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Berlin Brandenburg

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  • Wiley Online Library  (24)
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  • 1
    In: Molecular Ecology, February 2014, Vol.23(3), pp.733-746
    Description: Interactions between arbuscular mycorrhizal fungal () species cocolonizing the same host plant are still little understood in spite of major ecological significance of mycorrhizal symbiosis and widespread occurrence of these fungi in communities rather than alone. Furthermore, shifting the composition of communities has demonstrated consequences for the provision of symbiotic benefits to the host as well as for the qualities of ecosystem services. Therefore, here we addressed the nature and strength of interactions between three different species in all possible two‐species combinations on a gradient of inoculation densities. Fungal communities were established in pots with plants, and their composition was assessed with taxon‐specific real‐time markers. Nature of interactions between the fungi was varying from competition to facilitation and was influenced by both the identity and relative abundance of the coinoculated fungi. Plants coinoculated with and grew bigger and contained more phosphorus than with any of these two fungi separately, although these fungi obviously competed for root colonization. On the other hand, plants coinoculated with and , which facilitated each other's root colonization, grew smaller than with any of these fungi separately. Our results point to as yet little understood complexity of interactions in plant‐associated symbiotic fungal communities, which, depending on their composition, can induce significant changes in plant host growth and/or phosphorus acquisition in either direction.
    Keywords: Barrel Medic ; Claroideoglomus Claroideum ; Functional Complementarity ; Gigaspora Margarita ; Quantitative Real‐Time ; Rhizophagus Irregularis
    ISSN: 0962-1083
    E-ISSN: 1365-294X
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  • 2
    In: New Phytologist, January 2013, Vol.197(1), pp.186-193
    Description: The objective of this study was to investigate the isotopic composition of oxygen bound to phosphate (δ18O‐PO4) in different phosphorus (P) pools in plant leaves. As a model plant we used soybean (Glycine max cv Toliman) grown in the presence of ample P in hydroponic cultures. The leaf blades were extracted with 0.3 M trichloroacetic acid (TCA) and with 10 M nitric acid. These extractions allowed measurement of the TCA‐soluble reactive P (TCA P) that is rapidly cycled within the cell and the total leaf P. The difference between total leaf P and TCA P yielded the structural P which includes organic P compounds not extractable by TCA. P uptake and its translocation and transformation within the soybean plants lead to an 18O enrichment of TCA P (δ18O‐PO4 between 16.9 and 27.5‰) and structural P (δ18O‐PO4 between 42.6 and 68.0 ‰) compared with 12.4‰ in the phosphate in the nutrient solution. δ18O values of phosphate extracted from soybean leaves grown under optimal conditions are greater than the δ18O‐PO4 values of the provided P source. Furthermore, the δ18O‐PO4 of TCA P seems to be controlled by the δ18O of leaf water and the activity of inorganic pyrophosphatase or other pyrophosphatases.
    Keywords: Acid Phosphatase ; Δo Of Leaf Water ; Δo‐ ; Soybean ; Structural P ; Tca‐Soluble Reactive P P
    ISSN: 0028-646X
    E-ISSN: 1469-8137
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  • 3
    In: Journal of Ecology, November 2018, Vol.106(6), pp.2332-2343
    Description: The extent to which plants can reduce nutrient concentrations in soil and thereby compete with others may increase with nutrient mobility. Hyphae of arbuscular mycorrhizal fungi (AMF) can extend the soil volume from which plants acquire phosphorus (P), thus increasing competition for these resources with neighbours. In this study, we tested whether the suppression of hyphal interconnections between neighbour plants mitigates their competitive interactions and consequently affects plant community structure. We used custom‐built microcosms that used a wire system to suppress the development of a common mycorrhizal network (CMN) between plant neighbours. We applied this CMN treatment to plants without neighbours (competition‐free controls), with conspecific neighbours (monocultures) or with heterospecific neighbours (two and four species communities), all assembled from two pools of four separate temperate grassland species each. We analysed changes in species and community‐level productivity and P acquisition. The CMN treatment affected species differently. Most species had reduced shoot biomass while root biomass increased with CMN disconnection. Productivity and nutrient acquisition of Plantago lanceolata in four‐species mixtures was negatively affected, leading to a less even distribution of P among species, but community‐level P acquisition was not affected. On average, two‐species and four‐species mixtures produced similar community biomass and had the same P content as monocultures. Synthesis. Common mycorrhizal network disconnection affected competitive interactions among species only little. One explanation may be that the absence of pronounced competitive hierarchy among the species investigated led to relatively symmetric interactions among species that were stable with respects to additional common mycorrhizal network effects. Another explanation is that common mycorrhizal network effects are less important in natural soils with natural arbuscular mycorrhizal fungi communities than experiments with few arbuscular mycorrhizal fungi strains and often sterilized soils suggest. Common mycorrhizal network disconnection affected competitive interactions among species only little. One explanation may be that the absence of pronounced competitive hierarchy among the species investigated led to relatively symmetric interactions among species that were stable with respects to additional common mycorrhizal network effects. Another explanation is that common mycorrhizal network effects are less important in natural soils with natural arbuscular mycorrhizal fungi communities than experiments with few arbuscular mycorrhizal fungi strains and often sterilized soils suggest.
