Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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LED or HPS in ornamentals? A case study in roses and campanulas
Ouzounis, Theoharis ; Giday, Habtamu ; Kjaer, Katrine H. ; Ottosen, Carl-Otto - \ 2018
European Journal of Horticultural Science 83 (2018)3. - ISSN 1611-4434 - p. 166 - 172.
Energy saving - Greenhouses - Light sources - Ornamentals

The aim of the experiment was to evaluate the effect of novel top-installed high-output light-emitting diodes (LEDs) on ornamental plant production both in terms of productivity and energy use in comparison with conventional HPS lamps in two standard greenhouse compartments. The experiments were performed in late winter period using three varieties of potted miniature roses (Rosa hybrida) and two cultivars of Campanula grown in identical installed supplemental light levels (75–85 µmol m-2 s-1 of PPFD) with temperature set points 18°C at night, 24°C during the day, while 800 ppm of CO2 was supplied. Due to the winter being relatively cold, the set points were equal to the realized temperature as ventilation rarely occurred. The leaf temperature was maintained at the same level by adjusting the top pipe temperature. Two harvests were performed in February and in March to show the potential effect of winter-or early spring-grown plants. The results showed relatively small differences with respect to plant performance between the HPS and LED treatments, and most significant differences were found only in the 1st batch of roses harvested in February regarding plant height and stem fresh and dry weight, indicating that growth was favored under HPS lamps for three out of four cultivars. Both the 2nd batches for roses and campanulas harvested in March showed very limited or no differences between treatments. The energy saving on the electricity side was 60% in LEDs compared to HPS, but due to the increased heat use from top pipes the energy used for heating increased by around 50% over the whole experimental period.

Allopolyploidization in Cucumis contributes to delayed leaf maturation with repression of redundant homoeologous genes
Yu, Xiaqing ; Wang, Xixi ; Hyldgaard, Benita ; Zhu, Zaobing ; Zhou, Rong ; Kjaer, Katrine Heinsvig ; Ouzounis, Theoharis ; Lou, Qunfeng ; Li, Ji ; Cai, Qingsheng ; Rosenqvist, Eva ; Ottosen, Carl-Otto ; Chen, Jinfeng - \ 2018
The Plant Journal 94 (2018)2. - ISSN 0960-7412 - p. 393 - 404.
The important role of polyploidy in plant evolution is widely recognized. However, many questions remain to be explored to address how polyploidy affects the phenotype of the plant. To shed light on the phenotypic and molecular impacts of allopolyploidy, we investigated the leaf development of a synthesized allotetraploid (Cucumis × hytivus), with an emphasis on chlorophyll development. Delayed leaf maturation was identified in C. × hytivus, based on delayed leaf expansion, initial chlorophyll deficiency in the leaves and disordered sink‐source transition. Anatomical observations also revealed disturbed chloroplast development in C. ×hytivus. The determination of chlorophyll biosynthesis intermediates suggested that the chlorophyll biosynthesis pathway of C. × hytivus is blocked at the site at which uroporphyrinogen III is catalysed to coproporphyrinogen III. Three chlorophyll biosynthesis‐related genes, HEMA1, HEME2 and POR, were significantly repressed in C. × hytivus. Sequence alignment showed both synonymous and non‐synonymous substitutions in the HEMA1, HEME2 and POR genes of the parents. Cloning of the chlorophyll biosynthetic genes suggested the retention of homoeologs. In addition, a chimeric clone of the HEMA1 gene that consisted of homologous genes from the parents was identified in C. × hytivus. Overall, our results showed that allopolyploidization in Cucumis has resulted in disturbed chloroplast development and reduced chlorophyll biosynthesis caused by the repressed expression of duplicated homologous genes, which further led to delayed leaf maturation in the allotetraploid, C. × hytivus. The preferential retention/loss of certain types of genes and non‐reciprocal homoeologous recombination were also supported in the present study, which provides new insights into the impact of allopolyploidy.
Avoiding pitfalls in interdisciplinary education
Holt, R.E. ; Woods, P.J. ; Ferreira, A.S.A. ; Bardarson, H. ; Bonanomi, S. ; Boonstra, W.J. ; Butler, W.E. ; Diekert, F.K. ; Fouzai, N. ; Holma, M. ; Kokkalis, A. ; Kvile, K. ; Macdonald, J.I. ; Malanski, E. ; Nieminen, E. ; Ottosen, K.M. ; Pedersen, M.W. ; Richter, A. ; Rogers, L. ; Romagnoni, G. ; Snickars, M. ; Törnroos, A. ; Weigel, B. ; Whittington, J.D. ; Yletyinen, J. - \ 2017
Climate Research 74 (2017)2. - ISSN 0936-577X - p. 121 - 129.
Climate change - Education - Interdisciplinarity - Learning mechanisms - Research network
As the world's social-environmental problems increasingly extend across boundaries, both disciplinary and political, there is a growing need for interdisciplinarity, not only in research per se, but also in doctoral education. We present the common pitfalls of interdisciplinary research in doctoral education, illustrating approaches towards solutions using the Nordic Centre for Research on Marine Ecosystems and Resources under Climate Change (NorMER) research network as a case study. We provide insights and detailed examples of how to overcome some of the challenges of conducting interdisciplinary research within doctoral studies that can be applied within any doctoral/postdoctoral education programme, and beyond. Results from a selfevaluation survey indicate that early-career workshops, annual meetings and research visits to other institutions were the most effective learning mechanisms, whereas single discipline-focused courses and coursework were among the least effective learning mechanisms. By identifying the strengths and weaknesses of components of NorMER, this case study can inform the design of future programmes to enhance interdisciplinarity in doctoral education, as well as be applied to science collaboration and academic research in general.
Differential effects of elevated air humidity on stomatal closing ability of Kalanchoë blossfeldiana between the C3 and CAM states
Fanourakis, Dimitrios ; Hyldgaard, Benita ; Gebraegziabher, Habtamu ; Bouranis, Dimitris ; Körner, Oliver ; Nielsen, Kai Lønne ; Ottosen, Carl-Otto - \ 2017
Environmental and Experimental Botany 143 (2017). - ISSN 0098-8472 - p. 115 - 124.
Air humidity - Evaporative demand - Facultative CAM species - Stomata - Stomatal conductance - Transpiration

