Dissertations / Theses on the topic 'Reproduction végétale'
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Boyer, Catherine. "Conceptualisation de la reproduction végétale à l'école primaire." Paris 5, 1998. http://www.theses.fr/1998PA05H001.
Full textThis research studies and inquires into the conditions under which the assimilation and construction of scientific knowledge operate for primary school children. For several classes, from first-years infants to second-year primary this developmental study analyses the gradual shift from the everyday situations. It underlines that the inescapable precursor elements of conceptualization-children's initial representations are found to be very distant from scientific concepts and are fraught with very stubborn obstacles. Believed not to be interrelated, these conceptions are mainly expressed at everyday level. Consequently, a break brought about by specific didactic situations is indispensable if a more scientific conception is to be obtained. Questioning, observation and experimentation thus contribute towards this break. In this process the socio-cognitive conflict proves to be crucial and promotes the predominance of scientific operative invariants. The variety of signifiants also plays an important part. As regards accession to a scientific conception, this will come from a development of relationships between the different concepts. However, although the everyday concept is found to be an obstacle, vocabulary also proves to be a source of problems for the young pupil. For any one child one and the same word will awaken different conceptions over time, just as one and the same formulation level out of context will correspond in children's minds to an everyday or scientific conception. It is in fact only by dealing with individual cases, in conjuction with reciprocal relationship, that children's conceptualization can perhaps be understood. The concepts of seed, flower and fruit thus occur in a partial relative order and, if towards the age of 9 conceptualization of vegetable reproduction becomes scientifc, this does not mean that it is yet finalized or stabilized
Villar, Marc. "Incompatibilité interspécifique chez Populus : approches physiologique et biochimique." Lyon 1, 1987. http://www.theses.fr/1987LYO10008.
Full textGaget, Mireille. "Incompatibilité interspécifique chez Populus : effet Mentor." Lyon 1, 1988. http://www.theses.fr/1988LYO10012.
Full textJnoud, Najat. "Incompatibilité interspécifique chez Populus : approches cytologique et cytochimique." Lyon 1, 1991. http://www.theses.fr/1991LYO10056.
Full textDornier, Antoine. "Dynamique et évolution des métapopulations chez les plantes : l'exemple de Crepis sancta (Asteraceae) en milieu urbain." Montpellier 2, 2008. http://www.theses.fr/2008MON20104.
Full textLandscape heterogeneity induces spatial structure of populations at a given spatiotemporal scale. These populations experiment frequent extinctions that are counterbalanced by colonization events. Metapopulation dynamics determines species viability and population spatial structure. Furthermore, selection pressures in a metapopulation context differ from those in large panmictic populations, in particular due to the transient nature of populations. Small transient populations of Crepis sancta (Asteraceae) around ornamental trees in urban environment have been studied in order to analyze species metapopulation dynamics. From 4 consecutive years occupancy data, a spatially realistic model has been parameterized. Also, genetics markers allowed us to describe dispersal processes (seed and pollen). Factors affecting extinction namely population size, inbreeding and connectivity have been studied. Finally, consequences of heterogeneous densities on mating system have been studied both both theoretically and experimentally. We show that metapopulation framework allows us to describe two general patch dynamic scenarios : a patch dynamic where local dispersal does matter in one site and a second scenario where external colonization account for metapopulation dynamics. Unexpectedly numerous seeds have been found to not come from local reproduction and we hypothesize the existence of a seed bank whose effects remain to be studied. Demographic factors explain extinction and dispersal reduces extinction risk. Finally, we demonstrated the existence of an Allee effect, which underlines the importance of the demographical context on fitness, and we analyzed theoretically its effect on the selection of self-fertilization in a metapopulation
Bittebiere, Anne-Kristel. "La clonalité : un processus majeur de la dynamique spatiale et du fonctionnement des communautés végétales en systèmes prairiaux." Rennes 1, 2012. https://tel.archives-ouvertes.fr/tel-00725017.
