Literatura académica sobre el tema "Stress agricolo"

Malgré l’amélioration qu’ils apportent à la production agricole, les périmètres irrigués génèrent des risques sociaux, économiques et écologiques importants, qui questionnent leurs impacts effectifs sur la vulnérabilité sociale, économique, environnementale et alimentaire des populations bénéficiaires. La réflexion sur la construction de la vulnérabilité mobilisée dans le cadre de cet article cherche à analyser, dans une perspective socio-historico-économique, comment les processus, les changements et les perturbations dans le temps et dans l’espace peuvent expliquer les mécanismes à la source des vulnérabilités actuelles des ménages installés autour du système irrigué de la cuvette de Guédé au Sénégal. Les résultats mettent en évidence une vulnérabilité différentielle des types de ménages à plusieurs facteurs de stress. Cette vulnérabilité est fonction de la faiblesse des surfaces cultivées et des rendements, des coûts de production élevés ou des difficultés d’accès à des activités extra-agricoles, mais aussi de la période et du lieu d’installation des ménages, qui définissent partiellement leur dotation en ressources, et ainsi leur capacité à faire face à des conditions changeantes. Pour fournir une réflexion pluridisciplinaire, systémique et nuancée sur la vulnérabilité des ménages agricoles du système irrigué de Guédé, il est important de comprendre les mécanismes qui fondent la construction et l’évolution de la vulnérabilité et de voir comment leurs interactions dynamiques peuvent réduire ou renforcer les vulnérabilités existantes ou créer de nouvelles vulnérabilités.

In the past few decades, size and weight of agricultural machinery have increased significantly, and as a consequence, the severity and depth to which the stress is transmitted into agricultural soil have increased. The objective of experimental determinations was to study the influence of some factors characteristics to compaction: tire inflation pressure, wheel load and contact pressure on the contact area between tire and soil, as well as 2D and 3D mapping of pressure distribution in the footprint. The front tire of the U445 Romanian agricultural tractor was tested at five tire inflation pressures: 100, 150, 200, 250 and 300 kPa, obtaining contact areas between 0.0252 – 0.0349 m2 and contact pressures between 98 - 136 kPa.

AbstractThe ecological effects of disrupted flooding are known to be pernicious for the occurring riparian fauna. As flooding disturbance is argued to structure species assemblages, behavioural aspects may be affected just as well. Generally, eurytopic inhabitants possess a well-developed dispersal ability allowing frequent recolonization, whereas specialized stenotopic species are expected to be adapted to these stress regimes. This study aims at determining whether flooding induces different behavioural responses in two congeneric wolf spider species. Variation in flood-avoiding behaviour was evaluated by means of individual tests performed under different ambient conditions. We considered sheltering behaviour preceding flooding, a direct flight reflex induced by the flood event, an escape reaction away from the rising water and submersion tolerance. Our findings indicated clear flood-avoiding behaviour for both species, yet a higher degree of plasticity in individual behaviour for a riparian wolf spider (Pardosa agricola) in contrast to a generalist species (P. amentata). Nonetheless the former species systematically reacted under different ambient conditions, a generalist shifts responses, displaying a higher degree of between-individual variation. Submersion tolerance was equivalent, emphasizing similar morphological characteristics. We argue habitat specialization and/or experience with local conditions to influence behavioural responses in order to optimize long-term persistence under flood stress. Future studies of behavioural variation should consider temporal variation in species condition, thus employing distinct populations thriving under different local stress regimes.

Les émissions d’ammoniac sont à 95 % d’origine agricole, dont 80 % proviennent de l’élevage. L’ammoniac est un gaz irritant pouvant être incriminé dans l’apparition de certaines maladies (asthme, bronchites chroniques) chez les éleveurs et chez les animaux et également dans la diminution des performances zootechniques. Les retours de l’ammoniac à la biosphère se font sous forme sèche ou humide, soit à proximité du lieu d’émission, soit après avoir parcouru de longues distances notamment pour l’ammonium dont le temps de résidence dans l’air est plus long que celui de l’ammoniac. Ces retombées ont diverses conséquences : (1) sur les plantes, cela entraîne un déséquilibre dans leur alimentation et augmente leur fragilité vis-à-vis d’autres facteurs secondaires de stress ; (2) suivant les caractéristiques physico-chimiques des sols et des eaux cela débouchera, soit sur un enrichissement en azote, soit sur une acidification avec disparition de la faune et de la flore dans les cas extrêmes.

Principles of allostasis and allostatic load have been widely applied in human research to assess the impacts of chronic stress on physiological dysregulation. Over the last few decades, researchers have also applied these concepts to non-human animals. However, there is a lack of uniformity in how the concept of allostasis is described and assessed in animals. The objectives of this review were to: 1) describe the extent to which the concepts of allostasis and allostatic load are applied theoretically to animals, with a focus on which taxa and species are represented; 2) identify when direct assessments of allostasis or allostatic load are made, which species and contexts are represented, what biomarkers are used, and if an allostatic load index was constructed; and 3) detect gaps in the literature and identify areas for future research. A search was conducted using CABI, PubMed, Agricola, and BIOSIS databases, in addition to a complementary hand-search of 14 peer-reviewed journals. Search results were screened, and articles that included non-human animals, as well as the terms “allostasis” or “allostatic” in the full text, were included. A total of 572 articles met the inclusion criteria (108 reviews and 464 peer-reviewed original research). Species were represented across all taxa. A subset of 63 publications made direct assessments of allostatic load. Glucocorticoids were the most commonly used biomarker, and were the only biomarker measured in 25 publications. Only six of 63 publications (9.5%) constructed an allostatic load index, which is the preferred methodology in human research. Although concepts of allostasis and allostatic load are being applied broadly across animal species, most publications use single biomarkers that are more likely indicative of short-term rather than chronic stress. Researchers are encouraged to adopt methodologies used in human research, including the construction of species-specific allostatic load indexes.

