Дисертації з теми "Plantes aquatiques – Effets du stress"
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Thouvenot, Lise. "Stratégies de réponse de l'espèce invasive Ludwigia grandiflora aux contraintes environnementales." Rennes 1, 2012. http://www.theses.fr/2012REN1S141.
The success of invasive species depends on the characteristics of exotic species (their biological traits) and the characteristics of their introduced habitats (biotic and abiotic characteristics). The success of these species will depend on their response strategies to environmental constraints. In this thesis, we focus on the the Large Water Primrose plant species, Ludwigia grandiflora subsp. Hexapetala,. This amphiphyte species is considered as the most invasive aquatic plant in France. The present thesis aims to improve our knowledge on the adaptive strategies of Ludwigia grandiflora to environmental constraints in order to better understand and explain its invasive success. The responses of this species to abiotic parameters and biotic interaction were investigated using a functional traits approach. To achieve these goals, we conducted microcosm and mesocosm experiments. We demonstrated that L. Grandiflora possesses a large adaptive capacity to respond to fluctuations of abiotic factors (e. G. Variation of water depth, light intensity, salinization of ecosystems). Furthermore, our results showed that L. Grandiflora had a high growth rate, compensated herbivore damages and was able to produce a dense canopy in response to competition. However, the response strategy of L. Grandiflora to biotic pressure (competition and predation) depended on its own density, on the density and the status (native vs exotic) of neighboring species and on its environment (terrestrial vs aquatic). The response strategies of L. Grandiflora face to abiotic parameters and biotic pressure could explain its invasive success
Vijayaraj, Vinita. "Understanding regime shifts in shallow lakes subject to multiple stresses : Individual and combined effects of agricultural runoff and climate warming on submerged macrophytes." Electronic Thesis or Diss., Université de Lorraine, 2022. http://www.theses.fr/2022LORR0076.
Submerged macrophytes stabilize the clear-water status in shallow lakes, supporting many ecosystem services. Shallow lakes are exposed to agricultural runoff (ARO) containing pesticides and nutrients, which can affect macrophytes and threaten the clear-water state. Recent studies show that nitrate may affect macrophyte growth and species richness. Pesticides can also affect macrophytes directly or indirectly by disrupting biotic interactions. Climate warming is an additional stress to shallow lakes. lncreased temperatures may promote phytoplankton growth and nutrient release or can modify top-down control. The combined stressors may have additive, synergistic or reversed effects, and these effects are difficult to predict. The objectives of this thesis were to investigate (1) the individual and combined effects of nitrate, pesticides and climate warming on macrophytes (2) whether upscaling from micro- to mesocosms would preserve the response of macrophytes; and (3) whether the stressor effects could be detected in the macrophyte physiology. Several experiments integrating different functional groups (macrophytes, phytoplankton, periphyton and their respective consumers) were performed under controlled conditions (laboratory microcosms). These ecosystem models were exposed for several weeks to a simplified cocktail simulating an ARO (nitrates alone or mixed with 4 pesticides) at two temperatures (ambient and +4°C). Following this, more realistic ecosystems were studied using outdoor mesocosms exposed to ARO and simulating the same type of heating (semi-controlled conditions). ln all these experiments, the response of the macrophytes was documented by measuring their growth (biomass, size) and physiology (photosynthetic pigments, phenolic compounds, anthocyanins, elemental stoichiometry). Results from the microcosms showed that all functional groups were affected directly or indirectly by the tested stress factors. Pesticides alone but not nitrate reduced macrophyte biomass. Nitrate and pesticides in combination acted synergistically reducing the resilience of the macrophyte-dominated state. Warming marginally promoted macrophyte growth but together with ARO reduced macrophyte growth (objective 1). Results from the mesocosms showed that the strong negative effect of ARO on the growth of macrophytes was preserved in the outdoor mesocosms but only at ambient temperature. Warming enhanced macrophyte growth, similar to the microcosms, but also significantly buffered the ARO effect, highlighting different responses compared with the microcosms (objective 2). Complex biotic interactions along with invasions of invertebrate larvae may have reversed responses to the stressors. Besides their effects on growth, ARO and warming had a significant effect on the content of carotenoids, phenolic compounds and stoichiometry. These results need to be confirmed to determine their relevance as early warning signals of stress (objective 3). This thesis shows that the exposure of shallow lakes to ARO can induce regime shifts by tipping the system towards a degraded state dominated by phytoplankton. ln particular, the role of nitrate, which is much less studied compared to phosphorus, is clearly highlighted. Despite the positive effects of warming on macrophyte growth, the three stressors combined (pesticides, nitrates and warming) reversed the expected effect and led to a sharp decline in macrophyte biomass. The change in scale achieved confirms the need to better take into account the complexity of biotic interactions for a more reliable assessment of the environmental risks to which aquatic ecosystems are exposed
Gillard, Morgane. "Réponses de plantes aquatiques invasives au réchauffement climatique." Thesis, Rennes 1, 2016. http://www.theses.fr/2016REN1B014/document.
Climatic models predict a rise of globale surface temperature about 1 to 4°C by 2100. Climate modifications generated by this warming might favor biological invasions. The general objectif of this thesis was to explore the impacts of climate warming and climate change on four macrophytes invasive in Europe. This work focused on germination, growth, physiology and distribution of these species, through experiments in controlled conditions, in experimental garden and by using species distribution models. We showed that i) higher temperatures favor moderately the germination capacity of Ludwigia hexapetala and Ludwigia peploides subsp. montevidensis, decrease the seedlings survivorship but improve their biomass production, ii) the effect of increased temperature on macrophytes depends on the season, iii) a 3°C warming can modify metabolism without generating changes on the growth, iv) the water primroses L. hexapetala is the only species that showed both better apical and lateral growth when facing a warming, v) models predict an increase of the distribution surface of Ludwigia spp., Myriophyllum aquaticum and E. densa in their invasive ranges, and a decrease of their distribution area in the other continents, including their native range. This thesis offer a better understanding of climate changes consequences on invasive macrophytes in order to anticipate their futur colonisation potential
Puijalon, Anne Sara. "Stratégies adaptatives des végétaux aquatiques et stress mécaniques : réponses morphologiques et plasticité phénotypique." Lyon 1, 2008. http://www.theses.fr/2008LYO10117.
Adaptive phenotypic plasticity results in an improvement of plant performance and hence an increase of fitness. This study focused on plastic responses of two higher aquatic species exposed to hydraulic stress (current). This study revealed two contrasting ategies: high resistance to breaking and uprooting for the first one vs. Escape from stress (size reduction) for the other one, without decrease of fitness. The latter species displayed an altered clonal growth pattern in response to hydraulic stress (e. G. More compact growth form, high clonal growth to the detriment of vertical expansion of the main individual). The stress release leads to compensatory growth at both individual and clone scale. The morphological response to hydraulic stress is regulated by the nutrient level (growth favored for intermediate velocity and high nutrient levels)
Breugnot, Emilie. "Déterminisme spatio-temporel des peuplements macrophytiques en grands cours d'eau : application à la Garonne et à la Dordogne." Bordeaux 1, 2007. http://www.theses.fr/2007BOR13380.
