Lignite pre-treatment and its effect on bio-stimulative properties of respective lignite humic acids

Humic acids originating from South-Moravian lignite were subjected to a comparative study with the aim to assess the alteration of their physico-chemical properties after various lignite pre-treatments. Physical modification was achieved with two organic acids, such as acetic acid and citric acid and chemical modification by nitric acid and hydrogene peroxide in various concentrations. Elemental analysis, solid-state NMR, GC–MS analysis of polyols and size exclusion chromatography were carried out for chemical–physical characterization of obtained humic acids. Their biological effect, in form of potassium and ammonium humates, was tested on maize (Zea mays) seedlings. In these tests, potassium humates achieved far better overall results than ammonium humates. Results were inter-correlated in order to appraise the influence of humic acids physical and chemical properties on biological activity. Surprisingly, fractions with the lowest molecular size (0–35 kDa) showed no correlation with bioactivity results (Pearson coefficient from 0.05 to −0.4). On the contrary, middle-sized fractions (35–175 kDa) showed highly significant positive correlation (Pearson coefficient up to 0.92) and the highest molecular-size-fractions (275–350 kDa) showed negative correlation (Pearson coefficient up to −0.75). These findings were identical for both potassium and ammonium humates. No connection was found between bioactivity of humates and polyols content which was remarkably high; it reached 150 mg per g of humic acids in the most extreme case of 5% hydrogene peroxide pre-treatment. In the final analysis, the preparation mode bore pivotal responsibility for the control of humic acids biological effect and showed the best results for potassium humates obtained from lignite pre-treated by acetic acid and by 2% hydrogen peroxide.     

Porcine CD18 mediates Actinobacillus pleuropneumoniae ApxIII species-specific toxicity

Actinobacillus pleuropneumoniae, the causative agent of porcine pleuropneumonia, produces Apx toxins that are recognized as major virulence factors. Recently, we showed that ApxIIIA-cytotoxic activity specifically targets Sus scrofa leukocytes. Since both LtxA from Aggregatibacter actinomycetemcomitans (aggressive periodontitis in humans) and LktA from Mannheimia haemolytica (pneumonia in ruminants) share this characteristic, respectively towards human and ruminant leukocytes, and because both use the CD18 subunit to interact with their respective LFA-1, we hypothesized that ApxIIIA was likely to bind porcine CD18 to exercise its deleterious effects on pig leukocytes. A β ₂−integrin-deficient ApxIIIA-resistant human erythroleukemic cell line was transfected either with homologous or heterologous CD11a/CD18 heterodimers using a set of plasmids coding for human (ApxIIIA-resistant), bovine (-resistant) and porcine (-susceptible) CD11a and CD18 subunits. Cell preparations that switched from ApxIIIA-resistance to -susceptibility were then sought to identify the LFA-1 subunit involved. The results showed that the ApxIIIA-resistant recipient cell line was rendered susceptible only if the CD18 partner within the LFA-1 heterodimer was that of the pig. It is concluded that porcine CD18 is necessary to mediate A. pleuropneumoniae ApxIIIA toxin-induced leukolysis.     

Spatial distribution of sediments and transfer properties in soils in a stormwater infiltration basin

Purpose  

The aim of our study was to characterise the heterogeneity of sediment distribution in a stormwater retention/infiltration basin (Pont de Cheviré, Nantes, France) and to determine the impact of this distribution on water transfer properties in the soil.     

