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.
2010
Forfattere
Marcel Van Oijen Ad Schapendonk Mats HøglindSammendrag
Background and Aims The carbon balance of vegetation is dominated by the two large fluxes of photosynthesis (P) and respiration (R). Mechanistic models have attempted to simulate the two fluxes separately, each with their own set of internal and external controls. This has led to model predictions where environmental change causes R to exceed P, with consequent dieback of vegetation. However, empirical evidence suggests that the R : P ratio is constrained to a narrow range of about 0·4-0·5. Physiological explanations for the narrow range are not conclusive. The aim of this work is to introduce a novel perspective by theoretical study of the quantitative relationship between the four carbon fluxes of P, R, growth and storage (or its inverse, remobilization). Methods Starting from the law of conservation of mass - in this case carbon - equations are derived for the relative magnitudes of all carbon fluxes, which depend on only two parameters: the R : P ratio and the relative rate of storage of carbon in remobilizable reserves. The equations are used to explain observed flux ratios and to analyse incomplete data sets of carbon fluxes. Key Results The storage rate is shown to be a freely varying parameter, whereas R : P is narrowly constrained. This explains the constancy of the ratio reported in the literature. With the information thus gained, a data set of R and P in grassland was analysed, and flux estimates could be derived for the periods after cuts in which plant growth is dominated by remobilization before photosynthesis takes over. Conclusions It is concluded that the relative magnitudes of photosynthesis, respiration, growth and substrate storage are indeed tightly constrained, but because of mass conservation rather than for physiological reasons. This facilitates analysis of incomplete data sets. Mechanistic models, as the embodiment of physiological mechanisms, need to show consistency with the constraints.
Sammendrag
Traditional wood preservatives based on biocides are effective against wood-deteriorating organisms because of their toxicity. By contrast, modified woods are non-toxic by definition. To investigate the efficiency of various wood modifications, quantitative real-time polymerase chain reaction (qPCR) was used to profile the DNA amounts of the white-rot fungus Trametes versicolor (L.) [Lloyd strain CTB 863 A] during an 8-week-long growth period in treated Pinus sylvestris (L.) sapwood. The studied wood was modified by acetylation, furfurylation, and thermal treatment. The traditional wood preservatives bis-(N-cyclohexyldiazeniumdioxy)-copper (Cu-HDO) and chromated copper arsenate (CCA) were used as references, whereas untreated P. sylvestris (L.) sapwood served as a control. The maximum levels of fungal DNA in native wood occurred at the end of the experiment. For all wood treatments, the maximum fungal DNA level was recorded after an incubation period of 2 weeks, followed by a decline until the end of the trial. For the preservative-treated woods, Cu-HDO showed the lowest level of fungal DNA throughout the experiment, indicating that exploratory hyphal growth is limited owing to the phytotoxicity of the treatment. The other treatments did not inhibit the exploratory hyphal growth phase. We conclude that qPCR studies of hyphal growth patterns within wood should provide a powerful tool for evaluating and further optimizing new wood protection systems.
Forfattere
David M Gadoury Arne Stensvand Robert C. Seem Catherine Heidenreich Maria Herrero Mary Jean Welser Andrew Dobson Håvard Eikemo Belachew AsalfSammendrag
Cleistothecia on leaves of deciduous perennials are often dispersed before leaf fall to other substrates. In contrast, strawberry leaves remain attached during winter, and cleistothecia of Podosphaera macularis remained attached to these leaves. Release of overwintered ascospores was coincident with renewed plant growth, and pathogenicity of ascospores was confirmed. Upper and lower surfaces of emergent leaves were similarly susceptible, but upper surfaces were obscured by folding in emergent leaves. Emergent leaves exposed to airborne inoculum developed severe infection of the lower surface, but not the obscured upper surface. Emergent leaves acquired ontogenic resistance during unfolding, and the upper leaf surface thereby escaped infection. We found no evidence that the pathogen survives winters in New York, USA or Norway within crown tissue. Plants stripped of infected leaves remained mildew-free when forced after overwintering, while mildew colonies commonly developed on emergent leaves of plants not stripped of mildewed leaves. Unsprayed plots established using mildew-free plants either remained asymptomatic or developed only traces of powdery mildew during one growing season, even when located within 100 to 150 meters of severely diseased plots. In summary, our results suggest the following: (i) sanitation, use of disease-free plants, and eradicative treatments could contribute greatly to management of strawberry powdery mildew; (ii) cleistothecia represent a functional source of primary inoculum; and (iii) the common observation of higher mildew severity on lower leaf surfaces may reflect escape of the upper epidermis due to the combined effect of leaf folding and rapid acquisition of ontogenic resistance.
