Hochschule Geisenheim University

Geisenheim, Germany

Hochschule Geisenheim University

Geisenheim, Germany

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Obermeier W.A.,University of Marburg | Lehnert L.W.,University of Marburg | Kammann C.I.,Hochschule Geisenheim University | Muller C.,Justus Liebig University | And 8 more authors.
Nature Climate Change | Year: 2017

The increase in atmospheric greenhouse gas concentrations from anthropogenic activities is the major driver of recent global climate change. The stimulation of plant photosynthesis due to rising atmospheric carbon dioxide concentrations ([CO 2 ]) is widely assumed to increase the net primary productivity (NPP) of C3 plants - the CO 2 fertilization effect (CFE). However, the magnitude and persistence of the CFE under future climates, including more frequent weather extremes, are controversial. Here we use data from 16 years of temperate grassland grown under â € free-air carbon dioxide enrichment' conditions to show that the CFE on above-ground biomass is strongest under local average environmental conditions. The observed CFE was reduced or disappeared under wetter, drier and/or hotter conditions when the forcing variable exceeded its intermediate regime. This is in contrast to predictions of an increased CO 2 fertilization effect under drier and warmer conditions. Such extreme weather conditions are projected to occur more intensely and frequently under future climate scenarios. Consequently, current biogeochemical models might overestimate the future NPP sink capacity of temperate C3 grasslands and hence underestimate future atmospheric [CO 2 ] increase. © 2017 Macmillan Publishers Limited, part of Springer Nature. All rights reserved.

Kalili K.M.,Stellenbosch University | Vestner J.,Stellenbosch University | Vestner J.,Hochschule Geisenheim University | Stander M.A.,Stellenbosch University | De Villiers A.,Stellenbosch University
Analytical Chemistry | Year: 2013

Despite the significant importance of tannins in viticulture and enology, relatively little is known about the detailed chemical composition of these molecules. This is due to challenges associated with the accurate analytical determination of the highly structurally diverse proanthocyanidins which comprise tannins. In this contribution, we address this limitation by demonstrating how online comprehensive two-dimensional liquid chromatography (LC × LC) coupled to high resolution mass spectrometry (HR-MS) can be exploited as a powerful analytical approach for the detailed characterization of grape seed tannins. Hydrophilic interaction chromatography (HILIC) and reversed-phase liquid chromatography (RP-LC) were employed in the two dimensions to provide complementary information in terms of separation according to hydrophilicity and hydrophobicity, respectively. Online coupling of HILIC × RP-LC with fluorescence detection and electrospray ionization MS delivered high resolution analysis in a practical analysis time, while allowing selective detection and facilitating compound identification. Time-of-flight (TOF) MS provided high acquisition rates and sensitivity coupled to accurate mass information, which allowed detection of procyanidins up to a degree of polymerization (DP) of 16 and a degree of galloylation up to 8 in a red grape seed extract. This analytical methodology promises to shed new light on these important grape constituents and potentially on their evolution during wine production. © 2013 American Chemical Society.

Tramontini S.,Plant Health Unit PLH | Tramontini S.,University of Turin | Doring J.,Hochschule Geisenheim University | Vitali M.,University of Turin | And 3 more authors.
Functional Plant Biology | Year: 2014

Grapevine (Vitis vinifera L.) expresses different responses to water stress, depending not only on genotype, but also on the influence of vineyard growing conditions or seasonality. Our aim was to analyse the effects on drought response of two grapevine cultivars growing on two soils, one water draining (WD) containing sand 80% volume and the other water retaining (WR), with no sand. Under these two different water-holding capacities Syrah, displaying a near-anisohydric response to water stress, and Cabernet Sauvignon (on the contrary, near-isohydric) were submitted to water stress in a pot trial. Xylem embolism contributed to plant adaptation to soil water deprivation: in both cultivars during late phases of water stress, however, in Syrah, already at moderate early stress levels. By contrast, Syrah showed a less effective stomatal control of drought than Cabernet Sauvignon. The abscisic acid (ABA) influenced tightly the stomatal conductance of Cabernet Sauvignon on both pot soils. In the near-anisohydric variety Syrah an ABA-related stomatal closure was induced in WR soil to maintain high levels of water potential, showing that a soil-related hormonal root-to-shoot signal causing stomatal closure superimposes on the putatively variety-induced anisohydric response to water stress. © CSIRO 2014.

