Publikasjoner
NIBIOs ansatte publiserer flere hundre vitenskapelige artikler og forskningsrapporter hvert år. Her finner du referanser og lenker til publikasjoner og andre forsknings- og formidlingsaktiviteter. Samlingen oppdateres løpende med både nytt og historisk materiale. For mer informasjon om NIBIOs publikasjoner, besøk NIBIOs bibliotek.
2009
Sammendrag
Det er ikke registrert sammendrag
Forfattere
Igor A. Yakovlev Harald Kvaalen Carl Gunnar Fossdal Øystein JohnsenSammendrag
MicroRNAs (miRNAs) are endogenous small RNAs that can have large-scale regulatory effect and could participate in epigenetic regulation of gene expression in plants. We show for the first time that temperature during zygotic embryogenesis and seed maturation in Norway spruce regulates an “epigenetic memory” in the progeny, regenerated through somatic embryogenesis. The warmer the in vitro temperature applied, the later the regenerated plants formed terminal buds in the common environment the second growth season. The differences were very large, and similar in size to a provenance separation of 4 – 6 degrees of latitude (Kvaalen and Johnsen, 2008). To study a molecular mechanisms of a memory from embryo development we have prepared two concatemerized small RNA libraries representing small RNAs predominantly expressed in plants growing from seeds obtained after embryogenesis in cold environment (CEL) and warm environment (WEL) after short day (SD) treatment (going to bud set). In total we obtained 201 different small RNAs, with dominated length of 21-nt, 123 from WEL and 93 from CEL. Using multiple methods, including BLAST, sequence alignment and sequence folding we found 27 novel candidate miRNAs and only 3 earlier described. Additionally 103 small RNAs have exact matches in spruce EST database, which could be their putative targets and 67 small RNAs have no matches. We used quantitative RT–PCR to study the expression patterns of 31 chosen candidate miRNAs and monitor the occurrence stage-dependent miRNA-mediated cleavage for 4 regions of putative mRNA targets. All miRNA show difference in transcript levels after SD treatment and 12 miRNAs show constitutively differential expression in progeny from CE and WE. Kvaalen H, Johnsen O (2008) Timing of bud set in Picea abies is regulated by a memory of temperature during zygotic and somatic embryogenesis. New Phytologist 177: 49-59
Sammendrag
Wood is a traditional building material but in general it underlies restrictions in outdoor applications due to its respective durability against microbiological decay. To face this problem, different impregnation systems are applied to enhance the materials\" servicelife. Scots pine (Pinus sylvestris) is the most widely distributed pine in Eurasia and hence easily available. Despite of the previously defined good treatability of Scots pine sapwood, large differences in treatment performance are reported from industry. As process parameters are always adjusted to the material most difficult to treat, permeability variations in wood material are an economical problem. Therefore, it is important to understand the material in order to make a more reasonable material selection possible.....
2008
Sammendrag
Det er ikke registrert sammendrag
Sammendrag
Bruken av bioenergi kommer til å øke betraktelig i årene som kommer. Politisk ligger det målsettinger om en dobling av bruken i løpet av 12 år, og utbyggingstakten i fjernvarmesektoren er nær femdoblet siste fem år. Mange aktører står derfor på første trinn i læringskurven og skal vurdere ulike typer brensel, samt utforme en effektiv forsyningskjede for dette brenselet. Å ha en viss kontroll med kvalitet og kvantitet på brenselet er en forutsetning for å klare dette. En kubikk flis kan være så mangt. Grove målemetoder kan gi svært grove estimat på energimengden man har for hånden. Ulike definisjoner på brennverdi er av og til opphav til forvirring om energimengden i brenselet og virkningsgraden i ulike forbrenningsanlegg.....
Forfattere
Øystein Johnsen Igor A. Yakovlev Daniel Kwaku A. Asante Anne Eskild Nilsen Harald Kvaalen Carl Gunnar FossdalSammendrag
In forest trees, environmental conditions during the reproduction can greatly influence progeny performance. We here suggest that temperature during zygotic embryogenesis and seed maturation regulates an “epigenetic memory” in the progeny, involving differential expression of genes that may regulate bud phenology, cold acclimation and embryogenesis in Norway spruce. Conditions colder than normal advance the timing whilst temperatures above normal delay the onset of these processes. The altered performance lasts for many years. The seedlings actually remember the temperatures and photoperiod prevailing during zygotic embryogenesis and seed maturation. We show for the first time that regenerated plants, cloned through somatic embryogenesis, express a memory of the temperatures applied during embryo development whilst growing in a common greenhouse environment. The warmer the in vitro temperature applied, the later the regenerated plants formed terminal buds in the common environment the second growth season. The differences were very large, and similar in size to a provenance separation of 4 – 6 degrees of latitude. To study a molecular mechanisms of a memory from embryo development identical crosses were performed, seed were produced in different temperature regimes (cold and warm embryonic history) and seedling were grown under long day (LD = continuous light) and short day (SD = 12 h night) conditions. We have prepared two subtracted cDNA libraries, forward and revers, representing genes predominantly expressed in plants growing from seeds obtained after embryogenesis in cold environment (CE) and warm environment (WE) after short day treatment (going to bud set). Annotation reveals considerable differences in studied transcriptomes. More than 50% of contigs were unknown. So obtained subtracted libraries is a good source of candidate genes. We used quantitative RT–PCR to study the expression patterns of 34 chosen candidate genes. Just two putative genes among them with no matching in the Database and one reverse transcriptase show constitutively differential expression in progeny from CE and WE
Forfattere
Harald Kvaalen Øystein JohnsenSammendrag
It has been shown previously that height growth and bud phenology are influenced by the temperature during zygotic embryogenesis in Picea abies.To test whether this phenomenon operates within individual plants, clones produced through somatic embryogenesis were used. Seeds were from a full-sib family produced in both a cold (outdoor) and a warm (inside a glasshouse) environment. Embryogenic clones derived from mature zygotic embryos from both crossing environments were cultured at 18, 23 and 28 during the proliferation and embryo maturation steps.After the second growing season in a glasshouse, plants from the warm seed production environment were taller and had significantly later bud set. For the first time, it is also shown that plants are influenced by the in vitro temperature during somatic embryo development. The warmer the temperature, the later the plants formed terminal buds. The differences were similar to those produced by a provenance separation of 4-6 degrees of latitude.The results indicate that there exists a mechanism in P. abies that operates during embryo development and adjusts the timing of bud set in accordance with the temperature conditions in which the mother tree lives. This in turn counteracts negative effects of gene flow among populations located along altitudinal and latitudinal gradients.
Sammendrag
The treatability of Scots pine (Pinus sylvestris) sapwood is ranked in the European standard EN 350-2 as class 1 (easy to treat), although huge differences in sapwood penetration exist. To obtain full sapwood penetration, process parameters have to be adjusted to the material most difficult to treat. It is therefore of importance to understand the factors that are responsible for penetration differences. Scots pine sapwood was investigated for anatomical differences influencing the ratio of filling (RoF) when treated with the wood modifying agent furfuryl alcohol. The database for the study was samples from two test series including Scots pine from Norway and Denmark. Within these experimental series each sample can be reassigned to its original position in the stem. The RoF for each sample was evaluated, and the variation in treatability within trees, between trees and between different stands was studied...
2007
Forfattere
Jan BjerketvedtSammendrag
Det er ikke registrert sammendrag
Forfattere
Jan BjerketvedtSammendrag
Det er ikke registrert sammendrag