Les tempêtes sont responsables de la moitié des dégâts dans les forêts européennes. Lemassif landais a été touché par deux tempêtes. L’ancrage racinaire est une composante majeure de la stabilité des arbres. L'ancrage du pin adulte est dépendant du développement des racines au stade jeune puisqu’elles ne fourchent pas spontanément et ne possèdent pas d’axes à développement retardé. Notre but était de mettre en relation architecture racinaire, stabilité et itinéraire sylvicole. Nous avons mesuré et analysé de façon innovante l'architecture racinaire d'arbres âgés de 3 à 5 ans et de 13 ans ayant subi une tempête. Le pivot des arbres de 13 ans ne représente que 12% de la biomasse racinaire mais reste le composant majeur de la stabilité. Un ancrage efficace est assuré par un pivot vertical unique, petit et large ou long et fin, par le volume des racines profondes et par la rigidité des racines traçantes. Le maintien du tronc est uniquement lié à la rigidité de la partie centrale du système racinaire. La fonction d’haubanage des racines traçantes est faible. La taille du plus grand secteur sans racine traçante auvent et sous le vent tout comme une microtopographie importante au vent n’interviennent pas dans la stabilité. Au stade jeune, les arbres plantés présentent de nombreuses déformations des racines traçantes,déformations qui les redistribuent au hasard tout autour de la souche avant d’être rapidement incluses par la souche en croissance. Le développement du pivot est en général correct. Les différents types de labour n’impactent pas l’architecture racinaire. Les racines traçantes suivent la surface du sol et peuvent être coupées lors des entretiens de la strate basse. / Storms account for half of the damages in European forests; the Landes forest has beenheavily damaged by two major storms. Root anchorage is a major element in tree stability. The root anchorage of mature pine is strongly linked with the root development in seedlings as this species donot spontaneously fork and do not grow delayed branches. The aim of our research was to link rootarchitecture, stability and stand management practices. We measured and analyzed in an innovative way the root architecture of 3-5-year-old trees as well as 13-year-old trees from stands damaged by astorm.The 13-year-old trees, taproot only represented 12% of root biomass but still remained the maincomponent of stability. An efficient anchorage was provided by a unique vertical taproot, short andlarge or long and thin, together with a larger deep root volume. Windward shallow roots stiffness alsocontributed to stability. Stem leaning was solely prevented by the stiffness of the central part of theroot system. The guying of shallow roots did not contribute to stability. The size of the largest anglebetween shallow roots windward and leeward was not related to stem leaning. Similarly, a largerfurrow leeward did not weaken tree stability.Planted seedling show large deformations of their shallow lateral roots, randomly distributed around the stump before being later included in the growing stump. The taproot growth was generally correct. Root architecture of trees after strip ploughing was not different from those of full ploughing. Theshallow roots follow the soil surface and can be cut during mechanical weed control.

Submitted by Gabriela Lopes (gmachadolopesufpel@gmail.com) on 2017-02-08T14:02:33Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) TESE_CarlosBusanello.pdf: 2235732 bytes, checksum: e2445dbcb147a88becd9a9bd9fe1e349 (MD5) / Approved for entry into archive by Aline Batista (alinehb.ufpel@gmail.com) on 2017-02-13T12:05:47Z (GMT) No. of bitstreams: 2 TESE_CarlosBusanello.pdf: 2235732 bytes, checksum: e2445dbcb147a88becd9a9bd9fe1e349 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-02-13T12:05:47Z (GMT). No. of bitstreams: 2 TESE_CarlosBusanello.pdf: 2235732 bytes, checksum: e2445dbcb147a88becd9a9bd9fe1e349 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2016-09-06 / Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul - FAPERGS / O conhecimento da capacidade geral de combinação-CGC e capacidade específica de combinação-CEC são fundamentais para conhecer as melhores combinações em um grupo de linhagens elite de