A functional–structural plant model that simulates whole- canopy gas exchange of grapevine plants (Vitis vinifera L.) under different training systems

Background and Aims: Scaling from single-leaf to whole-canopy photosynthesis faces several complexities related to variations in light interception and leaf properties. To evaluate the impact of canopy strucuture on gas exchange, we developed a functional–structural plant model to upscale leaf processes to the whole canopy based on leaf N content. The model integrates different models that calculate intercepted radiation, leaf traits and gas exchange for each leaf in the canopy. Our main objectives were (1) to introduce the gas exchange model developed at the plant level by integrating the leaf-level responses related to canopy structure, (2) to test the model against an independent canopy gas exchange dataset recorded on different plant architectures, and (3) to quantify the impact of intra-canopy N distribution on crop photosynthesis. Methods: The model combined a 3D reconstruction of grapevine (Vitis vinifera) canopy architecture, a light interception model, and a coupled photosynthesis and stomatal conductance model that considers light-driven variations in N distribution. A portable chamber device was constructed to measure whole-plant gas exchange to validate the model outputs with data collected on different training systems. Finally, a sensitivity analysis was performed to evaluate the impact on C assimilation of different N content distributions within the canopy. Key Results: By considering a non-uniform leaf N distribution within the canopy, our model accurately reproduced the daily pattern of gas exchange of different canopy architectures. The gain in photosynthesis permitted by the non-uniform compared with a theoretical uniform N distribution was about 18 %, thereby contributing to the maximization of C assimilation. By contrast, considering a maximal N content for all leaves in the canopy overestimated net CO2 exchange by 28 % when compared with the non-uniform distribution. Conclusions: The model reproduced the gas exchange of plants under different training systems with a low error (10 %). It appears to be a reliable tool to evaluate the impact of a grapevine training system on water use efficiency at the plant level.EEA MendozaFil: Prieto, Jorge Alejandro. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Mendoza; Argentina.Fil: Louarn, Gaëtan. Institut National de la Recherche Agronomique; FranciaFil: Perez Peña, Jorge Esteban. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Mendoza; ArgentinaFil: Ojeda, Hernan. Institut National de la Recherche Agronomique. Unité expérimentale de Pech Rouge; FranciaFil: Simonneau, Thierry. Institut National de la Recherche Agronomique. LEPSE Montpellier; FranciaFil: Lebon, Eric. Institut National de la Recherche Agronomique. Unité Mixte de Recherche; Franci

Delayed grape ripening by intermittent shading to counter global warming depends on carry-over effects and water deficit conditions

Grapevine phenology is continuously advancing due to global warming, exposing berry ripening to increasingly drier and hotter episodes that can dramatically affect yield and berry quality. This study aimed to analyse whether intermittent shading produced by panels placed over the plants can delay berry ripening to counter the impact of global warning on phenology. A two-year outdoor trial repeated on two batches of young potted grapevine (cv. Syrah) was conducted in Montpellier (South of France). Shading was created in a row using 2 m-wide horizontal panels placed 2.4 m above the ground. A moderate water deficit was also applied at the start of veraison to half the plants in both full sun (without panels) and shaded conditions to mimic usual field conditions. Variables related to budburst, flowering, veraison and sugar at harvest were analysed in all treatments. Although intermittent shading did not significantly modify air temperature within the canopy when cumulated over the growing season, the panels substantially delayed veraison by up to more than 30 days under well-watered conditions. The most marked phenological shifts were noted in the second year of treatment between flowering and veraison when carbon demand sharply increased during berry formation, suggesting there was a carry-over effect likely due to limited carbon assimilation. This was accompanied by sharp decreases in berry diameter and sugar content per berry at harvest. Higher berry growth and sugar loading were maintained when shading was combined with water deficit. However, the trigger effect of water deficit on veraison almost halved the phenological delay caused by the panels. Overall, a cooler period for ripening could be achieved with panels over the vines but at the expense of berry size and sugar amount in berries. It can be concluded that shading intensity and duration should be adapted to evaporative and soil water conditions to benefit from the phenological delay caused by panels, without altering production in the long term

Effects of the oral endothelin-receptor antagonist bosentan on echocardiographic and doppler measures in patients with pulmonary arterial hypertension

