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261.
262.
Cell saps from leaves, petioles and storage root of sugar beet plants were analysed to indicate the possible specific and/or non-specific (osmotic) function of K and Na ions for the regulation of assimilate partitioning in sugar beet. Plants were cultivated up to 94 days in nutrient solutions containing either 4.5 mol m?3 K + 0.5 mol m?3 Na (K plants) or 0.5 mol m?3 K + 4.5 mol m?3 Na (Na plants) or 0.5 mol m?3 K + 0.5 mol m?3 Na (control). Osmotic potentials of the cell sap of leaf blades (?1.4 to ?1.6 MPa) and petioles (?1.6 to ?2.0 MPa), respectively, were rather low and similar. It was concluded that in these organs Na may replace K in its osmoregulatory functions. While shoot growth was favoured by Na, a principally improved translocation of K into the taproot was noted. This was - especially in the K-treatment - associated with increased growth of the storage root and a simultaneously stimulated sucrose accumulation. The results are discussed in terms of a different compartmentation of K, Na and Cl within the cell and within the whole plant and of a specific role of potassium in the process of assimilate translocation and storage. 相似文献
263.
Michael Dannenmann Rainer Gasche Astrid Ledebuhr Thomas Holst Helmut Mayer Hans Papen 《European Journal of Forest Research》2007,126(2):331-346
The effect of forest management (thinning) on in situ carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) trace gas exchange between soil and atmosphere was studied in three consecutive years at three beech forest sites, which
differ in aspect [southwest (SW), northeast (NE), northwest (NW)]. At all sites adjacent thinning plots (“T”) and untreated
control plots (“C”) were established. Measurements at the SW and NE sites covered the years 4–6 after thinning while at the
NW site measurements covered the year before and the first 2 years after thinning. Mean N2O fluxes were <3 μg N2O–N m−2 h−1 at all plots except for the newly thinned NWT plot. CH4 uptake was rather low, too. Very low CH4 oxidation rates during dry periods are explained by physiological drought stress for CH4 oxidizers. Heterotrophic litter decomposition constitutes the largest part of total soil respiration. On the whole, no significant
positive or negative effects of the silvicultural treatment on the magnitude of CO2-, CH4- and N2O-trace gas exchange could be observed at the SW site 4–6 years after thinning. Also at the NE site, no effects of thinning
on CO2 and N2O fluxes could be demonstrated. However, at this site a significant moisture-induced lower CH4 uptake could be shown. At the NW site forest management led to a dramatic increase in N2O emissions in the first two summers after thinning and to distinct effects on CO2 emissions and CH4 uptake in the first year after the felling. The unambiguous effects of thinning at the NW site are mainly related to higher
C input by dead residues leading to enhanced mineralization activity, to a shift in the competition for nutrients favoring
microorganisms as compared to trees and to changes in the soil water availability at the thinned plot. Considering the data
obtained from the NE and SW site we expect that with the development of an understorey vegetation at the NW site the observed
effects on the magnitude of trace gas exchange due to thinning will continue to decline in the following years. Our results
implicate that it is indispensable to take account of the effects of forest management in order to accurately calculate trace
gas emission inventories for the investigated forest ecosystem in case thinning took place immediately before. 相似文献
264.
Sprague LD Schubert E Hotzel H Scharf S Sachse K 《Veterinary journal (London, England : 1997)》2009,181(3):274-279
Reports of canine chlamydiosis are infrequent, possibly because the pathogen is rarely considered to be a cause of disease in dogs. This report presents details of Chlamydophila psittaci infection in four bitches with recurrent keratoconjunctivitis, severe respiratory distress and reduced litter size (up to 50% stillborn or non-viable puppies) in a small dog-breeding facility in Germany. Cell culture and immunofluorescence examination of conjunctival, nasal and pharyngeal swabs revealed chlamydial inclusions. PCR and sequencing of ompA amplification products confirmed the presence of Cp. psittaci genotype C. The zoonotic potential of the pathogen was illustrated by evidence of disease in two children that lived on the premises with the infected dogs. There was circumstantial evidence to suggest infection of dogs and humans may have followed the introduction of two canaries and a parrot to the household. The persistent nature of the chlamydial infection suggests that dogs may be reservoirs of Cp. psittaci, but this putative role and whether or not dogs shed the pathogen require further investigation. 相似文献
265.
266.
Jens Frankowski Malte Dorow Jakob Juenger Melanie Reckordt Steffen Schulz Claus Ubl Helmut Winkler 《Fisheries Management and Ecology》2019,26(1):86-96
Migration patterns of 146 female silver eels on their way through fresh and brackish water stretches of the Warnow River into the Baltic Sea were studied using acoustic telemetry. The majority of eels (77%) regained their expected downstream migration behaviour after a median rehabilitation time of 2 days. Positive rheotactic behaviour was observed for 23% of tagged eels after release, probably influenced by experimental procedures. The observed silver eel escapement rate was 63%. Two migratory groups were classified by significantly different migratory speed, time of residence in brackish waters and biometric silvering characteristics. Although the classification of silvering stages is based on these measures, the proportions of these stages did not reflect the observed differences in migratory behaviour. In the context of a permanent silver eel descent in the freshwater part of the Warnow River, a permanent escapement was likewise occurring into the Baltic Sea. 相似文献
267.
Lothar Müller Uwe Schindler Helmut Rogasik 《Archives of Agronomy and Soil Science》2013,59(5):403-414
Adapting soil engaging operations to the soil moisture status may limit damage of the soil structure or degradation processes. This requires the quantification of soil trafficability in dependence on soil hydrological conditions. The aim was to test the relevance of topsoil parameters in relation to trafficability and to study their temporal variability during a springtime period. On different sites located in the holocene regions east of Berlin, soil moisture, density and strength parameters were analysed and related to the actual score of trafficability. The results show that those parameters being most suitable to characterise the trafficability in the field such as consistence and density, are easy and reliable to estimate on the basis on framework guidelines. Vehicle mobility and the risk of topsoil and subsoil structural damage are mainly influenced by the topsoil status of the upper 10 cm, in particular of the soil surface of cohesive soils. Trafficability state may be derived at least from two or more relevant consistency and density parameters. Trafficability states are autocorrelated in the time domain. One‐step‐ahead forecasting of trafficability is possible using autocorrelations and weather data. 相似文献