milho para um programa de melhoramento. Para identificar estas relações foi utilizado um grupo de 10 linhagens cruzadas entre si em um delineamento dialélico incluindo os recíprocos, totalizando 90 híbridos. Estes híbridos foram testados em três ambientes, Pato Branco-PR, Campos Novos-SC e Frederico Westphalen-RS representando a região Sul do Brasil na safra agrícola 2012/2013. Os efeitos aditivos foram mais importantes que os efeitos não aditivos para a variação dos híbridos. O genitor 6 foi o que apresentou a maior estimativa do efeito da CGC, com alelos favoráveis ao incremento de peso de espiga e peso de grão. Para estas mesmas características, levando em consideração a CEC, a hibridação envolvendo os genitores 1x2 promoveu aumento no ambiente 1, e a hibridação envolvendo os genitores 4x8 promoveu redução considerável destas características. A ação do ambiente interferiu na expressão da maioria dos caracteres, indicando a necessidade de conhecer os fatores genéticos e ambientais na composição de novos híbridos de milho. Para mapeamento de QTLs foi utilizado 73 linhas de introgressão provenientes do cruzamento entre B73 e Gaspé Flint seguido de retrocruzamento, esta população foi avaliada em duas condições hídricas de campo principalmente para arquitetura do sistema radicular, bem como, caracteres morfológicos e componentes do rendimento em Ravenna, Itália. Com a genotipagem das linhas pôde-se confeccionar um mapa no qual representa 80% do genoma do Gaspé Flint introgredido em B73 contendo 329 bins independentes. A utilização do software REST para quantificar as variáveis do sistema radicular em raízes de milho em condições de campo foi eficaz, rápida e precisa. A análise de QTLs indica 35 possíveis regiões principalmente nos cromossomos 1, 2 e 4 para as características de raiz, levando em consideração todas as 31 características, foram encontrados 132 possíveis QTLs distribuídos por todos os cromossomos. Para a condição de estresse hídrico observa- se que raízes que apresentam ângulo aberto, grandes áreas e peso seco sendo superficiais, reduzem o rendimento de grãos. / The understanding about general-GCA and specific-SCC combining ability are key to identify the best combinations in an elite lineage group of a maize breeding program. In order to identify these relationships, a group comprising 10 lineages crossed with each other in a diallel design, including the reciprocal crosses, totalling 90 hybrids, were used. The hybrids were tested in three different environments, Pato Branco-PR, Campos Novos-SC and Frederico Westphalen-RS, representing the Southern Region of Brazil in the agricultural harvest of 2012/2013. For hybrid variance, additive were more important than non-additive effects. Parent 6 showed the highest estimated effect of GCA, with favorable alleles for increments of ear and grain weight. For these same traits, taking into account the SCC, the hybridization involving 1x2 parents promotes an increase in the environment 1. On the other hand, the hybridization involving 4x8 parents promotes a pronounced reduction of these traits. The expression of most traits analyzed were affected by environmental action and it indicates that the understanding of genetic and environmental factors is necessary for the development of new maize hybrids. For QTL mapping, 73 introgressed lines from the crossing between B73 and Gaspé Flint followed by backcross were used and evaluated under two field water regimes. The major traits analyzed were root architecture, plant morphological traits and yield components. Based in the genotyping analysis of the lines, it was possible to obtain a map in which 80% of the Gaspé Flint genome is introgressed in B73 comprising 329 independent bins. The software REST was employed to quantify the variables of the maize root system under field conditions and it was effective, fast and accurate. The QTL analyses indicate 25 probable regions mainly in the chromossomes 1, 2 and 4 for the root traits. Taking into account all of the 31 traits, 90 probable QTLs, distributed in all chromossomes, were found. For watering stress condition, it was possible to observe that roots with open angle, bigger area and dry mass, as well as superficial, reduces grain yield.