Despite their crucial importance, limited information exists about how livestock are affected by climate change in Nigeria. Changing climatic patterns are manifested through occurrences like abrupt temperature increase, dwindling rainfall pattern, rise in spells of drought and flood. These conditions exert different effects across the geographical landscape of the country, which can broadly be classed as Semiarid, Sahel and Derived Savannah, respectively as well as Forest and Montane. Livestock provide humans with the full complement of amino acids, which are the only known natural suppliers of Vitamin B12 and equally supply iron, calcium, iodine and zinc. In addition, livestock accounts for 40% of Agricultural Gross Domestic Product and significantly contributes to enhancing rural livelihood. Stress conditions are induced in livestock by harsh weather conditions that reduce the feed available to them as well as impede growth rate and reproduction efficiency and disease incidence which may eventually result in death. In the light of the livestock benefits to humanity, it is necessary to devise means of making their climate resilient. Some of the proven strategies include animal genetic improvement for stress tolerance, growing disease resistant, early maturing and drought tolerant crops, selecting for and rearing climate tolerant animal species and breeds. Malgré leur importance cruciale, il existe peu d'informations sur la manière dont le bétail est affecté par le changement climatique au Nigéria. Le changement des modèles climatiques se manifeste par des événements tels que l'augmentation brutale de la température, la diminution des précipitations, l'augmentation des périodes de sécheresse et d'inondation. Ces conditions exercent des effets différents sur le paysage géographique du pays, qui peuvent être globalement classés comme semi-aride, sahélien et savane dérivée, respectivement, ainsi que forêt et montagne. Le bétail fournit aux humains le complément complet d'acides aminés, qui sont les seuls fournisseurs naturels connus de vitamine B12 et fournissent également du fer, du calcium, de l'iode et du zinc. En outre, l'élevage représente 40% du produit intérieur brut agricole et contribue de manière significative à l'amélioration des moyens d'existence ruraux. Les conditions de stress sont induites chez le bétail par des conditions météorologiques difficiles qui réduisent les aliments disponibles pour eux et entravent le taux de croissance, l'efficacité de la reproduction et l'incidence des maladies qui peuvent éventuellement entraîner la mort. À la lumière des avantages de l'élevage pour l'humanité, il est nécessaire de concevoir des moyens de rendre leur résilient climatique. Certaines des stratégies éprouvées comprennent l'amélioration génétique animale pour la tolérance au stress, la culture de cultures résistantes aux maladies, à maturation précoce et à la sécheresse, la sélection et l'élevage d'espèces et de races animales tolérantes au climat.

Introduction : Au Maroc, les périodes de sècheresse sont nombreuses et ont des conséquences néfastes sur la production agricole. Le tournesol est une plante oléagineuse très affectée par la sécheresse. Les plantes oléagineuses représentent 75 % de la consommation d’huiles au Maroc. Objectif : Dans les conditions de culture d’environnement salin, l’analyse des taux de sucres extraits à partir des tiges et des feuilles permet de révéler la corrélation de l’augmentation ou l’absence d’accumulation des sucres simples et la tolérance ou la sensibilité à la salinité. Méthodologies et résultats : La culture de différentes variétés commerciales d’origine France et Maroc de tournesol révèle des pourcentages de diminution comprises entre 0% et 38 % et entre 0 % et 60 % respectivement dans l’environnement de NaCl 60 mM et de NaCl 120 mM chez les différentes variétés étudiées. Les rapports de la teneur des sucres extraites des tiges et des feuilles dans les conditions de NaCl 60 mM par rapport à la teneur sucres témoins et ceux de la teneur des sucres dans les conditions de NaCl 120 mM par rapport à la teneur des sucres témoin sont compris entre 1,042 et 1,50 et entre 1,88 et 2,16 respectivement chez les différentes variétés étudiées. Conclusion et Application des résultats : Ces variétés présentent une variabilité de la tolérance et la sensibilité. 2 variétés de tournesol (AG5640 et MK 3790) présentent une tolérance à l’environnement, 2 variétés de tournesol (Natil et Cliosol) présentent une tolérance modérée et 6 variétés (Santaffe, ORO 9, Albena, Santos, Florinne et Fleury) sont sensibles. Chez ces variétés étudiées l’accumulation de sucres simples dans les feuilles et les tiges dans l’environnement salin pourrait contribuer au maintien de l’équilibre osmotique au niveau cellulaire dans des conditions de déshydratation. D’autres études basées sur l’identification des paramètres génétiques et physiologiques permettront un criblage précoce de plantes adaptées à des contraintes liées aux stress salin et hydrique et classer les différentes variétés selon leur tolérance aux stress salin. Mots clés : Sélection tournesol, stress salin, tiges, feuilles, sucre. Ouazzani et Moustaghfir, J. Appl. Biosci. 2020 Accumulation des sucres dans les tiges et les feuilles de différentes variétés de tournesol exposées à l’environnement salin 15906 ABSTRACT Introduction: In Morocco, periods of drought are numerous and have negative consequences on agricultural production. Sunflower is an oilseed plant that very affected by drought. Oil plants represent 75% of oil consumption in Morocco. Objective: Under conditions of cultivation in a saline environment, analysis of the levels of sugars extracted from stems and leaves reveals the correlation of the increase or absence of accumulation of simple sugars and the tolerance or sensitivity to salinity. Methodologies and results: The cultivation of different commercial varieties of French and Moroccan origin of sunflower in a saline environment reveals percentages decrease in the fresh weight ranging between 0% and 38% and 0% and 60% respectively in the environment of 60 mM and 120 mM of NaCl in the different varieties studied. The ratios of the content of sugars extracted from the stems and leaves under the conditions of 60 mM NaCl conditions compared to the control sugar content and those of the content 120 mM NaCl conditions compared to the control sugar content are between 1.042 and 1.50 and between 1.88 and 2.16 respectively in the different varieties studied. Conclusion and Application of results: These varieties exhibit variability in tolerance and susceptibility. 2 varieties (AG5640 and MK 3790) show environmental tolerance, 2 varieties (Natil and Cliosol) show moderate and 6 varieties (Santaffe, ORO 9, Albena, Santos, Florinne et Fleury) are susceptible. In these varieties studied, the accumulation of simple sugars in leaves and stems in the saline environment could help maintain osmotic balance at the cellular level under dehydrated conditions. Further studies based on the identification of genetic and physiological parameters will allow an early screening of plants screening of plants adapted to constraints linked to salt and water stress to classify the different varieties according to their tolerance to salt stress. Keywords: Sunflower selection, salt stress, stems, leaves,sugars

