Effect of phosphorus supply on root traits of two Brassica oleracea L. genotypes

BACKGROUND: Phosphorus (P) deficiency limits crop production worldwide. Crops differ in their ability to acquire and utilise the P available. The aim of this study was to determine root traits (root exudates, root system architecture (RSA), tissue-specific allocation of P, and gene expression in roots) that (a) play a role in P-use efficiency and (b) contribute to large shoot zinc (Zn) concentration in Brassica oleracea. RESULTS: Two B. oleracea accessions (var. sabellica C6, a kale, and var. italica F103, a broccoli) were grown in a hydroponic system or in a high-throughput-root phenotyping (HTRP) system where they received Low P (0.025 mM) or High P (0.25 mM) supply for 2weeks. In hydroponics, root and shoot P and Zn concentrations were measured, root exudates were profiled using both Fourier-Transform-Infrared spectroscopy and gas-chromatography-mass spectrometry and previously published RNAseq data from roots was re-examined. In HTRP experiments, RSA (main and lateral root number and lateral root length) was assessed and the tissue-specific distribution of P was determined using micro-particle-induced-X-ray emission. The C6 accession had greater root and shoot biomass than the F103 accession, but the latter had a larger shoot P concentration than the C6 accession, regardless of the P supply in the hydroponic system. The F103 accession had a larger shoot Zn concentration than the C6 accession in the High P treatment. Although the F103 accession had a larger number of lateral roots, which were also longer than in the C6 accession, the C6 accession released a larger quantity and number of polar compounds than the F103 accession. A larger number of P-responsive genes were found in the Low P treatment in roots of the F103 accession than in roots of the C6 accession. Expression of genes linked with "phosphate starvation" was up-regulated, while those linked with iron homeostasis were down-regulated in the Low P treatment. CONCLUSIONS: The results illustrate large within-species variability in root acclimatory responses to P supply in the composition of root exudates, RSA and gene expression, but not in P distribution in root cross sections, enabling P sufficiency in the two B. oleracea accessions studied

Analize bakrovih zlitin na nožnici rimskega meča iz Ljubljanice

The method of proton induced X-ray emission (PIXE) analysis was applied for studies of the metal composition of copper-based alloys on the scabbard of a Roman gladius, discovered in the river Ljubljanica. The scabbard fitments were made of brass, except for small parts of the U-shaped lining made of bronze. The fitting components were bound by riveting and soldering using a tin-lead alloy. The analysis testifies to the use of brass in the early Augustan era. The reliability of the PIXE results is discussed.Z metodo protonsko vzbujenih rentgenskih žarkov (PIXE) smo določili sestavo bakrovih zlitin na nožnici rimskega meča, ki je bil najden v strugi Ljubljanice. Nožnično okovje je narejeno iz medenine, le majhni deli podlage v obliki črke U so iz brona. Posamezni sestavni deli okovja so spojeni s kovičenjem in spajkanjem, pri čemer so uporabili kositrno-svinčev lot. Rezultati analize potrjujejo rabo medenine v zgodnjem avgustejskem obdobju. Zanesljivost dobljenih rezultatov smo ocenili z modeliranjem

Internalization of Consumed TiO2 Nanoparticles by a Model Invertebrate Organism

There is little in vivo data concerning the fate of ingested TiO2 nanoparticles (nano-TiO2). We report here experiments aimed at assessing if ingested nano-TiO2 accumulates in the digestive gland epithelium or are internalized elsewhere in the body of the terrestrial isopod crustaceans. The animals (Porcellio scaber, Isopoda, Crustacea) fed for 3, 7, or 14 days on food dosed with 100 or 1000 μg nano-TiO2 showed no evidence of internalization of Ti measured by microparticle-induced X-ray emission method. The effect of ingested nanoparticles was measured by conventional toxicity measures such as feeding rate, weight change, and mortality and did not indicate any toxicity. However, cell membrane of digestive glands, measured with a modified method for assessing cell membrane stability, was affected already after 3 days of exposure to 1000 μg nano-TiO2 per gram dry weight of food indicating cytotoxic potential of ingested nanoparticles. Our results confirmed hypothesis on low toxic potential and no internalization of consumed TiO2 nanoparticles by a model invertebrate organism. However, cytological marker unequivocally indicated adverse effect of ingested nano-TiO2. We conclude that the isopod model system could be used for studying the fate and effect of ingested nanoparticles

