Genetic Variability of Rubisco in Tetraploid Wheats (Triticum turgidum)

Nineteen tetraploid wheats (Triticum turgidum), differing in their agronomical behaviour and geographic origins were grown in two experiments and analysed for the following physiological traits: soluble leaf protein content, rubisco content, initial and potential carboxylase activities of this enzyme as well as its relative content in percentage of protein, the specific activity of the enzyme and its activation state. The results show a high genetic variability for all studied traits and more particularly for the initial carboxylase activity. High phenotypic correlation was observed between the rubisco content and its potential activities, in the first experiment. Correlation between souble leaf protein and rubisco content was significant in 9 genotypes of the second experiment.     

Antioxidant properties of trans-epsilon-viniferin as compared to stilbene derivatives in aqueous and nonaqueous media

trans-Epsilon-viniferin, the dimer of resveratrol, extracted from Vitis vinifera, has been evaluated for its antioxidant capacity. Its properties have been compared to those of resveratrol and synthetic stilbenic derivatives (4-hydroxystilbene, 4,4'-dihydroxystilbene, 3,5-dihydroxystilbene, and trimethylresveratrol), in regard to their liposolubility using two media with different polarity. The bleaching of beta-carotene by lipoperoxyl (LOO.) radicals in an oil/water (O/W) emulsion and the scavenging of superoxide anions (O(-)(2) in dimethyl sulfoxide (DMSO) using 5,5-dimethyl-1-pyrroline-N-oxide as a spin trap were followed using UV-visible and electron paramagnetic resonance, respectively. Epsilon-viniferin exhibits the best antioxidant capacity in the DMSO/O(-)(2) polar system (IC(50) = 0.14 mM) while 4,4'-dihydroxystilbene presents the highest antioxidant capacity in the O/W/LOO. system (inhibition of beta-carotene bleaching, 82%). Partition coefficients and kinetics of partition between 1-octanol and water were measured to discuss the antioxidant efficiency of the compounds in relation with their chemical structure.     

Voracious invader or benign feline? A review of the environmental biology of European catfish Silurus glanis in its native and introduced ranges*

A popular species for food and sport, the European catfish (Silurus glanis) is well‐studied in its native range, but little studied in its introduced range. Silurus glanis is the largest‐bodied freshwater fish of Europe and is historically known to take a wide range of food items including human remains. As a result of its piscivorous diet, S. glanis is assumed to be an invasive fish species presenting a risk to native species and ecosystems. To assess the potential risks of S. glanis introductions, published and ‘grey’ literature on the species’ environmental biology (but not aquaculture) was extensively reviewed. Silurus glanis appears well adapted to, and sufficiently robust for, translocation and introduction outside its native range. A nest‐guarding species, S. glanis is long‐lived, rather sedentary and produces relatively fewer eggs per body mass than many fish species. It appears to establish relatively easily, although more so in warmer (i.e. Mediterranean) than in northern countries (e.g. Belgium, UK). Telemetry data suggest that dispersal is linked to flooding/spates and human translation of the species. Potential impacts in its introduced European range include disease transmission, hybridization (in Greece with native endemic Aristotle’s catfish [Silurus aristotelis]), predation on native species and possibly the modification of food web structure in some regions. However, S. glanis has also been reported (France, Spain, Turkmenistan) to prey intensively on other non‐native species and in its native Germany to be a poor biomanipulation tool for top‐down predation of zooplanktivorous fishes. As such, S. glanis is unlikely to exert trophic pressure on native fishes except in circumstances where other human impacts are already in force. In summary, virtually all aspects of the environmental biology of introduced S. glanis require further study to determine the potential risks of its introduction to novel environments.     

Fine root dynamics along an elevational gradient in the southern Appalachian Mountains,USA

