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Curnow, Philip Kenneth. "Influence of root exudates on rhizosphere pseudomonads." Thesis, Imperial College London, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286230.
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Shi, Shengjing. "Influence of root exudates on soil microbial diversity and activity." Lincoln University, 2009. http://hdl.handle.net/10182/1549.
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Interactions between plant roots and soil microorganisms in the rhizosphere are critical for plant growth. However, understanding of precisely how root exudates influence the diversity and activity of rhizosphere microorganisms is limited. The main objective of this study was to investigate the effect of radiata pine (Pinus radiata) root exudates on rhizosphere soil microbial communities, with an emphasis on the role of low molecular weight organic anions. The study involved the development and validation of new methods for investigating rhizosphere processes in a purpose-built facility. This included development of an in situ sampling technique using an anion exchange membrane strip to collect a range of organic anions exuded from radiata pine roots grown in large-scale rhizotrons. These included tartarate, quinate, formate, malate, malonate, shikimate, lactate, acetate, maleate, citrate, succinate and fumarate. Soil microbial activity and diversity were determined using dehydrogenase activity and denaturing gradient gel electrophoresis. Links between organic anions in root exudates and rhizosphere soil microbial community structures were investigated by comparing wild type and genetically modified radiata pine trees which were grown in rhizotrons for 10 months. As expected, there was considerable temporal and spatial variability in the amounts and composition of organic anions collected, and there were no consistent or significant differences determined between the two tree lines. Significant differences in rhizosphere microbial communities were detected between wild type and genetically modified pine trees; however, they were inconsistent throughout the experiment. The shifts in microbial communities could have been related to changes in exudate production and composition. Based on results from the main rhizotron experiment, a microcosm study was carried out to investigate the influence of selected pine root exudate sugars (glucose, sucrose and fructose) and organic anions (quinate, lactate and maleate) on soil microbial activity and diversity. Soil microbial activity increased up to 3-fold in all of the sugar and organic anion treatments compared to the control, except for a mixture of sugars and maleate where it decreased. The corresponding impacts on soil microbial diversity were assessed using denaturing gradient gel electrophoresis and 16S rRNA phylochips. Addition of the exudate compounds had a dramatic impact on the composition and diversity of the soil microbial community. A large number of bacterial taxa (88 to 1043) responded positively to the presence of exudate compounds, although some taxa (12 to 24) responded negatively. Organic anions had a greater impact on microbial communities than sugars, which indicated that they may have important roles in rhizosphere ecology of radiata pine. In addition, a diverse range of potentially beneficial bacterial taxa were detected in soil amended with organic anions, indicating specific regulation of rhizosphere microbial communities by root exudates. This project highlighted the considerable challenges and difficulties involved in detailed investigation of in situ rhizosphere processes. Nonetheless, the findings of this study represent a significant contribution to advancing understanding of relationships between root exudates and soil microbial diversity, which will be further enhanced by refinement and application of the specific methodologies and techniques developed.
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Vives, Peris Vicente. "Interaction of citrus root exudates with plant growth promoting rhizobacteria under abiotic stress conditions." Doctoral thesis, Universitat Jaume I, 2018. http://hdl.handle.net/10803/461915.
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En la naturaleza las plantas liberan constantemente a la rizosfera una mezcla de metabolitos conocida como exudados radiculares. Su composición puede verse afectada por diferentes estímulos, incluyendo estreses abióticos como la salinidad o elevadas temperaturas. El Capítulo 1 demuestra que los portainjertos de cítricos citrange Carrizo y Citrus macrophylla exudan diferentes concentraciones de prolina y fitohormonas dependiendo del estrés abiótico y del genotipo. El Capítulo 2 estudia el efecto de dichos exudados de plantas de cítricos sometidas a salinidad y calor sobre las rizobacterias Pseudomonas putida KT2440 y Novosphingobium sp. HR1a, los cuales generalmente promueven su crecimiento. Además, se detectó la presencia de prolina y salicilatos en exudados a través del análisis de la expresión de los promotores PputA y PpahA de P. putida KT2442 y Novosphingobium sp. HR1a respectivamente. Finalmente, el Capítulo 3 muestra el efecto beneficioso de ambas bacterias en plantas de C. macrophylla sometidas a salinidad.In nature, plants are constantly releasing a mixture of metabolites through the roots known as root exudates. Its composition can be affected by different stimuli, including abiotic stress conditions as salinity or high temperatures. Chapter 1 demonstrates that citrus rootstocks Carrizo citrange and Citrus macrophylla exude different concentrations of proline and phytohormones depending on the abiotic stress condition and the genotype. Chapter 2 studies the effect of citrus root exudates from salt- and heat-stressed plants on the rhizobacteria Pseudomonas putida KT2440 and Novosphingobium sp. HR1a, which generally promote their growth. Moreover, the presence of proline and salicylates in root exudates was also tested through the analyses of the expression of the promoters PputA and PpahA of P. putida KT2442 and Novosphingobium sp. HR1a, respectively. Finally, Chapter 3 reveals the beneficial effect of both bacterial strains in C. macrophylla plants subjected to salt stress conditions.
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Henry, Amelia. "Effect of Drought, Flooding, and Potassium Stress on the Quantity and Composition of Root Exudates in Axenic Culture." DigitalCommons@USU, 2003. https://digitalcommons.usu.edu/etd/5633.
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Root exudates include important chelating compounds and can change the rhizosphere pH by several units. These changes are essential for nutrient uptake and can also alter solubility of soil contaminants and increase plant uptake. Mild root-zone stress may increase exudation and more severe stress can damage membranes and increase root turnover, all of which increase root-zone carbon. Increased carbon from this rhizodeposition can increase microbial activity, which might help degrade contaminants. We studied the effect of three types of stress on root exudation of crested wheatgrass (Agropyron cristatum): low K+, drought, and flooding. These stresses were compared to two types of controls: 100% NO3- and high NH4+:NO3- ratio. We developed an improved axenic system to keep plants microbe-free for 70 days while analyzing exudates for total organic carbon (TOC) and organic acids. Axenic conditions were confirmed by plate counts of the leachate and microscopic observations of the leachate and roots. Optimal conditions for plant growth were maintained by monitoring temperature, light, humidity, water, O2, CO2, nutrient availability, and root-zone pH. Plants were grown in Ottawa sand that was layered by size to optimize water availability. Total organic carbon released over the 70-day growth period in mg per gram dry plant was 2.6 in the control, 2.3 in the NH4+ treatment, 3.7 in the flood and K+ stress treatments, and 4.4 in the drought treatment, which was the only treatment significantly higher than controls (p = 0.05). TOC and organic acid levels in the exudates peaked before the end of the study. The peak TOC levels, expressed as mg TOC per gram new dry plant mass, were 1.9 in the control, 3.0 in the NH4+ treatment, 2.9 in the flood, and 5.8 in the drought and K+ stress treatments. Organic acids were measured by gas chromatography-mass spectrometry (GC-MS). Malic acid was the predominant organic acid, and accounted for the majority of the TOC in the drought treatment. Oxalic, succinic, fumaric, and malonic acids accounted for less than 10% of the TOC. These data indicate that stress may enhance phytoremediation by changing root-zone exudate composition.
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Medina, Rachel Morales. "Investigation of Maize Root Exudates on Heterodera glycines Populations under Direct and Indirect Exposure." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1482499805741097.
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Curlango-Rivera, Gilberto. "Function of Root Border Cells and their Exudates on Plant Defense in Hydroponic Systems." Diss., The University of Arizona, 2011. http://hdl.handle.net/10150/202535.
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Controlled environment agriculture offers a solution to challenges including less available land, water deficits, and consumer demand for pesticide free produce. However, control of soil-borne diseases is a major limiting factor. The goal of this dissertation was to examine predictions of the hypothesis that border cells function to protect plant health by controlling microorganisms associated with plants grown in hydroponic culture. Border cells separate from root tips upon immersion in water, and appear to have important roles in the defense mechanisms of plant roots. The general objectives were (1) to study the delivery of border cells in hydroponics; (2) to evaluate interactions between border cells and microorganisms in hydroponics; and (3) to explore approaches to alter border cell production for improved root disease control. In this study it was confirmed that border cells can be released continuously into the solution of hydroponic culture suggesting that plants grown in this system may use extra energy in the production of new border cells. Free border cells interacted with microorganisms present in the hydroponic solution by secreting an extracellular capsule. Previous studies showed that proteins are a key component of this capsule, including lectins. The interaction of pea lectin and Nectria haematococca spores therefore was explored. Results demonstrated that pea lectin agglutinates fungal spores in a hapten-specific manner, and inhibits their germination. Lectin had no negative effect on root development suggesting that it could be used as a potential control for soil-borne diseases in hydroponics. To control the production of border cells, subsequent studies measured the impact of a transient exposure of root tips to different metabolites secreted by root caps and border cells. Exposure to specific metabolites altered the production of border cells without measurable effects on root growth and development. This is in contrast to results obtained with altered gene expression. For example, gene silencing of a border cell specific gene resulted in altered root growth.
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Sun, Lijuan. "Study on the mechanisms of rhizosphere priming effects induced by root exudates in a temperate broad-leaved forest." Kyoto University, 2018. http://hdl.handle.net/2433/232351.
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Kyoto University (京都大学)0048
新制・課程博士
博士(農学)
甲第21150号
農博第2276号
新制||農||1059(附属図書館)
学位論文||H30||N5124(農学部図書室)
京都大学大学院農学研究科地域環境科学専攻
(主査)教授 北山 兼弘, 教授 小杉 緑子, 教授 本田 与一
学位規則第4条第1項該当
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Kierul, Kinga. "Comprehensive proteomic study of Bacillus amyloliquefaciens strain FZB42 and its response to plant root exudates." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2013. http://dx.doi.org/10.18452/16805.
