Les sols des oliveraies subissent des pressions environnementales fortes telles que les contraintes pédoclimatiques méditerranéennes et des pratiques agronomiques intensives. Ils requièrent une grande attention face aux changements climatiques. En zone littorale, les stress osmotiques et thermiques s’intensifient. Dans un contexte d’exacerbations de pressions, les sols pourraient subir des modifications profondes de leur qualité, modifications qu’il serait possible d’atténuer en adoptant des pratiques agricoles "durables". Ce projet de thèse a pour objectif d’examiner, en tenant compte de la littoralité, l’impact de pratiques conventionnelles et de conservation sur les activités microbiennes des cycles du C et N et les caractéristiques chimiques du sol. Ont été évaluées dépendamment de la distance à la mer, I)les fonctions des communautés microbiennes de la phyllosphère et de la rhizosphère de l’olivier, II)l’incidence du labour, de co-culture de Fabaceae, d’un enherbement et d’un apport de margions au Liban et en France, III)les réponses microbiennes à des stress hydriques après différentes pratiques. Ce travail a porté plus précisément sur les activités enzymatiques et cataboliques microbiennes intervenant dans la transformation de la matière organique dont la qualité a été étudiée par RMN du solide13C. Ce travail a permis d’observer une littoralité des fonctionnements microbiens avec une atténuation probable des émissions de CO2 par l’utilisation des pratiques de conservation. Par conséquent il est nécessaire de développer en oléiculture intensive des pratiques garantissant la stabilité des fonctions écologiques supportées par les relations sols/microorganismes/plantes. / Olive grove soils are subjected to harsh environmental pressures such as Mediterranean constraints and intensive agriculture practices. They require a great attention in the context of climate change. In coastal areas, osmotic and thermal stresses are intensified. Under these conditions of intensified pressure, significant changes in soil quality may occur and these changes can be mitigated by ‘sustainable’ farming practices. Thus, this thesis project aimed at evaluating, under coastal constraints, the impact of conventional and conservation practices on microbial activities involved in C and N cycles, and soil chemical characteristics. Depending on the distance from the sea, we evaluated i) functions of microbial communities of olive rhizosphere and phyllosphere, ii) the effect of tillage, Fabaceae co-culture, natural grass, OMW in Lebanon and France, iii) microbial responses to water stress under different practices. This work focused on microbial activities involved in the transformation of organic matter, whose quality was studied by solid state NMR 13C. Therefore, this work reported a ‘coastal print’ on microbial functioning and a likely reduction of CO2 emissions through the application of conservation practices. Therefore, it is necessary to develop, under olive tree culture intensification, practices ensuring stability of ecological functions supported by soils / microorganisms / plants relationships.

Diazotróficos de vida-livre podem ser encontradas associadas à filosfera, dermosfera e rizosfera das espécies vegetais. Alguns dados sugerem que a fixação biológica de N2 (FBN) por bactérias assimbióticas representa uma entrada importante de nitrogênio nos ecossistemas tropicais, variando com as espécies vegetais e nas diferentes partes da planta. O presente trabalho teve como objetivos estimar a quantidade de N2 fixado de forma assimbiótica na filosfera, dermosfera e rizosfera sobre a copa das espécies vegetais Guapira oposita e Euterpe edulis, e avaliar a diversidade das bactérias assimbióticas, através da análise do gene rRNA 16S, em uma Restinga ,em Ubatuba, SP. O estudo foi realizado no Parque Estadual da Serra do Mar, Núcleo Picinguaba, em épocas de baixa e alta pluviosidade. A atividade da nitrogenase foi determinada pela técnica de redução do acetileno e as concentrações de etileno foram determinadas por cromatografia gasosa. A diversidade de bactérias que habitam filosfera, dermosfera e solo foi acessada por pirosequenciamento da região V4 do gene rRNA 16S. A maior fixação de N foi observada na dermosfera de E. edulis nas duas épocas de coleta (175,1± 53,4 ng cm-2 h-1; 97,2 ± 21 ng cm-2 h-1), as taxas de fixação de N mais baixas foram observadas no solo. Na época de alta pluviosidade, a FBN na filosfera de G. oposita (52,0 ± 12 ng cm-2 h-1) foi significativamente maior do que a filosfera de E. edulis (3,6 ± 06 ng cm-2. h-1) e do que no mesmo compartimento mas em diferentes épocas de coleta (7,5 ± 1,3 ng cm-2 h-1). O valor do 15N foi maior no solo onde a fixação de N foi mais baixa. Na filosfera e na dermosfera, a relação C/N foi mais baixa quando a FBN foi mais alta. A FBN no solo e serrapilheira de restinga apresentou grande variação espacial, com locais de alta atividade. As 188629 sequências obtidas foram agrupadas em 16727 Unidades Taxonômicas Operacionais (UTOs), distribuídos em 35 filos. Os principais filos detectados foram Proteobacteria (38%) e Acidobacteria (12%). As classes Alphaproteobacteria e Gammaproteobacteria foram as mais abundantes nos três compartimentos. Potenciais fixadores de N foram detectados nas classes Alpha Beta e Gammaproteobacteria. A abundância de cianobacterias fixadoras de N na filosfera e na dermosfera foi baixa, indicando que outros diazotróficos também colonizam