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Delamare, Jeremy. "Analyses de deux stratégies d’acclimatation à un stress thermique intense reposant sur une thermo-sensibilisation ou une sensibilisation médiée par des bactéries PGPR chez le colza et la caméline". Electronic Thesis or Diss., Normandie, 2023. http://www.theses.fr/2023NORMC243.
Pełny tekst źródłaThe on-going climate changes that we are facing are characterized in particular by modifications of temperature profiles in terms of intensity, duration and repetition of heat waves. These heat waves occur during the reproductive stages of the crops, which are also the most critical for seed yield elaboration and grain quality in crops. Oleaginous species such as rapeseed and camelina, are species particularly impacted by heat stress that cause yield penalties and a lower seed quality. Therefore, to cope with heat stress, it has become necessary to identify new acclimation levers that differ avec genetic and agronomic levers, such as strategies based on plants acclimation. Thermopriming which consist in priming the plants in a way to help them respond more rapidly, effectively, intensively and/or sensitively to heat by a prior exposure of a stress of the same nature could allow the plants to acclimate and develop appropriate response mechanisms. The plant inoculation with Plant Growth Promoting Rhizobacteria (PGPR)-type bacteria is also an acclimation lever increasingly studied, that limit the impacts of abiotic stress such as heat stress. However, although these two types of acclimation levers are mainly studied to limit stress impact on aboveground development and yield, few studies have observed their effects on root morphology and functions such as root exudation. In this thesis we analysed in rapeseed and camelina (i) the effects of a gradual increase in temperature prior a heat stress on yield and grain quality and on root morphology and exudation and (ii) the effects of inoculating two Pseudomonas with PGPR activities in order to limit the impact of heat stress on yield and grain quality. Moreover, in order to understand the impact of heat stress and PGPR inoculation (combined or not) on the plant and associated rhizosphere, the effects of these treatments were studied on root exudation, carbon (C) allocation in the soil-plant system, root morphological traits and soil microbial communities. Our results showed that rapeseed and camelina have contrasting strategies in terms of response to heat stress. Indeed, camelina seems to respond to the stress by increasing its investment to the roots thus improving the quality of exudation and stimulating the activity of microbial communities, unlike rapeseed, which seems to undergo heat stress. In addition, these two species respond differently to the two acclimation strategies applied. In rapeseed, thermopriming reduced C exudation and maintained yield and grain quality, whereas it had a more negative impact on exudation and root morphology in camelina. PGPR inoculation is an acclimation strategy that tends to limit the effects of heat stress on yield and grain quality in rapeseed. However, PGPRs act as an additional sink in rapeseed, impacting its development, exudation and the activity and composition of microbial communities in the rhizosphere. By contrast, camelina is slightly affected by the addition of PGPRs and seems to control the plant/bacteria interactions rather than be affected by them. In short, beneficial effects on plants of these acclimation levers have been evidenced. In addition, it could be interesting to integrate the effects of varietal selection on plant response strategies to stress, and in particular the variability of root functions and interactions with the rhizosphere, in the light of the varietal selection differentially undergone by rapeseed and camelina
Guyonnet, Julien. "Effet de la stratégie de gestion des ressources des plantes sur l’investissement dans l’exsudation racinaire, et les conséquences sur les communautés bactériennes". Thesis, Lyon, 2017. http://www.theses.fr/2017LYSE1008.
Pełny tekst źródłaRoot exudation is known to influence microbial communities functioning, in particular those involve in nitrogen cycle. (Haichar et al, 2012). It’s linked to plant physiology, which can be evaluated with functional traits, allowing a plant distribution in function of their performance in their environment. Thus, we can distinguish competitive species, with higher photosynthetic capacity and rapid rates of N acquisition, conservative species with the opposite characteristics (Aerts & Chapin, 1999) and intermediate plants, with intermediate characteristics.The objective of this work is to determinate the influence of nutrient management strategiy of 6 poaceae, along a strategies gradient from conservative strategy (Sesleria caerulea and Festuca paniculata), intermediate (Antoxanthum odoratum and Bromus erectus) to competitive strategy (Dactylis glomerata and Trisetum flavescens), on diversity and functioning of total and denitrifying communities.I) Firstly, we studied the link between the plant nutrient management strategy and the root exudates quantity in the root adhering soil (RAS). Then, we determined the influence of the rate of root exudation on potential microbial activities (respiration and denitrification), and with a DNA-SIP (Stable Isotope Probing) approach coupled to high-throughput sequencing, the influence of root exudation on the bacterial structure and diversity of communities colonizing the RAS and the root system. II) Secondly, we studied the link between the plant nutrient management strategy and the nature of molecules exuded in RAS and present in root extracts by analyzing primary metabolites profile to Festuca paniculata, Bromus erectus and Dactylis glomerata, respectively a conservative, an intermediate and a competitive plant. Then, we determined the influence of primary metabolites profile of each plant on semi-real denitrification of communities colonizing RAS of plants. III) Finally, an mRNA-SIP approach is in progress to determine the influence of exuded metabolites on active bacterial communities functioning and the expression of genes involved in denitrification process in RAS and root system. Our results show an influence of the nutrient management strategy on the rate of carbon exudation, the competitive plants exuding more than conservatives ones
Chanteloup, Pierre. "Patrons d'organisation des traits aériens et racinaires en prairies humides : liens avec la production primaire (quantité et qualité)". Phd thesis, Université Rennes 1, 2013. http://tel.archives-ouvertes.fr/tel-00861449.
