The Experts below are selected from a list of 273 Experts worldwide ranked by ideXlab platform
Sofie Sjögersten - One of the best experts on this subject based on the ideXlab platform.
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composition and concentration of root Exudate analogues regulate greenhouse gas fluxes from tropical peat
Soil Biology & Biochemistry, 2018Co-Authors: N T Girkin, Benjamin L. Turner, Nick Ostle, Sofie SjögerstenAbstract:Abstract Tropical peatlands are a significant carbon store and source of carbon dioxide (CO2) and methane (CH4) to the atmosphere. Plants can contribute to these gas emissions through the release of root Exudates, including sugars and organic acids amongst other biomolecules, but the roles of concentration and composition of Exudates in regulating emissions remains poorly understood. We conducted a laboratory incubation to assess how the type and concentration of root Exudate analogues regulate CO2 and CH4 production from tropical peats under anoxic conditions. For CO2 production, substrate concentration was the more important driver, with increased CO2 fluxes following higher addition rates of four out of the six Exudate analogues. In contrast, Exudate type was the more important driver of CH4 production, with acetate addition associated with the greatest production, and inverse correlations between Exudate concentration and CH4 emission for the remaining five treatments. Root Exudate analogues also altered pH and redox potential, dependent on the type of addition (organic acid or sugar) and the concentration. Overall, these findings demonstrate the contrasting roles of composition and concentration of root Exudate inputs in regulating greenhouse gas emissions from tropical peatlands. In turn this highlights how changes in plant communities will influence emissions through species specific inputs, and the possible impacts of increased root exudation driven by rising atmospheric CO2 and warming.
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root Exudate analogues accelerate co2 and ch4 production in tropical peat
Soil Biology & Biochemistry, 2018Co-Authors: N T Girkin, Benjamin L. Turner, J. Craigon, Nick Ostle, Sofie SjögerstenAbstract:Root Exudates represent a large and labile carbon input in tropical peatlands, but their contribution to carbon dioxide (CO2) and methane (CH4) production remains poorly understood. Changes in species composition and productivity of peatland plant communities in response to global change could alter both inputs of Exudates and associated greenhouse gas emissions. We used manipulative laboratory incubations to assess the extent to which root Exudate quantity and chemical composition drives greenhouse gas emissions from tropical peatlands. Peat was sampled from beneath canopy palms (Raphia taedigera) and broadleaved evergreen trees (Campnosperma panamensis) in an ombrotrophic wetland in Panama. Root Exudate analogues comprising a mixture of sugars and organic acids were added in solution to peats derived from both species, with CO2 and CH4 measured over time. CO2 and CH4 production increased under most treatments, but the magnitude and duration of the response depended on the composition of the added labile carbon mixture rather than the quantity of carbon added or the botanical origin of the peat. Treatments containing organic acids increased soil pH and altered other soil properties including redox potential but did not affect the activities of extracellular hydrolytic enzymes. CO2 but not CH4 production was found to be linearly related to microbial activity and redox potential. Our findings demonstrate the importance of root Exudate composition in regulating greenhouse gas fluxes and propose that in situ plant species changes, particularly those associated with land use change, may account for small scale spatial variation in CO2 and CH4 fluxes due to species specific root Exudate compositions.
Andrea Carminati - One of the best experts on this subject based on the ideXlab platform.
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Rhizodeposition under drought is controlled by root growth rate and rhizosphere water content
Plant and Soil, 2017Co-Authors: Michael Holz, Mohsen Zarebanadkouki, Anders Kaestner, Yakov Kuzyakov, Andrea CarminatiAbstract:AimsRhizodeposition is an important energy source for soil microorganisms. It is therefore crucial to estimate the distribution of root derived carbon (C) in soil and how it changes with soil water content.MethodsWe tested how drought affects Exudate distribution in the rhizosphere by coupling 14CO2 labelling of plants and phosphor imaging to estimate C allocation in roots. Rhizosphere water content was visualized by neutron radiography. A numerical model was employed to predict the Exudate release and its spatiotemporal distribution along and around growing roots.ResultsDry and wet plants allocated similar amounts of 14C into roots but root elongation decreased by 48% in dry soil leading to reduced longitudinal rhizosphere extension. Rhizosphere water content was identical (31%) independent of drought, presumably because of the high water retention by mucilage. The model predicted that the increase in rhizosphere water content will enhance diffusion of Exudates especially in dry soil and increase their microbial decomposition.ConclusionRoot growth and rhizosphere water content play an important role in C release by roots and in shaping the profiles of root Exudates in the rhizosphere. The release of mucilage may be a plant strategy to maintain fast diffusion of Exudates and high microbial activity even under water limitation.