Aquatic macrophytes are a functional group of hydrosystems with numerous ecological rules. Large rivers are ecosystems often impacted by human activity and present strong physical constraints. However, large rivers have been little studied. The principal aim of this study is to analyse the determinism of the macrophytes communities with a multi-scale approach (different space and time scales) in eight sites on the rivers Dordogne and Garonne. Ranunculus fluitans communities are similar in the two rivers and are characteristic of meso-eutrophic and running waters. Physical parameters (depth, substratum, water velocity) represent the principal factors affecting the floristic composition and the abundance of the macrophytes at the station scale as well as at the local scale. Compared with small rivers, chemical parameters only have little influence. The hydrological factors are especially structuring at the different temporal scales. Floods are the major source of disturbances and their impacts are often observed during several years. We showed the complex interactions between plants and flow. The macrophytes especially modify the water heights and velocities. Using a biological growth model (Gompertz model) associated with the hydrological constraints we proposed the bases of a dynamic model of growth for the aquatic macrophyte communities in large river. This thesis allowed us to improve knowledge on the functioning of plant communities in large rivers and to evaluate the implication of these results for surveying and sampling macrophytes in large rivers especially when applying the Macrophyte Biological Index for Rivers
Mialoundama, Samba Alexis. "Régulation moléculaire du métabolisme secondaire chez les plantes au cours du développement et sous l'effet du stress." Strasbourg, 2009. http://www.theses.fr/2009STRA6215.
Ponts, Nadia. "Influence de stress oxydatifs sur la biosynthèse de mycotoxines de Fusarium spp. Contaminantes de l'épi de maïs." Bordeaux 1, 2005. http://www.theses.fr/2005BOR13112.
Pierrugues, Olivier (19. "Caractérisation moléculaire de deux gènes AtPap2, codant des lipides phosphate phosphatases chez Arabidopsis : implication potentielle d'AtPap2a dans la signalisation du stress." Aix-Marseille 1, 2000. http://www.theses.fr/2000AIX11021.
Lopez, Félicie. "Identification et étude de l'expression de deux gènes en réponse au stress salin chez "Raphanus sativus"." Montpellier 2, 1996. http://www.theses.fr/1996MON20025.
Boscari, Alexandre. "Mécanismes de l'accumulation des bétai͏̈nes en réponse au stress osmotique chez Sinorhizobium meliloti en culture libre et lors de la symbiose avec Medicago sativa : importance du transporteur de bétai͏̈nes, BetS." Nice, 2004. http://www.theses.fr/2004NICE4035.
Frigerio, Sara. "Plant response to abiotic stress : analysis of changes in the photosynthetic apparatus at both gene and protein level." Aix-Marseille 2, 2008. http://www.theses.fr/2008AIX22076.
Dans la première partie du travail, il a été analysé le comportement des différents subunités appartenantes à la famille multigénique du Lhcb, dans réponse à des différentes conditions de croissance en maïs (Zea mays). La redondance de ces séquences, en effet, a suggéré un possible rôle spécifique de chaque produit génique dans la capture de la lumière et dans la photoprotection, sur la base des conditions environnementales. Les plantes ont été poussées en différentes conditions de lumière et température, pour ensuite en isoler les tylacoides au fin de les tester pour l’accumulation des protéines des antennes (Lhc). Des significatives différences ont été relevées dans les antennes, soit majeurs (LHCII) que mineurs, du Photosystème II (PSII) et, en détail, la température a joué un important rôle, puisque le rapport LHCII/antennes mineures a montré une augmentation avec la diminution de la température. Le froid, en effet, est un facteur de stress assez puissant, dès qu’il réduit énormément la vitesse de transport des électrons au niveau de l’oxydation du QH2 de la part du Cytb6f, en déterminant un excès de réduction du plastoquinone. Dans la deuxième partie de cette thèse, la régulation par les conditions environnementales des polypeptides qui constituent l'antenne photosynthétique a été analysée en employant un mutant d’orge (Hordeum vulgare), viridis zb63, qui manque du Photosystème I, ce qui produit la réduction du plastoquinone et mime une surexcitation chronique du Photosystème II. [. . . ]
Adt, Isabelle. "Influence de facteurs environnementaux sur la physiologie et le métabolisme de SINORHIZOBIUM MELILOTI M5N1." Compiègne, 2002. http://www.theses.fr/2002COMP1421.
Liu, Ziqiang. "Molecular analysis and functional characterization of Nucleosome Assembly Protein 1 (NAP1) family proteins in plants." Université Louis Pasteur (Strasbourg) (1971-2008), 2008. http://www.theses.fr/2008STR13132.
Ben, Ali Doha. "Production de dianthalexine et de protéines b dans des cellules de Dianthus caryophyllus L. élicitées par Phytophthora parasitica Dastur : approche de la voie de synthèse de la phytoalexine." Lyon 1, 1985. http://www.theses.fr/1985LYO11665.
Pianelli, Katia. "Recherche des déterminants moléculaires de la tolérance aux métaux lourds dans la plante hyperaccumulatrice Thlaspi caerulescens : Analyse du rôle de la nicotianamine dans la tolérance au nickel." Montpellier 2, 2004. http://www.theses.fr/2004MON20203.
Brunissen, Laurence. "Interactions plantes-phloémophages : modalités et conséquences des réponses systémiques induites lors d’un stress." Amiens, 2009. http://www.theses.fr/2009AMIE0121.
Plants respond to biotic and abiotic damages by activating a wide range of plant defence mechanisms, which can durably alter their physical and chemical properties. Consequently, plant induced responses may alter the relationships between phytophagous insects and their host plants. This project allowed to evaluate effects of several stresses of Solanum tuberosum on its relationship with aphids Myzus persicae and Macrosiphum euphorbiae. We measured the systemic effects of previous infestations by aphids, of both biotic and abiotic damages by chewing herbivores or mechanical lesions, and finally of exogenous treatment with methyl-jasmonate on behaviour and performance of aphids. Results showed that both behaviour and performances may be altered by systemic plant induced responses. These effects could have important consequences on aphids colonisation processes and also partly explain how aphid populations are distributed in their natural habitat. These results also revealed the ability of aphids to manipulate induced responses of their host plants. To determine phloem sap proteins involved in plant response to aphids, we analyzed for the first time the phloem exudate proteome of S. Tuberosum by two-dimensional differential electrophoresis. This technique allowed to separate numerous peptides, but also to successfully detect changes in protein profiles after aphid infestations and mechanical damages. These researches give new opportunities of using plant induced responses to develop new strategies to control aphid populations
Dupuis, Isabelle. "Fécondation in vitro chez le maïs : étude de la réceptivité femelle et des stress thermiques." Lyon 1, 1990. http://www.theses.fr/1990LYO10079.
