Publications
NIBIOs employees contribute to several hundred scientific articles and research reports every year. You can browse or search in our collection which contains references and links to these publications as well as other research and dissemination activities. The collection is continously updated with new and historical material.
2009
Abstract
No abstract has been registered
Abstract
Denitrification is a key ecosystem process which is essential to avoid massive enrichment of nitrate in surface and ground water. A rather narrow group of bacteria are able to carry out denitrification, and they are known to be sensitive to environmentally toxic pollutants like e.g. heavy metals. Since these microorganisms carry out a key ecosystem function, they are strong candidates for testing and monitoring environmental effects of toxic substances likely to reach the soil environment. We conducted a series of experiments where either a pure strain of a denitrifying bacterium (Paracoccus denitrificans) or intact soil microbial communities containing indigenous denitrifiers were subjected to different types of silver nanoparticles (average particle size 20 and 1 nm) at a wide range of concentrations. The results showed that the smallest particles were far more toxic than the larger ones on a mass basis and completely killed off denitrifying bacteria in vitro at concentrations as low as 100 ppb. When soil was present, this concentration had no effect on respiration and even the far more sensitive process of denitrification, measured as production of the gases NO, N2O and N2, was unaffected. Results from experiments that are under way will also be presented. Here threshold levels for inhibition of denitrification by P. denitrificans and intact microbial communities are established for the two types of silver nanoparticles and where toxicity is compared when expressed on a mass basis vs. a surface area basis. Also the sensitivity of the different steps in the denitrification process will be compared and related to corresponding data for dissolved metals. The perspectives for using denitrification impediment as a way to assess ecotoxicity at a functional level will be discussed.
Abstract
Silver nanoparticles constitute one of the most common nanomaterials used in consumer products today, and the volumes used are increasing dramatically. Silver is an element known for its acute toxicity to both prokaryotes and a range of aquatic organisms. While ecotoxicity studies on nano-sliver is being studied at species level for some aquatic organisms, corresponding studies on terrestrial organisms are lagging behind. Also, studies targeting functional endpoints rather than purely physiological aspects are lacking. We have compared two types of nano-silver differing in average particle size (1 and 20 nm) with respect to their inhibitory effects on a pure strain of the soil bacterium Paracoccus sp. Which is an efficient denitrifyer capable of transforming NO3 into N2. This process is an important step in the biogeochemical cycling of N, and one that may potentially produce large amounts of the potent green house gas N2O if impeded by environmental pollutants. The results show that nano-silver is highly toxic to denitrifying bacteria and that low amounts severely affect the process of denitrification. Studies using indigenous denitrifying bacterial communities incubated in the presence of different concentrations of nano-silver in soil slurries are under way and will provide data where soil constituents affect the bioavailability nano-silver in a close to realistic exposure scenario. The implications of the relationship between toxicity levels in pure cultures and soil slurries will be discussed regarding the bioavailability of nanoparticles as pollutants in terrestrial environments.
Abstract
No abstract has been registered
Authors
Nadeem Yaqoob Jan Karlsson Benedicte Riber Albrectsen Halvor Solheim Carl Gunnar FossdalAbstract
In natural conditions plants are continuously exposed to number of pathogens both biotrophs and necrotrophs. To understand their defense response at the transcript level two clones C72 and C23 with differential level of resistance from the SwAsp collection were inoculated with a biotroph (Melampsora magnusiana Wagnar) and necrotroph (Ceratocysis spp.) and compared to wounded and healthy controls. Samples were collected in leaves and areas some distance away from the inoculation site to examine the long distance (systemic) defense responses at day, day3 and day14 post treatments. We performed microarray experiments on the necrotrophic and biothrophic interaction compared with the healthy controls and found that the two clones respond in widely different fashions to the treatments applied. Clone C23 showed almost no response to biotroph and necrotroph inoculations after 24 hours while clone 72 gave a clear defense response to both pathogens. We are now in the process of verifying these results and looking at additional time-points using qRT-PCR.