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Bacillus amyloliquefaciens FZB42 ist ein frei lebendes Bakterium, das Pflanzenwurzeln besiedelt und das Pflanzenwachstum durch viele verschiedene Wirkmechanismen anregt. In dieser Arbeit wurden die molekularen Grundlagen dieser positiven Wirkungen, die dieses „Pflanzenwachstum fördernde Rhizobakterium“ (PGPR) auf seine Wirte ausübt, untersucht. Um den gegenseitigen Austausch von B. amyloliquefaciens und seinen Wirtspflanzen zu entschlüsseln, wurden umfangreiche Proteomstudien durchgeführt. Es wurden Referenzkarten der extrazellulären und zytosolischen Proteinfraktionen erstellt. Die größte Anzahl an ausgeschiedenen Proteinen konnte während der stationären Phase beobachtet werden. Die identifizierten extrazellulären Proteine gehören verschiedenen Funktionsklassen an, wobei die prominentesten Klassen am Kohlenhydrat-Abbau und den Transport von Molekülen durch die Zellwand beteiligt sind. Die zytosolischen Extrakte von Kulturen, die in 1C-Medium bzw. Mineralmedium angezogen wurden, und in der zweidimensionalen Gelelektrophorese (2 DE) aufgetrennt wurden, ergaben 461 und 245 verschiedene Protein-Einträge. Die erstellten Referenz-Karten wurden anschließend verwendet, um Proteine und Prozesse, in an der Interaktion mit Pflanzen beteiligt sind, zu identifizieren. Dafür wurden die Bakterien Wurzelexudaten von Mais (Zea mays L.) ausgesetzt. Die Proteine aus zwei Stämmen, denen die globalen Transkriptionsregulatoren (Degu, AbrB) und vier Sigma-Faktoren (SigB, SigM, SigV, und SigX) fehlen, wurden ebenfalls untersucht, um ihre Beteiligung an den bakteriellen Reaktionen auf die Wurzelausscheidungen zu analysieren. Zusammenfassend ist dies die erste Studie, die umfangreiche Proteomdaten von Gram-positiven PGPR präsentiert, wobei gleichzeitig die Veränderung der Expression von extrazellulären und zytoplasmatischen Proteinen, nach Zugabe von Wurzelexudaten, ausgewertet wurde.Bacillus amyloliquefaciens strain FZB42 is a free-living bacterium that competitively colonizes plant roots and stimulates plant growth by many different modes of action. The molecular basis of singular beneficial effects that this Plant Growth-Promoting Rhizobacteria (PGPR) exert on their hosts have been studied. To decipher the molecular cross-talk of B. amyloliquefaciens and its’ host plants as a whole system, an extensive proteomic approach was performed. Reference maps of the extracellular and cytosolic protein fractions were established. The highest number of secreted proteins was observed during stationary growth phase. Identified extracellular proteins belong to different functional classes, with the most prominent classes involved in carbohydrate degradation and transportation of molecules across the cell wall. Cytosolic extracts obtained from cultures grown in 1C and minimal media subjected to the 2 Dimensional Electrophoresis (2 DE), revealed 461 and 245 different protein entries, respectively. Created reference maps were subsequently used to identify proteins and processes involved in the interaction with plants, prior to exposure of bacteria to maize (Zea mays L.) root exudates. The proteomics of two strains lacking expression of genes coding for global transcriptional regulators (degU, abrB) and four sigma factors (sigB, sigM, sigV, and sigX) were also inves-tigated, in order to analyse their involvement in bacterial responses to root exudates. In summary, this is the first study presenting comprehensive proteomics of Gram-positive PGPR, evaluating at the same time changes in protein expression caused by addition of root exudates at the extracellular and cytosolic level.
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Morris, Kendalynn A. "Nitrogen Cycling in the Rhizosphere of Cheatgrass and Crested Wheatgrass: Contributions of Root Exudates and Senescence." DigitalCommons@USU, 2014. https://digitalcommons.usu.edu/etd/3566.
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Cheatgrass is an invasive weed that has come to dominate large areas of the western United States. Once an ecosystem has been converted to a cheatgrass monoculture, it is extremely difficult to restore native vegetation. Cheatgrass negatively impacts wildlife and increases wildfire frequency and intensity. Understanding how cheatgrass so effectively invades western ecosystems is essential to turning the tide of invasion. One possible key to cheatgrass’ success is alteration of soil nutrient cycling. The goal of this study is to explore how nitrogen (N) may accumulate in cheatgrass soils via redistribution of N within soil N pools. To accomplish this we investigated soil N cycling in soils underneath cheatgrass and crested wheatgrass. We used a 15N isotope tracer to determine the contribution of root exudates to soil N pools. During the 1-week 15N tracer experiment, cheatgrass roots exuded more than twice as much N (0.11 mg N kg-1 soil d-1) as crested wheatgrass roots (0.05 mg N kg-1 soil d-1). We propose that exudation of high N content root exudates leads to the changes in soil N pool size and transformation rates commonly observed in soils under cheatgrass. This research uses a simple and relatively inexpensive isotope tracer to shed light on mechanisms by which invasive plants may alter soil processes. By understanding these mechanisms we may be able to develop strategies for better managing cheatgrass invasion.
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Heim, Alexander. "Chelating organic substances in roots and root exudates and their potential role in aluminium resistance of Norway Spruce (Picea abies (L.) Karst.) /." [S.l.] : [s.n.], 2000. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=13807.
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Khorassani, Reza. "Identification by HPLC-MS of new detected compounds in sugar beet root exudates for soil P mobilization." Göttingen Cuvillier, 2008. http://d-nb.info/989316955/04.
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Dietz, Sophie [Verfasser], Dierk Gutachter] Scheel, Helge [Gutachter] [Bruelheide, and Dam Nicole Marie [Gutachter] van. "Root exudates in the grassland ecosystem / Sophie Dietz ; Gutachter: Dierk Scheel, Helge Bruelheide, Nicole Marie van Dam." Halle (Saale) : Universitäts- und Landesbibliothek Sachsen-Anhalt, 2019. http://nbn-resolving.de/urn:nbn:de:gbv:3:4-1981185920-141553.
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Dietz, Sophie [Verfasser], Dierk [Gutachter] Scheel, Helge [Gutachter] Bruelheide, and Dam Nicole Marie [Gutachter] van. "Root exudates in the grassland ecosystem / Sophie Dietz ; Gutachter: Dierk Scheel, Helge Bruelheide, Nicole Marie van Dam." Halle (Saale) : Universitäts- und Landesbibliothek Sachsen-Anhalt, 2019. http://d-nb.info/1210728699/34.
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Canarini, Alberto. "Drought Effects on Soil Carbon Stability Mediated by Rhizodeposition and Microbes." Thesis, The University of Sydney, 2016. http://hdl.handle.net/2123/15963.
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Drought will increase in frequency and intensity in many areas of the world and has the potential to turn entire ecosystems from a sink to a source of C. Soil represents one of the largest C pools on earth, and small changes in the balance between inputs and outputs may have extreme consequences for total atmospheric CO2 concentrations. Outputs are determined by microbial decomposition of soil organic matter (SOM) which can be divided in pools of different inherent stability and turn-over. A major stable pool of C is represented by organo-mineral complexes (C bound to silt and clay), which is primarily controlled by plant-derived inputs to soil and soil microbes. Drought effects on plants, microbes and their interactions could cause changes to the stable pool of C, however information on this topic is lacking. In this thesis I: (i) reviewed and quantified drought-induced effects on soil respiration and microbial communities by meta-analysis; (ii) quantified the effects of drying and rewetting on wheat-derived C stabilization and N cycling; (iii) quantified and qualified drought-induced effects on root exudation of soybean and sunflower; (iv) examined drought effects to C stabilization in the field. Results show that drought can induce intense losses of C by increasing soil respiration following rewetting. Highest losses were produced in combination of intense drought and C-rich soils. At the same time drying and rewetting can cause intense stress on plants, reducing biomass and C inputs to soil. However plants can adopt different strategies to drought-induced changes which are reflected in different rates and quality of root exudates. In field drought did not change the size of the mineral-associated or more stable soil C, highlighting resistance of grassland soils. Specific microbial groups were linked to stable soil C at different depths and legumes were shown to be a key functional group in mediating drought effects and increasing stable C in soil.
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Herz, Katharina [Verfasser]. "Drivers of intraspecific variation of plant functional traits, plant performance and root exudates in German grasslands / Katharina Herz." Halle, 2017. http://d-nb.info/1142155315/34.
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Fan, Ben. "Plant colonization by GFP-labeled Bacillus amyloliquefaciens FZB42 and transcriptomic profiling of its response to plant root exudates." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2011. http://dx.doi.org/10.18452/16267.
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In dieser Arbeit wurden zunächst die Kolonisationen von drei verschiedenen Pflanzengattungen durch den GFP-markierten Bacillus amyloliquefaciens FZB42 mittels confocaler Lasermikroskopie und Elektronmikroskopie verfolgt. Hier konnte gezeigt werden, dass FZB42 alle ausgewählten Pflanzen besiedeln konnte. Bei Arabidopsis- und Maiskeimlingen wurden die Wurzelhaare und Verbindungen, an denen laterale Wurzeln entstehen, durch FZB42 bevorzugt besiedelt. Weiterhin wurden bei Arabidopsis die Spitzen der Primärwurzeln, und bei Mais die Wurzelkerben bevorzugt besiedelt. Bei Lemna wurden FZB42 Zellansammlungen entlang der Furchen, die zwischen den Epidermiszellen der Wurzel liegen, sowie den intrazellulären Hohlräumen an der Blattunterfläche gefunden. Anschließend wurden die Transkriptome von FZB42, der mit Maiswurzelexudat angezogen wurde, mittels Microarray analysiert. Insgesamt wurden 302 Gene, die 8,2 % des Transkriptoms ausmachen, signifikant durch das Wurzelexudat beeinflusst, wobei die Mehrzahl (260 Gene) hochreguliert wurde. Die induzierten Gene, dessen Funktion bereits bekannt ist, sind hauptsächlich an dem Nährstoffwechsel, Chemotaxis und Beweglichkeit, sowie an der Produktion von Antibiotika beteiligt. Auch wurden die Trankriptome von sieben FZB42-Muatnten durch Microarray analysiert. Diese hatten jeweils eine Deletionen in fünf Sigmafaktor-Genen (sigB, sigD, sigM, sigV,and sigX) und zwei globalen Transkriptionsregulator-Genen (degU und abrB). Die Expression vieler Genen wird durch diese Genprodukte beeinflusst. Mögliche Mechanismen, wie diese Faktoren die bakterielle Reaktion auf Wurzelexsudaten beeinflüssen, wurden vorgeschlagen. Schließlich wurden Northernblott-Untersuchungen an möglichen sRNA-Kandidaten durchgeführt, dessen Expression signifikant durch Wurzelexudate beeinflusst wurde. Dabei konnten 6 von 20 vermeintlichen sRNA-Kandidaten betätigt werden. Dies weist auf eine noch unbekannte Rolle der sRNAs bei der Pflanzen-Mikroben-Wechselwirkung.In this work colonization of three different plants genera, maize, Arabidopsis, and Lemna, by GFP-labeled Bacillus amyloliquefaciens FZB42 in a gnotobiotic system was firtly studied using confocal laser scanning microscopy and electron microscopy. It was shown that FZB42 is able to colonize all these three plants with a specific pattern. Root hairs and the junctions where lateral roots occurred were a preferred area of FZB42 on both maize and Arabidopsis seedlings. On Arabidopsis, tips of primary roots were another favored site of FZB42; while, on maize, the concavities in root surfaces were preferred. FZB42 cells were also able to colonize Lemna, preferably accumulating along the grooves between epidermis cells on roots and the concaved intercellular space on fronds. Secondly, microarray experiments were performed concerning the transcriptomic response of FZB42 to maize root exudates. A total of 302 genes representing 8.2% of FZB42 transcriptome were significantly altered in transcription by the presence of root exudates, the majority of them (260) were up-regulated in expression. The induced genes with known function were mainly involved in nutrition utilization, chemotaxis and motility, and antibiotic production. The transcriptome of seven FZB42 mutants, defective in five sigma factor genes (sigB, sigD, sigM, sigV, and sigX) and two global transcriptional regulator genes (degU and abrB), were also investigated through microarray experiments. A vast number of genes were indentified to be controlled by the protein factors respectively. Possible mechanisms were proposed of how these protein factors are involved in the response to root exudates. Finally, by northern blot existence of six out of 20 small RNA (sRNA) candidates was identified, which were significantly altered in expression by root exudates. This suggests that sRNA may play a hitherto unrecognized role in plant-microbe interaction.
