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.
2006
Authors
Ingjerd Solfjeld Øystein JohnsenAbstract
We have examined shoot and root growth and the concentration of carbohydrates in seedlings of a northern (67oN) and a southern (61oN) ecotype of Betula pendula Roth. cultivated at root-zone temperatures of 2, 6, 12 and 17oC. Three hydroponic experiments were conducted in controlled environments. We used three different pretreatments before seedlings were subjected to the experimental temperature treatments. Actively growing seedlings that were acclimated to the hydroponic solution for 3 weeks at a root temperature of 17oC, continued to grow at all the experimental temperatures, with an expected increase in growth from 2 to 17oC. However, if we started with ecodormant cold stored plants or used seedlings grown actively in perlite, no growth was observed at 2oC and only minor growth was found at 6oC. The highest root temperature always produced the best growth. The concentration of nonstructural carbohydrates was higher in seedlings grown at 2oC than at 17oC, and this is probably due to extensive incorporation of carbohydrates into cell walls and otherstructural elements at 17oC. We found no evidence for differences between the two ecotypes in root growth, in timing of bud burst, but shoot growth terminated in the northern ecotype in the first experiment because the natural photoperiod was below the critical value. Our study highlights the importance of post-transplantation stress (planting check) related to root growth, and that root threshold temperatures may change according to the way plants are pretreated.
Authors
Volkmar TimmermannAbstract
Monitoring on the forest officers\" plots in Norway has been running since 1988, with annual assessments carried out by local forest officers. In 2005 they assessed 30277 trees on 557 plots. For 15090 of these trees on 348 plots, there exist complete records of crown condition over the past 18 years. The plots are subjectively selected, mainly in Norway spruce dominated stands, and divided into four development classes. The results from 2005 show a slight increase in mean defoliation of Norway spruce to 16.4 %. There were small, but mostly negative changes in most regions without clear trends in the long term series. In southern Norway, a strong increase in defoliation was observed. Crown colour was improving in the western and northern regions of the country, whereas discolouration was increasing in south-eastern Norway. The mean discolouration was still very low in 2005, with 90 % of the spruce trees having normal, green colour. The mortality rate was low, on the average 3.4 ‰ for all trees. Only few causal agents of crown damage were reported. Data from 18 years of monitoring on the forest officers’ plots reveal some regional patterns for defoliation of spruce in Norway, with western Norway having the lowest mean defoliation through all years, and Mid-Norway the highest. In the other regions, the trends are not so clear with greater fluctuations in defoliation and discolouration.
Authors
Erik Lysøe Sonja Klemsdal Karen Rae Bone Rasmus J. N. Frandsen Thomas Johansen U. Thrane Henriette GieseAbstract
Zearalenones are produced by several Fusarium species and can cause reproductive problems in animals. Some aurofusarin mutants of Fusarium pseudograminearum produce elevated levels of zearalenone (ZON), one of the estrogenic mycotoxins comprising the zearalenones. An analysis of transcripts from polyketide synthase genes identified in the Fusarium graminearum database was carried out for these mutants. PKS4 was the only gene with an enoyl reductase domain that had a higher level of transcription in the aurofusarin mutants than in the wild type. An Agrobacterium tumefaciens-mediated transformation protocol was used to replace the central part of the PKS4 gene with a hygB resistance gene through double homologous recombination in an F. graminearum strain producing a high level of ZON. PCR and Southern analysis of transformants were used to identify isolates with single insertional replacements of PKS4. High-performance liquid chromatography analysis showed that the PKS4 replacement mutant did not produce ZON. Thus, PKS4 encodes an enzyme required for the production of ZON in F. graminearum. Barley root infection studies revealed no alteration in the pathogenicity of the PKS4 mutant compared to the pathogenicity of the wild type. The expression of PKS13, which is located in the same cluster as PKS4, decreased dramatically in the mutant, while transcription of PKS4 was unchanged. This differential expression may indicate that ZON or its derivatives do not regulate expression of PKS4 and that the PKS4-encoded protein or its product stimulates expression of PKS13. Furthermore, both the lack of aurofusarin and ZON influenced the expression of other polyketide synthases, demonstrating that one polyketide can influence the expression of others.
Abstract
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Abstract
Pulpwood has been imported to Norway since the beginning of the 20th century. However, exotic plant species hitchhiking with pulpwood were not observed before c.1985. Prior to this the imported timber was debarked, and the chances that diaspores would have attached to a debarked log (compared to a log with bark) are very small.A greenhouse germination experiment based on 385 dm2 of sifted bark from the holds of nine Estonian pulpwood ships yielded 3187 seeds of 201 species of vascular plants, few of which were typical of coniferous forests. Approximately 39% of the hitchhiking seeds did not germinate until after a period of cold treatment.Most of the species germinated in low densities, and those occurring in greater numbers are common and widespread in Norway. Six species were new to Norway: Agrostis clavata, Androsace filiformis, Bidens radiata, Carex montana, Melica picta, and Ranunculus cassubicus.During the last 20 years, pulpwood has been imported to Norway from many countries around the world, e.g. Russia, Scotland, Canada, and Zaire. While the present data do not indicate any immediate threat from aggressively invasive exotics, in order to avoid the introduction of non-native species and reduce the potential for biological invasion, timber should ideally be debarked prior to importation.
Authors
Erik LarnøyAbstract
No abstract has been registered
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Authors
Peder GjerdrumAbstract
Foredraget tar opp problemstillinger knyttet til skurteknologi, til sammenhengen mellom skur- kapasitet, -nøyaktighet og -utbytte.
Abstract
No abstract has been registered
Abstract
No abstract has been registered