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.
1992
Authors
Erik ChristiansenAbstract
The defence of Norway spruce against a combined attack of the bark beetle Ips typographus and its associated blue-stain fungi is based upon a) constitutive resin stored in ducts of the bark and sapwood, and b) induced resinosis in reaction zones surrounding the point of infection. Empirically, beetle epidemics are associated with external stresses, drought being a particularly prominent factor. An attempt was made to mechanistically explain the apparent link between drought and infestations, through studying after-effects of drought on the induced defence in stressed trees. In the field, 3-5.5 m tall trees were exposed to artificial drought over three growth seasons to investigate whether this treatment would predispose them to fungal infection in a fourth season when drought was absent. Pre-dawn xylem water potentials down to -1.85 MPa and a considerable foliage depletion were recorded. In the fourth season, the trees were inoculated with Ophiostoma polonicum, a pathogenic associate of Ips typographus. No difference in susceptibility could be seen between drought stressed trees and unstressed controls. Carbohydrate concentrations of foliage and branch bark were slightly enhanced and mineral nutrient concentrations strongly reduced in stressed trees.
Authors
Dan AamlidAbstract
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Authors
Anita JensenAbstract
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Alhaji S. Jeng Harald BergsethAbstract
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Authors
H. Sverdrup P. Warfvinge Tore Frogner Arnt-Olav Håøya M. Johanson B. AndersenAbstract
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Authors
Ingegerd Dormling Øystein JohnsenAbstract
Identical pair crosses, including reciprocals, in Pinus sylvestris L. (Scots pine) were made on ramets of the same clones in three clonal archives (seed orchards) in Sweden: Svar (64N), Rskr (59.5N), and Degeberga (56N). The offspring were used to test the hypothesis that the parental environment could affect the performance of the progeny (aftereffects). Growth and freezing tests were performed in the controlled conditions of the Stockholm Phytotron. Parental environment affected seed weight: the heaviest seeds came from Rskr and the lightest seeds, from Degeberga. Height development was affected in the two growth periods tested: seeds from Svar produced the shortest plants and seeds from Rskr, the tallest plants. There was an effect on the autumn frost hardiness in the first growth period that disappeared after the second growth period. The most hardy progenies came from Svar. The aftereffects of the parental environment were less than the maternal effects on seed weight and also less than the effects of full-sib families on growth and autumn frost hardiness. Small but mostly significant reciprocal effects were found for height and height increment during the second growth period. There was a significant reciprocal effect for seed weight. Seed weight differences could explain only a small part of the effects on growth and none of the effects on hardiness.