yew (Taxus brevifolia) and other species of Taxus are cumbersome, and the yields of taxol are in the range of 0.0075–0.01%. This paper describes a simple and efficient procedure for the isolation of taxol and its major natural analogues from the bark of T. brevifolia consisting of a single chromatographic column (using silica gel, Florisil, or a reverse-phase C18-silica), followed by crystallization. Isolated yields of taxol from five “pooled” bark samples (blended from many different batches by the supplier) were in the range of 0.02–0.04%, and from bark collected from a more restricted locale, yields reached 0.06%. The procedure also yielded taxol analogues, such as 10-deacetylbaccatin III (0.02–0.04%), 10-deacetyltaxol-7-xyloside (0.06-0.1%), taxol-7-xyloside (0.005–0.01%), 10-deacetyltaxol (0.01–0.02%), 10-deacetylcephalomannine-7-xyloside (0.006–0.01%), and cephalomannine (0.005–0.007%). Of these, 10-deacetyltaxol-7-xyloside is the most abundant taxane in the Pacific yew bark.

Attacks of bark- and wood-boring Coleoptera on snow-broken conifers over a two-year period.

Abstract: The attacks of bark‐ and wood‐boring Coleoptera on broken conifer stems after severe snow‐breakage in early 1988 were studied in autumn 1988 and 1989. The study included twelve stands in the county...

Effects of drought on the induced defence reaction of Scots pine to bark beetle-associated fungi

Abstract: Summary — Water stress was imposed on Scots pine saplings grown in a greenhouse. Predawn leaf water potential (ψwas monitored regularly while carbohydrate reserves were quantified in the phloem, xylem and shoots. Trees were inoculated in the bole with a bark beetle-associated fungus at 4 different periods of the year; the induced defence reaction was quantified 2-3 wk later by its length and the total amount of resin. A decrease in the induced reaction (length and resin quantity) was observed in the most severely stressed trees. However, no clear relationship could be established between the concentration of carbohydrates (soluble or hydrolysable) and the intensity of the defence reaction.

Use of Eucalyptus and Acacia mollissima Bark Extract-Formaldehyde Adhesives in Particleboard Manufacture

Abstract: In this work we have studied the possibility of utilization, in adhesives manufacture, of the tannin extracts of E. astringens and £. sideroxylon and those of Acacia decnrrens, formerly mollissima^ barks issuing from Moroccan afforestation. To overcome the high viscosity and to improve the reactivity of these extracts, treatment with sulfite ions arc realized in the current study. Before that, the average molecular weight of acctylatcd extracts, before and after treatment, were estimated by size exclusion chromalography (SEC) analysis. The reactivity characteristics of these products were determined by differential scanning calorimetry (DSC). The results obtained from tannin-formaldehyde adhcsivcs were compared with those obtained with phenol-formaldehyde (PF) synthetic resin and to values recommended for exterior particlcboards by ACNOR standards. The obtained results from this study shows that the sulfonation of these extracts results in a significant reduction of their molecular weight and their viscosity. The enthalpic analysis shows that the glue mixtures based on tannins give almost the same kinetic parameters values, although slightly less performant, than those obtained with PF resin. The results obtained for laboratory boards prepared with mixtures of tannin-formaldehyde show that the obtained values from internal bond tests are above those of Canadian standard but the formulations obtained from Eucalyptus tannins yield an insufficient water resistance.These results arc broadly in accord with those stipulated by the ACNOR standard for the particlcboards formed with urea-formaldehyde resin, and consequently, these formulations can be used in interior applications, where the water resistance is not specified.

The Essential Oils of Rhus coriaria L. (Sumac)

Abstract: The essential oils obtained from the leaf, fruit pericarp and branch/bark of Rhus coriaria L. by hydrodistillation were examined by GC and GC/MS. Sixty-three constituents in the branch/bark oil, sixty-three constituents in the leaf oil and eighty-five constituents in the fruit pericarp oil were identified. The predominant compounds in the pericarp oil were limonene (0.17–9.49%), nonanal (10.77–13.09%) and (Z)-2-decenal (9.90–42.35%), while major components of the leaf oil were β-caryophyllene (0.33–16.95%) and a sesquiterpene hydrocarbon tentatively identified as patchoulane (3.08–23.87%). The major constituents of the branch/bark oil were β-caryophyllene (12.35–21.91%) and cembrene (10.71–26.50%). The composition of oils from two different phytogeographic regions showed variations.

Influence of Dust from a Limestone Quarry on Chlorophyll Degradation of the Lichen Physcia adscendens (Fr.) Oliv.

