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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A new Global Agro-Environmental Stratification (GAES)
Mücher, Sander ; Simone, Lorenzo De; Kramer, Henk ; Wit, Allard de; Roupioz, Laure ; Hazeu, Gerard ; Boogaard, Hendrik ; Schuiling, Rini ; Fritz, Steffen ; Latham, John ; Cormont, Anouk - \ 2016
Wageningen : Wageningen Environmental Research (Wageningen Environmental Research rapport 2761) - 69
stratification - agriculture - environment - monitoring - agricultural production - sustainable agriculture - observation - stratificatie (zaden) - landbouw - milieu - landbouwproductie - duurzame landbouw - observatie
The GAES database (Version 01a) is a newly developed Global Agro-Environmental Stratification within the EU SIGMA (Stimulating Innovation for Global Monitoring of Agriculture) project. GAES will serve as a new agro-environmental stratification for better global monitoring of the agricultural production on the basis of Earth Observation data and crop growth models. It is anticipated that GAES will be exploited for a wider range of applications, some within SIGMA, towards data gap analysis that identifies agro-environmental strata with limited capacity and monitoring data on agricultural production. GAES was produced by applying segmentation techniques to newly available global agroenvironmental data with a high spatial resolution re-sampled to 1 km spatial resolution. The datasets were able to stratify the agricultural production zones according to the region’s agro-environmental characteristics, including climatic regimes, soil, terrain, elevation conditions, water availability and land cover proprieties. The GAES strata obtained by segmentation at four different spatial levels (with Level 4 as the most detailed) have been further characterised and described in terms of phenology (e.g. start and peak of the growing season), agricultural (water) management practices, field size, biotic constraints, national and sub-national crop production statistics, GDP, transport infrastructure conditions or market accessibility. The GAES database has four hierarchical layers, with 92 attributes. GAES Level 1 has 194 agro-environmental (AE) types (818 strata); GAES Level 2 has 300 AE types (1,688 strata); GAES Level 3 has 374 AE types (2,087 strata); GAES Level 4 has 516 AE types (3,208 strata). GAES typology is a combination of temperature, altitude, parent material and land cover characteristics. GAES Version 01 has become freely available.
Trade-off between light interception efficiency and light use efficiency: implications for species coexistence in one-sided light competition
Onoda, Y. ; Saluñga, J.B. ; Akutsu, K. ; Aiba, S.I. ; Yahara, T. ; Anten, N.P.R. - \ 2014
Journal of Ecology 102 (2014)1. - ISSN 0022-0477 - p. 167 - 175.
herbaceous plant community - temperate rain-forest - secondary forest - canopy structure - carbon gain - height - growth - photosynthesis - populations - stratification
1. Taller plant species can pre-empt solar energy and suppress growth of subordinate species in vegetation stands, which is described through one-sided competition. Yet, in much of the world’s vegetation species of different statures coexist. This study aims to clarify the mechanisms underlying this apparent paradox. 2. We quantified how co-occurring species and individuals intercepted and used light for growth in a mature, warm-temperate evergreen forest. This was performed by determining the 3D distribution of foliage and light with a ground-based lidar system in combination with nondestructive measurements of plant growth. 3. Taller trees intercepted light more efficiently per unit of above-ground biomass than shorter trees did (=higher light interception efficiency, LIE). However, taller trees tended to have lower biomass production per unit light interception (=lower light use efficiency, LUE). Reduced LUE in taller trees was associated with their higher biomass allocation to nonphotosynthetic organs and probably with over-saturated light intensity for photosynthesis at high canopy positions. Due to the increased LIE and decreased LUE with tree heights, a trade-off between LIE and LUE was found, and this trade-off resulted in trees of different statures having similar relative growth rates. 4. Synthesis. Light competition drives trees to grow taller, and the light interception efficiency is higher in taller trees; however, this benefit comes at a cost of decreased efficiency of light use for growth. This trade-off allows trees of different statures to grow at proportionally comparable rates and may promote coexistence of tree species in one-sided light competition.
A high-resolution bioclimate map of the world: a unifying framework for global biodiversity research and monitoring
Metzger, M.J. ; Bunce, R.G.H. ; Jongman, R.H.G. ; Sayre, R. ; Trabucco, A. ; Zomer, R. - \ 2013
Global Ecology and Biogeography 22 (2013)5. - ISSN 1466-822X - p. 630 - 638.