esses ambientes e contribuem com a FBN. / Free-living N2 fixing bacteria can be found associated with the phyllosphere, bark and rizosphere of the diferent plant species. Some data suggest that biological N2 fixation (BNF) by free-living bacteria represents an important input of nitrogen in tropical ecosystem, varying with the plant species and in different parts of the plant. This study aimed to estimate the amount of N2 fixed in the phyllosphere, bark and soil under the canopy of Guapira opposite and Euterpe edullis, and evaluate the diversity of bacteria through the sequencing of the 16S rRNA gene analysis, the phyllosphere, bark and soil in a Restinga area, Ubatuba, SP. The study was conducted in the Parque Estadual da Serra do Mar, Núcleo Picinguaba in seasons of low and high rainfall. Nitrogenase activity was determined by the acetylene reduction assay (ARA) and ethylene concentrations were determined by gas chromatography. The diversity of bacteria in the phyllosphere, bark and soil was accesed using pyrosequencing of the 16S rRNA V4 region. The bark of Euterpe edullis was higher at both sampling times (175,1±53,4 ng. cm-2. h-1, 97,2±21 ng. cm-2. h-1). The BNF rates were lower in soil. In high rainfall conditions, the BNF in the phyllosphere of Guapira opposite increased significantly (52,0±12 ng. cm-2. h-1) when compared with Euterpe edullis (3,6 ± 06 ng. cm-2. h-1) and Guapira opposite (7,5 ± 1,3 ng. cm-2. h-1) phyllosphere. The value of 15N was higher in the soil where the rates of FBN was lower. In the phyllosphere and bark, C/N was lower when BNF was higher. BNF in soil great spatial variation with areas of high activity. The 18.629 sequences obtained were grouped into 16.727 Operational Taxonomic Units (OTUs) distributed in 35 phyla. The main phyla Proteobacteria represented 38% of the OTUs and Acidobacteria 12% of the UTOs. The classes Alphaproteobacteria and Gammaproteobacteria were the most abundant in the three compartmens. Alphaproteobacteria, Betaproteobacteria and Gammaproteobacteria were the main potential N-fixers. The abundance of nitrogen-fixing Cyanobacteria in the phyllosphere and bark was low, indicating that others diazotrophics also colonize these environments and contribute with BNF.

Wo und wie schnell nehmen Wurzeln Wasser auf? Obwohl diese Frage in Pflanzen- und  Bodenwissenschaften von großer Bedeutung ist, gibt es nur wenige experimentelle Daten darüber, an welcher Stelle der Wurzeln eine transpirierende Pflanze das Wasser aus dem Boden erhält. Die Antwort auf diese Frage erfordert direkte und in-situ Messungen des lokalen Wasserflusses in die Wurzel hinein. Ziel dieser Arbeit war es, eine neue Methode zu entwickeln und anzuwenden, um den lokalen Wasserfluss in unterschiedliche Segmente der Pflanzenwurzeln zu quantifizieren. Dabei wurde Neutronenradiographie eingesetzt um den Transport von deuteriertem Wasser (D2O) in die Wurzel von Lupinen zu untersuchen. Die Lupinen wuchsen in Aluminium Containern, die mit sandigem Boden gefüllt waren. Der sandige Boden wurde mit Hilfe von 1cm-dicken Schichten groben Sandes in verschiedene Bereiche eingeteilt. Diese Schichten reduzierten die Diffusion von D2O zwischen den verschiedenen Bereichen.  D2O wurde in ausgewählte Bereiche tagsüber (transpiriende Pflanzen) und nachts (nicht transpiriernde Pflanze) injiziert. Transport von D2O in die Wurzeln hinein wurde durch Neutronenradiographie mit einer räumlichen Auflösung von 100 µm in Intervallen von 10 Sekunden aufgezeichnet. Die Messungen zeigten: i) Transport von D2O in die Wurzel hinein war tagsüber schneller als nachst; ii) D2O wurde tagsüber schnell entlang der Wurzel in Richtung Spross transportiert, während dieser axiale Fluss nachts vernachlässigbar war. Die Unterschiede zwischen Tag- und Nachtmessungen wurden durch konvektiven Transport von D2O in den Wurzeln erklärt. Um den effektiven Wasserfluss in die Wurzeln hinein zu quantifizieren, wurde ein einfaches Konvektions-Diffusions Modell entwickelt, wobei die Zunahme der D2O Konzentration in Wurzeln vom konvektiven Transport abhängt und von the Diffusion des D2O in die Wurzeln. Die Ergebnisse zeigten, dass die Wasseraufnahme nicht gleichmäßig entlang der Wurzel stattfindet. Die Wasseraufnahme war in den oberen Bodenschichten höher als in den tieferen. Entlang einzelner Wurzeln war der radiale Fluss in nahen Teilen der Wurzel höher als in den weiter entfernten Teilen der Wurzel. In Lupinen fand die Wasseraufnahme im Wesentlichen in den lateralen Wurzeln statt. Die Funktion der Pfahlwurzel war es, das Wasser der lateralen Wurzeln zu sammeln und zum Spross zu transportieren. Diese Funktion wird durch eine geringe radiale und eine hohe axiale Leitfähigkeit sichergestellt.  Wir haben diese Technik auch angewandt um den Einfluss der Rhizosphäre auf die Wasseraufnahme zu untersuchen. Wie vor Kurzem auch in der Literatur berichtet wurde, wurde auch in dieser Arbeit beobachtet, dass der Boden in der unmittelbaren Nähe der Wurzeln, der sogenannten Rhizosphäre, hydrophob wird, wenn der Boden trocken wird. Zum ersten Mal konnte gezeigt werden, dass durch die Hydrophobizität der Rhizosphäre die Wasseraufnahme nach Trocknung und folgender Bewässerung reduziert wird. Es wurde die Schlussfolgerung gezogen, dass nach Trocknung die Rhizosphäre einen entscheidenden Wiederstand für den Wasserfluss zur Wurzel darstellt. Das beeinflusst vermutlich auch die Ausdehnung des Bereiches der Wurzeln, in dem Wasser aufgenommen wird. Die Bedeutung dieser Arbeit ist die Entwicklung einer neuen Methode, um Wasseraufnahme durch Wurzeln lebender Pflanzen lokal zu quantifizieren. Diese Methode macht es möglich quantitativ zu messen, wo und wie schnell Wurzeln Wasser im Boden aufnehmen. Diese Technik wird es erleichtern, die Funktionsweise der Wurzeln verschiedener Pflanzen zu verstehen und den Einfluss von Wurzelwachstum und wechselnder äußerer Bedingungen, wie Wassergehalt, Transpiration und Verfügbarkeit von Nährstoffen und vieler weiterer Faktoren zu untersuchen.  Die Antwort auf diese Fragen könnten einen weiten Bereich für landwirtschaftliche Anwendungen eröffnen, die darauf abzielen, Bewässerungsmethoden zu verbessern.

