Mineralisation of crop residues on the soil surface or incorporated in the soil under controlled conditions

In the present work, we compare the effect of mature crop residues mixed into a ferralitic soil or placed as a single layer on soil surface on the mineralisation of C and N over 55 days. As residues, we used dry stems of rice, soybean, sorghum, brachiaria and wheat. There were no significant effects of residue placement on C mineralisation kinetics. Decomposition of the residues on the soil surface slightly increased net N mineralisation for residues having the smallest C/N ratio.     

Correlation between mite community structure and gross N fluxes

Net nitrogen (N) mineralisation rate is the result of two independent processes: gross N mineralisation and N immobilisation. Techniques for determining these rates have only been developed recently and no studies have examined the relationship between soil fauna and these two components of net N mineralisation. We present data which demonstrates that mite community structure, described using the Shannon index, is correlated with gross N immobilisation rates in the Western Australian wheat belt. These results suggest that examining the impacts of mites on gross N fluxes is warranted.     

Using functional traits to assess the role of hedgerow corridors as environmental filters for forest herbs

Linear habitats such as hedgerows can constitute important refuges for native flora and fauna, possibly providing connectivity between landscape elements. The effectiveness of these functions, however, depends on the ability of linear habitats to benefit a significant proportion of the local species pool and their functional attributes. This study aims to identify life-history traits that appear to either limit or facilitate survival or colonization of forest herbs in hedgerows. The distribution patterns of 47 native forest herbaceous species and their associated traits were compared in a system of hedgerows and attached forest patches of southern Quebec. Although 83% of the species surveyed in forest patches were present in hedgerows, significant differences in abundance suggest the existence of a selective pressure on forest species in linear habitats. Early spring flowering was negatively associated with hedgerows, possibly because of unfavourable microclimatic conditions. Seed dispersal phenology partly mirrors results for flowering phenology with early summer dispersal and late fall dispersal being less common in hedgerows than in forests. Slow dispersal mainly through myrmecochory was also less common in hedgerows compared to forest sites, suggesting a selective pressure on slow dispersers in linear habitats. The capacity for vegetative propagation was positively associated with hedgerows, possibly because it provides an alternative strategy to survive and expand when conditions are less favourable for sexual reproduction. Our approach highlights traits that can help determine the vulnerability of native forest species in linear habitats or their likelihood to benefit from the maintenance of wooded corridors in an inhospitable matrix.     

Interactions between bovine beta-lactoglobulin and peptides under different physicochemical conditions

The aim of this study was to determine if peptides could interact with beta-lactoglobulin (beta-LG) and what the physicochemical conditions promoting their interaction with the protein are. The binding of negatively charged (beta-LG 125-135 and 130-135), positively charged (beta-LG 69-83 and 146-149), and hydrophobic (alphaS1-CN 23-34 and beta-LG 102-105, both bioactive peptides) peptides to bovine beta-LG was determined using an ultrafiltration method under different physicochemical conditions: pH 3.0, 6.8, and 8.0; buffers of 0.05 and 0.1 M; 4, 25, and 40 degrees C; beta-LG/peptide ratios of 1:5 and 1:10. At pH 3.0, none of the peptides interacted with beta-LG at any temperature, buffer molarity, or beta-LG/peptide ratio probably due to electrostatic repulsions between the highly protonated species. At pH 6.8 and 8.0, charged peptides beta-LG 130-135, 69-83, and 146-149 bound to beta-LG under some physicochemical conditions, possibly by nonspecific binding. However, both hydrophobic peptides probably bind to the inner cavity (beta-barrel) of beta-LG, provoking the release of materials absorbing at 214 nm. Given the known biological activities of the hydrophobic peptides used in this study (opioid and ACE-inhibitory activities), their binding to beta-LG may be relevant to a better understanding of the physiological function of the protein.     

Copper binding capacity of root exudates of cultivated plants and associated weeds

Cu binding to root exudates of two cultivated plants, wheat (Triticum aestivum) and rape (Brassica napus), and two weeds associated with wheat, dog daisy (Matricaria inodora) and cornflower (Centaurea cyanus), was studied in vitro under hydroponic and sterile conditions. Nutrient solutions were prepared with or without P. A MetPLATE microbiological test was used to assess the metal complexing capacity of root exudates. In the P-deficient solutions, no exudation was observed for any of the four plants; consequently, no Cu binding occurred. When P was present in the nutrient solutions, the plant exudates displayed differing abilities to complex Cu. No difference was detected in the binding capacity of the dog daisy or cornflower, and the blank [heavy metal binding capacity (HMBC)=1.07, 1.40 and 1.00, respectively]; however, the rape and wheat exudates were found to complex Cu in rhizospheric solutions (HMBC=1.73 and 3.00, respectively). The concentrations of exuded organic C were 1.2, 10.8, 15.3 and 15.7 mg l^-1 for the dog daisy, cornflower, wheat and rape, respectively. These results suggest that the nature, as well as the amount, of the organic compounds exuded by plant root, is important in determining the extent of Cu complexation.     