conterminous united-states - climate-change - land classification - observing system - europe - stratification - ecoregions - impacts - regions - trends
Aim To develop a novel global spatial framework for the integration and analysis of ecological and environmental data. Location The global land surface excluding Antarctica. Methods A broad set of climate-related variables were considered for inclusion in a quantitative model, which partitions geographic space into bioclimate regions. Statistical screening produced a subset of relevant bioclimate variables, which were further compacted into fewer independent dimensions using principal components analysis (PCA). An ISODATA clustering routine was then used to classify the principal components into relatively homogeneous environmental strata. The strata were aggregated into global environmental zones based on the attribute distances between strata to provide structure and support a consistent nomenclature. Results The global environmental stratification (GEnS) consists of 125 strata, which have been aggregated into 18 global environmental zones. The stratification has a 30 arcsec resolution (equivalent to 0.86 km2 at the equator). Aggregations of the strata were compared with nine existing global, continental and national bioclimate and ecosystem classifications using the Kappa statistic. Values range between 0.54 and 0.72, indicating good agreement in bioclimate and ecosystem patterns between existing maps and the GEnS. Main conclusions The GEnS provides a robust spatial analytical framework for the aggregation of local observations, identification of gaps in current monitoring efforts and systematic design of complementary and new monitoring and research. The dataset is available for non-commercial use through the GEO portal (
The significance of habitats as indicators of biodiversity and their links to species
Bunce, R.G.H. ; Bogers, M.M.B. ; Evans, D. ; Halada, L. ; Jongman, R.H.G. ; Mücher, C.A. - \ 2013
Ecological Indicators 33 (2013). - ISSN 1470-160X - p. 19 - 25.
agricultural landscapes - ecosystem services - europe - stratification - cover
The first section of the paper discusses the background to the use of habitats as indicators for biodiversity including a discussion of the range of definitions that have been used. Habitats can now be recorded consistently across Europe at different time intervals in order to estimate stock and change as an indicator of biodiversity that is efficient and relatively easy to record. Habitats are considered to be the third level in a hierarchy with biomes and landscapes as higher categories and vegetation, species and genetic diversity as lower levels. An advantage of using habitats is that many other taxa are associated with them and examples are given from the literature. Examples are also given of the association between habitats and species in European Environmental Zones using expert judgement. Statistical analysis using a range of procedures can also be used to assess the association between species and habitats. Reliable data on the extent, status and changes in European habitats is essential for policy makers across the European Union and would also be important for promoting species conservation.
A rural typology for strategic European policies
Eupen, M. van; Metzger, M.J. ; Pérez-Soba, M. ; Verburg, P.H. ; Doorn, A.M. van; Bunce, R.G.H. - \ 2012
Land Use Policy 29 (2012)3. - ISSN 0264-8377 - p. 473 - 482.
stratification - exploration
The role that the agricultural sector plays in rural areas has considerably changed in the last five decades, and is reflected in a major shift towards multi-dimensional, multi-sectoral land use. Existing European rural typologies are mostly one-dimensional, based on a rather coarse administrative scale data and are unable to define adequately the diversity of the regions involved. The rural typology presented in this paper has been produced as a response to a new policy need for typologies addressing the diversity in regional rurality. This paper describes the method developed and explores the relevance of the results for future rural policies. This new rural typology incorporates two dimensions identified by statistical screening of a range of geographical and socioeconomic data related to the territorial variation of European rural land. The use of high-resolution raster data at 1 km2 resolution provides large flexibility for the construction of individual classifications, with a variable number of classes for a variety of objectives. In the example presented, nine divisions were produced, which were subsequently summarised into three rural classes termed Peri-urban, Rural and Deep Rural. The rural typology enables the consistent identification of comparable rural areas and intergradations with urban land in the European territory, and describes the degree of generalisation that is possible. In addition, it provides a spatially explicit framework for scientific analysis and communication to both European policy makers and local stakeholders. --------------------------------------------------------------------------------
The Pan European Ecological Network: PEEN
Jongman, R.H.G. ; Bouwma, I.M. ; Griffioen, A.J. ; Walters, L.J. ; Doorn, A.M. van - \ 2011
Landscape Ecology 26 (2011)3. - ISSN 0921-2973 - p. 311 - 326.
stratification - greenways - habitats
The pan European biological and landscape diversity strategy (PEBDLS) was developed under the auspices of the Council of Europe in order to achieve the effective implementation of the convention of biological diversity (CBD) at the European level. A key element of PEBLDS has been the development of the Pan European Ecological Network (PEEN) as a guiding vision for coherence in biodiversity conservation. PEEN has been developed in three subprojects: Central and Eastern Europe, completed in 2002; South-eastern Europe, completed in 2006; and Western Europe, also completed in 2006. The methodology of the development of the three maps has been broadly comparable but data availability, differences in national databases, technical developments and geographical differences caused variations in the detailed approach. One of the challenges was to find common denominators for the habitat data in Europe; this was solved differently for the subprojects. The project has resulted in three maps that together constitute the PEEN. They differ in terms of ecological coherence and the need for ecological corridors; for example, in Central and Western Europe corridors are essential to provide connectivity, while in Northern, Eastern and South-eastern Europe larger, coherent natural areas still exist. The future steps in developing PEEN should include the implementation of national ecological networks and, in particular, the pursuit of international coherence through the development of trans-European ecological corridors. The big challenge is to develop a common approach among the over 100 European-wide agencies that are responsible for biodiversity conservation
An assessment of long term ecosystem research activities across European socio-ecological gradients
Metzger, M.J. ; Bunce, R.G.H. ; Eupen, M. van; Mirtl, M. - \ 2010
Journal of Environmental Management 91 (2010)6. - ISSN 0301-4797 - p. 1357 - 1365.