La présente étude porte sur l’évaluation d’une méthode d’acquisition de la solution de sol présente à l’interface sol-racine, dans la rhizosphère. Cette interface constitue le lieu privilégié de prise en charge par les plantes des contaminants, tels que les métaux traces. Comme les plantes acquièrent ces éléments à partir de la phase liquide, la solution de sol de la rhizosphère est une composante clé pour déterminer la fraction de métaux traces biodisponibles. La microlysimétrie est la méthode in situ la plus appropriée pour aborder les difficultés liées à l’échelle microscopique de la rhizosphère. Ainsi, dans les études sur la biodisponibilité des métaux traces au niveau de la rhizosphère, les microlysimètres (Rhizon©) gagnent en popularité sans, toutefois, avoir fait l’objet d’études exhaustives. L’objectif de cette étude est donc d’évaluer la capacité de ces microlysimètres à préserver l’intégrité chimique de la solution, tout en optimisant leur utilisation. Pour ce faire, les microlysimètres ont été soumis à une série d’expériences en présence de solutions et de sols, où la quantité de solution prélevée et le comportement des métaux traces (Cd, Cu, Ni, Pb, Zn) ont été étudiés. Les résultats montrent que les microlysimètres fonctionnent de façon optimale lorsque le contenu en eau du sol est au-dessus de la capacité au champ et lorsqu’il y a peu de matière organique et d’argile. Les sols sableux ayant un faible contenu en C organique reproduisent mieux le volume prélevé et la solution sous la capacité au champ peut être récoltée. L’utilisation des microlysimètres dans ces sols est donc optimale. Dans les essais en solution, les microlysimètres ont atteint un équilibre avec la solution après 10 h de prélèvement. En respectant ce délai et les conditions optimales préalablement établies (pH acide et COD élevé), les microlysimètres préservent la composition chimique de la solution. Dans les essais en sol, cet équilibre n’a pas été atteint après dix jours et huit prélèvements. Le contenu en matière organique et l’activité microbienne semblent responsables de la modification des concentrations en métaux au cours de ces prélèvements, notamment, dans l’horizon FH où les microlysimètres performent très mal. En revanche, dans l’horizon B, les concentrations tendent à se stabiliser vers la fin de la série de prélèvements en se rapprochant des valeurs de référence. Bien que des valeurs plus élevées s’observent pour les microlysimètres, leurs concentrations en métaux sont comparables à celles des méthodes de référence (extrait à l’eau, lysimètres de terrain avec et sans tension). En somme, les microlysimètres se comportent généralement mieux dans l’horizon B. Même si leur utilisation est plus optimale dans un sol sableux, cet horizon est privilégié pour de futures études sur le terrain avec les microlysimètres. / This study focuses on evaluating a method of acquiring soil solution in the soil-root interface of the rhizosphere. The liquid phase of the rhizosphere constitutes the main area where plants absorb contaminants like trace metals. Thus the rhizosphere soil solution is key to determine the amount of bioavailable trace metals. Microlysimetry has been described as the most appropriate in situ method to tackle difficulties inherent to the microscopic scale of the rhizosphere. Despite the lack of an exhaustive evaluation of their performance, microlysimeters have gained popularity for in situ studies on the bioavailability of trace metals. The objective of this study was to evaluate the capacity of microlysimeter to preserve the chemical integrity of the soil solution and also to determine their optimum use conditions. To do this, microlysimeter have been submitted to a series of laboratory experiments with solutions and soils. The volume of solution extracted and trace metals (Cd, Cu, Ni, Pb, Zn) behaviour were studied. Results show that microlysimeters work optimally when soil water content is above field capacity and when the amount of clay and organic matter is low. Sandy soils with low organic carbon content have a better reproducibility for extracted volume and soil solution extraction is possible even when soil water content is below field capacity. Using microlysimeters in this soil type is thus optimal. In solution experiments, microlysimeters reached equilibrium with the control solution after ten hours of extraction. In optimal conditions (acidic pH and high DOC) and after this ten hours period, microlysimeters preserve the chemical composition of the solution. In soil experiments, this equilibrium has not been reached after eight samplings throughout ten days. Organic matter content and microbial activity could be responsible for the modification of concentrations of trace metals during sampling. This is especially true for FH horizon where microlysimeters perform poorly. In contrast, the concentrations reach the reference values toward the end of sampling serie in the B horizon and microlysimeters have a better overall performance in this horizon. Although higher values are observed for microlysimeters, trace metals concentrations are comparable to other extraction methods, specifically for the B horizon. Even if their uses are optimized in sandy soil, the B horizon should be privileged for future field studies involving microlysimeters.