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Guo, Jingqi. "THE INFLUENCE OF TALL FESCUE CULTIVAR AND ENDOPHYTE STATUS ON ROOT EXUDATE CHEMISTRY AND RHIZOSPHERE PROCESSES." UKnowledge, 2014. http://uknowledge.uky.edu/pss_etds/50.
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Tall fescue (Lolium arundinaceum (Schreb.) Darbysh.) is a cool-season perennial grass used in pastures throughout the Southeastern United States. The grass can harbor a fungal endophyte (Epichloë coenophiala) thought to provide the plant with enhanced resistance to biotic and abiotic stress. However, the alkaloids produced by the common variety of the endophyte cause severe animal health issues resulting in a considerable amount of research focused on eliminating the toxic class of alkaloids while retaining the positive abiotic and biotic stress tolerance attributes of the other alkaloids. In doing so, very little attention has been paid to the direct influence the fungal-plant symbiosis has on rhizosphere processes. Therefore, my objectives were to study the influence of this relationship on plant biomass production, root exudate composition, and soil biogeochemical processes using tall fescue cultivars PDF and 97TF1 without an endophyte (E-), or infected with the common toxic endophyte (CTE+), or with two novel endophytes (AR542E+, AR584E+). I found that root exudate composition and plant biomass production were influenced by endophyte status, tall fescue cultivar, and the interaction of cultivar and endophyte. Cluster analysis showed that the interaction between endophyte and cultivar results in a unique exudate profile. These interactions had a small but perceptible impact on soil microbial community structure and function with an equally small and perceptible impact on carbon and nitrogen cycling in soils from rhizobox and field sites. These studies represent the first comprehensive analysis of root exudate chemistry from common toxic and novel endophyte infected tall fescue cultivars and can be used to help explain in part the observed changes in C and N cycling and storage in pastures throughout the Southeast U.S..
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Akter, Pervin [Verfasser], Petr [Akademischer Betreuer] [Gutachter] Karlovsky, and Franz [Gutachter] Hadacek. "Plant Root Exudates : Variation between Species and Reaction to Water Deficit / Pervin Akter ; Gutachter: Petr Karlovsky, Franz Hadacek ; Betreuer: Petr Karlovsky." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2017. http://d-nb.info/1125105968/34.
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Valori, Federico. "Effects of root exudates on cadmium bioavailability in the rhizosphere : assessment of cadmium toxicity to plants and microorganisms, and soil remediation." Bordeaux 1, 2006. http://www.theses.fr/2006BOR13151.
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Des sols contaminés uniquement en Cd, depuis une longue période, ont d'abord été utilisés pour évaluer les effets d'exsudats racinaires de faible masse moléculaire, libérés dans un système modèle par un filtre placé à la surface du sol, sur les biomasses microbiennes carbonées et azotées, la respiration microbienne, le pool inorganique d'N et la biodisponibilité de Cd dans la rhizosphère (BIOMET®). L'utilisation d'une espèce végétale, Holcus lanatus L. , pour la phytoremédiation aidée de sols contaminés en Cd a été étudiée de façon préliminaire en solution hydroponique sur 4 semaines. Les plantes, dont le système racinaire a été lavé, ont été placées dans une solution nutritive simulant la concentration en Cd extrait et le pH des parcelles d'origine. La concentration et la quantité de Cd ont été quantifiées dans les parties aériennes, les feuilles et les racines. On a mesuré les activités enzymatiques Guaiacol peroxidase dans les feuilles, ainsi que leur densité en chlorophylle et caroténoïdes totaux. L'assainissement des sols contaminés en Cd a été étudié en utilisant une technique de stabilisation in situ basée sur l'apport au sol de l'un des 3 composés inorganiques suivants: beringite + grenailles d'acier, sépiolite, et bentonite. La concentration en Cd a été mesurée dans la solution du sol (Rhizon) au cours des premiers jours suivants l'amendement du sol et après 6 mois. L'efficacité de la remédiation des sols contaminés en Cd par stabilisation in situ a été évaluée en vase de végétation placés sous serre, avec 3 végétaux de sensibilité différente à l'exposition au Cd (sensible: Phaseolus vulgaris, moyennement tolérante: Holcus lanatus, tolérante: Lactuca sativa).
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au, A. Jayasekera@murdoch edu, and Arunodini Uthpalawanna Jayasekera. "Interactions between Phytophthora cinnamomiand Acacia pulchella: consequences on ecology and epidemiology of the pathogen." Murdoch University, 2006. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20061129.134500.
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Phytophthora cinnamomi is an important pathogen of many plant species in natural ecosystems and horticulture industries around the world. In Western Australia, a high proportion of native plant species are susceptible to P. cinnamomi attack. Acacia pulchella, a resistant legume species native to Western Australia has been considered as a potential biological control tool against P. cinnamomi. To develop effective control methods, it is important to understand the interactions between the control agent and the different life forms of the pathogen. In this thesis the interactions are investigated between P. cinnamomi and varieties of A. pulchella which occur in jarrah (Eucalyptus marginata) forest and sand plain ecosystems.
The soil inoculum of P. cinnamomi was compared under the potted plants of the three common varieties of A. pulchella, var. pulchella, var. glaberrima and var. goadbyi. These were grown in infected jarrah forest soil in the glasshouse and in vitro in a sterilised soil-less mix aseptically. Acacia urophylla (a species non suppressive towards P. cinnamomi) was also included as a control. An isolate of the most commonly found clonal lineage of P. cinnamomi in the jarrah forest, A2 type 1 was selected for use in experiments after testing showed it reliably produced zoospores and chlamydospores both axenically and in non-sterile conditions, in comparison to several other isolates. The lowest survival of P. cinnamomi inoculum was found under A. pulchella var. goadbyi plants grown both in non sterile soil and in aseptic soil-less mix.
All the life forms of P. cinnamomi were affected by A. pulchella (Chapters 2, 3, 4 and 5). The soil leachates from potted plants of A. pulchella var. goadbyi reduced sporangial production (Chapter 2) and caused cytoplasm collapse of chlamydospores (Chapter 3). The confirmation was obtained that soil under A. pulchella was inhibitory to sporangial stage of P. cinnamomi and new evidence was obtained on chlamydospore inactivation. Cytoplasm collapse in the chlamydospores was observed both for chlamydospores on mycelial discs on Mira cloth exposed to the soil leachate and within infected roots buried in soils under the three varieties of A. pulchella plants. The effect was strongest under the plants of A. pulchella var. goadbyi and indicated that the chlamydospores of P. cinnamomi are unlikely to act as persistent structures under A. pulchella var. goadbyi plants.
In Chapter 4, bioassays were conducted with axenically produced mycelia, chlamydospores and zoospores to test the inhibitory effect of the root exudates collected from aseptically grown A. pulchella var. goadbyi plants. The zoospores of the same isolate used in the soil leachate tests were immobilised (became sluggish and encysted) within one to two minutes. When incubated for 24 h, zoospores predominantly clumped and germ tubes were observed only from the clumped ones. Chlamydospores produced by four isolates of the common A2 type 1 strain and the only one A2 type 2 strain available at the time were tested. A higher percentage of chlamydospores collapsed and a very low percentage germinated after 24 h. Chlamydospores of all the A2 type 1 isolates were inhibited by the root exudates whilst the A2 type 2 isolate remained viable. The findings showed that the suppressive effect must be due at least in part to substances exuded by the A. pulchella plants. However, it appeared that the A2 type 1 isolates were more vulnerable to this effect than the single A2 type 2 isolate.
In Chapter 5, the effect of season on sporangial suppression of P. cinnamomi was shown using field soils collected from three jarrah forest soil vegetation types and a Banksia woodland on Bassendean sand, collected in winter and summer. The effect of age of A. pulchella plants was demonstrated using the soils collected from rehabilitated bauxite mine pits. In all the locations soils were collected under A. pulchella plants and 5 m away from the nearest A. pulchella. An effect of soil type was evident as whilst the soil leachates made from the three lateritic jarrah forest soil types where A. pulchella is common in the understorey were suppressive to the sporangial stage of P. cinnamomi, this effect was not evident in the Bassendean sand under A. pulchella. A. pulchella soils collected in winter were less suppressive towards sporangial production than soils collected in summer. An effect of plant age was demonstrated as soil leachates from four year-old A. pulchella stands in rehabilitated bauxite mine sites were more suppressive for sporangia than leachates from one year-old stands.
Further information on the behaviour of the pathogen in soil and in potting mix with and without A. pulchella was obtained by infecting lupin radicles with an isolate of each A2 type, 1 and 2 strains of P. cinnamomi and burying them in the soil under the three varieties of A. pulchella plants. After a week, the chlamydospores were mostly collapsed and hyphae deteriorated. Oospores were observed and in significant numbers under the potted plants of A. pulchella var. glaberrima.
Isolates of all three clonal lineages of P. cinnamomi found in Australian soil were tested for the ability to produce oospores. Two isolates of the A1 and A2 type 2 and three isolates of the common A2 type 1 were screened. The two isozyme types of the A2 clonal lineage isolated in Australia varied in ability to self and produce oospores in planta in several soils from the jarrah forest. The isozyme type 2 of the A2 clonal lineage of P. cinnamomi produced oospores under these experimental conditions. This stimulation was not effective for most of the tested isolates of the A2 type 1 and the A1 clonal lineage. The in planta oospores were viable but dormant and the oogonial-antheridial associations were amphigynous both in vitro and in vivo. For the first time it was established that, the stimulus for selfing and oospore formation in the A2 type 2 of P. cinnamomi is available in some jarrah forest soils, with and without A. pulchella and also in the potting mix used. This raises important questions for the management of the pathogen.
Several factors were identified as potential stimuli for selfing. Among them, soil nutrient levels and essentially enhanced sulphur presence were found important. Temperature also played a key role. Oospores were produced abundantly at 21 25 ºC but not over 28 ºC.
The biology of P. cinnamomi has been studied for several decades but some important aspects remain un-researched. This thesis pioneers research into the in planta selfing aspect of the pathogen in soil. It also improved the understanding of the interactions between P. cinnamomi and A. pulchella which to some extent supports use of A. pulchella as a biological control tool against P. cinnamomi. However, attention is drawn to the natural mechanisms of this complex pathogen to survive in planta by producing oospores, the most persistent form of its life cycle.
