Showing papers by "Agriculture and Agri-Food Canada published in 2000"
TL;DR: The antioxidant activity of many phenolic compounds and extracts was comparable to those of synthetic antioxidants using the beta-carotene bleaching and HPLC methods.
Abstract: Methods for determining primary antioxidant activity were evaluated. A beta-carotene bleaching method and a free radical method using 2, 2-diphenyl-1-picrylhydrazyl (DPPH(*)) were modified to rapidly test samples for potential antioxidant activity. Malonaldehyde production in a linoleic acid emulsion system assayed by an HPLC method was also used to determine antioxidant and prooxidant activities initiated by a metal catalyst (Cu(2+)). All methods were used to assess activity of selected phenolic compounds including several anthocyanidins/anthocyanins and selected berry extracts. Most phenolic compounds had prooxidant activity at low concentrations, unlike synthetic antioxidants (BHA and BHT). Compounds with similar structures exhibited comparable trends in antioxidant activity. Antioxidant activity usually increased with an increase in the number of hydroxyl groups and a decrease in glycosylation. The antioxidant activity of many phenolic compounds and extracts was comparable to those of synthetic antioxidants using the beta-carotene bleaching and HPLC methods.
1,453 citations
TL;DR: Determination of the degree of lycopene isomerization during processing would provide a measure of the potential health benefits of tomato-based foods, and further research on the bioavalability, pharmacology, biochemistry, and physiology must be done to reveal the mechanism of lyCopene in human diet.
Abstract: Lycopene is the pigment principally responsible for the characteristic deep-red color of ripe tomato fruits and tomato products. It has attracted attention due to its biological and physicochemical properties, especially related to its effects as a natural antioxidant. Although it has no provitamin A activity, lycopene does exhibit a physical quenching rate constant with singlet oxygen almost twice as high as that of beta-carotene. This makes its presence in the diet of considerable interest. Increasing clinical evidence supports the role of lycopene as a micronutrient with important health benefits, because it appears to provide protection against a broad range of epithelial cancers. Tomatoes and related tomato products are the major source of lycopene compounds, and are also considered an important source of carotenoids in the human diet. Undesirable degradation of lycopene not only affects the sensory quality of the final products, but also the health benefit of tomato-based foods for the human body. Lycopene in fresh tomato fruits occurs essentially in the all-trans configuration. The main causes of tomato lycopene degradation during processing are isomerization and oxidation. Isomerization converts all-trans isomers to cis-isomers due to additional energy input and results in an unstable, energy-rich station. Determination of the degree of lycopene isomerization during processing would provide a measure of the potential health benefits of tomato-based foods. Thermal processing (bleaching, retorting, and freezing processes) generally cause some loss of lycopene in tomato-based foods. Heat induces isomerization of the all-trans to cis forms. The cis-isomers increase with temperature and processing time. In general, dehydrated and powdered tomatoes have poor lycopene stability unless carefully processed and promptly placed in a hermetically sealed and inert atmosphere for storage. A significant increase in the cis-isomers with a simultaneous decrease in the all-trans isomers can be observed in the dehydrated tomato samples using the different dehydration methods. Frozen foods and heat-sterilized foods exhibit excellent lycopene stability throughout their normal temperature storage shelf life. Lycopene bioavailability (absorption) can be influenced by many factors. The bioavailability of cis-isomers in food is higher than that of all-trans isomers. Lycopene bioavailability in processed tomato products is higher than in unprocessed fresh tomatoes. The composition and structure of the food also have an impact on the bioavailability of lycopene and may affect the release of lycopene from the tomato tissue matrix. Food processing may improve lycopene bioavailability by breaking down cell walls, which weakens the bonding forces between lycopene and tissue matrix, thus making lycopene more accessible and enhancing the cis-isomerization. More information on lycopene bioavailability, however, is needed. The pharmacokinetic properties of lycopene remain particularly poorly understood. Further research on the bioavalability, pharmacology, biochemistry, and physiology must be done to reveal the mechanism of lycopene in human diet, and the in vivo metabolism of lycopene. Consumer demand for healthy food products provides an opportunity to develop lycopene-rich food as new functional foods, as well as food-grade and pharmaceutical-grade lycopene as new nutraceutical products. An industrial scale, environmentally friendly lycopene extraction and purification procedure with minimal loss of bioactivities is highly desirable for the foods, feed, cosmetic, and pharmaceutical industries. High-quality lycopene products that meet food safety regulations will offer potential benefits to the food industry.