Endophytes are organisms that live inside plants without causing disease and include microbes that benefit their hosts by aiding in nutrient acquisition and pathogen control. This thesis concerns the endophytes of the genus Zea which includes modern maize (Zea mays L.). Beginning 9,000 years ago, maize was domesticated from wild grasses in Mexico (teosintes), bred into diverse varieties and moved to new soils throughout the Americas. The impact of these long-term changes on the associated endophytic communities has not been examined. Furthermore, today, maize is routinely transplanted around the world to facilitate breeding, but the short-term impact of switching soils on endophyte composition is not known. I attempted to answer the first question by surveying the bacterial endophytes that inhabit 14 diverse ancestral, ancient and modern Zea genotypes. To answer the second question, three extreme Zea genotypes, ancestral, intermediate and modern, were grown side by side on two extreme soils that span the tropical-to-temperate migration route of maize. Endophyte populations from seeds, roots and shoots were DNA fingerprinted using terminal restriction length polymorphism (TRFLP) of 16S rDNA. To understand microbial functions, bacteria were cultured and tested for >13 in vitro traits including nitrogen fixation, phosphate solubilization, plant hormone production and antibiosis. Relationships between endophyte communities were analyzed using principle component analysis (PCA) and Sᴓrensen’s similarity index. The results show that different Zea tissues and genotypes have diverse endophytic communities. The community composition of seed endophytes correlates with host phylogeny suggesting that as humans bred maize, they inadvertently impacted its microbial inhabitants, though the change was gradual. Soil swapping and growth on sterile sand confirm that shoot and root endophyte communities in juvenile plants are primarily inherited. However, a given maize genotype can also select and take up the same microbes (based on TRFLP) from geographically diverse soils. These latter results show that the endophyte communities of Zea plants are significantly buffered from the short-term effects of migration. A few microbes and microbial traits are conserved across all Zea genotypes and soil treatments, suggestive of a core taxonomic and functional microbiota for this agriculturally important genus. / OMAFRA New Directions, Ontario Research Fund, Canadian Foundation for Innovation

[Truncated abstract] Native Australian soils contain very low amounts of phosphorus. The soils of southwestern Australia are ancient and highly weathered. Consequently, the availability of phosphorus in these soils is too low for cropping purposes, so the application of P is necessary to maintain productivity. When P is applied to soil, typically as soluble superphosphate, it tends to be transformed to increasingly less soluble forms over time. Sparingly soluble forms of soil P are relatively inaccessible to Triticum aestivum; however, many grain legumes have a higher P-acquisition efficiency, allowing them to access pools of soil P that T. aestivum cannot. The P-acquisition efficiency of some grain legumes has been attributed in part to their ability to release large quantities of carboxylates, coupled with the development of cluster roots for species such as Lupinus albus. There are a number of unexplained observations in terms of the P-acquisition efficiency of grain legume species and the way that those species respond to P fertilisation. This PhD project aimed to study carboxylate release from a range of crop species, and investigate its role in variation among species for acquisition of phosphorus from sparingly soluble forms (chapter 1). ... L. albus (chapter 5). There was considerable variation in P acquisition among accessions. The variation cannot be attributed to differences in carboxylate release, cluster-root development or whole root system rhizosphere extract pH as measured in this study. We hypothesise that the variation might be attributed to differences in the ratio of release of protons and other cations localised around cluster roots. In conclusion studies of carboxylate exudation and sparingly soluble forms should use more than a single form if the aim is to draw generalised conclusions on P-uptake efficiency from sparingly soluble forms. Comparative studies of a range of species are a useful tool for enhancing our understanding of root physiology. While the benefit of carboxylates for providing access to poorly soluble P has been demonstrated, questions remain as to potential other roles for carboxylates, particularly in species that do not form cluster roots. Variation in P uptake among accessions of L. albus is present, and more work on proton release and ion balance of root clusters is necessary to understand intraspecific variation.