Full textDispersion through clonal growth may be a major process of plant community structuring especially in prairial systems where most species are clonal. These species produce genetically identical ramets organized in a network structure, whose aggregation depends on the species clonal growth strategy. The present thesis aims at analyzing and understanding grassland plant community dynamics based on spatial assembly rules of clonal species and determining its consequences on the community functioning. To achieve these goals, we used complementary experimental and modeling approaches. We demonstrated that clonal growth strategies determine community spatial structure at fine scale, generating a wide range of patterns. The species spatial pattern varied depending on the clonal growth strategies occurring in the community. This variability was suggested to result from a modification of clonal traits in response to the biotic environment. Indeed, we highlighted that the clone is able to adjust its horizontal growth according to its competitor's identity thanks to information collected by ramets. The adaptive nature of this plastic response in competition resistance was dependent on plant structural blue-print and to a lower extent on ontogeny. We also demonstrated that clonal traits had a major role in community functioning by influencing productivity, probably through the spatial patterns they drive. These results have been applied to the setting-up of herbaceous buffer strips and helped to define an optimal sowing with regard to their function of water preservation. The present thesis underlines the importance of processes operating at the clone scale for those operating at the community or the ecosystem scale
Leducq, Jean-Baptiste. "Système de reproduction, dispersion et succès reproducteurs chez une espèce végétale menacée : exemple de Biscutella neustriaca (Brassicaceae), une espèce auto-incompatible et micro-endémique." Thesis, Lille 1, 2010. http://www.theses.fr/2010LIL10015/document.
Full textIn sexual species, reproduction systems and dispersal could involve in viability of small populations by having directly an impact on individuals’ reproductive success. In plants, reproduction and dispersal are mainly passive processes and thus depend of local density in mates, isolation between populations and genetic relationships among individuals. In Biscutella neustriaca, a micro-endemic plant of the Seine river valley, we highlight a strong genetic isolation between populations corroborated by habitat fragmentation and low dispersal abilities of the species. By using phenotypic and molecular approaches, we determine that B. neustriaca is strictly self-incompatible. In this context of isolation and spatially structured genetic diversity, we wonder to what extent dispersal and self-incompatibility impact individuals’ reproductive successes. Through an ex situ experiment, we highlight both effects of pollen limitation and decrease in local density of compatible mates on maternal reproductive success decrease. In four natural populations, we identify individual reproductive potential and local density of available mates as main factors explaining male and female reproductive successes variability. Genetic factors as inbreeding depression and self-incompatibility also seem to evolve in reproductive successes in some populations. We discuss about importance of considering many factors when acting for conservation in a threatened population, the need to know the reproductive system and dispersal abilities of the species, inseparable from a monitoring of targeted populations, where effects of these factors are only detectable at certain temporal and spatial scales. We illustrate our works by a concrete conservation action in one of the studied populations
Journé, Valentin. "Influence du climat lors de l'investissement des ressources dans la reproduction chez les arbres forestiers : une approche par modélisation mécaniste." Thesis, Aix-Marseille, 2020. http://theses.univ-amu.fr.lama.univ-amu.fr/200217_JOURNE_229kn950dq423kitgvy940umn_TH.pdf.
Full textGlobal changes affect species distribution and ecosystems functioning due to long term climatic trends and extreme climatic events. Forests are notably subject to massive growth decline and even mortality. One of the major processes of forest dynamics is sexual reproduction, but there are still many uncertainties about the effect of climate on trees reproduction, especially on when and how resources are allocated to pollen and seeds. Reproduction also allows species to persist over generations, through adaptation and migration. The main objective of this thesis is to develop an approach based on resource and phenology modelling, in order to understand and predict climate effects on forest trees reproduction. First, I used statistical model to investigate temporal and spatial variation of fruit production. Second, I quantified the allocation of resources between vegetative versus reproductive functions, with a hierarchical Bayesian model and observation of growth, male and female reproduction over several years. Results allowed us to identify trade-off during floral initiation, and highlighted the importance of resources levels to ensure reproduction. Lastly, I developped a process-based model of reproduction and included it in an existing model of forest functioning (CASTANEA). The reproduction model, which runs from flower initiation to seed maturation, simulates spatial and temporal patterns of seed production. The model was calibrated and validated on silver fir on Mont-Ventoux and used to investigate how climate change will impact fruit production
Scarcelli, Nora. "Structure et dynamique de la diversité d'une plante cultivée à multiplication végétative : le cas des ignames au Bénin ("Dioscorea sp.")." Phd thesis, Montpellier 2, 2005. http://www.theses.fr/2005MON20070.