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Tato, L. M. "INTEGRATED RESPONSES OF A WILD SPECIES PARIETARIA JUDAICA (L. 1753) TO DIRECT AND INDUCED IRON DEFICIENCY GROWTH CONDITIONS." Doctoral thesis, Università degli Studi di Milano, 2013. http://hdl.handle.net/2434/218168.
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Iron (Fe) is an essential micronutrient in plants as it takes part in major metabolic pathways such as photosynthesis and respiration and is linked to many enzymes that accomplish many other cellular functions (DNA synthesis, nitrogen fixation, hormone production). Fe deficiency, a major abiotic stress, reduces crop yields, especially in calcareous soils in which the solubility of Fe is extremely low because of the high soil pH.
Parietaria judaica is a wild sinantropic Strategy I plant that implements many integrated mechanisms allowing to successfully complete the life cycle in highly calcareous environments.
In this work the main mechanisms by which P. judaica overcomes the low bioavailability of Fe have been identified. P. judaica was subject to direct and induced Fe deficiency growth conditions in hydroponic systems. Strategy I biochemical mechanisms of FeII-reduction and rhizosphere acidification were studied, as well as low organic acids and phenolics in root exudates. It was suggested that the accumulation and exudation of phenolic compounds plays a central role in the adaptive strategy of P. judaica to cope with Fe deficiency conditions.
Key enzymes of primary and secondary metabolism were assayed in order to identify the metabolic rearrangement that occurs under Fe deficiency conditions. The data analysed confirm that under Fe deficiency the metabolic rearrangement takes place by modifying allocation of carbon skeletons between primary and secondary metabolism. It was observed that secondary metabolism constitutes the main concern under this stress condition as P. judaica sustains the supply of substrates using non oxidative ways.
Phenolic composition was characterized by HPLC analyses in P. judaica focusing on phenolic composition changes due to low Fe availability. Phenolic compounds found in P. judaica belong mainly to the mono- and di- caffeoylchinic acids group. The chlorogenic acid was resulted the most sensible component under Fe deficiency stress.
Morphological and architectural modifications of root system were also analysed. P. judaica changes its root system according to the experimental treatment imposed. The differences found in direct and induced Fe-Deficiency conditions were oriented to increase the root contact surface with the medium. In particular, the root architecture reflected the plant nutritional status.
Comparing the data obtained from high bicarbonate and highly alkaline buffer conditions it was observed that P. judaica has no problems to acquire Fe in highly alkaline environments, suggesting that in a highly chalky environment the availability of bicarbonate itself constitutes the real factor of stress.
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McManus, Paul. "Rhizosphere Interactions Between Copper Oxide Nanoparticles and Wheat Root Exudate in a Sand Matrix; Influences on Bioavailability and Uptake." DigitalCommons@USU, 2016. https://digitalcommons.usu.edu/etd/5058.
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Copper oxide nanoparticles (NPs) are used in an expanding range of industries including a potential for agricultural applications as a fungicide. Accidental spills or misapplication of CuO NPs may lead to soil contamination. Plant roots exude a wide range of organic chemicals for bioprotection and to enhance bioavailability of nutrients. Many of these chemicals are metal chelators that may increase the solubility of CuO NPs, thus enhancing the impact of these NPs on plants. This work was directed towards understanding which plant exudates force increased solubility of CuO NPs and to determine if the level of NP in the growth matrix drives a feedback effect, regarding composition and quantity of exudates.
Wheat seedlings (Triticum aestivum cv Deloris) were grown in a sand matrix for 10 days after 3 days of germination. The sand was amended with sublethal doses of CuO NPs from 0 to 300 mg Cu/kg dry sand. Sand was selected as the solid growth matrix as a proxy for soil in terms of plant root morphology, mechanical impedance and water stress, while providing a low background of dissolved organic carbon for the isolation of root exudates. After plant growth, the pore water was collected from the sand by vacuum filtration and analyzed.
By coupling analytic techniques including Triple Quad Mass Spectroscopy and ion chromatography with geochemical modeling, we have identified citrate and the phytosiderophore, deoxymugineic acid (DMA) as chelators that drove the majority of dissolution of CuO NPs, especially DMA at higher CuO NP doses. Altered biogeochemistry within the rhizosphere was correlated with increased plant uptake of Cu and bio-response via exudate type, quantity and metal uptake. Exposure of wheat to CuO NPs lead to dose-dependent reduction in Fe, Ca, Mg, Mn and K in roots and shoots. This work is relevant to growth of commercially important crop wheat in the presence of CuO NPs as a fertilizer, fungicide or a pollutant.
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Kierul, Kinga [Verfasser], Rainer [Akademischer Betreuer] Borriss, Thomas [Akademischer Betreuer] Schweder, and Thomas [Akademischer Betreuer] Eitinger. "Comprehensive proteomic study of Bacillus amyloliquefaciens strain FZB42 and its response to plant root exudates / Kinga Kierul. Gutachter: Rainer Borriss ; Thomas Schweder ; Thomas Eitinger." Berlin : Humboldt Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2013. http://d-nb.info/1041284608/34.
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Kierul, Kinga [Verfasser], Rainer Akademischer Betreuer] Borriss, Thomas [Akademischer Betreuer] Schweder, and Thomas [Akademischer Betreuer] [Eitinger. "Comprehensive proteomic study of Bacillus amyloliquefaciens strain FZB42 and its response to plant root exudates / Kinga Kierul. Gutachter: Rainer Borriss ; Thomas Schweder ; Thomas Eitinger." Berlin : Humboldt Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2013. http://nbn-resolving.de/urn:nbn:de:kobv:11-100212224.
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Schreiber, Christina [Verfasser], Uwe [Akademischer Betreuer] Rascher, and Andreas [Akademischer Betreuer] Weber. "Rhizosphere dynamics of higher plants in the water fluctuation zone of Yangtze River : Root exudates and mass flow / Christina Schreiber. Gutachter: Uwe Rascher ; Andreas Weber." Düsseldorf : Universitäts- und Landesbibliothek der Heinrich-Heine-Universität Düsseldorf, 2011. http://d-nb.info/1015434738/34.
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Hassan, Ahmed Abdulla Mohamed. "The interactions between Yemeni wheat and barley cultivars and isolates of Cochliobolus sativus and the role of root exudates and toxins in susceptibility and pathogenicity." Thesis, University of Newcastle Upon Tyne, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299426.
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Javed, Muhammad Tariq. "Mechanisms behind pH changes by plant roots and shoots caused by elevated concentration of toxic elements." Doctoral thesis, Stockholms universitet, Botaniska institutionen, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-64324.
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Toxic elements are present in polluted water from mines, industrial outlets, storm water etc. Wetland plants take up toxic elements and increase the pH of the medium. In this thesis was investigated how the shoots of submerged plants and roots of emergent plants affected the pH of the surrounding water in the presence of free toxic ions. The aim was to clarify the mechanisms by which these plants change the surrounding water pH in the presence of toxic ions. The influence of Elodea canadensis shoots on the pH of the surrounding water was studied in the presence of cadmium (Cd) at low initial pH (4-5). The involvement of photosynthetic activity in the pH changes was investigated in the presence and absence of Cd. The cytosolic, vacuolar and apoplasmic pH changes as well as cytosolic Cd changes in E. canadensis were monitored. The influence of Eriophorum angustifolium roots on the pH of the surrounding water was investigated in the presence of a combination of Cd, copper, lead, zinc and arsenic at low initial pH (3.5). Eriophorum angustifolium root exudates were analyzed for organic acids. Elodea canadensis shoots increased the pH of the surrounding water, an effect more pronounced with increasing Cd levels and/or increasing plant biomass and increased plant Cd uptake. The pH increase in the presence of free Cd ions was not due to photosynthesis or proton uptake across the plasmalemma or tonoplast. Cadmium was initially sequestered in the apoplasm of E. canadensis and caused its acidosis. Eriophorum angustifolium roots increased the surrounding water pH and this effect was enhanced in the presence of arsenic and metals. This pH increase was found to depend partly on the release of oxalic acid, formic acid and succinic acid by the plants. In conclusion, E. canadensis shoots and E. angustifolium roots were found to increase the low initial pH of the surrounding water. The pH modulation by these species was enhanced by low levels of free toxic ions in the surrounding water.At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Submitted. Paper 3: Submitted. Paper 4: Manuscript.
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Fan, Ben [Verfasser], Rainer [Akademischer Betreuer] Borriss, Thomas [Akademischer Betreuer] Börner, and Rudolf [Akademischer Betreuer] Ehwald. "Plant colonization by GFP-labeled Bacillus amyloliquefaciens FZB42 and transcriptomic profiling of its response to plant root exudates / Ben Fan. Gutachter: Rainer Borriss ; Thomas Börner ; Rudolf Ehwald." Berlin : Humboldt Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2011. http://d-nb.info/1015016537/34.
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Jothimuthu, Preetha. "Environmentally-friendly disposable Lab-on-a-chip Sensor for Point-of-Care Measurement of Heavy Metals." University of Cincinnati / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1306518480.
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Marques, Anderson Cesar Ramos. "FIXAÇÃO BIOLÓGICA DE NITROGÊNIO E MICORRÍZAÇÃO EM GRAMÍNEAS DOS CAMPOS SULINOS." Universidade Federal de Santa Maria, 2014. http://repositorio.ufsm.br/handle/1/4869.
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Empresa Brasileira de Pesquisa AgropecuáriaThe knowledge of the level of association that occurs between diazotrophic bacteria and fungi arbusculares mycorrhizae (AMF) in grassland ecosystems may be important for the understanding of the changes caused by the addition of fertilizers containing phosphorus (P) and nitrogen (N), in the production and botanical composition of natural pastures. The objective of this study was to evaluate. (a) the occurrence of three genera of diazotrophic bacterial in the root system under fertilization with N and P, and determine the contribution of N via BNF, and (b) evaluate the behavior of the association between AMF and native grasses. Four most abundant grasses in natural grasslands of the Southern Campos in Rio Grande do Sul , Axonopus affinis, Paspalum notatum, Andropogon lateralis and Aristida laevis were grown in pots of 5 kg, in a greenhouse, two studies being conducted (A e B ). In A, two treatments were applied: 50 mg kg-1 soil P and 100 mg kg-1 of soil N (NP) and a control, being evaluated, the number of diazotrophic bacteria of the genera Azotobacter, Azospirillum and Herbaspirillum, and the contribution of BNF was determined by the technique of natural 15N abundance. In B, the treatments consisted of applying 50 mg kg-1 soil P (P), application of 50 mg kg-1 soil P and 100 mg kg-1 of soil N (NP), and a control, in both treatments mycorrhizal colonization was determined. For A, A. laevis demonstrate to be more dependent on biological N fixation than the other species. The grass P. notatum compared with other species demonstrated to be more efficient to absorb available soil N. The dry matter accumulation in shoots of the native species was higher with the application of NP. In B the mycorrhizal colonization was similar between the control, P and NP to the roots of A. lateralis and A. laevis, thus presenting a greater dependence on the mycorrhizal association. Differently, in A. affinis and P. notatum, the mycorrhizal colonization was lower when subjected to fertilization with P and NP, thus presenting a lower dependence. It is concluded for A that fertilization with N and P reduces diazotrophic colonization, increasing the production of dry matter and N content of the tissue. A. laevis showed the highest contribution of biological nitrogen fixation, since P. notatum showed higher N accumulation in soil. In relation to B, A. laevis and A. lateralis have a higher dependence on the mycorrhizal than A. affinis and P. notatum.
