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1.
Božena Šerá 《Biologia》2008,63(6):1085-1088
Road nets are man-made constructions in the open landscape with a specific vegetation accompaniment in a verge or band along the road or in a divider strip. A determination of six basic vegetation types of bands along roads is possible in Central Europe (tree lines, planting area, forest stand, early successful growth, bushes band, grassy-herbal associations). In the Czech Republic, grassy-herbal communities growing on road verges are mainly formed by perennials, hemicryptophyts, and species with tendency towards pollination by insects and to anemochory and exozoochory. 40% woody and 25% herbaceous species which are non-native for Central Europe form a part of them. Three halophyte species are growing in closed lines along asphalt: Puccinellia distans, Digitaria sanguinalis and Spergularia rubra. Roads and highways should be made and used with respect to the ecological potential of roadside vegetation. However, the road net functioned as a corridor for invasive (planting or spreading) plant species.  相似文献   

2.
The taxonomic position of a fossil recently found in Givetian strata of the Eifel Mountains, Germany, is discussed. It is a member of the Mollusca, but it is uncertain if it should be assigned to the Cephalopoda or the Scaphopoda. Both possibilities can be supported by the preserved morphology of the specimen. Without additional material the question of higher taxonomic assignment remains unsolved.  相似文献   

3.
An interesting example of interference in the arginase assay is presented. This can be exploited to convey the importance of taking precautions and appropriate controls to the students of enzymology.  相似文献   

4.
The role of calcium in chloroplasts—an intriguing and unresolved puzzle   总被引:1,自引:0,他引:1  
Rocha AG  Vothknecht UC 《Protoplasma》2012,249(4):957-966
More than 70?years of studies have indicated that chloroplasts contain a significant amount of calcium, are a potential storage compartment for this ion, and might themselves be prone to calcium regulation. Many of these studies have been performed on the photosynthetic light reaction as well as CO(2) fixation via the Calvin-Benson-Bassham cycle, and they showed that calcium is required in several steps of these processes. Further studies have indicated that calcium is involved in other chloroplast functions that are not directly related to photosynthesis and that there is a calcium-dependent regulation similar to cytoplasmic calcium signal transduction. Nevertheless, the precise role that calcium has as a functional and regulatory component of chloroplast processes remains enigmatic. Calcium concentrations in different chloroplast subcompartments have been measured, but the extent and direction of intra-plastidal calcium fluxes or calcium transport into and from the cytosol are not yet very well understood. In this review we want to give an overview over the current knowledge on the relationship between chloroplasts and calcium and discuss questions that need to be addressed in future research.  相似文献   

5.
The International Journal of Life Cycle Assessment - Mining of raw materials have both positive (e.g., creation of values and jobs along their supply chains and the supply chains they enter) and...  相似文献   

6.

Background  

During the last few years, DNA sequence analysis has become one of the primary means of taxonomic identification of species, particularly so for species that are minute or otherwise lack distinct, readily obtainable morphological characters. Although the number of sequences available for comparison in public databases such as GenBank increases exponentially, only a minuscule fraction of all organisms have been sequenced, leaving taxon sampling a momentous problem for sequence-based taxonomic identification. When querying GenBank with a set of unidentified sequences, a considerable proportion typically lack fully identified matches, forming an ever-mounting pile of sequences that the researcher will have to monitor manually in the hope that new, clarifying sequences have been submitted by other researchers. To alleviate these concerns, a project to automatically monitor select unidentified sequences in GenBank for taxonomic progress through repeated local BLAST searches was initiated. Mycorrhizal fungi – a field where species identification often is prohibitively complex – and the much usedITSlocus were chosen as test bed.  相似文献   

