Climate change models predict an increase in frequency and amplitude of extreme weather events, including heat waves. To better predict how the composition and distribution of plant assemblages might respond to these changes in temperature, it is important to understand how species currently respond to these extremes. Photosynthetic thermal tolerance (T25)and photosynthetic recovery (RT25) were quantified in 27 species. We also studied the relationships between T25, RT25 and leaf mass per area (LMA). Leaf temperature was also monitored in the field. Leaves used in this study were collected from two distinct environments representing desert and montane plant assemblages. T25 and RT25 were measured using a chlorophyll fluorescence protocol incorporating sub-saturating light and short duration heat stress. Mean T25and LMA were significantly different between environments. Mean RT25 was not significantly different between environments. There was a positive relationship between T25 and LMA in both environments. The ability to recover from heat stress does not differ between two biomes that experience vastly different mean maximum temperatures during the summer months. LMA is a predictive leaf trait for thermal tolerance.

La température est un des principaux facteurs climatiques pilotant le développement des champignons pathogènes foliaires pendant les différentes étapes de leur cycle parasitaire. Puisque ces microorganismes se développent à la surface, puis à l’intérieur des feuilles, c’est la température de feuille (« body temperature » en écologie) qui pilote leur développement. En épidémiologie végétale, c’est toutefois la température d’air qui est utilisée pour caractériser l’effet de la température sur le développement des agents pathogènes foliaires. Or, la température de feuille peut différer significativement de la température d’air en fonction des conditions climatiques. La prise en compte de la température d’air pour étudier la dynamique des maladies foliaires ne peut donc s’affranchir de deux biais : la température mesurée n’est pas celle qui est réellement perçue par l’agent pathogène et l’hétérogénéité spatiale des températures au sein du peuplement n’est pas prise en compte. De plus, la relation entre la température et le développement des agents pathogènes est non linéaire, ce qui limite la gamme de validité autorisant l’utilisation des sommes de températures, pourtant largement employées en protestion des cultures. L’objectif général de cette thèse est de reconsidérer la prise en compte de la température pour l’étude du développement des champignons pathogènes foliaires.Le pathosystème blé-Mycosphaerella graminicola a été choisi en tant qu’objet d’étude. La stratégie adoptée pour atteindre les objectifs de la thèse combine deux approches complémentaires, l’expérimentation et la modélisation. Pour la première fois, la loi de réponse d’un agent pathogène foliaire à la température de feuille a été établie. Un dispositif expérimental innovant a permis d’établir la loi de réponse pour trois isolats sur une large gamme de températures foliaires, via la mesure en continu de la température de 191 feuilles (F et F) inoculées et l’utilisation d’un système de forçage thermique par lampe infrarouge. La loi de réponse de la période de latence de la septoriose à la température de feuille s’apparente au concept de courbe de performance thermique développé en écologie. Celle-ci étant non linéaire sur l’ensemble de la gamme de température étudiée, l’impact de l’amplitude de fluctuations de température de feuille a été caractérisé. Une amplitude élévée a conduit à plusieurs effets négatifs pour le développement de M. graminicola : l’augmentation de la durée du cycle de l’agent pathogène, la diminution de la surface sporulante des lésions et de la densité de pycnides. Les différences de cinétique de développement en fonction de l’amplitude des fluctuations ne sont que partiellement expliquées par l’effet Kaufmann (purement mathématiques), suggérant que M. graminicola atténue les conséquences négatives d’amplitudes de fluctuation plus élevées. Enfin, les simulations du développement de la septoriose réalisées à partir de données de températures foliaires diffèrent signicativement de celles réalisées à partir de températures d’air mesurées de façon standard par une station météorologique. Ces simulations ont également souligné le caractère déterminant du pas de temps considéré.Par le transfert de concepts d’écologie vers l’épidémiologie, cette thèse ouvre des pistes pour améliorer la prise en compte de la température dans les modèles épidémiologiques. Elle contribue au développement d’une meilleure compréhension des mécanismes par lesquels l’environnement affecte les microorganismes, point clé pour le développement de modèles mécanistes de réponses possibles au changement climatique / Temperature is a major force for the development of foliar fungal pathogens. Such organisms develop onto and into leaves during their growth cycle. Thus, leaf temperature is the temperature they actually perceive (“body temperature”). However, air temperature has always been used by plant pathologists to study the effect of temperature on the development of foliar fungal pathogens. Leaf temperature may significantly differ from the air temperature according to weather conditions. Therefore, considering the air temperature to study foliar pathogens can potentially cause two biases: the measured temperature is not the temperature such pathogens actually perceive and the spatial heterogeneity of leaf temperatures within the plant canopy is ignored. In