Showing papers by "University of Hohenheim published in 2008"

Organo-mineral associations in temperate soils: Integrating biology, mineralogy, and organic matter chemistry

Abstract: We summarize progress with respect to (1) different approaches to isolate, extract, and quantify organo-mineral compounds from soils, (2) types of mineral surfaces and associated interactions, (3) the distribution and function of soil biota at organo-mineral surfaces, (4) the distribution and content of organo-mineral associations, and (5) the factors controlling the turnover of organic matter (OM) in organo-mineral associations from temperate soils. Physical fractionation achieves a rough separation between plant residues and mineral-associated OM, which makes density or particle-size fractionation a useful pretreatment for further differentiation of functional fractions. A part of the OM in organo-mineral associations resists different chemical treatments, but the data obtained cannot readily be compared among each other, and more research is necessary on the processes underlying resistance to treatments for certain OM components. Studies using physical-fractionation procedures followed by soil-microbiological analyses revealed that organo-mineral associations spatially isolate C sources from soil biota, making quantity and quality of OM in microhabitats an important factor controlling community composition. The distribution and activity of soil microorganisms at organo-mineral surfaces can additionally be modified by faunal activities. Composition of OM in organo-mineral associations is highly variable, with loamy soils having generally a higher contribution of polysaccharides, whereas mineral-associated OM in sandy soils is often more aliphatic. Though highly reactive towards Fe oxide surfaces, lignin and phenolic components are usually depleted in organo-mineral associations. Charred OM associated with the mineral surface contributes to a higher aromaticity in heavy fractions. The relative proportion of OC bound in organo-mineral fractions increases with soil depth. Likewise does the strength of the bonding. Organic molecules sorbed to the mineral surfaces or precipitated by Al are effectively stabilized, indicated by reduced susceptibility towards oxidative attack, higher thermal stability, and lower bioavailability. At higher surface loading, organic C is much better bioavailable, also indicated by little 14C age. In the subsurface horizons of the soils investigated in this study, Fe oxides seem to be the most important sorbents, whereas phyllosilicate surfaces may be comparatively more important in topsoils. Specific surface area of soil minerals is not always a good predictor for C-stabilization potentials because surface coverage is discontinuous. Recalcitrance and accessibility/aggregation seem to determine the turnover dynamics in fast and intermediate cycling OM pools, but for long-term OC preservation the interactions with mineral surfaces, and especially with Fe oxide surfaces, are a major control in all soils investigated here.

BLUP for phenotypic selection in plant breeding and variety testing

Abstract: Best linear unbiased prediction (BLUP) is a standard method for estimating random effects of a mixed model. This method was originally developed in animal breeding for estimation of breeding values and is now widely used in many areas of research. It does not, however, seem to have gained the same popularity in plant breeding and variety testing as it has in animal breeding. In plants, application of mixed models with random genetic effects has up until recently been mainly restricted to the estimation of genetic and non- genetic components of variance, whereas estimation of genotypic values is mostly based on a model with fixed effects. This paper reviews recent developments in the application of BLUP in plant breeding and variety testing. These include the use of pedigree information to model and exploit genetic correlation among relatives and the use of flexible variance-covariance structures for genotype-by-environment interaction. We demonstrate that BLUP has good predictive accuracy compared to other procedures. While pedi- gree information is often included via the so-called numerator relationship matrix ðAÞ, we stress that it is frequently straightforward to exploit the same infor- mation by a simple mixed model without explicit reference to the A-matrix.

Statistical Analysis of Yield Trials by AMMI and GGE: Further Considerations

Abstract: Recent review articles in this journal have compared the relative merits of two prominent statistical models for analyzing yield-trial data: Additive main effects and multiplicative interaction (AMMI) and genotype main effects and genotype × environment interaction (GGE). This review addresses more than 20 issues that require clarification after controversial statements and contrasting conclusions have appeared in those recent reviews. The AMMI2 mega-environment display incorporates more of the genotype main effect and captures more of the genotype × environment (GE) interaction than does GGE2, thereby displaying the which-won-where pattern more accurately for complex datasets. When the GE interaction is captured well by one principal component, the AMMI1 display of genotype nominal yields describes winning genotypes and adaptive responses more simply and clearly than the GGE2 biplot. For genotype evaluation within a single mega-environment, a simple scatterplot of mean and stability is more straightforward than the mean vs. stability view of a GGE2 biplot. Diagnosing the most predictively accurate member of a model family is vital for either AMMI or GGE, both for gaining accuracy and delineating mega-environments.

