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.
1993
Authors
Jens Viktor Nørgaard Valerie Duran Øystein Johnsen Peter Krogstrup Snorri Baldursson Sara von ArnoldAbstract
Two sets, containing 9 and 72 embryogenic cell lines of Picea abies (L.) Karst., were tested for cryotolerance using a standard two-step cryopreservation protocol. Eight and 69 cell lines, respectively, survived freezing in all or some of the trials. A strong effect of cell line on regrowth after freezing was demonstrated in both sets. Culture morphology and maturation competence of the nine cell lines was unaffected by freezing and were not correlated to cryotolerance. In the 72 cell lines originating from seeds of five full-sib families, selected from a progeny test for their widely different autumn frost hardiness, a family effect on cryotolerance was observed. This effect was not related to physiological characters (ability to form embryogenic cultures and mature somatic embryos, autumn frost hardiness).
Authors
Richard HorntvedtAbstract
No abstract has been registered
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Authors
Erik Christiansen Gunnar FjoneAbstract
Defoliation of conifers occasionally precedes bark beetle attacks, suggesting that a severe loss of foliage and ensuing reductions in carbohydrate availability may enhance host tree susceptibility. To shed light on this question, different degrees of defoliation on young Picea abies were simulated by removing whole whorls of branches from below, the trees retaining 100, 50, or 25% of their original crown biomass. After one week or one year, the trees were inoculated with Ophiostoma polonkum, a tree-killing fungus transmitted by Ips typographus. Fungal proliferation and tree mortality increased with increasing levels of pruning. Pruning reduced stem diameter growth, but not carbohydrate reserves in foliage and bark. Foliar N, P, and Ca increased with increasing pruning. The results lend support to the hypothesis that a reduction in the photosynthesis capacity increases host tree susceptibility to a beetle-fungus attack, and that induced defence against infection depends on efficient translocation of assimilates to the sites of infection.
Authors
Per Holm NygaardAbstract
No abstract has been registered
Authors
Mette Goul ThomsenAbstract
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Authors
Harald Kvaalen Arild ErnstsenAbstract
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.
Authors
Dan AamlidAbstract
No abstract has been registered
Authors
Dan AamlidAbstract
No abstract has been registered