Sammendrag
Colletotrichum acutatum causes bitter rot (often named anthracnose) in cherry and apple. It is the most important fruit decay in sour cherry in Norway and may give severe losses also in sweet cherry and apple. We have found the fungus in all fruit and berry crops grown commercially in the country and on many ornamentals and a few weeds. Single spore isolates frequently developed the ascigerous stage of the fungus (Glomerella acutata) in culture, but it was not detected on apple or cherry plant material. If still attached to the tree, fruits and fruit stalks of sour cherry infected the previous year produced conidial inoculum throughout the entire following season. Also newly infected sour cherry flowers produced conidial inoculum until harvest. Up to 80% of the fruit spurs on sweet cherry had buds infected with C. acutatum in spring. Apple buds also contained the fungus, but to a much lower extent. More than 90% of the sweet cherry leaves could be infected with C. acutatum around harvest in heavily infected orchards. Symptoms on leaves never appeared in the orchards. We also found such asymptomatic leaf infections in apples. Most of the inoculum seemed to be present on the fruit trees themselves. However, initial inoculum in newly established, disease free plantings may be introduced from older fruit trees, ornamentals and weeds in or in close vicinity to the orchards.
Forfattere
Jon Anders Stavang Rolf Inge Pettersen Micael Wendell Knut Asbjørn Solhaug Olavi Junttila Roar Moe Jorunn E. OlsenSammendrag
Active gibberellin (GA(1)) is an important mediator of thermoperiodic growth in pea. Plants grown under lower day than night temperature (negative DIF) elongate less and have reduced levels of GA(1) compared with plants grown at higher day than night temperature (positive DIF). By comparing the wild type (WT) and the elongated DELLA mutant la cry(s), this study has examined the effect of impaired GA signalling on thermoperiodic growth, photosynthesis, and respiration in pea. In the WT a negative DIF treatment reduced stem mass ratio and increased both root mass ratio and leaf mass ratio (dry weight of specific tissue related to total plant dry weight). Leaf, root and stem mass ratios of la cry(s) were not affected by DIF. Under negative DIF, specific leaf area (projected leaf area per unit leaf dry mass), biomass, and chlorophyll content of WT and la cry(s) plants were reduced. Young, expanding leaves of plants grown under negative DIF had reduced leaf area-based photosynthetic capacity. However, the highest photosynthetic electron transport rate was found in fully expanded leaves of WT plants grown under negative DIF. Negative DIF increased night respiration and was similar for both genotypes. It is concluded that GA signalling is not a major determinant of leaf area-based photosynthesis or respiration and that reduced dry weight of plants grown under negative DIF is caused by a GA-mediated reduction of photosynthetic stem and leaf tissue, reduced photosynthesis of young, expanding leaves, and reduced growth caused by low temperature in the photoperiod.
