Effets de la nutrition azotée et du stress hydrique sur la maturation et la composition en anthocyanes des baies de Vitis vinifera L. au vignoble et en conditions contrôlées

Les incidences de la nutrition azotée et de l'alimentation hydrique de la vigne sur la maturation des raisins et sur la synthèse des anthocyanes dans les pellicules ont été étudiées sur des plants de Vitis vinifera L. cv. Merlot. Les expérimentations ont été conduites sur des plants cultivés au vignoble (variations simultanées des disponibilités en eau et en azote induites par un enherbement permanent) et en serre en hydroponique (boutures fructifères et plants en pots de deux ans). La maturation du raisin est favorisée par la limitation de la nutrition azotée et par la réduction de l'alimentation hydrique des vignes. Notre travail met également en évidence des interactions de la nutrition azotée et de l'alimentation hydrique avec l'ensemble de l'alimentation minérale de la vigne (en particulier P et K). Une alimentation hydrique réduite ou une nutrition limitée en azote stimulent la synthèse d'anthocyanes tandis qu'un niveau d'azote très élevé semble inhiber cette synthèse. Cet effet inhibiteur n'est pas observé sous contrainte hydrique. Les alimentations hydrique et azotée exercent donc probablement un contrôle sur l'activité d'une ou de plusieurs enzymes impliquées dans les premières étapes de la voie de biosynthèse des anthocyanes. Les niveaux de nutrition azotée et d'alimentation hydrique conduisent à des profils d'anthocyanes différents. La réduction de l'alimentation hydrique favorise la synthèse des dérivés de la malvidine. A l'inverse, une diminution de la nutrition azotée limite leur synthèse. Ces facteurs environnementaux semblent agir différemment sur les enzymes impliquées dans la synthèse des différentes formes d'anthocyanes. Les différents profils observés pourraient également être le fait de l'activation ou de la limitation du catabolisme des anthocyanes. Au vignoble, le niveau de réponse de la vigne (en particulier en termes de synthèse des anthocyanes) dépend essentiellement des conditions climatiques de l'année (millésime), du terroir et du mode d'entretien du sol.We studied the effect of nitrogen nutrition and water deficit on the ripening of berries and on anthocyanins biosynthesis in the berry skins of Merlot vines (Vitis vinifera L.) The experiments have been performed either on vines cultivated in vineyard (permanent grass cover allowed simultaneous variation of nitrogen and water supply) or under controlled environmental conditions (grapevine fruiting cuttings and two-year-old potted vines). Better berry ripening was observed under nitrogen or water limited supply. Our work showed interactions between nitrogen nutrition and water supply and the whole mineral nutrition of vines (especially P and K). Under reduced water and nitrogen nutrition, an increase of anthocyanins skin content was observed while a high nitrogen supply seemed to inhibit the anthocyanins synthesis. However, this latter effect was not observed under watering constraint. Our results suggest that water and nitrogen supply have a regulatory effect on the activity of the enzymes involved in the first steps of anthocyanins pathway. Different profiles of the anthocyanins species were obtained depending on the levels of nitrogen nutrition and watering supply. The synthesis of the malvidin derivatives was increased by a reduced water supply and was decreased by a limited nitrogen nutrition. The environmental factors seem to act differently on the esterification steps of anthocyanins biosynthesis. A regulation of the anthocyanins catabolism has to be considered too. In the vineyard, the level of anthocyanins biosynthesis depends essentially on the climatic conditions of the year (vintage), the "Terroir" effect and the cultural practices.BORDEAUX2-BU Santé (330632101) / SudocBORDEAUX1-BU Sciences-Talence (335222101) / SudocVILLENAVE D'ORNON-Bib. ISVV (335502201) / SudocSudocFranceF