Full textMoret, Jacques. "La variation de populations méditerranéennes d'Ornitogales : conséquences au niveau de la systématique et de l'évolution du genre." Paris 11, 1985. http://www.theses.fr/1985PA112169.
Full textThe variability (in levels, degrees and diversity) of Mediterranean populations of Ornithogalum was studied according to the principles of « synthetic » Systematics (Morphology, Caryosystematics and Cytogenetics, Biology of Reproduction etc. ). The polymorphism of the populations is quite intense and manifests itself on various levels: intra-individual polymorphism of the floral characteristics; inter-individual polymorphism connected with varied modes of reproduction and to the existence of ecads and ecotypes. There are multiple ways of speciation: geographic isolation, polyploidy, restructuration of the caryotype. The most original is exemplified by O. Divergens. This species exhibits a remarkable instability in its caryotype (at the population, individual and organ levels), at the levels of both the vegetative and the reproduction systems. This instability is coupled with a mainly vegetative type of reproduction. The variability of taxons belonging to this genus was evaluated in Morocco through statistical and biological concepts of the species, based on the study of natural and experimental living populations
Danchin, Étienne. "Rôle des facteurs comportementaux dans les mécanismes de régulation des populations d'oiseaux coloniaux : cas de la mouette tridactyle (Rissa tridactyla)." Paris 6, 1988. http://www.theses.fr/1988PA066180.
Full textScarcelli, Nora. "Structure et dynamique de la diversité d'une plante cultivée à multiplication végétative : le cas des ignames au Bénin ("Dioscorea sp.")." Phd thesis, Université Montpellier II - Sciences et Techniques du Languedoc, 2005. http://tel.archives-ouvertes.fr/tel-00482798.
Full textTheodorou, Ioannis. "Cell fate and blade patterning during the early growth of Saccharina latissima sporophytes." Electronic Thesis or Diss., Sorbonne université, 2023. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2023SORUS013.pdf.
Full textSaccharina latissima is amulticellular parenchymatic photosynthetic organism in the group of brown algae (Phaeophyceae). It belongs specifically to the group of kelps (Laminariales), a group that has recently ac-quired great economic and ecological importance.Notably, our knowledge for Saccharina and the other kelps is restricted to their physiological and ecological traits while our understanding on their development is mostly outdated or incomplete. Their life cycle is diplobiotic with heteromorphous generations. Specifi-cally, the large and conspicuous plant is the sporophyte, and the microscopic stage is represented by two dioecious gametophytes.The early development of the sporophyte is a largely unknown process.The aim of this project was to elucidate the morphogenesis of Saccharina latissima’s embryos from de-scriptive and mechanistic point of view. First, we identified three main phases based on the body axes of the embryo. Phase I follows the formation of the polarised zygote, characterised by a sequence of anticli-nal transverse divisions perpendicular to the main growth axis.Then, longitudinal anticlinal divisions take place during Phase II, leading to the formation of a monostromatic grid mad of cross-aligned cuboid cells. The third growth axis is introduced during Phase III, together with the emergence of different types of tis-sue, a process defined as polystromatisation. Then (Paper I), a morphometric study was performed in Phase II. Morphometric quantitative parameters like cell division rate and orientation as well as cell shape and direction of expansion were collected and combined with hyperosmotic treatments to test simulations derived from vertex