Heydarizadeh, Parisa. "Regulation of secondary compounds synthesis by photosynthetic organisms under stress." Thesis, Le Mans, 2015. http://www.theses.fr/2015LEMA1019/document.
Under stress, photosynthetic organisms reoriente their metabolism toward the production of high added value molecules. Regarding the importance of this process, it is surprising that the processes on which the reorientation relies are still not better understood. This thesis aims to provide new information regarding these processes. The 1st part of this thesis is dedicated to the effects of 3 different light intensities on the carbon metabolism of the diatom Phaeodactylum tricornutum. The impact of light intensities higher than 300 µmol photons m-2 s-1 (ML) were different from those obtained with 30 µmol photons m-2 s-1 at the physiological and molecular levels. Carbon deficiency was responsible for the occurrence of plateau phase in cultures. Except lag phase, lipid synthesis was higher under ML In contrast, protein and chrysolaminarin syntheses increased under 1000 and 30 µmol photons m-2 s-1, respectively. Gene expression modifications suggest that the reversible conversion between phosphoenolpyruvate and pyruvate constitutes a key step for the orientation of intermediates to either high value molecules biosynthetic pathways. The physiological state of the cells should be taken into consideration when samples comparison is considered.The 2nd part of the report is dedicated to the effects of light quantity and quality (blue, red, 70% red+30% blue and white light delivered by LED) on the regulation of essential oil synthesis in 3 Mentha species collected in nature. The light quality impacts the strategy of carbon utilization by the plant. Typically, red light was the most effective for stimulating the production of essential oil in Mentha sp. while carbon fixation capacity was similar to that found in other ligthing conditions. Regardless the light intensity, Glomus mossae was the only arbuscular mycorrhizal fungus able to enhance additionally essential oil production
Mir, Derikvand Mohammad. "Relations entre la lignification et la réponse à la sécheresse." Paris 11, 2008. http://www.theses.fr/2008PA112272.
Drought is an important abiotic stress which affects many metabolic pathways in plants. Recently, preliminary data, mainly from global transcriptome studies, have suggested that lignification may be involved in drought stress tolerance; however no lignin-specific investigations had been performed. The main objective of this thesis, therefore, was to study the relation between lignification and drought stress tolerance using Arabidopsis thaliana as a model for vascular plants. A progressive drought stress protocol was established. The expression pattern of 14 genes involved or potentially involved in the lignin-specific pathway was determined using RT-PCR on the WS ecotype at two developmental stages. At the rosette stage, CADB2, CADG and CADA were upregulated in response to drought. Subsequently, at the flowering stage, F5H1, COMT1 and CADB1 were induced. The up- or down-regulated mutant lines for F5H1, COMT1, CADB2 and CADG genes were used in order to determine the potential impact of the mutations on biomass production under drought conditions. Although in some cases, significant differences between wild type and overexpressing or repressed mutant lines were found, this was not sufficient to demonstrate a major role of these genes in response to drought stress. Lignin analyses of WS and Col0 wild type ecotypes indicated that drought stress accelerates lignification and modifies lignin composition transiently in young plants. The increase level in sinapoyl malate, a soluble phenolic, could be correlated with the induction of F5H1 and COMT1. In parallel, T-DNA knock-out mutants for cinnamoyl CoA reductase 1 and 2 (CCR1 & CCR2) involved in the lignin biosynthesis pathway were characterized. The two ccr1 null mutants had a stunted phenotype, partial sterility and delayed senescence when compared to wild type. Biochemical analyses showed that their lignin content was reduced (25-30%) with more condensed lignin which had incorporated ferulic acid. Modification of the pools of sinapoyl malate and flavonoids was observed suggesting redirection of feruloyl-CoA to cell wall-bound ferulate esters and to sinapoyl malate and feruloyl malate. In contrast, no modification of these traits was detected in the ccr2 mutant demonstrating a major role of CCR1 in lignification
Petit, Anne-Noëlle. "Effets de fongicides anti-Botrytis sur les organes végétatifs et reproducteurs de la vigne." Reims, 2008. http://theses.univ-reims.fr/exl-doc/GED00000827.pdf.
In the vineyard, the use of fungicides is necessary to control grey mould caused by the phytopathogenic Botrytis cinerea. Three applications of botryticides are recommended: at the end of flowering (stage A), at bunch closure (stage B), and at the beginning of berry ripening (stage C). Fludioxonil and fenhexamid belong to two different chemical classes and are commonly used as botryticides. To reduce pesticide use, it’s necessary to improve the knowledge about chemical effects on plant physiology. Therefore, effects of these botryticides have been evaluated on grapevine vegetative and reproductive organs. Indeed, photosynthesis performed in vegetative organs provides the energy and structural substrates for plant growth. Considering reproductive organs, their development is related to the yield. Therefore, the photosynthesis was used as a physiological parameter to study stress caused by fungicides on vegetative organs. Plant defense responses have also been analysed because chemical stress induced by botryticides could activate these responses. Considering the fungicide effects on reproductive organs, various factors which could influence their efficacy were followed: (i) treatment stage, (ii) fungicide mode of action, (iii) selection pressure exerted by fungicides on B. Cinerea and (iv) grapevine defense responses
Al, Gehani Idress. "Effet des stades d'application et de l'intensité de stress hydriques répétés sur l'état hydrique et la croissance des plantes et des fruits de tomate." Avignon, 2005. http://www.theses.fr/2005AVIG0315.
Repeated water stress treatments of moderate intensity (pre-dawn leaf water potential from –0. 6 to –1. 3 MPa) and high intensity (pre-dawn leaf water potential from –1. 4 to –2. 0 MPa) were applied on tomato (Lycopersicon esculentum Mill. Cv Raïssa) plants growing in a greenhouse during the flowering and fruit growth stages for three successive years. The growth of shoots and fruits reduced with only one cycle of water stress treatment applied. When water stress treatment to be repeated, the water supply of the plants is strongly improved as well as the water supply and the dry matter accumulation of the fruits about +100% compared to the fruits developed by plants with only one cycle of water stress treatment, which results in a doubling of the water use efficiency. The stressed plants are able to develop an osmotic adjustment strategy whenever the stress intensity is high. Fruit osmotic potential decreased and accompanied by higher contents of soluble sugars (glucose and fructose) and of some organic acids (malic and citric acid). Water stress also reduces the loss of firmness of small size fruits. The firmness correlated strongly with fruit water potential but poorly with osmotic and turgor potential
Mediouni, Chamseddine. "Analyse des voies de détoxification des métaux lourds chez les plantes et lien avec les réponses cellulaire et moléculaire après traitement aux agents génotoxiques." Strasbourg, 2009. http://www.theses.fr/2009STRA6213.