Pełny tekst źródłaRomillac, Nicolas. "Effets de l’introduction du pois dans une succession de cultures sur certaines communautés végétales et bactériennes et leurs fonctions écosystémiques associées". Thesis, Université de Lorraine, 2015. http://www.theses.fr/2015LORR0266/document.
Pełny tekst źródłaCrops species modify resources availability and perturbation regimes perceived by the communities of organisms residing in the agroecosystems and, as a consequence, can lead to alteration of ecosystem functions useful to crop production, such as nitrogen and sulfur mineralization or crop-weeds competition, realized by weeds or microorganisms. Our objective was to study the effect of a legume, pea, when introduced in a crop succession, on weed communities and microbial communities involved in protein decomposition and sulfate ester mineralization, which are the main forms of N and S, respectively, in agricultural soils. To do so, we performed experiments in controlled conditions used data from a 5-years field experiment. In controlled conditions, we showed that pea during its development modify through its root functional traits several enzymatic activities involved in N decomposition/mineralization. However, in the field experiment, climatic factors were the main drivers of the microbial communities involved in N and S decomposition/mineralization. Moreover, pea selected weed communities that were functionally different from weed communities growing in other crops such as oilseed rape. However, this effect did not persist under the following crop. As a conclusion, our results suggest that pea modifications of microbial communities are weak compared to other factors such as climatic factors. However, pea effects on weed communities are strong but short lived. Those results highlight the complementarity of microcosm and field experiments, and the necessity of long term field experiments to take into account climate variability
Ghestem, Murielle. "Quelles propriétés racinaires et quelles espèces-outils pour la stabilisation des points chauds de dégradation en Chine du Sud ?" Phd thesis, AgroParisTech, 2012. http://pastel.archives-ouvertes.fr/pastel-00855792.
Pełny tekst źródłaDemenois, Julien. "Quelle influence des symbioses mycorhiziennes et des traits racinaires sur l'érosion des sols tropicaux ? Application à la restauration écologique des écosystèmes forestiers dégradés de Nouvelle-Calédonie sur Ferralsols développés sur substrats ultramafiques". Thesis, Paris, AgroParisTech, 2017. http://www.theses.fr/2017AGPT0011.