948 citations
TL;DR: Bacterial endophytes have been implicated in supplying biologically fixed nitrogen in non-legumes, and these associations can increase the nitrogen economy of a crop, reducing the requirement for N fertilizers.
Abstract: Most healthy naturally propagated plants grown in field or potting soils are colonized by communities of endophytic bacteria, embracing a wide variety of species and genera. These bacteria form nonpathogenic relationships with their hosts: some beneficial, some neutral, and some detrimental. Such associations can increase plant growth and hasten development or improve resistance to environmental stress. Endophytic bacteria have been implicated in supplying biologically fixed nitrogen in non-legumes, and these associations can increase the nitrogen economy of a crop, reducing the requirement for N fertilizers. Bacterial endophytes have also been shown to prevent disease development through endophyte-mediated de novo synthesis of structural compounds and fungitoxic metabolites. Such induced protection responses have been linked to certain forms of systemic acquired (disease) resistance. Certain crop sequences have been shown to favor the build-up of specific plant growth-promoting bacterial endophyte popula...
757 citations
TL;DR: The problems, aspects and methods of liquid storage and freeze-thawing of boar semen are discussed and a review is given on examination of spermatozoa by the recent fluorescent staining methods.
718 citations
TL;DR: Evaluated antimicrobial films, designed to slowly release bacterial inhibitors, to improve the preservation of vacuum-packaged processed meats during refrigerated storage found strongest inhibition was observed on drier surfaces (bologna), onto which acid release was slower, and with films containing cinnamaldehyde, as a result of its greater antimicrobial activity under these conditions.
489 citations
TL;DR: In this article, the effect of fresh cattle manure on soil acidity and nutrient availability was determined in the laboratory for two acid soils from Beaverlodge and Fort Vermillion in the Peace River region of Alberta, Canada.
Abstract: Crop production on acid soils can be improved greatly by adjusting the pH to near neutrality. While soil acidity is commonly corrected by liming, there is evidence that animal manure amendments can increase the pH of acid soils. The effect of fresh cattle manure on soil acidity and nutrient availability was determined in the laboratory for two acid soils from Beaverlodge and Fort Vermillion in the Peace River region of Alberta, Canada. The effect of manure on soil pH was immediate and persisted during an 8-wk incubation. Manure-amended soil had significantly higher pH than unamended soil, and the highest rate (40 g manure kg -1 , dry weight basis) increased the pH of Beaverlodge and Fort Vermillion soils from 4.8 to 6.0 and 5.5 to 6.3, respectively. The higher pH in manure-amended than unamended soils was attributed to buffering from bicarbonates and organic acids in cattle manure. Mineral N (NH 4 -N + NO 3 -N), available P, K, Ca, and Mg increased immediately after manure application, and available P and K remained significantly higher in manure-amended than unamended soil after the 8-wk incubation. Soils amended with 40 g manure kg -1 had three to four times more plant-available P and K than unamended soils after incubation. Available S concentrations did not differ significantly in manure-amended and unamended soils. Extractable Al and Fe declined slightly after manure application, but did not differ in manure-amended or unamended soils after incubation. No change in the cation-exchange capacity (CEC) of manure-amended soils compared to unamended soils was observed in this study, and it appears that appreciable changes in Al, Fe, and CEC from manure application do not occur in the short-term (weeks). Our results indicate that, in the short-term, cattle manure amendments can increase the pH and the quantity of plant-available P and K in acid soils.
448 citations
TL;DR: The intensive research about the effects of tea on health provide a good starting point and are summarized to get a better understanding of the complex mechanisms that could be implicated in the physiological activity of both beverages.
404 citations
TL;DR: In this article, the authors calculate phenotypic relationships between energy balance in early lactation and health and reproduction in that lactation, using data from 140 multiparous Holstein cows.