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The development of the shoot and the roots exhibits a dynamic balance that is characteristic of the plant and the local conditions. Consideration of all aspects of these organ relations, including plant regeneration, suggest that information about organ size, performance and developmental rates is communicated over considerable distances. The movement of substrates, sucrose and essential ions, could not suffice to account for common situations in which they originate in storage tissues, nor for the essential correlation between organ development and vascular differentiation. More generally, the temporal and spatial separation of developmental processes on the one hand and mature functions on the other means that the information exchanged must include the potential for future and not only immediate function. In contrast to substrates, special signals could be selected to depend on development and to elicit varied responses throughout the plant. An example is the concrete evidence that auxin originates in shoot tissues and is essential for root initiation. Further, this same auxin can influence and thus integrate different processes throughout the plant. Mature organs and tissues participate in auxin relations and influence development, with the result that responses to auxin are in the context of the organs present on the plant and missing structures are added as needed. The acquisition of essential substrates feeds back to hormones by limiting development and influencing auxin distribution. A possibility that requires further study is whether feedback could also be due to direct coupling between functional performance and auxin relations. In more general terms, the discussion demonstrates the importance of the mechanisms that integrate plant development and ways they could mask mutant expression.  相似文献   

9.
Alcoholism has complex etiology and there is evidence for both genetic and environmental factors in its pathophysiology. Chronic, long-term alcohol abuse and alcohol dependence are associated with neuronal loss with the prefrontal cortex being particularly susceptible to neurotoxic damage. This brain region is involved in the development and persistence of alcohol addiction and neurotoxic damage is likely to exacerbate the reinforcing effects of alcohol and may hinder treatment. Understanding the mechanism of alcohol’s neurotoxic effects on the brain and the genetic risk factors associated with alcohol abuse are the focus of current research. Because of its well-established role in neurodegenerative and neuropsychological disorders, and its emerging role in the pathophysiology of addiction, here we review the genetic and epigenetic factors involved in regulating α-synuclein expression and its potential role in the pathophysiology of chronic alcohol abuse. Elucidation of the mechanisms of α-synuclein regulation may prove beneficial in understanding the role of this key synaptic protein in disease and its potential for therapeutic modulation in the treatment of substance use disorders as well as other neurodegenerative diseases.  相似文献   

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A new cheiracanthid acanthodian species, Cheiracanthus flabellicostatus sp. nov., is described based on scales found in the beds of the Aruküla Regional Stage of Siverskiy and Zaitsevo localities of the Leningrad Region. It is distinguished from other members of the genus in the presence of a V-shaped eminence in the medial part of the scale crown and 8–10 large ribs branching into smaller ribs in the anterior part of the crown; large lacunas are observed at crossings of circular and ascending canals in the middle part of the scale neck.  相似文献   

12.
An α-carbonic anhydrase (CA, EC 4.2.1.1) isolated from the living fossil sponge Astrosclera willeyana, Astrosclerin, was investigated for its inhibition profile with simple inorganic anions, complex anions and other small molecules known to interact with these zinc enzymes. Astrosclerin is a catalytically highly efficient enzyme, and is inhibited in the low micromolar range by sulfamide, sulfamic acid, phenylboronic acid and phenylarsonic acid, and in the submillimolar range by a variety of anions including fluoride, chloride, cyanate, thiocyanate, cyanide, hydrogen sulfide, bisulfate, stannate, perosmate, divanadate, perrhenate, perruthenate, selenocyanide, trithiocarbonate, diethyldithiocarbamate and iminodisulfonate. Less efficient Astrosclerin inhibitors were sulfate, bromide, iodide, azide, bicarbonate, carbonate, tetraborate and perchlorate (K(I)s of 5.11-30.6mM) whereas tetrafluoroborate was not at all inhibitory. Because Astrosclerin is involved in calcification processes in vivo, its anion inhibition profile may be important for future studies designed to shed light on the physiologic functions of α-CAs in marine organisms.  相似文献   

13.
Summary Recent investigations into the role of peroxisomes in mammalian lipid metabolism have employed double isotope methodologies to examine the influence of peroxisomal agents on lipid turnover in the liver and extra hepatic tissues of the living animal.The action of these agents, all of which caused extensive changes in the flux of lipid metabolism in the treated animals, may best be viewed in relation to their effects on the common pathway of fatty acid oxidation in peroxisomes.Clofibrate, for example, acts through induction of peroxisomal oxidases and catalase; glycolate and ethanol through activation of this pathway; and aminotriazole and allylisopropylacetamide through inhibition of the catalase step in the sequence.The data from these studies provide support for the concept of an important contributory and regulatory role of peroxisomes in relation to the overall balance of lipid metabolism, and emphasize that these organelles play a significant role in the oxidation of common fatty acids, as well as a potential for the elimination of fatty acids that are poorly oxidized by mitochondria.Additionally, the data raise intriguing questions on the extension of peroxisomal influence to include phospholipid metabolism and the substantial degree of inter-tissue communication which is involved in the balance of lipid metabolism in the whole animal.  相似文献   