Pełny tekst źródłaTropical forest ecosystems cover nearly half of the world's forest area. These ecosystems provide basic services for the well-being of our societies (e.g. regulation of material flows, soil preservation) are particularly affected (loss and degradation of forests) by global changes. New Caledonia, and its ultramafic substrates, is no exception to this trend. Mining and fires are responsible for forest regression, fragmentation, degradation and soil erosion. The archipelago is ranked among the hotspots of global biodiversity and the ecological restoration of these ecosystems is a major challenge. The objective of this thesis is to contribute to the ecological restoration of the forests of New Caledonia in order to limit the erosion of soils on ultramafic substrates and is part of the disciplinary field of the ecology of restoration. The scientific objective is to study the influence of mycorrhizal symbiosis and root traits on the erosion of Ferralsols developed on ultramafic substrates through a multi-scale approach. In the first part, we highlight the floristic and structural characteristics of plant communities on ultramafic substrates. These suggest an increased expression of the root traits of dominant species in monodominant forests. The central place of fire and cyclones in the dynamics of plant succession is also emphasized, as well as mycorrhizal symbioses in maintaining the monodominance of Nothofagus aequilateralis. In the second part, our work suggests the existence of a biotic threshold between degraded ligno-herbaceous maquis and ligno-herbaceous maquis. Repeated fires would be the main cause of crossing this threshold. The increase in plant biomass would be the key factor contributing to the stability of the aggregates between these two stages. Thus, fire protection combined with the promotion of plant successions through the use of potentially facilitating species such as Costularia arundinacea could be an efficient strategy for limiting erosion of Ferralsols. In addition, the influence of plant (e.g. floristic composition) and fungal communities (e.g. biomass) on the stability of aggregates is clearly highlighted. The third part aims to evaluate the ability of plant species, combined with mycorrhizal fungi, to increase the stability of aggregates, but also to identify root traits and mycorrhizal associations contributing to this increase. In this section, we demonstrate that the combination of high values for “Root Mass Density - Root Length Density – percentage of fine roots” is effective in increasing aggregate stability. Moreover, the efficacy of this combination of root traits is enhanced by mycorrhizal symbiosis. Thus, of the three plant species evaluated, Costularia arundinacea would be the most effective tool species for increasing the stability of aggregates. This work allowed us to highlight the influence of root traits and mycorrhizal symbiosis on the stability of soil aggregates on Ferralsols on ultramafic substrates, at the scale of plant communities or at the level of plant species. To our knowledge, these results are the first to be acquired on this type of soil. These results make it possible to formulate proposals for the ecological restoration of forest ecosystems in New Caledonia in order to limit soil erosion on ultramafic substrates, but also to sketch new avenues of research
Zwicke, Marine. "Impacts d'une canicule sécheresse sur le fonctionnement et la structure des communautés végétales de l'écosystème prairial". Phd thesis, Université Blaise Pascal - Clermont-Ferrand II, 2013. http://tel.archives-ouvertes.fr/tel-01020033.
Pełny tekst źródłaRossi, Lorenzo Matteo Walter. "Embankment as a carbon sink : a study on carbon sequestration pathways and mechanisms in topsoil and exposed subsoil". Thesis, Montpellier, 2019. http://www.theses.fr/2019MONTG083.
Pełny tekst źródłaCarbon (C) sequestration is receiving increasing scientific and political attention in a framework of greenhouse gasses mitigation. However, geotechnical soils have been neglected for their C sequestration potential, with the global attention focusing on agricultural and natural soils. In the present thesis project we aim to assess the potential of geotechnical embankments as C sink, and, through the study of plant species and soils showing contrasting features, shed light on SOC sequestration mechanisms and the role of the different actor involved. We aim not only to quantify the C gained and lost in soil, but even its origin (fresh new C input or old preexistent C) and how it is partitioned in different C pools characterized by different C stability (quality of stored C). First, we evaluated the C storage in different pools under soil sowed with 12 different herbaceous species in a 10 months experiment. Assessing different root traits allowed understanding the influence of root economic spectrum on C storage. We showed how traits linked to high labile C are linked to a higher C increase in the stable SILT+CLAY pool (<20µm). Root traits related to a low input of recalcitrant, instead, favor accumulation in the unstable POM fraction. Thanks to a 183 days stable isotope labelling experiment (CO2 constantly enriched with 13C) we were able to study the C dynamics in different C pools under two species (L. perenne and M. sativa) sowed on two soil (topsoil, 0-30cm depth and subsoil brought to the surface, 110-140 cm depth) showing contrasting characteristics. We evidenced the great interest of bridging C origin and C pools when studying soil C fates, allowing unveiling processes those more traditional methods would hide. New C and old C showed synergetic covariation, with lower old C losses associated to higher new C inputs. This is in good accordance with the Preferential Substrate Utilization hypothesis (Cheng and Kuzyakov, 2005). The Preferential Substrate Utilization hypothesis was also validated with the study of priming effect and soil respiration, that showed higher plant derived C in respired CO2 when plant C input were high, while increasing old C mineralization when plant C input were low, i.e. in subsoil. We observed significant plant derived new C input in the SILT+CLAY fraction (<20µm, highly stable) supporting evidence of the in vivo entombing effect in the soil Microbial Carbon Pump hypothesis (Liang et al., 2017). The species effect mainly occurred on new C input, but it was overpowered by the soil effect, with lower C storage in low quality soil (low nitrogen and microbial biomass and activity). In general, microbiological conditions were the main driver for new C accumulation and old C loss, and helped to explain why no effect of soil C saturation – a central theory in recent studies on C sequestration - was find in the protected carbon. Such fundamental understanding of plant-soil interactions help us to better optimize soil and vegetation management for road embankment revegetation