345 citations
TL;DR: A robust new approach for describing and segmenting landforms which is directly applicable to precision farming has been developed in Alberta using derivatives computed from DEMs and a fuzzy rule base to identify up to 15 morphologically defined landform facets.
312 citations
TL;DR: Of all the insects tested, Cryptolestes ferrugineus was the most sensitive to DE, and Rhyzopertha dominica and T. castaneum were the most tolerant species tested.
308 citations
TL;DR: This review emphasizes Canadian contributions, but incorporates studies from North America to put that research into perspective, and concludes that resistant cultivars will ensure stable yields and high-quality grain free of mycotoxins.
Abstract: The recent increase in prevalence and severity of fusarium head blight (FHB), in cereals in Canada and elsewhere, has caused hardship and economic loss to producers and the grain industry. This review emphasizes Canadian contributions, but incorporates studies from North America to put that research into perspective. Since the reviews of Sutton in 1982 and Miller in 1994, significant advances in our understanding of the epidemiology of the disease have occurred that are fundamental to the development of appropriate management strategies. Also, we now better understand the genetics of resistance in wheat and there is a consensus that resistant cultivars will provide the most stable and durable solution to the problem of FHB. Our knowledge of the genetic basis of resistance in wheat, and the development of molecular markers to facilitate early generation selection for resistance to FHB, are essential tools to this end. Resistant cultivars will ensure stable yields and high-quality grain free of mycotoxins.
TL;DR: The Raspberry seed oil was rich in tocopherols with the following composition (mg/100 g): α-tocopherol 71; γ-tocherol 272; δ-tochemol 17.4; and total vitamin E equivalent of 97.7%.
TL;DR: The diffusion of acetic or propionic acids from thin chitosan-based antimicrobial packagingfilms in which they were incorporated was measured after immersion of the films in water, and the effects of pH (5.7, 6.4, or 7.0) and temperature (4 °C, 10 °C or 24 °C) on diffusion were investigated as discussed by the authors.
Abstract: The diffusion of acetic or propionic acids from thin (44 to 54 m m) chitosan-based antimicrobial packagingfilms in which they were incorporated was measured after immersion of the films in water, and the effects of pH (5.7,6.4, or 7.0) and temperature (4 °C, 10 °C, or 24 °C) on diffusion were investigated. The kinetics of acetic- and propi-onic-acid release deviated from the Fickian model of diffusion. Diffusion was found to be unaffected by pH in therange of values tested, but a decrease in temperature from 24 °C to 4 °C resulted in a reduction of diffusion coefficientsfrom 2.59 × 10 -12 m 2 .s -1 to 1.19 × 10 -12 m .s for acetic acid and from 1.87 × 10 m 2 .s -1 to 0.91 × 10 -12 m 2 .s -1 for propionicacid. The effect of temperature on diffusion was well (r 2 . 0.9785) described by an Arrhenius-type model with activa-tion energies of 27.19 J.mole -1 (acetic) and 24.27 J.mole (propionic). Incorporation of lauric acid or essential oils(cinnamaldehyde or eugenol) into the chitosan film at the time of preparation produced a subsequent reduction in thediffusion of acetic or propionic acid, and maximum effects were obtained with lauric acid and cinnamaldehydeincorporated to final concentrations of 1.0% and 0.5% (w/w), respectively.Key Words: diffusion, acetic, propionic, chitosan, packaging
TL;DR: Data from clinical studies established that there was an inverse linear relationship between measures of postprandial blood glucose and insulin responses to an oral glucose load, consumed in a drink, and the logarithm of viscosity of the drink are re-analysed using concentration and molecular weight as the dependent variables.
Abstract: Data from clinical studies established that there was an inverse linear relationship between measures of postprandial blood glucose and insulin responses to an oral glucose load, consumed in a drink, and the logarithm of viscosity of the drink. These data have been re-analysed using concentration and molecular weight as the dependent variables. Molecular weight (M) of the beta-glucans used was determined using high-performance size exclusion chromatography equipped with a triple detector system of right angle light scattering, viscometry and refractive index. A significant relationship between changes in peak blood glucose and a combination of logarithm of the concentration and logarithm of M was found.