land-use change - stratification - vulnerability - habitats - science - lter
Integration of European long term ecosystem research (LTER) would provide important support for the management of the pan-European environment and ecosystems, as well as international policy commitments. This does require appropriate coverage of Europe and standardised frameworks and research methods between countries. Emerging interest in socio-ecological systems prompted the present assessment of the distribution of LTER activities across European socio-ecological gradients. This paper presents a European stratification with a 1 km(2) resolution, delineating 48 broad socio-ecological regions. The dataset is based on an existing biogeophysical stratification constructed using multivariate clustering of mainly climatic variables and a newly developed socio-economic stratification based on an economic density indicator. The coverage of European LTER facilities across the socio-ecological gradients is tested using this dataset. The analysis shows two strong biases in the present LTER effort. Firstly, urban and disturbed regions are consistently under-represented, illustrating a bias for traditional ecological research away from human activity. Secondly, the Mediterranean, for which some of the most extreme global change impacts are projected, is receiving comparatively little attention. Both findings can help guide future investment in the European LTER network - and especially in a Long Term Socio-Ecological Research (LTSER) component - to provide a more balanced coverage. This will provide better scientific understanding of pan-European environmental concerns and support the management of natural resources and international policy commitments in the European Union
Identity-by-Descent Matrix Decomposition Using Latent Ancestral Allele Models
Braak, C.J.F. ter; Boer, M.P. ; Totir, L. ; Winkler, C.R. ; Smith, O.S. ; Bink, M.C.A.M. - \ 2010
Genetics 185 (2010)3. - ISSN 0016-6731 - p. 1045 - 1057.
quantitative trait loci - population-structure - plant-populations - genotype data - association - stratification - prediction - regression - selection - markers
Genetic linkage and association studies are empowered by proper modeling of relatedness among individuals. Such relatedness can be inferred from marker and/or pedigree information. In this study, the genetic relatedness among n inbred individuals at a particular locus is expressed as an n x n square matrix Q. The elements of Q are identity-by-descent probabilities, that is, probabilities that two individuals share an allele descended from a common ancestor. In this representation the definition of the ancestral alleles and their number remains implicit. For human inspection and further analysis, an explicit representation in terms of the ancestral allele origin and the number of alleles is desirable. To this purpose, we decompose the matrix Q by a latent class model with K classes (latent ancestral alleles). Let P be an n x K matrix with assignment probabilities of n individuals to K classes constrained such that every element is nonnegative and each row sums to 1. The problem then amounts to approximating Q by PPT, while disregarding the diagonal elements. This is not an eigenvalue problem because of the constraints on P. An efficient algorithm for calculating P is provided. We indicate the potential utility of the latent ancestral allele model. For representative locus-specific Q matrices constructed for a set of maize inbreds, the proposed model recovered the known ancestry.
Trajectories of land use change in Europe: a model-based exploration of rural futures
Verburg, P.H. ; Berkel, D.B. van; Doorn, A.M. van; Eupen, M. van; Heiligenberg, H.A.R.M. van den - \ 2010
Landscape Ecology 25 (2010)2. - ISSN 0921-2973 - p. 217 - 232.
agricultural landscapes - mountain landscapes - adaptive capacity - areas - adaptation - scenarios - policies - stratification - consequences - netherlands
Land use change is characterized by a high diversity of change trajectories depending on the local conditions, regional context and external influences. Policy intervention aims to counteract the negative consequences of these changes and provide incentives for positive developments. Region typologies are a common tool to cluster regions with similar characteristics and possibly similar policy needs. This paper provides a typology of land use change in Europe at a high spatial resolution based on a series of different scenarios of land use change for the period 2000–2030. A series of simulation models ranging from the global to the landscape level are used to translate scenario conditions in terms of demographic, economic and policy change into changes in European land use pattern. A typology developed based on these simulation results identifies the main trajectories of change across Europe: agricultural abandonment, agricultural expansion and urbanization. The results are combined with common typologies of landscape and rurality. The findings indicate that the typologies based on current landscape and ruralities are poor indicators of the land use dynamics simulated for the regions. It is advocated that typologies based on (simulated) future dynamics of land change are more appropriate to identify regions with potentially similar policy needs
A new European Landscape Classification (LANMAP): A transparent, flexible and user-oriented methodology to distinguish landscapes
Mucher, C.A. ; Klijn, J.A. ; Wascher, D.M. ; Schaminée, J.H.J. - \ 2010
Ecological Indicators 10 (2010)1. - ISSN 1470-160X - p. 87 - 103.
