首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
A continuous record of sedimentation in spring-fed fens makes them suitable for detailed palaeoenvironmental studies. A newly investigated cupola spring-fed fen (Paw?ów site), located in the Lublin chalkland, eastern Poland, was the object of our study. This special karst region is characterised by the occurrence of Upper Cretaceous carbonate rocks in the substratum. Sedimentological observations indicated strong variability of biogenic-carbonate series in the deposits (=peat-tufa rhythmite), reflects changes of accumulation conditions (oxidising versus reducing), resulting from alternate occurrence of warmer and cooler periods. Difficulties in pollen analysis due to oxidising conditions necessitate a multidisciplinary approach for palaeoenvironmental reconstruction. We used a multidisciplinary approach (sedimentological, palaeobotanical, geochemical analyses and radiocarbon dating) to determine the main evolutionary stages of this unique fen ecosystem and to discuss the role of local or/and regional factors in its development. Pollen and plant macrofossil analyses, supported by radiocarbon dating, proved that the bottom part of the cores represents the Late Glacial–Early Holocene stages of the fen development. A comparative analysis of palaeoenvironmental data showed close resemblance between the Paw?ów fen and the earlier studied fens in eastern Poland and Central-Eastern Europe, and the connection between their development and supraregional hydrological-climatic factors. The results indicated also the influence of the morphological position of such a type of ecosystem on the development of a continuous deposit succession. The occurrence of a river valley in close proximity of the Paw?ów site resulted in the lack of tufa deposits from the Atlantic period, because of an erosional phase in the river valley.  相似文献   

2.
3.
I. Kasprzyk 《Aerobiologia》2004,20(4):217-222
Airborne pollen of entomophilous plants occurred in low or very low concentrations, and constituted 4 of the total pollen sum. In 1997–2002, between 18 and 26 taxa were identified. Out of this large group the following taxa were represented in larger concentrations every year– Salix, Acer, Morus, Cichorioideae, Asterioideae, Plantago major/media, Sambucus nigra and Tilia. Microscopic examination revealed that pollen grains of the above mentioned species were often glued together, which is a typical adaptation to this kind of pollination. Club moss (Lycopodium spp.) and horsetail (Equisetum spp.) spores were recorded sporadically. Fern spores were found frequently but in very low numbers. In 2002 the occurrence of the airborne pollen of entomophilous plants in the city and in the countryside was compared. A higher percentage value of pollen was found in the atmosphere of the city rather than in the countryside, due to the high concentration of Acer pollen, which is a partly entomophilous species and common in municipal plantings. In the countryside air there was a higher concentration of pollen from purely entomophilous species, such as Viburnum and Asteroideae.  相似文献   

4.
High Pinaceae pollen concentrations in the air and on the surface of puddles before the main pollen season started were observed in Kraków (southern Poland) in May 2013. The paper presents the results of detailed studies of the composition and source of the “yellow rain” in 2013, and as a comparison, the Pinaceae pollen concentrations and samples collected from the ground surface in 2014 were considered. The air samples were collected using the volumetric method (Hirst-type device), while pollen grains sampled from the ground surface were processed using a modified Erdtman acetolysis method. Finally, all samples were studied using a light microscope. In 2013, the period of higher Abies, Picea and Pinus pollen concentrations was observed from the 5 to 12 of May, earlier than the main pollen season occurred. The presence of rainfall on the 12 and 13 of May 2013 caused the pollen deposition on the ground surface, where the prevalence of Pinaceae pollen was found. The synoptic situation and the analysis of the back-trajectories and air mass advection at the beginning of May 2013 indicated that Pinaceae pollen grains could have been transported from Ukraine, Romania, Hungary and Slovakia. In contrast, Pinaceae pollen grains deposited on the ground surface as a “yellow” film in May 2014, originated from local sources.  相似文献   

5.
Apoptosis: mitochondrial membrane permeabilization--the (w)hole story?   总被引:7,自引:0,他引:7  
One critical step of apoptosis is the release of mitochondrial proteins through the outer mitochondrial membrane. Recent work shows that two pro-apoptotic Bcl-2 family proteins, Bax and Bid, as well as the mitochondrion-specific lipid cardiolipin may cooperate in chemically defined liposomes to generate a protein-permeable conduit, relaunching the debate on the identity of the pore responsible for mitochondrial membrane permeabilization during apoptosis.  相似文献   

6.