TL;DR: The first successful assignment of 15 microsatellite or simple sequence repeat (SSR) markers to the Phaseolus vulgaris molecular linkage map is reported, indicating a widespread distribution throughout the bean genome.
Abstract: Microsatellite or simple sequence repeat (SSR) markers have been successfully used for genomic mapping, DNA fingerprinting, and marker-assisted selection in many plant species. Here we report the first successful assignment of 15 SSR markers to the Phaseolus vulgaris molecular linkage map. A total of 37 SSR primer pairs were developed and tested for amplification and product-length polymorphism with BAT93 and Jalo EEP558, the parental lines of an F7 recombinant inbred (RI) population previously used for the construction of a common bean molecular linkage map. Sixteen of the SSRs polymorphic to the parental lines were analyzed for segregation and 15 of them were assigned to seven different linkage groups, indicating a widespread distribution throughout the bean genome. Map positions for genes coding for DNAJ-like protein, pathogenesis-related protein 3, plastid-located glutamine synthetase, endochitinase, sn-glycerol-3 phosphate acyltransferase, NADP-dependent malic enzyme, and protein kinase were determined for the first time. Addition of three SSR loci to linkage group B4 brought two separated smaller linkage groups together to form a larger linkage group. Analysis of allele segregation in the F7 RI population revealed that all 16 SSRs segregated in the expected 1:1 ratio. These SSR markers were stable and easy to assay by polymerase chain reaction (PCR). They should be useful markers for genetic mapping, genotype identification, and marker-assisted selection of common beans.
TL;DR: The application of ELISA and monoclonal antibody technologies in plant pathology has greatly improved the ability to detect plant pathogens and is increasing the understanding of, their ecology and epidemiology.
Abstract: Detection and diagnosis of plant viruses has included serological laboratory tests since the 1960s. Relatively little work was done on serological detection of plant pathogenic bacteria and fungi prior to the development of ELISA and monoclonal antibody technologies. Most applications for laboratory-based tests were directed at virus detection with relatively little emphasis on fungal and bacterial pathogens, though there was some good work done with other groups of plant pathogens. With the advent of molecular biology and the ability to compare regions of genomic DNA representing conserved sequences, the development of laboratory tests increased at an amazing rate for all groups of plant pathogens. Comparison of ITS regions of bacteria, fungi, and nematodes has proven useful for taxonomic purposes. Sequencing of conserved genes has been used to develop PCR-based detection with varying levels of specificity for viruses, fungi, and bacteria. Combinations of ELISA and PCR technologies are used to improve sensitivity of detection and to avoid problems with inhibitors or PCR often found in plants. The application of these technologies in plant pathology has greatly improved our ability to detect plant pathogens and is increasing our understanding of, their ecology and epidemiology.
TL;DR: In this article, positive-head tension infiltrometer (TI) and single-ring pressure infiltron (PI) were compared on single-grain sand, structured loam, and cracking-clay loam soils under conventional tillage (CT), no-tillage (NT), and native woodlot (WL) managements.
Abstract: Saturated hydraulic conductivity (K SAT ) is an important soil property that is difficult to measure. Positive-head tension infiltrometer (TI) and single-ring pressure infiltrometer (PI) techniques show promise for measuring K SAT , but there have been few field tests or comparisons with other methods. The TI, PI, and classical undisturbed soil core (SC) methods for measuring K SAT were compared on single-grain sand, structured loam, and cracking-clay loam soils under conventional tillage (CT), no-tillage (NT), and native woodlot (WL) managements. Of the 27 between-method correlations (3 methods x 3 soils x 3 managements), only four were significant (P < 0.05). The TI method yielded lower K SAT values under high-permeability conditions (K SAT ≥ 10 -4 ms -1 ) relative to the other methods, as evidenced by lower geometric mean K SA (K GM ), lower maximum K SAT (K MAX ), and lower minimum K SAT (K MIN ) values. The 0.10-m diam. by 0.10-m-long SC method cores may have been too small to yield representative estimates of K SAT in the cracking-clay loam and in the NT and WL managements of the sand and loam, as indicated by high coefficients of variation (CVs), inconsistent K GM values, or high K MAX values relative to the other methods. Erratic K MAX and K MIN values, along with high CVs, suggest that the 0.10-m-diam. PI ring may have been too small to adequately sample the cracking clay loam soil under CT and NT management. Further work appears warranted for developing K SAT measurement methods, interpreting K SAT results, and determining appropriate K SAT methods for various soil types and conditions.