land - stratification
We have developed a new hierarchical European Landscape Classification that can be used as a framework for, e.g., indicator reporting and environmental sampling. Landscapes are ecological meaningful units where many processes and components interact. And as such, landscapes themselves have resulted from long-term interactions of natural abiotic, biotic and anthropogenic processes. A good understanding of landscapes is essential for its assessment, protection, management and planning. An internationally consistent approach is therefore obligatory and the production of landscape classifications and associated maps is an important tool in this context. Although intuitive maps are available there are no consistent quantitative maps of European landscapes. In this paper, landscapes are regarded as forming recognizable parts of the earth's surface and as showing a characteristic ordering of elements. The complex nature of the underlying scientific concepts, which sometimes overlap and conflict, requires an objective and consistent methodology, as described in the present paper. As there are many regional differences in landscape properties, it is crucial to strike the right balance between reducing the inherent complexity and maintaining an adequate level of detail. Against this background, a European Landscape Map (LANMAP) has been produced, making use of available segmentation and classification techniques on high-resolution spatial data sets. LANMAP is a landscape classification of Pan-Europe with four hierarchical levels; using digital data on climate, altitude, parent material and land use as determinant factors; and has 350 landscape types at the most detailed level. At this level there are 14,000 mapping units with a minimum mapping unit of 11 km2. Thus far, LANMAP is limited to a biophysical approach, since there is a lack of consistent and European-wide data on cultural–historical factors. This paper describes the conceptual background of LANMAP, its methodology and results, and shows its potentials and limitations
Spatial distribution of grassland productivity and land use in Europe
Smit, H.J. ; Metzger, M.J. ; Ewert, F. - \ 2008
Agricultural Systems 98 (2008)3. - ISSN 0308-521X - p. 208 - 219.
landgebruik - landbouwgrond - graslanden - europese unie - klimaatverandering - grondproductiviteit - land use - agricultural land - grasslands - european union - climatic change - land productivity - silvopastoral system - future scenarios - northern greece - herbage mass - nitrogen - spain - quality - stratification - agriculture - efficiency
Grasslands are an important land use in Europe with essential functions for feed and ecosystem service supply. Impact assessment modelling of European agriculture and the environment needs to consider grasslands and requires spatially explicit information on grassland distribution and productivity, which is not available. This paper presents and analyses spatially explicit data of grassland productivity and land use across regions in Europe. Data are extracted from various regional, national and international census statistics for Europe, extending eastwards to the Ural Mountains. Regional differences in grassland productivity are analysed considering selected climatic and agronomic parameters and are compared with the remotely sensed normalised difference vegetation index (NDVI) and simulations from two impact assessment models. Temporal productivity changes are investigated for selected regions. As grassland is mainly used for animal feed stuff, the spatial distribution of milk productivity is also analyzed. Results show large regional differences in grassland productivity and land use in Europe. Grassland productivity is highly correlated with annual precipitation and less with annual temperature sum and growing season length. The correlation with NDVI is low. Comparison with large-scale simulations from two different models reveal that simulated spatial patterns of grassland productivity differ from the data obtained in this study, which may be attributable to the under-representation of management effects in these models. Grassland productivity has increased in recent decades, but the average annual genetic gain is different between temporary (0.5%) and permanent grassland (0.25%). The spatial pattern of milk productivity across Europe is similar to the productivity of grassland, suggesting that grassland productivity plays a major role in the distribution of milk productivity. The dataset described in this paper extends the present understanding of the spatial distribution and temporal changes in grassland productivity and land use in Europe. The dataset forms a suitable basis for evaluating large-scale (grassland) productivity models, for which observed data are scarce. However, the definition of grasslands and the collection of data across European countries need to be more consistent and standardised to improve the quality of European grassland productivity and land use data.
