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.
1994
Forfattere
Kjell AndreassenSammendrag
Det er ikke registrert sammendrag
Forfattere
Harald KvaalenSammendrag
Ethylene production from an embryogenic culture of Norway spruce (Picea abies L.) was generally low, ca 2.5 nl g(-1) h(-1), whereas 1-aminocycloprapane-1-carboxylic acid (ACC) concentration was high, fluctuating between 50 and 500 nmol g(-1) during the 11-day incubation period. Hypoxia (2.5 and 5 kPa O-2) rapidly inhibited ethylene production without subsequent accumulation of ACC. Exogenous ACC (1, 10 and 100 mu M) did not increase ethylene production, but the highest concentrations inhibited tissue growth. Ethylene (7 mu l l(-1)) did not inhibit growth either when supplied as ethephon in the medium or in a continuous flow system. Benzyladenine (BA) had little effect on ethylene production, although it was necessary for sustaining the ACC level. Omission of 2,4-dichloro-phenoxyacetic acid (2,4-D) from the medium caused ethylene production to increase from about 2.5 to 7 nl g(-1) h(-1) within the 11-day incubation period. Although 2,4-D did not specifically alter the endogenous level of ACC, the lowest ACC level, 33 nmol g(-1), was observed in tissue treated with 2,4-D (22.5 mu M) and no BA for 11 days. Data from this treatment were used to estimate the kinetic constants for ACC oxidase, the apparent K-m was 50 mu M and V-max 2.7 nl g(-1) h(-1). Growth of the tissue was strongly inhibited by 2,4-D in the absence of BA, but weakly in the presence of BA (4.4 mu M). The results suggest that ethylene or ACC may be involved in the induction of embryogenic tissue and in the early stages of embryo maturation.
Sammendrag
Det er ikke registrert sammendrag
Forfattere
Kjell AndreassenSammendrag
Det er ikke registrert sammendrag
Forfattere
Harald KvaalenSammendrag
Det er ikke registrert sammendrag
Forfattere
Dag FjeldSammendrag
Det er ikke registrert sammendrag
1993
Forfattere
Dag FjeldSammendrag
I et forsøk med maskinell flekkmarkberedning er arbeidskvaliteten undersøkt ved ulik skjermtetthet (Trondheim og Trysil). Arbeidskvaliteten er sammenlignet på snauflater og i skjermstillinger med 17 til 36 trær pr. daa. To kriterier for arbeidskvalitet er anvendt: Arealdekningen av markberedningstamme- og rotskader på gjenstående skjerm. Det ble benyttet både en- og to-rads traktoraggregat og gravemaskinmontert markberedningsutstyr. Forsøket viser at arealdekningen av kranmontert markberedningsutstyr er mindre påvirket av skjermtetthet enn traktormontert. Skader på gjenstående skjermtrær består primært av rotskader. Skadeprosenten er høy og øker med økt skjermtetthet. Resultatene indikerer at den viktigste faktor for skadeprosenten kan være andelen av blottlagt mineraljord
Forfattere
Harald Kvaalen Arild ErnstsenSammendrag
It is known that reducing the partial pressure of O2 influences the induction of somatic embryogenesis. We tested the hypothesis that O2 causes changes in the endogenous levels of exogenously supplied benzyladenine (BA) or 2,4-dichlorophenoxyacetic acid (2,4-D).Embryogenic tissue of Picea abies was incubated under reduced (2.5, 5 kPa) and ambient (21 kPa) levels of O2 for 1, 3, 7 and 11 days and the endogenous concentrations of BA and 2,4-D were measured. For all treatments the concentration of BA in the tissue increased until the third day. At day 3, the ratio of BA in the tissue relative to the initial concentration in the medium, was 3.9, 2.8 and 1.9 for tissue incubated under 2.5, 5 and 21 kPa O2, respectively. The BA concentration then declined gradually. Uptake of 2,4-D was inhibited at low O2 levels.However, 2,4-D gradually accumulated in tissue grown under hypoxia, so that high levels were reached by day 11. These shifts in the BA and 2,4-D levels also caused a transient increase in the BA to 2,4-D ratio in tissue incubated under hypoxia. Although relevant for the previously reported effects of oxygen on induction of embryogenic tissue, it is unlikely that oxygen-induced alterations in BA and 2,4-D levels alone suffice to explain these findings.
Forfattere
R. Minocha Harald Kvaalen S.C. Minocha S. LongSammendrag
Embryogenic cultures of red spruce (Picea rubens Sarg.) and Norway spruce (Picea abies (L.) Karst.) were initiated from dissected mature zygotic embryos. The tissues were grown on either proliferation medium or maturation medium. On proliferation medium, the embryogenic tissue continued to produce early stage somatic embryos (organized meristems attached to elongated, suspensor-like cells), whereas on maturation medium fully mature embryos developed from the embryonic tissue. Analysis of polyamines in tissues grown on these two media showed that: both putrescine and spermidine concentrations were always higher in cultures grown on proliferation medium than in cultures grown on maturation mediumin both species, spermidine concentrations declined with time in the tissues grown on maturation medium spermine was present in only minute quantities and showed only a small change with time. The presence of difluoromethylomithine in the culture medium had little effect on polyamine concentration, whereas the presence of difluoromethylarginine caused a decrease in putrescine concentrations in both red spruce and Norway spruce tissues grown on proliferation medium or maturation medium.
1992
Forfattere
Jan BjerketvedtSammendrag
Det er ikke registrert sammendrag