Made available in DSpace on 2014-06-11T19:32:54Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-12-19Bitstream added on 2014-06-13T18:44:30Z : No. of bitstreams: 1 cardoso_er_dr_jabo.pdf: 228976 bytes, checksum: ca70e1512974c2bad475cf6b0242c931 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / O uso de agentes biológicos para controle de nematóides é considerado uma das várias medidas a serem empregadas em um manejo integrado de pragas, sendo uma preocupação de caráter mundial. Contudo, foram estudados os fatores determinantes da freqüência de fungos totais e nematófagos, da atividade enzimática e da distribuição de nematóides de solos não rizosféricos e rizosféricos sob alface (Lactuca sativa L.); banana (Musa cavendishii L.); grama batatais (Paspalum notatum) e Impatiens (Impatiens valleriana). A atividade predadora dos fungos nematófagos foi avaliada contra o nematóide Panagrellus redivivus. O número de fungos totais variou de 6,9 x 105 a 31,2 x 105 UFC g-1 solo seco no solo não-rizosférico e de 6,9 x 105 a 25,6 x 105 UFC g-1 solo seco no solo rizosférico. As contagens dos fungos nematófagos corresponderam a 23-41 % e 23-34 % dos fungos totais encontrados no solo rizosférico e não-rizosférico, respectivamente. Enquanto as contagens dos fungos totais do solo rizosférico se distribuíram na seguinte seqüência: alface > banana > grama-batatais > Impatiens, os nematófagos diminuíram na seguinte ordem: alface > Impatiens > banana > grama-batatais. A matéria orgânica e a umidade do solo influenciaram a distribuição tanto dos fungos totais como dos nematófagos do solo não-rizosférico. A distribuição dos nematóides nas amostras de solo e raiz foram Rotylenchulus sp., Helicotylenchus sp. e Tylenchus sp. para alface, Meloidogyne sp., Helicotylenchus sp., Pratylenchus sp. e Rotylenchulus sp. para banana, Meloidogyne sp., Helicotylenchus sp., Pratylenchus sp. e Rotylenchulus sp. para grama-batatais, Meloidogyne sp., Helicotylenchus sp., Pratylenchus sp., Rotylenchulus sp. e Tylenchus sp. para Impatiens. Em termos gerais, as atividades da desidrogenases, amilases, celulases e endoglucanases distribuíram-se no solo não-rizosférico de acordo... / Biological control of nematodes is considered one of the many practices that can be used in integrated pest management. We investigated the factors affecting the frequency of the total and the nematophagous fungi, soil enzymatic activity as well as the distribution of the nematodes in rhizospheric and bulk soil of lettuce (Lactuca sativa L.); Impatiens (Impatiens valleriana); banana (Musa cavendishii L.) and Bahiagrass (Paspalum otatum). The effect of the nematophagous fungi were evaluated against the nematode Panagrellus redivivus. The total fungal number ranged from 6,9 x 105 to 31,2 x 105 UFC g-1 dry soil in the bulk soil and from 6,9 x 105 to 25,6 x 105 UFC g-1 dry soil in the rhizosphere. Nematofagous fungi counts were to 23-41 % and 23-34 % of the total fungi found in the rhizosphere and bulk soil, respectively. While the total fungi counts of the rizosphere were distributed in the following sequence: lettuce > banana > Bahiagrass > Impatiens, the nematophagous fungi decreased in the following order: lettuce> Impatiens >banana > Bahiagrass. Moisture and organic matter contents of the bulk soil influenced the distribution of the total and nematophagous fungi of the soil. The following phytonematodes found in the samples of soil and roots were Rotylenchulus sp., Helicotylenchus sp. and Tylenchus sp (lettuce), Meloidogyne sp., Helicotylenchus sp., Pratylenchus sp. and Rotylenchulus sp (banana), Meloidogyne sp., Helicotylenchus sp., Pratylenchus sp. and Rotylenchulus sp. (Bahiagrass), Meloidogyne sp., Helicotylenchus sp., Pratylenchus sp., Rotylenchulus sp. and Tylenchus sp. (Impatiens). In general, the activities of the enzymes desidrogenase, amylase, celulase and endoglucanase followed the distribution of the frequency of the soil total and nematophagous fungi ...(Complete abstract, click electronic access below)