Projected environmental shifts under climate change: European trends and regional impacts
Metzger, M.J. ; Bunce, R.G.H. ; Leemans, R. ; Viner, D. - \ 2008
Environmental Conservation 35 (2008)1. - ISSN 0376-8929 - p. 64 - 75.
species distributions - great-britain - global change - scenarios - stratification - vulnerability - conservation - policy - model - scale
Potential impacts of climate change on ecosystems and the environment are generally assessed by summarizing climate change scenarios for broad regions (for example countries), or by specific modelling exercises. This paper presents an alternative approach for summarizing climate change impacts on the European environment, by linking climate change scenarios to recognized environmental divisions. Sixteen climate scenarios from four general circulation models were therefore linked to 84 statistically derived strata sharing common environmental features. In this way, the future distribution of the strata, as defined by their climate characteristics, were quantified and mapped. The results show that Europe is likely to experience major environmental shifts, with pronounced regional variations. As expected, environmental strata shift northwards. In particular the southern Mediterranean strata are projected to expand, whereas Atlantic environments remain much more stable. Alpine and Mediterranean mountain environments decline dramatically. However, the Scandinavian zones show no consistent pattern of change. More detailed analysis of four sample regions shows that the impacts of the projected shifts will largely depend on regional characteristics. Environmental conservation, regional assessments and scenario development could therefore be facilitated by combining relevant regional datasets (for example for vegetation, land cover and species distribution) with the shifting environmental strata
A spatially explicit and quantitative vulnerability assessment of ecosystem service change in Europe
Metzger, M.J. ; Schröter, D. ; Leemans, R. ; Cramer, W. - \ 2008
Regional Environmental Change 8 (2008)3. - ISSN 1436-3798 - p. 91 - 107.
land-use change - global change - climate-change - stratification - environment - scenarios - dynamics - carbon
Environmental change alters ecosystem functioning and may put the provision of services to human at risk. This paper presents a spatially explicit and quantitative assessment of the corresponding vulnerability for Europe, using a new framework designed to answer multidisciplinary policy relevant questions about the vulnerability of the human-environment system to global change. Scenarios were constructed for a range of possible changes in socio-economic trends, land uses and climate. These scenarios were used as inputs in a range of ecosystem models in order to assess the response of ecosystem function as well as the changes in the services they provide. The framework was used to relate the impacts of changing ecosystem service provision for four sectors in relation to each other, and to combine them with a simple, but generic index for societal adaptive capacity. By allowing analysis of different sectors, regions and development pathways, the vulnerability assessment provides a basis for discussion between stakeholders and policymakers about sustainable management of Europe¿s natural resources
A standardized procedure for surveillance and monitoring European habitats and provision of spatial data
Bunce, R.G.H. ; Metzger, M.J. ; Jongman, R.H.G. ; Brandt, J. ; Blust, G. de; Elena-Rossello, R. ; Groom, G.B. ; Halada, L. ; Hofer, G. ; Howard, D.C. ; Kovár, P. ; Mücher, C.A. ; Padoa-Schioppa, E. ; Paelinx, D. ; Palo, A. ; Pérez-Soba, M. ; Ramos, I.L. ; Roche, P. ; Skånes, H. ; Wrbka, T. - \ 2008
Landscape Ecology 23 (2008)1. - ISSN 0921-2973 - p. 11 - 25.
strategic ecological survey - land-cover - stratification - classification - biodiversity - principles - britain
Both science and policy require a practical, transmissible, and reproducible procedure for surveillance and monitoring of European habitats, which can produce statistics integrated at the landscape level. Over the last 30 years, landscape ecology has developed rapidly, and many studies now require spatial data on habitats. Without rigorous rules, changes from baseline records cannot be separated reliably from background noise. A procedure is described that satisfies these requirements and can provide consistent data for Europe, to support a range of policy initiatives and scientific projects. The methodology is based on classical plant life forms, used in biogeography since the nineteenth century, and on their statistical correlation with the primary environmental gradient. Further categories can therefore be identified for other continents to assist large scale comparisons and modelling. The model has been validated statistically and the recording procedure tested in the field throughout Europe. A total of 130 General Habitat Categories (GHCs) is defined. These are enhanced by recording environmental, site and management qualifiers to enable flexible database interrogation. The same categories are applied to areal, linear and point features to assist recording and subsequent interpretation at the landscape level. The distribution and change of landscape ecological parameters, such as connectivity and fragmentation, can then be derived and their significance interpreted.
Towards a spatially explicit and quantitative vulnerability assessment of environmental change in Europe
Metzger, M.J. ; Schröter, D. - \ 2006
Regional Environmental Change 6 (2006)4. - ISSN 1436-3798 - p. 201 - 216.
sustainability science - land classification - future scenarios - climate-change - global change - ecosystems - impacts - stratification - framework - systems
Over the next century, society will increasingly be confronted with the impacts of global change (e.g. pollution, land use changes, and climate change). Multiple scenarios provide us with a range of possible changes in socio-economic trends, land uses and climate (i.e. exposure) and allow us to assess the response of ecosystems and changes in the services they provide (i.e. potential impacts). Since vulnerability to global change is less when society is able to adapt, it is important to provide decision makers with tools that will allow them to assess and compare the vulnerability of different sectors and regions to global change, taking into account exposure and sensitivity, as well as adaptive capacity. This paper presents a method that allows quantitative spatial analyses of the vulnerability of the human-environment system on a European scale. It is a first step towards providing stakeholders and policy makers with a spatially explicit portfolio of comparable projections of ecosystem services, providing a basis for discussion on the sustainable management of Europe's natural resources
Europese bedrijven professionaliseren geconditioneerde stratificatie
Derkx, M.P.M. ; Jensen, M. - \ 2005
De Boomkwekerij 18 (2005)2. - ISSN 0923-2443 - p. 14 - 16.