Quercetin: potentials in the prevention and therapy of disease.

Abstract: Purpose of reviewQuercetin is discussed since several decades as a multipotent bioflavonoid with great potential for the prevention and treatment of disease. In the current review, we present the most recent findings on quercetin with regard to the pharmacology, the in-vitro and in-vivo effects in d

Nonalcoholic Fatty Liver Disease in Humans Is Associated with Increased Plasma Endotoxin and Plasminogen Activator Inhibitor 1 Concentrations and with Fructose Intake

Abstract: Results of animal experiments suggest that consumption of refined carbohydrates (e.g. fructose) can result in small intestinal bacterial overgrowth and increased intestinal permeability, thereby contributing to the development of nonalcoholic fatty liver disease (NAFLD). Furthermore, increased plasminogen activator inhibitor (PAI)-1 has been linked to liver damage of various etiologies (e.g. alcohol, endotoxin, nonalcoholic). The aim of the present pilot study was to compare dietary factors, endotoxin, and PAI-1 concentrations between NAFLD patients and controls. We assessed the dietary intake of 12 patients with NAFLD and 6 control subjects. Plasma endotoxin and PAI-1 concentrations as well as hepatic expression of PAI-1 and toll-like receptor (TLR) 4 mRNA were determined. Despite similar total energy, fat, protein, and carbohydrate intakes, patients with NAFLD consumed significantly more fructose than controls. Endotoxin and PAI-1 plasma concentrations as well as hepatic TLR4 and PAI-1 mRNA expression of NAFLD patients were significantly higher than in controls. The plasma PAI-1 concentration was positively correlated with the plasma endotoxin concentration (Spearman r = 0.83; P < 0.005) and hepatic TLR4 mRNA expression (Spearman r = 0.54; P < 0.05). Hepatic mRNA expression of PAI-1 was positively associated with dietary intakes of carbohydrates (Spearman r = 0.67; P < 0.01), glucose (Spearman r = 0.58; P < 0.01), fructose (Spearman r = 0.58; P < 0.01), and sucrose (Spearman r = 0.70; P < 0.01). In conclusion, our results suggest that dietary fructose intake, increased intestinal translocation of bacterial endotoxin, and PAI-1 may contribute to the development of NAFLD in humans.

Developments in breeding cereals for organic agriculture

Abstract: The need for increased sustainability of performance in cereal varieties, particularly in organic agriculture (OA), is limited by the lack of varieties adapted to organic conditions. Here, the needs for breeding are reviewed in the context of three major marketing types, global, regional, local, in European OA. Currently, the effort is determined, partly, by the outcomes from trials that compare varieties under OA and CA (conventional agriculture) conditions. The differences are sufficiently large and important to warrant an increase in appropriate breeding. The wide range of environments within OA and between years, underlines the need to try to select for specific adaptation in target environments. The difficulty of doing so can be helped by decentralised breeding with farmer participation and the use of crops buffered by variety mixtures or populations. Varieties for OA need efficient nutrient uptake and use and weed competition. These and other characters need to be considered in relation to the OA cropping system over the whole rotation. Positive interactions are needed, such as early crop vigour for nutrient uptake, weed competition and disease resistance. Incorporation of all characteristics into the crop can be helped by diversification within the crop, allowing complementation and compensation among plants. Although the problems of breeding cereals for organic farming systems are large, there is encouraging progress. This lies in applications of ecology to organic crop production, innovations in plant sciences, and the realisation that such progress is central to both OA and CA, because of climate change and the increasing costs of fossil fuels.

