Dendroclimatology of arctic shrubs

Práce se věnuje vlivu klimatických charakteristik na mikroskopickou stavbu dřeva jalovce. Dendrochronologie jako metoda naráží v arktických oblastech na své limity. Právě v těchto oblastech je však nedostatečná síť klimatických a meteorologických stanic s dostatečně dlouhými řadami klimatických parametrů. V současnosti proto stoupá zájem o studium arktických keříků, které se mohou vyskytovat i za severní hranicí lesa. V údolí Gangasdalen v oblasti fjordu Jarfjord v severovýchodním Norsku bylo v polovině srpna roku 2014 odebráno 33 disků z keřů jalovce, na kterých byly mikroskopicky měřeny šířky letokruhů. Z 26 jedinců, které se podařilo křížově datovat, byla vytvořena hlavní chronologie. Na vybraných osmi vzorcích byly ve spolehlivém období chronologie měřeny pomocí programu WinCell anatomické charakteristiky dřeva a to jak pro celý letokruh, tak zvlášť pro jeho jarní a letní část. Jednalo se o plochu lumen, šířku buněčných stěn, počet buněk v letokruhu a šířku letokruhu či jeho částí. Bylo zjištěno, že šířka letokruhu nemusí mít vždy nutně nejvyšší závislost na klimatu a tedy nemusí být nejlepší klimatické proxy. Nejvyšších závislostí dosahoval počet buněk v letokruhu na letních teplotách, naopak nejnižší závislost na klimatu vykazovaly plochy lumen.Thesis focuses on the influence of climate on microscopic structure of anatomic features in juniper wood. Dendrochronology as a method reaches its limits in the Arctic regions. Insufficient network of meteorological stations providing sufficiently long series of climatical data is the reason of increasing interest in studying Arctic shrubs, which can occur even beyond the latitudal forrest line. Thirty-three discs from juniper shrubs were collected in Gangasdalen valley on the banks of Jarfjord fjord in the August 2014. The master chronology was developed from 26 cross-dated samples. Eight carefully chosen samples were used for microscopic measurement of wood anatomic features during the reliable period of the main chronology using WinCell Wood Cell Anatomy software. Lumen area, wall thickness, number of cells and tree ring (its part) width were measured for both whole ring, and for earlywod and latewood. It was found that ring width does not necessarily have the highest dependency on climate and therefore may not always be the best climatic proxy. The highest dependency reached the number of cells, which was generally positively correlated with summer temperatures. On the other hand, lumen area shows the lowest dependency on climate.Department of Physical Geography and GeoecologyKatedra fyzické geografie a geoekologiePřírodovědecká fakultaFaculty of Scienc

Influence of the external environment on the moisture spectrum of Norway spruce (Picea abies (L.) KARST.)

The fluctuation of relative humidity and temperature in the surrounding environments of wood products is an important parameter influencing their mechanical properties. The objective of this study was to investigate the complex relationship between the moisture content and mechanical properties of wood as a critical aspect in the design of durable and reliable structures. Over a period of 669 days, a simulated type of experiment was conducted, during which the moisture content and external temperature were continuously measured in a compact profile of Norway spruce (Picea abies (L.) KARST.). The data were processed using quadratic and cubic models to establish a predictive model. It was found that the quadratic models slightly outperformed the cubic models when considering time lags greater than six days. The final model demonstrated a significant improvement in explaining the variance of the dependent variable compared to the basic model. Based on these findings, it can be concluded that understanding the relationship between the moisture content and temperature of wood samples plays an important role in wood’s efficient use, particularly for timber constructions. This understanding is vital for accurately predicting the mechanical characteristics of wood, which, in turn, contributes to the development of more durable and reliable structures.Web of Science147art. no. 134

PTt history from kyanite-sillimanite migmatites and garnet-staurolite schists from the Bayankhongor area, Mongolia indicates suprasubduction switching from extension to compression during Rodinia assembly