Forfattere
Jon Anders Stavang R. I. Pettersen M. Wendell K. A. Solhaug O. Junttila R. Moe J. E. OlsenSammendrag
Active gibberellin (GA1) is an important mediator of thermoperiodic growth in pea. Plants grown under lower day than night temperature (negative DIF) elongate less and have reduced levels of GA1 compared with plants grown at higher day than night temperature (positive DIF). By comparing the wild type (WT) and the elongated DELLA mutant la crys, this study has examined the effect of impaired GA signalling on thermoperiodic growth, photosynthesis, and respiration in pea. In the WT a negative DIF treatment reduced stem mass ratio and increased both root mass ratio and leaf mass ratio (dry weight of specific tissue related to total plant dry weight). Leaf, root and stem mass ratios of la crys were not affected by DIF. Under negative DIF, specific leaf area (projected leaf area per unit leaf dry mass), biomass, and chlorophyll content of WT and la crys plants were reduced. Young, expanding leaves of plants grown under negative DIF had reduced leaf area-based photosynthetic capacity. However, the highest photosynthetic electron transport rate was found in fully expanded leaves of WT plants grown under negative DIF. Negative DIF increased night respiration and was similar for both genotypes. It is concluded that GA signalling is not a major 25 determinant of leaf area-based photosynthesis or respiration and that reduced dry weight of plants grown under negative DIF is caused by a GA-mediated reduction of photosynthetic stem and leaf tissue, reduced photosynthesis of young, expanding leaves, and reduced growth caused by low temperature in the photoperiod.
Forfattere
Gedrime Kusliene Trond Olav Pettersen Tatsiana Espevig Trygve S. Aamlid Anne A. SteensohnSammendrag
High fertilizers rates, especially of nitrogen (N) and phosphorus (P), are commonly used for turfgrass grow-in on sand-based soils. The United States Golf Association recommends preplant applications of up to 1.0 kg P and 0.5 kg N per 100 m2 followed by applications of up to 0.3 kg N/100 m2 every fifth day until plant cover is complete. Such high rates of N and P, given before roots have developed, incur a great risk for nutrient leaching. Irrigation several times per day to keep the seedbed constantly moist also contributes to this leaching potential. iSeed® is a seed coat patented by Yara International ASA and used for grass seed marketed by DLF Trifolium. The coat contains both fast-acting and slow-release fertilizers, in total 10% N and 2% P of coated seed weight. The objective of this research was to determine the effect of iSeed® on turf quality and nitrogen and phosphorus leaching during turfgrass grow-in on two sand-based rootzones. A two-factorial experiment was carried out in the field lysimeter facility at Bioforsk Øst Landvik, South East Norway (58o34"N, 8o52"E) from 22 June to 26 July 2010. The rootzone was maid up of either straight sand, SS, or Green Mix®, GM, (Høst AS, Grimstad Norway), the latter being SS amended with 20% (v/v) mature garden compost. The 2 m2 lysimeter plots were seeded with either iSeed® or uncoated seed of the same seed lot of perennial ryegrass (Lolium perenne L.) ‘Berlioz 1", the sowing rate in both cases corresponding to 20 g/m2 pure seed. Use of uncoated seed was combined with preplant applications of 4 g N (as calcium ammonium nitrate, 27% N) and 0.8 g P (as superphosphate, 8% P) per m2, i.e. the same amount of total nitrogen and phosphorus as in the iSeed® coating. One treatment included additional applications of 5 g N (as calcium nitrate, 15.5% N) and 1.0 g P (as superphosphate, 8% P) on day no. 10 and 21 after sowing. The experiment was irrigated heavily, especially during the first ten days after sowing. Observations were made over the 35 day period. The results revealed significant effects of rootzone composition (SS vs. GM) and/or seed type/additional fertilizer application on turfgrass ground cover, overall impression, colour, surface traction and root development. For all these characters, the GM rootzone showed significant benefits compared with the SS rootzone; however, total nitrogen leaching was 21 % higher and total phosphorus leaching 11 times higher from the GM than from the SS rootzone. Plots seeded with iSeed® usually performed slightly better than plots seeded with uncoated seed, but the visual effects were mostly insignificant and small compared to those of additional fertilizer applications on day no 10 and 21 after sowing. Use of iSeed® reduced nitrate and total nitrogen leaching by approximately 50% during the first 10 days after sowing, but caused no significant reduction during the following 25 days; these effects probably reflect the slow-release properties of 82% of the nitrogen contained in iSeed®. Leaching of phosphorus was not affected by either seed type or additional fertilizer application. Interactions between rootzone and seed type/additional fertilizer applications were mostly not significant. We conclude that iSeed® has the potential to reduce nitrogen leaching during turfgrass establishment on sand-based rootzones. However, as iSeed® does not eliminate the need for additional fertilizer inputs about two weeks after sowing, the environmental benefit seems to be of relatively short duration when growing in perennial ryegrass on athletic fields. The advantages of iSeed® may perhaps be more significant when growing in forage or amenity grasslands over a longer period and with less fertilizer inputs.