Effets des facteurs hydriques et osmotiques sur la croissance des talles de ble

Les paramètres principaux régissant la croissance en longueur des talles de blé : potentiel hydrique, osmotique et de turgescence, ainsi que certains constituants de l’osmolarité ont été étudiés en conditions contrôlées et au champ. L’influence de ces paramètres sur la régression des talles observée généralement au cours de la montaison a été recherchée. On observe une compartimentation stricte de l’eau entre les zones adultes et en croissance d’un limbe. Le potentiel hydrique des zones en croissance est peu dépendant des fluctuations des conditions agroclimatiques. Le maître brin (MB) et la talle 3 (T3) présentent des stratégies différentes de maintien de leur croissance en cas de déficit hydrique : le maître brin peut garder plus longtemps une turgescence positive avec un potentiel osmotique systématiquement plus bas que celui de la T3. Par contre, celle-ci peut croître à des pressions de turgescence plus faibles, car le potentiel seuil de croissance est plus faible que celui du maître brin. Ces caractéristiques peuvent contribuer à l’homogénéisation de la taille des talles dont la date de début d’allongement varie avec le rang. La population de T3 qui régresse au cours de la montaison n’a pas pu être caractérisée précocement par les paramètres hydriques impliqués dans les modèles décrivant l’allongement. On note cependant que les talles en régression sont plus pauvres en sucres et plus riches en nitrates.The main growth parameters, water, osmotic and turgor potential of wheat tillers are studied in controlled and field-grown plants. The objective of the study was to analyse the decline of the tiller during shoot elongation. Between the growing and the adult part of blades, there is a compartmentation of water. Water potential of the growing parts is not so dependent on variations in the environment. There are different biomechanical properties between the main and the 3rd tiller. The osmotic potential of the main tiller is lower than that of the 3rd tiller. Accordingly, the main tiller can maintain a positive turgor for longer periods. The turgor threshold of the 3rd tiller is lower and requires a lower turgor to maintain the same relative growth rate as the main tiller. These properties could lead to growth compensation between tillers. The 3rd tiller population which declines during the fast growing phase cannot be sorted at an early stage with the growth parameters we studied, as these parameters change when the decline is obvious. At that time, a decrease in sugar content and a relative increase in nitrate content are measured in declining tillers

Recherche de marqueurs associés à la contrainte en azote et en carbone chez la vigne (vitis vinifera var. Cabernet Sauvignon)

L'enjeu de la viticulture, est de produire des fruits de qualité pouvant être utilisés pour la fabrication du vin. Pour cela, les pratiques culturales portent sur le contrôle de l'apport en azote (engrais azotés) et la disponibilité en carbone (limitation de la surface foliaire). Ce travail de thèse a porté sur la recherche de marqueurs biochimiques et moléculaires associés aux conditions de contraintes en azote et en carbone, chez la vigne (Vitis vinifera var Cabernet Sauvignon). L'étude biochimique (concentration en sucre, acides aminés libres) et écophysiologique (croissance des parties végétatives) de boutures fructifères a montré que la croissance (taille des plants et surface foliaire) est le caractère le plus discriminant entre les plants sous contrainte et les plants témoin, sans toutefois permettre de discriminer la contrainte en azote de la contrainte en carbone. Une étude moléculaire a donc été entreprise par téalisation de banques HSS (Hybridation Soustractive Suppréssive) pour les plantes placées en contrainte azotée vs plantes contrôle. Le criblage de ces banques par macroarrays a mis en évidence 137 clones induits ou réprimés par la contrainte en azote.The stake of the vine growing, is to produce fruits of quality suitable for the manufacture of wine. For that, the growing methods related to the control of the nitrogen contribution (nitrate fertilizers and the availability of carbon (limitation of leaf aera). This thesis work concerned the search for biochemical and molecular markers on grape (Vitis vinifera var Cabernet Sauvignon) associated with nitrogen and carbon constraints. he biochemical (sugar concentration, free amino acids, and ecophysiologic (growth of the vegetative parts) studies of fruit-bearing cuttings showed that the growth (size if the plants and leaf aera) is the more discriminating character between the plants under constraint and control conditions. But they did not allow to disciminate the nitrogen and the carbon constraint. A molecular study was thus undertaken by realization of SSH libraries (Subtractive Suppressive Hybridization) for the plants placed in nitrogenized constraint vs control plants. The screening of these libraries by microarrays highlighted 137 clones induced or repressed by the nitrogen constraint.BORDEAUX2-BU Santé (330632101) / SudocSudocFranceF