This work presents the response of plants [tomato, Arabidopsis thaliana Col0 and A. Thaliana cad2 mutant, defective in the glutathione (GSH) biosynthesis pathway] to heavy metal excess. At the physiological level, the treatment with cadmium or copper induce plant growth inhibition, more pronounced at high copper concentration. Differences in heavy metal toxicity could be linked to variation of heavy metal tolerance mechanisms like phytochelatine chelation. At the biochemical level, the two heavy metals induce oxidative stress. In response to ROS accumulation, there is an increase of antioxydative enzyme activity in the leaves of wild type plants, whereas, the lack of GSH biosynthesis leads to the lack of antioxydative response in the cad2 mutant. At the molecular level, cadmium and copper induce, essentially via ROS accumulation, DNA double strand break (DSBs) in the leaves of Arabidopsis thaliana Col0 and of the mutant cad2 and cell death in the leaves and the roots of both plant types, characterized by an induction of specific gene expression. On the other hand, a high induction of cell death is related to a great accumulation of DSBs and the lack of repair gene induction. This suggests that cells are directed towards cell death rather than to DNA repair if DNA damages are to much accentuated
Chu-Ky, Son. "Fluidité membranaire en relation avec l’adaptation de la bactérie lactique Oenococcus oeni au milieu vin." Dijon, 2005. http://www.theses.fr/2005DIJOS063.
Oenococcus oeni is the lactic acid bacterium mainly responsible for malolactic fermentation in winemaking processes. Stress response plays a key role for the growth of this bacterium in hostile media such as wine. The regulation of membrane fluidity is one of the mechanisms involved in this adaptation. Membrane fluidity was monitored by using fluorescence anisotropy with 1,6-diphenyl-1,3,5-hexatriene (DPH). Cold shock has been shown to counteract the deleterious effect of acidity and ethanol on the membrane by rigidifying the membrane and by increasing the viability of O. Oeni. Adaptation of cells to stress conditions induced increases in saturation and cyclisation degrees of O. Oeni membrane lipids. The regulation membrane proteins / lipids ratio played a primordial role in stress resistance. Finally, the O. Oeni cfa gene encoding the Cyclopropane Fatty Acids (CFA) synthase involved in the biosynthesis of CFA was characterised
Abdul, Razzak Nawroz. "Caractérisation fonctionnelle de la famille CYP98 de cytochromes P450 chez Arabidopsis thaliana." Strasbourg 1, 2006. http://www.theses.fr/2006STR13010.
Together in silico and genetic mining approaches have recently designated the CYP98 family of plant cytochromes P450 as the family of enzymes that catalyzes the meta-hydroxylation step in the phenylpropanoid pathway. The meta-hydroxylation of phenolic precursors proceed via shikimate or quinate esters. Three genes belonging to the CYP98 family, CYP98A3, CYP98A8 and CYP98A9, have been reported in Arabidopsis thaliana. Analysis of EMS mutants and expression analysis demonstrated the involvement of CYP98A3 in the synthesis of lignin monomers. In this work, different Arabidopsis transgenic lines down-regulated ou up-regulated for the three genes belonging to the CYP98 family have been investigated. As expected the CYP98A3 down-regulated lines (nul and co-suppressed mutant) showed altered lignin content and composition (H lignin instead of G/S lignin). These plants also exhibited a strikingly reduced size. The reasons for the changes in plant size and inhibition of development are analysed. This analysis indicated a direct impact of meta-hydroxylated phenolic precursors on cell growth. This analysis also revealed the existence of an alternative meta-hydroxylation pathway in A. Thaliana. A role of meta-hydroxylated phenolic precursors in cell and plant growth is confirmed by the analysis of wild-type traitement with coumaroyl shikimate and caffeoyl shikimate and the analysis of overexpression mutants of CYP98A3. Plant development, biomass, and seed production was significantly increased by CYP98A3 overexpression. The impact on lignification and seed compositions was assessed. The CYP98A3 gene expression is manly detected in lignifying tissues. We showed, using promoter-GUS transformants that the CYP98A8 and CYP98A9 are expressed only in stamen (tapetum and developing pollen grain) in the young floral buds. CYP98A9 expression is also induced by biotic and abiotic stress. Analysis of stress resistance of CYP98A9 overexpressing and silenced mutants demonstrated that it plays a significant role in the plant protection against bacterial and fungal pathogens and abiotic stress
Moisy, Cédric. "Analyse structurale et transcriptionnelle des rétrotransposons du génome de la vigne, Vitis vinifera L." Strasbourg 1, 2008. http://www.theses.fr/2008STR13038.
Feki, Mohamed. "La sécheresse bioclimatique estivale en Kroumirie et dans les Mogods (Tunisie) : estimation à partir du stress hydrique de la végétation." Aix-Marseille 1, 2006. http://www.theses.fr/2006AIX10100.
Shekafandeh, Nobawdegani Akhtar. "Régénération par gynogenèse in vitro chez le blé dur (Triticum durum) et l'orge (Hordeum vulgare) : obtention de plantes selon diverses modalités d'application de stress salins." Vandoeuvre-les-Nancy, INPL, 1998. http://www.theses.fr/1998INPL070N.
Bashandy, Talaat. "Analyse d'un double mutant de thiorédoxine réductase d'Arabidopsis thaliana : étude de la redondance fonctionnelle des régulations dithiol disulfure." Perpignan, 2010. http://www.theses.fr/2010PERP1004.
Intracellular redox status is a critical parameter determining plant development in response to biotic and abiotic stress. Thioredoxin (TRX) and glutathione are key regulation pathways of thiols redox homeostasis. The main goal of my PhD is to study the interplay between these two redox pathways. NAD(P)H-dependent thioredoxin reductases (NTR) are the reducers of cytosolic and mitochondrial TRX. In contrast to mammals, the inactivation of both NTR (ntra ntrb) in Arabidopsis do not lead to lethality. Ntra ntrb plants are fertile and only show a limited growth phenotype. We performed a transcriptomic analysis of the ntra ntrb mutant. Interestingly, we observed an overexpression of several genes implicated in the flavonoids biosynthesis leading to overaccumulation of flavonoids in the mutant and protecting the ntra ntrb mutant plants against UV radiations (Bashandy et al, Mol. Plant 2009). The GSH pathway was shown to play a major role in compensating the inactivation of NTR (Reichheld et al, 2007). To confirm genetically the role of GSH in absence of NTR we associated the ntra ntrb and the glutathione biosynthesis mutant cadmiumsensitive2 (cad2). Cad2 is a weak allele of the glutathione biosynthesis enzyme GSH1 gene, having a 30% glutathione content and being aphenotypic under normal growth conditions. We found that these two thiol reduction pathways interfere with developmental processes through modulation of auxin signaling. The triple ntra ntrb cad2 mutant develops almost normally at the rosette stage but failed to generate lateral organs from the inflorescence meristem, producing almost naked stems that were reminiscent of several mutants affected in polar auxin transport (PAT) or biosynthesis. The triple mutant exhibited other defects in processes regulated by auxin, including a loss of apical dominance, vasculature defects, and reduced secondary root production. Furthermore it has lower auxin (IAA) levels and decreased capacity for PAT, suggesting that the NTR and glutathione pathways alter both auxin transport and metabolism. Thus, our data provide a mechanism to fine-tune plant development in response to environmental constraints (Bashandy et al, Plant Cell 2010)
Magnan, Fabienne. "Analyse fonctionnelle d'une protéine de type calmoduline d'Arabidopsis thaliana (AtCML9) : rôle dans les réponses des plantes aux contraintes de l'environnement." Toulouse 3, 2007. http://www.theses.fr/2007TOU30041.