Wetlands have declined in area and quality at an accelerating pace in the last 50 years. Yet, the last 50 years is when international attention has been focussed on wetlands through the Ramsar Convention. An analysis of how the convention has evolved over the past 50 years suggests it has been drifting away from its original mandate in a maladaptive manner, and this drift is a problem for achieving its original objectives. A review of the strategic plans of the convention revealed two key conditions for institutional drifting and the associated lack of success. The first condition lies in its unique situation as a non-UN convention, which reduces the convention’s visibility and interactivity with other biodiversity-related conventions, agencies, or programmes. The second condition is an increasing number of conventions dealing with biodiversity issues, all forcing the Ramsar Convention to seek different roles in an increasingly competitive institutional landscape. A more effective future for the convention arguably lies in reasserting its original mandate, but with cognisance of the changed environmental pressures of the twenty-first century. While this would narrow its increasingly broad focus, such a reorientation will allow wetlands and waterfowl to start a track to recovery, backed by active and focused Contracting Parties in a renewed international convention on wetland conservation, management, and sustainable use.

  相似文献   

7.
The aim of the study was to compare the courseof flowering and the occurrence of Alnus,Corylus and Betula pollen grains inthe air in 1999–2001. In 2000 and 2001 birchesflowered in a typical way – the floweringperiod was short and intense and that periodhad the highest concentration of pollen. Bothyears had no rainfall then and the temperaturewas high, which caused intense flowering ofbirches over a large area. In 1999 and 2000most of the Alnus and Coryluspollen was recorded at the end or after theirflowering period. At that time the weather wasunstable (as is usual in February and March).Pollen must have been transported fromelsewhere. Wind analysis showed that the mainsources of Corylus pollen must have beenin the south, and of Alnus in the southand west. In the southern margin of Poland thevegetative period begins later due to a colderclimate.  相似文献   

8.
Song Y  Li Z 《ZooKeys》2012,(168):13-17
A new species, Zyginella menghaiensissp. n. (Hemiptera: Cicadellidae: Typhlocybinae: Zyginellini), is described from Chinaand a key to species of Zyginella from China is provided.  相似文献   

9.
Derivatives of ethanologenic Escherichia coli K011 were constructed for D: (-)-lactate production by deleting genes encoding competing pathways followed by metabolic evolution, a growth-based selection for mutants with improved performance. Resulting strains, SZ132 and SZ186, contain native genes for sucrose utilization. No foreign genes are present in SZ186. Strain SZ132 also contains a chromosomally integrated endoglucanase gene (Erwinia chrysanthemi celY). Strain SZ132 produced over 1 mol lactate per liter of complex medium containing 10% (w/v) sugar (fermentation times of 48 h for glucose, 120 h for sucrose). Both strains produced 667-700 mmol lactate per liter of mineral salts medium. Yields for metabolized sugar ranged from 88% to 95% in both media.  相似文献   

10.
11.
A critical and annotated catalogue of 183 types of Hymenoptera Chrysididae belonging to 124 taxa housed in the Radoszkowski collection is given. Radoszkowski type material from other institutes has also been checked. Six lectotypes are designated in Kraków (ISEA-PAN): Chrysis acceptabilis Radoszkowski, 1891; Chrysis persica Radoczkowsky, 1881; Chrysis daphnis Mocsáry, 1889; Chrysis lagodechii Radoszkowski, 1889; Chrysis remota Mocsáry, 1889 and Chrysis vagans Radoszkowski, 1877. The lectotype of Brugmoia pellucida Radoszkowski, 1877 is designated in Moscow (MMU). Four new combinations are proposed: Philoctetes araraticus (Radoszkowski, 1890), comb. n.; Pseudomalus hypocrita (du Buysson, 1893), comb. n.; Chrysis eldari (Radoszkowski, 1893), comb. n.; and Chrysura mlokosewitzi (Radoszkowski, 1889), comb. n.. Ten new synonyms are given: Chrysis auropunctata Mocsáry, 1889, syn. n. of Chrysis angolensis Radoszkovsky, 1881; Chrysis chrysochlora Mocsáry, 1889, syn. n. and Chrysis viridans Radoszkowski, 1891, syn. n. of Chrysis keriensis Radoszkowski, 1887; Chrysis angustifrons var. ignicollis Trautmann, 1926, syn. n. of Chrysis eldari (Radoszkowski, 1893); Chrysis maracandensis var. simulatrix Radoszkowski, 1891, syn. n. of Chrysis maracandensis Radoszkowski, 1877; Chrysis pulchra Radoszkovsky, 1880, syn. n. of Spinolia dallatorreana (Mocsáry, 1896); Chrysis rubricollis du Buysson, 1900, syn. n. of Chrysis eldari (Radoszkowski, 1893); Chrysis subcoerulea Radoszkowski, 1891, syn. n. of Chrysis chlorochrysa Mocsáry, 1889; Chrysis therates Mocsáry, 1889, syn. n. of Chrysis principalis Smith, 1874; and Notozus komarowi Radoszkowski, 1893, syn. n. of Elampus obesus (Mocsáry, 1890). One species is revaluated: Chrysis chalcochrysa Mocsáry, 1887. Chrysis kizilkumiana Rosa is the new name for Chrysis uljanini Radoszkowski & Mocsáry, 1889 nec Radoszkowski, 1877. Pictures of seventy-seven type specimens are given.  相似文献   

