bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nitrogen metabolism in flag leaf and grain of wheat in response to irrigation regimes
Authors: Xu Zhen‐Zhu , Yu Zhen‐Wen 
Published: January 2006

AbstractAlthough scarcity of irrigation water is one of the key limiting factors for wheat production in many regions of the world, by using partial irrigation at strategic times during the growing season, it might be possible to enhance productivity. We measured the changes in various parameters related to nitrogen (N) metabolism in flag leaf and grain of wheat (Triticum aestivum L.) plants (cv. Jinan 17 and Lumai 21), which were subjected to five irrigation regimes until physiological maturity. Severely deficient or excessive irrigation during grain filling decreased the photosynthetic rate (A), the concentrations of N, free amino acid, and soluble protein, as well as the activities of nitrate reductase (NR) and glutamine synthetase (GS) and increased malondialdehyde (MDA) accumulation and endopeptidase (EP) activity, though grain protein concentration might mainly depend on genotype. The activities of NR and GS were significantly positively correlated with A, but those of EP were significantly negatively correlated with A. The results indicate that while severe water stress aggravates the adverse effect on nitrogen metabolism, excessive soil moisture is also not useful during the grain‐filling stage, resulting in lower grain yield and quality. Our results suggest that applying an optimal irrigation regime in wheat fields still plays an important role in the improvement of grain yield and quality.
Spatial variation of tracer distribution in a structured clay field soil
Authors: Koszinski Sylvia , Quisenberry Virgil , Rogasik Helmut , Wendroth Ole 
Published: January 2006

AbstractWithin the sensitive soils of the River Oder Basin (E Brandenburg, Germany), chloride‐tracer transport was studied with respect to soil‐surface conditions of the well structured clayey topsoil (disturbed vs. undisturbed) and irrigation mode (flooding vs. sprinkling). The spatial variation of chloride and dye distribution was sampled in a regular grid within different soil depths. Different methods were used for the analysis of spatial heterogeneity: a heterogeneity index HI derived from fitting parameters of the cumulative distribution function, semivariogram analyses to identify the spatial representativity of observations and to classify the spatial variation, and Spearman's rank correlations to examine the spatial similarity of tracer distribution across different soil depths.Soil aggregation was obvious throughout the soil profile, and macropores and fractures were preferred flow paths for the tracer. Flood irrigation resulted in more “uniform” distribution than sprinkling did. However, preferential flow was identified for all treatments, where, once established below the surface layer, flow paths led to heterogeneity indices manifesting nonuniform flow and reduced lateral mixing between macropores and soil matrix. Within the flooded plot, spatial structure of chloride concentration was moderate unlike the strongly structured variation within the sprinkled plots.For purposes to generalize and to assess regional risk of the water and solute transport within the topsoil of the River Oder Basin, spatial autocorrelation ranges of about 15 cm should be considered and included into concepts of soil protection and land‐use management, soil‐sampling strategies, or modeling approaches.
Cold and hot water–extractable organic matter as indicators of litter decomposition in forest soils
Authors: Landgraf Dirk , Leinweber Peter , Makeschin Franz 
Published: January 2006

AbstractMild extractions were used as indicators of easily decomposable organic matter (OM). However, the chemical composition of extracted OM often remained unclear. Therefore, the composition of cold and hot water–extractable OM was investigated in the O horizons (Oi, Oe, Oa) of a 170 y old beech stand (Fagus sylvatica) in the Ore Mtns., SE Germany. To simulate litter decomposition, the O horizon samples were incubated for 1 week under defined conditions. Cold‐ and hot‐water extracts were analyzed and chemically characterized by pyrolysis–field ionization mass spectrometry (Py‐FIMS). The C and N concentrations were always lower in the cold‐(C: 2.69 to 3.95 g kg–1; N: 0.14 to 0.29 g kg–1) than in the hot‐water extracts (C: 13.77 to 15.51 g kg–1; N: 0.34 to 0.83 g kg–1). The C : N ratios of both extracts increased with increasing depth. Incubation increased the concentrations of C and N in all water extracts, while C : N ratios of extracts decreased. The molecular‐chemical composition of cold and hot water–extracted OM revealed distinct differences. Generally, cold water–extracted OM was thermally more stable than hot water–extracted OM. The mass spectra of the hot water–extracted organic matter revealed more intensive signals of carbohydrates, phenols, and lignin monomers. Additionally, the n‐C28 fatty acid and the n‐C38–to–n‐C52 alkyl monoesters clearly distinguished the hot‐ from the cold‐water extract. A principle‐component analysis visualized (1) alterations in the molecular‐chemical composition of cold‐ and hot‐water extracts due to previous incubation of the solid O horizon samples and (2) a decomposition from the Oi to the Oh horizon. This provides evidence that the macromorphological litter decomposition was reflected by the chemical composition of water extracts, and that Py‐FIMS is well‐suited to explain at the molecular level why OM decomposability is correlated with water‐extracted C.
Spatial variability of O layer thickness and humus forms under different pine beech–forest transformation stages in NE Germany
Authors: Bens Oliver , Buczko Uwe , Sieber Sonja , Hüttl Reinhard F. 
Published: January 2006