OBJECTIVES The purpose of this study was to investigate the effects of bosentan (125 or 250 mg twice daily) on echocardiographic and Doppler variables in 85 patients with World Health Organization class III or IV pulmonary arterial hypertension (PAH). BACKGROUND Bosentan, an orally active dual endothelin-receptor antagonist, improves symptoms, exercise capacity, and hemodynamics in patients with PAH. METHODS Patients had primary pulmonary hypertension (84%) or PAH associated with connective tissue disease. Of these, 29 patients received placebo and 56 received bosentan (1:2 randomization). Six-minute walk tests and echocardiograms were performed at baseline and after 16 weeks of treatment. RESULTS Baseline characteristics were similar in the placebo and bosentan groups, and echocardiographic and Doppler findings were consistent with marked abnormalities of right ventricular (RV) and left ventricular (LV) structure and function that were due to PAH. The treatment effect on 6-min walking distance was 37 m in favor of bosentan (p = 0.036). Treatment effects of bosentan compared with placebo on other parameters were as follows: Doppler-derived cardiac index = + 0.4 l/min/m2(p = 0.007), LV early diastolic filling velocity = + 10.5 cm/s (p = 0.003), LV end-diastolic area = + 4.2 cm2(p = 0.003), LV systolic eccentricity index = -0.12 (p = 0.047), RV end-systolic area = -2.3 cm2(p = 0.057), RV:LV diastolic areas ratio = -0.64 (p = 0.007), Doppler RV index = -0.06 (p = 0.03), and percentage of patients with an improvement in pericardial effusion score = 17% (p = 0.05). CONCLUSIONS Bosentan improves RV systolic function and LV early diastolic filling and leads to a decrease in RV dilation and an increase in LV size in patients with PAH

Recent climatic and anthropogenic imprints on lacustrine systems in the Pyrenean Mountains inferred from minerogenic and organic clastic supply (Vicdessos valley, Pyrenees, France)

High-resolution seismic profiling has been combined with geochemical analyses of both watershed samples and five lacustrine cores retrieved from two natural lacustrine basins of glacial origin: Lake Majeur and Lake Sigriou (1630 m a.s.l. and 1995 m a.s.l., respectively, Eastern French Pyrenees). Identifying specific minerogenic and organic markers of autochthonous and allochthonous supply, data allow documenting past climatic and anthropogenic pressures. Over the past century, the lacustrine sediment of Lake Majeur has been essentially composed of algae, drastically contrasting with the natural sedimentary infill of the basin, mainly resulting from soil erosion from the mid–late Holocene. Since ad 1907, the Lake Majeur has been used for hydroelectricity production. Human-induced lake-level regulations, affecting up to 37% of the lacustrine surface, have increased by fourfold the accumulation rate of the lake and favoured water enrichment. Rubidium abundance within the lacustrine sediments of the two lakes reflects the mid–late Holocene palaeohydrology. After dam construction in ad 1907, greater quantities of rubidium found in Lake Majeur sedimentary infills indicate drier climatic periods, such as from ad 1975 to ad 1982, during which water reservoirs were particularly in demand. Inversely, before the dam was built, rubidium fluctuations were correlated with wetter conditions and hydrological events were recorded as sandy layers deposited by canyon reactivation, synchronous with European climatic deterioration phases. We notably document that the Mediaeval Climate Anomaly was interrupted by some humid periods dated c. ad 940, ad 1080, ad 1100 and ad 1250. We also date the onset of the ‘Little Ice Age’ c. ad 1360 and identify that this period was wetter after c. ad 1500

Effects of the oral endothelin-receptor antagonist bosentan on echocardiographic and doppler measures in patients with pulmonary arterial hypertension

OBJECTIVES The purpose of this study was to investigate the effects of bosentan (125 or 250 mg twice daily) on echocardiographic and Doppler variables in 85 patients with World Health Organization class III or IV pulmonary arterial hypertension (PAH). BACKGROUND Bosentan, an orally active dual endothelin-receptor antagonist, improves symptoms, exercise capacity, and hemodynamics in patients with PAH. METHODS Patients had primary pulmonary hypertension (84%) or PAH associated with connective tissue disease. Of these, 29 patients received placebo and 56 received bosentan (1:2 randomization). Six-minute walk tests and echocardiograms were performed at baseline and after 16 weeks of treatment. RESULTS Baseline characteristics were similar in the placebo and bosentan groups, and echocardiographic and Doppler findings were consistent with marked abnormalities of right ventricular (RV) and left ventricular (LV) structure and function that were due to PAH. The treatment effect on 6-min walking distance was 37 m in favor of bosentan (p = 0.036). Treatment effects of bosentan compared with placebo on other parameters were as follows: Doppler-derived cardiac index = + 0.4 l/min/m2(p = 0.007), LV early diastolic filling velocity = + 10.5 cm/s (p = 0.003), LV end-diastolic area = + 4.2 cm2(p = 0.003), LV systolic eccentricity index = -0.12 (p = 0.047), RV end-systolic area = -2.3 cm2(p = 0.057), RV:LV diastolic areas ratio = -0.64 (p = 0.007), Doppler RV index = -0.06 (p = 0.03), and percentage of patients with an improvement in pericardial effusion score = 17% (p = 0.05). CONCLUSIONS Bosentan improves RV systolic function and LV early diastolic filling and leads to a decrease in RV dilation and an increase in LV size in patients with PAH

