Interspecific differences in photosynthetic efficiency and spectral reflectance in two Umbilicaria species from Svalbard during controlled desiccation

This study aimed to evaluate the effective photosynthetic quantum yield ( Phi PSII) and the Photochemical Reflectance Index (PRI) for assessment of photosynthetic performance of two Umbilicaria lichens during gradual desiccation of their thalli. U. cylindrica and U. decussata exhibited curvilinear relationship (S-shape curve) of decreasing Phi PSII values with decreasing water potential (WP) of thalli. During initial phase of desiccation (WP from 0 to -10 MPa), no decrease of Phi PSII was apparent, further desiccation (WP from -10 to -20 MPa) led to fast Phi PSII decrease from 0.6 to 0.1 indicating strong inhibition of photosynthetic processes. Critical WP at which photosythetic processes are fully inhibited was found bellow -25 MPa in both lichen species. Photochemical Reflectance Index (PRI) exhibited curvilinear increase with thalli desiccation (decreasing WP). At full thallus hydration, the PRI reached the value of -0.18 in both species. Under strong dehydration (WP from -20 to -30 MPa), however, U. cylindrica showed somewhat lower value (-0.04) than U.decussata (-0.02 MPa). PRI to WP relationship is discussed and compared to existing evidence from higher plants and poikilohydric organisms.Tato publikace je zaměřena na souběžné sledování indexu PRI a efektivního kvantového výtěžku fyotoyntézy během vysychání stélek dvou druhů lišejníků rodu Umbilicaria ze souostroví Špicberky (Svalbard). Byl zjištěno, že PRI s postupujícím vysycháním roste, zatímco u listů vyšších rostlin klesá.This study aimed to evaluate the effective photosynthetic quantum yield (Phi PSII) and the Photochemical Reflectance Index (PRI) for assessment of photosynthetic performance of two Umbilicaria lichens during gradual desiccation of their thalli. U. cylindrica and U. decussata exhibited curvilinear relationship (S-shape curve) of decreasing Phi PSII values with decreasing water potential (WP) of thalli. During initial phase of desiccation (WP from 0 to -10 MPa), no decrease of Phi PSII was apparent, further desiccation (WP from -10 to -20 MPa) led to fast Phi PSII decrease from 0.6 to 0.1 indicating strong inhibition of photosynthetic processes. Critical WP at which photosythetic processes are fully inhibited was found bellow -25 MPa in both lichen species. Photochemical Reflectance Index (PRI) exhibited curvilinear increase with thalli desiccation (decreasing WP). At full thallus hydration, the PRI reached the value of -0.18 in both species. Under strong dehydration (WP from -20 to -30 MPa), however, U. cylindrica showed somewhat lower value (-0.04) than U.decussata (-0.02 MPa). PRI to WP relationship is discussed and compared to existing evidence from higher plants and poikilohydric organisms

Interspecific differences in photosynthetic efficiency and spectral reflectance in two Umbilicaria species from Svalbard during controlled desiccation

This study aimed to evaluate the effective photosynthetic quantum yield (FPSII) and the Photochemical Reflectance Index (PRI) for assessment of photosynthetic performance of two Umbilicaria lichens during gradual desiccation of their thalli. U. cylindrica andU. decussata exhibited curvilinear relationship (S-shape curve) of decreasing FPSII values with decreasing water potential (WP) of thalli. During initial phase of desiccation (WP from 0 to -10 MPa), no decrease of FPSII was apparent, further desiccation (WP from -10 to -20 MPa) led to fast FPSII decrease from 0.6 to 0.1 indicating strong inhibition of photosynthetic processes. Critical WP at which photosythetic processes are fully inhibited was found bellow -25 MPa in both lichen species. Photochemical Reflectance Index (PRI) exhibited curvilinear increase with thalli desiccation (decreasing WP). At full thallus hydration, the PRI reached the value of -0.18 in both species. Under strong dehydration (WP from -20 to -30 MPa), however, U. cylindrica showed somewhat lower value (-0.04) than U.decussata (-0.02 MPa). PRI to WP relationship is discussed and compared to existing evidence from higher plants and poikilohydric organisms

An improved method for the visualization of conductive vessels in Arabidopsis thaliana inflorescence stems

Dye perfusion is commonly used for the identification of conductive elements important for the study of xylem development as well as precise hydraulic estimations. The tiny size of inflorescence stems, the small amount of vessels in close arrangement, and high hydraulic resistivity delimit the use of the method for quantification of the water conductivity of Arabidopsis thaliana, one of the recently most extensively used plant models. Here, we present an extensive adjustment to the method in order to reliably identify individual functional (conductive) vessels. Segments of inflorescence stems were sealed in silicone tubes to prevent damage and perfused with a dye solution. Our results showed that dyes often used for staining functional xylem elements (safranin, fuchsine, toluidine blue) failed with Arabidopsis. In contrast, Fluorescent Brightener 28 dye solution perfused through segments stained secondary cell walls of functional vessels, which were clearly distinguishable in native cross sections. When compared to identification based on the degree of development of secondary cell walls, identification with the help of dye perfusion revealed a significantly lower number of functional vessels and values of theoretical hydraulic conductivity. We found that lignified but not yet functional vessels form a substantial portion of the xylem in apical and basal segments of Arabidopsis and, thus, significantly affect the analyzed functional parameters of xylem. The presented methodology enables reliable identification of individual functional vessels, allowing thus estimations of hydraulic conductivities to be improved, size distributions and vessel diameters to be refined, and data variability generally to be reduced