The tectonometamorphic evolution of the peri-Siberian tract of the Central Asian Orogenic Belt is mainly characterized by Baikalian Late Proterozoic - Early Cambrian cycle related to amalgamation of Proterozoic oceanic and continent fragments to Siberain landmass. Here we present in-situ monazite geochronology linked to P−T modelling of micashischsts and migmatite gneisses at the northern part of the Precambrian Baydrag block (central Mongolia) previously considered as a part of Baikalian metamorphic belt. Garnet-sillimanite-kyanite gneiss records first burial to the sillimanite stability at ~725 °C and 6.5 kbar, followed by burial to the kyanite stability at ~650 °C and ~8 kbar. The garnet-staurolite schist records burial to the staurolite-stability at ~620 °C and 6 kbar, followed by a nearly isothermal burial to ~580 °C and 9 kbar. The monazite data yield a continuum of 207Pb-corrected 238U/206Pb dates of c. 926−768 Ma in the Grt−Sil−Ky gneiss, and c. 937−754 Ma in the Grt-St schist. Based on monazite textural positon and internal zoning, the time of prograde burial and peak under a thermal gradient of 28-32 °C/km is estimated at c. 870−890 Ma. It is not clear whether such high grade conditions prevailed until a phase of further burial under a geothermal gradient of 18-22 °C/km and dated at 800−820 Ma. Additionally, monazite with dates of c. 568−515 Ma occurs as whole grains or as rims with sharp boundaries on Grenvillean monazite in Grt-St schist testifying for minor Baikalian overprint. Metamorphic zircon rims with Th/U ratio ~0.01-0.06 in Grt−Sil−Ky gneiss with 877 ± 7 Ma age, together with lower intercepts of zircon discordia lines in both Grt-Sil-Ky gneiss and Grt-St schist further support the Tonian age of high grade metamorphism. The P−T and geochronology data show anticlockwise P−T evolution from c. 930 to 750 Ma which is interpreted as a result of thickening of suprasubduction extensional and hot edifice - probably of back arc or arc type. This kind of prograde metamorphism was so far described only on the northern part of the Tarim block and interpreted as a result of initiation of peri-Rodinian subduction of Mirovoi Ocean. Here, we further discuss geodynamic consequences of a unique discovery of Tonian metamorphism in term of tectonic switch related to initiation of peri-Rodinian oceanic subduction during supercontinent assembly followed by strong mechanical coupling potentially related to onset of Rodinia splitting

FAD binding, cobinamide binding and active site communication in the corrin reductase (CobR)

Adenosylcobalamin, the coenzyme form of vitamin B12, is one Nature's most complex coenzyme whose de novo biogenesis proceeds along either an anaerobic or aerobic metabolic pathway. The aerobic synthesis involves reduction of the centrally chelated cobalt metal ion of the corrin ring from Co(II) to Co(I) before adenosylation can take place. A corrin reductase (CobR) enzyme has been identified as the likely agent to catalyse this reduction of the metal ion. Herein, we reveal how Brucella melitensis CobR binds its coenzyme FAD (flavin dinucleotide) and we also show that the enzyme can bind a corrin substrate consistent with its role in reduction of the cobalt of the corrin ring. Stopped-flow kinetics and EPR reveal a mechanistic asymmetry in CobR dimer that provides a potential link between the two electron reduction by NADH to the single electron reduction of Co(II) to Co(I)

Characterisation of PduS, the pdu Metabolosome Corrin Reductase, and Evidence of Substructural Organisation within the Bacterial Microcompartment

PduS is a corrin reductase and is required for the reactivation of the cobalamin-dependent diol dehydratase. It is one component encoded within the large propanediol utilisation (pdu) operon, which is responsible for the catabolism of 1,2-propanediol within a self-assembled proteinaceous bacterial microcompartment. The enzyme is responsible for the reactivation of the cobalamin coenzyme required by the diol dehydratase. The gene for the cobalamin reductase from Citrobacter freundii (pduS) has been cloned to allow the protein to be overproduced recombinantly in E. coli with an N-terminal His-tag. Purified recombinant PduS is shown to be a flavoprotein with a non-covalently bound FMN that also contains two coupled [4Fe-4S] centres. It is an NADH-dependent flavin reductase that is able to mediate the one-electron reductions of cob(III)alamin to cob(II)alamin and cob(II)alamin to cob(I)alamin. The [4Fe-4S] centres are labile to oxygen and their presence affects the midpoint redox potential of flavin. Evidence is presented that PduS is able to bind cobalamin, which is inconsistent with the view that PduS is merely a flavin reductase. PduS is also shown to interact with one of the shell proteins of the metabolosome, PduT, which is also thought to contain an [Fe-S] cluster. PduS is shown to act as a corrin reductase and its interaction with a shell protein could allow for electron passage out of the bacterial microcompartment