Fien Degryse - One of the best experts on this subject based on the ideXlab platform.
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Isotopic fractionation of Zn in tomato plants suggests the role of root Exudates on Zn uptake
Plant and Soil, 2013Co-Authors: Erik Smolders, Liske Versieren, Dong Shuofei, Nadine Mattielli, Dominik Weiss, Ivan Petrov, Fien DegryseAbstract:Aims Phytosiderophore-chelated Zn can be absorbed in grasses. Root Exudates of dicotyledonous plants can mobilize soil Zn but it is unclear how this affects Zn bioavailability. Stable Zn isotope shifts can indicate Exudate-facilitated Zn uptake, since complexation of Zn^2+ by organic ligands in solution yields a small, but detectable, enrichment of the heavy Zn isotope due to thermodynamic fractionation. Methods Tomato seedlings were grown in resin-buffered nutrient solution in which free Zn^2+ concentrations are buffered, in a factorial design of two Zn levels and two solution volumes. The latter factor allowed altering the Exudate concentrations in the solution. Dissolved Cu concentrations in the resin buffered system were used as a sensitive index of metal mobilization resulting from root activity. In addition, seedlings were grown in Zn deficient soil with and without Zn addition. Results The dissolved Cu concentration increased with Zn deficiency and was highest at the lowest solution volume, suggesting metal mobilization by root Exudates. At low Zn supply, Zn in the plant was enriched in heavy Zn (^66Zn) and this was most pronounced at small solution volume. Similarly, Zn deficiency in soil enriched tomato shoot Zn with heavy isotope in this plant. Interpretation Zinc deficiency increases the contribution of Zn-Exudate complexes, which are enriched in the heavy isotope compared to the free ion, to Zn uptake by transporting Zn from the bulk solution or soil to the roots where they likely dissociate and release Zn^2+.
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isotopic fractionation of zn in tomato plants suggests the role of root Exudates on zn uptake
Plant and Soil, 2013Co-Authors: Erik Smolders, Liske Versieren, Dong Shuofei, Nadine Mattielli, Ivan Petrov, Dominik J Weiss, Fien DegryseAbstract:Aims Phytosiderophore-chelated Zn can be absorbed in grasses. Root Exudates of dicotyledonous plants can mobilize soil Zn but it is unclear how this affects Zn bioavailability. Stable Zn isotope shifts can indicate Exudate-facilitated Zn uptake, since complexation of Zn2+ by organic ligands in solution yields a small, but detectable, enrichment of the heavy Zn isotope due to thermodynamic fractionation.
Yakov Kuzyakov - One of the best experts on this subject based on the ideXlab platform.