modelling. Simulations suggest that anisotropic patterns on cell wall (CW) stiffness explain the 2D morphogenesis of the embryo. Next (Paper II), we postulated that these patterns could be underlied by a specific organisation of the cytoskeleton. Observations on actin labelling show an aniso-tropic actin filaments (AFs) organisation at the cortex below the anticlinal CWs. Specifically, the cortical AFs are parallel to the future third growth axis. In contrast, the AFs below the walls of the front and rear surfaces seem isotropic. Drug treatments did not assist to establish a functional link between the CW stiff-ness and AF patterns. However, AFs potentially restrict cell growth along a 2D plane. We postulate that this pattern of AFs organisation needs to be rearranged for allowing cell growth and division along the three spatial axes, and therefore, to allow thickening of the so far monolayer lamina. Furthermore, we focused on the cellular and molecular events leading lamina thickening (Phase II to – Phase III transition). At the molecular level (Paper IV), transcriptomic analysis during the initiation of Phase III detected a downregula-tion of most of the differentially expressed genes. In addition, GO analysis indicates a switch of gene ex-pression towards signaling and post-translational modifications. However, a direct relation between the patterns of gene expression and the addition of a third growth axis has not been established.At the cellular level (Paper III),semithin sections elucidated the patterns of 3D growth and cell differentiation. Specifical-ly, polystromatisation (thickening) and cell differentiation occurs centripetally from an external epidermal meristem and propagates acropetally from the base of the embryo. Different regions of the developing thallus present different morphometries and abundance of the different cell types. For example, the older polystroma is rich in medullary elements and poor in cortical cells, and the inverse is observed in younger polystroma.My project formulates a morphogenetic model for Saccharina’s embryos, based on simple cellular me-chanics. Anisotropic patterns explain how the embryos acquire their initial shape which is the scaffold for the late 3Dgrowth accompanied by tissue emergence and a superficial meristem
Hossaert-McKey, Martine. "Des fleurs comment et à quoi bon ? : Données et réflexions sur la reproduction sexuée de deux espèces pérennes affines, à propagation végétative, Lathyrus latifolius et Lathyrus sylvestris (légumineuses, papilionaceae)." Pau, 1988. http://www.theses.fr/1988PAUU3013.
Full textBelhasnat, Ralette. "Contribution à l'étude biotechnique des élevages piscicoles en eau recyclée : Application à la slamoniculture." Nancy 1, 1988. http://www.theses.fr/1988NAN10073.
Full textPomente, Dominique. "Étude expérimentale génétique, écologique et écophysiologique du polymorphisme végétal : chémotypes et formes sexuelles du thym." Montpellier 2, 1987. http://www.theses.fr/1987MON20058.
Full textPelosse, Perrine. "Rôle des compromis évolutifs dans la spécialisation et la coexistence d'espèces compétitrices : développements théoriques et expérimentaux chez les insectes parasitoïdes." Phd thesis, Université Claude Bernard - Lyon I, 2008. http://tel.archives-ouvertes.fr/tel-00369569.
Full textMonasterio, Sarmiento Maximina. "Recherches écologiques sur les Espeletia du Paramo désertique des Hautes Andes tropicales du Venezuela." Paris 6, 1986. http://www.theses.fr/1986PA066320.
Full textGerber, Sophie. "Variabilité des protéines de l'endosperme du pin maritime révélée par électrophorèse bidimensionnelle : interprétations génétiques, cartographie et relation avec des caractères quantitatifs." Institut national agronomique Paris-Grignon (1971-2006), 1992. http://www.theses.fr/1992INAP0126.