Orientador: Ciro Antonio Rosolem / Banca: Leonardo Theodoro Büll / Banca: Francisco Antonio Monteiro / Resumo: É crescente o uso de espécies do gênero Brachiaria nos mais diversos sistemas de produção, e isso se deve em grande parte à adaptabilidade dessas espécies às mais variadas condições de solo e/ou clima. A Brachiaria humidicola, particularmente, pode sintetizar e liberar de suas raízes compostos que inibem o processo de nitrificação, o que pode provocar alterações na ciclagem do nitrogênio (N) no sistema solo-planta. No presente estudo avaliou-se a dinâmica do N no sistema solo-planta, bem como as perdas de N-NH3 após a dessecação de Brachiaria brizantha, Brachiaria decumbens, Brachiaria humidicola e Brachiaria ruziziensis, espécies amplamente cultivadas no Brasil. O experimento foi conduzido em casa de vegetação, em Botucatu-SP, utilizou-se um Latossolo Vermelho distroférrico e o delineamento experimental adotado foi o de blocos casualizados, com parcelas subdivididas no tempo e quatro repetições. As parcelas foram compostas por quatro espécies de brachiaria (B. brizantha, B. decumbens, B. humidicola e B. ruziziensis) e as subparcelas por cinco épocas de avaliação (0, 7, 14, 21 e 28 dias após a dessecação). As plantas foram dessecadas com glyphosate 50 dias após a semeadura. Em cada uma das avaliações foram determinadas a massa de matéria seca das raízes e da parte aérea (colmos + folhas), bem como os teores de N-total, N-NH4+ e N-NO3- das brachiarias. Do solo, que foi dividido em solo da rizosfera e solo não-rizosférico, foram determinados os teores de N-total, N-NH4+, N-NO3-, pH e matéria orgânica. Também foi estimado o balanço do N no sistema solo-planta após a dessecação. As quatro espécies do gênero Brachiaria não apresentaram efeito significativo no processo de nitrificação. As maiores perdas de N do sistema solo-planta após a dessecação foram verificadas na B. ruziziensis, as quais foram pequenas e não resultaram em perdas... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Increasingly Brachiaria species are grown in different crop systems, and this is largely due to the adaptability of these plants in the several soil and climate conditions. Brachiaria humidicola, particularly, is able to synthesize and release compounds from their roots that inhibit the nitrification, which can cause changes in the nitrogen (N) cycling in the soil-plant system. In this study we evaluated the N dynamics in soil-plant system and NH3-N losses after desiccation of Brachiaria brizantha, Brachiaria decumbens, Brachiaria humidicola and Brachiaria ruziziensis, species widely cultivated in Brazil. The experiment was conduced in a greenhouse located in Botucatu, SP, Brazil. The study was carried out in a split plot in randomized blocks design, with four replicates. Plants of B. brizantha, B. decumbens, B. humidicola e B. ruziziensis were grown in pots filled with a clay soil and were desiccated with glyphosate 50 days after planting. Plant and soil samples were taken 0, 7, 14, 21 and 28 days after plant desiccation. Each sampling time root and shoot dry matter and total-N, ammonium-N (NH4+-N) and nitrate-N (NO3--N) were determined in plant tissue. Rhizospheric and non rhizospheric soil were separated and total-N, NH4+-N, NO3--N, pH and organic matter were determined in soil samples. Nitrogen budget in soil-plant system after desiccation was estimated. The four Brachiaria species has no significant effect on the nitrification process. The largest N losses from soil-plant system after desiccation were found in B. ruziziensis, but these losses were small and didn't result in significant N losses from soil-plant system / Mestre

L'activité humaine est responsable de pollutions diffuses des sols entrainant des dommages sur l'écosystème. Afin d'éviter des déséquilibres importants comme la diminution de la biodiversité ou bien la contamination des chaînes trophiques par des polluants, il est nécessaire de restaurer les écosystèmes. Les différentes techniques utilisées à l'heure actuelle sont couteuses, diminuent la fertilité du sol et ont un effet négatif sur la fonctionnalité des écosystèmes. A contrario, la phytoremédiation ou dépollution grâce aux plantes, apparaît comme une solution digne d'intérêt. Néanmoins, elle nécessite d'être améliorée puisque de nombreux mécanismes restent inexpliqués. L'originalité de notre travail est d'étudier la fonctionnalité de la rhizosphère du maïs (Zea mays) exposée à des pesticides organochlorés (OCPs), le lindane et la chlordécone, interdits