Effects of root exudates and humic substances on weathering kinetics

The effect of complex natural organic ligands on the weathering kinetics of aluminum oxide was investigated in laboratory experiments. A peat-derived humic substance and root exudates obtained from ectomycorrhizal (Picea abies — Hebeloma crustuliniforme) and non-mycorrhizal Norway Spruce trees; and γ-Al₂O₃ were used as a model system. The experimental weathering rates are in accordance with a surface-controlled dissolution mechanism. The effect of the humic material on dissolution rates appears to depend on the degree of protonation of the humic (macro)molecules: we observed dissolution-enhancement or -inhibition at pH 3 and 4, respectively. Ectomycorrhizal exudates proved to be effective weathering agents at pH 4, as opposed to humic material and non-mycorrhizal exudates. Our results suggest that (i) the role of humic materials in mineral weathering and podzolization is different from what is commonly thought, and (ii) mineral weathering rates in the rhizosphere may be higher than in the bulk soil.     

First report of Hymenoscyphus fraxineus on Fraxinus excelsior in Montenegro

During the monitoring of the mycological complex on different forest tree species in the Biogradska Gora National Park in north‐east Montenegro, symptoms indicative of ash dieback caused by Hymenoscyphus fraxineus were observed on young Fraxinus excelsior trees in the protected virgin forest, including dieback of plants and branches, wilting of leaves and shoots leading to a “flag‐like” habitus, premature shedding of leaves and longitudinal bark necroses. Using standard isolation methods, slow‐growing cultures with numerous phialides, typical of the asexual phase of the ash dieback fungus, were obtained. In addition, petioles with numerous characteristic apothecia were also recorded. This is the first report of H. fraxineus on common ash in Montenegro. Possible pathways of introduction and implications of the findings are discussed.     

Feynman's path-integral approach for intense-laser-atom interactions

Atoms interacting with intense laser fields can emit electrons and photons of very high energies. An intuitive and quantitative explanation of these highly nonlinear processes can be found in terms of a generalization of classical Newtonian particle trajectories, the so-called quantum orbits. Very few quantum orbits are necessary to reproduce the experimental results. These orbits are clearly identified, thus opening the way for an efficient control as well as previously unknown applications of these processes.     

Study of the genetic variability of porcine circovirus type 2 detected in Serbia and Slovenia

Recent variants of porcine circovirus type 2 (PCV2) were obtained from tissues of domestic pigs with porcine circovirus associated disease and from randomly selected wild boar samples from Serbia and Slovenia. A 450-base-pair nucleotide sequence was obtained by PCR from the ORF2. The derived nucleotide and amino acid sequences were aligned and compared to the corresponding region of closely related PCV2 sequences determined in previous years and retrieved from the GenBank. The 30 Serbian and 17 Slovenian PCV2 sequences clustered into three previously determined genotypes (PCV2a: 7), (PCV2b: 38) and (PCV2d: 2). Three major variable regions, concerning 29 amino acid position substitutions within the ORF2, were observed, which further supports the segregation of the detected strains into three separate genotypes. This study indicates that PCV2b is the predominant genotype in Serbia and Slovenia and the detected PCV2 strains are closely related to those previously described in Europe and in other parts of the world.     

Bemerkungen über die Populationsbewegungen der Mittelmeerfruchtfliege (Ceratitis capitata Vied.) an der jugoslawischen Adriaküste