Alami, Sophia. "Action de stress physiques (froid, obscurité) sur le développement et la viabilité du pollen de plusieurs variétés de sorgho-grain : incidence sur le métabolisme des acides nucléiques dans les méiocytes et le tapis." Toulouse, INPT, 1988. http://www.theses.fr/1988INPT004A.
Mony, Cendrine. "Plasticité phénotypique et compétitivité chez les hydrophytes : étude expérimentale et de modélisation de Ranunculus peltatus Schrank." Metz, 2003. http://docnum.univ-lorraine.fr/public/UPV-M/Theses/2003/Garbey.Cendrine.SMZ0330.pdf.
Phenotypic plasticity is an important aspect of how plants develop, function and evolve in their environments. This thesis aimed at investigating the ecological significance of plasticity in hydrophytes and analysing its influence on plant competitiveness. We selected, as a study model, Ranunculus peltatus Schrank, well-known for its high plasticity. Its adaptations to nutrient or light stress and to disturbances were analysed through in situ, laboratory and semi-controlled experiments and a modelling approach. The following results were highlighted: R. Peltatus adapted its biological traits according to stress and disturbance via different resource allocation patterns. R. Peltatus rapidly adjusted its morphology in response to variations in shade and water depth following classical adaptive patterns. Adaptations developed in response to nutrient stress were essentially physiological and consisted mainly in the increase of nutrient uptake and nutrient-use efficiency in stressful conditions. With respect to disturbance, R. Peltatus regeneration types were plastic. Mechanistic modelisation was used to simulate and improve the understanding of adaptative patterns highlighted experimentally. This approach constituted a first step in the evaluation of costs and benefits of a physiological adaptation in response to environmental stress. Hence, adaptive plasticity favours R. Peltatus competitiveness and its ability to colonise and adapt to new sites. A large number of hydrophytes possesses this capacity. Its competitive interests is therefore essentially dependent on the plant combination of traits and on the amplitude and dynamic of their plastic adjustments
Turc, Benjamin. "Dynamique des réponses physiologiques, structurales et moléculaires au stress O₃ dans les feuilles de peuplier." Electronic Thesis or Diss., Université de Lorraine, 2021. http://www.theses.fr/2021LORR0334.
With background concentrations having reached phytotoxic levels during the last century, tropospheric ozone (O₃) has become a key climate change agent, counteracting carbon sequestration by forest ecosystems. Impacts on vegetation includes physiological alteration, structural and ultrastructural changes and transcriptomic deregulation leading to plant growth inhibition (and yield loss). However, few studies have investigated the link between the dynamics of these events. Considering that one of the main gap for implementing the recent O3 flux-based critical levels (CL) concerns the quantification of plant capacity to neutralize a portion of the O₃ entering the leaf, a better understanding of cellular response dynamics to O₃ is required. In this context, young poplar (Populus tremula x alba, 717-1b4 INRAE clone) were exposed to 80 or 100 ppb O₃ in fully controlled conditions during 30 days. All analysis were performed on two leaves differing by their developmental stage (fully expanded vs in expansion). After a latency period driven by foliar development, net CO₂ assimilation and stomatal conductance decreased in response to O₃. Hypersensitive response-like appeared early during exposure, and showed sigmoidal-like dynamic, varying according to leaf age. Ontological evolution of HR-like lesion showed post-mortem evolution cellular material. Genes whose expression was highly correlated with HR-like were all involved in response to biotic stress, and can constitute a starting list of investigation to determine O₃ stress molecular markers. Accelerated Cell Senescence (ACS), followed through chlorophyll content, was later induced and showed monotonic dynamic. Senescence related genes were regulated early during O₃ exposure and dynamics of ACS-related microscopic changes were depending on O₃ treatments, leaf position and POD0. Hence, this work demonstrates the development of a complex syndrome of early reactions to O₃ stress in leaves, with di stinct dynamics and mechanisms of the HR-like and ACS processes. These processes could result from distinct spatial accumulation of O₃-induced ROS. Finally, this study also suggested that expression of genes involved in development during leaf expansion could confer higher tolerance to O₃ stress
Hilbert, Ghislaine. "Effets de la nutrition azotée et du stress hydrique sur la maturation et la composition en anthocyanes des baies de Vitis vinifera L. Au vignoble et en conditions contrôlées." Bordeaux 2, 2002. http://www.theses.fr/2002BOR20995.
We studied the effect of nitrogen nutrition and water deficit on the ripening of berries and on anthocyanins biosynthesis in the berry skins of Merlot vines (Vitis vinifera L. ) The experiments have been performed either on vines cultivated in vineyard (permanent grass cover allowed simultaneous variation of nitrogen and water supply) or under controlled environmental conditions (grapevine fruiting cuttings and two-year-old potted vines). Better berry ripening was observed under nitrogen or water limited supply. Our work showed interactions between nitrogen nutrition and water supply and the whole mineral nutrition of vines (especially P and K). Under reduced water and nitrogen nutrition, an increase of anthocyanins skin content was observed while a high nitrogen supply seemed to inhibit the anthocyanins synthesis. However, this latter effect was not observed under watering constraint. Our results suggest that water and nitrogen supply have a regulatory effect on the activity of the enzymes involved in the first steps of anthocyanins pathway. Different profiles of the anthocyanins species were obtained depending on the levels of nitrogen nutrition and watering supply. The synthesis of the malvidin derivatives was increased by a reduced water supply and was decreased by a limited nitrogen nutrition. The environmental factors seem to act differently on the esterification steps of anthocyanins biosynthesis. A regulation of the anthocyanins catabolism has to be considered too. In the vineyard, the level of anthocyanins biosynthesis depends essentially on the climatic conditions of the year (vintage), the "Terroir" effect and the cultural practices
Loisel, Ayala. "Compromis d'allocation des ressources et réchauffement climatique : vers une sénescence précoce des organismes aquatiques?" Thesis, Aix-Marseille, 2019. http://www.theses.fr/2019AIXM0392.