O conhecimento do nível de associação que ocorre entre bactérias diazotróficas e fungos micorrízicos arbusculares (FMA) nos ecossistemas campestres, pode ser importante para a o entendimento das alterações provocadas pela adição de fertilizantes, contendo fósforo (P) e nitrogênio (N), na produção e na composição botânica das pastagens naturais. O objetivo do presente trabalho foi avaliar (a) a ocorrência de três gêneros de bactérias diazotróficas no sistema radicular sob fertilização com N e P, e determinar a contribuição de N via FBN, e (b) avaliar o comportamento da associação entre FMAs e gramíneas nativas. Foram utilizadas quatro gramíneas de maior abundância nas pastagens naturais dos Campos Sulinos no Rio Grande do Sul, Axonopus affinis, Paspalum notatum, Andropogon lateralis e Aristida laevis, cultivadas em casa de vegetação, sendo conduzidos dois estudos (A e B). Em A, foram aplicados dois tratamentos: 50 mg kg-1 de solo de P + 100 mg kg-1 de N solo (NP) e uma testemunha, sendo avaliados, o número de bactérias diazotróficas dos gêneros Azotobacter, Azospirillum e Herbaspirillum, e a contribuição da FBN através da técnica da abundância natural de 15N. Em B, os tratamentos consistiram na aplicação de 50 mg kg-1 de solo de P (P); aplicação de 50 mg kg-1 de solo de P + 100 mg kg-1 de N solo (NP), e uma testemunha, em ambos foi determinada a colonização micorrízica. A espécie A. laevis demonstrou ser mais dependente da fixação biológica de N que as demais espécies. A espécie P. notatum em comparação as demais espécies, demostrou ser mais hábil em absorver o N disponível no solo. A matéria seca acumulada da parte aérea das espécies nativas foi maior com a aplicação de NP. A colonização micorrízica foi semelhante entre a testemunha, P e NP para as raízes de A. lateralis e A. laevis, apresentando assim uma maior dependência da associação micorrízica. Diferentemente, nas espécies A. affinis e P. notatum, a colonização micorrízica foi menor quando submetidas a adubação com P e NP, apresentando assim uma menor dependência. Conclui-se assim, que a adubação com N e P reduz a colonização de bactérias diazotróficas, aumentando a produção de matéria seca e teor de N no tecido. A. laevis apresentou a maior contribuição da fixação biológica de nitrogênio, já P. notatum apresentou maior acúmulo de N do solo. As espécies A. laevis e A. lateralis apresentam maior dependência da micorrização que as espécies A. affinis e P. notatum.
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Neuschütz, Clara. "Phytostabilization of mine tailings covered with fly ash and sewage sludge." Doctoral thesis, Stockholms universitet, Botaniska institutionen, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-8452.
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Establishing plant communities is essential for the restoration of contaminated land. As potential cover materials, fly ash and sewage sludge can prevent formation of acid mine drainage from sulfidic mine waste. The aim of the thesis was to i) screen for plants that can be established in, and prevent leakage of metals and nutrients from sludge on top of ash and tailings, and ii) investigate root growth into sealing layers of ash and sludge. Analyses were performed under laboratory, greenhouse and field conditions using selected plant species to examine the release of Cd, Cu, Zn, N, and P from the materials. Plant physiological responses and interactions with fly ash were also investigated. The data show that plants can decrease metal and nutrient leakage from the materials, and lower the elemental levels in the leachate, but with varying efficiencies among plant species. Plants capable of taking up both nitrate and ammonium were more efficient in preventing N leakage compared with those taking up primarily ammonium. Fast growing plants could raise the pH in acidic sludge leachate, but the initial pH decrease and N leakage was not counteracted by plants. Germination in fresh sludge was problematic, but enhanced by aeration of the sludge. In general, the accumulation of metals in plant shoots was low, especially if ash was located below the sludge. Fresh ash was phytotoxic (e.g., high alkalinity, salinity and metal levels) and induced the activity of stress-related enzymes in shoots. In sealing layers of aged and cured ash, roots could grow if the penetration resistance was low, or into the surface of stronger layers if the surface had become pulverized. The roots caused dissolution of calcium-rich minerals, possibly by exudation of saccharides. Addition of sludge to an ash layer increased root growth, likely due to decreased bulk density and pH, and nutrient addition. In conclusion, with selected plant species and a properly constructed cover, metal and nutrient leaching from the materials and root growth into the sealing layer can be restricted.
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Santos, Paulo Cézar das Mercês. "Phytophthora nicotianae: ação de meios de cultura e da qualidade da luz no crescimento e esporulação e aspectos fisiológicos e bioquímicos da interação com porta-enxertos cítricos." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/11/11135/tde-05012016-105803/.
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A citricultura brasileira apresenta números bastante significativos e expressivos, refletindo a grande importância social e econômica que essa atividade agrícola e industrial tem para a economia do país. O Brasil se destaca como o maior produtor de laranja do mundo. As plantas cítricas podem ser produzidas e multiplicadas de várias formas e a enxertia é a forma de propagação vegetativa mais utilizada comercialmente no Brasil. Dentre os porta-enxertos mais empregados, sobressaem-se o citrumeleiro Swingle e a tangerineira Sunki. Apesar das vantagens presentes nesses dois genótipos, a produção deles está sendo limitada por doenças causadas por fungos e estraminipilas. Em citros, as diversas espécies de Phytophthora são responsáveis pelas doenças gomose e podridões, principalmente de radicelas. P. nicotianae é a espécie que mais afeta as plantas cítricas no Brasil. Não obstante a grande importância de P. nicotianae para os porta-enxertos, alguns mecanismos de resistência ou susceptibilidade ainda requerem mais investigações cientificas. O presente trabalho visa a elucidação de alguns mecanismos de resistência dos citros a P. nicotianae, por meio de estudos fisiológicos e bioquímicos dos porta-enxertos, além da ação de meios de cultura e da qualidade da luz no estudo da fisiologia desse estraminipila. Para isso realizou-se a detecção de alguns equivalentes de compostos fenólicos através da técnica HPLC e o comportamento do genótipo resistente frente à possível inibição da síntese de compostos fenólicos através do tratamento das raízes do porta-enxerto Swingle com Pro-Ca; avaliou-se a atração de zoósporos de P. nicotianae por exsudatos radiculares provenientes dos dois porta-enxertos com o uso de uma armadilha adaptada; verificou-se o comportamento do zoósporo, a motilidade e a zoosporogênese frente à ação de vários compostos fenólicos e testou-se a ação de diferentes meios de culturas e da qualidade da luz no crescimento micelial e na esporulação de P. nicotianae. Os resultados revelaram que a tangerineira Sunki possui maiores quantidades de equivalentes em apigenina que o citrumeleiro Swingle nos dois períodos de avaliação, para o HPLC. O porta-enxerto resistente apresentou mais equivalentes de ácido clorogênico que o genótipo susceptível. Quanto ao Pro-Ca, os equivalentes de compostos fenólicos em raízes de plântulas do citrumeleiro Swingle não diferiram daquelas plantas tratadas com água. O Pro-Ca não inibiu e não desativou a síntese de compostos fenólicos. O uso do anticorpo contra a elicitina \"α-plurivorina\" teve resultados intermediários no consumo de água por plântulas de tangerineira Sunki e a atividade zoosporicida dos compostos fenólicos apresentou resultados variáveis no comportamento da motilidade de zoósporos. Os compostos fenólicos escopoletina e tricetinpentametoxi conseguiram paralisar a motilidade e proporcionaram as menores porcentagens de zoosporogênese. O meio de cultura AA permitiu a maior TCMD, seguido de CA e V8-CaCO3-Ágar. Os maiores valores de esporulação foram encontrados nesses dois últimos meios, respectivamente. Todas as faixas de luzes (e a ausência de luz) estudadas no presente trabalho podem ser avaliadas para o crescimento micelial, porém o tratamento claro foi aquele que mais induziu a esporulação de zoósporos de P. nicotianae.The Brazilian citrus industry has very significant and expressive numbers, reflecting the great social and economic importance of this industrial and agricultural activity has for the economy. Brazil stands out as the world\'s largest orange producer. Citrus plants can be produced and multiplied in various ways and the bud is the form of vegetative propagation more commercially used in Brazil. Among the most commonly used rootstocks, stand up the Swingle citrumelo and Sunki mandarin. Despite the advantages these two genotypes present, their production is being limited by diseases caused by fungi and estraminipilas. In citrus, all species of Phytophthora are responsible for diseases gummosis and fibrous root rot, especially. P. nicotianae is the kind that affects citrus plants in Brazil. Regardless of the great importance of P. nicotianae for rootstocks, some mechanisms of resistance or susceptibility still require further scientific investigation. This study aims to elucidate some mechanisms of resistance of citrus to P. nicotianae, through physiological and biochemical studies of rootstocks, beyond of action culture media and quality of light in the physiological study of this estraminipila. To this was carried out to detect certain equivalent of phenolic compounds by HPLC and genotype resistant behavior against the possible inhibition of the synthesis of phenolic compounds by treatment of the roots of Swingle rootstock with Pro-Ca; evaluated the zoospores attraction P. nicotianae by exudates from the two rootstocks using an adapted trap; it was the zoospore behavior, motility and zoosporogenesis to the action of various phenolic compounds and tested the action of different culture media and quality of light on mycelial growth and sporulation of P. nicotianae. The results for HPLC revealed that Sunki mandarin has larger amounts of apigenin equivalents Swingle citrumelo in that the two periods. The sturdy rootstock had more chlorogenic acid equivalents of the susceptible genotype. As for the Pro-Ca equivalent of phenolic compounds in Swingle seedling roots not differ from those plants treated with water. The Pro-Ca not inhibited and not disabled the synthesis of phenolic compounds. The use of the antibody against elicitin \"α-plurivorin\" had intermediate results in water consumption by Sunki mandarin seedlings and zoosporicide activity of phenolic compounds showed variable results in the behavior of zoospore motility. The scopoletin and tricetinpentametoxi phenolic compounds managed to paralyze the motility and provided the smallest percentages of zoosporogenesis. The culture medium AA allowed greater DMGR, followed by CA and V8-CaCO3-Agar. The highest sporulation values were found in the last two media, respectively. All lights tracks (and the absence of light) studied in this work can be evaluated for mycelial growth, but the treatment light was that more induced sporulation of zoospores of P. nicotianae.