Après avoir été longtemps dépendante des pesticides, l’agriculture mondiale est aujourd’hui frappée par un courant qui favorise des pratiques plus durables et plus respectueuses de l’environnement. Pour répondre à ces nouvelles exigences, les agriculteurs doivent se tourner vers l’exploitation et la rentabilisation des ressources naturelles par le biais de pratiques agricoles combinant la performance et la protection des cultures à un moindre coût écologique. Dans ce contexte, le développement de molécules biologiques capables de stimuler les défenses naturelles des végétaux (SDN) est une stratégie qui attire de plus en plus l’attention. Une molécule SDN est un éliciteur susceptible de déclencher une série d’évènements biochimiques menant à l’expression de la résistance chez la plante. La perception du signal par des récepteurs membranaires spécifiques et sa transduction par diverses voies de signalisation conduisent à la synthèse et à l’accumulation synchronisée de molécules défensives parmi lesquelles certaines jouent un rôle structural alors que d’autres exercent une fonction antimicrobienne directe. Les barrières structurales contribuent à retarder la progression de l’agent pathogène dans les tissus de la plante et à empêcher la diffusion de substances délétères telles des enzymes de dégradation des parois ou des toxines. Les mécanismes biochimiques incluent, entre autres, la synthèse de protéines de stress et d’inhibiteurs de protéases ainsi que la production de phytoalexines, des métabolites secondaires ayant un fort potentiel antimicrobien. Les progrès remarquables accomplis ces dernières années en termes de compréhension des mécanismes impliqués dans la résistance induite chez les plantes se traduisent aujourd’hui par la commercialisation d’un nombre de plus en plus important de SDN capables de stimuler le « système immunitaire » des plantes en mimant l’effet des agents pathogènes.

The research goal is improving the stability and yield response of durum wheat. The search for intensive varieties with high stability is justified and is currently one of primary selective direction. Under climate change with increas-ing stress on the process of forming yield of cultivated crops, the resistance of varieties to adverse factors and re-sponse to favorable conditions are the key factors of yield productivity growth and are considered prime selective directions. The research included identification within the system of ecological and geographical studies of both broad-range varieties adapted to cultivation in the steppe regions of Russia and Kazakhstan, and varieties of local significance for specific environmental conditions of the distribution areas. Three ecological and geographical ex-periments were carried out. The first one was based on 28 selective standard lines of the KASIB (Kazakh-Sibirian wheat selection), studied in four ecological and geographical locations: Barnaul, Omsk, Bezenchuk, Orenburg. The second experiment included selective lines of the Samara Research Institute of Agriculture studied in ecological and geographical locations of Krasnodar, Orel, Bezenchuk, Orenburg, Barnaul. The third one was formed of seven selective lines of the Samara Research Institute of Agriculture and three lines of Orenburg Research Agricultural Institute studied there and Bezenchuk. Primary genotypic selections for wide range use were identified – 1693D-71, 2006D-44(454), 2126D-1(525), 2219D-3(557) by Samara Research Institute of Agriculture, Hordeiforme 08-107-5 by Omsk Agriculture Research Centre, Hordeiforme 910 and Hordeiforme 895 by Altai Resarch Institute of Agricul-ture and of Local significance – 1941D-17, 1941D-19, 2201D-4 by Samara Research Institute of Agriculture result-ed from studies using the regression analysis of yield data.