AbstractSpatial variability of humus layer (O layer) thicknesses can have important impacts upon soil water dynamics, nutrient storage and availability, as well as plant growth. The purpose of the present study was to elucidate the impact of forest‐transformation practices on the spatial variability of O layer thicknesses. The study focused on the Kahlenberg forest area (NE Germany) with stands of Scots pine (Pinus sylvestris)and European beech (Fagus sylvatica)of different age structures that form a transformation chronosequence from pure Scots pine stands towards pure European beech stands. Topsoil profiles including both, the O layer and the uppermost humic mineral soil horizon were excavated at intervals of 0.4 m along 15–20 m long transects, and spatial variability of O layer thicknesses was quantified by variogram analysis. The correlation lengths of total O layer thickness increased in the sequence consisting of pure pine stand (3.1 m) → older mixed stand (3.7 m) → pure beech stand (4.5 m), with the exception of the younger mixed stand, for which no correlation lengths of total O layer thickness could be determined. The degree of spatial correlation,i.e., the percentage of the total variance which can be described by variograms, was highest for the two monospecies stands, whereas this percentage was distinctly lower for the two mixed stands. A similar minimum for the two mixed stands was observed for the correlation lengths of the Oh horizon. These results suggest that the spatial structures of forest‐transformation stands may be interpreted in terms of a disturbance (in the form of the underplanting of beech trees). After this disturbance, the forest ecosystem requires at least 100 y to again reach relative equilibrium. These findings are in line with the results of other soil‐related investigations at these sites.
Effect of subcritical hydrophobicity in a sandy soil on water infiltration and mobile water content
Authors: Lamparter Axel , Deurer Markus , Bachmann Jörg , Duijnisveld Wilhelmus H. M. 
Published: January 2006

AbstractRecent research shows that most soils are more or less water repellent. Already subcritical water repellency may cause incomplete soil wetting and preferential flow. Both processes potentially reduce the residence time of water and solutes in the vadose zone, resulting in an enhanced risk of groundwater contamination. The objective of the present paper is, therefore, to evaluate the impact of reduced soil wettability on the soil water infiltration rate and to investigate the tendency towards preferential flow with the analysis of the immobile water content in the infiltration zone.In november 2002, a field experiment was done in a coniferous forest, 30 km N of Hannover, Germany. Soil hydrophobicity was quantified by measuring the contact angles. The hydraulic conductivity of the podsolic sandy soil was measured depth‐dependent with a double‐ring tension infiltrometer in three soil horizons. To quantify possible preferential‐flow effects, a LiBr‐Tracer was added to the infiltrating water to evaluate the mobile water‐content fraction after infiltration. Additionally, infiltration rates of water were compared with infiltration rates of ethanol which were determined after water infiltration at the same locations.Results show that the actual water repellency of field‐moist soil was mainly subcritical (contact angle <90°). Water infiltration rates were reduced due to subcritical repellency by a factor of 3–170 compared with ethanol infiltration rates (exclusion of wetting effects). This spatially variable infiltration behavior was not clearly reflected neither by the small‐scale contact‐angle measurements nor by the analysis of the average immobile soil water content in the infiltration zone. We conclude that this specific infiltration behavior of water caused by small‐scale wettability effects may temporarily reduce the local connectivity of water‐flow pathways.
Abbau von Isoproturon in Regenwurm‐Makroporen und in der Unterbodenmatrix – Eine Feldstudie
Authors: Bolduan Rainer , Zehe Erwin 
Published: January 2006