Jeffery S.,Harper Adams University College | Verheijen F.G.A.,University of Aveiro | Kammann C.,Hochschule Geisenheim University | Abalos D.,Wageningen University
Soil Biology and Biochemistry | Year: 2016

Methane (CH4) emissions have increased by more than 150% since 1750, with agriculture being the major source. Further increases are predicted as permafrost regions start thawing, and rice and ruminant animal production expand. Biochar is posited to increase crop productivity while mitigating climate change by sequestering carbon in soils and by influencing greenhouse gas fluxes. There is a growing understanding of biochar effects on carbon dioxide and nitrous oxide fluxes from soil. However, little is known regarding the effects on net methane exchange, with single studies often reporting contradictory results. Here we aim to reconcile the disparate effects of biochar application to soil in agricultural systems on CH4 fluxes into a single interpretive framework by quantitative meta-analysis. This study shows that biochar has the potential to mitigate CH4 emissions from soils, particularly from flooded (i.e. paddy) fields (Hedge's d = −0.87) and/or acidic soils (Hedge's d = −1.56) where periods of flooding are part of the management regime. Conversely, addition of biochar to soils that do not have periods of flooding (Hedge's d = 0.65), in particular when neutral or alkaline (Hedge's d = 1.17 and 0.44, respectively), may have the potential to decrease the CH4 sink strength of those soils. Global methane fluxes are net positive as rice cultivation is a much larger source of CH4 than the sink contribution of upland soils. Therefore, this meta-study reveals that biochar use may have the potential to reduce atmospheric CH4 emissions from agricultural flooded soils on a global scale. © 2016 Elsevier Ltd

Galidevara S.,Andhra University | Reineke A.,Hochschule Geisenheim University | Koduru U.D.,Andhra University
Journal of Invertebrate Pathology | Year: 2016

The entomopathogenic fungus Beauveria bassiana (Bals.) Vuillemin is commercially available as a bio insecticide. The expression of three genes previously identified to have a role in pathogenicity in in vitro studies was validated in vivo in three lepidopteran insects infected with B. bassiana. Expression of all three genes was observed in all the tested insects starting from 48 or 72 h to 10 d post infection corroborating their role in pathogenicity. We suggest that it is essential to test the expression of putative pathogenicity genes both in vitro and in vivo to understand their role in different insect species. © 2016 Elsevier Inc.

Szolnoki G.,Hochschule Geisenheim University | Hoffmann D.,Forschungsanstalt Geisenheim University
International Journal of Wine Business Research | Year: 2014

Purpose: The purpose of this study is to test the segmentation based on the usage of sales channels and to compare the segments with each other in terms of socio-demographic and behavioural characteristics. Design/methodology/approach: This study was conducted using representative data collected in Germany through a face-to-face interview. 2,000 German consumers answered questions towards the usage of different sales channels when purchasing wine as well as socio-demographic and other behavioural questions. A hierarchical cluster analysis was run, to classify the respondents into segments. Findings: The results illustrate the usefulness of this kind of segmentation and show significant differences between the six consumer groups: discount-customers, food-retail-customers, supermarket-customers, cellar-door-customers, wine-store-customers and multichannel-customers. These segments differ in their socio-demographic as well as in their behavioural structure. Furthermore, the six segments could be split into two groups depending on their average purchase value: a basic group and a premium group. Practical implications: This segmentation provides an analysing tool for the German retailers, which is able to identify the loyal and potential consumers of the different sales channels. Originality/value: This segmentation was conducted using the purchase activity of German consumers in different sales channels. This segmentation approach has been never used to identify, describe and classify wine consumers. © Emerald Group Publishing Limited.