TL;DR: In this article, the authors examined the antioxidant capacity of extracted blueberries and found that blueberry extracts obtained at 60 °C had higher recovery of anthocyanins and antioxidant capacity.
Abstract:
Temperature, pH, and oxygenation of extracted blueberries were examined to determine how processing may affect the antioxidant capacity of blueberry food products. Extraction of fruit at 60 °C resulted in higher recovery of anthocyanins and antioxidant capacity, compared to extracts obtained at 25 °C. Subsequent room temperature storage resulted in losses in anthocyanins and antioxidant capacity only in those extracts obtained at 60 °C. Antioxidant capacity was greatest in pH 1 extracts, compared to extracts at pH 4 and 7. Oxygenation was detrimental to both anthocyanins and antioxidant capacity. Antioxidant capacity of processed products was positively correlated with anthocyanin (R = 0.92) and phenolic content (R = 0.95), and negatively correlated with % polymeric color (R = -0.64). In general, products that had experienced less processing had a higher antioxidant capacity. Simple colorimetric tests for anthocyanins and phenolics proved to be useful indicators of antioxidant capacity in processed products.
TL;DR: The results suggest that plants of the genus Ocimum can be used as an alternative to synthetic insecticides.
TL;DR: This review summarizes and recommends appropriate seed sampling techniques, protocols for screening weeds for resistance to herbicides of different sites of action, interpretation of results, and information given to the grower.
Abstract: : Diagnosing herbicide-resistant weeds as a first step in resistance management and monitoring their nature, distribution, and abundance demands efficient and effective screening tests. This review summarizes and recommends appropriate seed sampling techniques, protocols for screening weeds for resistance to herbicides of different sites of action, interpretation of results, and information given to the grower. Elements common to all screening procedures are reviewed. Choosing appropriate discriminating doses to distinguish between resistant and susceptible weed biotypes is the most important factor in achieving accurate and consistent results. Interpretation of results is also critical because resistant weeds may comprise a small portion of the population in suspected accessions or biotypes. Additional index words: Bioassay, discriminating dose, seed sampling, site of action, surveys. Abbreviations: ACCase, acetyl-CoA carboxylase (EC 6.4.1.2); ALS, acetolactate synthase (EC 4.1.3.18); AOPP, arylo...
TL;DR: In this paper, microwave assisted extraction (MAE) and high performance liquid chromatographic (HPLC) procedure was applied to measure ergosterol in soil samples, and the E-to-FB conversion factors were determined in six species of fungi grown in vitro.
Abstract: Determination of fungal biomass (FB) and FB-carbon (FB-C) from soil ergosterol concentration is diAcult because of unknown ergosterol-to-fungal biomass (E-to-FB) conversion factors and ineAcient ergosterol extraction methods. We applied a microwave-assisted extraction (MAE) and high performance liquid chromatographic (HPLC) procedure to measure ergosterol in soil samples. The E-to-FB conversion factors were determined in six species of fungi grown in vitro. The MAE method was fast and extracted up to nine times more soil ergosterol than a classical refluxing saponification method. Soil ergosterol was separated and quantified rapidly (<10 min) by HPLC. Alternaria alternata, Chaetomium globosum, Fusarium oxysporum, Penicillum chrysogenum, Rhizopus stolonifer and Trichoderma harzianum isolated from soil and plant matrices were grown in batch. Ergosterol and biomass content were determined in mycelia harvested during the stationary and exponential phases of growth. Total mycelial ergosterol ranged from 180 to 2178 mg, and total dry biomass ranged from 17 to 595 mg. Total ergosterol and fungal dry biomass were strongly associated (r 2 = 0.95). The C content in mycelial mats averaged 43% (21.1, SD), and was similar among fungal species and growth phases. The analyses of variance showed that the E-to-FB ratio was similar among fungal species or growth phase. An average ergosterol concentration of 4 m gm g ˇ1 dry biomass was determined for the six species of fungi, which gave a conversion factor of 250 mg dry biomass mg ˇ1 ergosterol. The MAE method recovered an average of 62% (211%, SD) of the ergosterol added in mycelial mats to soils prior to extraction, and its recovery was independent of soil properties. The E-to-FB ratio and percent recovery of mycelial ergosterol helped establish for the first time relationships determining soil FB and FB-C from soil ergosterol concentration. The amount of FB ranged from 155 to 4745 mg g ˇ1 and that for FB-C ranged from 67 to 2040 m gg ˇ1 for diAerent soils, and was higher in samples taken from native undisturbed land than in samples taken from adjacent cultivated fields. Measurement of soil ergosterol concentration is a useful estimate content of the living soil FB. 7 2000 Elsevier Science Ltd. All rights reserved.