Plant fructans in stress environments: emerging concepts and future prospects

Abstract: Plants are sessile and sensitive organisms known to possess various regulatory mechanisms for defending themselves under stress environments. Fructans are fructose-based polymers synthesized from sucrose by fructosyltransferases (FTs). They have been increasingly recognized as protective agents against abiotic stresses. Using model membranes, numerous in vitro studies have demonstrated that fructans can stabilize membranes by direct H-bonding to the phosphate and choline groups of membrane lipids, resulting in a reduced water outflow from the dry membranes. Inulin-type fructans are flexible random-coiled structures that can adopt many conformations, allowing them to insert deeply within the membranes. The devitrification temperature (Tg) can be adjusted by their varying molecular weights. In addition, above Tg their low crystallization rates ensure prolonged membrane protection. Supporting, in vivo studies with transgenic plants expressing FTs showed fructan accumulation and an associated improvement in freezing and/or chilling tolerance. The water-soluble nature of fructans may allow their rapid adaptation as cryoprotectants in order to give optimal membrane protection. One of the emerging concepts for delivering vacuolar fructans to the extracellular space for protecting the plasma membrane is vesicle-mediated, tonoplast-derived exocytosis. It should, however, be noted that natural stress tolerance is a very complex process that cannot be explained by the action of a single molecule or mechanism.

Sucrose, sucrosyl oligosaccharides, and oxidative stress: scavenging and salvaging?

Abstract: In nature, no single plant completes its life cycle without encountering environmental stress. When plant cells surpass stress threshold stimuli, chemically reactive oxygen species (ROS) are generated that can cause oxidative damage or act as signals. Plants have developed numerous ROS-scavenging systems to minimize the cytotoxic effects of ROS. The role of sucrosyl oligosaccharides (SOS), including fructans and the raffinose family oligosaccharides (RFOs), is well established during stress physiology. They are believed to act as important membrane protectors in planta. So far a putative role for sucrose and SOS during oxidative stress has largely been neglected, as has the contribution of the vacuolar compartment. Recent studies suggest a link between SOS and oxidative defence and/or scavenging. SOS might be involved in stabilizing membrane-associated peroxidases and NADPH oxidases, and SOS-derived radicals might fulfil an intermediate role in oxido-reduction reactions taking place in the vicinity of membranes. Here, these emerging features are discussed and perspectives for future research are provided.

Comparison of mixed-model approaches for association mapping.

Abstract: Association-mapping methods promise to overcome the limitations of linkage-mapping methods. The main objectives of this study were to (i) evaluate various methods for association mapping in the autogamous species wheat using an empirical data set, (ii) determine a marker-based kinship matrix using a restricted maximum-likelihood (REML) estimate of the probability of two alleles at the same locus being identical in state but not identical by descent, and (iii) compare the results of association-mapping approaches based on adjusted entry means (two-step approaches) with the results of approaches in which the phenotypic data analysis and the association analysis were performed in one step (one-step approaches). On the basis of the phenotypic and genotypic data of 303 soft winter wheat ( Triticum aestivum L.) inbreds, various association-mapping methods were evaluated. Spearman's rank correlation between P -values calculated on the basis of one- and two-stage association-mapping methods ranged from 0.63 to 0.93. The mixed-model association-mapping approaches using a kinship matrix estimated by REML are more appropriate for association mapping than the recently proposed QK method with respect to (i) the adherence to the nominal α-level and (ii) the adjusted power for detection of quantitative trait loci. Furthermore, we showed that our data set could be analyzed by using two-step approaches of the proposed association-mapping method without substantially increasing the empirical type I error rate in comparison to the corresponding one-step approaches.

Nitrogen rhizodeposition in agricultural crops: Methods, estimates and future prospects

Abstract: The objective of the present review was to present the current knowledge on nitrogen (N) rhizodeposition, including techniques for 15N labelling of agricultural plants, amounts of N rhizodeposition and its fate in soil. Rhizodeposition is the process of release of organic and inorganic compounds from living plant roots. It is often quantified in terms of carbon (C) and less often as N derived from rhizodeposition (NdfR). Rhizodeposition of N can be estimated by labelling plants with 15N and following its fate in soil. Most methods used for labelling plants with 15N can only be applied after appearance of the first leaf and only allow pulse or multiple pulse labelling. Only the split-root technique and the application of gaseous 15N allow continuous labelling. All methods available at present have their flaccidities mostly due to the fact that the application of N is not following its physiological pathway of assimilation or by using artificial conditions. In the studies reviewed, amounts of N rhizodeposits ranged from 4% to 71% of total assimilated plant N. In legumes the median was 16% and in cereals it was 14%. Rhizodeposits were 15–96% of the below-ground plant biomass (BGP). In legumes the median was 73% and in cereal it was 57%. The high variability of these results shows the need for more investigations on N rhizodeposition looking especially on the factors influencing the amounts released in different plant species under field conditions.