Full textThe present work is intended as a step toward a description of the maritime pine genome (Pinus pinaster Ait. ). It initiates a study of quantitative traits variation using this description, The growth performances of the trees composing the breeding population of maritime pine are known thanks to general combining abilities measured in progeny tests. Eighteen trees representing the range of performances were sampled in this population. The variability of the proteins contained in the haploid endosperms (or megagametophytes) of these pines was studied by two-dimensional electrophoresis, An average of 12 endosperms per tree were analysed and compared. After a systematic analysis of the variation observed, 84 loci were described, responsible for position or amount modifications or presence/absence of proteins, Human genetics techniques were used to build a map. Seventeen linkage groups were detected, which included 65 loci and covered 530 centimorgans, The methods used to estimate and to test for linkage between loci are discussed. The linkage data allowed us to estimate the genome length of maritime pine, It was found to be around 2000 centimorgans, Pines contain one of the greatest quantity of DNA per cell. Some considerations about the relationship between physical and genetic maps in angiosperms and gymnosperms are thus proposed. The relationship between the weight of megagametophytes and the alleles expressed in these haploid organs was studied for every locus. The effect of three loci was detected. The diploid genotype of 18 pines for the 84 loci was compared to their growth performances thanks to different statistical techniques, The results suggest that protein amount variation could be related to quantitative traits, the usefulness and limits of quantitative trait loci (QTL), particularly for forest tree breeding, are discussed
Clabaut, Aline. "Analyse génétique de l'embryogenèse somatique chez la chicorée (Cichorium intybus L.) : cartographie des QTL et gènes candidats." Thesis, Lille 1, 2009. http://www.theses.fr/2009LIL10039/document.
Full textSomatic embryogenesis (SE) Is an asexual re-production pathway in which somatic cells form embryos in a process that resembles zygotic embryogenesis. ln chicory a genetic variability in the capacity of somatic embryo formation was found, and two contrasting genotypes were selected K59, embryogenic. and K28, hardly embryogenic were selected for obtain a F1' progeny. Vanabllity for somatic embryo formation was exploited to identify chromosomal regions (QTL) and candidate genes implicated in ES. After 7 days of culture of root explants under SE-inducing conditions and 30 days of development the number of plantlets (PL) and shoot-like structures (SH) obtained were counted. The traits PL and SH showed continuous and normal distributions after log10 transformation, and heritabilities superior to 63%. A genetic map for the K28*K59 progenies was built for a QTL analysis related to ES. Six QTL were detected for both PL and SH that together explained more than 23% and 44% of the phenotypic variation for these traits. respectively. Amongst the 63 mapped candidate genes, 16 co-Iocalised with QTL for PL and SH. ln view of their implication in the maintenance of the undifferentiated state of the stem ceIls in shoot apical meristems. the co-localisation of genes homologous to SHOOT MERISTEMLESS (STM) and ARGONAUTE (AGO) in Arabidopsis wlth QTL6 and QTL2. respectively. is a particular interesting result. With the detection of QTL for SE. the results of this study have for the first time revealed elements in the genetic control of SE in chicory
Bouchereau, Jean-Luc. "Bioécologie et tactiques adaptatives d'occupation d'une lagune méditerranéenne (Mauguio, Languedoc, France) par trois poissons téléostéens gobiidés : "Pomatoschistus minutus" (Pallas, 1770), "P[omatoschistus] microps" (Kroyer, 1838), "Gobius Niger Linnaeus", 1758." Montpellier 2, 1994. http://www.theses.fr/1994MON20043.
Full textGuillemet, Rozenn. "Incidence de l'incorporation de fibres alimentaires dans l’aliment de gestation, et de facteurs individuels sur le comportement alimentaire et les performances de la truie allaitante." Rennes 1, 2006. http://www.theses.fr/2006REN1S084.
Full textWintenberger, Coraline. "Dynamique fluviale et végétation pionnière à la Salicaceae en rivière sablo-graveleuse : études in et ex situ de la survie des semis durant les premiers stades de la succession biogéomorphologique en Loire Moyenne." Thesis, Tours, 2015. http://www.theses.fr/2015TOUR4020/document.