Riociguat treatment in patients with chronic thromboembolic pulmonary hypertension: Final safety data from the EXPERT registry

Objective: The soluble guanylate cyclase stimulator riociguat is approved for the treatment of adult patients with pulmonary arterial hypertension (PAH) and inoperable or persistent/recurrent chronic thromboembolic pulmonary hypertension (CTEPH) following Phase

Régulation des transferts d'eau dans la plante et conséquences sur la croissance en déficit hydrique

Mes travaux initiaux ont porté sur les mécanismes de régulation des transferts d’eau à travers la plante. Je les ai étendus depuis quelques années pour mieux comprendre l’impact des conditions climatiques contraignantes sur l’état hydrique et la croissance des organes. Face à l’accroissement des contraintes climatiques et de la compétition pour l’usage de l’eau, je contribue ainsi à la recherche de génotypes adaptés à des ressources hydriques limitées. A mes approches biophysiques initiales sur pêcher, j’ai adjoint des approches génétiques (en collaboration) et biochimiques (par des formations complémentaires) pour analyser quantitativement les processus de transfert d’eau et de contrôle de la croissance dans des plantes entières intactes (tournesol, maïs et Arabidopis), soumises à des environnements climatiques fluctuants. Je me suis largement appuyé sur la modélisation pour (i) structurer les connaissances existantes, (ii) planifier des expérimentations au regard d’hypothèses à tester, (iii) analyser les résultats, et finalement les réintégrer dans des modèles dynamiques à base biophysique. Grâce à ces approches, j’ai alimenté les modèles de réponse des plantes à l’environnement climatique, utilisés par mes collaborateurs pour l’analyse de la variabilité génétique et la définition d’idéotypes adaptés aux scénarios climatiques contraignants. J’ai construit notamment des modèles de réponse de la transpiration et de la croissance des plantes aux contraintes hydriques qui permettent une description des génotypes par des jeux de caractères les plus héritables possibles. J’ai également contribué à mettre en évidence le rôle intégré de gènes en interaction avec le fonctionnement hydraulique des plantes, ainsi qu’une cascade signalétique induite par un pathogène racinaire. J’inscris ainsi mes travaux dans le projet de l’unité que je dirige actuellement avec un engagement fort vers la biologie intégrative verticale. Mon implication dans la formation s’est traduite essentiellement par l’encadrement de nombreux(ses) étudiant(e)s et post-doctorants et plus marginalement par des cours aux étudiants de 3ème cycle (Montpellier SupAgro et Université Montpellier 2). Je leur transmets mes compétences dans 2 domaines principaux. J’explicite la démarche de modélisation comme support de formalisation et d’assemblage des connaissances en appui à l’ expérimentation. Je replace les connaissances sur la physiologie des transferts d’eau le long du continuum sol-plante-atmosphère dans une perspective d’analyse de la variabilité génétique. Mon projet personnel prolonge mes travaux sur la régulation de la croissance des plantes. Il découle de mes résultats sur l’importance des fluctuations de la turgescence cellulaire dans les tissus en expansion. Je propose en particulier d’analyser les processus qui régulent la turgescence dans les cellules en croissance. Je compte reprendre des études sur le contrôle des flux d’eau par les stomates et intégrer les acteurs impliqués dans la régulation du potentiel osmotique intracellulaire. Ces processus sont multiples et nécessitent le développement d’approches de modélisation pour gérer la complexité des interactions en jeu, et évaluer quantitativement la part de chacun d’eux. A plus long terme, je propose d’élargir mes objectifs vers l’explicitation de l’efficience de transpiration en m’appuyant sur un réseau de collaborations et une plate-forme de modélisation (OpenAléa)

Absorption d'eau en conditions de disponibilite hydrique non uniforme. Etude sur pechers en solution nutritive

* INRA, Unite Regionale de Documentation, Montfavet Diffusion du document : INRA, Unite Regionale de Documentation, Montfavet Diplôme : Dr. Ing

Water uptake regulation under non-uniform water availability

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