    Keywords: Arbuscular Mycorrhizal Fungi ; Common Mycorrhizal Network ; Complementarity And Competition ; Nutrient Mobility ; Resource Ratio Theory ; Temperate Grassland Species
    ISSN: 0022-0477
    E-ISSN: 1365-2745
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  • 4
    In: New Phytologist, July 2018, Vol.219(1), pp.195-205
    Description: Remobilization of zinc (Zn) from shoot to grain contributes significantly to Zn grain concentrations and thereby to food quality. On the other hand, strong accumulation of cadmium (Cd) in grain is detrimental for food quality. Zinc concentrations and isotope ratios were measured in wheat shoots (Triticum aestivum) at different growth stages to elucidate Zn pathways and processes in the shoot during grain filling. Zinc mass significantly decreased while heavy Zn isotopes accumulated in straw during grain filling (Δ66Znfull maturity–flowering = 0.21–0.31‰). Three quarters of the Zn mass in the shoot moved to the grains, which were enriched in light Zn isotopes relative to the straw (Δ66Zngrain–straw −0.21 to −0.31‰). Light Zn isotopes accumulated in phloem sinks while heavy isotopes were retained in phloem sources likely because of apoplastic retention and compartmentalization. Unlike for Zn, an accumulation of heavy Cd isotopes in grains has previously been shown. The opposing isotope fractionation of Zn and Cd might be caused by distinct affinities of Zn and Cd to oxygen, nitrogen, and sulfur ligands. Thus, combined Zn and Cd isotope analysis provides a novel tool to study biochemical processes that separate these elements in plants.
    Keywords: Cadmium Cd ; Element Speciation ; Isotope Ratios ; Remobilization ; Wheat ; Zinc Zn
    ISSN: 0028-646X
    E-ISSN: 1469-8137
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  • 5
    In: Journal of Raman Spectroscopy, March 2017, Vol.48(3), pp.368-373
    Description: Pyrophosphatases (EC 3.6.1.1) are ubiquitous enzymes that catalyse the hydrolysis of pyrophosphate, a byproduct of many biochemical reactions. The hydrolysis leads to an oxygen isotope exchange between the newly formed phosphate molecules and water. Here, we applied Raman spectroscopy to monitor the oxygen isotope exchange reaction in presence of pyrophosphatase from baker's yeast. For this purpose, enzymatic assays consisting of 0.8  O‐enriched phosphate were prepared under pH‐buffered conditions. Upon addition of pyrophosphatase, the Raman spectrum of the solution immediately started to shift to higher wavenumbers, indicating the progressive substitution of O in phosphate by O from water. The analytical results were quantified by fitting a Voigt function to the measured Raman spectra that allowed to determine the relative contribution of each phosphate isotopologue in solution over time. Based on the relative contribution of the different phosphate species, the apparent overall oxygen exchange rate could be calculated assuming a first‐order kinetic. The progressive formation and disappearance of the different phosphate isotopologues were then modelled by applying a consecutive reaction scheme with first‐order steps. The results of our experiments show that Raman spectroscopy can be used to study the kinetics of enzyme‐catalysed oxygen isotope exchange in the phosphate–water system. Copyright © 2016 John Wiley & Sons, Ltd. Here, we show that Raman spectroscopy can be applied to monitor enzyme‐catalysed oxygen isotope exchange between phosphate and water. Quantification of the overlapping Raman spectra allowed to calculate the overall reaction rate of the oxygen isotope exchange.
