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.
1998
Authors
Espen Lydersen Valter Angell Odd Eilertsen Thorbjørn Larssen Jan Mulder I.P. Muniz Hans Martin SeipAbstract
No abstract has been registered
Authors
Vincent R. Franceschi Trygve Krekling Alan A. Berryman Erik ChristiansenAbstract
The bark anatomy of Norway spruce clones that were resistant or susceptible to Ceratocystis polonica, a bark beetle vectored fungal pathogen, was compared. The major difference concerned the axial parenchyma cells, called polyphenolic parenchyma (PP cells) because of their vacuolar deposits. The phenolic nature of the deposits was indicated by autofluorescence under blue light, and immunocytochemical studies demonstrating PP cells are enriched in phenylalanine ammonia lyase (EC 4.3.1.5), a key enzyme in phenolic synthesis. Susceptible clone PP cells occurred as single rows filled with dense deposits. The resistant clone had 40% more PP cells, which occurred in rows two cells thick with individual cells also scattered among the sieve cells, and had lighter deposits. Trees inoculated with fungus were analyzed but a distinct fungal response could not be separated from the general wound response. In the resistant clone, phenolic bodies were reduced in size and density or disappeared completely 12 day after wounding, and PP cell size increased. The susceptible clone phenolics and cell size changed only slightly. These data show that PP cells are active in synthesis, storage, and modification of phenolics in response to wounding, providing a primary site of constitutive and inducible defenses.
Authors
Sondre Skatter Bohumil KuceraAbstract
A new theory is presented on the cause of the prevalent directions of the spiral grain patterns found in conifers. The hypothesis is based upon the assumption that spiral grain has a function, i.e. that it represents a growth strategy to ensure survival of the trees. The mechanical function of the tree trunk is placed in focus, that is the ability of the trees to withstand external mechanical loads, mainly from wind. Spiral grain is an optimized growth feature when the trees are exposed to combined bending and torsion. Torsion occurs when the crown is asymmetric in the plane perpendicular to the wind direction. Systematic crown asymmetry, with heavier crowns on the south side, was confirmed by measuring the crown projections on 253 sparsely grown pines; 76.7% of the trees had longer branches on the south than on the north side, and the average length difference was 40.8 cm. By studying wind maps it was seen that most of the coniferous forests have prevailing westerly winds, which, when combined with the crown asymmetry, leads to a prevailing torque. Right-handed spiral grain in the outermost layers of mature trees is proposed to be a strategy to withstand this torque, i.e. to avoid stem breakage
Authors
Anne Sverdrup-Thygeson Fred MidtgaardAbstract
No abstract has been registered
Authors
E. Hellström M. Palo Birger SolbergAbstract
No abstract has been registered
Abstract
The genus Bryomyia comprises altogether eight species in the Palearctic region, including one new species Bryomyia amurensis Mamaev et Økland described in the present article. A revised key to the species of Bryomyia in the Holarctic region is presented.
Authors
Karl Hilding Thunes Fred MidtgaardAbstract
No abstract has been registered
Authors
Sondre SkatterAbstract
No abstract has been registered
Authors
Jan MulderAbstract
No abstract has been registered
Authors
Franck Brignolas François Lieutier Daniel Sauvard Erik Christiansen Alan A. BerrymanAbstract
Changes in phloem phenolic content of Norway spruce (Picea abies (L.) Karst.) clones were followed during the first 12 days of the reaction induced by phloem artificial inoculation with Ceratocystis polonica Siem., a bark beetle (Ips typographus L.) associated fungus. The aim was to confirm our previous results concerning the mechanisms of this reaction and the possible predictors of Norway spruce resistance to bark beetles and their associated fungi. The induced reaction was characterized by a slight decrease of tanning ability and an increase of ()-catechin concentration, which confirmed our previous observations. The relative resistance of the clones was first predicted using the predictors previously proposed. In addition, the first axis of the principal component analysis describing the phenolic content of all clones was used as a synthetic predictor (resistance axis). Related variables were also tested as predictors. Actual resistance of each clone was then measured, using mass inoculations of C. polonica, and was compared with the predictions. Four predictors were so validated: the resistance axis, tanning ability and isorhapontin concentration in uninoculated phloem, and ()-catechin concentration in the phloem 6 days after its inoculation. Phloem phenolic composition could thus be used to predict Norway spruce resistance to bark beetles and their associated fungi.