Some Sources Of Variation In Structural Characteristics Of Douglas-Fir Bark

This study examines variations in structure and formation of Douglas-fir bark. Development of a classification system based on the external appearance of the bark surface that would correlate with anatomical characteristics of the bark was not possible. Modification of bark by fungi was observed to occur in several specific ways, such as attacking cell walls of sclereids, removing contents from lumina of various cell types, and affecting formation of cork layers in regions associated with radial checks and fissures in the bark

The Presence of Callose in Cork Cells

Observations of fluorescence with ultraviolet microscopy and staining with transmission electron microscopy indicate that a substance reacting like callose is present as a plugging material in pitlike areas in the walls of mature cork (phellem) cells

Genetic Variation in The Age of Demarcation Between Juvenile And Mature Wood in Douglas-Fir

Variation in the age of demarcation between juvenile and mature wood based on wood density was studied in 180 Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) trees. Ring density profiles were generated from X-ray densitometry of increment cores from each of 3 randomly selected trees from each of 30 wind-pollinated families (parent trees) grown in 2 replication blocks. The families represented 10 provenances (3 families per provenance). Two boundary points were determined: the age at which a significant change occurred in the slope of the density-age relationship (using piecewise regression techniques), and the age at which species average density was reached. The period of juvenile wood production ranged from 11 to 37 years among the trees sampled. Most of the variation was among trees-within-plots; however, significant differences among families-within-provenances indicated that the period of juvenile wood production for this population of Douglas-fir was under appreciable genetic control

Bound Chlorinated Residue in Chloropicrin-Treated Douglas-Fir

Douglas-fir wafers exposed to chloropicrin vapors, then aerated and heated or extracted with acetone, were analyzed under a scanning electron microscope equipped with an energy dispersive X-ray analyzer. Chlorinated residues appeared to be most concentrated in the middle lamellae and in areas where wood extractives were located, which indicates that the residues were selectively binding to phenolic materials. Thin layer chromatography of acetone extracts of the treated wood suggested that chlorinated residues were binding to extractives, particularly to a portion of the phenolic extractive dihydro-quercetin. Analysis of a mixture of vanillin (a phenolic lignin derivative) and chloropicrin showed the presence of two other compounds. Mass spectroscopy tentatively identified these as CCl3-vanillin and NO2-vanillin. This identification suggests that the chloropicrin molecule was fragmented and that the two components were chemically linked to the vanillin molecule at an unspecified point. The data suggest an explanation for the presence of a phenolic-bound chlorinated residue in chloropicrin-treated wood

Drying and Other Related Properties of Western Hemlock Sinker Heartwood

Sinker heartwood dries more slowly than normal heartwood of western hemlock. Extraction with ethanol or acetone and presteaming improved the rate of drying of sinker heart-wood. Electron microscopy was used to examine bordered pits in normal and sinker heartwood and extracted specimens of sinker heartwood. Parallel capacitance was lowest in sapwood, higher in normal heartwood, and highest in sinker heartwood. The range in capacitance was related to total extractive content at similar moisture contents

Longitudinal Water Permeability of Western Hemlock. I. Steady-State Permeability

Average initial permeability to water of sapwood was found to be 9.6 X 10-10 cm2, that of wetwood from heartwood was 6.64 X 10-10 cm2, and that of normal heartwood was 4.4 X 10-12 cm2. All the specimens were never-dried, approximately 0.95 cm in diameter and 2 cm long, and were embedded in a lucite tube using epoxy resin as binder.Using polyethylene glycol 1000 as an embedding agent, 23% of sapwood pits, 42% of pits in wetwood from heartwood, and 84% of pits in normal heartwood were found to be aspirated. Scanning electron microscopy revealed that the normal heartwood of freeze-dried heartwood was heavily incrusted, but that of wetwood was relatively free of incrustation. High water permeability of wet heartwood was attributed to a low level of pit aspiration and freedom from incrustation.Both sapwood and wetwood exhibited deterioration of permeability with time. In sapwood the cause was considered to be time-dependent pit aspiration because of hydrostatic pressure differentials during testing, but in wetwood the deterioration was attributed to extractives transported by water and deposited on pit membranes to form an impermeable coat of film.A further proposal is that formation of wet pockets during drying of western hemlock lumber is caused by formation of an impermeable zone from the incrustation of pits by extractives during the migration of water, which traps the moisture in lumber

Properties and decay resistance of preservative-treated Douglas-fir flakeboard

The effect of pretreatment of Douglas-fir flakes with CCA-C, borate, and azaconazole on properties of flakeboard was studied. Flakes had higher retention levels of CCA-C and borate in their ends than in their centers. The distribution of chemicals was uniform in panels, which indicates that the chemicals did not migrate during hot-pressing. Treatment markedly enhanced resistance to brown rot (Postia placenta). Borate-treated panels had large thickness swelling and often delaminated when exposed to hot, wet conditions. In static bending and internal bond tests, strength reduction for borate- and CCAC-treated panels was evident. Azaconazole showed no deleterious effect on strength.Keywords: flakeboard, CCA, physical properties, durability, borate, Douglas-fir, azaconazol

Acyl-CoA synthetase 3 promotes lipid droplet biogenesis in ER microdomains

Control of lipid droplet (LD) nucleation and copy number are critical, yet poorly understood, processes. We use model peptides that shift from the endoplasmic reticulum (ER) to LDs in response to fatty acids to characterize the initial steps of LD formation occurring in lipid-starved cells. Initially, arriving lipids are rapidly packed in LDs that are resistant to starvation (pre-LDs). Pre-LDs are restricted ER microdomains with a stable core of neutral lipids. Subsequently, a first round of “emerging” LDs is nucleated, providing additional lipid storage capacity. Finally, in proportion to lipid concentration, new rounds of LDs progressively assemble. Confocal microscopy and electron tomography suggest that emerging LDs are nucleated in a limited number of ER microdomains after a synchronized stepwise process of protein gathering, lipid packaging, and recognition by Plin3 and Plin2. A comparative analysis demonstrates that the acyl-CoA synthetase 3 is recruited early to the assembly sites, where it is required for efficient LD nucleation and lipid storag

A Role for Phosphatidic Acid in the Formation of “Supersized” Lipid Droplets

Lipid droplets (LDs) are important cellular organelles that govern the storage and turnover of lipids. Little is known about how the size of LDs is controlled, although LDs of diverse sizes have been observed in different tissues and under different (patho)physiological conditions. Recent studies have indicated that the size of LDs may influence adipogenesis, the rate of lipolysis and the oxidation of fatty acids. Here, a genome-wide screen identifies ten yeast mutants producing “supersized” LDs that are up to 50 times the volume of those in wild-type cells. The mutated genes include: FLD1, which encodes a homologue of mammalian seipin; five genes (CDS1, INO2, INO4, CHO2, and OPI3) that are known to regulate phospholipid metabolism; two genes (CKB1 and CKB2) encoding subunits of the casein kinase 2; and two genes (MRPS35 and RTC2) of unknown function. Biochemical and genetic analyses reveal that a common feature of these mutants is an increase in the level of cellular phosphatidic acid (PA). Results from in vivo and in vitro analyses indicate that PA may facilitate the coalescence of contacting LDs, resulting in the formation of “supersized” LDs. In summary, our results provide important insights into how the size of LDs is determined and identify novel gene products that regulate phospholipid metabolism