Zusammenfassung Untersuchungen über den Massenwechsel und die Biologie der MittelmeerfruchtfliegeCeratitis capitata Vied. während der letzen 5 Jahre führten zu folgenden Ergebnissen:1. Die Mittelmeerfruchtfliege, die bis 1947 in ganz Jugoslawien unbekannt war, kommt seit mindestens zehn Jahren auch an der Adriaküste vor.2. Erst im Jahre 1958 erwies sich die Fruchtfliege als Schädling verschiedener Obstarten.3. Wie aus Beobachtungen in Obstanlagen an der Adriaküste hervorgeht, befällt die Fliege in erster Linie Pfirsich, ferner auch Birne, Kaki, Feige, Apfel, Pflaume, Orange und grünen Paprika. Im Laboratorium gelang die Zucht außerdem noch an Banane, nicht aber an Tomate und Trauben.4. ObwohlC. capitata ein polyphages Insekt ist, befällt sie an einigen Stellen, wo sie regelmäßig große Häufigkeit aufweist, nur Pfirsich (Split, Debeli Rti) bzw. nur Kaki (Ankaran). In manchen Obstgärten lebt sie aber an verschiedenen Früchten (Podstrana, Stroanac). Es gibt bei der Fruchtfliege also auf Obstarten spezialisierte Populationen und solche, die an verschiedenen Obstarten vorkommen.5. Unter den in unserem Küstenland herrschenden Klimabedingungen kann die Fruchtfliege in einem Jahr 4–5 Generationen entwickeln. Die Herbstgeneration verpuppt sich Ende Oktober/Anfang November in der Erde, die Imagines verlassen bis Januar die Puppen und warten auf das Reifen der ersten, frühen Pfirsichsorten. Die gleiche Überwinterungsweise wurde auch an der Olivenfliege beobachtet.6. Mit Angelica-Öl versehene Fanggläser brachten nur zum Teil befriedigende Ergebnisse, da dieser Lockstoff nur die Männchen anzieht, aber auch nur in der Zeit, in der die Fliegen überhaupt selten sind. Im Spätsommer und Herbst wirkt ein aus Kleie und Biammonphosphat bereiteter Köder auf beide Geschlechter stark anlockend.     

Potentially toxic elements in the riparian soils of the Sava River

Purpose

Riparian zone contamination is a growing problem for several European catchments due to high anthropogenic pressures. This study investigates As, Cd, Cr, Cu, Ni, Pb, and Zn concentrations in the Sava River riparian zone, characterized by wide agricultural areas, various geological substrates, and different types of industrial pollution. The accumulation and mobility of these elements were studied because they are listed as priority substances in the Water Framework Directive and environmental objectives for surface waters.

Materials and methods

Sampling was performed during the sampling campaign of the EU 7th FW-funded GLOBAQUA project in September 2015 during a low-water event. Soil samples were collected along the Sava River at 12 selected sampling sites, from a depth of 0–30 cm, at a distance of 10–15 m from the river bank. The extent of pollution was estimated by determining total and readily soluble element concentrations in the soils. Potential ecological risk and the source of the selected elements in the soils was determined using the enrichment factor (EF), potential ecological risk index (RI), and statistical methods such as the principal component analysis (PCA) and multiple linear regression analysis (MLRA).

Results and discussion

This study showed that concentrations of the selected elements increase along the Sava. In terms of origin, PCA and MLRA indicated that Cr and Ni in soils are predominantly lithogenic, while As, Cd, Pb, and Zn are both lithogenic and anthropogenic (ore deposits, industry, and agriculture). PCA singled out Cu since its origin in soil is most probably from specific point-source pollution. EF was generally minor to moderate for most of the examined elements, apart from Cu, for which the EF was significant at one sampling site. Overall ecological risk (RI) fell within the low-risk category for most sites, apart from Belgrade sampling site (BEO), where high total Cd content affected individual and overall ecological risk indicators, indicating Cd could represent a considerable ecological risk for the downstream riparian zone.

Conclusions

At downstream sites, there was a noticeable increase in PTE content, with Cd, Cr, Ni, and Zn exceeding the proposed threshold values for European soils, indicating rising contamination in riparian soils. In terms of the ecological risk, only Cd could pose a potential ecological threat for the downstream riparian zone.