La réponse et l’adaptation des plantes à un stress métallique mettent en jeu de nombreux mécanismes afin de limiter les effets néfastes des éléments toxiques. Bien que certains de ces mécanismes soient bien caractérisés, de nombreux acteurs cellulaires et moléculaires restent à identifier pour mieux comprendre la diversité des stratégies mises en œuvre dans ces processus complexes et vitaux pour les plantes.Dans un premier temps, nous nous sommes intéressés au rôle de deux modifications post-traductionnelles, la phosphorylation et la méthylation des protéines non-histone dans la réponse à un stress induit par deux éléments non essentiels et toxiques, le cadmium (Cd) et l’uranium (U). Nous avons analysé la dynamique de ces modifications chez trois espèces du genre Arabidopsis : A. thaliana et A. lyrata, deux espèces sensibles au Cd, et A. halleri, espèce naturellement capable de tolérer et d’hyper-accumuler ce métal toxique dans ses feuilles. En utilisant une combinaison d’analyses par Western blot et par spectrométrie de masse nous avons montré que les patterns de méthylation des protéines changent au cours de stress métalliques. Puis, nous avons analysé l’expression des gènes codant les enzymes impliquées dans les réactions de phosphorylation et méthylation des protéines dans différentes conditions de stress. Ces analyses ont montré qu’un grand nombre de protéines kinases sont régulés au niveau transcriptionnel par un stress métallique tandis que seules quelques une en ce qui concerne la méthylation. Pour finir, nous avons mis en place un criblage génétique de mutants d’A. thaliana et identifié deux gènes codant des protéines lysine méthyltransférases impliqués dans la tolérance au Cd.Dans un deuxième temps, nous avons étudié les mécanismes cellulaires de la réponse du système racinaire d’A. thaliana lors d’une exposition à l’U. L’utilisation de différents systèmes rapporteurs et la mesure de différents paramètres physiologiques nous ont permis de mettre en évidence que l’architecture racinaire est fortement modulée en réponse à l’U et ceci de façon dose dépendante. Cet effet est lié à l’inhibition du cycle cellulaire et à la synthèse d’espèces réactives de l’oxygène et d’oxyde nitrique dont l’accumulation provoque la mort cellulaire. Ces changements sont associés à une perturbation du transport et de la distribution de l’auxine dans les racines. Ces événements sont temporellement corrélés avec l’accumulation de polymères de défense (callose et lignine) impliqués dans l’imperméabilisation des cellules et des parois. Cette étude confirme enfin que le stress induit par l’U est intimement lié à une perturbation de l’homéostasie de certains macronutriments (phosphate et fer) et partage les cascades de signalisation d’une carence en phosphate.Ce travail met en évidence des mécanismes de réponse et d’adaptation aux métaux toxiques à travers la régulation fine des phénomènes de méthylation des protéines non-histone et l’identification de processus cellulaires impliqués dans la réponse à la toxicité de l’U dans le système racinaire. / Plant response and adaptation to metallic stress are involving numerous mechanisms limiting the toxic effect of metals. Although a large number of these mechanisms are well characterized, many processes are in need to be identified in order to have a better understanding of strategies involved in plant response to toxic elements.In first instance, we investigated the role of two post-translational modifications, phosphorylation and methylation of non-histone proteins in response to stress induced by two toxic metals, cadmium and uranium. We analyzed the dynamic of these modifications in three species of Arabidopsis: A. thaliana, A. lyrata two species sensitive to cadmium and A. halleri, a species which naturally tolerate and hyperaccumulate toxic metals in her leaves. By using Western blots and mass spectrometry in parallel, we showed that lysine methylation pattern were changing during metallic stresses. Next, we analyzed the gene expression of enzymes involved in phosphorylation and lysine methylation processes in plants exposed to different adverse conditions. These analyses showed that numerous kinases expressions were differentially regulated in response to metallic stress. Concerning protein lysine methyltransferases, only a few enzymes were differentially regulated. Finally, through a mutant genetic screening we identified two genes coding for protein lysine methyltransferases involved in tolerance to a stress induced by cadmium.Secondly, we studied the physiological and cellular processes involved in the response of A. thaliana root system to uranium. Through the utilization of several reporters and the measure of physiological parameters, we demonstrated that the root architecture was strongly modulated in response to a stress induced by uranium and that in a dose dependent manner. These effects are linked to a cell cycle inhibition and the synthesis and accumulation of reactive oxygen species and nitric oxyde wich participated in the root apex cell death. These changes were associated with perturbation in auxin transport and distribution at the root apex and were temporally correlated to the deposition of defense polymers (callose and lignin) involved in cell proofing and cell wall stiffness. This study is confirming the fact that uranium induced stress is intimately linked to a disruption of phosphate and iron homeostasis. Furthermore, uranium-signaling cascade are sharing a part of the phosphate starvation-signaling cascade.Together, these two studies are revealing mechanisms involved in plant response and adaptation to metallic trace elements through the thin tuning of non-histone methylation and the identification of cellular process involved in the toxicity of uranium in roots.