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Carreras, Alexis. "Caractérisations biochimique et microscopique du piège extracellulaire de racine et des exsudats racinaires de trois essences ligneuses sahéliennes : balanites aegyptiaca D., Acacia tortilis subsp. raddiana S., et tamarindus indica L." Thesis, Normandie, 2018. http://www.theses.fr/2018NORMR017.
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La coiffe racinaire est cruciale à la croissance et survie du méristème subapical de racine. Elle libère des cellules frontières (CFs) qui assurent la protection de l’apex racinaire. Les CFs associées à leur mucilage forment le piège extracellaire de racine (RET). La caractérisation du RET et des exsudats racinaires de trois essences ligneuses sahéliennes à partir de plantules cultivées in vitro a été réalisée. B. aegyptiaca et A. raddiana prospèrent dans les zones semi-arides, à l’opposé de T. indica. La morphologie des CFs et l’organisation du RET ont été déterminées par microscopie. La compostion en glycopolymères et la détection des arabinogalactanes proteines (AGPs) dans le RET et les exsudats racinaires ont été déterminées par des analyses biochimiques. L’effet des exsudats racinaires sur la croissance d’Azospirillum brasilense, une bactérie bénéfique pour la plante a été évalué. B. aegyptiaca produit des CFs de type border cells (BCs) alors que les autres Fabaceae produisent des BCs et des border-like cells. Les BCs sont entourées d’un dense mucilage riche en polymères de paroi. Le RET et les exsudats racinaires issus de B. aegyptiaca et A. raddiana sont plus riches en AGPs que ceux provenant T. indica. Les AGPs pourraient contribuer à la survie des plantules dans un contexte semiaride. Ce travail ouvre de nouvelles perspectives de recherche concernant l'implication du RET dans la survie des plantes à l'ariditéThe root cap is primordial for seedling growth and supports root apical meristem integrity. The root cap releases root border cells (RBCs) that surround the root tip and ensure seedling protection against numerous stresses. RBCs and their associated mucilage form the root extracellular trap (RET). Here, RET and root exudate characterization of three Sahelian woody seedlings are performed. In contrast to B. aegyptiaca and A. raddiana which thrive in semi-arid areas, T. indica is more sensitive to drought. B. aegyptiaca, A. raddiana and T. indica seedlings were sub-cultured in vitro. RBC morphologies and RET organization were determined using microscopic approaches. The polysaccharide composition and arabinogalactan protein (AGP) content were determined by biochemical approaches in the RET and the root exudates. Moreover, the effect of root exudates on the growth of Azospirillum brasilense a plant benefical bacteria has been performed. While B. aegyptiaca produces only border cell (BC) type, the two Fabaceae seedlings release both BCs and border-like cells (BLCs). BCs are enclosed in a dense mucilage enriched in cell wall polymers. Compared to T. indica, RET and root exudates of B. aegyptiaca and A. raddiana include more abundant AGPs. In this context, AGPs could contribute to woody seedling survival. This work opens new research perspectives regarding involvement of RET in plant survival to aridity
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Williams, Alan. "Effect of legume root exudate on attachment and biofilm formation by Rhizobium leguminosarum." Thesis, University of East Anglia, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.439894.
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Crane, Cynthia Elizabeth. "Investigation of the Interactions Among Grass, Chlorophenols and Microbes." Diss., Virginia Tech, 1999. http://hdl.handle.net/10919/28194.
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Studies were conducted to explore the interactions among rye grass, chlorophenols and microorganisms. The objectives were to examine some of the processes by which plants affect the fate of subsurface organic contaminants. The research was divided into three studies: interactions between live grasses and 2,4-dichlorophenol (DCP), 2,4,6-trichlorophenol (TCP), and pentachlorophenol (PCP); physico-chemical interactions between the three chlorophenols and root tissue; and effect of root exudates on biodegradation of TCP.
To study the interactions between plants and organic contaminants, rye grass plants were grown in solutions containing DCP, TCP or PCP for one to three weeks. The grass removed substantial amounts of the chlorophenols throughout the incubation time. The majority of each chlorophenol removed from solution could not be recovered by non-destructive solvent extraction. The removal of the chlorophenols from solution and the unrecoverability of the removed compound followed different kinetics, indicating that the two are different processes. Both contaminant removal and unrecoverability were closely related to root surface area but not to transpiration. A qualitative model was developed to describe the uptake of organic contaminants by plants. The data demonstrate the importance of physico-chemical interactions between contaminants and roots and suggest that maximization of root surface area should be one consideration when selecting a plant species for phytoremediation.
To study the physico-chemical interactions between plant roots and organic contaminants, the distribution of DCP, TCP and PCP within a three phase system was examined. The three phases were severed grass roots, water and an organic solvent, either hexane or ethyl acetate. The chlorophenol mass that partitioned into the solvent phase was inversely correlated with root mass and root surface area index. Partition coefficients calculated with respect to the organic liquid phase were inversely correlated with root mass and root surface area index. A similar partitioning experiment was conducted using PCP placed in a solution containing only the dissolved organic material released by roots. These resulting partition coefficients decreased with increasing organic carbon concentration. It appeared that the organic compounds released into solution by the roots affected the movement of the chlorophenol into the organic liquid phase. It is proposed that the presence of roots simultaneously promoted retention of the chlorphenols in the aqueous phase and provided a sorption site.
The effect of grass root exudates and glucose on the lag time associated with 2,4,6-trichlorophenol (TCP) degradation by an unacclimated microbial inoculant and an acclimated microbial inoculant was investigated. The presence of an alternate organic carbon source reduced lag time for both the acclimated microbial inoculant and the inoculant that had not been previously exposed to chlorinated phenols. The lag time for acclimation of microbes to TCP mineralization was affected by the ratio of the alternate organic carbon source concentration to the biomass concentration. It is proposed that the presence of a readily available, alternate organic carbon source affected lag time through promotion of microbial population growth and provision of a preferred source of carbon and energy.
The results indicate that rye grass may directly, through partitioning and uptake, and indirectly, through soil microbes, affect the fate of chlorophenols in the subsurface environment.Ph. D.
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Steele, Helen. "Influence of inoculation upon flavonoid profiles in Lotus pedunculatus roots and exudate." Thesis, Queen's University Belfast, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318737.
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Rogers, Craig David. "Ecological and molecular investigation of wheat bulb fly (Delia coarctata, Fallén, Diptera : Anthomyiidae) for the advancement of population monitoring and control methodologies." Thesis, University of Edinburgh, 2012. http://hdl.handle.net/1842/6267.
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Wheat bulb fly (WBF) (Delia coarctata, Fallén, Diptera: Anthomyiidae) is a pest of commercial importance in cereal crops. Control is dependent on organophosphates some of which are restricted in the UK, while current oviposition monitoring techniques are labour intensive and subjective. Eggs are not laid in association with a host-plant, therefore, prompt location of a suitable host is critical to the survival of the newly hatched larvae. Wheat bulb fly larvae have been shown to exhibit a positive chemotactic response to wheat and other host-plant seedlings and their root exudates. The objective of this study was to improve the control and population monitoring methodology associated with WBF, by investigating the ecology and specifically the chemical ecology of the WBF. Bioassays were used to investigate the behavioural response of WBF to known chemical constituents of host-plant exudates. Four secondary metabolites were found to be attractive while CO2 was found to alter the behaviour of larvae. Wheat bulb fly oviposition was assessed in field situations to describe egg laying spatially and through time. Geostatistical and ecological techniques were used to observe the spatial dependence and dispersion of oviposition and construct contour maps or scale-sized dot graphs of oviposition density. The traditional single line transect sampling pattern was compared against a more intensive sampling regime. Oviposition monitoring was conducted over a three year period to ascertain the time of peak egg density of this fly. A molecular based diagnostic test to assess WBF egg populations for damage forecasting was developed. A real time polymerase chain reaction (PCR) protocol was produced to estimate field populations of WBF eggs through the quantification of eggs from field samples. In addition endpoint PCR was used to identify the presence or absence of eggs from samples. This study gives the potential to advance current control methodology by providing the basis for the development of a lure and kill or confusion/disruption strategy, while offering a more accurate sampling system and a molecular diagnostic test, for improvement of the management of WBF.
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Laloum, Yohana. "La Pourriture racinaire du pois : éléments de compréhension du processus infectieux d'A. euteiches et perspectives agronomiques." Thesis, Normandie, 2017. http://www.theses.fr/2017NORMR094.
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Dans l’objectif de redynamiser la culture des protéagineux, il est primordial d’améliorer la gestion du risque lié à Aphanomyces euteiches, agent responsable de la pourriture racinaire du pois. Le manque de connaissances sur les mécanismes d’infection d’A. euteiches constitue un frein à l’élaboration de stratégies de contrôle durable. Dansl’optique d’étudier les premières étapes du processus infectieux d’A. euteiches, laconstruction d’une souche A. euteiche-GFP a été entreprise. Transfecter A. euteiches aura permis d’assurer (i) la production de protoplastes par digestion enzymatique du mycélium puis (ii) d’insérer le gène gfp par la méthode de transfection chimique PEG-CaCl2 et (iii) de constater l’insertion stable du gène gfp dont l’expression s'est avérée transitoire. En parallèle, dans l’objectif d’apporter des éléments de réponses quant aux rôles des exsudats racinaires et du Root Extracellular Trap (RET) dans les réactions de défense du pois, une étude comparée des interactions entre Pisum sativum (plante sensible) et Vicia Faba (plante tolérante) au pathogène A.euteiches a été réalisée durant les premières phases de l’infection. Alors que de nombreuses variations au niveau de la composition polysaccharidique du RET et des exsudats ont été observées chez le pois, la féverole a présenté des modifications marginales. Chez le pois, l’infection est intense et rapide alors qu’elle semble réduite chez la féverole. La féverole repousse les zoospores tandis que le pois infecté les attire davantage. La féverole semble pouvoir protéger le pois au travers de mécanismes de communication qu’il convient de caractériser. L’ensemble de ces résultats semblent prometteurs dans le développement de méthode de lutte contre la pourriture racinaire du pois. Enfin, l’étude des propriétés bio-physico-chimiques des sols susceptibles de conditionner l’apparition de la maladie ont permis de confirmer la corrélation positive entre la densité d’inoculum du pathogène et le potentiel infectieux (PI) dans des sols naturellement infestés : les sols possédant des teneurs élevées en sable ou en calcium s'avèrent défavorables au développement de la maladie. Cette étude a aussi permis de mettre en évidence une influence possible des communautés microbiennes des sols, susceptibles d’influencer le processus infectieux d’A.euteichesAphanomyces euteiches is a pathogenic oomycete considered to be the most damaging root disease of pea crops in the world and there is currently no registered pesticide for its control. Crop management is the most efficient tool to control root rot, and avoidance of infested soil seems to be the optimal solution. Mechanisms related to A. euteiches root colonization remain poorly understood. In order to better understand A.euteiches infectious cycle, a polyethylene glycol (PEG) – calcium chloride (CaCl2) transformation protocol has been perfected in order to stably express the reporter gene GFP. The data show for the first a transient expression of green fluorescent protein (GFP) which can be observed in A.euteiches mycelium, a Saprolegnia oomycete. Vector pGFPN, containing the ham34 promoter and terminator of the Peronospora oomycete Bremia Lactucae, was introduced in A.euteiches protoplasts. Transient expression of GFP could be observed in A. euteiches mycelium by confocal microscopy. qPCR analyses confirmed the actual gfp gene insertion in its genome. Meanwhile, the influence of both pea and faba bean root extracellular trap (RET) and root exudates has been explored for A. euteiches zoospores by chemotaxis assays, microscopic observations and oomycete DNA quantification. Reciprocally pea and faba bean roots responses to A. euteiches infection have been studied at early stage of infection by biochemical analysis of cell wall polymer content in the RET and root exudates. Whereas infected pea root exudates stimulated A.euteiches zoospores attraction, faba bean exudates had a repellent effect on zoospores. In response to infection, arabinogalactan protein content of root pea exudates was altered. Interestingly, A.euteiches colonization was less intense on faba bean root surface and protect pea root at early stage of infection. Finally, the correlation between inoculum quantity in infested and the inoculum potential (IP) in field has been confirmed by qPCR. Analyses of the influence of abiotic soil parameters on the disease showed that a high calcium concentration or sand content negatively impact the IP. Furthermore, microbial communities proved to play a role in the expression of the disease in some soils. Metagenomics could be applied in order to provide new directions in managing this disease
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Friberg, Hanna. "Persistence of Plasmodiophora brassicae : influence of non-host plants, soil fauna and organic material /." Uppsala : Dept. of Entomology, Swedish University of Agricultural Sciences, 2005. http://epsilon.slu.se/2005115.pdf.