High relative air humidity (RH ≥ 85%) impairs stomatal functionality, attenuating plant capacity to cope with abiotic stress. Previous studies were limited to C3 species, so the RH effect on stomatal physiology of CAM plants remains unexplored. We addressed the topic through comparisons of C3 and CAM states in a facultative CAM species. These states were validated by diel measurements of net assimilation rate and malate level. In the first two experiments, three Kalanchoë interspecific hybrid cultivars were exposed to moderate (60%) or high (90%) RH. Both leaves that expanded at high RH and leaves that had expanded at moderate RH and were subsequently exposed to high RH (for nine days) showed increased stomatal conductance. In the third experiment, both C3 and CAM state plants of one K. blossfeldiana cultivar were exposed to low (40%), moderate (60%) or high (90%) RH. Plant transpiration during night-time was inversely related to ambient RH in either state, whereas during day-time a significant effect was only noted at 90% RH. Kalanchoë leaves showed a very effective control of water loss upon water deprivation, especially in the CAM state. Following a single week exposure to 90% RH, detached leaves showed increased rates of water loss during desiccation in C3 state plants. No effect of high RH on stomatal response to desiccation was noted in leaves detached from plants in CAM-state. It is concluded that the negative effect of either growth or one-week exposure to high RH is restricted to the C3 state in Kalanchoë.

Improving stomatal functioning at elevated growth air humidity : A review
Fanourakis, Dimitrios ; Bouranis, Dimitrios ; Giday, Habtamu ; Alves Carvalho, Dalia ; Rezaei Nejad, Abdolhossein ; Ottosen, Carl Otto - \ 2016
Journal of Plant Physiology 207 (2016). - ISSN 0176-1617 - p. 51 - 60.
Abscisic acid - Evaporative demand - Stomatal closing ability - Stomatal size - Water loss

Plants grown at high relative air humidity (RH ≥ 85%) are prone to lethal wilting upon transfer to conditions of high evaporative demand. The reduced survival of these plants is related to (i) increased cuticular permeability, (ii) changed anatomical features (i.e., longer pore length and higher stomatal density), (iii) reduced rehydration ability, (iv) impaired water potential sensitivity to leaf dehydration and, most importantly, (v) compromised stomatal closing ability. This review presents a critical analysis of the strategies which stimulate stomatal functioning during plant development at high RH. These include (a) breeding for tolerant cultivars, (b) interventions with respect to the belowground environment (i.e., water deficit, increased salinity, nutrient culture and grafting) as well as (c) manipulation of the aerial environment [i.e., increased proportion of blue light, increased air movement, temporal temperature rise, and spraying with abscisic acid (ABA)]. Root hypoxia, mechanical disturbance, as well as spraying with compounds mimicking ABA, lessening its inactivation or stimulating its within-leaf redistribution are also expected to improve stomatal functioning of leaves expanded in humid air. Available evidence leaves little doubt that genotypic and phenotypic differences in stomatal functioning following cultivation at high RH are realized through the intermediacy of ABA.