addition, the relationship between temperature and the development of foliar pathogens is nonlinear. This challenges the immoderate use of degree-day sums in plant disease epidemiology. The main objective of this thesis is to reconsider the use of temperature for the study of the development of foliar fungal pathogens.The wheat-Mycosphaerella graminicola pathosystem was chosen as the model of study. The strategy to achieve the objectives of the thesis combines two complementary approaches: experimentation and modelling. For the first time, the impact of leaf temperature on the development of a leaf pathogen was characterized. An original experimental device allowed determining the response law for three isolates over a wide range of leaf temperature, using thermal infrared lamps and measuring continuously the temperature of 191 inoculated leaves (F1 and F2). The response law of M. graminicola latent period to leaf temperature is similar to the concept of thermal performance curve (TPC) developed in ecology. As this TPC is non-linear over the entire leaf temperature range investigated, the impact of the amplitude of leaf temperature fluctuations has been characterized. A high amplitude led to several negative effects on M. graminicola development: an increase in the duration of the pathogen cycle, a decrease in the final sporulating area in the pycnidium density. Differences in kinetics of development depending on the amplitude of the fluctuations were only partially explained by the Kaufmann effect (purely mathematical), suggesting that M. graminicola mitigates the negative consequences of higher amplitudes of temperatures fluctuation. Finally, simulations of the development of M. graminicola performed using leaf temperature data differed significantly from those performed using air temperatures measured in a standard way, by a weather station. Simulations also underlined the importance of the time step considered. By transferring concepts from ecology to epidemiology, this thesis provided guidelines to better take into account temperature in epidemiological models. It helped to develop a better understanding of the mechanisms by which the environment affects micoorganisms, the cornerstone for the development of mechanistic models of possible responses to climate change.

Made available in DSpace on 2017-07-10T17:36:55Z (GMT). No. of bitstreams: 1 2014_Diss_Paulo_Ricardo_Lima.pdf: 1308778 bytes, checksum: fcc1fc80a1ef2f3cfecb3a398ecc76bb (MD5) Previous issue date: 2014-02-21 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The knowledge of Morphophysiological mechanisms that allow a plant tolerate water stress conditions constitutes important tool for analyzing the quality of seedlings, so it the work aimed to quantify the effects of water management in the period of rustification in seedlings of Handroanthus impetiginosus (Mart. ex DC.) Mattos and Gallesia integrifolia (Spreng.) Harms by means of foliar thermometry and parameters morphometric of quality and additionally analyze the performance of seedlings after the rustification, in soil sandy and loamy soil. The experiment was conducted in a protected ambient at the State University of West Paraná, campus Marechal Cândido Rondon - PR. The treatments were comprised of four hydric regimes: daily irrigation (control), every two, three and four days in 60 seedlings per treatment for four weeks. The mensurations involved the measurement of the leaf temperature (TF), the increments in height, the stem diameter, in the mass dry of root , in the mass dry of shoot and leaf area. The mensurations of TF occurred at the end of each irrigation management cycle and for the other variables were held measurements at the beginning and end of rustification. After the impositions of hydric managements, the seedlings were taken to pots containing sandy soil and clay soil to check the influence of different hydric management as well as soil type in the seedling survival. The analysis between the control treatment and irrigation every two days resulted in significant differences (P> 0,05) merely for leaf area, whereas in and both species studied presented decreased of leaf area with the increase of hydric restriction. Seedlings of H. impetiginosus with of irrigation cycles every three days, showed a reduction in the rate of growth in diameter of 29%, of 58% to increment the dry mass of shoots and 32% for leaf area compared to the management control. Seedlings of G. integrifolia irrigated every three days showed no significant differences (P> 0,05) compared with irrigated daily. The irrigation management every four days in seedlings of H. impetiginosus enabled higher speed of growth of the root system and reduced aerial growth, resulting in warming the leaf, whereas the irrigation management every four days in seedlings of G. integrifolia presented reduction in the rate of growth of the shoot and not presented difference (P> 0,05) in the root system growth and also resulted in leaf warming. The use of the infrared thermometry allows benchmarking the leaf temperature during rustification of seedlings of H. impetiginosus and G. integrifolia. Was no influence of soils in the seedling survival of H. impetiginosus and G. integrifolia, and symptoms of hydric deficit always if manifested first in clay soil, mainly in seedlings not adapted to hydric stress. In both species, the symptoms of hydric deficit presented by the seedlings of different management hydrics showed that seedlings submitted to the irrigation regimes every three and four days, were attenuating slowly the symptoms of hydric deficit