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.
2013
Authors
Nils Egil SøvdeAbstract
No abstract has been registered
Abstract
BACKGROUND: To grow remontant strawberries at high latitudes in autumn is challenging because of short days and low light levels. Nevertheless, current day and night temperatures in Norwegian coastal areas up to 63 degrees N are normally sufficient for growth and fruit development till early October, and even higher temperatures can be expected in the future according to climatic scenarios, with potential to prolong the growing season. However, light would be a minimum factor. It is therefore of interest to examine the effects of providing supplemental light when photosynthetic active radiation (PAR) falls below critical level for development of high fruit quality. OBJECTIVE: To examine effects on fruit yield parameters, fruit tension, Brix° and arthropod numbers, in order to investigate the potential of LED lighting using diodes giving red and blue light, as a means to prolong the growing season at northern latitudes. METHOD: In this two-year study remontant strawberry cvs ‘Everest’ and ‘Rondo’ were grown in high polytunnels. Two LED lighting levels (LED100 and LED300) were applied from 7 Pm to 7 AM, whenever light intensity fell below 400 μmol m−2 s−1 from first week of September, and compared to ambient light (control). The LED300 was peaking at wavelengths of 460 nm and 660 nm, respectively blue and red, and the relation between blue and red light was 1 : 8; LED100 delivered similar wavelengths but the blue to red relation was 2 : 8. Fruit yield, soluble solids (Brix°), fruit firmness, temperature (°C), dew point (°C), and PAR light (μmol m−2 s−1) were recorded. The experimental design was block with four replications. The lamps were hung with the light source 40 cm above top of canopy, giving a PAR radiation at top of canopy of LED100 and LED300 of respectively 900 and 258 μmol m−2 s−1. RESULTS: LED improved fruit yield and quality, but more at 900 than at 258 μmol m−2 s−1. However, highest light level was probably beyond the saturation point for photosynthesis, at least in early morning and late evening and the last three weeks of the harvesting season, because of low temperatures. Some fruit yield was not harvested because of too low temperatures to achieve ripen fruits after mid-October. Arthropods were sampled from ‘Rondo’ leaves 2–3 times per season, and aphids, spider mites and predatory mites (introduced) were the most numerous groups. LED significantly decreased the number of spider mites in the autumn. CONCLUSIONS: LED lighting has potential as light source growing remontant strawberries in high polytunnels, when PAR radiation is below 400 μmol m−2 s−1. However, to benefit fully of the light it would be necessary to grow the plants in winter tunnels and add heating. That would increase the yields significantly compared with our results.
Authors
Mekjell Meland Eva Birken Clive KaiserAbstract
Crop load adjustments in European plum trees (Prunus domestica L.) require thinning either by hand (mechanical) or chemical means to achieve marketable size, fruit quality and to overcome alternate bearing. Efficient tools for crop load management are highly desirable, since only a few chemical thinners are registered and hand thinning is labor intensive and costly. Gibberellic acid (GA3) was tested as a novel approach to regulate the crop load of the plum cultivar ‛Opal’ at Ullensvang, western Norway. The objective was to reduce flower bud induction in the “off-year” thus adjusting crop load the subsequent year. In 2008, an “off-year”, GA3 was applied to 9 year-old ‘Opal’ trees as a high volume spray to the point of run-off at 50 ppm or 100 ppm at either 5 weeks after full bloom or 10 weeks after full bloom, or on both dates and compared with untreated control trees. Trees were unthinned the first year but then thinned to commercial standard the following year. In the year of application, total yield was recorded and fruit quality evaluated. Return bloom, fruit set, yield and fruit quality were assessed the subsequent year. In general, there were no significant differences in crop load of all treated trees compared to untreated trees in the year of application (non-target crop) however, fruit weight increased slightly on those trees when GA3 was applied 5 weeks after full bloom compared to all other treatments and untreated trees. The following year (target crop) fruit set was significantly reduced for all GA3 treatments. The most effective application time was 5 weeks after full bloom. Before thinning, initial fruit set was greatest on untreated trees as well as on those trees treated with GA3 10 weeks after full bloom. Fruit weight and fruit colour were significantly better on trees with the least fruit set. GA3 applications had no effect on fruit firmness. It is concluded that GA3 is an effective tool for inhibiting flower bud induction in an “off-year” thus enabling crop load management the subsequent “on-year”.