12.
Oak (Quercus petraea Liebl.) and larch (Larix decidua Mill.) forest plantations of the study area Mlodzawy in Poland were analysed. Changes in the syntaxonomic composition and of Ellenberg's indices (light, continentality, moisture, reaction and nitrogen index) were determinated. The results obtained mostly conform to the assumption that the herb layer of both plantations becomes, gradually with tree growth, more similar to each other and to that of mature oak-hornbeam forests. Such statement is justified by: an increase in the share of species common to both plantation types, a significant increase in the number and cover of the Querco-Fagetea character-species, accompanied by a decrease in the number and cover of other character-species, a general decrease in the share of species with extreme climatic and edaphic requirements, accompanied by a gradual increase in the share of number and cover of species with average demands. From the studies it may be concluded that the developmental mechanisms w which determine the direction and trends of changes in the herb layer are mainly common to both plantation types, whereas tree stand species, in spite of different habit, ecological demands, and effect on soil properties, have only slight modification influence.  相似文献   

13.
The Upper Jurassic complex of Zegarowe Rocks is situated on the Kraków–Wieluń Upland in southern Poland. The complex is dominated by massive limestones representing carbonate buildups. The successive stages of carbonate buildup development include: colonisation, aggradational growth and progradation phases. In the colonisation phase, on top of loose peloidal-ooid sands micritic peloidal thrombolites developed. Peloidal and agglutinated thrombolites and stromatolites proliferated during the aggradational growth phase, whereas the progradation phase was characterised by shallowing and related development of agglutinated stromatolites with coprolites. The latter were the effect of periodical stabilisation of detrital sediments by microbial mats. The Zegarowe Rocks complex developed upon an elevation of the Late Jurassic stable northern shelf of the Tethys. This elevation was formed due to local decrease in subsidence rate, induced by the presence of a Palaeozoic granitoid intrusion in the shelf substratum. The carbonate buildups of the Zegarowe Rocks complex, initially developing as sediment-starved mounds upon fault-controlled intraplatform highs under strongly restricted background sedimentation rate, were replaced by agglutinated microbial reefs.  相似文献   

14.
Boron is an essential nutrient for plants, but it is toxic in excess. Transgenic rice plants expressing an Arabidopsis thaliana borate efflux transporter gene, AtBOR4, at a low level exhibited increased tolerance to excess boron. Those lines with high levels of expression exhibited reduced growth. These findings suggest a potential of the borate transporter BOR4 for the generation of high-boron tolerant rice.  相似文献   

15.
16.
(S)-(?)-Vertinolide 1 was synthesized via the tetronic acid derivative 6 from (S)-(?)-tetrahydro-2-methyl-5-oxo-2-furancarboxylic acid 3. (±)-Vertinolide was also synthesized from (±)-3.  相似文献   

17.
It has become a widespread practice to convert δ(18)O(p) values measured in human and animal dental enamel to a corresponding value of δ(18)O(w) and compare these data with mapped δ(18)O(w) groundwater or meteoric water values to locate the region where the owner of the tooth lived during the formation of the enamel. Because this is a regression procedure, the errors associated with the predicted δ(18)O(w) values will depend critically on the correlation between the comparative data used to perform the regression. By comparing four widely used regression equations we demonstrate that the smallest 95% error is likely to be greater than ±1% in δ(18)O(w) , and could be as large as ±3.5%. These values are significantly higher than those quoted in some of the recent literature, and measurements with errors at the higher end of this range would render many of the published geographical attributions statistically unsupportable. We suggest that the simplest solution to this situation is to make geographical attributions based on the direct comparison of measured values of δ(18)O(p) rather than on predicted values of δ(18)O(w).  相似文献   

18.
The synthesis of (±)-licarin-B, a neolignan of Licaria aritu Ducke (Lauraceae), was achieved by pyrolysis of 3-hydroxy-3-piperonyl-1-propyl-2-methoxy-4-(E)-propenylphenyl ethers.  相似文献   

19.
The synthesis of (–)-muricatacin starting from 1-bromododecane and 2-pentyn-l-ol is described. 2-Pentadecyn-1-ol (4), which was prepared from 1-bromododecane (2) and 2-pentyn-1-ol (3), was converted to epoxy alcohol 6 through a two-step reaction sequence, 6 being successively submitted to tosylation, iodination, chain extension with tert-butyl lithioacetate, and acid-catalyzed cyclization to give (–)-muricatacin (1a). Recrystallization afforded optically pure 1a.  相似文献   

20.
The aim of this study was to register the zooplanktonic organisms in water bodies in the Zoological Garden in Kraków, especially from a point of view of the occurrence of species of the Paramecium aurelia complex. Only P. caudatum was found in one habitat, in several sampling places. The species seems very resistant and can survive in poor or polluted habitats in which the P. aurelia ssp. are eliminated.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号