Les agriculteurs font partie d’une catégorie socioprofessionnelle qui exprime une certaine forme de malaise due à une multitude de pressions et de mutations de leur métier. Notre approche est focalisée sur les différences interindividuelles contribuant à l’adaptation et à la résistance dans un contexte particulièrement menaçant ou bien favorisant l’aggravation d’un état de souffrance psychologique. Dans ce but, nous nous centrons sur le concept de ressources, et notamment sur le modèle de Conservation des ressources (Hobfoll, 1989), afin de comprendre quelles sont les ressources matérielles, énergétiques, personnelles et en termes de conditions sociales dont les gains sont les plus protecteurs et les pertes les plus délétères pour la santé des agriculteurs. Pour éprouver nos hypothèses, cette recherche repose sur une méthode de recueil quantitative et longitudinale en deux temps de mesure auprès d’une cohorte d’agriculteurs lorrains. Ainsi, la santé est évaluée en termes de bien-être (bonheur, vigueur, satisfaction de vie, santé perçue) et de mal-être (stress, épuisement professionnel, douleurs musculosquelettiques). Nos résultats, obtenus à l’aide de modèles structuraux (approche Partial Least Square Path Modeling), nous confirment la prépondérance des effets délétères des pertes de ressources sur la santé à T1. À l’inverse, et dans une plus faible mesure, les gains de ressources la protègent. Par ailleurs, le changement dans la santé à T2 est prédit uniquement par l’érosion des ressources. Nos résultats soulignent la nécessité de prévenir les pertes de ressources psychologiques et de conditions sociales, puis énergétiques pour préserver la santé des agriculteurs
Farmers are part of a socio-professional category that expresses some form of unease due to multiple pressures and changes in their profession. Our approach focuses on interindividual differences contributing to adaptation and resistance, in a particularly threatening context, or favoring the worsening of a state of psychological suffering. To this end, we focus on the concept of resources and in particular on the Conservation of Resources theory (Hobfoll, 1989). This theory allows us to understand which are the material, energy, personal characteristics and conditions resources and among them, which gains are the most protective and which losses are the most destructive of the farmers' health.To test our hypotheses, this research is based on a two-stage quantitative and longitudinal measurement method for a cohort of Lorraine (France northeastern region) farmers. Thus, health is assessed in terms of well-being (happiness, vigor, life satisfaction, perceived health) and ill-being (stress, burnout, musculoskeletal pain). Our results obtained by using structural models (Partial Least Square Path Modeling) confirm the preponderance of the deleterious effects of resources’ losses on health at T1, conversely, and to a lesser extent, that the resources’ gains protect it. On the other hand, the change in health at T2 is predicted only by resource erosion. Our results underline the need to prevent the loss of personal and conditions resources and then energy to preserve farmers’ health

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico
With the increasing of areas degraded by soil salinization process, is necessary to increase of agricultural investments to be able to reach a production acceptable. In order to reduce such inputs, studies of microorganisms involved in the production process are becoming more constant. The objective of this study was to evaluate the associations between endophytic fungi Dark Septate and cowpea plants when irrigated with water of different salinities, analyzing biometrics, gas exchange, nutrient content and accumulation of organic solutes in the leaves. Cowpea plants were grow in containers of five liters under greenhouse conditions and subjected to four different electrical conductivity of irrigations water (1.2; 2.2; 3.6; 5.0 dS m-1). Were used for the inoculation strains Bâ2 and 21W and treatments were as follows: F1 â plants that were not inoculated; F2 â plants inoculated with strains 21W and F3 â plants inoculated with strain Bâ2. during the experiment was measured gas exchange and at the end of the experiment the plant were collected and determinate the leaf area, shoot dry mass, root dry mass, concentration of the foliar nutrients and organic solutes, and was made the determination colonization of roots by the fungus. The salinity caused significant reductions in biomass, leaf area and leaf gas exchange, however, the presence of the endophytic fungi provided a large tolerance to the adverse effects of salinity. There was a larger accumulation of calcium, sodium, clore and phosphorus in cowpea leaves with increasing salinity and decrease in the leaves of nitrogen and potassium. The presence of the fungus in the plant provided a foliar phosphorus and nitrogen.
With the increasing of areas degraded by soil salinization process, is necessary to increase of agricultural investments to be able to reach a production acceptable. In order to reduce such inputs, studies of microorganisms involved in the production process are becoming more constant. The objective of this study was to evaluate the associations between endophytic fungi Dark Septate and cowpea plants when irrigated with water of different salinities, analyzing biometrics, gas exchange, nutrient content and accumulation of organic solutes in the leaves. Cowpea plants were grow in containers of five liters under greenhouse conditions and subjected to four different electrical conductivity of irrigations water (1.2; 2.2; 3.6; 5.0 dS m-1). Were used for the inoculation strains Bâ2 and 21W and treatments were as follows: F1 â plants that were not inoculated; F2 â plants inoculated with strains 21W and F3 â plants inoculated with strain Bâ2. during the experiment was measured gas exchange and at the end of the experiment the plant were collected and determinate the leaf area, shoot dry mass, root dry mass, concentration of the foliar nutrients and organic solutes, and was made the determination colonization of roots by the fungus. The salinity caused significant reductions in biomass, leaf area and leaf gas exchange, however, the presence of the endophytic fungi provided a large tolerance to the adverse effects of salinity. There was a larger accumulation of calcium, sodium, clore and phosphorus in cowpea leaves with increasing salinity and decrease in the leaves of nitrogen and potassium. The presence of the fungus in the plant provided a foliar phosphorus and nitrogen.