Full textThe present study is focused on the three first stages: geomorphic, pioneer and biogeomorphic of the Fluvial Biogeomorphological Succession applied to a sandy-gravel bed lowland river: the Loire River (in its middle reaches). This work is based on both an in and ex situ approach. It analyses the recruitment and survival during their first stages of growth of two Salicaceae trees: Populus nigra L. and Salix alba L. developed on a non-migrating (forced) bar. The dynamics of this bar influences the survival potential of seedlings during floods. The seedlings adapt morphologically according to the sedimentary structure, and as a consequence, modify their survival potential. Three conceptual models detail: (i) the dynamics of a mid-channel forced bar during floods, (ii) the longitudinal evolution of the mortality of seedlings induced by the downstream fining of sediments, (iii) the sediment archiving and time needed to reach a pioneer island state from a non-migrating vegetated bar
Lavergne, Sébastien. "Les Espèces végétales rares ont-elles des caractéristiques écologiques et biologiques qui leur sont propres ? : Applications à la conservation de la flore en Languedoc-Roussillon." Montpellier, ENSA, 2003. http://www.theses.fr/2003ENSA0011.
Full textThis thesis aims at determining general ecological and biological features among rare plants of the Mediterranean Basin, and at describing general mechanisms creating and maintaining interspecific differences in abundance and distribution. First, a methodological synthesis has been proposed, focusing on matter of rarity definitions, on biases in rarity measurements, and on methodology of determination of rarity syndromes. Then, three approaches have been used to reach the objectives of the thesis. The influence of historic, ecological and biological factors on changes in regional abundance and distribution of rare species has been studied in a Mediterranean region, from 1886 to 2001. Rare species showed a great tendency to occur in elevated zones, with extensive agricultural practices, but most of regressions and local extinction of rare species have occurred in lowland areas, where land use have been continuously intensified since the la the 19th century. Decreasing or extinct rare species arc over represented among Brassicaceae, Poaccac, Orobanchaceae, Gentianaceae et Papayeraceae, hydrophytes, chaméphytes, and among species with a large Eurosiberian distribution. On the contrary, endemic species showed high rates of local persistence from 1886 to 2001. We then undertook a pairwise comparison across 20 pairs of endemic and widespread congeners. Endemic species tend to occur in sloping and rocky habitats, with open and sparse vegetation. They also exhibit smaller statures, lower pollen ovule ratio and lower individual fecundity. Endemic species thus tend to occur in lower competitive habitats, tend to be more inbred and to have lower colonisation potential. The pair of Aquilegia species included in this survey has been further compared to quantify experimentally the relative responsibility of predation and pollination interactions on low fecundity of endemic species. Predator exclusion showed that the endemic. A. Viscosa suffered higher rates of predation. This species also has a lower reproductive success, because of a lower pollinator activity. However, the two species have the same reproductive assurance when pollinators are excluded. More generally, phylogenetic independent contrasts calculated with 18 species of Ranunculaceae revealed that range size of species is positively correlated with pollen / ovule ratio, with natural seed/ovule ratio, but not with seed/ovule ratio in absence of pollinators. In these species, mostly perennial, colonisation potential may thus have been enhanced by allogamy and reproductive success, but not by automatic selfing in the absence of pollinators. Implications of these results are discussed in conclusion, especially for delimiting decreasing species in the Western Mediterranean, and for the knowledge on endemic species biological functioning, and for the example value of the methodology used in this work
Said, Charlette. "Différenciation et reconnaissance des gamétophytes mâle et femelle chez Larix leptolepis : étude structurale." Lyon 1, 1988. http://www.theses.fr/1988LYO19007.
Full textGonnet, Jean-François. "Apport de la biologie micromoléculaire (flavonoïdes) à la compréhension de la structure et du fonctionnement de l'espèce allogame Centaurea montana (Composées) et de l'espèce autogame Chaerophyllum aureum (ombellifères) au sein de deux groupements végétaux subalpins : prairie et mégaphorbiaie." Lyon 1, 1989. http://www.theses.fr/1989LYO10022.
Full textBeuve, Francois xavier. "Problématisation, investigations et apprentissages dans les sciences de la vie. : Etude didactico-pédagogique des conditions de possibilité pour des investigations empiriques problématisantes, dans deux domaines biologiques : nutrition et reproduction végétales." Thesis, Normandie, 2017. http://www.theses.fr/2017NORMC010/document.