Attributes of fine roots (<2.0 mm diameter) were quantified in five southern Appalachian plant communities along an elevational gradient. These attributes include the seasonal dynamics of fine root mass and length, the depth distribution of fine roots, fine root width and, most importantly, the annual appearance and disappearance of fine roots. The principal objectives of this study were two-fold: (1) to compare these attributes of fine roots between plant communities and (2) to compare the results of the two methods used to quantify the attributes: (1) harvesting roots from forest soil with soil cores and (2) photographing roots growing against the windows of minirhizotron boxes. The plant communities that were sampled are characteristic of the region and are designated as follows from lowest elevation (782 m) to highest elevation (1347 m): (1) xeric ridge, (2) cove hardwoods, (3) low elevation mixed oak, (4) high elevation mixed oak, and (5) northern hardwoods. Fine root mass varies seasonally in this temperate region with lowest and highest mass in the spring and autumn, respectively. Fine root mass and fine root mass appearance were lowest in the cove hardwood community and highest in the low elevation mixed oak community. The total length of fine roots was highest in the xeric ridge community and lowest in the low elevation mixed oak community. The high total root length in the xeric ridge community was due to the presence of an exceptionally dense mat of very fine roots found there. The width of these roots was significantly less than that of roots on all other plots. Subsequent regression illustrates two strong patterns in the data. First, fine root mass, fine root mass appearance and leaf production were positively correlated. Second, fine root length and soil moisture were negatively correlated. The accumulation of root mass in these communities was linked to overall site productivity and the development of root length in response to moisture stress. Only the timing of root growth initiation was related to elevation and the associated parameter of soil temperature. The best estimates of fine root appearance and disappearance were generated by harvesting roots rather than photographing them. Some methodological problems with root photography implemented in this study are addressed.     

How do biodiversity patterns of river animals emerge from the distributions of common and rare species?

We studied the patterns of commonness and rarity for one vertebrate (fish) and four freshwater insect taxa (Ephemeroptera, Plecoptera, Trichoptera and Coleoptera) in southwestern France (57,000 km²), and we analysed the relationships between the location of sites and the contribution of commonness and rarity to species richness within a large stream system. Richness patterns in fish and aquatic insects were related to the location of sites within the stream system. The number of common and rare fish species increased from up- to downstream areas as a result of downstream additions of species. The number of common insect species peaked in the intermediate section of the river continuum, whereas rarity increased with decreasing elevation. In all taxa, common species gave a closer approximation to overall patterns of species richness than did rare ones. The biodiversity patterns of river animals emerged from convergence in the distributions of common and rare species (fish), or mostly from the distribution of common species (insects). However, in fish, Ephemeroptera and Plecoptera, the rarer species became almost equally, or more strongly correlated with overall species richness when increasing information along the common-to-rare and rare-to-common sequences. These patterns suggested that rarer species show a similar or stronger affinity, on a species-for-species basis, for high richness areas than do the commoner species. These schemes have implications for biodiversity assessments, as studies using common species richness to target important areas for monitoring or conservation efforts within stream systems will not necessarily identify areas important for rare species, and vice versa.     

Indirect host effect on ectomycorrhizal fungi: Leaf fall and litter quality explain changes in fungal communities on the roots of co-occurring Mediterranean oaks

Host trees can modify their soil abiotic conditions through their leaf fall quality which in turn may influence the ectomycorrhizal (ECM) fungal community composition. We investigated this indirect interaction using a causal modelling approach. We identified ECM fungi on the roots of two coexisting oak species growing in two forests in southern Spain - Quercus suber (evergreen) and Quercus canariensis (winter deciduous)-using a PCR-based molecular method. We also analysed the leaf fall, litter and soil sampled beneath the tree canopies to determine the concentrations of key nutrients. The total mycorrhizal pool was comprised of 69 operational taxonomic units (OTUs). Tomentella and Russula were the most species-rich, frequent and abundant genera. ECM fungi with epigeous and resupinate fruiting bodies were found in 60% and 34% of the identified mycorrhizas, respectively. The calcium content of litter, which was significantly higher beneath the winter-deciduous oak species due to differences in leaf fall quality, was the most important variable for explaining ECM species distribution. The evaluation of alternative causal models by the d-sep method revealed that only those considering indirect leaf fall-mediated host effects statistically matched the observed covariation patterns between host, environment (litter, topsoil, subsoil) and fungal community variables.     

Geographical barriers and ecological gradients: Geographical distribution of the subspecies and morphotypes of Deutonura deficiens Deharveng, 1979 (Collembola: Neanuridae)

This work explores the links between ecogeographical barriers and clines, and the boundaries of infraspecific biological entities. The distribution of the three subspecies and eight morphotypes of the Neanurinae Deutonura deficiens (Collembola) are mapped and commented based on 570 records. The species inhabits a wide range of forest habitats from the north of Portugal to southeastern France. The subspecies and morphotypes constitute homogeneous geographic sets arranged as a mosaic of closely related forms. A few overlapping zones between subspecies or morphotypes have been detected, some of them having the character of hybrid zones; on the whole however, overlap is small or rare and allopatry or parapatry is the general pattern. Current range boundaries of subspecies and morphotypes were found to be usually not determined by major hydrographical and topographical barriers, with the noticeable exception of the Rhône River. At subspecies level, the morphological cline of increasing tuberculization correlated to the bioclimatic gradient from Mediterranean to Atlantic climates, already recorded by Deharveng (1984. Polymorphisme et polytypisme morphologiques chez quelques Neanurinae européens. Rev. Ecol. Biol. Sol. 21, 533–562), is confirmed on the present data set. Conversely, ecological boundaries, known to constrain species distribution in many living groups of the region, do not fit the contact zones between the different morphotypes of the three subspecies of D. deficiens. The eight recognized forms appear to be at different degrees of reproductive isolation, illustrating active speciation process possibly inherited from recent ecogeographical events. A more detailed sampling on contact zones and a robust phylogenetic hypothesis are needed at this stage for progressing in our understanding of this complex pattern.     