respectivement en 1998 et 1993 et persistants dans l'environnement. Cette étude a été réalisée en présence ou absence de microorganismes afin de préciser les mécanismes mis en jeux par les microorganismes et les matrices végétales. Ce travail a mis en évidence les mécanismes impliqués dans la phytotoxicité des deux organochlorés sur les cellules racinaires. Les réponses cellulaires sont dose-dépendantes et montrent un effet des OCPs sur le cycle cellulaire (induction de l'endoréplication et de la ploïdie) et la mort cellulaire (induction de ROS, du calcium cytosolique, des caspase-3-like, de l'apoptose) lors d'expositions extrêmes (correspondant à des cas particuliers comme les friches industrielles). A de plus faibles expositions ayant une réalité environnementale, les racines exposées montrent une perturbation importante de leur métabolome primaire. Ces modifications mesurées sur la production des sucres, des acides organiques, des acides aminées et des lipides peuvent être induites par le stress oxydant produit par les OCPs. Par ailleurs, de tels changements dans le métabolome peuvent provoquer une modification de la composition des exsudats racinaires, jouant sur la relation plante/microorganismes de la rhizosphère. Nos résultats montrent que la fonctionnalité globale de la rhizosphère (allocation des ressources en carbone et azote, catabolisme des microorganismes) n'est pas modifiée sur le long terme en présence des OCPs. Enfin, nous avons démontré l'implication de la rhizosphère (rétention/métabolisation des OCPs) sur l'absorption des OCPs par Zea mays. Le lindane semble être en partie minéralisé par la microflore rhizosphèrique puis les métabolites libérés sont absorbés par les racines, où ils sont majoritairement bioconcentrés. Ces connaissances fondamentales mettent en évidence l'adaptation de la rhizosphère à la pression chimique des OCPs et montrent que la rhizosphère reste fonctionnelle en présence de matrices contaminées par les OCPs. / Human activities lead to diffuse pollution causing damages to the ecosystem. To avoid major disturbances such as biodiversity loss or contamination of trophic chains by pollutants it is necessary to restore these ecosystems. The classical techniques used in depollution are expensive, reduce soil fertility and have a negative effect on ecosystem functionality. In contrast, the use of plants to clean up soils called phytoremediation seems to be a more effective solution. However, it needs to be improved because many biological mechanisms remain unexplained. The originality of our work is to study the functionality of the rhizosphere of maize (Zea mays) exposed to organochlorine pesticides (OCPs), lindane and chlordecone, banned in 1998 and 1993 respectively and persistent in the environment. This study will be conducted in the presence or absence of microorganisms to clarify the relationships between microorganisms and plant matrices. In this study, the mechanisms involved in the phytotoxicity of OCPs in root cells were analyzed. The cytotoxicity was dose-dependent and showed effects on the cell cycle (induction of endoreduplication and level of ploidy) and on cell death (induction of ROS, cytosolic Ca2+, caspase-3-like, apoptosis) under higher doses of exposure (particular case of former industrial sites). Lower exposures usually detected in the environment showed great disturbances in the root metabolome. These changes in sugars, organic acids, amino acids and lipids syntheses could be induced by oxidative stress provided by OCPs. Moreover, metabolome changes might cause modifications in root exudate composition which is involved in plant-microbe relationships. Ours results demonstrate that the overall rhizosphere functionality (resource allocation, carbon and nitrogen contents and microorganism's catabolism) was not disturbed by OCPs long-term exposure. Finally, we demonstrated rhizosphere positive impact on uptake of OCPs by Zea mays. Lindane seems to be partially mineralized by rhizospheric microorganisms. Then, these produced metabolites were uptaken by roots where they were bioconcentrated. These findings highlighted the rhizosphere adaptation to chemical pressure by OCPs and showed the good rhizosphere functionality despite of the OCPs contamination.

CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior / This study investigates ecological process and dynamic of the hypersaline tidal flats (HTF, locally knowns as âapicumâ). The HTF systems are characterized by flat landscape and hypersaline soil conditions that may occour in arid and semiarid regions of the world. Usually HTF can be found inside mangrove forest or as a transitional system between mangrove and dry land ecosystem. These areas are highly important for advances of mangrove forest in case of sea level increase. Besides, HTF have great economic value, as prioritarian areas to install aquaculture or saline ponds. Also it represents security zones for traditional populations, as artisanal fishermen. However, the ecological process which drives the HTFs systems remain poorly knew. The studies presented in this doctoral dissertation aim to fulfill some lacks of knowledge about ecological process that could drive the HTF dynamic. The chapter 1 is a bibliographical review about this system. On chapter 2 were evaluated possibles mechanisms used by plants in order to improve their survival in such stressed environment through the study of rhizosphere soils and comparison with bulk soils. On chapter 3, through an experimental study in the field, the possible effect of two crab species bioturbation on HTFs soils and it possible effects on soil properties were evaluated. The chapter 4 registered the evaluation of ecological interactions among biotic and abiotic fractions of the system using ecological modeling tools. In this sense, a structural ecological model was designed using microrelief elevation, soil properties, two plant species biomass and the covering areas of two crab species. Based on results obtained in these studies, it was possible to conclude that HTFs have a particular ecological dynamic and have close relation with mangrove forests due the nutrients, material and animal population flux shared by them. The plant community of HTFs areas is componed mainly by pioneersâ clonal halophytes species. These species seemed to have different strategies to deal with saline stress, an important limitant factor for their growing and distribution. The seasonal effects were noteworthy mainly in bulk soils. In this sense, it is possible that plant estabilize the environment in their benefit. The crabs were able to affect biogeochemical dynamic in HTF soils. However, the burrouing effects of crab species on soil properties were different and seemed reflect the species habit. Although bioturbation effects were important, the modifications on HTF soil properties were less evident than in mangrove forests. Environmental process related to salinity and nutrients availability are among the main factors to drive crabs distribution and plant growth in HTFs. These processes were dependent of microrelief variation. A combination of abiotic factors (microrelief elevation and soil properties) and positive relations among plant species seems to guide the ecological dynamics in HTFs systems. Conservation strategies of coastal environments areas must include the HTF protection due their importance for coastal environments on climate change scenario and economic importance, but mainly because their unique ecological characteristics. / Esse estudo teve como objetivo geral investigar processos ecolÃgicos e a dinÃmica do apicum. Esses sistemas se caracterizam por serem planÃcies hipersalinas que ocorrem em zonas costeiras de regiÃes Ãridas onde podem ser identificadas dentro de bosques de mangue ou entre o manguezal e ecossistemas de terra seca, como mata seca ou restinga. Os apicuns sÃo Ãreas estratÃgicas para recuo das florestas de mangue em caso de aumento do nÃvel do mar. AlÃm disso, possuem grande importÃncia econÃmica, visto que sÃo Ãreas preferenciais para instalaÃÃo de empreendimentos de aquicultura e salinas e por que representam zonas de seguranÃa para populaÃÃes tradicionais. Entretanto, muito pouco se sabe sobre os processos ecolÃgicos que regulam a dinÃmica do sistema. Os estudos compilados nessa tese visam de algum modo suprir lacunas sobre os processos ecolÃgicos que regem a dinÃmica desse sistema. O capÃtulo 1 traz uma ampla revisÃo bibliogrÃfica sobre esse sistema. No capÃtulo 2 foram avaliados possÃveis mecanismos utilizados pelas plantas para sobreviverem ao ambiente limitante atravÃs do estudo dos solos rizosfÃricos e comparaÃÃo com solos nÃo colonizados por plantas. No capÃtulo 3, atravÃs de um estudo experimental de campo foram avaliados os efeitos da bioturbaÃÃo de duas espÃcies de caranguejos nos solos de apicum e seus possÃveis efeitos sobre as condiÃÃes edÃficas. O capÃtulo 4 aprofunda-se na avaliaÃÃo das interaÃÃes ecolÃgicas que ocorrem entre o solo, microrelevo e a biota do sistema (plantas e animais). Nesse sentido, um modelo ecolÃgico estrutural foi construÃdo utilizando variaÃÃes na elevaÃÃo do relevo, propriedades do solo, biomassa das plantas e Ãrea de cobertura de caranguejos. Com base nos resultados, concluiu-se que o sistema apicum possui dinÃmica ecolÃgica muito prÃpria e possui uma relaÃÃo com os bosques de mangue graÃas ao compartilhamento de fluxos de matÃria, nutrientes e populaÃÃes de animais. A comunidade de plantas do apicum à composta, sobretudo por espÃcies clonais halÃfitas pioneiras e que parecem possuir estratÃgias diferenciadas para lidar com o estresse salino, fator limitante do seu crescimento e distribuiÃÃo. O efeito da sazonalidade à notÃvel, sobretudo nas Ãreas nÃo colonizadas por plantas, indicando que possivelmente as plantas estabilizam o sistema solo em seu beneficio. Diferentes espÃcies de caranguejos sÃo capazes de afetar a dinÃmica biogeoquÃmica do solo. A bioturbaÃÃo do solo pelas espÃcies estudadas provocou diferentes efeitos nas propriedades do solo, os quais parecem estar intimamente ligados as hÃbitos das espÃcies. Entretanto, as seus efeitos nos apicuns, embora importantes, sÃo menos intensos que em Ãreas de manguezais. Processos ambientais ligados à salinidade do solo e à disponibilidade de nutrientes estÃo entre os principais fatores que regem a distribuiÃÃo de caranguejos e crescimento das plantas nos apicuns. Esses processos sÃo intimamente dependentes das variaÃÃes do microrelevo. Uma combinaÃÃo entre fatores abiÃticos (elevaÃÃo do relevo e propiedades do solo) e relaÃÃes positivas entre espÃcies de plantas parecem se os princiapis agentes na dinÃmica ecolÃgica dos apicuns. EstratÃgias de conservaÃÃo de sistemas costeiros devem incluir a proteÃÃo dos apicuns visto seu importante papel ecolÃgico no cenÃrio de mudanÃas climÃticas e importÃncia para economia local, sobretudo por conta suas caracterÃsticas ecolÃgicas Ãnicas.