Authors
Heleen de Wit Anders Bryn Annika Hofgaard Jonas Karstensen Maria Malene Kvalevåg Glen Philip PetersAbstract
No abstract has been registered
Abstract
A mountain pine beetle (MPB) epidemic is currently ravaging large areas of interior British Columbia (BC) with significant implications for ecosystem services including future timber supply and community economic stability. Information is needed on future stand dynamics in areas of impacted forests that are unlikely to be salvaged logged. Of greatest concern are stands dominated by lodgepole pine (>50% timber volume). Predicting how surviving trees in these areas respond and grow and the timing and species composition of natural regeneration ingress is of critical importance for multiple forest values. We undertook a retrospective study in the Flathead Valley of southeastern British Columbia where an intense MPB epidemic peaked in 1979–1980. Our objective was to gain insight into stand recovery and stand self-organization as influenced by species-specific growth responses of different sized secondary structure trees (individual seedling, sapling, sub-canopy and canopy trees surviving the epidemic) and post-beetle regeneration dynamics. MPB mortality rates, the percent of basal area killed by beetles, varied from 42% to 100% with most stands between 60% and 80%. In general, all surviving secondary structure released but the extent of growth release exhibited species variability. Release of surviving canopy lodgepole pine trees was often dramatic and greatest in stands with high total stand MPB mortality rates. Ingress of natural regeneration was slow in the first few years after MPB attack but there was a strong pulse of recruitment 10–20 years post disturbance which then slowed considerably. Nearly 30 years after the MPB attack, the stocking and composition of the understories have changed dramatically. Overall, the occurrence of the MPB epidemic resulted in more structurally and compositionally diverse stands leading to multiple successional pathways different from those of even-age pine dominated stands. The recovery and self-organization of unsalvaged natural stands in the Flathead Valley was a complicated process. It has provided insights for future forest management in areas impacted by the current massive MPB epidemic ongoing for the past decade in western North America.
Authors
Lydia Lawless Andreas C. Drichoutis Rodolfo M. Jr. NaygaAbstract
No abstract has been registered
Authors
Sveinn Are Hanssen Jan Ove Bustnes Lisbeth Schnug Sophie Bourgeon Trond Vidar Johnsen Manuel Ballesteros Christian Sonne Dorte Herzke Igor Eulaers Veerle Jaspers Adrian Covaci Marcel Eens Duncan John Halley Truls Borg Moum Rolf Anker Ims Kjell E ErikstadAbstract
© 2013 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Abstract
To investigate the role of dehydrins (DHNs) in extreme low-temperature (LT) tolerance, we sampled needle tissue of Siberian spruce (Picea obovata Ledeb.) from trees growing in an arboretum in Trondheim, Norway from August 2006 to April 2007 and tracked changes in LT tolerance via relative electrolyte leakage. We used western blotting to estimate relative amounts of proteins binding a DHN K-segment antibody, measured relative amounts of nine transcripts for small (<25 kDa) DHNs by quantitative reverse transcription–polymerase chain reaction (PCR) using primers developed for DHN transcripts in a closely related species, Picea abies (L.) Karsten, and isolated and sequenced PCR products for five P. obovata DHNs. Three protein bands of 53, 35 and 33 kDa were detected on western blots of SDS–PAGE-separated protein extracts. The 53-kDa DHN was already present late in the growing season, but accumulated during acclimation, and levels decreased rapidly during deacclimation. The 33- and 35-kDa proteins, identified as Picg5 class DHNs by mass spectrometry, first appeared in detectable amounts late in the acclimation process and remained at detectable levels throughout the period of maximum LT tolerance. Levels of the 53-kDa DHN correlated with two LT tolerance parameters, while results for the 33- and 35-kDa proteins were equivocal due to limited sample size and variation in LT tolerance during the mid-winter period. Three additional bands of 30, 28 and 26 kDa were detected in extracts from needles collected in November 2010 using an immunity-purified antibody. Immunoblotting of two-dimensional gel electrophoresis gels loaded with proteins extracted from October and November samples corroborated the results obtained by SDS–PAGE western blots. One large spot in the 53 kDa range and two trains of spots in the same size range as the 33 and 35 kDa DHNs were detected using the K-segment antibody. Eight of the nine DHN transcripts closely tracked LT tolerance parameters, whereas the ninth DHN transcripts followed a reverse pattern, decreasing during winter and increasing again during deacclimation. Multiple regression models using principal components of the transcripts to predict two different LT tolerance parameters suggest separate but overlapping functions for different DHNs in establishing and maintaining extreme LT tolerance.
Authors
A.E. Bond R. Metcalfe P. Suckling K. Tatcher R. Walke K. Smith Daniel Rasse M. Steven D. JonesAbstract
No abstract has been registered