14.
For centuries the alkaloids of coca leaves have sustained the natives of the Andes in their onerous existence, but only recently have the effects of this drug been clinically studied.  相似文献   

15.
《Palaeoworld》2020,29(1):75-87
Typical early Viséan foraminiferal assemblages documented in outcrops of the Western Meseta of Morocco led to the erroneous biostratigraphic dating of areas that later, after much effort, have been demonstrated to correspond to the mid and late Viséan. These sections are analyzed to decipher if they are formed by reworked specimens or if this fauna really survived into younger rocks. Key sections are located in vast areas of the Western Meseta, in the north of the Azrou-Khenifra basin, Fourhal area, El Hammam Ridge, Oulmès area, Sidi Bettache basin (all on the north of the Western Meseta), and the Skoura region (on the southern border). The environmental settings as well as the taphonomical stage of preservation of the foraminifers suggest that most of the assemblages are composed of autochthonous or parautochthonous foraminifers and, thus, that the fauna really survived into the middle and even upper Viséan carbonate platforms of the Western Meseta. In some sections, the early Viséan foraminifers share the same levels with mid Viséan foraminifers; in others, they share the same levels with mid and late Viséan foraminifers, and in a third group, the early Viséan foraminifers occur in the same stratigraphic sections with mid and late Viséan assemblages, although never in exactly the same stratigraphic levels but alternating. These distributions exemplify the three patterns of interaction between the stratigraphic and biogeographic ranges of the assemblages.The absence of similar patterns is noteworthy in the surrounding regions of the Palaeotethys, and thus, this anomalous distribution can be discarded as a matter of dispersal from neighbouring regions. The absence of similar patterns in basins situated far from the Western Meseta allows abiotic factors to be discarded, such as tectonic/environmental setting, palaeolatitude or isolation. The most plausible hypothesis to explain the survival of these fauna is related to biotic factors, such as species interaction and competition, and they can be compared to some similar modern ecological patterns. However, the primary triggering factor allowing these biotic factors to interact is considered to be the late arrival of the mid Viséan foraminifers to the Western Meseta, allowing them to occupy niches completely different from the rest of the Palaeotethys.  相似文献   

16.
Steel  J. A. 《Hydrobiologia》1997,349(1-3):27-37
Major aspects of algal modelling are defined.Prediction and explanation are suggested as mainobjectives. Examples of the development and use ofshort-term prediction and more general explanatoryalgal models for reservoirs are given. It is concludedthat good prediction and explanation are not likely tobe simultaneously achievable. Possible means ofassessing the capabilities of ecosystem models andmodelling are considered. Some suggestions as to howthe present situation may be coped with, and improved,are proposed.  相似文献   

17.
Ardiç-Mordo?an is a new fossil Mammal locality in the Karaburun Peninsula of Western Turkey. Among its fauna, which is described here, the carnivores are especially interesting, with the most complete specimens ever found ofPercrocuta miocenica and of a primitive species of hyaenid, of which a new subspecies is described,Protictitherium intermedium paralium. This fauna is strongly reminiscent of those of sever-al other Middle Miocene localities in this area, Çandir, Pa?alar and Inönü in Turkey, and Prebreza in Serbia, and they must all belong to the same mammalian zone. Their ungulates attest an open environment which must have been widespread in the Turko-Balkanic area in Serravallian times.  相似文献   

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A new genus and species Amplectosporangium jiangyouense, is described from the Pingyipu Formation (Siegenian) of the Lower Devonian in Jiangyou district, Sichuan, China. The plant consists of naked dichotomizing erect axes with terminal fertile branch-systems. Sporangia are oval-shaped each with a short stalk and are arranged along the inner side of dichotomized axes in single row. By comparison with other known Devonian plants the genus is considered to represent a new morphological type of early land plants. Based on the theory of the telomic origin of the ovular integument, the plant may represent an early stage in the evolution of integument.  相似文献   

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