Full textFor several years now, and with reference to the rationalist epistemology of Bachelard, Canguilhem and Popper, the relationship between problem, scientific knowledge and learning is the focus of extensive educational research. Language holds a first choice place at the heart of this interaction, which explains more particularly the importance given to scientific debate, and whose representation of the outcome, in terms of problematizing activity, is enabled by creating “spaces of constraints and needs”, which build on the fundamental distinction of an empirical thesaurus and the thesaurus of the model [or the models], and also on the equally fundamental distinction of the apodictic and assertoric, that is what is the contingency and the necessary. Furthermore, though the scientific debate seems centered around the construction of the problem at stake, another question is raised, within the conceptual framework of problematization that we mobilize, the very function of empirical investigations, according to their own structure : are still involved in the construction of the problem at stake and, where appropriate, under what conditions ? Based on these recent findings, this research work aims at the conceptualization, the implementation and the analysis of two teaching-learning science sequence, in a class of year 9 and 10, so as to highlight some elements which may participate in the scientific case of problematization to be surveyed, more particularly in the articulation of the construction to solve the problem at stake
Marinho, Soriano ELiane. "Ecologie, physiologie et production d'agar de deux rhodophycées : "Gracilaria bursa-pastoris" et "Gracilaria gracilis" (Etang de Thau, Hérault - France)." Montpellier 2, 1997. http://www.theses.fr/1997MON20057.
Full textMsanda, Fouad. "Ecologie et cartographie des groupements végétaux d'Anzi (anti-atlas occidental, Maroc) et contribution à l'étude de la diversité génétique de l'arganier (Argania spinosa (L. ) Skeels)." Grenoble 1, 1993. http://www.theses.fr/1993GRE10084.
Full textRuaux, Brigitte. "Les plantes envahissantes des corridors fluviaux : traits biologiques, impacts de Ludwigia peploides et L. grandiflora en Loire moyenne et implications pour la gestion." Phd thesis, Université François Rabelais - Tours, 2008. http://tel.archives-ouvertes.fr/tel-00380073.
Full textCao, Vien. "Contribution à l'étude des péridiniens d'eau douce : Isolement de clones, culture, nutrition. Quelques aspects inconnus ou peu connus de la biologie de ces algues." Paris 7, 1987. http://www.theses.fr/1987PA077098.
Full textKumar, Charchit. "Quantitative and qualitative investigation of adhesion and friction on textured surfaces : inspiration from insect-plant interactions." Thesis, Strasbourg, 2019. http://www.theses.fr/2019STRAE008.
Full textAdhesion and friction exist in many technical systems as well as in natural ones. Both phenomena have a profound influence on the durability and efficiency of technical systems. A well-recognised way to tune these characteristics - besides altering the physicochemical properties - is the texturing of the interacting surfaces. Inspiringly, plant leaf surfaces are often decorated with diverse surface morphologies, and so show remarkable functionalities. This thesis aimed to perform a systematic investigation of adhesion and friction mechanics on micro-structured surfaces replicated from plant leaves, in contact with a probe, which was inspired from an insect’s adhesive pad. Surface morphologies of three different plant leaves were directly transferred onto a viscoelastic polymer. For this, three different replication approaches were comprehensively explored. Scanning electron microscopy and confocal laser scanning microscopy were used for the qualitative and quantitative evaluation of replication ability. For the contact mechanics investigation, a high-resolution nanoindenter was modified, with incorporating a unique feature to record the in-situ real-contact images. Pull-off tests were carried out to quantitatively evaluate the effect of pre-load on adhesion force characteristics and to understand distinct attachment-detachment modes. Friction investigations were performed to examine the effect of normal load and sliding speed on the friction force. Results were discussed with regard to each surface’s topography
Sellami, Jallouli Sahar. "Etude de l'homéostasie des sucres en réponse à une forte salinité chez Arabidopsis thaliana : impact sur l'anatomie des tissus vasculaires dans la hampe florale et rôle dans la tolérance Arabidopsis natural accessions display adaptations in inflorescence growth and vascular anatomy to withstand high salinity during reproductive growth Salinity Effects on Sugar Homeostasis and Vascular Anatomy in the Stem of the Arabidopsis Thaliana Inflorescence." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS549.