houtachtige planten als sierplanten - zaden - stratificatie (zaden) - voorkieming - kiemrust - zaadvochtigheid - boomteelt - onderzoeksprojecten - europa - ornamental woody plants - seeds - stratification - pregermination - seed dormancy - seed moisture - arboriculture - research projects - europe
Boomkwekerijen, onderzoeksinstituten en zaadbedrijven uit heel Europa werken samen om het geconditioneerde stratificeren van boomzaden in de vingers te krijgen. Bij veel zaadsoorten lukt dat inmiddels heel goed
Gibberellins and the cold requirement of tulip
Rebers, M. - \ 1994
Agricultural University. Promotor(en): L.H.W. van der Plas; E. Knegt. - S.l. : Rebers - ISBN 9789054853237 - 121
liliaceae - bloembollen - gibberellinen - zaden - stratificatie (zaden) - groei - tulipa - kou - ornamental bulbs - gibberellins - seeds - stratification - growth - cold
<p>Tulip bulbs <em>(Tulipa gesneriana</em> L.), <em></em> with terminal buds containing a complete flower, require a period of low temperature to prepare the bud for floral stalk elongation and full flower development at subsequent higher temperatures. For the cultivar Apeldoorn, a dry- storage treatment of 12 weeks at 5°C prior to planting at 20°C, win lead to proper floral stalk elongation and full flower development. Shorter periods at 5°C usually result in slower shoot elongation and delayed flowering. Without any cold treatment, the growth of the shoot is strongly reduced and often flower abortion occurs. In these processes, the involvement of gibberellins (GAs) has been implicated, because application of GAs could partly replace the cold treatment. In addition, GA biosynthesis inhibitors could reduce the floral stalk elongation of cold-treated bulbs and this effect was reversed by simultaneous application of GA.<p>In horticultural practice, there is a need for a practical assay to test whether a particular bulb has received a proper cold treatment. The amount of GAs or of one particular GA, might provide a suitable parameter in a test for properly cold-treated bulbs.<p>In this study, the role of GAs in the cold requirement of tulip was investigated by analysing the GA levels in cooled and noncooled tulip bulbs, and by studying the effect and metabolism of applied GAs in combination with a' GA biosynthesis inhibitor.<p>An inventory was made of GAs, in sprouts of cooled (12 weeks 5°C) and noncooled bulbs (12 weeks 17°C) (chapter 3). By combined gas chromatography-mass spectrometry (GC-MS) and GC-selected ion monitoring (SIM), GA <sub><font size="-2">1</font></sub> , GA <sub><font size="-2">4</font></sub> , GA <sub><font size="-2">9</font></sub> , GA <sub><font size="-2">12</font></sub> , GA <sub><font size="-2">24</font></sub> , GA <sub><font size="-2">34</font></sub> and three GA-related compounds were detected. They all occurred in sprouts of both cooled and noncooled bulbs. Most of them were found in the conjugated form as well. Among these GAs, GA <sub><font size="-2">4</font></sub> and/or GA <sub><font size="-2">1</font></sub> might be the active forms, the others being precursors (GA <sub><font size="-2">9</font></sub> , GA <sub><font size="-2">12</font></sub> , and GA <sub><font size="-2">24</font></sub> ), or an inactivation product (GA <sub><font size="-2">34</font></sub> ).<p>Using GC-SIM and deuterated GAs as internal standards, the changes in endogenous GA levels were measured in sprouts and basal plates during cooled and noncooled bulb storage, as well as after planting these bulbs (chapter 4). GA <sub><font size="-2">4</font></sub> and GA <sub><font size="-2">24</font></sub> were the major occurring gibberellins, with levels up to ca. 10 ng per sprout or basal plate. GA <sub><font size="-2">1</font></sub> , GA <sub><font size="-2">9</font></sub> and GA <sub><font size="-2">34</font></sub> were present in much lower amounts. The levels of GA <sub><font size="-2">12</font></sub> and of the GA conjugates and GA-related compounds were not analysed.<p>During bulb storage, the level of GA <sub><font size="-2">4</font></sub> per sprout increased, especially in noncooled bulbs. After 12 weeks, these sprouts contained more GA <sub><font size="-2">4</font></sub> and also more GA <sub><font size="-2">1</font></sub> than cooled sprouts. However, sprouts in noncooled bulbs did hardly show any development after planting and it is unlikely that the increased level at the end of bulb storage is correlated with floral stalk elongation at subsequent higher temperatures. In the basal plates no significant changes occurred in the GA levels during storage. Therefore, the GA content in sprouts or basal plates at the end of bulb storage, cannot be used as marker in a test for properly cold-treated bulbs.<p>After planting cooled bulbs, the sprouts started to grow and within the first 11 days the level of GA <sub><font size="-2">4</font></sub> in the floral sulks increased. In planted noncooled bulbs, sprout growth was negligible and an increase in the level of GA <sub><font size="-2">4</font></sub> did not occur.