Orientador: Priscila Lupino Gratão
Banca: Tiago Tezotto
Banca: Rogério Falleiros Carvalho
Resumo: O tomateiro é uma das hortaliças mais cultivadas em ambiente protegido, destacando-se entre as hortaliças melhor adaptadas a esse sistema de cultivo. A produção e qualidade dos frutos estão diretamente relacionadas com a qualidade da água utilizada e o manejo adequado da irrigação. Para propor estratégias de manejo no uso de água salina na irrigação de tomateiro, o presente estudo teve como objetivo avaliar o crescimento, desenvolvimento, rendimento; qualidade e respostas antioxidantes do tomateiro cultivado sob estresse salino parcial do sistema radicular. O experimento foi conduzido em ambiente protegido na Universidade Federal Rural do Semi-Árido (UFERSA), em Mossoró, RN, Brasil. O delineamento estatístico utilizado foi o inteiramente casualizado, com seis tratamentos e quatro repetições, totalizando 24 unidades experimentais. Os tratamentos consistiram de seis manejos de irrigação utilizando águas de baixa e alta salinidade (S1-0,5 e S2-5,0 dS m-1), com ou sem divisão do sistema radicular. Para os tratamentos T1, T2 e T3 não houve divisão do sistema radicular, sendo que para tratamentos T4*, T5* e T6*, foi adotado o sistema de divisão das raízes. O número de folhas, área foliar, altura de planta, diâmetro de caule e partição de fotoassimilados (massa seca de folha, caule, raiz, fruto e total) foram os parâmetros de crescimento determinados. Diâmetro transversal, diâmetro longitudinal, número de frutos por planta, massa fresca média de fruto, produção, pH, Firmeza de polpa... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Tomato is one of vegetables most cultivated in greenhouses, standing out among the plants adapted to this cropping system. The production and fruit quality are directly related to the quality of water used for irrigation and its appropriate management. In order to propose management strategies for use of saline water irrigation in tomato crop production, the present study aimed to evaluate the growth and development of plants, yield and quality, and antioxidant responses of tomato cultivated under a partial salt stress of the root system. The experiment was carried out in a greenhouse at the Universidade Federal Rural do Semi-Árido (UFERSA), Mossoró, RN, Brazil. The experimental design was completely randomized, with six treatments and four replicates, totaling 24 experimental units. The treatments consisted of six different irrigation managements using low and high saline water (S1-0.5 and S2-5.0 dS m-1), applied with or without the partial root-zone saline irrigation (PRSI). For the treatments T1, T2 and T3, the PRSI was not applied, whilst T4*, T5* and T6* treatments were under the PRSI. The number of leaves, leaf area, plant height, stem diameter and dry weight of leaf, stem, root and, fruit were determined as plant growth parameters. Cross diameter, lengthwise diameter, number of fruits per plant, mass average fresh fruit, yield, pH, pulp firmness, soluble solids content, titratable acidity, vitamin C, color relation (a*/b*), lycopene and β-carotene were determined as pa... (Complete abstract click electronic access below)
Mestre

Dans les écosystèmes aquatiques, l'activité anthropique, mais aussi le contexte naturel induisent chez les organismes aquatiques des situations de stress multiples. Parmi les sources potentielles de perturbation, trois d'entre elles, d’origine chimique, ont été étudiées : contamination métallique, une contamination par un herbicide, par un mélange d’alkylphénols polyéthoxylés et enfin une contamination par un produit pétrolier. Cette démarche entre dans le cadre de la directive européenne REACh (Registration Evaluation Autorisation of CHemicals) mais aussi de la directive cadre eau DCE (directive 2000/60/CE) du parlement Européen et du Conseil établissant une politique communautaire dans le domaine de l'eau. Il s’agit en fait d'évaluer la pertinence d’une série d’indicateurs précoces de pollution (ex : biomarqueurs) afin de prédire l'effet des substances chimiques lors de contaminations chroniques ou ponctuelles du milieu aquatique. Une approche intégrée des interactions des substances ou produits sélectionnés sur la réponse génétique, protéique, cellulaire, histologique et individuelle chez la truite arc-en-ciel, Onchorynchus mykiss, a été entreprise en mésocosmes ouverts et dynamiques et en laboratoire. In vivo, une étude multimarqueurs sur des truites juvéniles femelles diploïdes a été menée à chaque exposition, de 21 ou 28 jours, et durant une période de « récupération » afin d'estimer les effets sur la physiologie des truitelles. Le mélange de nonylphénols polyéthoxylés et l’essence utilisés pour les expositions montrent ainsi des effets qui perdurent jusqu’à la fin de cette période de « récupération ». Les mésocosmes, utilisés lors de cette thèse, offrent des conditions favorables au maintien et à la croissance de truites juvéniles. (...) Dans une démarche de recherche de biomarqueurs d’effets chez une espèce modèle, transposer ces travaux chez des poissons (mâles et femelles) à des stades de développement différents pourrait ainsi permettre d’isoler les paramètres les plus pertinents, à chaque stade ou pour l’ensemble du cycle de l’espèce, afin d’apporter de nouveaux outils pour la surveillance des milieux aquatiques
In the aquatic ecosystems, anthropic activity, but also natural environment induce several kind of stress in aquatic organisms. Among the potential sources of stress, three chemicals were studied here: a metal, a bipyridylium herbicide, a mixture of nonylphenol polyethoxylate and an oil product exposure. This study enters within the framework of the European directive REACh (Registration Evaluation Authorization of CHemicals) but also of the Directive Cadre Eau, DCE (directive 2000/60/CE) of the European Parliament. The aim is to evaluate the relevance of an early pollution indicator pool (biomarkers) in order to predict chemical substance effects during chronic exposure or after specific contaminations of the aquatic compartment. An integrated approach of the substance effects on the genetic, proteinic, cellular, histological and individual answers in the rainbow trout, Onchorynchus mykiss, were undertaken in open and dynamic mesocosms and also laboratory. In vivo, a multibiomarker study on female juvenile trout was done at each exposure, over 21 or 28 days, followed by a period of “recovery». The mixture of nonylphenol polyethoxylate and the gasoline used for the exposures thus show effects which perdurent until the end of this period of “recovery. The mesocosms used in this study offer favorable conditions for juvenile survival and growth. (...) In addition to the assessment of the measurement robustness and the biomarker relevance, we compared the data obtained in this study with the in vivo tests and those obtained using in vitro tests. This approach made possible to highlight coherent answers between in vitro the tests and in vivo markers. But in vitro tests are only one preliminary approach to quickly seek a specific toxic action. The modulation monitoring of key genes in the fish reproduction function, during a gasoline exposure, offers complementary informationabout the pollutant mode of action. We noted that the effects of the contamination on the hormonal rates were differed in time compared to the modulation of the gene transcription. In order to bring new tools for the monitoring, in a model species, of the aquatic environment,transposing this work in male and female fish at different developmental stages would enableisolating still most relevant parameters