Abstract
Tree and understorey fine root growth and longevity was determined by minirhizotrone research in northern Finland. The study was made in a 70-year-old Norway spruce stand, growing on a mesic mineral soil site in the Kivalo experimental forest. Three replicate plots were established, and three vertical minirhizotron tubes installed in June 2003 in soil of each of the three plots. The images were taken at monthly intervals (altogether 11 sessions) during the growing seasons 2004, 2005 and 2006. The lengths, diameters and status (new, living, dead, disappeared) of Norway spruce and understorey (mainly shrub) fine roots were recorded. Our data indicates that there were more new roots growing in the upper soil depths (the organic layer) than in the lower soil depths (mineral soil). Roots in the organic layer, however, elongated less than roots in the upper mineral soil. The growth rate was highest in late summer and early autumn. Regarding root longevity, both trees and understorey showed the same trends by root order and soil depth; the average longevity was 14-16 months. The time from death to disappearance was 6-8 months for trees and 2-7 months for understorey. Furthermore, monthly trends of new roots born versus their death and/or disappearance by soil depth are also presented.
Abstract
No abstract has been registered
Abstract
The common European cerambycid Leiopus nebulosus (Linnaeus, 1758) is herein split into two sibling species. The male genitalia characters, as well as spermathecae in females, were examined and found to provide strong support for this separation. A new species, Leiopus linnei sp. nov., is based on specimens mainly from Scandinavia. The establishment of the new species is supported by DNA barcoding of Scandinavian specimens of L. nebulosus, L. linnei sp. nov., and L. punctulatus (Paykull, 1800). There are significant genetic differences between all these species. The geographical distribution and the bionomy of L. nebulosus and L. linnei sp. nov. are described. The type of Cerambyx nebulosus Linnaeus, 1758 is lost. A neotype of Cerambyx nebulosus, currently Leiopus nebulosus (Linnaeus, 1758), is designated and a redescription of L. nebulosus is presented. A key for the identification of L. nebulosus and L. linnei sp. nov. is provided. The varieties L. nebulosus var. dissimilis Pic, 1889, L. nebulosus var. unifasciatus Pic, 1891, and L. nebulosus var. siculus Pic, 1924 are considered as junior synonyms, syn.nov. of L. nebulosus.
Abstract
Mechanical strength properties are the most important feature of wood in constructions. In decaying wood strength loss can precede mass loss. Hence, both in laboratory and outdoor applications non-destructive measurement methods for early decay detection are in demand. The aim of this study was to evaluate the applicability of ultrasonic pulse propagation as a tool for decay detection in different laboratory setups. A dynamic MOE (MOEdyn) strength test device based on measurement of ultrasonic pulse propagation was used for non-destructive strength evaluation in different exposure situations for Scots pine sapwood. Two different test setups were used. In the first test MOEdyn was measured above fibre saturation. A range of different wood protection treatments were tested according to the terrestrial microcosms (TMC) test, a modified ENV 807. Three different soil types were used: forest soil dominated by white rot, Simlångsdalen test field soil dominated by brown rot and compost soil characterised by a mixture of bacteria and soft rot. Before strength testing the samples were water saturated and MOEdyn was measured above the fibre saturation point at time intervals (0, 8, 16, 24, 32 and 40 weeks) using ultrasound. Comparisons of strength loss were performed between treatments in the different soil types, and strength loss was also compared with mass loss. In the second test MOEdyn were measured below fibre saturation. Ultrasound measurements were performed on 0.5 m pine logs sampled from five trees from the same stand in central Southern Norway. Logs from two of the trees had varying amounts of discoloration due to an incipient attack by the white rot fungus Phlebiopsis gigantea during storage. Amount of visible discoloration had effect on MOEdyn values from measurements on log ends. Transversal measurement of MOEdyn was not successful. In a subsequent water uptake test, logs with discoloration absorbed substantially more water than the rest of the sample. The conclusion of this study was that the use of ultrasonic MOE is applicable as an evaluation tool in early decay detection.
Abstract
No abstract has been registered