AbstractUm zu klären, wie lange durch präferenziellen Transport in den Unterboden gelangte Herbizide dort persistieren, wird beispielhaft der mikrobielle Abbau des Herbizids Isoproturon am Ende von Makroporen/Wurmgängen in 80–100 cm Tiefe mit dem Abbau in der umgebenden Bodenmatrix verglichen. Dazu wurde eine Methode entwickelt, welche die Messung des Isoproturon‐Abbaus in Makroporen unter Feldbedingungen erlaubt. Nach Voruntersuchungen zur Optimierung von Applikation und Probennahme wurden im Einzugsgebiet des Weiherbachs (Kraichgau, SW Deutschland) auf einer überdachten Versuchsparzelle 55 Wurmgänge mit einer Tiefe von 80–100 cm mit Isoproturon beimpft. In Boden der Versuchsparzelle wurden parallel Bodenfeuchte und ‐temperatur kontinuierlich gemessen. Jeweils 5–6 der beimpften Wurmgänge wurden alle 8 Tage herauspräpariert und auf ihren Gehalt an Isoproturon untersucht, um die Kinetik des Abbaus zu ermitteln. Parallel erfolgte die Untersuchung des Abbaus von Isoproturon in der die Wurmgänge umgebenden Bodenmatrix im Labor. Die Ergebnisse der Feld‐ und Laborversuche zeigen, dass der mikrobielle Abbau von Isoproturon direkt am Ende der Wurmgänge mit einem DT‐50‐Wert von 15,6 d ähnlich schnell erfolgt wie im Oberboden. Bereits wenige Zentimeter vom Zentrum des Wurmgangs entfernt zeigte sich in der umgebenden Unterbodenmatrix innerhalb von 30 d kein Abbau von Isoproturon. Diese deutliche Zunahme der Persistenzzeit konnte durch die wesentlich geringere mikrobielle Aktivität in der umgebenden Bodenmatrix erklärt werden. Für das Schicksal eines Herbizids, welches durch präferenzielle Fließereignisse in den Unterboden gelangt ist, ist somit entscheidend, ob es aus der Makropore in die umgebende Bodenmatrix transportiert wird oder nicht, denn die Abbauraten im Unterboden nehmen bereits nach wenigen Zentimetern um etwa eine Größenordnung ab. Aussagen dieser Genauigkeit sind selbst mit hochauflösenden Prozessmodellen bestenfalls für extrem gut untersuchte Standorte ableitbar.
How representatively can we sample soil mineral nitrogen?
Authors: Giebel Antje , Wendroth Ole , Isaak Reuter Hannes , Kersebaum Kurt‐Christian , Schwarz Jürgen 
Published: January 2006

AbstractSpatial distribution of soil mineral‐N content (Nmin) is a scale‐variant process. Precision farming assumes knowledge about the spatial distribution of Nmin. Moreover, sampling in management zones is based on the assumption of spatial dependence between sampling points. In the present study, variability structure of Nmin and the sources of variability were investigated. Within an agricultural landscape, Nmin was investigated across a field in a nested design over four consecutive years. Temporally unstable structure of individual nests require a sampling with several nests in the field. In the investigated field, 35%–49% of the total variability derived from small‐scale variability observed at spatial distances of <5 m and from sampling and analytical errors. Differences between 10 and 26 kg N ha–1 for the soil depth increment 0–60 cm can be expected. Uncertainty due to analytical errors were in the order of 5–10 kg N ha–1 for a 0–60 cm layer.
Influence of fruit treatments on perishability during cold storage of sweet chestnuts
Authors: Jermini Mauro , Conedera Marco , Sieber Thomas N , Sassella Alberto , Schärer Hans , Jelmini Giorgio , Höhn Ernst 
Published: January 2006