Estimation of the impact of oil palm plantation establishment on greenhouse gas balance

Abstract: Estimates of emissions indicate that if tropical grassland is rehabilitated by oil palm plantations, carbon fixation in plantation biomass and soil organic matter not only neutralises emissions caused by grassland conversion, but also results in the net removal of about 135 Mg carbon dioxide per hectare from the atmosphere. In contrast, the emission from forest conversion clearly exceeds the potential carbon fixation of oil palm plantings. Forest conversion on mineral soils to promote continued oil palm mono cropping causes a net release of approximately 650 Mg carbon dioxide equivalents per hectare, while the emission from peat forest conversion is even higher due to the decomposition of drained peat and the resulting emission of carbon oxide and nitrous oxide. The conversion of one hectare of forest on peat releases over 1,300 Mg carbon dioxide equivalents during the first 25-year cycle of oil palm growth. Depending on the peat depth, continuous decomposition augments the emission with each additional cycle at a magnitude of 800 Mg carbon dioxide equivalents per hectare. The creation of ‘flexibility mechanisms’ such as the clean development mechanism and emission trading in the Kyoto Protocol could incorporate plantations as carbon sinks in the effort to meet emission targets. Thus, for the oil palm industry, grassland rehabilitation is an option to preserve natural forest, avoid emissions and, if the sequestered carbon becomes tradable, an opportunity to generate additional revenue.

Belowground net primary productivity and biomass allocation of a grassland in Inner Mongolia is affected by grazing intensity

Abstract: The root system of permanent grasslands is of outstanding importance for resource acquisition. Particularly under semi-arid conditions, the acquisition of water and nutrients is highly variable during the vegetation growth period and between years. Additionally, grazing is repeatedly disturbing the functional equilibrium between the root system and the transpiring leaf canopy. However, very few data is available considering grazing effects on belowground net primary productivity (BNPP) and root-shoot dry mass allocation in natural grassland systems. We hypothesise that grazing significantly reduces BNPP due to carbon reallocation to shoot growth. Root biomass and BNPP were estimated by soil coring in 2004, 2005 and 2006 and from ingrowth cores in 2005 and 2006 at one site which has been protected from grazing since 1979 (UG79), at one winter grazing (WG), and one heavily grazed (HG) site. BNPP was estimated from the summation of significant increments of total and live root biomass and from accumulated root biomass of ingrowth cores. Belowground biomass varied from 1,490–2,670 g m−2 and was significantly lower under heavy grazing than at site UG79. Root turnover varied from 0.23 to 0.33 year−1 and was not significantly different between sites. Heavy grazing significantly decreased live root biomass and BNPP compared to site UG79. Taking BNPP estimates from live root biomass dynamics and ingrowth cores as the most reliable values, the portion of dry mass allocated belowground relative to total net primary productivity (BNPP/NPP) varied between 0.50–0.66 and was reduced under heavy grazing in 2005, but not in 2006. The positive correlation between cumulative root length density of ingrowth cores and leaf dry matter suggests that the ingrowth core method is suitable for studying BNPP in this semi-arid steppe system. Grazing effects on BNPP and BNPP/NPP should be considered in regional carbon models and estimates of belowground nutrient cycling.