Scavenging of free radicals, antimicrobial, and cytotoxic activities of the Maillard reaction products of beta-lactoglobulin glycated with several sugars

The Maillard reaction occurs during many industrial and domestic thermal treatments of foods. It is widely used because of its role in creating colors, flavors, textures, and other functional properties in foodstuffs. Proteins glycated without the use of conventional chemical reagents have improved technofunctional properties such as heat stability, emulsifying, and foaming properties. The present study was carried out to determine the extent to which this reaction can convey antioxidant, antimicrobial, or cytotoxic activities to beta-lactoglobulin (BLG) and to its tryptic and peptic hydrolysates. BLG was modified with six different sugars in solution at 60 degrees C. Antiradical properties were estimated using a radical scavenging activity test. Antimicrobial activities against different bacterial strains were studied with a diffusion disk method. Cytotoxic tests were performed using two cell lines and the 3-(4,5-dimethylthiazoyl-2-yl)-2,5-diphenyltetrazolium bromide (MTT) rapid colorimetric assay. Glycation induced a radical scavenging activity to BLG, the intensity of which depended on the sugar used for modification. Proteins modified with ribose and arabinose showed the highest radical scavenging activities depicted by about 80 and 60% of 2,2-diphenyl-1-picrylhydrazyl (DPPH) absorption decrease at 515 nm. No antimicrobial effect of any glycated form of BLG against Escherichia coli, Bacillus subtilis, Listeria innocua, and Streptococcus mutans was observed. The MTT test showed no enhancement of cytotoxicity by modified proteins and peptides against COS-7 and HL-60 cells. Thus, glycated proteins could be used in formulated food as functional ingredients with a radical scavenging activity able to delay deterioration due to oxidation. This use could be even more advisable considering the lack of toxicity to eukaryotic and prokaryotic cell cultures demonstrated in this work.     

Isolation and structure elucidation of a new thermal breakdown product of glucobrassicin,the parent indole glucosinolate

The thermal breakdown of glucobrassicin, the major natural indole glucosinolate present in cruciferous vegetables, has been studied. This study has been conducted using pure synthetic glucobrassicin instead of raw vegetable material to eliminate possible other sources (i.e., enzymatic or chemical) of degradation. After 1 h in aqueous solution at 100 degrees C, 10% of the original glucobrassicin is degraded and yields a unique degradation compound. This compound is described for the first time and has been identified as 2-(3'-indolylmethyl)glucobrassicin on the basis of data obtained by (1)H nuclear magnetic resonance spectroscopy as well as tandem mass spectrometric experiments carried out from positive and negative electrospray produced ions.     

Partitioning the spatial and environmental variation of Sclerotinia stem rot on soybean

The variance in survival of Sclerotinia sclerotiorum's sclerotia, carpogenic germination (apothecia) as well as Sclerotinia stem rot (SSR) severity (Disease Severity Index (DSI)) on soybean was partitioned among canopy, soil physico-chemistry and microbiology, cultural practices (2 or 3-y-corn rotation/soybean monoculture and mineral fertilization/urban compost), and spatial matrices in two soils. Partial multiple regression was used to partition the individual SSR variables variance while partial canonical redundancy analysis partitioned the DSI-apothecia and apothecia-survival variance. In clay loam, the sclerotial survival and apothecia variance were mainly explained by the spatial structure of soil physico-chemistry while the DSI did not share this spatial structure and was largely explained by the effects of 3-y-corn rotation on canopy and soil, i.e. lower weed biomass, enhanced soybean yield and fewer apothecia were correlated with disease suppressiveness. In sandy loam, the DSI variance was mostly explained by the spatial structure of canopy and physico-chemistry. Disease suppressiveness, by the interaction of 3-y-corn rotation with urban compost, was largely explained by the enhancement of soil properties, i.e. higher aggregate stability, microbial activity and soil solution concentration in exchangeable ions correlated negatively with carpogenic germination. Partitioning the SSR variance among four matrices of spatial and environmental factors allowed for the first time to interpret and quantify the variance of disease development explained by cultural practices in interaction with the main characteristics of this agroecosystem.     

Kinetic study of the acid hydrolysis of various oligofructose samples

The kinetic of acid hydrolysis of five commercially available oligofructose samples used as food ingredients has been investigated as a function of the dry matter concentration, reaction pH, and temperature. The initial fructose release rate is found to be roughly proportional to the inverse of the average polymerization degree in number. A pseudo first order kinetic is found with respect to the fructosyl chain end concentration and to the proton concentration. Arrhenius plot is found to reasonably fit the data in a relatively wide temperature range (7-130 degrees C). The results allow the estimation of the fructose release rate in many foodstuff processing conditions.     

Long-term treatment with standardized Ginkgo biloba extract (EGb 761) attenuates cognitive deficits and hippocampal neuron loss in a gerbil model of vascular dementia

The standardized extract of Ginkgo biloba EGb 761 has been used to reduce cognitive dysfunction. The present study was designed to evaluate the effect of postischemic oral treatment with EGb 761 in a model of vascular dementia in gerbils. Daily oral posttreatment with EGb 761 led to a significant recovery of spatial memory assessed by the object location test, inhibited the decrease in plasma SOD activity and protected the hippocampal CA1 neurons, even when administered after the insult. These data provide further evidence for the therapeutic potential of EGb 761 in the treatment of vascular dementia.