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.
2003
Authors
Lars Sandved Dalen J. Watkinson A.A. Sioson V. Singal D. Kumar N. Ramakrishnan L.S. Heath Carl Gunnar Fossdal R. GreneAbstract
Trees cover over one-third of the world\"s land area and carry out about two-thirds of global photosynthesis. Coniferous forests cover 1.2 billion hectares of Alaska, Canada, Scandinavia, and Russia, and comprise one-fourth of the world\"s boreal and temperate forests. More than 50% of Scandinavia\"s land area consists of forests, mostly coniferous. Information about the molecular responses in trees to biotic and abiotic factors is therefore of great importance - both scientifically and practically.Transcript regulation in response to drought stress was investigated for Norway spruce (Picea abies) with microarrays including 1,700 cDNAs from 5 EST libraries from Pinus taeda and analyzed using the Expresso Microarray Management System.In order to verify the level of drought stress, we measured the physiological status of the plants. After four days of drought, chlorophyll fluorescence was reduced by 6% and after eight days by over 40 %, compared to the control. Hybridizations of spruce RNA to microarray slides was used to probe for changes in transcripts from two to eight days after watering stopped.Monitoring of transcript levels was accomplished by hybridizing spruce cDNA to the 1700 element microarrays. After two days of drought, circa 2 % of the transcripts in Norway spruce were significantly upregulated and 7 % were downregulated. At the end of the experiment after eight days of drought needle chlorophyll fluorescence was reduced by 40 % compared to the control, and 6 % of the transcripts were upregulated and 12 % of the transcripts were downregulated. Results from inductive logic programming are also presented.
Abstract
No abstract has been registered
Abstract
An individual-based agent model is presented which resembles aspects of natural evolution in ecosystems under selective pressure due to limited resources. The environmental conditions are determined by spatial and temporal variability of resource abundances.The agents have to choose between three different types of resources; the one consumed most during lifetime solely counts for the fitness of the individual agent. Simulation runs show that populations specialized in different resource types are mutually influencing each other under temporal variation of a single resource type.Mobility of agents in a locally heterogenous world enables recolonization after a population has starved to death. Wavelet analysis of the population time series reveals that some observed population dynamics show phenomena such as localized periodicities which cannot be explained by linear dependencies on the resource input dynamics.
Authors
Stephen Woodward Jan Stenlid Marco Michelozzi Halvor Solheim B. Karlsson Panaghiotis TsopelasAbstract
No abstract has been registered
Authors
Ulf SikströmAbstract
No abstract has been registered
Authors
J.W. Hudgins Erik Christiansen Vincent R. FranceschiAbstract
Conifers have defenses such as the production of phenolic compounds and resins that can be induced by bark beetles and other invading organisms, but the signaling agents involved are unknown. The anatomical effects of methyl jasmonate (MJ), a potent inducer of certain plant defenses, were compared with wounding of the bark of 1215-year-old trees of five conifer species.Wounding in all species resulted in tissue necrosis and wound periderm development immediately around the wound site. One cm from the wound, swelling of phloem polyphenolic parenchyma cells and phenolic accumulation were observed in Pseudotsuga menziesii (Mirb.) Franco, Picea pungens Engelman, Larix occidentalis Nutt. and Pinus monticola Douglas ex D. Don, but not in Taxus brevifolia Nutt.Traumatic resin ducts were formed in response to wounding in three species of Pinaceae, but not in P. monticola, which formed irregular clusters of cells rather than ducts. Taxus brevifolia did not form resin ducts in response to either wounding or MJ treatment.In the Pinaceae species studied, surface application of 100 mM MJ caused similar anatomical changes to those observed in response to wounding, including phenolic accumulation, cell swelling and traumatic resin duct formation, but it did not induce a wound periderm.Traumatic resin ducts differed in size among the study species, ranging from small in L. occidentalis to very large in P. menziesii. In P. menziesii, P. pungens and L. occidentalis, traumatic resin ducts were more abundant after MJ treatment than after wounding. We conclude that the octadecanoid pathway is likely involved in defense responses in stems of the Pinaceae, but not necessarily in other taxa.
Authors
Holger LangeAbstract
High resolution digital elevation maps (DEMs) offer the investigation of multifractal properties of the spatial characteristics of river basins like the width function, and the determination of the relation between average slope and basin area.There have been a number of universality claims in this respect; the range of the scaling exponent for the slope-area relation seems to be narrow, and the multifractal spectrum of the width function is characterized by a single site-specific Lipschitz-Hlder exponent alpha, the spectrum having an envelope given by that of Peanos basin.Comparing 17 river basins covering two orders of magnitude in basin area, our findings do not confirm this universal character. In particular, the Lipschitz-Hlder exponent crucially depends on the resolution of the width function extraction; we show that it is easy to produce almost identical spectra for completely different basins when varying the resolution.The problem of interior points is also encountered. We adopt Venezianos modified calculation of f(alpha) in this case. The slope-area exponent covers a wide range of values which also include the pure random case. We thus question the usability of these measures as a classification tool for river basins. http://www.cosis.net/abstracts/EAE03/05246/EAE03-J-05246.pdf
Authors
Bjørn ØklandAbstract
No abstract has been registered
Authors
Ali Temiz Morten Eikenes U.C. Yildiz Fred G. Evans Bjørn JacobsenAbstract
No abstract has been registered
Abstract
No abstract has been registered