Retention of Staphylococci and Total Coliforms During Wastewater Percolation Through Equatorial Soil in Central Africa: The Role of the Soil Column Near Soil Surface and that Closely Above Groundwater Table

Groundwater protection from pollutants depends mostly on retention potentials of soil above groundwater table. Soil separating soil surface from groundwater table is made up of several layers and can be divided into different columns along its vertical transect. Wastewater percolation tests were carried out through one soil column CA, in contact with soil surface and through another CB, closely above groundwater table. The aim of the study was to assess the importance of soil columns CA and CB, in total coliforms and staphylococci retention during wastewater infiltration or groundwater recharge, in equatorial soils in Central African region. The results showed that, the fraction of total coliforms retained through soil column CA varied with respect to wastewater loads applied on top of soil column, from 69.22% to 99.95%, relative to the total coliforms concentration deposited on top. The fraction of total coliforms retained through CB varied with respect to wastewater loads applied, from 96.98 to 99.89% relative to the total coliforms deposited on top. Through both soil columns, fractions of staphylococci retained was in the order of 99.99% relative to the total staphylococci concentration deposited on top. For the whole bacteriological analysis, the fractions of total coliforms retained seems to be greater through deeper soil column than that of upper soil column. The bacterial contaminants retained relative to their concentrations in wastewater poured on soil column surfaces, varied from 6.17 log units to 9.73 log units. An applied load of 100 ml seemed to lead to the bacterial pollutants transported through both soil columns studied. NH₄ ⁺ was retained by fractions varying from 97.37 to 98.74%. Concentrations of various contaminants found in groundwater would be a tiny part, relative to quantities deposited on soil surface. Bacterial retention potentials of soil column separating soil surface from groundwater table during wastewater percolation, varies along its transect. It would be due to numerous and variable physical, chemical and structural properties of soil layers and bacteria on the one hand, and to results of various interactions between soil layer particles and cell bacteria, on the other hand.     

Evidence for proteolysis of a recombinant prion protein in a lamb brain‐amended loamy soil

Soils contaminated by prions, the infectious agents responsible for transmissible spongiform encephalopathy diseases, remain infectious to grazing animals for many years. In this study, the ability of enzymes produced by soil microbes to degrade a recombinant prion protein (recPrP) was investigated in a loamy soil. A ¹⁵N‐labelled recPrP was added to soil in which microbial biomass and soil proteolytic activity had been increased by either simultaneous or prior amendment with lamb brain, and distribution of ¹⁵N among soil solid particles, soluble molecules and bacterial biomass was determined. After 1 day the proportions of recovered recPrP‐N associated with microbial biomass and soluble molecules were 6–9 and 15–19%, respectively, which is consistent with the hypothesis of degradation. A greater incorporation of ¹⁵N‐derived β‐sheeted recPrP into the microbial biomass pool occurred when the soil proteolytic activity was pre‐stimulated by a lamb brain amendment, suggesting that the recPrP degradation in soil is mediated by the activity level of proteolytic enzymes produced by the microbial biomass. The majority (35–87%) of the recovered recPrP‐N was associated with the soil particles. An observed partial degradation of recPrP deposited on a mica surface by soil soluble enzymes indicated a sorption‐related resistance to proteolysis. In conclusion, integration of the stimulation and turnover of the soil microbial component, after an input of a large amount of animal organic matter with the sorption properties of prion protein, is required to model and predict prion survivability, transformation and transmissibility in soil.     

Synthesis of carbenes through substitution reactions at a carbene center

An (amino)(phosphino) carbene can be transformed into (amino)(phosphonio) carbenes, which undergo nucleophilic intermolecular as well as intramolecular substitution reactions at the carbene center. A variety of carbenes can be synthesized starting from a single carbene precursor. The resulting gamut of electronic and steric effects possible should open the way not only to a detailed study of the mechanism, but also to the subsequent improvement of catalytic reactions that involve carbene-transition metal complexes.