<p>The biological activity of GA <sub><font size="-2">1</font></sub> , GA <sub><font size="-2">4</font></sub> and GA <sub><font size="-2">9</font></sub> , was tested on isolated sprouts, cultivated on a liquid medium <em>in vitro</em> (chapter 5). To compare the sensitivity to exogenous GAs, sprouts from both cooled and noncooled bulbs were used. The growth retardant paclobutrazol was used to study the role of GA biosynthesis. The growth of these isolated sprouts, the response to GAs and the effect of paclobutrazol, appeared to be dependent not only on the pretreatment of the bulbs, but also on the time in the season that the sprouts were isolated and incubated.<p>At early starting dates of incubation, floral stalks from both cooled and noncooled bulbs hardly showed any elongation in the absence of exogenous GA. Paclobutrazol had no effect on floral stalk elongation, and the response to GAs of sprouts from cooled bulbs was greater than the response of sprouts from noncooled bulbs. At later starts, considerable floral stalk elongation already occurred without GA application. Paclobutrazol inhibited this floral stalk elongation, and the growth of sprouts from both cooled and noncooled bulbs was stimulated by GA application. The three tested GAs were not significantly different in stimulating floral stalk elongation. The effect of paclobutrazol. was reversed by simultaneous application of GA. The results of these <em>in vitro</em> experiments demonstrated that, although depending on the time of the year, sprouts from both cooled and noncooled bulbs are responsive to exogenous GAs. Moreover, sprouts from both bulb treatments are capable of GA biosynthesis. The increasing performance of the isolated sprouts when incubated at later starting dates, and the increasing effect of paclobutrazol on these sprouts, suggested an increase in the availability of precursors for the synthesis of GAs. Apparently, low temperatures as well as bulb storage itself enhance GA biosynthesis and GA sensitivity, and consequently floral stalk elongation after planting when conditions are favourable for growth.<p>The isolated sprouts did not develop a full-grown flower without the addition of GA. GA <sub><font size="-2">4</font></sub> was more effective than GA <sub><font size="-2">9</font></sub> in stimulating this flower development. GA <sub><font size="-2">1</font></sub> could also stimulate flower development, but was no more effective than GA <sub><font size="-2">4</font></sub> .<p>The activity of applied GA <sub><font size="-2">9</font></sub> might be due to its conversion to GA <sub><font size="-2">4</font></sub> . GA <sub><font size="-2">4</font></sub> on its turn, might have to be converted to GA <sub><font size="-2">1</font></sub> before becoming biologically active. The metabolism of applied GA <sub><font size="-2">9</font></sub> was studied, with the purpose to investigate whether tulip sprouts are able to metabolize GA <sub><font size="-2">9</font></sub> to biologically active GA <sub><font size="-2">4</font></sub> or GA <sub><font size="-2">1</font></sub> , and whether sprouts from cooled and noncooled bulbs show differences in GA metabolism (chapter 6). [ <sup><font size="-2">3</font></SUP>H]GA <sub><font size="-2">9</font></sub> and [ <sup><font size="-2">2</font></SUP>H]GA <sub><font size="-2">9</font></sub> were applied to isolated sprouts by injection into the floral stalk and the metabolites were analysed in the sprouts after 24 h. According to HPLC analyses, [ <sup><font size="-2">3</font></SUP>H]GA <sub><font size="-2">9</font></sub> was converted to GA <sub><font size="-2">4</font></sub> -like and GA <sub><font size="-2">34</font></sub> -like compounds. The labelled metabolites of [ <sup><font size="-2">2</font></SUP>H]GA <sub><font size="-2">9</font></sub> were identified by GC-SIM, which demonstrated the conversion of [ <sup><font size="-2">2</font></SUP>H]GA <sub><font size="-2">9</font></sub> to [ <sup><font size="-2">2</font></SUP>H]GA <sub><font size="-2">4</font></sub> and [ <sup><font size="-2">2</font></SUP>H]GA <sub><font size="-2">34</font></sub> . Sprouts from both cooled and noncooled bulbs were able to convert GA <sub><font size="-2">9</font></sub> to GA <sub><font size="-2">4</font></sub> and GA <sub><font size="-2">34</font></sub><em>in vitro</em> . No evidence was found for the production of labelled GA <sub><font size="-2">1</font></sub> .In the presence of prohexadione (BX-112), known for its inhibiting effect on 2- and 3β-hydroxylations of GAs, the formation of [ <sup><font size="-2">2</font></SUP>H] metabolites was less or absent.<p>In conclusion, there is no direct correlation between the cold-stimulated growth and a change in the endogenous GA status in sprouts or basal plates during cold bulb storage. Further, the sensitivity to GAs increases in cooled sprouts, but also noncooled sprouts are responsive to applied GAs, and GA sensitivity apparently is not limiting for the development of noncooled sprouts <em>in vitro</em> . After cooled bulb storage, GA biosynthesis is essential for floral stalk elongation to proceed. The increase in the level of GA <sub><font size="-2">4</font></sub> in the growing floral stalks of cooled bulbs, the response of isolated sprouts to GA <sub><font size="-2">4</font></sub> and the inability of isolated sprouts to produce detectable amounts of GA <sub><font size="-2">1</font></sub> from applied GA <sub><font size="-2">9</font></sub> , support the hypothesis that GA <sub><font size="-2">4</font></sub> is the major intrinsically active GA in the floral stalk elongation of tulip.