La Chine est actuellement confrontée à de sérieux problèmes environnementaux et est listée parmi les pays qui contribuent le plus à la pollution et à la destruction de l'environnement mondial. En particulier, la Chine du Sud est une zone naturellement sujette aux glissements de terrain à cause de conditions tectoniques, climatiques et anthropiques particulièrement défavorables. Depuis la fin des années 1990, l'Etat chinois a mis en place des politiques de reforestation de grande envergure. mais il existe des lacunes de connaissances qu'il convient de combler. En particulier, le choix des espèces les plus adaptées n'est pas aisé parce que les processus par lesquels les plantes stabilisent les pentes ont besoin d'être mieux compris.En introduction, afin de mieux préciser les périmètres qui cadrent cette thèse, sont présentées la situation de la Chine du Sud au regard des glissements de terrain, la discipline d'éco-ingénierie et les solutions qu'elle peut apporter. Ainsi, ce travail (i) se concentre sur des espèces végétales locales, (ii) se limite aux glissements de terrain superficiels, et (iii) concerne à la fois les processus mécaniques et hydriques entre le sol et les racines. A l’intérieur de ces cadres, la thèse a pour objectif de répondre à la question scientifique : quels sont les propriétés racinaires qui influencent la stabilisation des pentes ? La réflexion est ensuite appliquée aux plantes de Chine du Sud afin d’identifier les meilleures espèces-outils. Pour répondre à cette question, à la fois les données de terrain (en Chine du Sud), les expériences de laboratoire (en France) et la formulation de concepts sont mobilisées. Les résultats sont organisés en deux chapitres. Le premier pose la question de l’efficacité de la présence de racines pour stabiliser les pentes, tous d’abord sous l’angle des processus mécaniques, puis sous l’angle des processus hydriques. Le deuxième chapitre permet d’identifier un panel de traits pertinents et non redondants évaluant l’efficacité d’une espèce pour la stabilisation des pentes puis s’appuie sur ce panel afin de sélectionner les espèces chinoises les plus efficaces. Enfin, la discussion aborde les limites de ce travail et propose de nouvelles pistes de recherche.Du point de vue mécanique comme du point de vue hydrique, c’est la conjonction des effets des racines de structure et des racines fines qui importe. Les racines de structure sanas racines fines ne sont pas optimales et peuvent même faire apparaître des lignes de fragilité. Plus précisément, les racines de structure sont particulièrement bienvenues vers l’aval de la pente pour des raisons à la fois mécaniques et hydriques. Les racines fines seules ne sont pas optimales non plus, elles peuvent faire apparaître localement des zones de faiblesse qui, si elles sont proches, participeront au déclenchement d’un glissement de terrain. Des ramifications racinaires denses améliorent la stabilité mécanique. Orientées vers l’aval de la pente, elles améliorent la stabilité hydrique. Les autres traits racinaires pertinents pour évaluer l’efficacité des racines à stabiliser le sol sont la contrainte et la déformation maximale en tension, la concentration en azote et la concentration en sucres solubles. / China is currently facing serious environmental issues and is listed among the countries that contribute most to pollution and destruction of the global environment. Particularly, Southern China is naturally prone to landslides because of unfavourable tectonic, climatic and anthropogenic conditions. Since the late 1990s, the Chinese government has implemented policies of large-scale reforestation, but the question of the most suitable species is still pending. The introduction of this thesis presents the different types of landslides, the context in Southern China and what eco-engineering means, in order to clarify the boundaries within which this work is situated. Thus, this study (i) limits itself to the study of superficial landslides, (ii) fits into the requirement scheme of low-cost solutions using local plant species, and (iii) focuses on the root, plant and hotspot degradation scales. Within those geographical, sociological, political and scientific frameworks, this thesis aims to answer the following scientific question: which species and root architectures are the most efficient to stabilize the steep slopes in Southern China? To answer this question, field data (in Southern China), laboratory experiments (in France) and the formulation of concepts are mobilized. The results are organized into two chapters. The first chapter identifies a panel of relevant and nonredundant traits assessing a given species effectiveness in slope stabilization, and then draws on that panel to select the most efficient Chinese species. The second chapter raises the question of the effectiveness of the presence of roots to stabilize slopes, first in terms of mechanical processes, then in terms of hydraulic processes. Finally, the discussion addresses the limitations of that work and suggests new avenues of research. Root traits relevant