Buckel I.,Schrodinger | Molitor D.,Center De Recherche Public Gabriel Lippmann | Liermann J.C.,Johannes Gutenberg University Mainz | Sandjo L.P.,Johannes Gutenberg University Mainz | And 3 more authors.
Phytochemistry | Year: 2013

Phenguignardic acid was recently described as a phytotoxic secondary metabolite from submerged cultures of the grape black rot fungus Guignardia bidwellii. Since the production rate of this natural product in submerged culture is very low, fermentation optimisation was carried out. The optimisation of cultivation conditions led to the identification of seven secondary metabolites, structurally related to guignardic acid, a known secondary metabolite from Guignardia species containing a dioxolanone moiety. All metabolites presented here have not been described to date and are presumably biosynthesised via deamination products of amino acids, such as phenylalanine, valine, tyrosine, and alanine. Four of the seven compounds showed phytotoxic activity. Based on the structures determined by NMR spectroscopy a preliminary structure activity relationship indicated a free carboxyl group as presumably required for the phytotoxic activity. © 2012 Elsevier Ltd. All rights reserved.

Schmidt D.,Hochschule Geisenheim University | Velten K.,Hochschule Geisenheim University
Food and Bioproducts Processing | Year: 2016

A detailed understanding of mixing and homogenization during food processing is essential for process control and optimization, but often hard to achieve on industrial scales. We used 3D CFD simulations to analyze bubble flow induced mixing of yeast nutrients in industrial scale wine fermentations for different vessel geometries. Employing boundary conditions resembling the common set-up of bubble column simulations, an Eulerian multiphase model was experimentally validated and then used to describe the gas–liquid flow. Mixing behavior was evaluated based on passive tracer distributions implied by three different dosage locations. Average homogenization times ranged between (71 ± 8) s and (100 ± 9) s for most active fermentations, with significant differences depending on tank geometry. Mixing times were approximately twice as long in early stages of fermentation. For the simulation scenarios investigated, CO2 bubble-induced flow during active fermentation is shown to effectively prevent unwanted nutrient inhomogeneities. © 2016 Institution of Chemical Engineers

Friedel M.,Hochschule Geisenheim University | Patz C.-D.,Hochschule Geisenheim University | Dietrich H.,Hochschule Geisenheim University
Food Chemistry | Year: 2013

For more than a decade, Fourier-transform infrared (FTIR) spectroscopy combined with partial least squares (PLS) regression has been used as a fast and reliable method for simultaneous estimation of multiple parameters in wine. In this study, different FTIR instruments (single bounce attenuated total reflection, transmission with variable and defined pathlength) and different variable selection techniques (full spectrum PLS, genetic algorithm PLS, interval PLS, principal variable PLS) were compared on an identical sample set of international wines and ten wine parameters. Results suggest that the single bounce attenuated total reflection technique is well suited for the analysis of ethanol, relative density and sugars, but less accurate in the analysis of organic acid content. The transmission instrument with variable pathlength shows good validation results for the analysis of organic acids, but less accurate results for the analysis of ethanol and relative density as compared to the other instruments. The transmission instrument with defined pathlength was well suited for the analysis for all parameters investigated in this study. Variable selection improved model robustness and calibration results, with genetic algorithm PLS being the most effective technique. © 2013 Elsevier Ltd. All rights reserved.

Spinarova S.,Hochschule Geisenheim University | Hendriks L.,Hochschule Geisenheim University
Acta Horticulturae | Year: 2015

Understanding plant responses to water deficiency has become globally one of the most challenging tasks in crop management, plant stress physiology and breeding technologies. It has stimulated the demand of growers, breeders and researchers of ornamental plants for efficient and reliable methods to detect and quantify water stress before the plants will be damaged irreversibly. This paper summarizes our experience and investigations using gas exchange technology, ultrasonic acoustic emission (UAE) technique and thermal imaging, as applied in horticulture research. In projects testing drought tolerance of bedding plants or monitoring water status of cut flowers during the post harvest life it could be concluded: 1) gas exchange and UAE measurements under stress conditions provide especially robust data for cultivar screening, 2) thermal imaging proves best for application in irrigation scheduling regarding the easy handling and good reliability of interpretations and 3) UAE profiles in short-term stress tests appear as meaningful indicators for prediction of cut flowers' longevity.

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