Preparation and modification of carboxylate-substituted metal oxo clusters

Anorganisch-organische Hybridmaterialien, in denen anorganische und organische Bestandsteile kovalent miteinander verbunden sind, zweite Klasse von Hybridmaterialien, stellen eine interessante Klasse von Materialien dar, mit sehr breiten Eigenschaften und Anwendungen. Durch die Verwendung von organisch modifizierten Metallalkoxiden, die an ihre Oberfläche polymerisierbare Liganden erhalten, lassen sich Hybridmaterialien herstellen.Im ersten Teil dieser Arbeit wurden organisch modifizierte Übergangsmetallcluster durch die Reaktion der entsprechenden Alkoxide mit Carbonsäuren hergestellt. Die Reaktion von Gemischen aus Titan und Yttriumalkoxiden mit Methacrylsäure führt zur Bildung von Mischcluster unterschiedlicher Zusammensetzung. Die Reaktion von Zr(OBu)4 mit Propion-, Essig- und Dimethylacrylsäure führte zur Bildung von Zirconium Oxo Clustern mit entsprechenden Liganden durch. In gleicher Form und Größe wie bei Zirconium Oxo Clustern wurde der Hafnium Oxo Cluster in der Reaktion von Hf(OBu)4 mit Essigsäure gebildet.Im zweiten Teil dieser Arbeit wurde versucht die polymerisierbaren Liganden an Metall Oxo Clustern zu reduzieren. Das wurde sowohl bei Hydrosilylierungsreaktionen als auch beim Austausch von an die Oberfläche gebundenen Liganden gegen andere Säuren untersucht. Abhängig vom molaren Verhältnis zwischen Clustern und freien Carbonsäuren wurden gemischte Oxo Cluster mit funktionalen und nicht-funktionalen Säuren erhalten. Durch Radikalcopolymerisation der Hafnium/Titan Cluster mit Methylmethacrylaten als organisches Monomer, wurden anorganisch-organische Hybridmaterialien hergestellt. Es wurden die thermische und mechanische Eigenschaften dieser Polymere untersucht.Inorganic-organic hybrid materials, in which the inorganic and organic part are connected by a covalent linkage, class II of hybrid materials, are an interesting class of materials with many possibilities, interesting properties and applications. In this work, metal oxide clusters substituted by polymerizable groups were investigated. Such clusters can be used as co-monomers in polymerization reactions. In the first part organically modified transition metal oxo clusters were prepared by reaction of metal alkoxides with functional and non-functional carboxylic acids. Upon reaction of titanium propoxide and yttrium 2-methoxyethoxide with methacrylic acid, three different mixed-metal clusters were obtained, depending on the titanium to yttrium alkoxide ratio: Ti4Y2O4(OMc)14(MeOCH2CH2OH)2, (OMc = methacrylate), Ti4Y2O4(OMc)14(MeOH)2 and Ti4Y2O4(OMc)12(OCH2CH2OMe)2(McOH)2. Reaction of mixtures of titanium propoxide and hafnium butoxide with methacrylic acid resulted in the formation of the mixed-metal cluster Hf4Ti4O6(OPr)4(OMc)16. Zr12O8(OH)8(OProp)24, (OProp = propionate), Zr12O8(OH)8(OAc)24 or Hf12O8(OH)8(OAc)24, (OAc = acetate), were prepared by the reaction of either zirconium butoxide or hafnium butoxide with propionic acid or acetic acid. Zr12O8(OH)8(OAcrMe2)24, (OAcrMe2 = dimethylacrylate), was prepared by the reaction of zirconium butoxide with dimethylacrylic acid. In the second part of the work, attempts were made to reduce the number of polymerizable ligands of metal oxo-clusters. This was tested by either hydrosilylation reaction of methacrylate-substituted cluster or by exchange of surface bonded ligands for other carboxylates. Depending on the molar ratio of clusters and carboxylic acid, oxo clusters with both functional and non-functional carboxylic acids were obtained, for example Zr6O4(OH)4(OMc)6(OIsob)6 or Zr6O4(OH)4(OMc)7(OOCEt)5.Free radical-iniciated polymerisation of Hf4Ti4O6(OPr)4(OMc)16 with methyl methacrylate, resulted in cluster-crosslinked hybrid materials.Both thermal stability and mechanical properties of the polymers were improved by the crosslinking.9