Protein concentrate from Jatropha curcas screw-pressed seed cake and toxic and antinutritional factors in protein concentrate

Abstract: BACKGROUND: Jatropha curcas seeds are highly toxic to livestock The presence of phorbol esters and antinutrients such as trypsin inhibitor, lectin and phytate and the high level of shells in the seed cake prevent its use in animal diets Using the principle of isoelectric precipitation, the conditions for preparation of the protein concentrate from oil-containing seed cake and defatted seed cake were optimised and the contents of phorbol esters and antinutrients were determined RESULTS: The recovery of protein concentrate was highest when the proteins from the seed cakes were solubilised at pH 11 for 1 h at 60 ◦ C and the precipitation of these proteins was done by lowering the pH to 4 Under these conditions, over 53% of the total proteins present in the seed cakes were recovered in the protein concentrates The protein contents in the protein concentrates obtained from the oil-containing seed cake and defatted seed cake were 760 and 820 g kg −1 respectively Substantial amounts of phorbol esters were present in the protein concentrates (086–148 mg g −1 ) Trypsin inhibitor was present at an approximately tenfold higher level in the protein concentrates than in the seed cakes Lectin and phytate were also present at high levels, but their levels were lower than in the seed cakes Tannins were present in negligible amounts CONCLUSION: To make the protein concentrate from Jatropha seed cake fit for use as an ingredient in livestock feed, phorbol esters must be removed and trypsin inhibitor and lectin inactivated by heat treatment The adverse effects of phytate could be mitigated by addition of phytase in the diet  2008 Society of Chemical Industry

Tree rings and ice cores reveal C-14 calibration uncertainties during the Younger Dryas

Abstract: The Younger Dryas interval during the Last Glacial Termination was an abrupt return to glacial-like conditions punctuating the transition to a warmer, interglacial climate. Despite recent advances in the layer counting of ice-core records of the termination, the timing and length of the Younger Dryas remain controversial. Also, a steep rise in the concentration of atmospheric radiocarbon at the onset of the interval, recorded primarily in the Cariaco Basin, has been difficult to reconcile with simulations of the Younger Dryas carbon cycle. Here we discuss a radiocarbon chronology from a tree-ring record covering the Late Glacial period that has not been absolutely dated. We correlate the chronology to ice-core timescales using the common cosmic production signal in tree-ring 14C and ice-core 10Be concentrations. The results of this correlation suggest that the Cariaco record may be biased by changes in the concentration of radiocarbon in the upper ocean during the early phase of the Younger Dryas climate reversal in the Cariaco basin. This bias in the marine record may also affect the accuracy of a widely used radiocarbon calibration curve over this interval. Our tree-ring-based radiocarbon record is easily reconciled with simulated production rates and carbon-cycle changes associated with reduced ocean ventilation during the Younger Dryas. Attaching a ‘floating’ tree-ring chronology to ice core records that cover the abrupt Younger Dryas cold interval during the last glacial termination provides a better estimate of the onset and duration of the radiocarbon anomaly. The chronology suggests that marine records may be biased by changes in the concentration of radiocarbon in the ocean, which may affect the accuracy of a popular radiocarbon calibration program during this interval.

Regulation of proteasome-mediated protein degradation during oxidative stress and aging.

Abstract: Protein degradation is a physiological process required to maintain cellular functions. There are distinct proteolytic systems for different physiological tasks under changing environmental and pathophysiological conditions. The proteasome is responsible for the removal of oxidatively damaged proteins in the cytosol and nucleus. It has been demonstrated that proteasomal degradation increases due to mild oxidation, whereas at higher oxidant levels proteasomal degradation decreases. Moreover, the proteasome itself is affected by oxidative stress to varying degrees. The ATP-stimulated 26S proteasome is sensitive to oxidative stress, whereas the 20S form seems to be resistant. Non-degradable protein aggregates and cross-linked proteins are able to bind to the proteasome, which makes the degradation of other misfolded and damaged proteins less efficient. Consequently, inhibition of the proteasome has dramatic effects on cellular aging processes and cell viability. It seems likely that during oxidative stress cells are able to keep the nuclear protein pool free of damage, while cytosolic proteins may accumulate. This is because of the high proteasome content in the nucleus, which protects the nucleus from the formation and accumulation of non-degradable proteins. In this review we highlight the regulation of the proteasome during oxidative stress and aging.