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Rezgui, Cyrine. "Etude du potentiel d'introduction de la culture du pois d'hiver dans les successions culturales en Normandie : conséquences sur les communautés microbiennes du sol et les flux d'azote Impacts of the winter pea crop (instead of rapeseed) on soil microbial communities, nitrogen balance and wheat yield Quantification et analyse des exsudats racinaires de pois, de blé et de colza : mise au point d’une méthodologie de collecte des exsudats racinaires N rhizodeposition quantification and root exudates characterization of pea (Pisum Sativum L.), rapeseed (Brassica napus L.) and wheat (Triticum aestivum L.) under controlled conditions Linking soil microbial community to C and N dynamics during crop residues decomposition." Thesis, Normandie, 2020. http://www.theses.fr/2020NORMR047.
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La transition agroécologique vise la triple performance agronomique, écologique et sociétale des exploitations agricoles. Un certain nombre de pratiques agricoles permet d’envisager la construction et le développement de systèmes de culture répondant à ces contraintes. Les légumineuses, par leur capacité à fixer l’azote atmosphérique, sont une alternative intéressante aux intrants azotés. Outre l’absence de fertilisation lors de leur culture, elles fournissent de l’azote à la culture suivante. Il existe cependant un manque de références sur certaines légumineuses à graines et notamment la culture du pois d’hiver. En effet, si des données acquises dans différentes régions françaises sont disponibles, aucune référence n’a été publiée pour la Normandie où la culture du pois d’hiver connaît un récent regain d’intérêt. Cette thèse propose d’évaluer, sur une période de deux ans, l’effet du remplacement du colza par le pois d’hiver en tête de rotation en réalisant une analyse comparative de ces deux successions (pois d’hiver-blé et colza-blé). L’objectif était d’évaluer l’effet de ce changement de tête de rotation (pois d’hiver vs colza) sur l’état biologique du sol et les flux d’azote à différentes échelles spatiotemporelles. Les résultats ont révélé une forte variabilité spatio-temporelle dans la réponse des communautés microbiennes du sol, et mis en évidence l’importance du contexte pédoclimatique dans le déterminisme de l’abondance et de l’activité des communautés microbiennes du sol. Ils ont montré par ailleurs, l’effet positif du pois d’hiver sur la disponibilité de l’azote minéral au cours du cycle cultural et pour les cultures suivantes, ici le blé puis l’orge. Les apports d’azote minéral dans le sol lié à la contribution des parties racinaires via la rhizodéposition et à la dégradation des résidus de culture après récolte ont été évalués au cours de ce travail de thèse. En effet, si la rhizodéposition s’est révélée plus importante sous pois d’hiver, elle n’a pas eu d’impact significatif sur les communautés microbiennes rhizosphériques. Contrairement à ces observations, la dégradation des résidus de culture a significativement modifié la composition des communautés bactériennes en lien avec leur composition biochimique initiale. La succession culturale incluant le pois a enrichi le sol en azote minéral mais des risques de perte d’azote par lixiviation de l’ordre de 23 kg N. ha-1 ont été estimés. Ces constats soulignent l’importance d’adapter la conduite des systèmes de culture incluant le pois d’hiver, en limitant les pertes d’azote par lixiviation et en maximisant son utilisation par les cultures suivantes. Les résultats de ces travaux ont confirmé la diminution des quantités d’engrais azoté utilisées dans la succession contenant le pois, sans préjudice de productivité, ni pour le pois, ni pour la culture suivante, ici, le blé. Finalement, introduire le pois d’hiver dans la rotation de culture en région Normandie, semble permettre de répondre à la problématique d’augmentation du coût des intrants, et aux enjeux de transition agroécologique et d’autonomie protéique régionaleThe agroecological transition targets triple agronomic, ecological, and societal performance of farms. Some new agricultural practices had emerged to develop a new cropping system to respond to these constraints. Legumes constitute an interesting alternative. Indeed, legumes are advantageous for soils due to their symbiotic relationship with nitrogen-fixing bacteria. The presence of compatible rhizobia combined to nitrogen-limited conditions promotes symbiosis which is the most efficient way for legumes to acquire more nitrogen. Compared with non-nodulated plants, symbiosis provides a competitive advantage by increasing soil nitrogen pool. However, some grain legumes, notably winter pea, are rarely studied, especially in the Normandy region where no reference has been published for this crop. The objective of this study is to compare two crop successions for a period of two years (winter pea-wheat and rapeseed-wheat), in order to assess the effect of replacing rapeseed by winter pea at the head of the rotation .We evaluated the effect of these two crops (winter pea vs rapeseed) on the biological state of the soil and nitrogen fluxes at different spatio-temporal scales. The results showed a significant spatio-temporal effect on the response of soil microbial communities and highlighted the importance of the pedoclimatic context in determining the abundance and activity of soil microbial communities. A positive effect of winter pea has been demonstrated on the availability of mineral nitrogen during the crop cycle and for following crops (wheat and barley). The supply of nitrogen to the soil is linked to the rhizodeposition of nitrogen via plants roots and the degradation of crop residues after harvest. Our results showed that winter pea exhibited the greatest amount of nitrogen rhizodeposition. However, rhizodeposition did not have a significant impact on rhizospheric microbial communities. Contrary to these observations, the degradation of crop residues significantly modified the composition of bacterial communities linked to their initial biochemical composition. Crop succession including winter pea enriched the soil with mineral nitrogen but simulation with STICS software revealed a nitrogen leaching around of 23 kg N. ha-1 during the cropping cycle. These findings underline the importance of adapting an adequate crop management system, including winter pea, to limit nitrogen losses. The results showed also that wheat yields after winter pea without the use of nitrogen fertilizers were equivalent to those obtained after rapeseed. However, rapeseed required significant nitrogen fertilization. Including winter pea in crop rotation in Normandy region may be a key to enhance productivity, to respond to the challenges of agroecological transition, regional protein autonomy, and to reduce environmental and economic costs, by reducing notably, the costs of fertilizers production and uses
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Lapie, Clémentine. "Caractérisation de la rhizodéposition du maïs (Zea mays L.) en réponse à la présence d’hydrocarbures aromatiques polycycliques et d’éléments traces métalliques." Electronic Thesis or Diss., Université de Lorraine, 2019. http://www.theses.fr/2019LORR0237.
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Cette thèse porte sur le fonctionnement de la rhizosphère dans un contexte de végétalisation de sols contaminés. Nous avons évalué l’impact de contaminants modèles (phénanthrène et cadmium) sur la rhizodéposition du maïs (Zea mays L.), afin de mieux comprendre le rôle joué par la rhizodéposition dans la tolérance de la plante à ce type de stress abiotique. Pour cela, un dispositif de culture et de collecte des rhizodépôts permettant d’évaluer la réponse du maïs à une exposition aux polluants a été mis en place. Ce développement méthodologique s’est attaché en particulier à mettre les plantes dans des conditions amenant à un fonctionnement aussi proche que possible de celui de conditions de culture normales dans un sol, tout en permettant la collecte des deux principales familles de rhizodépôts : les exsudats racinaires et le mucilage. Des outils de caractérisation des rhizodépôts récoltés ont été développés (analyses colorimétriques, LC-MS, GC-MS) afin de doser les principales familles de composés émis par les racines telles que les glucides, les acides aminés, les protéines et les acides organiques. Enfin, les rôles connus des molécules mises en évidence dans les expériences précédentes sur la dynamique des polluants ont été discutés. Cette étude a permis de mettre en évidence des modifications du profil métabolique de la rhizodéposition en présence de polluants et ce de façon différenciée selon qu’il s’agissait de polluants organiques ou métalliques. La présence de Cd entraine chez le maïs une diminution globale des composés émis par les racines (carbone total, glucides, acides aminés). Seules les protéines ne semblent pas être affectées par la présence du métal tandis que l’exsudation d’acides organiques augmente avec l’exposition au Cd. Le phénanthrène, quant à lui, entraîne une augmentation du carbone exsudé alors qu’il entraîne au contraire une diminution du carbone secrété dans le mucilage. De plus, il induit une augmentation de l’émission des glucides simples et polymérisés, des acides gras et des protéines tandis qu’il entraîne une baisse de la diffusion d’acides organiques. En plus de la présence de polluants, le développement du maïs a été étudié en analysant parallèlement sa rhizodéposition aux stades 4, 6 et 8 feuilles. L’effet du Cd sur l’exsudation semble s’accentuer à partir du stade 6 feuilles tandis que celui du phénanthrène tend au contraire à s’atténuer. L’influence des polluants sur le mucilage semble en revanche moins marquée et plus constante au cours du temps. Enfin, de nombreuses molécules rhizodéposées ont été identifiées comme pouvant jouer un rôle dans la dynamique des polluants dans le sol et par conséquent leur tolérance par la plante, notamment au travers des mécanismes de complexation ou de solubilisationThis thesis focuses on the functioning of the rhizosphere in the context of revegetation of contaminated soils. We evaluated the impact of model contaminants (phenanthrene and cadmium) on maize (Zea mays L.) rhizodeposition to better understand the role of rhizodeposition in the plant's tolerance to this type of abiotic stress. To this end, a system of plant cultivation and rhizodeposit collection was set up to assess the response of maize to pollutant exposure. Our methodological development aimed at placing the plants in conditions as close as possible as those of soil cultivation, while allowing the collection of the two main families of rhizodeposits: root exudates and mucilage. Tools for characterizing the collected rhizodeposits were developed (colorimetric analyses, LC-MS, GC-MS) in order to determine the main families of compounds emitted by roots such as carbohydrates, amino acids, proteins and organic acids. Finally, the role of the molecules highlighted in our experiments on pollutant dynamics was discussed. This study revealed changes in the metabolic profile of rhizodeposition in presence of pollutants and those differences may vary considering the nature of the pollutant (organic or metallic). Cd caused a decrease of almost all compound emissions by maize roots (total carbon, carbohydrates, amino acids). Only proteins did not appear to be affected by the presence of the metal, while the exudation of organic acids increased with Cd exposure. Phenanthrene, on the other hand, increased the quantity of exuded carbon while it decreased the carbon secreted in the mucilage. In addition, it induced an increase in the emission of simple and polymerized carbohydrates, fatty acids and proteins while diffused organic acids decreased. In addition to the presence of pollutants, the development of maize was studied by analysing its rhizodeposition at the 4, 6 and 8-leaf stages. The effect of Cd on exudation seemed to increase from the 6-leaf stage, while that of phenanthrene tended to decrease. On the other hand, the influence of pollutants on mucilage seemed less marked and more constant over time. Finally, many rhizodeposited molecules have been identified as playing a role in the pollutants’ dynamics in the soil and therefore in their tolerance by the plant, in particular through complexation or solubilisation mechanisms
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Castro-Castellon, Ana. "A biofilter process for phytoplankton removal prior to potable water treatment works : a field and laboratory study." Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:9ac04284-cf4a-48f1-bdab-d8ca6e66aefb.