Forfattere
Stine Andersen Anna Burkal Malene Falster Olsen Bent Egberg MikkelsenSammendrag
Adult habits, including unhealthy eating patterns, are largely established during a person´s childhood and early youth. In this connection, public schools are important health promoting platforms due to their potential for encouraging interest, knowledge and learning about health related issues. The main aim of the study was to shed light on primary and lower secondary school pupils´ everyday experience with food, nutrition, ecology and health in connection to public organic school food, using the municipality of Copenhagen as a case. We have examined how a procurement and provision strategy that primarily originates from “backstage agents” such as engaged politicians and civil servants and governed by administrative priorities, is perceived among agents at the front stage arena - the school. Furthermore we have investigated to which degree the pupils experience a connection between the “organicness” of the food program and the underlying organic supply chain principles, and to which degree the pupils experience a connection between the “organicness” of the food program and classroom initiatives in subjects related to ecology and health. In February 2008, we approached a public school which proved willing to participate in our study. Subsequently, over a period of four weeks, we designed an interview guide used to conduct focus group interviews with pupils from grades 5 and 7, which were then transcribed. In general, pupils were very interested in ecology as a subject. However it seems that they do not see a very strong connection between the healthy, organic meals offered at school and class room activities related to health and ecology. The pupils did not feel that they had been involved in the decision to establish organic and healthy food procurement. As a result they held that they did not feel very committed or engaged in the school provision initiative, and the organic and healthy food procurement was not highly sought after on the part of the pupils. This appears to justify a distinction between the perspective that front stage actors have, including pupils, and the perspective of politicians and planners that operate back stage. The distance between these two stages, which tends to increase in large scale municipal school food systems, is an important challenge to address when planning school food interventions. There seems to be a potential for linking organic school food service more closely with curricular activities, and for linking issues of healthier eating and organic food supply. There is also a need for greater involvement of the pupils and other front stage actors when the food service system and food related curricular activities are planned.
Sammendrag
Det er ikke registrert sammendrag
Forfattere
Margarita Novoa Garrido Harald VoldenSammendrag
The main objective of this experiment was to compare timothy and X-Festulolium varieties Felina and Felopa as forage for growing bulls. Thirty one-year-old Norwegian Red bulls were assigned to one of the three feeding groups by stratified block randomisation within weight in individual boxes and feeding. The forage was grown at Bioforsk"s research station in Bodø, (latitude: 67.28 °N), Norway, and harvested at a NDF content of 500 g/kg dry matter in the summer of 2008. The grass was ensiled in round balls and fed ad libitum. The bulls were fed a fixed amount of one kg of concentrate/day through the experiment. Animals were slaughtered at a live weight of 600 kg, and the slaughters were classified according to the EUROP system. The animals fed with timothy had an overall larger weight gain than the bulls fed with the X-Festulolium variants, though the weight gain decreased towards the end of the feeding period. The forage consumption in the timothy group was also larger. Grass type had no effect on the on the classification of the slaughters.