Le pois (Pisum Sativum L.) possède la capacité de fixer le diazote atmosphérique (N2) via une symbiose avec des bactéries du sol au sein d’organes racinaires que sont les nodosités. Bien que cette particularité rende cette espèce particulièrement intéressante dans un contexte de transition agro-écologique, la fixation symbiotique du N2 est cependant sensible aux stress abiotiques tels que le déficit hydrique du sol, ce qui contribue à l’instabilité du rendement du pois et réduit son attrait chez les agriculteurs. La stabilité du rendement dépend à la fois de la capacité de la plante à tolérer un stress, mais aussi de sa capacité à récupérer après ce stress. Or, les mécanismes impliqués pendant la phase de récupération demeurent peu explorés. Il est ainsi essentiel d’identifier des traits de plantes maximisant la résilience du pois au déficit hydrique, afin de proposer des idéotypes mieux adaptés à des conditions environnementales de disponibilité en eau ou nutriments fluctuantes.Les principaux objectifs de cette étude étaient dans un premier temps d’identifier les processus écophysiologiques impliqués pendant la phase de récupération, après un épisode de déficit hydrique, et en considérant en particulier la croissance de la plante et son acquisition d’azote. Dans un deuxième temps, il s’agissait de déterminer les composantes moléculaires sous-jacentes à ces mécanismes de récupération au sein des racines et des nodosités. Au cours d’une première expérimentation réalisée sur la plateforme de phénotypage 4PMI (Dijon, France) nous avons analysé en détail la dynamique de récupération de deux génotypes de pois après leur avoir imposé un déficit hydrique de deux semaines. Alors que pour l’un des génotypes (Kayanne) le rendement à maturité physiologique était maintenu sous ces conditions de déficit hydrique temporaire, le rendement du second génotype étudié (Puget) a été négativement affecté par le déficit hydrique. Nous avons utilisé conjointement une approche au niveau plante entière (en utilisant un cadre d’analyse écophysiologique axé sur les flux de carbone, azote et eau dans la plante) à des approches de type « omiques » (métabolomique, transcriptomique et dosages de phytohormones) dans les compartiments racinaires et nodulaires. Cette analyse a été complétée par une seconde expérimentation impliquant des marquages isotopiques au 13C et 15N2 qui nous a permis de mesurer précisément les flux de carbone et d'azote dans le continuum sol-plante-atmosphère.Nos analyses ont révélé que les deux génotypes étudiés avaient des capacités de résilience contrastées, en partie expliquées par la mise en place de différentes stratégies de récupération pendant la période de ré-arrosage, et impliquant des processus liés à la nutrition azotée de la plante. Nous avons démontré que pendant la phase de récupération, Kayanne pouvait rapidement ajuster la formation de ses nodosités en fonction de ses besoins en azote pour sa croissance, lui permettant ainsi de récupérer totalement après deux semaines de déficit hydrique. Au contraire, la restauration du statut azoté chez le génotype Puget a été initiée plus tardivement mais plus intensément aboutissant à une surcompensation en termes de nombre de nodosités formées. Nous avons donc émis l’hypothèse que le fort coût en énergie résultant de la surcompensation nodulaire s’est effectué aux dépends de la croissance de la plante, impactant in fine le rendement de Puget
Pea (Pisum sativum L.) has the unique ability to fix atmospheric dinitrogen (N2) via a symbiosis with soil bacteria in root nodules. Although this specificity makes this crop particularly interesting in the context of agroecological transition, symbiotic nitrogen fixation is particularly sensitive to abiotic stresses such as water deficit, which contributes to the yield instability of this protein crop and reduces its interest for farmers. Yield stability depends both on plant's ability to tolerate stress and on its ability to recover after stress. However, the mechanisms involved during the recovery period have been for now poorly explored. It is, therefore, essential to identify traits of plants maximizing pea resilience to water deficit, in order to propose new ideotypes that are better adapted to environmental conditions of fluctuating water or nutrient availabilities.The main objectives of this study were: i) to identify the ecophysiological processes involved during the recovery period following a water deficit, considering in particular plant growth and plant nitrogen acquisition, and ii) to determine the underlying molecular processes within roots and nodules.During a first experiment in controlled conditions (4PMI Platform, Dijon, France), the dynamics of recovery of two pea genotypes were analyzed in detail after imposing plants before their flowering to a water deficit of two weeks. While one of the genotypes, (Kayanne), was able to maintain its yield under these conditions, yield of the other one (Puget) was decreased by water deficit. We have used both a) a whole-plant approach (using an ecophysiological framework focused on carbon, nitrogen and water fluxes in the plant) and b) so-called "omics" approaches (metabolomics, transcriptomics, and phytohormone assays) concerning root and nodule compartments. This analysis was completed by a second one where 13C and 15N2 isotopic labeling experiment allowed us to precisely measure carbon and nitrogen fluxes in the soil-plant-atmosphere continuum.Our analyses revealed that the two genotypes studied had contrasting resilience abilities, partly explained by different recovery strategies during the re-watering period, and particularly implying processes which were related to nitrogen nutrition. We have demonstrated that during the recovery period Kayanne was able to quickly and strictly re-adjust the formation of nodules to its growth needs, allowing this genotype to fully recover from the 2-week water deficit period. On the other hand, in Puget, the initiation of new nodules after water deficit was delayed compared to control plants, but numerous additional nodules developed. We hypothesized that the associated larger energy cost, which occurred to the detriment of growth, would finally negatively impact Puget’s yield.This difference in the dynamics of the root system response to re-watering was comforted by the molecular analysis performed in root and nodule compartments. The "omics" analysis also highlighted differences in antioxidant and osmoprotective responses between the two genotypes that could help to explain the delay observed for the recovery of the two genotypes.Altogether these results give new insights for the understanding of the regulatory mechanisms underlying the recovery of pea plant after a water deficit. Next step will consist in a statistical integration of the multi-scaled data (ecophysiological, hormonal, metabolomic and transcriptomic data), which should make it possible to identify the main regulators involved in recovery, for breeding strategies leading to the selection of pea ideotypes better suited to fluctuating water conditions