TL;DR: An atrazine-metabolizing Nocardioides sp.
Abstract: Atrazine, a herbicide widely used in corn production, is a frequently detected groundwater contaminant. Nine gram-positive bacterial strains able to use this herbicide as a sole source of nitrogen were isolated from four farms in central Canada. The strains were divided into two groups based on repetitive extragenic palindromic (rep)-PCR genomic fingerprinting with ERIC and BOXA1R primers. Based on 16S ribosomal DNA sequence analysis, both groups were identified as Nocardioides sp. strains. None of the isolates mineralized [ring-U-14C]atrazine. There was no hybridization to genomic DNA from these strains using atzABC cloned from Pseudomonas sp. strain ADP or trzA cloned from Rhodococcus corallinus. S-Triazine degradation was studied in detail in Nocardioides sp. strain C190. Oxygen was not required for atrazine degradation by whole cells or cell extracts. Based on high-pressure liquid chromatography and mass spectrometric analyses of products formed from atrazine in incubations of whole cells with H218O, sequential hydrolytic reactions converted atrazine to hydroxyatrazine and then to the end product N-ethylammelide. Isopropylamine, the putative product of the second hydrolytic reaction, supported growth as the sole carbon and nitrogen source. The triazine hydrolase from strain C190 was isolated and purified and found to have a Km for atrazine of 25 μM and a Vmax of 31 μmol/min/mg of protein. The subunit molecular mass of the protein was 52 kDa. Atrazine hydrolysis was not inhibited by 500 μM EDTA but was inhibited by 100 μM Mg, Cu, Co, or Zn. Whole cells and purified triazine hydrolase converted a range of chlorine or methylthio-substituted herbicides to the corresponding hydroxy derivatives. In summary, an atrazine-metabolizing Nocardioides sp. widely distributed in agricultural soils degrades a range of s-triazine herbicides by means of a novel s-triazine hydrolase.
TL;DR: In this paper, the first isolation, purification and characterization of a wheat β-D-glucan was reported, and additional structural detail was revealed by hydrolysis with (1→3)(1→4)-β-D -glucans-4-oglucanohydrolase (lichenase, EC 3.2.1.8) and analysis of the oligosaccharide reaction products.
TL;DR: In this article, the effects of 19 consecutive years of pig (Sus scrofa) slurry (PS) application to a loamy soil (loamy, mixed, frigid Aeric Haplaquept) on N 2 O emissions were measured 36 times in 1 yr.
Abstract: Agricultural soils often receive annual applications of manure for long periods. Our objective was to quantify the effects of 19 consecutive years of pig (Sus scrofa) slurry (PS) application to a loamy soil (loamy, mixed, frigid Aeric Haplaquept) on N 2 O emissions. Soil surface N 2 O fluxes (F N2O ) were measured 36 times in 1 yr. Nitrous oxide concentration profiles, soil NH 4 + - and NO, -N contents, denitrifying enzyme activity (DEA), and denitrification rate (DR) in soil were also determined to explain the variation in F N2O . Long-term (19 yr) treatments on continuous silage maize (Zea mays L.) were 60 (PS60) and 120 Mg ha -1 yr -1 (PS120) of pig slurry and a control receiving mineral fertilizer at a dose of 150 kg ha -1 each of N, P 2 O 5 , and K 2 O. Denitrifying enzyme activity, soil N 2 O concentrations, and F N2O (< 25 ng m 2 s -1 ) were low in the control plots receiving mineral fertilizer. Annual applications of PS to the soil for 18 yr had positive residual effects on the DEA compared with the long-term fertilized control plots. Following PS application, there was a strong and rapid increase of F N2O (up to 350 ng m -2 s -1 ) on manured plots. The PS-induced F N2O increased with increasing quantity of PS, probably as the result of a greater availability of NO, -N for denitrification. The effects of PS on F N2O were mostly limited to the 30 d following application. with low fluxes (< 10 ng m -2 s -1 ) during the rest of the measurement period. Total N 2 O-N emissions represented 0.62, 1.23, and 1.65% of total N applied in control, PS60, and PS120 plots, respectively. These emission factors for the PS plots agreed with values previously suggested for N-fertilized soils (1.25%).