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Phytoplankton blooms compromise the quality of freshwater ecosystems and the efficient processing of water by treatment works worldwide. This research aims to determine whether in-situ filamentous biofiltration processes mediated by living roots and synthetic filters as media can reduce or remove the phytoplankton loading (micro-algae and cyanobacteria) prior to a potable water treatment works intake. The underlying biofiltration mechanisms were investigated using field and laboratory studies. A novel macroscale biofilter with three plant species, named the "Living-Filter", installed in Farmoor II reservoir, UK, was surveyed weekly for physicochemical and biological variables under continuous flow conditions during 17 weeks. The efficiency of a mesoscale biofilter using the aquatic plant Phalaris arundinacea and synthetic filters, was tested with Microcystis aeruginosa under continuous flow conditions and in batch experiments. The 'simultaneous allelochemical method' was developed for quantifying allelochemicals from Phalaris in aqueous samples. Microscale studies were used to investigate biofilter allelochemical release in response to environmental stressors and Microcystis growth inhibition in filtered and unfiltered aqueous root exudate. Results demonstrate that the removal of phytoplankton biomass by physical mechanisms has a removal efficiency of ≤45% in the "Living-Filter" (filamentous biofilter plus synthetic fabric) and that the removal of Microcystis biomass using only biofilters was 25%. Chemical mechanisms that reduce Microcystis cell numbers are mediated by allelochemicals released from biofilter roots. Root exudate treatments on Microcystis revealed that Microcystis growth is inhibited by allelochemicals, not by nutrient competition, and that protists and invertebrates play a role in removing Microcystis. Filamentous biofilters can remove phytoplankton biomass by physical, chemical and biological mechanisms. Biofilters and synthetic filters in combination improve removal efficiency. Application of macroscale biofilters prior to potable water treatment works benefits the ecosystem. Plant properties, biofilter size to surface water ratio, and retention time must be considered to maximise the benefits of biofiltration processes.
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Leyval, Corinne. "Intéractions bactéries-mycorhizes dans la rhizosphère du pin sylvestre et du hêtre : Incidences sur l'exsudation racinaire et l'altération des minéraux." Nancy 1, 1988. http://www.theses.fr/1988NAN10169.
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L'influence de bactéries solubilisant les phosphates (agrobactérium) et de champignons éctomycorhizogènes sur l'altération d'un mica, la phlogopite et de phosphates insolubles, a été étudiée : en cultures liquides, en l'absence de racine ; dans la rhizosphère du pin sylvestre et du hêtre, en relation avec les composés exsudés. Les thizobactéries favorisent la solubilisation des éléments minéraux par production d'acides organiques. Les champignons ectomycorhizogènes solubilisent les phosphates en culture pure, mais, en conditions symbiotiques, ils jouent surtout un rôle par l'augmentation du volume de sol exploré par les racines, donc des surfaces d'échnage et d'adhésion avec les minéraux
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Akter, Pervin. "Plant Root Exudates." Doctoral thesis, 2016. http://hdl.handle.net/11858/00-1735-0000-002B-7D35-3.
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Samal, Debasmita. "Potassium uptake efficiency mechanisms and root exudates of different crop species." Doctoral thesis, 2007. http://hdl.handle.net/11858/00-1735-0000-0006-AFF3-D.
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Samal, Debasmita [Verfasser]. "Potassium uptake efficiency mechanisms and root exudates of different crop species / submitted by Debasmita Samal." 2007. http://d-nb.info/986869759/34.
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Lee, Cheng-Hsuan, and 李承玹. "Low Molecular Weight Dicarboxylic Organic Acids by Brassicaceae: Root Exudates and Effects in Contaminated Soils." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/54933287372550946303.
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碩士國立臺灣大學
農業化學研究所
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Abstract Many research shows that some Brassica spp. have been proved can hyperaccmulate cadmium and zinc in shoot in recent years, but until now doesn''t have a final conclusion. These researchers suggest that just only target at soil-root interface (rhizosphere) to study, can understand more detail about the relationship between organic acids in rhizosphere and accmulate cadmium and zinc in shoot.The validity of Cadmium (Cd) and zinc (Zn) in soils will increase by the low-molecular-weight dicarboxylic organic acids (LMWDOAs) [oxalic acid, malonic acid, fumaric acid, succinic acid, maleic acid] produced at the soil-root interface (rhizosphere), especially cadmium, it also play an important role in availability and uptake of Cd and Zn, vary between cultivars of Brassicaceae. The objective of this study, therefore, was to (1) investigate the nature and quantity of LMWDOAs present in the rhizosphere of Brassicaceae cultivars [ Brassica oleracea, Brassica juncea (L.) Coss, Brassica oleracea Var. Capitata, Brassica campestris, Brassica chinensis ] grown in four different soils: TY-C, TY-NC, CH-C, and CH-NC, and (2) study the relationship between the validity of Cd , Zn in soil and LMWDOAs present in the rhizosphere. Plants were grown in pot-cultures conditions. Malonic, fumaric, succinic, and maleic acids were found and quantified in the HCl/MeOH extracts of rhizosphere soil, with malonic and succinic acids being predominant. No HCl/MeOH extractable LMWDOAs were identified in the bulk soil. Total amount of LMWDOAs in the rhizosphere soil of the contaminated soil was significantly higher than that for the low or non-contaminated soil in all four soils, ( just effect by cadmium concentration in soils, but not significantly effect by zinc concentration in soils ) furthermore, large differences in amounts of LMWDOAs were found in the rhizosphere soil for the same cultivars grown in different soils and followed the pattern: TY-C >CH-C >CH-NC~ TY-NC. Extractable Cd concentration also followed the same soil sequence as LMWDOA production. These results suggest that the Cadmium accumulation Cd accumulating cultivars will be proportional to the levels of LMWOAs found in the rhizosphere soil of each cultivar, the differing levels of LMWDOAs present in the rhizosphere soil played an important role in the solubilization of particulate-bound Cd into soil solution and its subsequent phytoaccumulation by the high and low Cd accumulating cultivars, by the way these five LMWDOAs will not the main imfulance help plant accumulation zinc.
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Modise, Lorato. "Isolation and Characterization of Rhizosphere Bacterial Community from cultivated plants in Mahikeng, NorthWest Province, South Africa / Lorato Modise." Thesis, 2014. http://hdl.handle.net/10394/16198.
Full textAbstract:
The rhizosphere is characterized by the presence of high microbial activities which are
influenced by plant root exudates. This study examined bacterial diversity and physiological
functions plants rhizosphere using both culture-dependent and culture-independent techniques of
seven cultivated. Physico-chemical properties of soil samples revealed that the rhizobacteria
adapted well to pH ranging from 7.5 to 9.1. Macronutrients (carbon, nitrogen, calcium,
magnesium, phosphorous, potassium, sodium and iron) had a wide range of concentration
between 0 to 4380.1 mg/kg. Concentrations of metal elements (cadmium, cobalt, chromium,
copper and zinc) from all rhizosphere samples were below the amount of 3.1 mg/kg, indicating
that the samples were free from metal contaminations. Sole carbon substrates utilization of
bacteria in rhizosphere samples were measured as Average Well Colour Development (A WCD)
and Group-wise Average Well Colour Development (AWCDg) patterns. At seventy two hours,
there was no significant difference in AWCD patterns between bacteria in all samples and there
was a significant difference in AWCDg patterns. Biochemical tests showed majority of isolates
had similar physiological properties to members of Bacillus genus. All the bacterial isolates
exhibited positive antifungal trait, fifteen solubilized phosphate and three had cyanide production
traits during in vitro plant growth promotion assays. In vitro plant growth revealed that bacterial
isolate RL1 (Bacillus licheniformis) produced the highest concentration of indole acetic acid
(IAA) at 25 mg/ml. Bacterial isolate RG3 (Bacillus pumilus) had the highest amino cyclopropane
carboxylase (ACC) deaminase activity indicated by the high production of α-ketobutyrate
produced at 4.8 mg/ml. There were significant differences in shoot length at P ≤ 5% level of
significance and there was no significant difference in the number of leaves across all three
inoculated plants at P ≥ 5% level of significance. Sequence and phylogenetic analysis of
identified culture-dependent bacteria revealed a homologous similarity of 94 to 100% between
isolates sequences and GenBank sequences. From this, 81% of the sequences were closely
related to Firmicutes, 13% to Actinobacteria and 6% to Proteobacteria. From cultureindependent
method, only 8 PCR-DGGE bands were detected, the 200 bp sequences in the 16S
rRNA fragment showed 91 to 100% homologous similarity to GenBank sequences. Their 16S
rRNA sequences was closely related to 50% uncultured bacterium clones, 25% Firmicutes, 13%
Proteobacteria and 12% Bacteroidetes sequences. Both culture-dependent and cultureindependent
techniques were precise in the identification and description of bacterial community
in rhizosphere.Thesis (M.Sc) North-West University, Mafikeng Campus, 2014
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Lu, Chia-Yen, and 呂佳燕. "The ptsG gene participating in root exudates-mediated systemic disease resistance-inducing ability of Bacillus cereus C1L in maize." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/75274124606526255365.
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Yang, Luojin. "Root exudation pattern of sugar beet (Beta vulgaris L.) as influenced by light intensity and P deficiency." Thesis, 2016. http://hdl.handle.net/11858/00-1735-0000-0028-87DC-8.
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