Temperature is a key ecological driver that regulates the biological functions of living organisms. This impact is more pronounced in ectothermic animals whose metabolism depends on environmental temperature and its variations. In these species, warming induces an acceleration in growth as well as a decrease in adult size. While these patterns are often observed over a generation, their evolution and the underlying mechanisms remain poorly understood thus far. In aquatic environments, temperature rise can decrease oxygen availability, increasing potentially the production of free radicals that are toxic to the body and accelerate aging process. In order to better understand adaptive abilities of fish facing climate change, this thesis explores the evolution of life history strategies through field approaches and experiments over several generations. Monitoring of growth, reproduction and oxidative balance showed for instance the importance of sex as well as ancestral and development temperatures on strategies
Larrigaudière, Christian. "Effets du traitement ionisant sur le métabolisme de l'acide 1 - aminocyclopropane - 1 - carboxylique chez des fruits climactériques : analyse de la réponse de stress et implications dans la maturation." Toulouse, INPT, 1989. http://www.theses.fr/1989INPT019A.
Jaimes, Miranda Fabiola. "La régulation transcriptionnelle dépendant de l'éthylène : Caractérisation fonctionnelle d'un cofacteur transcriptionnel du type MBF1 et d'un facteur de transcription de la famille des ERF chez la tomate." Toulouse, INPT, 2006. http://ethesis.inp-toulouse.fr/archive/00000242/.
Siala, Wafi. "Caractérisation moléculaire et fonctionnelle d'AtNRX1 et AtNRX2 deux protéines de type nucléorédoxines chez Arabidopsis thaliana." Perpignan, 2010. http://www.theses.fr/2010PERP1075.
Redox regulation plays a crucial role in the regulation of programs underlying plant cell division and defense mechanisms to environmental stresses. Key nuclear proteins (transcription factors, phosphatases, reductases, etc. . . ) are implicated in the control of cell division and stress response programs. Some of these proteins are known to be themselves under redox control through oxido-reduction of specific thioredoxins (TRX). While the presence of TRX in every cellular compartment has been shown, including the nucleus, their role in this latter compartment is poorly understood, especially in plants. The aim of this study is to get more insight into the functions of nuclear TRX by characterizing two Arabidopsis thaliana nucleoredoxins called AtNRX1 and AtNRX2
Herbette, Stéphane. "Etude des glutathions peroxydases (GPX) chez les végétaux supérieurs : rôle dans la réponse au stress." Clermont -Ferrand 2, 2004. http://www.theses.fr/2004CLF22494.
Henry, Christophe P. "Des perturbations à la restauration des écosystèmes aquatiques : expérimentation sur d'anciens chenaux du Rhône." Lyon 1, 1995. http://www.theses.fr/1995LYO10138.
Effa, Effa Branly Wilfried. "Effets de la symbiose endomycorhizienne sur la tolérance au stress hydrique chez le riz." Thesis, Montpellier, 2020. http://www.theses.fr/2020MONTG035.
Establishment of arbuscular mycorrhizal (AM) symbiosis in rice can promote its growth and tolerance to abiotic stress such as drought by improving its access to nutrient and water. The use of AM fungi (AMF) as bio-fertilizer therefore represent an interesting avenue for improving sustainability and resilience of rice cultivation in a context of land degradation and climate change. However, AM-symbiosis can in some context lead to detrimental effect on rice growth. Recent studies suggest that rice response to inoculation can, in addition to fungi and to environmental characteristics, be influenced by specific genetic determinants in rice. In this work, our objectives were to identify QTLs associated with plant response to AM-symbiosis when grown under irrigated and water deficit conditions. For this, plant growth conditions allowing root infection by the AM fungi Rhizophagus irregularis and compatible with high-throughput phenotyping were first determined. Secondly, a fully sequenced panel of 150 African rice (O. glaberrima) was phenotyped for shoot biomass across growth in inoculated and non-inoculated conditions using an imaged-based high-throughput phenotyping platform. Plants were grown in inoculated or non-inoculated conditions for four weeks under irrigation followed by a water deficit for three weeks. In our conditions, a negative effect of inoculation on shoot growth was observed at early vegetative growth under irrigated conditions (at 28 days after sowing; DAS) and after drought stress (at 46 DAS). Expression analyses of rice marker genes involved in different steps of rice/RI interaction, combined with visual observations of fungi structures in the root revealed that the plant established a pre-symbiotic dialogue with the fungi without establishing functional symbiosis. Association analyses between genotype and phenotype for shoot biomass under the inoculated treatment at 28 DAS identified a QTL containing a gene involved in nitrate transport. Our results open interesting ways regarding the role of nitrogen nutrition on AM-symbiosis establishment
Kaushal, Parvinder. "Analyse écophysiologique des effets de stress liés aux transplantations des arbres forestiers." Nancy 1, 1987. http://www.theses.fr/1987NAN10299.
Koch, Garance. "Effet du stress hydrique sur la croissance de la tomate : une étude multi-échelle : de la cellule à la plante entière pour une meilleure compréhension des interactions entre les différentes échelles." Thesis, Avignon, 2018. http://www.theses.fr/2018AVIG0347.
As for other multicellular organs, growth and development of leaves and fruits arecharacterized by cell division and expansion. Cell division and expansion are two maingrowth processes. Fleshy fruit pericarp cells also include successive endocycles that providean important increase in cell ploidy. There is a clear link between cell growth andendoreduplication. However, this link is still unclear from a functional point of view. Cellularprocesses interact during organ development and are related to plant water and carbon flows.The objective of this thesis is to give insights into the multi-scale control of leaves and fruitsgrowth in tomato (Solanum lycopersicum Mill.) and the plasticity of growth-related traits inresponse to soil water stresses.This study mainly focused on cherry tomato Solanum lycopersicum, cv. West Virginia 106(WVa 106). This genotype was cultivated in different conditions of watering regimes withautomated systems developed for this study. Soil water deficit response was studied atdifferent observation scales (tissue, organ, whole plant) and at different plant growth stagesthanks to protocols that were used until now on plants with determinate growth and simpleleaves that were modified for this study. Two transgenic genotypes modified on a cell cycleregulation gene were also cultivated to create variations on growth related traits for a betterunderstanding of their relationships. Multi-scale growth kinetics of source and sink organs(leaf and fruit) were also analyzed. Results have brought new elements about growth-relatedtraits coordination and have reinforced a few hypotheses already presented in scientificpapers. This work has supplied an original dataset on water stress effects on cellular processes(division, expansion, endoreduplication) related to leaf and fruit growth in tomato in thecontext of the plant as a whole. In perspectives, this dataset may allow to further develop anexisting model of fleshy fruit development which was first developed for fruits of plantsgrowing optimal condition. Genericity of this model will be tested on another organ, the leaf.This work also opens some tracks about how the model could be modified when growth islimited by water stress
Leschevin, Maïté. "Implication de la paroi végétale et plus particulièrement des enzymes de modification des pectines dans la tolérance au stress salin chez Arabidopsis." Thesis, Amiens, 2021. http://www.theses.fr/2021AMIE0027.