Die nicht-alkoholische Fettlebererkrankung : Die Rolle der Leber im metabolischen Syndrom

Epidemiologie Die nicht-alkoholische Fettlebererkrankung (»non-alcoholic fatty liver disease«, NAFLD) ist mittlerweile eine der häufigsten Lebererkrankung weltweit mit einer mittleren Prävalenz von 20% weltweit und bis zu 30% in Europa [1]. Als Hauptrisikofaktoren gelten einerseits verschiedene Umweltfaktoren, insbesondere Bewegungsmangel und falsche Ernährung sowie andererseits die verschiedenen Aspekte des metabolischen Syndroms: Adipositas, Fettstoffwechselstörungen sowie Insulinresistenz und Diabetes mellitus Typ 2. Aus diesem Grund wird die Fettleber mittlerweile auch als hepatische Komponente des metabolischen Syndroms bezeichnet. Neben den Umweltfaktoren konnte auch gezeigt werden, dass eine genetische Prädisposition im Sinne von einem Adiponutrin Polymorphismus (»patatin-like phospholipase domain containing 3«, PNPLA3 [2, 3] zu einem gehäuften Auftreten einer Fettlebererkrankung führen kann

Trunk radial growth, water and carbon relations of mature apple trees on two size-controlling rootstocks during severe summer drought

The use of size-controlling rootstocks is central to modern high-density fruit production systems. While biological mechanisms responsible for vigor control are not fully understood, differences in water relations and carbohydrate storage ability have been suggested as two potential factors. To better understand the processes that control growth vigor, we analyzed the trunk radial variation at seasonal and diurnal timescales and measured the midday leaf water potential (ΨMD), leaf gas exchange and concentrations of non-structural carbohydrates (NSC) in apple trees of variety ‘Jonagold’ grafted on two rootstocks of contrasting growth vigor (dwarfing J-TE-G vs invigorating J-TE-H). The measurements were conducted during an exceptionally hot and dry summer. We found that smaller annual trunk radial increments in dwarfed trees were primarily due to an earlier cessation of trunk secondary growth. The interdiurnal trunk circumference changes (ΔC) were slightly lower in dwarfed trees, and these trees also had fewer days with positive ΔC values, particularly during the driest summer months. The trunks of dwarfed trees shrank gradually during the drought, showed less pronounced diurnal variation of trunk circumference and the maximum trunk daily shrinkage was only weakly responsive to the vapor pressure deficit. These results indicated that lower turgidity in the cambial region may have limited the trunk radial expansion in dwarfed trees during the hot and dry days. Dwarfed trees also maintained lower ΨMD and leaf gas exchange rates during the summer drought. These parameters decreased in parallel for both rootstock combinations, suggesting their similar drought sensitivity. Similar concentrations and seasonal dynamics of NSC in both rootstock combinations, together with their similar spring growth rates, suggest that NSC reserves were not directly limiting for growth. Our results support the prominent role of water relations in rootstock-induced size-controlling mechanisms and highlight the complexity of this topic

Can the clusters Zr6O4(OH)4(OOCR)12 and [Zr6O4(OH)4(OOCR)12]2 be converted into each other?

Upon reaction of zirconium alkoxides, Zr(OR)4, with carboxylic acids, the clusters Zr6O4(OH)4(OOCR)12 (Zr6) or [Zr6O4(OH)4(OOCR)12]2 (Zr12) were obtained, depending on the employed carboxylic acid. The structures of Zr12 clusters with acetate, propionate, vinyl acetate or 3,3\u2032-dimethylacrylate ligands were determined by single-crystal X-ray diffraction, as well as that of methacrylate/acetate and methacrylate/propionate mixed-ligand clusters. The structure of the hafnium cluster [Hf6O4(OH)4(acetate)12]2 is also reported for comparison. The Zr12 clusters are structurally related to the Zr6 clusters since they are composed of two Zr6 sub-units which are bridged by four carboxylate ligands. In each compound, carboxylic acid molecules interact with the cluster by hydrogen bonding to part of the \u3bc3-OH ligands. The clusters are highly dynamic in solution, due to site exchange of the carboxylate ligands; low-temperature NMR spectra of the clusters correspond to the solid-state structures. The Zr6 and Zr12 clusters can be clearly distinguished by their solution NMR spectra. Reactions between selected Zr12 clusters and carboxylic acids led to the conclusion, that only part of the ligands is accessible for ligand exchange reactions. In contrast, all ligands were exchanged when the Zr6 cluster Zr6O4(OH)4(methacrylate)12 was treated with an excess of propionic acid, and Zr6O4(OH)4(propionate)12 was formed. However, the Zr12 cluster [Zr6O4(OH)4(propionate)12]2 was obtained from the reaction of Zr(OBu)4 with propionic acid. The Zr6 and Zr12 clusters thus do not interconvert at the given reaction conditions. (\ua9 Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006