    Keywords: Pyrophosphatase ; Oxygen Isotope Exchange ; Phosphate ; Water ; Cofactor ; Kinetics
    ISSN: 0377-0486
    E-ISSN: 1097-4555
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  • 6
    In: Journal of Applied Ecology, June 2009, Vol.46(3), pp.683-691
    Description: 1 Increasing plant species richness often increases biomass production in nutrient‐poor semi‐natural grasslands. If such positive diversity–productivity effects also apply to nutrient‐rich agricultural grasslands, mixtures could improve resource‐use efficiency in the vast area used for forage production. We therefore quantified the diversity–productivity effects in nutrient‐rich agricultural grasslands using four‐species grass–legume mixtures. 2 The sown overall density and species proportions of Lolium perenne, Dactylis glomerata, Trifolium pratense and Trifolium repens were varied in a 3‐year field experiment to investigate the effects of species richness (1, 2, 4 species) and species proportion (0, 3, 10, 25, 40, 50, 70, 90, 100% sowing proportion) on productivity under a nitrogen fertilization of 50, 150 or 450 kg N ha−1 year−1. 3 The four‐species mixtures reached up to twice the yield of the average of the four species’ monocultures (overyielding up to 106%), predominantly due to combining grass and legume species. Mixtures were up to 57% more productive than the most productive monoculture (transgressive overyielding). Both these diversity–productivity effects appeared across a broad range of species proportions and persisted at the two lower levels of N fertilization for 3 years. 4 Mixtures fertilized with 50 kg N ha−1 year−1 produced yields comparable to grass monocultures fertilized with 450 kg N ha−1 year−1, if the legume proportion was about 50 to 70%. Diversity–productivity effects were reduced at the highest level of N fertilization, where they virtually disappeared in the third year. Increased N fertilization also accelerated the observed general trend towards D. glomerata dominated and legume‐poor swards. 5 Synthesis and applications. Diversity–productivity effects led to consistent transgressive overyielding in intensively managed grasslands, suggesting a highly increased resource‐use efficiency in mixtures. Performance better than monocultures can be achieved with grass–legume mixtures that have a low number of species, across a wide range of species proportions and in nutrient‐rich conditions. Processes such as niche complementarity and positive interspecific interactions leading to diversity effects proved to be highly relevant and widely applicable for intensive forage production. Such diversity–productivity effects could allow reduced inputs of N fertilizer without loss of productivity in different grassland production systems.
    Keywords: Cost 852 ; Diversity–Ecosystem Function ; Diversity–Productivity Effects ; Grass–Legume Mixtures ; Monocultures ; Rgrd ; Simplex Design ; Species Proportions ; Yield
    ISSN: 0021-8901
    E-ISSN: 1365-2664
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  • 7
    In: Journal of Industrial Ecology, December 2010, Vol.14(6), pp.874-877
    ISSN: 1088-1980
    E-ISSN: 1530-9290
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  • 8
    In: New Phytologist, October 2006, Vol.172(1), pp.117-126
    Description: •  In grasslands, the loss of structural carbon (C) from nonharvested plant parts is a primary C source for the soil. The amount of input depends not only on the size of structural C pools but also on their loss rates. •  In the field, we examined the effects of elevated atmospheric partial pressures of CO2 (pCO2) and nitrogen (N) supply on pool size and rates of structural C loss in stubble and roots of perennial ryegrass (Lolium perenne) by using multiple‐pulse labelling and steady‐state labelling. •  Stubble retained structural C for roughly half the time it was retained in roots. Elevated pCO2 combined with low N supply enlarged the pools of roots and stubble. These conditions also stimulated the rate of structural C loss from stubble and, thus, the amounts available for further transformation. •  The potential of multiple‐pulse labelling as a field technique is highlighted. The stimulation of structural C loss from stubble by elevated pCO2 at low N provides a missing link between increased C assimilation and low yield response and indicates a potentially higher input of structural C into the soil.