Floristic and ecological differences between recent and ancient forests growing on non-acidic soils

The aim of this work was to investigate differences in soil chemistry and understory composition between recent forests (sites afforested in the last 170 years) and ancient forests growing on non-acidic soils. The study was carried out on hardwood forests at moderate elevation (400–600 m asl) in the Jura Mountains (N.E. France) on four main pedological substrates with different characteristics. The floristic composition of 127 stands from recent forests (n = 65) or ancient forests (n = 62) was surveyed. Some functional traits and the Ellenberg indicator values of the surveyed species were recorded. In addition, the topsoil from 30 stands was analysed. The composition of the flora was analysed by Detrended Correspondence Analysis and the species which were typical of one class of forest age were identified using a chi-square (χ²) test. The difference between forest classes for plant traits, their indicator values, or soil chemistry was tested using the generalized linear model and Bonferroni t-tests (or Kruskall–Wallis tests). The floristic composition of the ancient forests was significantly different from that of the recent forests and was characterized by a high occurrence of shrub species in recent forests. These differences were associated with higher specific leaf area, low-range seeds dispersal, and some life forms like geophytes. There was no clear difference in soil chemistry between the two classes of forests, except for δ¹⁵N values. The weakness of the difference in the soil between ancient and recent forests suggested that changes in soil chemistry caused by a former agricultural land use were not responsible for the differences in understory composition recorded. The differences in functional traits between the two forest classes supported this conclusion. We finally concluded that (i) past land use modifies the vegetation composition of current forests, even on neutral soils and that (ii) in our context, biological filters were probably responsible for these changes.     

Odor Modification in Salmon Hydrolysates Using the Maillard Reaction

The aim of this work was to study the effect of adding sugar during proteolysis to promote the Maillard reaction and mask the initial fish odor and off-flavors generated. An experimental design, based on the Doehlert plan, was used to study the influence of hydrolysis conditions (time, temperature, sugar, and antioxidant addition) on the odor characteristics of hydrolysates, soluble protein levels, and amino acid content. Results showed that the lowest level of sugar (10 g of D-xylose added to 1 kg of by-products) was enough to develop a grilled odor in hydrolysates. In the hydrolysis conditions used—i.e., enzyme inactivation at 95°C for 30 min—hydrolysis temperature had no effect on grilled odor production but significantly affected the soluble protein fraction, as did hydrolysis time. Soluble protein content and essential amino acid content increased with the enzymatic reaction but were not modified by adding sugar. Hydrolysis conditions that promote Maillard reactions while keeping a nutritional balance have been identified.     

An inconvenient truth about xylem resistance to embolism in the model species for refilling <Emphasis Type="Italic">Laurus nobilis</Emphasis> L.

Key message

Direct, non-invasive X-ray microtomography and optical technique observations applied in stems and leaves of intact seedlings revealed that laurel is highly resistant to drought-induced xylem embolism. Contrary to what has been brought forward, daily cycles of embolism formation and refilling are unlikely to occur in this species and to explain how it copes with drought.

Context

There has been considerable controversy regarding xylem embolism resistance for long-vesselled angiosperm species and particularly for the model species for refilling (Laurus nobilis L.).

Aims

The purpose of this study was to resolve the hydraulic properties of this species by documenting vulnerability curves of different organs in intact plants.

Methods

Here, we applied a direct, non-invasive method to visualize xylem embolism in stems and leaves of intact laurel seedlings up to 2-m tall using X-ray microtomography (microCT) observations and the optical vulnerability technique. These approaches were coupled with complementary centrifugation measurements performed on 1-m long branches sampled from adult trees and compared with additional microCT analyses carried out on 80-cm cut branches.

Results

Direct observations of embolism spread during desiccation of intact laurels revealed that 50% loss of xylem conductivity (Ψ₅₀) was reached at ??7.9?±?0.5 and ??8.4?±?0.3 MPa in stems and leaves, respectively, while the minimum xylem water potentials measured in the field were ??4.2 MPa during a moderate drought season. Those findings reveal that embolism formation is not routine in Laurus nobilis contrary to what has been previously reported. These Ψ₅₀ values were close to those based on the flow-centrifuge technique (??9.2?±?0.2 MPa), but at odds with microCT observations of cut branches (??4.0?±?0.5 MPa).

Conclusion

In summary, independent methods converge toward the same conclusion that laurel is highly resistant to xylem embolism regardless its development stage. Under typical growth conditions without extreme drought events, this species maintains positive hydraulic safety margin, while daily cycles of embolism formation and refilling are unlikely to occur in this species.