International Conference Nuclear Energy for New Europe 2003 Neutral Molecules in Tokamak Edge Plasma -Role of Vibrationally Excited Hydrogen Molecules

ABSTRACT The role of neutral molecules in edge plasma is discussed with special emphasis on the vibrationally excited hydrogen. Neutral molecules are formed mostly by surface processes on the walls and then released to the edge plasma where they take part in volumetric reactions with other particles. Typically these molecules are formed in excited states and data are needed for their reactions on the wall and in the volume. Processes in edge plasma determine particle and energy flux what is especially critical issue in tokamak divertor region. Various cross sections and reaction rates are needed for modelling edge plasma and its interaction with walls

Geochemistry of speleothems affected by aragonite to calcite recrystallization – Potential inheritance from the precursor mineral

Formerly aragonite speleothems recrystallized to calcite result from solutions subsaturated in aragonite and supersaturated in calcite that infiltrate into the speleothem through the interconnected porosity. In most cases, the crystal replacement takes place through a thin solution film. This diagenetic process can occur under open or semi-closed geochemical conditions. Thus, secondary calcite crystals record the composition of the fluid at the time of diagenesis affected by calcite partition coefficients and fractionation factors (open system) or partly inherit the composition of the primary aragonite (semi-closed system). So, whether or not recrystallized aragonite speleothems can record reliable geochemical signals from the time of speleothem primary deposition still is an open debate. We studied a stalagmite from Eagle Cave (Spain) predominantly composed of secondary calcite that replaced aragonite, although a core of primary aragonite extending 45 mm along the growth direction was preserved at the base of the sample. We obtained Mg and Sr compositional maps, paired U–Th dating and δ18O and δ13C profiles across the diagenetic front. Additionally, two parallel isotope records were obtained along the speleothem growth direction in the aragonite and calcite sectors. Our results support that recrystallization of this speleothem took place in open system conditions for δ18O, δ13C, Mg and Sr, but in semi-closed system conditions for U and Th. The recrystallization of this sample took place during one or several events, likely after the Younger Dryas as a result of climate change influencing drip water composition. Based on compositional zoned patterns, we suggest that the advance of diagenetic fronts in this speleothem had an average rate of 50 ± 45 μm/yr. Such recrystallization rate can transform any aragonite speleothem into calcite within a few centuries. We suggest that the volume of water interacting with the speleothem at the time of recrystallization is of critical importance for inheritance of different elements. The volume of solution is controlled by (1) the discharge of water passing through the sample and (2) the lapse time between aragonite dissolution and calcite precipitation. Hydrology and hydrochemistry of the interacting solution, together with the mineralogy and texture of the speleothem are the essential controls for the diagenesis of the speleothem. Recrystallization of aragonite speleothems does not follow stratigraphical levels of the sample but occurs along sites with preferential flow paths in any sector of the speleothem. In these cases the relationship between age and distance from base is not preserved. However, alternation of periods of recrystallization with periods of aragonite precipitation causing speleothem accretion can result in recrystallized speleothems with coherent distance from the base-age relationship. Thus, early diagenesis of speleothems affected by seasonal or inter-annual oscillation of drip waters supersaturated and subsaturated in aragonite may provide best-scenario conditions for dating and preservation of paleoenvironmental records along recrystallized speleothems. However, even in this scenario, the variable discharge and the diagenetic rate control the geochemical inheritance from the primary aragonite crystals