    Keywords: Elevated Co ; Perennial Ryegrass ; Managed Grassland ; Pulse Labelling ; Roots ; Steady‐State Labelling ; Structural Carbon Loss ; Stubble
    ISSN: 0028-646X
    E-ISSN: 1469-8137
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  • 9
    Language: English
    In: Journal of Plant Nutrition and Soil Science, December 2015, Vol.178(6), pp.896-903
    Description: Inadequate plant nutrition and biotic stress are key threats to current and future crop yields. Zinc (Zn) deficiency and toxicity in major crop plants have been documented, but there is limited information on how pathogen and pest damage may be affected by differing plant Zn levels. In our study, we used soybean plants as a host, a soybean pest, and three soybean pathogens to determine whether plant Zn levels change pest and disease assessments. Two soybean cultivars were grown in sand culture with a soluble nutrient solution that ranged from Zn‐deficient to toxic. Detached leaves from these plants were either inoculated with , the soybean aphid, pv. , a bacterium that causes bacterial pustule, , the necrotrophic fungus responsible for stem rot, or , a biotrophic obligate pathogen that causes soybean rust. There were significant ( 〈 5%) effects on aphid colonization, positive counts for bacterial pustule, orum leaf area affected, and numbers of rust lesions associated with the Zn treatments. Plants grown with the physiologically optimal levels of Zn (2 µM) had less ( 〈 5%) soybean aphids cm leaflet than plants grown without Zn, at 0.1× Zn (0.2 µM), or at 100× Zn fertilization (200 µM). Plants grown with the normal fertilization of Zn or 100× Zn had fewer ( 〈 5%) positive counts for bacterial pustule and less lesion area affected by than plants grown without Zn or fertilized with 0.1× Zn. For soybean rust, plants grown with the physiologically optimal fertilization of Zn or 100× Zn had higher ( 〈 5%) lesions cm on leaflets from plants grown without Zn or fertilized with 0.1× Zn. These results indicate different Zn nutrition levels in soybean significantly affected aphid and disease development.
    Keywords: Aphis Glycines ; Glycine Max ; Phakopsora Pachyrhizi ; Sclerotinia Sclerotiorum ; Xanthomonas Axonopodis
    ISSN: 1436-8730
    E-ISSN: 1522-2624
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  • 10
    Language: English
    In: Journal of Plant Nutrition and Soil Science, June 2012, Vol.175(3), pp.385-393
    Description: Lower P‐input levels in organic than conventional farming can decrease soil total and available P, which can potentially be resupplied from soil organic P. We studied the effect of 30 y of conventional and organic farming on soil P forms, focussing especially on organic P. Soil samples (0–20 cm) were taken in a field experiment with a nonfertilized control, two organic systems receiving P inputs as animal manure, and two conventional systems receiving only mineral P or mineral P and manure. Soils were analyzed for total, inorganic, organic, and microbial P, by sequential P fractionation and by enzyme additions to alkaline soil extracts. Samples taken prior to starting the experiment were also analyzed. Average annual P balances ranged from –20 to +5 kg ha. For systems with a negative balance, labile and moderately labile inorganic P fractions decreased, while organic and stable inorganic P fractions were hardly affected. Similar quantities and proportions of organic P extracted with NaOH‐EDTA were hydrolyzed in all soils after addition of an acid phosphatase, a nuclease, and a phytase, and enzyme‐stable organic P was also similar among soils. Thus, neither sequential fractionation nor enzyme addition to alkaline soil extracts showed an effect of the type of applied P (manure mineral) on organic P, suggesting that organic P from manure has largely been mineralized. Thus far, we have no indication that the greater microbial activity of the organic systems resulted in a use of stable P forms.
    Keywords: Manure ; Microbial Biomass ; Sequential Fractionation ; Enzymatic Hydrolysis ; Long‐Term Field Experiment
    ISSN: 1436-8730
    E-ISSN: 1522-2624
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