compared with others hydrics management / O conhecimento dos mecanismos morfofisiológicos que permitem a uma planta tolerar as condições de estresse hídrico constitui importante ferramenta para analisar a qualidade de mudas. O trabalho objetivou quantificar os efeitos do manejo hídrico no período de rustificação em mudas de Handroanthus impetiginosus (Mart. ex DC.) Mattos e Gallesia integrifolia (Spreng.) Harms por meio da termometria foliar e por parâmetros morfométricos de qualidade e adicionalmente analisar o desempenho das mudas após a rustificação, em solo arenoso e argiloso. Conduziu-se o experimento em ambiente protegido na Universidade Estadual do Oeste do Paraná, campus de Marechal Cândido Rondon PR. Os tratamentos foram compostos por quatro regimes hídricos: irrigação diária (tratamento controle), a cada dois, três e a cada quatro dias, em 60 mudas por tratamento, durante quatro semanas. As mensurações envolveram a medição da temperatura foliar (TF), os incrementos na altura, no diâmetro de colo, na massa seca radicular, na massa seca da parte aérea e na área foliar. As mensurações da TF ocorreram ao final do ciclo de cada manejo de irrigação e para as demais variáveis realizaram-se as mensurações no início e final da rustificação. Após a imposição dos manejos hídricos, as mudas foram levadas para vasos contendo solo arenoso e argiloso, para verificar se há influencia dos diferentes manejos hídricos, bem como do tipo do solo na sobrevivência da muda. A análise entre os tratamentos controle e irrigação a cada dois dias resultou em diferenças (P> 0,05) apenas para área foliar, sendo que ambas as espécies estudadas apresentaram redução da área foliar com o aumento da restrição hídrica. Mudas de H. impetiginosus com ciclos de irrigação a cada três dias, apresentou redução na taxa de crescimento em diâmetro de 29%, de 58% para incremento da massa seca da parte aérea e de 32% para área foliar em comparação ao manejo controle. Mudas de G. integrifolia irrigadas a cada três dias não apresentaram diferenças significativas (P> 0,05) em relação às irrigadas diariamente. O manejo de irrigação a cada quatro dias em mudas de H. impetiginosus possibilitou maior velocidade de crescimento do sistema radicular e reduziu o crescimento aéreo, resultando no aquecimento foliar, enquanto que o manejo de irrigação a cada quatro dias em mudas de G. integrifolia apresentou redução na velocidade de crescimento da parte aérea e não apresentou diferença (P> 0,05) no crescimento do sistema radicular e também resultou no aquecimento foliar. O uso da termometria infravermelho permite aferir a temperatura foliar na rustificação de mudas de H. impetiginosus e G. integrifolia. Houve influência dos solos na sobrevivência das mudas de H. impetiginosus e G. integrifolia, e os sintomas de déficit hídrico sempre se manifestaram primeiro no solo argiloso, principalmente nas mudas não adaptadas ao estresse hídrico. Em ambas as espécies, as diferenças dos sintomas de déficit hídrico apresentadas pelas mudas dos diferentes manejos hídricos mostraram que mudas submetidas ao regime de irrigação a cada três e quatro dias, foram atenuando lentamente os sintomas de déficit hídrico em comparação aos demais manejos hídricos

Identifying reliable screening tools and characterizing tolerant germplasm sources is essential for developing wheat (Triticum aestivum L.) varieties suited for the hot areas of the world. Our objective was to evaluate heat tolerance of promising wild tetraploid wheat (Triticum turgidum L.) accessions that could be used as sources of heat tolerance in common- and durum-wheat (Triticum durum) breeding programs. We screened 109 wild tetraploid wheat accessions collected by the International Center for Agriculture Research in the Dry Areas (ICARDA) from the hottest wheat growing areas in Africa and Asia, as well as, two common wheat checks for their response to heat stress by measuring damage to the thylakoid membranes, flag leaf temperature depression (FLTD), and spike temperature depression (STD) during exposure to heat stress for 16 beginning at anthesis. Measurements were taken on the day of anthesis then 4, 8, 12, and 16 days post anthesis (DPA) under controlled optimum and heat-stress conditions. Individual kernel weight (IKW) and heat susceptibility index (HSI) measurements were also obtained. Prolonged exposure to heat stress was associated with increased damage to thylakoid membranes, as indicated by the high ratio of constant fluorescence (O) to peak variable fluorescence (P). A positive and significant correlation was found between O/P ratio and both FLTD and STD under heat-stress conditions. A negative and significant correlation was found between FLTD and HSI and between STD and HSI based on the second and third measurements (4 and 8 DPA). Correlations obtained after the third measurement were not significant because heat-stress accelerated maturity and senescence. For a pedigree-based mapping strategy a family approach was then developed by crossing and back-crossing heat-tolerant and heat-susceptible germplasm. A set of 800 lines resulting from the pedigree-based family approach was phenotyped using FLTD, chlorophyll content and yield and its components under heat stress. Genotyping of these lines was accomplished using simple sequence repeat (SSRs) markers. Some QTLs associated with heat stress tolerance were identified. This study identified potential heat-tolerant wild tetraploid wheat germplasm and QTL conditioning heat tolerance that can be incorporated into wheat breeding programs to improve cultivated common and durum wheat.