Antistranspirant compounds alleviate the mild-desiccation-induced reduction of vase life in cut roses
Fanourakis, D. ; Gebraegziabher, Habtamu ; Li, Tao ; Kambourakis, Emmanouil ; Ligoxigakis, Eleftherios K. ; Padadimitriou, Michael ; Strataridaki, Argiro ; Bouranis, Dimitrios ; Fiorani, F. ; Heuvelink, E. ; Ottosen, Carl-Otto - \ 2016
Postharvest Biology and Technology 117 (2016). - ISSN 0925-5214 - p. 110 - 117.
The vase life sensitivity to mild desiccation (12% weight loss) was addressed in rose, together with alleviation possibilities. The postharvest longevity upon arrival or following mild desiccation was determined on eight cultivars, combined with several morpho-physiological traits. Mild desiccation significantly decreased (10–39%) the vase life of six cultivars (termed sensitive), whereas it did not affect the vase life of two (thus tolerant). More severe desiccation (>12% weight loss) shortened the vase life of a tolerant cultivar. Stomatal control of water loss explained a large part of vase life variation following mild desiccation, whereas cut flower ability to rehydrate or pedicel rigidity (strength, wood density) did not significantly contribute to this variation. Four potentially-mitigating treatments were further tested on the three most sensitive to mild-desiccation cultivars. Antitranspirant treatments [SNP (elicitor of NO) or acetylsalicylic acid in vase water or darkening] decreased the cut flower water loss during the postharvest phase and alleviated the mild-desiccation-induced reduction in vase life. In contrast, Tween 20 (wetting agent) in the vase water shortened vase life. It is concluded that the vase life of previously desiccated cut roses can be extended by employing treatments that reduce the postharvest water loss.
Trends in marine climate change research in the Nordic region since the first IPCC report
Pedersen, M.W. ; Kokkalis, A. ; Bardarson, H. ; Bonanomi, S. ; Boonstra, W.J. ; Butler, W.E. ; Diekert, F.K. ; Fouzai, N. ; Holma, M. ; Holt, R.E. ; Kvile, K. ; Nieminen, E. ; Ottosen, K.M. ; Richter, A.P. ; Rogers, L.A. ; Romagnoni, G. ; Snickars, M. ; Tornroos, A. ; Weigel, B. ; Whittington, J.D. ; Yletyinen, J. ; Ferreira, A.S.A. - \ 2016
Climatic Change 134 (2016)1. - ISSN 0165-0009 - p. 147 - 161.
Oceans are exposed to anthropogenic climate change shifting marine systems toward potential instabilities. The physical, biological and social implications of such shifts can be assessed within individual scientific disciplines, but can only be fully understood by combining knowledge and expertise across disciplines. For climate change related problems these research directions have been well-established since the publication of the first IPCC report in 1990, however it is not well-documented to what extent these directions are reflected in published research. Focusing on the Nordic region, we evaluated the development of climate change related marine science by quantifying trends in number of publications, disciplinarity, and scientific focus of 1362 research articles published between 1990 and 2011. Our analysis showed a faster increase in publications within climate change related marine science than in general marine science indicating a growing prioritisation of research with a climate change focus. The composition of scientific disciplines producing climate change related publications, which initially was dominated by physical sciences, shifted toward a distribution with almost even representation of physical and biological sciences with social sciences constituting a minor constant proportion. These trends suggest that the predominantly model-based directions of the IPCC have favoured the more quantitatively oriented natural sciences rather than the qualitative traditions of social sciences. In addition, despite being an often declared prerequisite to successful climate science, we found surprisingly limited progress in implementing interdisciplinary research indicating that further initiatives nurturing scientific interactions are required.
What are the major global threats and impacts in marine environments? Investigating the contours of a shared perception among marine scientists from the bottom-up
Boonstra, W.J. ; Ottosen, K.M. ; Ferreira, A.S.A. ; Richter, A.P. ; Rogers, L.A. ; Pedersen, M.W. ; Kokkalis, A. ; Bardarson, H. ; Bonanomi, S. ; Butler, W. ; Diekert, F.K. ; Fouzai, N. ; Holma, M. ; Holt, R.E. ; Kvile, K. ; Malanski, E. ; Macdonald, J.I. ; Nieminen, E. ; Romagnoni, G. ; Snickars, M. ; Weigel, B. ; Woods, P. ; Yletyinen, J. ; Whittington, J.D. - \ 2015
Marine Policy 60 (2015). - ISSN 0308-597X - p. 197 - 201.
Marine scientists broadly agree on which major processes influence the sustainability of marine environments worldwide. Recent studies argue that such shared perceptions crucially shape scientific agendas and are subject to a confirmation bias. Based on these findings a more explicit engagement with scientists’ (shared) perceptions of global change in marine environments is called for. This paper takes stock of the shared understanding in marine science of the most pertinent, worldwide threats and impacts that currently affect marine environments. Using results from an email survey among leading academics in marine science this article explores if a shared research agenda in relation to global change in marine environments exists. The analysis demonstrates that marine scientists across disciplines are largely in agreement on some common features of global marine change. Nevertheless, the analysis also highlights where natural and social scientists diverge in their assessment. The article ends discussing what these findings imply for further improvement of interdisciplinary marine science.
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