to assessing the root effectiveness to soil stabilization are maximum tensile stress and strain, nitrogen concentration as well as concentration in water-soluble sugars. The most efficient species among nine pioneer species measured on the Chinese slopes are Pueraria stricta, a legume native from Southeast Asia which plantation happened from reforestation programs, and Artemisia codonocephala, a spontaneous Asteraceae native from Southern China. Recommendations regarding the nine species are presented for the use of their characteristics in eco-engineering. From the mechanical as well as the hydraulic viewpoint, the conjunction of structural roots and fine roots is determinant. Structural roots alone are not optimal and may even bring up lines of weakness. Specifically, for both mechanical and hydric reasons, structural roots are particularly efficient when they grow downslope. Fine roots alone are not optimal either, as they can produce local areas of weakness which, if they are close, can participate in the triggering of a landslide. The branching organization is also particularly important: dense throughout the root profile, branches improve the mechanical stability. Oriented downslope, branching forks improve underground water flow and thus hydraulic stability. The limits of this thesis point out the difficulty to choose indicators and to follow their evolution over time. Another limitation lies in the difficulty to assess the relationship between roots and soil, as the only root resistance is not sufficient to prevent soil from sliding. Finally, the spatial integration of root properties remains challenging. In conclusion, this thesis contributes to improve the knowledge of the plant material available in the mountains of Southern China. Its results will optimize eco-engineering actions related to slope stability. It also upgrades the knowledge about processes at stake between roots and their environment during a landslide

No description available.

The research presented in this thesis investigated the functional morphology in root<br />systems in relation to their role in providing anchorage and stability for the plant. The<br />anchorage of different types of root systems was investigated as well as the influence of<br />several environmental factors on their development. The research presented in this study<br />was completed by carrying out a series of modelling, glasshouse and field experiments<br />using physical models and real plants.<br />Model experiments showed that solid shapes like bulbs are very well suited to resist<br />vertical upward forces, i.e. uprooting, and shed some light on the mechanism of<br />anchorage in bulbs. The results of this laboratory study showed that the concept of<br />optimal bulb shape for resisting uprooting is viable. Uprooting tests on real bulb plants<br />confirmed the theoretical predictions about it, and showed the importance of bulbs in<br />anchorage. This study also proved that the soil type is very important when considering<br />the anchorage of solid forms such as the bulbs.<br />A second model study showed that the simplest models of tap root-dominated root<br />systems increase their resistance to overturning with the third and second power of the<br />embedment depth in cohesionless and in cohesive soil respectively. Anchorage strength<br />of a root system dominated by a tap root will be maximised with minimum investment<br />in structural material if the rigid tap root is extended to the largest possible depth.<br />Glasshouse experiments investigated the effects of soil compaction and temperature,<br />two of the most important environmental factors, on the axial and lateral development<br />and growth of the root systems of two species of young pines. It was shown that the rate<br />of root axial development in both investigated species decreased with an increase in soil<br />compaction whereas the lateral proliferation of their roots systems was not significantly<br />affected by soil consistency. A temperature of around 15°C seemed to be optimal for the<br />root elongation rate since the increase in axial length of the roots of both species was<br />largest at this temperature.<br />The effect of mechanical stimulation as a factor in shaping the root systems of plants<br />was also investigated. Apart from the changes caused to the parts of the tree above<br />ground, unidirectional periodical flexing induced an increase in total root CSA and<br />larger biomass allocation to the roots parallel to the plane of flexing which, in turn,<br />resulted in a larger number of major lateral roots with larger CSA in the plane of<br />flexing.<br />Mechanical and morphological field studies on two Pinus species investigated the<br />anchorage of plate root systems and showed that lateral roots in older trees are not the<br />major source of root anchorage in either of the species; although in both species a<br />certain asymmetry in the distribution of major lateral root CSA was recorded, it was not<br />significantly correlated to the asymmetry in anchorage.