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spatial pattern of enzyme activities depends on root Exudate composition
Soil Biology & Biochemistry, 2019Co-Authors: Xuechen Zhang, Michaela A. Dippold, Yakov Kuzyakov, Bahar S RazaviAbstract:Abstract Roots increase microbial activities depending on Exudate composition, especially on the ratios of sugars, carboxylic and amino acids, and thus structure enzyme activities in the rhizosphere. We introduce a new approach combining soil zymography and simulated Exudates released from Rhizon® samplers to stimulate microbial activities but avoid the direct release of enzymes by living roots. This enabled visualizing, localizing and analyzing the effects of simulated root Exudates on activity of five microbial enzymes involved in carbon (C) (β-glucosidase, cellobiohydrolase), nitrogen (N) (leucine aminopeptidase), phosphorus (P) (phosphatase) and sulfur (S) (sulfatase) cycles. We tested the hypotheses that 1) artificial Exudates stimulate microorganisms for enzyme production and form spatial gradients around roots, and 2) the extent of microbial enzyme activities in the rhizosphere is component-specific. In line with these hypotheses, the activities of P-, N- and S-related enzymes were higher near the artificial root and gradually decreased as a function of distance from the root. The pattern for C-cycle enzymes was uniform and independent of the Exudate composition. Among all components, alanine increased the rhizosphere extent much stronger than other substances, while methionine had no effect on the spatial distribution of enzyme activities. Vmax of all enzymes increased with alanine addition, but decreased after adding citrate. The ratios of enzyme activities demonstrated that rhizosphere microorganisms release more leucine aminopeptidase than other enzymes to meet their N demand. Glucose increased the Km of cellobiohydrolase and β-glucosidase, while alanine had the greatest effect on the Km of leucine aminopeptidase and sulfatase. Phosphatase is the enzyme most sensitive to the composition of root Exudates; consequently, any factor influencing root Exudate composition can strongly affect the P cycle. We conclude that the rhizosphere extent of microbial-derived enzyme activities is component- and enzyme-specific and that this extent depends on the substrate stoichiometry and microbial nutrient demand.
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Rhizodeposition under drought is controlled by root growth rate and rhizosphere water content
Plant and Soil, 2017Co-Authors: Michael Holz, Mohsen Zarebanadkouki, Anders Kaestner, Yakov Kuzyakov, Andrea CarminatiAbstract:AimsRhizodeposition is an important energy source for soil microorganisms. It is therefore crucial to estimate the distribution of root derived carbon (C) in soil and how it changes with soil water content.MethodsWe tested how drought affects Exudate distribution in the rhizosphere by coupling 14CO2 labelling of plants and phosphor imaging to estimate C allocation in roots. Rhizosphere water content was visualized by neutron radiography. A numerical model was employed to predict the Exudate release and its spatiotemporal distribution along and around growing roots.ResultsDry and wet plants allocated similar amounts of 14C into roots but root elongation decreased by 48% in dry soil leading to reduced longitudinal rhizosphere extension. Rhizosphere water content was identical (31%) independent of drought, presumably because of the high water retention by mucilage. The model predicted that the increase in rhizosphere water content will enhance diffusion of Exudates especially in dry soil and increase their microbial decomposition.ConclusionRoot growth and rhizosphere water content play an important role in C release by roots and in shaping the profiles of root Exudates in the rhizosphere. The release of mucilage may be a plant strategy to maintain fast diffusion of Exudates and high microbial activity even under water limitation.
Muhammad Naveed - One of the best experts on this subject based on the ideXlab platform.
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residues with varying decomposability interact differently with seed or root Exudate compounds to affect the biophysical behaviour of soil
Geoderma, 2019Co-Authors: Ewan Oleghe, Elizabeth M Baggs, Muhammad Naveed, Paul D HallettAbstract:Abstract Plants have a large impact on the physical behaviour of soil, partly due to seed and root Exudates that alter mineral:organic matter associations. In this study we explored how the decomposability of residues in soil interacts with seed or root Exudate compounds to influence microbial respiration, mechanical behaviour and hydrological properties. Sandy loam and clay loam soils were amended at a rate of 40 t ha−1 with ground green barley (7.13 mg C g−1), barley straw (7.26 mg C g−1) or poultry manure (5.22 mg C g−1), and either chia seed Exudate at 1.84 mg C g−1 soil or root Exudate compounds at 14.4 mg C g−1 soil. On cores packed to 1.3 g cm−3, uniaxial compression, penetration resistance, water sorptivity, water retention and porosity were measured at time 0, after 14 days of incubation at 20 °C, and then after subjecting incubated soils to three cycles of wetting and drying to simulate weathering. These time increments and weathering were intended to simulate a newly germinated seed or tip of a root, through to a more mature system. Application of seed and root Exudate increased carbon dioxide (CO2) emissions from 0.31 ± 0.01 to 15.11 ± 0.71 μg C-CO2 g soil−1 h−1 for the sandy loam soil and from 0.171 ± 0.01 to 10.56 ± 0.78 C-CO2 g soil−1 h−1 for the clay loam soil. There were large changes in soil physical properties caused by seed or root Exudate amendment coupled with residues, their decomposition and weathering. After incubation and weathering, soils with added seed or root Exudates and their interactions with organic residues were more mechanically stable, as measured by penetration resistance (22 to 58% increase) and compression index (25 to 43% decrease) compared to soils amended only with organic residue. Water sorptivity and porosity diminished with the addition of the Exudate. Exudates in combination with organic residues better protected soils against structural destabilization by increasing particle cementation, and decreasing rapid wetting and porosity.