AbstractWith a view to enhancing the quality of local chestnut in southern Switzerland, the impact of three treatments [‘soaking’, ‘cold bath’ (hydrotherapy) and ‘warm bath’ (thermo‐hydrotherapy)] on the qualitative, chemical and sensory characteristics of the nuts during 90 days of cold storage was evaluated. Weight and water content decreased significantly with increasing duration of storage. Starch content decreased following a negative logistic trend. Sucrose, however, increased steeply according to a monomolecular trend and was significantly higher between 0 and 60 days of storage in the soaked chestnuts than in the cold‐bath treated nuts. The mean proportion of mouldy fruit remained constant at 27% for the warm‐bath treated nuts and increased from 16 to 30% for the cold‐bath treated fruit and from 28 to 63% for the soaked nuts during the 90 days of cold storage. The most frequently isolated moulds were Ciboria batschiana, Penicillium spp. and Mucor hiemalis. Warm and cold baths were successful in eliminating the larvae of Cydia splendana but the cold bath was inadequate to control Curculio elephas. Cold bath significantly reduced the sensory qualities (sweetness, aroma, texture) of the nuts, but made them easier to peel, as did the warm bath. Copyright © 2006 Society of Chemical Industry
Effects of germination on the activities of amylases and phenolic enzymes in sorghum varieties grouped according to food end‐use properties
Authors: Dicko Mamoudou H , Gruppen Harry , Zouzouho Obou C , Traoré Alfred S , van Berkel Willem JH , Voragen Alphons GJ 
Published: January 2006

AbstractFifty sorghum varieties were screened to determine the effects of germination on levels of starch, α‐amylase, β‐amylase, phenylalanine ammonia lyase (PAL), peroxidase (POX) and polyphenol oxidase (PPO). Germination decreased starch content, with amylose being more degraded than amylopectin. In germinated grain, α‐amylase activity increased several‐fold in all varieties, whereas β‐amylase activity did not increase uniformly and even decreased in some varieties. Activity of the key enzyme in phenolic biosynthesis, PAL, was detected in only half of the varieties before germination but in all of them after germination. PPO was not activated in germinated sorghum grains, whereas POX activity increased up to tenfold in some varieties. Zymography revealed that germination induced de novo synthesis of several POX isoenzymes, among which an anionic POX isoenzyme (pI 3.1) was ubiquitously present. Amylase and phenolic enzyme activities could be correlated with grain and plant agronomic characteristics. The use of sorghum varieties for local dishes such as ‘tô’, ‘dolo’, couscous and thin porridge could be correlated with amylase and phenolic enzyme activities and the contents of their substrates. The biochemical constituents determined are useful markers for selection of varieties for food utilisation with special emphasis on infant porridges. Copyright © 2006 Society of Chemical Industry
Rapid high‐resolution T1 mapping by variable flip angles: Accurate and precise measurements in the presence of radiofrequency field inhomogeneity
Authors: Cheng Hai‐Ling Margaret , Wright Graham A 
Published: January 2006

AbstractRapid 3D mapping of T1 relaxation times is valuable in diverse clinical applications. Recently, the variable flip angle (VFA) spoiled gradient recalled echo approach was shown to be a practical alternative to conventional methods, providing better precision and speed. However, the method is known to be sensitive to transmit field (B1+) inhomogeneity and can result in significant systematic errors in T1 estimates, especially at high field strengths. The main challenge is to improve the accuracy of the VFA approach without sacrificing speed. In this article, the VFA method was optimized for both accuracy and precision by considering the influence of imperfect transmit fields, noise bias, and selection of flip angles. An analytic solution was developed for systematic B1+‐induced T1 errors and allows simple correction of T1 measurements acquired with any imaging parameters. A noise threshold was also identified and provided a guideline for avoiding T1 biases. Finally, it was shown that three flip angles were the most efficient for maintaining accuracy and high precision over large ranges of T1. A rapid B1+ mapping sequence was employed in all phantom experiments and high‐field in vivo brain scans. Experimental results confirmed the theory and validated the accuracy of the proposed method. Magn Reson Med, 2006. © 2006 Wiley‐Liss, Inc.
Effect of the intracellular localization of a Gd‐based imaging probe on the relaxation enhancement of water protons
Authors: Terreno Enzo , Geninatti Crich Simonetta , Belfiore Simona , Biancone Luigi , Cabella Claudia , Esposito Giovanna , Manazza Andrea D. , Aime Silvio 
Published: January 2006