Early cytokinin response proteins and phosphoproteins of Arabidopsis thaliana identified by proteome and phosphoproteome profiling

Cytokinins are plant hormones involved in regulation of diverse developmental and physiological processes in plants whose molecular mechanisms of action are being intensely researched. However, most rapid responses to cytokinin signals at the proteomic and phosphoproteomic levels are unknown. Early cytokinin responses were investigated through proteome-wide expression profiling based on image and mass spectrometric analysis of two-dimensionally separated proteins and phosphoproteins. The effects of 15 min treatments of 7-day-old Arabidopsis thaliana seedlings with four main cytokinins representing hydroxyisopentenyl, isopentenyl, aromatic, and urea-derived type cytokinins were compared to help elucidate their common and specific function(s) in regulating plant development. In proteome and phosphoproteome maps, significant differences were reproducibly observed for 53 and 31 protein spots, respectively. In these spots, 96 proteins were identified by matrix-assisted laser desorption/ionization time-of-flight/time-of-flight mass spectrometry (MALDI-TOF/TOF MS), providing a snapshot of early links in cytokinin-regulated signalling circuits and cellular processes, including light signalling and photosynthesis, nitrogen metabolism, the CLAVATA pathway, and protein and gene expression regulation, in accordance with previously described cytokinin functions. Furthermore, they indicate novel links between temperature and cytokinin signalling, and an involvement of calcium ions in cytokinin signalling. Most of the differentially regulated proteins and phosphoproteins are located in chloroplasts, suggesting an as yet uncharacterized direct signalling chain responsible for cytokinin action in chloroplasts. Finally, first insights into the degree of specificity of cytokinin receptors on phosphoproteomic effects were obtained from analyses of cytokinin action in a set of cytokinin receptor double mutants

Multiple low-temperature thermochronology constraints on exhumation of the Tatra Mountains: New implication for the complex evolution of the Western Carpathians in the Cenozoic

The tectonothermal evolution of the highest mountain range in the Carpathian arc—the Tatra Mountains— is investigated by zircon and apatite fission track and zircon (U-Th)/He (ZHe) dating methods in order to unravel the disputed exhumation and geodynamic processes in the Western Carpathians. Our data in combination with geological evidences reveal a complex Cenozoic history, with four major tectonothermal events: (i) a very low grade metamorphism of the crystalline basement at temperatures >240°C due to tectonic burial during the Eo-Alpine collision in the Late Cretaceous (~80 Ma); (ii) exhumation and cooling of the basement to temperatures 150°C after burial to 5–9 km depths by the Paleogene fore-arc basin; (iv) final exhumation of the segmented basement blocks during Oligocene-Miocene (32–11 Ma) owing to lateral extrusion of the North Pannonian plate and its collision with the European foreland. The spatial pattern of thermochronological data suggests asymmetric exhumation of the Tatra Mountains, beginning in the northwest at ~30–20 Ma with low cooling rates (~1–5°C/Ma) and propagating toward the major fault bounding the range in the south, where the youngest cooling ages (16–9 Ma) and fastest cooling rates (~10–20°C/Ma) are found. Our data prove that the Tatra Mountains shared Cenozoic evolution of other crystalline core mountains in the Western Carpathians. However, the Miocene ZHe ages suggest that the Tatra Mountains were buried to the greatest depths in the Paleogene-Early Miocene and experienced the greatest amount of Miocene exhumation

Nitrate concentrations evaluation in small streams of the Želivka river basin and analysis of catchments of these streams

Katedra fyzické geografie a geoekologieDepartment of Physical Geography and GeoecologyPřírodovědecká fakultaFaculty of Scienc