Samples of flax (Linum usitatissimum) stems from the cultivars 'Natasja' and 'Ariane' were separated into fibre and core fractions and analysed by gasliquid chromatographic methods, 13C CPMAS NMR spectrometry, histochemistry, electron microscopy and UV absorption microspectrophotometry to assist in determining the structure and composition of these cell walls in relation to quality and utilisation. Analyses from chromatography and NMR gave similar results for carbohydrate and phenolic constituents in various samples and in the lower, more mature regions of the stem. Amounts of uronic acids and xylose were lower while amounts of mannose, galactose and glucose were higher in fibre vs core fractions. Quantities of phenolic constituents were significantly higher in the core than the fibre, with groups representative of both guaiacyl and syringyl lignins; amounts of phenolic acids were low. NMR showed a low intensity signal for aromatics in fibre, and it is possible that such signals arise from compounds in the cuticle rather than the fibre. Microscopic studies indicated that aromatic constituents were present in core cell walls, cuticle of the epidermis, and cell corners and middle lamellae of some regions within the fibre tissues. The lignin in fibre appeared to be of the guaiacyl type and may be too low in concentration to be unambiguously detected by NMR. Aromatic compounds were not observed in the epidermis or parenchyma cell walls. Similar analyses of dewretted (unscutched) samples indicated that core tissues were mostly unchanged from unretted samples. Retted fibre tissues still contained lignified cell corners and middle lamellae in some regions. The cuticle, which was associated with retted fibres, was not degraded by dew-retting fungi. Fungi removed interfibre materials in some places and at times degraded the secondary wall near the cell lumen of fibre cells. Results indicate that microspectrophotometry and histochemistry are useful to identify the location and type of aromatics in fibre cell walls.Key words: bast, Linum usitatissimum, lignin, carbohydrate, NMR, gas-liquid chromatography, histochemistry, microscopy, microspectrophotometry.
Adding chelating agents, i.e., oxalic acid and ethylenediamine-tetra-acetic acid (edta), substantially increases the retting effect on flax by the commercial enzyme products Ultrazym and Flaxzyme (Novo Nordisk), as shown by scanning electron microscopy, release of reducing sugars, and the Fried test. Degradation of pectin-rich citrus peel by these enzymes also increases with the addition of oxalic acid and edta, while citric acid has a low or insignificant effect. Oxalic acid at 50 mmol concentration reduces the amount of Flaxzyme required to effectively ret flax stems, according to the Fried test, by a factor of about 50. Retting with Flaxzyme and 50 mmol oxalic acid is completed in approximately half the time at 45°C, compared with that at 22°C. A mechanical pretreatment that crushes flax stems by pulling them over a surface at a 90° angle opens the flax structure and further increases the efficiency of enzymatic retting. These procedures appear to modify both the chemical and structural features of flax, and they reduce the time as well as the amount of enzyme required to ret flax, therefore improving technical efficiency and economic attractiveness at the commercial level.
Seven strains of filamentous fungi and one yeast were isolated from flax that was dew retted in the United States. These filamentous fungi were subcultured to purity and identified, and six appear not to have been reported earlier as isolates from dew-retted flax. Five of the purified U.S. strains, two fungi isolated from flax that was dew retted in Europe, and a laboratory culture of Aspergillus sojae were tested for their ability to ret flax stems. The monocultures were evaluated for the degree of retting, fiber strength, dry weight loss, and tactile response (i.e., feel of softness) as reflected in the retted fiber. Structural modifications of representative samples of the retted flax were assessed by scanning electron microscopy. All of the filamentous fungi were able to carry out some retting, whereas the isolated yeast could not. All organisms produced pectinases when they were cultivated in shake flasks on ball-milled flax as the sole carbon source. Some fungi also produced cellulases, mannanases, and xylanases. Rhizomucor pusillus and Fusarium lateritium were noteworthy as retting organisms by their high level of pectinase activity, ability to attack noncellulosic cell types without attacking cellulose, capacity to penetrate the cuticular surface of the stem, and efficient fiber release from the core. The results indicated that these organisms deserve further study as potential organisms for retting of bast fibers in industrial applications.
Hen housing for commercial egg production continues to be a societal and regulatory concern. Controlled studies have examined various aspects of egg safety, but a comprehensive assessment of commercial hen housing systems in the US has not been conducted. The current study is part of a holistic, multidisciplinary comparison of the diverse aspects of commercial conventional cage, enriched colony cage, and cage-free aviary housing systems and focuses on environmental and egg microbiology. Environmental swabs and eggshell pools were collected from all housing systems during 4 production periods. Total aerobes and coliforms were enumerated, and the prevalence of Salmonella and Campylobacter spp. was determined. Environmental aerobic and coliform counts were highest for aviary drag swabs (7.5 and 4.0 log cfu/mL, respectively) and enriched colony cage scratch pad swabs (6.8 and 3.8 log cfu/mL, respectively). Aviary floor and system wire shell pools had the greatest levels of aerobic contamination for all eggshell pools (4.9 and 4.1 log cfu/mL, respectively). Hens from all housing systems were shedding Salmonella spp. (89–100% of manure belt scraper blade swabs). The dry belt litter removal processes for all housing systems appear to affect Campylobacter spp. detection (0–41% of manure belt scraper blade swabs) considering detection of Campylobacter spp. was much higher for other environmental samples. Aviary forage area drag swabs were 100% contaminated with Campylobacter spp., whereas enriched colony cage scratch pads had a 93% positive rate. There were no differences in pathogen detection in the shell pools from the 3 housing systems. Results indicate egg safety is enhanced when hens in alternative housing systems use nest boxes. Additionally, current outcomes indicate the use of scratch pads in hen housing systems needs to be more thoroughly investigated for effects on hen health and egg safety.