REPARTITION DE LA BIOMASSE CHEZ VITIS VINIFERA L. ; RENDEMENT DE CONVERSION DU RAYONNEMENT SOLAIRE GLOBAL ET COUTS ENERGETIQUES

PARIS-AgroParisTech Centre Paris (751052302) / SudocSudocFranceF

Etude comparée de la photosynthèse de deux variétés de prunier (Prunus Domestica L.) greffées sur quatre porte-greffe

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Modeling carbon export out of mature peach leaves

40 ref.International audienceThe characteristics of sorbitol and sucrose export out of mature leaves in seedlings of peach (Prunus persica L. Batsch cv CF 305) were investigated by simulating carbon fluxes through the leaf. Three treatments were employed: a control treatment and two treatments modifying leaf export, the latter using either shading or girdling. Photosynthesis and 14C partitioning into sorbitol and sucrose were measured during carbohydrate pool buildup at the beginning of the photoperiod, and the export rate of sorbitol and sucrose was modeled using a PSPICE (Simulation Program with lntegrated Circuit Emphasis) simulator. The simulation allowed predidion of the resulting sorbitol and sucrose contents, which were compared to experimental carbohydrate contents. The apparent Km, for sorbitol and sucrose phloem loading, estimated by carbon flux modeling, was 6.6 and 4 mol m(-3), respedively. The predided export capacity of the leaf, charaderized by the estimated Vmax, values for phloem loading of sorbitol and sucrose, was similar to the photosynthetic carbon flux measured under the leaf growth conditions. This export capacity was enhanced in plants in which all leaves except those studied were shaded. The mature leaf had a higher storage capacity for sorbitol than for sucrose in control plants, especially in the girdled treatment. Sucrose content appears to be tightly regulated

Modeling phloem loading in peach leaves

International audienceSorbitol and sucrose export out of mature peach (Prunus persica L. Batsch) leaves was studied by simulating carbon fluxes. Photosynthesis and 14C partitioning into sorbitol and sucrose were measured at the beginning of the photoperiod and the export rate of sorbitol and sucrose was modeled using saturable functions of the exportable carbohydrate content. The C fluxes were modeled using PSPICE (Simulation Program with Integrated Circuit Emphasis, University of Berkeley) simulator. The sorbitol and sucrose contents calculated by the simulator were compared with experimental carbohydrate contents. This allowed one to estimate the apparent Km and Vmax for sorbitol and sucrose phloem loading, and to quantify the effect of a theoretical small change in Km or Vmax on export rate. The estimated Vmax values for both sorbitol and sucrose phloem loading were similar to the photosynthetic C flux into each exportable carbohydrate measured under the leaf growth conditions. However, the fate of sorbitol differed from that of sucrose. The leaf appeared to have a higher storage capacity for sorbitol than for sucrose. The content of sucrose seemed tightly regulated

Time course of carbohydrates concentration in mature leaves of peach seedlings (<em>Prunus persica</em> (L.) Batsch) during the night

National audienceThis study aims to describe the time course of non-structural carbohydrates concentration in mature leaves of peach seedlings (cv GF 305) during the night. It was observed that the rate of starch breakdown was constant all through the night. This breakdown allowed to maintain the pool of exportable carbon until the beginning of the next photoperiod. The rate of carbon export decreased throughout the night and was close to the rate of starch breakdown at the end of the dark period. The sorbitol to sucrose ratio (SSR) changed little throughout the night. The kinetic characteristics of sorbitol and sucrose synthesis and exportation are probably central points of the SSR behavior. The apparent exportation rates of sorbitol and sucrose were calculated

Carbon partitioning in source leaves of peach, a sorbitol-synthesizing species, is modified by photosynthetic rate

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