Soil-carbon preservation through habitat constraints and biological limitations on decomposer activity

Abstract: We review recent experimental results on the role of soil biota in stabilizing or destabilizing soil organic matter (SOM). Specifically, we analyze how the differential substrate utilization of the various decomposer organisms contributes to a decorrelation of chemical stability, residence time, and carbon (C) age of organic substrates. Along soil depth profiles, a mismatch of C allocation and abundance of decomposer organisms is consistently observed, revealing that a relevant proportion of soil C is not subjected to efficient decomposition. Results from recent field and laboratory experiments suggest that (1) bacterial utilization of labile carbon compounds is limited by short-distance transport processes and, therefore, can take place deep in the soil under conditions of effective local diffusion or convection. In contrast, (2) fungal utilization of phenolic substrates, including lignin, appears to be restricted to the upper soil layer due to the requirement for oxygen of the enzymatic reaction involved. (3) Carbon of any age is utilized by soil microorganisms, and microbial C is recycled in the microbial food web. Due to stoichiometric requirements of their metabolism, (4) soil animals tend to reduce the C concentration of SOM disproportionally, until it reaches a threshold level. The reviewed investigations provide new and quantitative evidence that different soil C pools underlie divergent biological constraints of decomposition. The specialization of decomposers towards different substrates and microhabitats leads to a relatively longer persistence of virtually all kinds of organic substrates in the nonpreferred soil spaces. We therefore propose to direct future research explicitly towards such biologically nonpreferred areas where decomposition rates are slow, or where decomposition is frequently interrupted, in order to assess the potential for long-term preservation of C in the soil.

Ruminal biohydrogenation as affected by tannins in vitro

Abstract: The aim of the present work was to study the effects of tannins from carob (CT; Ceratonia siliqua), acacia leaves (AT; Acacia cyanophylla) and quebracho (QT; Schinopsis lorentzii) on ruminal biohydrogenation in vitro. The tannins extracted from CT, AT and QT were incubated for 12 h in glass syringes in cow buffered ruminal fluid (BRF) with hay or hay plus concentrate as a substrate. Within each feed, three concentrations of tannins were used (0.0, 0.6 and 1.0 mg/ml BRF). The branched-chain volatile fatty acids, the branched-chain fatty acids and the microbial protein concentration were reduced (P < 0.05) by tannins. In the tannin-containing fermenters, vaccenic acid was accumulated (+23 %, P < 0.01) while stearic acid was reduced ( - 16 %, P < 0.0005). The concentration of total conjugated linoleic acid (CLA) isomers in the BRF was not affected by tannins. The assay on linoleic acid isomerase (LA-I) showed that the enzyme activity (nmol CLA produced/min per mg protein) was unaffected by the inclusion of tannins in the fermenters. However, the CLA produced by LA-I (nmol/ml per min) was lower in the presence of tannins. These results suggest that tannins reduce ruminal biohydrogenation through the inhibition of the activity of ruminal micro-organisms.

Lycopene Inhibits Disease Progression in Patients with Benign Prostate Hyperplasia

Abstract: Lycopene is a promising nutritional component for chemoprevention of prostate cancer (PCa). A possibly beneficial role of lycopene in patients diagnosed with benign prostate hyperplasia (BPH), who are at increased risk of developing PCa, has been suggested, although clinical data are lacking. Therefore, this pilot study aimed to investigate the effects of lycopene supplementation in elderly men diagnosed with BPH. A total of 40 patients with histologically proven BPH free of PCa were randomized to receive either lycopene at a dose of 15 mg/d or placebo for 6 mo. The effects of the intervention on carotenoid status, clinical diagnostic markers of prostate proliferation, and symptoms of the disease were assessed. The primary endpoint of the study was the inhibition or reduction of increased serum prostate-specific antigen (PSA) levels. The 6-mo lycopene supplementation decreased PSA levels in men (P < 0.05), whereas there was no change in the placebo group. The plasma lycopene concentration increased in the group taking lycopene (P < 0.0001) but other plasma carotenoids were not affected. Whereas progression of prostate enlargement occurred in the placebo group as assessed by trans-rectal ultrasonography (P < 0.05) and digital rectal examination (P < 0.01), the prostate did not enlarge in the lycopene group. Symptoms of the disease, as assessed via the International Prostate Symptom Score questionnaire, were improved in both groups with a significantly greater effect in men taking lycopene supplements. In conclusion, lycopene inhibited progression of BPH.