AbstractGd‐HPDO3A has been internalized into rat hepatocarcinoma cells in the cytoplasm (by electroporation) or in intracellular vesicles (by pinocytosis), respectively. In the former case, the observed relaxation rates are likely dependent upon the amount of internalized paramagnetic complex, whereas in the latter case the relaxation enhancement is “quenched” to a plateau value (about 3 s−1) when the entrapped amount of Gd‐chelate is higher than 1 × 1010 Gd/cell. The observed behavior has been accounted in terms of a theoretical treatment based on equations formally derived by Labadie et al. (J Magn Reson B 1994;105:99–102). On this basis, entrapment into intracellular vesicles has been treated as a three‐site water exchange (extracellular/cytoplasm/vesicle compartments), whereas the cell pellets containing the paramagnetic agent spread out in the cytoplasm can be analyzed by a two‐site exchange system. Magn Reson Med, 2006. © 2006 Wiley‐Liss, Inc.
Retrospective gating for mouse cardiac MRI
Authors: Bishop Jonathan , Feintuch Akiva , Bock Nicholas A. , Nieman Brian , Dazai Jun , Davidson Lorinda , Henkelman R. Mark 
Published: January 2006

AbstractCardiac MR imaging in small animals presents some difficulties due to shorter cardiac cycles and smaller dimensions than in human beings, but prospectively gated techniques have been successfully applied. As with human imaging, there may be certain applications in animal imaging for which retrospective gating is preferable to prospective gating. For example, cardiac imaging in multiple mice simultaneously is one such application. In this work we investigate the use of retrospective gating for cardiac imaging in a mouse. Using a three‐dimensional imaging protocol, we show that image quality with retrospective gating is comparable to prospectively gated imaging. We conclude that retrospective gating is applicable for small animal cardiac MRI and show how it can be applied to the problem of cardiac MRI in multiple mice. Magn Reson Med, 2006. © 2006 Wiley‐Liss, Inc.
T1 measurement of 31P metabolites at rest and during steady‐state dynamic exercise using a clinical nuclear magnetic resonance scanner
Authors: Cettolo V. , Piorico C. , Francescato M. P. 
Published: January 2006

AbstractThis article illustrates some problems and possible solutions to determine the apparent spin–lattice relaxation time (T1) of the muscular 31P metabolites at rest and during dynamic steady‐state exercise using a clinical 1.5 T NMR scanner and a surface coil. T1 was first estimated on a phosphates solution (phantom) using four different acquisition protocols, all based on the multiple‐point “progressive saturation” method, and by fitting each data set with two different mathematical models. Subsequently, two of the four protocols and both models were used to estimate T1 both at rest and during exercise on the calf muscles of 10 healthy volunteers. Experimental results obtained on the phantom showed that T1 is greatly affected by the longest nominal explored repetition time (P < 0.001) and by the mathematical model (P < 0.001), ranging from 0.65 ± 0.10 to 8.4 ± 0.8 s. The two acquisition protocols applied on volunteers yielded significantly different T1 (P < 0.001), which were also rather different from the literature values for the same metabolites. Nevertheless, independently of the acquisition protocol and/or the fitting procedure, T1 of all muscular phosphagens did not change statistically from rest to steady‐state aerobic exercise. Magn Reson Med, 2006. © 2006 Wiley‐Liss, Inc.
Navigator gated high temporal resolution tissue phase mapping of myocardial motion
Authors: Jung Bernd , Zaitsev Maxim , Hennig Jürgen , Markl Michael 
Published: January 2006

AbstractData acquisition for phase contrast velocity mapping of myocardial motion is typically based on multiple breath‐held 2D measurements with limited acquisition duration and consequently relatively poor temporal resolution. In order to overcome the limitations of breath‐hold acquisitions, an improved navigator‐guided technique was implemented based on 2 navigator signals within each cardiac cycle in combination with paired acceptance and rejection criteria of successive navigator signals. Respiratory gated phase contrast measurements with 3‐directional velocity encoding were performed in 12 healthy volunteers in basal, midventricular, and apical locations of the left ventricle during free breathing with a temporal resolution of 13.8 ms. Results were compared to standard breath‐hold measurements with a temporal resolution of 69 ms. Data from the high temporal resolution study revealed details in left ventricular motion patterns that were previously not seen in phase contrast measurements and are only known from echocardiography. The proposed navigator gated technique for high temporal resolution velocity mapping is, therefore, highly promising for the detection of local and global motion abnormalities in patients with disturbed left ventricular performance, such as diastolic dysfunction. Magn Reson Med, 2006. © 2006 Wiley‐Liss, Inc.