Soil salinization is a alarming situation encountered in several regions of the world where the pressure on water is becoming increasingly strong, especially due to climate change and the need to increase crop yields to face a global growing population. Excess of salt in soil affects plant physiological mechanism thus reducing plant production. A better knowledge of plant defense mechanism in response to salt stress is crucial to provide efficient strategies in crop yield. The plant cell wall is the first physical barrier between the plant cell compartment and the environment and plays an essential role in cell growth and development but also in response to various stresses, including salt stress. The cell wall is a highly complex and dynamic structure, mainly composed of polysaccharides (cellulose, hemicelluloses and pectins). Pectins can be methylesterified and acetylated, and their degree of methylesterification (DM) and acetylation (DA) can be modulated in muro by specific enzymes, pectin methylesterases (PMEs, EC 3.1.1.11) and acetylesterases (PAEs, EC 3.1. 1.6). Some parcelar data from the literature showed the role of pectins and their degree of methylesterification in tolerance to salt stress. The aim of this work was to provide new insights on the role of the cell wall in response to salt stress in the glycophyte Arabidopsis thaliana. Three distinct strategies were developed. Firstly, the natural variation between two common accessions of Arabidopsis thaliana (Wassilewskija, Ws and Columbia, Col-0) in response to salt stress has been characterized using an integrative approach establishing a correlation between physiological, biochemical, metabolomics and proteomics analyses. The results showed a better tolerance to salt stress associated with the genetic background Ws with an older developmental stage, a more efficient detoxification of reactive oxygen species and a higher content of xylan, mannan and lignin within the wall. Secondly, a reverse genetics approach has been developed to determine the contribution of two pectin remodeling enzymes, AtPME3 and AtPAE7 in salt tolerance. The results showed changes in the cell wall sugar composition as a reduction in homogalacturonan and an increase in arabinan in both atpme3 and atpae7 mutants after a long exposure to salt. Additionaly, salt stress induces a modulation of the PRE activities with an alteration of the pectin methylesterification pattern indicating a role of PME and PAE in cell wall integrity under salinity. Finally, a more informative approach combining cell wall metabolism, pectin remodeling enzymes, sodium ion detoxification pathway, and impact of calcium ions on cell wall integrity was carried out to characterize the role of the cell wall in the sodium hypersensitive mutant Atsos1. The SOS1 gene encodes a Na+/H+ antiporter which is involved in Na + exclusion. Preliminary results revealed that PME and PAE activities remained unchanged in atsos1 unlike the wild-type where the activites increased. That was associated with a reduction in pectin and mannan in atsos1, which was recovered by Ca2+ supply. All these data suggest the key role of atsos1 to maintain cell wall integrity under salt stress
Coucheney, Françoise. "La protéine Lo18, " small HSP " de la bactérie Oenococcus oeni impliquée dans la fermentation malolactique des vins : régulation, structure oligomérique et rôle de lipochaperon." Dijon, 2005. http://www.theses.fr/2005DIJOS022.
Within the framework of the study of stress adaptative response of the lactic acid bacterium Oenococcus oeni, we focused on the characterization of the small heat shock protein Lo18. Its synthesis is induced by multiple stresses and the protein is localized both in cytoplasm and associated to the membranes by weak bonds. The expression of its gene is down-regulated by the repressor CtsR of Bacillus subtilis. The protein forms oligomeric structures from 2 to 18 monomers depending on the buffer pH. Lo18 has a chaperon activity in vitro, but has also the property to interact with phospholipids and to stabilize the membranes above 40° C. This lipochaperon activity could be a new function of the smHsp in the maintenance of membrane integrity
Foucher, Philippe. "Etude d'indicateurs morphologiques pour la caractérisation de l'état hybride de végétaux par analyse d'images." Angers, 2003. http://www.theses.fr/2003ANGE0015.
The purpose of this work is to study how artificial vision, using shape analysis methods, can indicate a modificatifion of the state of the plant. To this end, morphological indicators, allowing a diagnosis in the case of plants when water deficits are fairly high, are researched. The study is realised on images of forsythias looked at from a horizontal plane. The artificial vision is composed of two steps. The first one consists of developing a method to classify pixels of the image in two groups : the plant and its background. Thus, a one hidden layer perceptron was tested with success. The second step concerns the identification of parameters indicating the whole morphological evolution of plants under water stress conditions. Several methods were developped and tested. Three methods allowed to define, in an absolute manner, a threshold above which the plant can be considered stressed. A physiological study of the water status of the plant was undertaken in a parallel way to validate the results obtained-by artificial vision
Genot, Baptiste. "Functional characterization of the stress-activated Arabidopsis MAP Kinase MPK3 using gain-of-function mutations." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLE010.
Plants can detect pathogens in their environment and adapt to survive it. The Stress Signalling group in IPS2 aims to decipher cellular mechanisms occurring after pathogens detection and to propose strategies to develop stress-resistant crops. Mitogen-Activated Protein Kinases (MAPKs) modules define key actors of signal transduction. MAPKs are indeed quickly activated in response to various stresses including pathogens-associated molecular patterns (PAMPs). Genetic approaches using loss-of-function mutants showed that MAPK modules regulate many aspects of plant adaptation to their environment.In our laboratory, we previously identified mutations which render MAPKs constitutively active (CA) in the plant model Arabidopsis thaliana.The main objective of my thesis was to clarify the specific roles of MAPKs activated by the PAMP flg22 using this new tool. For this, I created plants expressing CA MAPKs and characterized them in normal growth conditions or after pathogen infections. I mainly focused my project on the MAPK MPK3. I showed that plants expressing a CA version of MPK3 had an auto-immune phenotype characterized by a severe dwarfism, spontaneous cell death and accumulation of reactive oxygen species. Transcriptomic, metabolomic and genetic studies were performed to understand which pathways are regulated by this MAPK. This work demonstrates that MPK3 is a positive regulator of plant immunity, whose function depends on EDS1 (Enhanced Disease Susceptibility 1), a key regulator of pathogens responses, and partially depends on the phytohormone salicylic acid. I also created and characterized plants expressing constitutively active MPK6 and MPK11. In conclusion, CA mutations allowed us to reveal new specific roles for several stress-activated MAPKs. My preliminary results also suggest that plants expressing CA MAPK may have a better resistance to pathogens
Hem, Sonia. "Caractérisation par spectrométrie de masse de réponses précoces du phosphoprotéome d’Arabidopsis thaliana au stress en fer." Montpellier 2, 2008. http://www.theses.fr/2008MON20018.