Les challenges posés par les missions d’exploration du système solaire sont très différents de ceux de la Station Spatiale Internationale, puisque les distances sont beaucoup plus importantes, limitant la possibilité de ravitaillements réguliers. Les systèmes support-vie basés sur des plantes supérieures et des micro-organismes, comme le projet de l’Agence Spatiale Européenne (ESA) MELiSSA (Micro Ecological Life Support System Alternative) permettront aux équipages d’être autonomes en termes de production de nourriture, revitalisation de l’air et de recyclage d’eau, tout en fermant les cycles de l’eau, de l’oxygène, de l’azote et du carbone, pendant les missions longue durée, et deviendront donc essentiels.La croissance et le développement des plantes et autres organismes biologiques sont fortement influencés par les conditions environnementales (par exemple la gravité, la pression, la température, l’humidité relative, les pressions partielles en O2 et CO2). Pour prédire la croissance des plantes dans ces conditions non-standard, il est crucial de développer des modèles de croissance mécanistiques, permettant une étude multi-échelle des différents phénomènes, ainsi que d’acquérir une compréhension approfondie de tous les processus impliqués dans le développement des plantes en environnement de gravité réduite et d’identifier les lacunes de connaissance.En particulier, les échanges gazeux à la surface de la feuille sont altérés en gravité réduite, ce qui pourrait diminuer la croissance des plantes dans l’espace. Ainsi, nous avons étudié les relations complexes entre convection forcée, niveau de gravité et production de biomasse et avons trouvé que l’inclusion de la gravité comme paramètre dans les modèles d’échanges gazeux des plantes nécessite une description précise des transferts de matière et d’énergie dans la couche limite. Nous avons ajouté un bilan d’énergie au bilan de masse du modèle de croissance de plante déjà existant et cela a ajouté des variations temporelles sur la température de surface des feuilles.Cette variable peut être mesurée à l’aide de caméras infra-rouges et nous avons réalisé une expérience en vol parabolique et cela nous a permis de valider des modèles de transferts gazeux locaux en 0g et 2g, sans ventilation.Enfin, le transport de sève, la croissance racinaire et la sénescence des feuilles doivent être étudiés en conditions de gravité réduite. Cela permettrait de lier notre modèle d’échanges gazeux à la morphologie des plantes et aux allocations de ressources dans une plante et ainsi arriver à un modèle mécanistique complet de la croissance des plantes en environnement de gravité réduite. / Challenges triggered by human space exploration of the solar system are different from those of the International Space Station because distances and time frames are of a different scale, preventing frequent resupplies. Bioregenerative life-support systems based on higher plants and microorganisms, such as the ESA Micro-Ecological Life Support System Alternative (MELiSSA) project will enable crews to be autonomous in food production, air revitalization, and water recycling, while closing cycles for water, oxygen, nitrogen, and carbon, during long-duration missions and will thus become necessary.The growth and development of higher plants and other biological organisms are strongly influenced by environmental conditions (e.g. gravity, pressure, temperature, relative humidity, partial pressure of O2 or CO2). To predict plant growth in these non-standard conditions, it is crucial to develop mechanistic models of plant growth, enabling multi-scale study of different phenomena, as well as gaining thorough understanding on all processes involved in plant development in low gravity environment and identifying knowledge gaps.Especially gas exchanges at the leaf surface are altered in reduced gravity, which could reduce plant growth in space. Thus, we studied the intricate relationships between forced convection, gravity levels and biomass production and found that the inclusion of gravity as a parameter in plant gas exchanges models requires accurate mass and heat transfer descriptions in the boundary layer. We introduced an energy coupling to the already existing mass balance model of plant growth and this introduced time-dependent variations of the leaf surface temperature.This variable can be measured using infra-red cameras and we implemented a parabolic flight experiment, which enabled us to validate local gas transfer models in 0g and 2g without ventilation.Finally, sap transport needs to be studied in reduced gravity environments, along with root absorption and leaf senescence. This would enable to link our gas exchanges model to plant morphology and resources allocations, and achieve a complete mechanistic model of plant growth in low gravity environments.