Full textIn Arabidopsis thaliana at the reproductive stage, the inflorescence plays an important role in the supply of nutrients through the vascular tissues of siliques and seeds. It is a model for the study of carbon allocation and sugar homeostasis in response to abiotic stress. The objective of this thesis was to study changes in the anatomy of vascular tissue and homeostasis of sugars in the main floral stem in response to salt stress, with or without acclimation to understand their contributions in the adaptive process and acclimation. First, we studied the natural variability of the growth of the inflorescence, the accumulation of sugars and the anatomy of vascular tissue in the scape in three accessions of Arabidopsis thaliana and related species halophyte «Thellungiella salsuginea ». This study showed changes in floral stem development, sugar accumulation, and vascular tissue anatomy in response to salt stress, depending on the level of tolerance of the ecotype. We have also shown that some of these modifications are related to adaptive processes to salt stress. These results suggest that the regulation of growth of the inflorescence and the adjustment of the anatomy of vascular tissues contribute to salt stress tolerance. Secondly, we studied changes of sugar transport and metabolism in Columbia accession of Arabidopsis thaliana in relation to changes in the anatomy of the vascular tissue and the composition of the secondary wall in xylem. The results show an accumulation of sugars associated with a deregulation of genes that encode for the sugar transport and metabolism. Changes in vascular tissue anatomy and in the composition of secondary wall in xylem vessels have also been observed. These results suggest a regulation of the distribution of sugars in the stem in response to salt stress that may contribute to stress tolerance. All of this work makes it possible to propose a model of the regulations acting on the homeostasis and the transport of sugars in response to salt stress in the floral stem, even if our results do not allow concluding if these processes are favorable to the production seeds and intervene in adaptation or acclimation to salt stress
Louerguioui, Ali. "Techniques de multiplication par clonage "in vitro" du genre eucalyptus." Grenoble 2 : ANRT, 1988. http://catalogue.bnf.fr/ark:/12148/cb37615472r.
Full textAl-Samman, Winkel Noura. "Quelques mécanismes contribuant au comportement pionnier de trois espèces méditerranéennes pérennes : "Dorycnium pentaphyllum Scop.", "Euphorbia nicaensis All.", et "Aphyllantes monspeliensis L."." Montpellier 2, 1992. http://www.theses.fr/1992MON20263.
Full textMallet, Bertrand. "Rôle des facteurs écologiques dans le processus de spéciation en milieu insulaire. Effet de l'habitat et des pollinisateurs sur la diversification du faham (Jumellea spp., Orchidaceae) aux Mascareignes." Thesis, La Réunion, 2014. http://www.theses.fr/2014LARE0020/document.
Full textMechanisms responsible for the establishment of reproductive isolation are little studied in island adaptive radiations. According to the theory of ecological speciation, reproductive isolation results from the ecologically-based divergent selection. By their unique characteristics, oceanic islands are ideal systems to study the role of ecological factors in the diversification of endemic lineages. This study focuses on the role of habitat and pollinators in restricting inter and intraspecific gene flow between populations of faham (Jumellea spp.), an orchid endemic to Mascarene Islands. To do this, patterns of phenotypic differentiation (floral traits), environmental differentiation (habitat, altitude, climate) and genetic differentiation (nuclear microsatellites) were compared. At the intraspecific level, the results show that gene flow restriction is mainly due to the colonization of different habitat types with no obvious role of pollinators. At the interspecific level, in addition to the role of habitat, pollinator shift seems to explain effective complete reproductive isolation. By placing these results into the continuum of speciation, it appears that reproductive isolation evolve initially in response to adaptation to different habitats and, in a second phase, would be enhanced by pollinator-driven divergent selection. Operationally, this study reviews the taxonomy of faham and proposes to define management units and priorities in terms of conservation
Albert, Arnaud. "Mécanismes de propagation du roseau commun envahisseur au Québec." Thèse, 2016. http://hdl.handle.net/1866/19564.
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