TL;DR: In this article, the authors measured fluxes of CO 2 in a tillage experiment that had been initiated in 1982 on a silt loam (Typic Haploboroll) in southwestern Saskatchewan.
Abstract: The traditional cropping system in semiarid regions of the Canadian prairies involves frequent summer fallowing with several tillage operations to control weeds during the fallow period. Recently, there has been a trend toward reduced tillage and more intensive cropping, but the impact of this shift in management on sequestration of atmospheric CO 2 remains uncertain. In 1995 and 1996, we measured fluxes of CO 2 in a tillage experiment that had been initiated in 1982 on a silt loam (Typic Haploboroll) in southwestern Saskatchewan. The experiment comprised two spring wheat (Triticum aestivum L.) rotations (continuous wheat [Cont. W] and fallow-wheat [F-W]), each with conventional tillage (CT) and no-till (NT) treatments. In Cont. W, CO 2 fluxes tended to be lower under NT than under CT (mean annual flux was 20 to 25% less for NT than CT). In F-W, tillage effects on mean annual CO 2 flux were significant (P < 0.05) in the wheat phase only (NT 10% less than CT). Tillage had negligible effect on C inputs in crop residues. lower CO 2 fluxes under NT than under CT were attributed to slower decomposition of crop residues placed on the surface of NT soil than when they were incorporated. With good growing conditions (and thus large inputs of residues) between 1989 and 1996, there was an accumulation of partially decomposed residues on the surface of NT soil. Carbon in surface residues represented about one-half of the C gained by NT soil. In Cont. W, surface residue C (in 1996) amounted to 3.6 t ha -1 under NT vs 1.4 t ha -1 under CT. Residue C amounts were smaller in the F-W system: 1.7 t ha -1 (NT) and 0.7 t ha -1 (CT). Based on our results, producers on medium-textured soils in the semiarid Canadian prairies who switch from the traditional wheat production system (conventionally tilled fallow-wheat) to continuous no-till cropping could, potentially, sequester 5 to 6 t C ha -1 in soil organic matter and surface residues in 13 to 14 yr.
TL;DR: Membrane technology for the processing of fruit juices and beverages has been applied mainly for clarification using ultrafiltration and microfiltration, and for concentration using reverse osmosis.
Abstract: Membrane technology for the processing of fruit juices and beverages has been applied mainly for clarification using ultrafiltration and microfiltration, and for concentration using reverse osmosis. The effects of product preparation, membrane selection, and operating parameters are important factors influencing filtration rate and product quality. Technological advances related to the development of new membranes, improvement in process engineering, and better understanding of fruit beverage constituents have expanded the range of membrane separation processes. Developments in novel membrane processes, including electrodialysis and pervaporation, increased the array of applications in combination with other technologies for alternate uses in fruit juices and beverages.
TL;DR: In this article, a simple linear model was used to explore the relationship among the soil organic constituents and evaluate the turnover of these carbon pools, and the results suggest that the quantity, as well as the turnover rate, of soil organic matter constituents that are in equilibrium influence the isotopic composition of such constituents.