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Surface tension, rheology and hydrophobicity of rhizodeposits and seed mucilage influence soil water retention and hysteresis
Plant and Soil, 2019Co-Authors: Muhammad Naveed, M. A. Ahmed, P. Benard, L. K. Brown, T. S. George, A. G. Bengough, T. Roose, N. Koebernick, P. D. HallettAbstract:Aims Rhizodeposits collected from hydroponic solutions with roots of maize and barley, and seed mucilage washed from chia, were added to soil to measure their impact on water retention and hysteresis in a sandy loam soil at a range of concentrations. We test the hypothesis that the effect of plant Exudates and mucilages on hydraulic properties of soils depends on their physicochemical characteristics and origin. Methods Surface tension and viscosity of the Exudate solutions were measured using the Du Noüy ring method and a cone-plate rheometer, respectively. The contact angle of water on Exudate treated soil was measured with the sessile drop method. Water retention and hysteresis were measured by equilibrating soil samples, treated with Exudates and mucilages at 0.46 and 4.6 mg g^−1 concentration, on dialysis tubing filled with polyethylene glycol (PEG) solution of known osmotic potential. Results Surface tension decreased and viscosity increased with increasing concentration of the Exudates and mucilage in solutions. Change in surface tension and viscosity was greatest for chia seed Exudate and least for barley root Exudate. Contact angle increased with increasing maize root and chia seed Exudate concentration in soil, but not barley root. Chia seed mucilage and maize root rhizodeposits enhanced soil water retention and increased hysteresis index, whereas barley root rhizodeposits decreased soil water retention and the hysteresis effect. The impact of Exudates and mucilages on soil water retention almost ceased when approaching wilting point at −1500 kPa matric potential. Conclusions Barley rhizodeposits behaved as surfactants, drying the rhizosphere at smaller suctions. Chia seed mucilage and maize root rhizodeposits behaved as hydrogels that hold more water in the rhizosphere, but with slower rewetting and greater hysteresis.
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Plant Exudates improve the mechanical conditions for root penetration through compacted soils
Plant and Soil, 2017Co-Authors: Ewan Oleghe, Elizabeth M Baggs, Muhammad Naveed, P. D. HallettAbstract:Background and aim Plant Exudates greatly affect the physical behaviour of soil, but measurements of the impact of Exudates on compression characteristics are missing. Our aim is to provide these data and explore how plant Exudates may enhance the restructuring of compacted soils following cycles of wetting and drying. Methods Two soils were amended with Chia ( Salvia hispanica) seed Exudate at 5 concentrations, compacted in cores to 200 kPa stress (equivalent to tractor stress), equilibrated to −50 kPa matric potential, and then compacted to 600 kPa (equivalent to axial root stress) followed by 3 cycles of wetting and drying and recompression to 600 kPa at −50 kPa matric potential. Penetration resistance (PR), compression index (C_C) and pore characteristics were measured at various steps. Results PR decreased and C_C increased with increasing Exudate concentration. At 600 kPa compression, 1.85 mg Exudate g^−1 soil increased C_C from 0.37 to 0.43 for sandy loam soil and from 0.50 to 0.54 for clay loam soil. After 3 wetting-drying cycles the clay loam was more resillient than the sandy loam soil, with resilience increasing with greater Exudate concentration. Root growth modelled on PR data suggested plant Exudates significantly eased root elongation in soil. Conclusion Plant Exudates improve compression characteristics of soils, easing penetration and enhancing recovery of root induced soil compaction.