(pH 7.2) at 4°C for 1.5 h. Tissue was washed twice in buffer for 1.5 h at 40C prior to post-fixation in 2% OS04 in the same buffer at room temperature for 1 h. An overnight wash in buffer followed by a 20-min wash preceded dehydration in a graded series of ethanol. The series consisted of 50, 60, 70, 80, 90, and 95% ethanol for I h, each, followed by 100%o for I d. Propylene oxide was used as a transitional solvent for 4 h followed by infiltration in a graded series of Polaron Ultra Low Viscocity embedding media. The
The Laxa group of the Panicum genus contains species which have CO2 exchange and anatomical characteristics intermediate to C3 and C4 photosynthetic types (C3/C4), and also species characterized as C3. Hybrids were made between two of the C3/C4 species and two C3 species. Carbon dioxide exchange and morphological, leaf anatomicaL and cytogenetic characteristics of F, hybrids between Panicum milioides Nees. ex Trin (C3/C4) and P. laxum Mez. (C3), P. spathellosum Doell (C3/C4) and P. boliviense Hack. (C3), and P. spathellosum and P. laxum were studied. There were no consistent differences in apparent photosynthesis, although two of the three hybrids had higher net CO2 uptake than the C3 parent. Values of inhibition of apparent photosynthesis by 21% 02, CO2 loss in the light, and CO2 compensation concentration for the hybrids were between those of the parents. All three hybrids showed leaf anatomical traits, especially organelle quantities in the bundle sheath cells, between those of their respective parents. Linear regression of CO2 compensation concentration on the percentage of mitochondria and chloroplasts in vascular bundle sheaths of the parents and hybrids pve correlation coefficients of -0.94. This suggests that the reduction in CO2 loss in the C3/C4 species, and to a lesser degree in the F, hybrids, was due to development of organelles and perhaps a higher proportion of leaf photorespiration in bundle sheaths. The overall morphology of the hybrids was so different from the parents that they could be described as new taxonomic forms. The chromosomes in the hybrids were mainly unpaired or paired as bivalents indicating possible homology between some parental genomes.Closely related Panicum species have been found to possess characteristics of C3, C4, and C3/C4 intermediate photosynthetic types based on CO2 exchange (2,3,5,6,13,14) and leafanatomy (4, 13). These species have been assigned to the informal taxonomic group Laxa or the closely related Grandia group (7,11,12 MATERIALS AND METHODSHybridization. An interspecific hybrid was produced by using Panicum milioides, accession 101, as the female parent and Panicum laxum, accession 127 (formerly reported as Panicum hylaeicum Mez [1]), as the pollen parent. To achieve this hybridization, potted plants ofboth accessions possessing inflorescences were taken into the laboratory. All florets, with the exception of 20 in preanthesis, were removed from the inflorescences of the female parent. The remaining florets were emasculated under a dissecting microscope by opening the florets and removing the anthers. Pots were returned to the greenhouse where the emasculated inflorescences were placed together with an inflorescence of the pollen parent and covered with a bag made of 2.5 cm diameter dialysis tubing. Seed were harvested from the female parent approximately 2 weeks later and then germinated in Petri plates on blotter paper. Seedlings were transplanted to small plastic pots and grown in the greenhouse for 2 months. The hybrid was identified among the g...
Anaerobic fungi in ruminal fluid from cows eating Bermuda grass hay plus a grain and minerals supplement were evaluated for diversity in sporangial morphotypes and colony growth patterns and for the degradation of various lignocelluloses. In selective cultures containing streptomycin and penicillin, an active population of ruminal fungi colonized leaf blades and degraded fiber at rates and extents almost equal to that of the total ruminal population. Three major sporangial morphotypes were consistently observed on leaf blades: oval, globose, and fusiform. Fungal colonies representing three distinct growth types consistently developed in anaerobic roll tubes inoculated with strained ruminal fluid. Sporangial morphotypes could not be matched to colony types due to multiple sporangial forms within a colony. Under identical growth conditions, one type exhibited a monocentric growth pattern, while two types exhibited polycentric growth patterns previously unreported in ruminal fungi. Mixed ruminal fungi in selective cultures or in digesta taken directly from the rumen produced a massive clearing of the sclerenchyma. Quantitation of tissue areas in cross sections by light microscopic techniques showed that fungal incubations resulted in significant (P = 0.05) increases in sclerenchyma degradation compared to whole ruminal fluid incubations. The mestome cell wall was at times penetrated and partially degraded by fungi; the colonization was less frequent and to a lesser degree than with the sclerenchyma. Conversely, ruminal bacteria were not observed to degrade the mestome sheath. Phenolic monomers at 1 mM concentrations did not stimulate to a significant (P = 0.05) extent the dry weight loss or fungal colonization of leaf blades; at 10 mM concentrations cinnamic and benzoic acids were toxic to ruminal fungi.
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