Abstract: Understanding the dynamics of soil C is key to managing soil organic matter to enhance soil quality and ecosystem functioning, and reduce trace gas emissions from soils. Our objective was to determine the source and turnover of C pools in some agricultural soils in eastern Canada. Soils from five field experiments under continuous maize cropping for 4–37 yr were sampled, and the organic C content and stable C isotope (13C) composition of whole soil and water soluble and microbial biomass fractions determined. The 13C results showed a clear distinction between the water soluble organic C and microbial biomass C, with the water soluble organic C more like the whole soil and the microbial biomass more like the maize residues. A simple linear model was used to explore the relationship among the soil organic constituents and evaluate the turnover of these carbon pools. Even though the water soluble organic C had a higher turnover rate than the microbial biomass C, the proportion of C4-derived C in the biomass was about 2.5 times greater than that in water soluble organic C. Apparently the large amount of native soil C, the small amount of water soluble organic C, and its equilibrium with the native soil C, cause humus to dominate the isotopic composition of water soluble organic C even though the water soluble C is very active. Our results suggest that the quantity, as well as the turnover rate, of soil organic matter constituents that are in equilibrium influence the isotopic composition of such constituents.
TL;DR: This collection of cDNA libraries, ESTs, and accompanying annotation will provide a new resource for studies on oomycetes and on soybean responses to pathogen challenge.
Abstract: Phytophthora sojae (Kaufmann and Gerdemann) is an oomycete that causes stem and root rot on soybean (Glycine max L. Merr) plants. We have constructed three cDNA libraries using mRNA isolated from axenically grown mycelium and zoospores and from tissue isolated from plant hypocotyls 48 h after inoculation with zoospores. A total of 3,035 expressed sequence tags (ESTs) were generated from the three cDNA libraries, representing an estimated 2,189 cDNA transcripts. The ESTs were classified according to putative function based on similarity to known proteins, and were analyzed for redundancy within and among the three source libraries. Distinct expression patterns were observed for each library. By analysis of the percentage G+C content of the ESTs, we estimate that two-thirds of the ESTs from the infected plant library are derived from P. sojae cDNA transcripts. The ESTs originating from this study were also compared with a collection of Phytophthora infestans ESTs and with all other non-human ESTs to assess the similarity of the P. sojae sequences to existing EST data. This collection of cDNA libraries, ESTs, and accompanying annotation will provide a new resource for studies on oomycetes and on soybean responses to pathogen challenge.
TL;DR: In this article, a review of target site-based herbicide resistance is presented, with emphasis on the biochemical and molecular basis for resistance, and the mutation and its effect on protein steric and electronic properties.
TL;DR: Two putative HD2-like histone deacetylase cDNA clones are identified from Arabidopsis thaliana by screening the expressed sequence tag database, and Northern blot analysis indicated that AtHD2A was highly expressed in flowers and young siliques ofArabidopsis plants, whereas AtHD 2B was widely expressed in stems, leaves, flowers andYoung siliques.
Abstract: Post-translational modification of histones, in particular acetylation, is an important mechanism in the regulation of eukaryotic gene expression. Histone deacetylases are enzymes that remove acetyl groups from the core histones and play a key role in the repression of transcription. HD2 is a maize histone deacetylase, which shows no sequence homology to the histone deacetylases identified from other eukaryotes. We have identified two putative HD2-like histone deacetylase cDNA clones, AtHD2A and AtHD2B, from Arabidopsis thaliana by screening the expressed sequence tag database. AtHD2A and AtHD2B encode putative proteins of 246 and 305 amino acids, and share 44% and 46% amino acid identity to the maize HD2, respectively. Northern blot analysis indicated that AtHD2A was highly expressed in flowers and young siliques of Arabidopsis plants, whereas AtHD2B was widely expressed in stems, leaves, flowers and young siliques. AtHD2A repressed transcription when directed to a promoter containing GAL4-binding sites as a GAL4 fusion protein. Deletion of the extended acidic domain or the domain containing predicted catalytic residues of AtHD2A resulted in the loss of gene repression activity, revealing the importance of both domains to AtHD2A function. Arabidopsis plants were transformed with a gene construct comprising an AtHD2A cDNA in the antisense orientation driven by a strong constitutive promoter, -394tCUP. Silencing of AtHD2A expression resulted in aborted seed development in transgenic Arabidopsis plants, suggesting that the AtHD2A gene product was important in the reproductive development of Arabidopsis thaliana.