L'objectif de ce travail était d'élaborer un outil de diagnostic a posteriori du stress hydrique perçu par la vigne, utilisable en réseau de parcelles. L'outil reposait sur le couplage d'un modèle de bilan hydrique à un modèle de classement de l'activité des sources d'assimilats et des puits végétatifs sous contrainte hydrique pour caractériser, à un pas de temps journalier, l'influence de l'alimentation hydrique sur l'état de la plante (relations sources - puits). Le modèle de classement était établi à partir de relations entre la fraction d'eau du sol transpirable par la vigne (FTSW) et l'assimilation nette maximale ou des paramètres et indicateurs composites de croissance végétative des ramifications. Le modèle de bilan hydrique simulant FTSW était paramétré pour chaque parcelle à partir de mesures de potentiels hydriques de base (Yb) par optimisation d'un paramètre (la quantité totale d'eau du sol transpirable par la vigne) sur la base d'une relation empirique entre Yb et FTSW
This study was aimed to elaborate a tool to diagnose a posteriori the water stress experienced by vine, witch could be used in a network of farmer's fields. The tool was based on the coupling of a water balance model with a model of classification of assimilates sources and vegetative sinks activities under water stress to characterise, at a daily time step, the influence of water supply on plant status (sources-sinks relationships). The classification model was established from relationships between the fraction of vine's transpirable soil water (FTSW) and maximal net assimilation or parameters and composite indicators of vegetative growth on lateral branches. The water balance model simulating FTSW was parametrized for each farmer's field from predawn leaf water potential measurements (Yb) by the optimisation of a parameter (the total vine's transpirable soil water) on an empirical relationship between Yb and FTSW

Le stress est impliqué dans le développement et l'exacerbation de diverses pathologies notamment au niveau intestinal. Les effets du stress dépendent de l'expression de neuromédiateurs spécifiques (CRF) et de leurs récepteurs. Notre étude porte sur la régulation et la fonction du CRF2 au niveau des entérocytes et des cellules tumorales coliques humaines. In vivo, nous avons montré que le stress et l'inflammation conduisent à l'augmentation de l'expression du CRF2 dans les colonocytes chez le rat. Dans les tumeurs, l'expression du CRF2 augmente avec le grade tumoral. In vitro, dans les cellules HT-29, l'activation du CRF2 induit une altération des jonctions adhérentes et des adhérences focales par la voie Src/ERK/FAK. Ces mécanismes sont responsables de la régulation de la perméabilité épithéliale et de l'augmentation de la migration des cellules tumorales. Ces travaux contribuent à la compréhension des mécanismes impliquant le stress dans le développement des pathologies intestinales.

La recherche a porté sur les perceptions des apprentissages scolaires d'enseignants de l'Enseignement agricole dans le rapport à leur activité. Nous avions fait l'hypothèse que les enseignants produisent, reproduisent voire réactivent leurs perceptions des apprentissages scolaires, quels que soient les composants, chaque fois que dans l'exercice de leur métier, il est question de ces apprentissages, voire qu'ils les associent à un bien-être, un mal-être dans leur travail. Pour saisir quel pouvait être le lien entre ces apprentissages et leur activité, nous sommes partie de plusieurs théories qui pourraient s'emboîter, ou s'additionner entre ce qui contribue à la formation des perceptions des apprentissages scolaires de l'enseignant et à leur expression dans son environnement professionnel. Il y a production ou reproduction d'apprentissages scolaires quand l'enseignant mobilise l'habitus (legs familial), quand il met en abîme (effet de miroir) sa formation scolaire dans les situations de transmission, quand il met en scène les influences de son environnement (familial, scolaire, social) agissant durant sa formation scolaire. Enfin quand des conditions de travail plus ou moins délétères catalysent des réminiscences d'apprentissages scolaires. Les résultats de notre étude ont montré que selon le contexte, les situations professionnelles rencontrés, l'enseignant compose ou négocie ou confronte ses perceptions des apprentissages scolaires. Cependant chaque enseignant reste singulier dans ses perceptions des apprentissages scolaires et dans les formes de liens qui peuvent s'opérer (conduites sociales, logiques) avec son activité
The research concerned the perceptions of teachers' school learnings of the Agricultural education, in the report in their activity. We had made the hypothesis which the teachers produce, reproduce even reactivate their perceptions of the school learnings, whatever are components, every time in the exercise of their job, it is about these learnings, even that they associate them with a well-being, an ill-being in their work. To seize what could be the link between these learnings and their activity, we left several theories which could fit, or add up between what contributes to the training of the perceptions of the school learnings of the teacher and to their expression in its professional environment.There is production or reproduction of school learnings when the teacher mobilizes the habit (domestic legacy), when he puts in abyss (effect of mirror) his school training in the situations of transmission, when he stages the influences of his environment (family, school, social) acting during his school training. Finally when the more or less noxious working conditions catalyse recollections of school learnings.The results of our study showed that according to the context, the professional situations met, the teacher makes up, either negotiates or confronts his perceptions of the school learnings. However every teacher remains singular in his perceptions of the school learnings and in the forms of links which can take place ( social, logical conducts) with his activity

