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.
1999
Forfattere
Unni AbrahamsenSammendrag
Resultater fra forsøk og avlingsregistreringer ved bruk av Moddus i havre i 1998
Forfattere
Heleen A. de Wit M. Kotowski Jan MulderSammendrag
Det er ikke registrert sammendrag
Forfattere
Heleen A. de WitSammendrag
Det er ikke registrert sammendrag
Forfattere
Bent C. BraskerudSammendrag
Det er ikke registrert sammendrag
Forfattere
Helge BonesmoSammendrag
The applicability of an expolinear growth equation for describing dry matter yield was investigated in seven field experiments for spring growth of timothy (Phleum pratense L.) and meadow fescue (Festuca pratensis Huds) under two levels of nitrogen application. The equation was expanded by a growth index (GI) correcting for variations in radiation, temperature, and plant available soil moisture and an ageing function describing the decrease in growth rate caused by advance in phenological development. The field sites covered a wide range of climatic conditions and the yield was recorded at five phenological stages from leaf stage to anthesis. The expansion of the equation appeared to be adequate for a combined analysis of the dry matter yield in meadow fescue and timothy. The estimated maximum growth rate during the linear phase (Cm) did not differ significantly between species. Cm increased with higher nitrogen application. It was concluded that Cm of the expanded model represented a potential rate, whereas the relative growth rate of the exponential phase (Rm) could not be considered as a potential rate. It varied more among locations and years, e.g. it was strongly affected by length of the period from growth onset to the start of the linear phase.
Forfattere
Carl Gunnar FossdalSammendrag
Plants are exposed to a great number of microorganisms under natural conditions. Pathogenic fungi and oomycetes are the main factors contributing to plant diseases, thus further understanding of plant-pathogen interactions may provide information leading to new strategies for reducing the damage caused by these pathogens on economically important trees and crops. Active plant-responses to microorganisms differ with respect to the degree of responses and with respect to the outcome of the interaction. In response to pathogens, active plant-defenses can be induced. Both local and systemic plant defense-response may be induced by pathogens. This thesis present indications of both local and systemic host responses at the molecular and cellular levels, using the conifer Norway spruce as a model host to study plan-pathogen interactions. Norway spruce seedlings were infected separately with the pathogenic fungi Heterobasidion annosum and Ceratocystis polonica, the pathogenic oomycete Pythium dimorphum and the ectomycorrhizal fungus Laccaria bicolor, to study the local and systemic effects of the infections at the cellular and molecular level. Increased levels of lignification was seen within 2 to 4 days in response to the pathogens, and indications of cytoplasmic translocations were also observed as a response to hyphae invading the root. Initially, a defense related plant peroxidase cDNA SPI2 (spruce pathogen induced 2) from Norway spruce roots was isolated and sequenced and found to encode a predicted 34kD SPI2 protein. The 34kD SPI2 protein was detected both in the root and shoot of Norway spruce seedlings, and accumulated as a local response to infection with the pathogenic oomycete Pythium dimorphum. In addition, two 38kD and 39kD SPI2 related proteins were detected in roots only after infection. Interestingly, increase levels of the 39kD SPI2 related protein was also detected in shoots of infected seedlings as a systemic response to infection. The putative plant defensin SPI1 (spruce pathogen induced 1) from Norway spruce has been proposed a role in the defense against pathogenic fungi and oomycetes. Here the predicted 5kD SPI1 protein was detected in Norway spruce seedlings and found to accumulate in roots during development. Notably, the putative plant defensin SPI1 lined the wall of cortical root cells, and in roots invaded by P. dimorphum the SPI1 protein was found associated with the invading hyphae. This supports the hypothesis that SPI1 has a role in the defense against pathogenic oomycetes and fungi. The possible protective role of prior colonization by the ectomycorrhizal fungus on later challenge with the pathogen C. polonica, previously known to be vectored to the tree stem by bark beetles, was also examined. Surprisingly, C. polonica was able to invade also roots of both mycorrhizal and non-mycorrhizal seedlings. Not only induced or enhanced plant responses were observed, but also reduced levels of defense-related proteins were observed in the infected roots at the later stages of infection. Decreased levels of SPI1was detected within 96 hours after infection in response to the pathogens tested. Reduced levels of the corresponding transcript was also detected indicating a suppression of host responses by the pathogens. Increased proteolytic activity was detected in infected roots, and from the pathogens. Proteolytic degradation of host proteins by fungal secreted proteases may reduce the levels of potentially antimicrobial proteins enabling the pathogens to effectively invade the roots. Reduced levels of the SPI1 in roots, was found also in response to the ectomycorrhizal fungus L. bicolor. Reduced levels of the peroxidase isozymes at the later stages of the infections, was also observed. Thus, suppressor(s) may be produced by both the pathogens and by the ectomycorrhizal fungus during infection, reducing the host responses and contributing to successful colonization of the roots.
Forfattere
Tor J. JohansenSammendrag
Det er ikke registrert sammendrag
Forfattere
J. Peter HallSammendrag
Det er ikke registrert sammendrag
Forfattere
A.S. IsaevSammendrag
Det er ikke registrert sammendrag
Forfattere
Anthony A. Hopkin J. Peter HallSammendrag
Det er ikke registrert sammendrag