Abstract: Dust is among the substances usually referred to as pollutants affecting lichen growth and occurence. Dust splashed or blown on to roadside trees and shrubs usually leads to a reduction of bark acidity, thus encouraging lichen assemblages characteristic of plants with alkaline bark (i.e., Xanthorion) (Hawksworth and Rose 1976). Dust from limestone quarries and cement and lime works is also alkaline and has the same neutralizing effect on bark, promoting the development of lichen species normally confined to limestone rocks (e.g., Physcia spp., Xanthoria spp.). A number of methods are used to estimate the effect of airborne pollutants on lichens. Changes in the rate of photosynthesis, chlorophyll content and chlorophyll degradation are normally more informative than parameters such as species composition and cover (De Wit 1983).

Bark: The Formation, Characteristics and Uses of Bark Around the World

Abstract: Bark: the formation, characteristics, and uses of bark around the world , Bark: the formation, characteristics, and uses of bark around the world , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

Pruning enhances the susceptibility of Picea abies to infection by the bark beetle‐transmitted blue‐stain fungus, Ophiostoma polonicum

Abstract: Defoliation of conifers occasionally precedes bark beetle attacks, suggesting that a severe loss of foliage and ensuing reductions in carbohydrate availability may enhance host tree susceptibility. To shed light on this question, different degrees of defoliation on young Picea abies were simulated by removing whole whorls of branches from below, the trees retaining 100, 50, or 25% of their original crown biomass. After one week or one year, the trees were inoculated with Ophiostoma polonkum, a tree‐killing fungus transmitted by Ips typographus. Fungal proliferation and tree mortality increased with increasing levels of pruning. Pruning reduced stem diameter growth, but not carbohydrate reserves in foliage and bark. Foliar N, P, and Ca increased with increasing pruning. The results lend support to the hypothesis that a reduction in the photosynthesis capacity increases host tree susceptibility to a beetle‐fungus attack, and that induced defence against infection depends on efficient translocation of assimi...

Sequence of a poplar bark storage protein gene.

Abstract: Temperate deciduous tree species retranslocate nitrogen from leaves to storage sites during the fall and remobilize stored nitrogen during the spring to support new shoot growth (Taylor and May, 1967; Ryan and Bormann, 1982). The majority of reserve nitrogen is stored as protein (Kang and Titus, 1980; Chapin and Kedrowski, 1983). In poplar, a 32-kD BSP that accumulates in the protein storage vacuoles of the inner bark parenchyma during autumn and winter has been described (Wetzel et al., 1989). The accumulation of poplar BSP is associated with short days (Coleman et al., 1991). SD accumulation of poplar BSP is also correlated with a large increase in the steady-state levels of BSP mRNA (Coleman et al., 1992). DNA gel blot analysis suggests that poplar BSP is encoded by a small multigene family. As part of our effort to understand nitrogen recycling and photoperiod control of BSP gene expression, we have isolated and sequenced a gene encoding a poplar BSP (Table I). A genomic library was prepared in the vector XGem-11 (Promega, Madison, WI) and screened at low stringency (approximately 25OC below Tm) using a poplar BSP cDNA (Coleman et al., 1992). Twelve positive clones were identified and rescreened with different regions of the BSP cDNA at high stringency (approximately 5OC below Tm). One positive clone (designated bspA) was isolated and subcloned into pBluescriptII SK (Stratagene, La Jolla, CA), and the nucleic acid sequence was determined. The poplar BSP gene was contained within a 3.9-kb EcoRVl AflII fragment, which included a 1646-bp coding region, 1246 bp upstream of the coding region and 1022 bp downstream of the coding region. The open reading frame was interrupted by four introns 152, 262, 175, and 144 nucleotides in length. A putative TATA sequence is located at nucleotides 1145 to 1151 and the transcriptional start site (as determined by primer extension) is located at nucleotide 1175. The DNA sequence is 99% identical with the BSP cDNA, and the decoded amino acid sequence is 97% identical with the amino acid sequence of the poplar BSP cDNA.

Analysis of archaeological birch bark pitches

Abstract: Dark lumps, thought to be pitch or resin used for caulking wooden funerary vessels, were excavated from four graves in Finland (dated between 1900 and 2200 BC). Gas chromatography-mass spectrometry was used to analyze distillates from both the archaeological samples and reference samples of bark pitch from various trees. There was a close similarity between results for the archaeological samples and those for birch ( Betula verrucosa (B. pendula) ) bark pitch.