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Wheat is the main winter crop in Rio Grande do Sul State. Temperature and photoperiod are the major environmental factors that control development in wheat. Wheat plants exposed to cold, non freezing temperatures induce them to enter the reproductive phase. Temperature and photoperiod response functions are used to simulate the wheat development. Developmental models are important part of water soil balance, growth and yield crop models. Thus, the objectives of this thesis were: (i) to evaluate vernalization sensitivity of some Brazilian wheat genotypes and to fit a vernalization response function for these genotypes; (ii) to determine the best temperature, photoperiod and vernalization functions to simulate wheat development with the Wang and Engel (WE) model for some Brazilian wheat genotypes; and (iii) to improve the prediction of available soil water in the soil by modifying two mechanistic models. To achieve the first objective, a factorial experiment with eight levels of vernalization (0, 7, 14, 21, 28, 35, 42 and 49 vernalization days) and six wheat genotypes were used. Also a field experiment was carried out in Santa Maria, RS, Brazil, to provide independent data on the date of developmental stages of six Brazilian wheat genotypes for evaluating the original and the modified WE model. Soil water content was determined with the gravimetric method to evaluate water balance models during three sowing dates. For those genotypes that presented some response to vernalization, response functions are presented, which can be used in models for simulating the development of Brazilian wheat cultivars with distinct vernalization requirements. The WE model simulates better the development of the Brazilian wheat genotypes using cardinal temperatures higher than original WE model and using daily maximum and minimum temperatures in the calculation of the temperature response function. The modified Campbell; Diaz water balance model is more realistic and has a greater potential for performing well in regions others than it was developed. The modified Amir; Sinclair water balance model simulates better the available soil water than the original model.
O trigo é a principal cultura de inverno do Estado do Rio Grande do Sul. A temperatura e o fotoperíodo são os dois elementos meteorológicos que mais influenciam o desenvolvimento de plantas de trigo. Quando se expõem plantas de trigo a temperaturas baixas não congelantes, estas podem ser induzidas a entrarem no estágio reprodutivo, diminuindo o seu ciclo de desenvolvimento. Para simular o desenvolvimento do trigo são utilizadas funções de resposta a temperatura e fotoperíodo. O modelo de desenvolvimento é parte importante em modelos de simulação de balanço de água no solo, crescimento e rendimento das culturas. Assim, os objetivos desta tese foram: (i) determinar a sensibilidade à vernalização de alguns genótipos de trigo do sul do Brasil e, ajustar uma função de reposta a vernalização para aqueles que apresentaram sensibilidade; (ii) determinar a melhor função de temperatura, fotoperíodo e vernalização para simular o desenvolvimento de alguns genótipos brasileiros de trigo com o modelo de Wang e Engel (WE); e (iii) obter uma melhor predição do balanço de água no solo, modificando dois modelos mecanísticos de balanço de água no solo. Para atingir o primeiro objetivo, foi conduzido um experimento fatorial com oito níveis de vernalização (0, 7, 14, 21, 28, 35, 42 e 49 dias de vernalização) e seis genótipos de trigo. Também foi realizado um experimento com várias datas de semeadura em Santa Maria, RS, Brasil, para obtenção de dados independentes dos estágios de desenvolvimento de seis genótipos Brasileiros de trigo para avaliar o modelo WE modificado. Foi determinado o conteúdo de água no solo pelo método gravimétrico em três datas de semeadura, com a finalidade de avaliar o desempenho dos dois modelos de balanço de água no solo. Para os genótipos que apresentaram resposta à vernalização são apresentadas funções de resposta, que podem ser usadas em modelos de simulação do desenvolvimento de genótipos brasileiros de trigo. O modelo WE simula melhor o desenvolvimento do trigo quando são usadas as temperaturas cardinais maiores do que as do modelo original e usando as temperaturas mínimas e máximas diária para o cálculo da função de resposta a temperatura. O modelo de balanço de água no solo de Campbell; Diaz modificado é mais realístico e com maior possibilidade de desempenho satisfatório em regiões de clima distinto daquelas em que foi desenvolvido. O modelo de balanço de água no solo de Amir; Sinclair modificado estima melhor a água disponível no solo que o modelo original.

In chapter 5 Tacitus’ historical writings are divided into three units: 1) the Agricola and the Germania, 2) the Histories, and 3) the Annals, not to refer to successive stages in the evolution of his understanding of virtus, but to stress the repeated insistence by which he delineates the expressions of virtus in three diferent periods of Roman history. By identifying what was essential to Roman virtus and what was superfluous and susceptible to change, Tacitus illustrates how, even though a certain degree of political freedom was lost, there were some Romans who could exercise a more ‘personal’ freedom which led to new manifestations of virtus. Tacitus’ perception of the nature of political change is one of the main themes used throughout the chapter to plot the barriers that virtus had to overcome in the new world of the principate.