In plants facing iron stress, the rapid induction of ferritins constitutes the best characterized molecular response. This process is under the control of phosphorylation/dephosphorylation events. This work aimed at characterizing the changes in the Arabidopsis phosphoproteome according to the iron environment in order to identify molecular events involved in these early steps. The approach was essentially performed directly at the peptide level. The general strategy was to optimize first the purification and fractionation of phosphopeptides from mixtures of model proteins showing an increasing complexity and then to apply the procedures to the biological samples of interest. The identification of phosphorylation sites was performed by MS/MS, either MALDI-TOF-TOF or nanoLC-ESI. Out of the methods elaborated, the combination of an initial enrichment by interaction with TiO2, of peptide fractionation by anion exchange and final purification using titanium dioxide, was proven to be the most effective for complex mixtures of phosphopeptides. This method was then used for peptides from the cytoplasmic side of the plasma membrane. It allowed the identification of pS and pT sites on mono- and multi-phosphorylated peptides from various membrane proteins of Arabidopsis. Among identified phosphoproteins, a main part corresponded to membrane transporters or kinases and one third of phosphorylation sites were not described to date. Different labelling approaches (metabolic, chemical, proteolytic) were then adapted to quantify the temporal pattern of these sites during the response to iron stress. The determination of changes in the phosphorylation levels was made by mass spectrometry after purification and fractionation of peptides as above
Ben, Nja Riheb. "Effet d’un stress salin sur la teneur en polymères pariétaux dans les feuilles de luzerne (Medicago sativacv Gabès) et sur la distribution dans les cellules de transfert des fines nervures." Limoges, 2014. http://aurore.unilim.fr/theses/nxfile/default/ad2f27f0-4319-4ebc-9039-58e310b33eb6/blobholder:0/2014LIMO4003.pdf.
Physiological and structural modifications in leaf of M. Sativa var. Gabès were compared in control and NaCl-treated plants. Biochemical analyses in wall fractions isolated from young and old leaves were associated with immuno detection of wall polymers in minor veins. The whole carbohydrate content is lower in young than in old control leaves. The reverse is induced by NaCl. The more expressed monosaccharides are galactose, galactic acid, glucose and arabinose in the pectin fractions, and xylose in the hemicellulose fractions. This content was modified according to leaf age and salin treament. In controls, the main difference was more glucuronic and galactic acids in old than in young leaves. Under NaCl, a higher content in arabinose and glucose occurred in young leaves, whereas more galactose, galactic acid, glucuronic acid and rhamnose in the old leaves, with a fucose increasing in the hemicellulose fractions. The immuno- identification of monosasaccharides by dot-blots has shown their variations in the wall fractions et their immunodetection in situ detailed their distribution in phloem transfer cells of minor veins. In controls, wall ingrowths are more abundant in the old than in the young leaves, and contain less JIM8, but more XyGs and RG. Under NaCl in old and young leaves, the augmentation of CCRCM1 and JIM8 argue for the possible role of these polymers in wall ingrowth network reinforcement
Nuttens, Andréïna. "Étude des effets de l'interaction entre polluants et ressources sur Myriophyllum spicatum grâce à une approche couplant écotoxicologie et écologie chimique." Thesis, Université de Lorraine, 2016. http://www.theses.fr/2016LORR0143/document.
Simultaneous contamination of aquatic ecosystems by pollutants and nutrients is a major problem whose effects on macrophytes are still unknown. The objective of this thesis was to study the effects of different pollutants, herbicides and trace metal elements (TME), in combination with varying resource availability (nitrogen, phosphorus, or carbon) on Myriophyllum spicatum, using parameters from chemical ecology and ecotoxicology. Tests showed contrasting effects of herbicides, but no effects of the TME. In all cases, resource modifications (nitrate, N:P ratio or sucrose) induced significant effects on the physiology and stoichiometry of the plant, which might alter its response to additional stress like pollutants. These results suggest that an imbalance of resources in the presence of pollutants may lead to unforeseen changes in the combined effects on macrophytes, and also highlight the need to add more informative parameters in tests to meet the challenges of multiple stress and improve environmental risk assessment
Gomez, Rodrigo Enrique. "Unravelling the contribution of lipids in plant autophagy : Identification and functional characterization of lipids implicated in the autophagic process in Arabidopsis." Thesis, Bordeaux, 2021. http://www.theses.fr/2021BORD0103.
Plants, being sessile organisms, are frequently confronted to a plethora of environmental stresses and harsh conditions. Enduring these conditions can lead to the accumulation of protein aggregates or organelles that become dysfunctional. To withstand these conditions, plants have evolved sophisticated adaptation mechanisms for the recycling of intracellular components. These mechanisms are essential for the metabolic transitions required for efficient nutrient use, as well as proper disposal of protein aggregates or damaged organelles. One of these mechanisms is autophagy, an intracellular degradation pathway that employs specialized double membrane vesicles that encapsulate cytosolic material and delivers it to the vacuole for degradation. Autophagy relies on the formation of these specialized vesicles, called autophagosomes (APs). APs are unique vesicles in the endomembrane system, first because they are made of a double lipid bilayer, and second because they do not but from a pre-existing compartment. AP biogenesis is a multistep process implicating a core machinery (ATG proteins) that mediate the de novo formation of an initial membrane; then, by the addition of lipids, this membrane expands into a cup-shaped structure with highly curved edges to engulf autophagic cargo. Upon completion, the rims of the structure seal and form a mature AP that traffics to the vacuole, where its outer membrane fuses with the tonoplast releasingthe inner membrane and cargo inside the vacuole. Thus, AP biogenesis relies on numerous membrane remodeling events, first to initiate the initial membrane, then to maintain the highly curved shape of the structure while ensuring its expansion, and finally to seal the mature structures and its subsequent fusion to the vacuole. Lipids, thanks to their physicochemical properties define important membrane features such as its, fluidity, curvature and electrostatics. Hence, evidence showing the crucial role of lipids in autophagy has emerged in the recent years. In plants however, little is known about the lipid composition of autophagic membranes and thus, about the functional contribution of lipids in plant autophagy. My PhD thesis consisted on identifying crucial lipids for plant autophagy with an aim to characterize their function in the process. By performing a lipid-related enzymes inhibitor screen in which we assayed the impact of inhibiting the synthesis of specific lipids on autophagy, we identified different lipid candidates important for plant autophagy. Notably, we identified the phosphatydil-inositol-4-phosphate (PI4P) as being critical for the formation of APs. In the absence of PI4P, AP formation is stalled at a very early stage resulting in a block in the process. Furthermore, we have obtained valuable insights to better understand the AP formation. In plants, particularly, our results suggest that the plasma membrane (PM) plays important roles in the formation of these structures. Taken together, our results confirmed that lipids are more than just building blocks constituting the autophagic membranes; rather, they seem to play distinct and specific roles in the pathway. Finally, this thesis highlights how lipids are key actors for the autophagic process and thus for plants adaptations to adverse and stressful environmental conditions