Análise bioquímica do carbono foliar em plantas de eucalipto submetidas a estresses hídrico e nutricional.

Resumo: Neste trabalho são apresentados os resultados preliminares das análises foliares de carbono não estrutural (açúcares, aminoácidos, ácidos orgânicos e amido) e estrutural (lignina e celulose) obtidas num plantio experimental de Eucalyptusgrandisde 3 anos de implantação. As árvores receberam dois níveis de adubação potássica (0 e 17,4 g K m-2 na forma de KCl) e foram submetidas a dois regimes hídricos (100% e 33% da precipitação). Abstract: This work presents the preliminary results about the foliar nonstructural carbon (sugars, aminoacids, organic acids and starch) and structural carbon content (lignin and cellulose) in a three years old Eucalyptus grandisexperimental area. The trees were subjected to two levels of potassium fertilization (0 and 17.4 g K m-2 applied as KCl) as well as two levels of water availability (100% and 33% of rainfall)

Structure, biogenese et roles fonctionnels des poly alpha-aminobutyrates elabores sous controle bacterien dans les nodosites de Medicago sativa L

SIGLECNRS T 57979 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Photosynthesis, Rubisco activity and mitochondrial malate oxidation in pedunculate oak (Quercus robur L) seedlings grown under present and elevated atmospheric CO 2

Pedunculate oak seedlings were grown at 350 and 700 μL/L CO2 in controlled chambers. After 130 days at elevated CO2, the biomass of the whole plant did not significantly increase. Photosynthesis, Rubisco activity, mitochondrial malate oxidation, carbohydrates and nitrogen contents were examined in the fourth growth flush. At 700 μL/L CO2, the leaf net photosynthetic rate was 220% higher than at 350 μL/L CO2. The decreased activity of Rubisco was accompanied by an accumulation of sucrose and glucose. The decreased oxidative capacity of crude leaf mitochondria from elevated CO2 plants was driven by the lower nitrogen and protein contents rather than by the higher carbohydrates contents in the leaves. Nevertheless, direct effects of elevated CO2 on the respiratory biochemistry cannot be excluded.Photosynthèse, activité Rubisco et oxydation mitochondriale du malate chez des semis de chêne pédonculé (Quercus robur L) élevés à des concentrations en CO2 atmosphérique actuelle et double. Des germinations de chêne pédonculé ont été élevées sous 350 et 700 μL/L de CO 2 en chambres de culture. Après 130 jours de CO2 élevé, la biomasse du plant entier n'a pas augmenté significativement. Les échanges foliaires de CO2, l'activité Rubisco, l'oxydation mitochondriale du malate, les teneurs de sucres et d'azote ont été étudiées sur des feuilles de la quatrième vague de croissance. À 700 μL/L de CO 2, le taux de photosynthèse nette foliaire augmente de 220 % par rapport à celui à 350 μL/L de CO2. La diminution de l'activité Rubisco est accompagnée d'une accumulation de saccharose et de glucose. La diminution de la capacité d'oxydation des mitochondries brutes de feuilles des plants sous CO2 élevé est reliée plutôt à la diminution des teneurs en azote et protéines qu'à l'augmentation de la teneur en sucres dans les feuilles. Néanmoins, les effets directs de l'élévation de CO2 sur la biochimie de la respiration ne sont pas exclus

Extraction and study of enzymes linked to malate metabolism in tree leaves

International audienc

Beech trees exposed to high CO₂ and to simulated summer ozone levels: Effects on photosynthesis, chloroplast components and leaf enzyme activity.

Young trees of European beech (Fagus sylvatica L.) were exposed in a phytotron to different levels of ozone and CO2 under the climatic simulation of one vegetation period. High ozone levels were simulated similar to high ozone concentration in the field (up to 110 ppb), while CO2 was added as 300 ppm to the present level of ca 380 ppm. Our study describes different aspects of photosynthesis from the leaf level to the reactions of selected thylakoid components at different harvest times during growth of the beech trees under the different fumigation regimes. Ozone effects appeared in the first weeks of the treatment as a stimulation of chlorophyll fluorescence (F-v/F-m), in oxygen production and in ribulose-1,5-bisphosphate carboxylase/oxygenase activity, while the summer and early autumn harvests showed strong reductions in these parameters. Only phosphoenolpyruvate carboxylase (PEPcase) activity remained higher under high ozone. The effects of high CO2 appeared in general as a small stimulation in enzyme activity like PEPcase in spring. However, with increasing time of fumigation, reductions of all parameters were observed. Especially chlorophylls showed strong reductions under high CO2. The combined treatment with high ozone plus high CO2 resulted mostly in an amelioration of the negative ozone effects, although control levels were not reached