     

Phosphorus-use efficiency of kale genotypes from coastal Croatia

Understanding the mechanisms of phosphorus (P)-use efficiency (PUE) may contribute to enhancing crop P nutrition because species growth variability at low-P is well known. The experiment was carried out to evaluate the response of kale genotypes to different P supply in randomized block design in three replications. Low-P supply led to a decrease in most parameters, whereas an increase was recorded in root growth parameters. Genotypes differed in shoot dry weight (DW), leaf area, root length and area, and shoot and root P content and concentration. Root traits significantly positively correlated with PUE. Genotypes Red Russian (RR) and IJK 17 were superior in terms of shoot DW production at low P supply, and had the highest uptake efficiency. Genotypes IJK 17 and 81 had the highest P utilization efficiency, while Vates blue curled (VBC) showed the lowest PUE. Genotypes had similar shoot P content and concentration at low P supply, but large PUE differences, implying the importance of P utilization efficiency.     

Oxidant/antioxidant properties of Croatian native propolis

Native propolis was defined as propolis powder collected from the continental part of Croatia and prepared according to a patented process that preserves all the propolis natural nutritional and organoleptic qualities. Nine phenolic compounds (out of thirteen tested) in propolis sample were detected by high performance liquid chromatography (HPLC) analysis. Among them chrysin was the most abundant (2478.5 microg/g propolis). Contrary to moderate antioxidant activity of propolis examined in vitro (ferric reduction antioxidant power; FRAP-assay), propolis as a food supplement modulated antioxidant enzymes (AOE) and significantly decreased lipid peroxidation processes (LPO) in plasma, liver, lungs, and brain of mice. The effect was dose- and tissue-dependent. The lower dose (100 mg/kg bw) protected plasma from oxidation, whereas the higher dose (300 mg/kg bw) was pro-oxidative. Hyperoxia (long-term normobaric 100% oxygen) increased LPO in all three organs tested. The highest vulnerability to oxidative stress was observed in lungs where hyperoxia was not associated with augmentation of AOE. Propolis protected lungs from hyperoxia by increased catalase (CAT) activity. This is of special importance for lungs since lungs of adult animals are highly vulnerable to oxidative stress because of their inability to augment AOE activity. Because of its strong antioxidant and scavenging abilities, native propolis might be used as a strong plant-based antioxidant effective not only in physiological conditions but also in cases that require prolonged high concentration of oxygen.     

Comment on "Nonreciprocal light propagation in a silicon photonic circuit"

We show that the structure demonstrated by Feng et al. (Reports, 5 August 2011, p. 729) cannot enable optical isolation because it possesses a symmetric scattering matrix. Moreover, one cannot construct an optical isolator by incorporating this structure into any system as long as the system is linear and time-independent and is described by materials with a scalar dielectric function.     

Application of computer-assisted semen analysis to explain variations in pig fertility

Sperm quality is often evaluated through computer-assisted semen analysis (CASA) and is an indicator of boar fertility. The aim of this research was to study the relationship between CASA motility parameters and fertility results in pigs. Insemination records and semen parameters from a total of 45,532 ejaculates collected over a 3-yr period were used. The statistical model for analysis of fertility data from these inseminations included factors related to sow productivity. The boar- and semen-related variance (direct boar effect) were corrected for the effects of individual boar, genetic line of the boar, age of the boar, days between ejaculations, number of sperm cells in an ejaculate, number of sperm cells in an insemination dose, and AI station. The remaining variance was analyzed if semen motility parameters had a significant effect. This analysis revealed significant (P < 0.05) effects of progressive motility, velocity curvilinear, and beat cross frequency on farrowing rate (FR). Total motility, velocity average path, velocity straight line, and amplitude of lateral head displacement affected (P < 0.05) total number of piglets born (TNB). Boar- and semen-related parameters explained 5.3% of the variation in FR and 5.9% of the variation in TNB. Motility parameters, measured by CASA, explained 9% of the boar- and semen-related variation in FR and 10% of the boar- and semen-related variation in TNB. Individual boar and genetic line of the boar affected (P < 0.0001) the variation in FR and TNB. No differences (P > 0.05) were observed between effects of AI stations on fertility outcome, underscoring the objectivity of the CASA system used. Motility parameters can be measured with CASA to assess sperm motility in an objective manner. On the basis of the motility pattern, CASA enables one to discriminate between the fertilizing capacity of ejaculates, although this depends on the genetic line of the boar used in AI stations.