De invloed van pootgoedbehandelingen op het aantal stengels en knollen bij aardappelen = The influence of some methods of potato seed preparation during storage on number of stems and tubers of the subsequent crop
Bus, C.B. - \ 1992
Lelystad : PAGV (Verslag / Proefstation voor de Akkerbouw en de Groenteteelt in de Vollegrond nr. 140) - 50
desinfectie - pootaardappelen - zaadbehandeling - zaden - stratificatie (zaden) - disinfection - seed potatoes - seed treatment - seeds - stratification
Studies on germination and vigour of cabbage seeds = [Aspecten van de kieming van zaden van witte kool en savoiekool
Liou, T.D. - \ 1987
Agricultural University. Promotor(en): C.M. Karssen, co-promotor(en): H.L. Kraak. - S.l. : Liou - 101
brassica oleracea - koolsoorten - karakteristieken - plantenvermeerdering - zaadcontrole - zaden - sporen - stratificatie (zaden) - cabbages - characteristics - propagation - seed testing - seeds - spores - stratification
<p>The effects of commercial storage of cabbage seeds on the germination of seeds and the emergence and growth of seedlings have been studied. Progressive ageing of seeds caused loss of seed vigour which resulted in poor emergence and growth of seedlings and the formation of abnormal seedlings. Loss of vigour was also observed indirectly in the controlled deterioration test (CD test) that speeds up the rate of ageing at controlled conditions. It was shown that the CD test gave the best indication of vigour loss. Low vigour seeds also differed from high vigour seeds in a more substantial loss of potassium ions during incubation in soil. Apart from seed vigour also soil conditions and other environmental factors influence the field performance that under certain atmospheric and soil conditions the best possible result is obtained.<p>Pre-incubation of cabbage seeds in osmotic solution clearly showed that several aspects of seed ageing are reversible. Pretreated seeds germinated earlier and faster and produced more normal seedlings than untreated seeds. The mechanism of osmotic pretreatment was studied. It 'is unlikely that such treatment favours the accumulation of osmotic constituents. The leakage of K <sup><font size="-2">+</font></SUP>was inhibited during osmotic incubation. Loss of vigour might be related to membrane damage.
Physiological analysis of methods to relieve dormancy of lettuce seeds
Weges, R. - \ 1987
Agricultural University. Promotor(en): C.M. Karssen. - S.l. : S.n. - 122
zaden - stratificatie (zaden) - lactuca sativa - slasoorten - kieming - zaadkieming - kiemrust - seeds - stratification - lettuces - germination - seed germination - seed dormancy
<p>Low maximum temperature of germination restricts the cultivation of a number of lettuce cultivars to temperate conditions. Pretreatments have been studied that increase the maximum germination temperature, which is characterized by the temperature for 50% germination (T <sub><font size="-1">50</font></sub> ). Pretreatment consists of pre-incubation, redesiccation and storage. Pre- incubation during 16 to 20 h at 15 °C in water increases T <sub><font size="-1">50</font></sub> with 4 to 10 °C, depending on cultivar. Redesiccation does not cause visible damage to seeds, as judged from the developing seedling, provided that germination has not started during pre-incubation. In cultivars with a high original T <sub><font size="-1">50</font></sub> redesiccation does not affect T <sub><font size="-1">50</font></sub> . However, if the original T <sub><font size="-1">50</font></sub> is low, redesiccation causes a drop of T <sub><font size="-1">50</font></sub> to values close to the original T <sub><font size="-1">50</font></sub> value. The effect of redesiccation is mainly determined by the final moisture content. Temperature and rate of drying are of minor importance in this respect. Pre-incubation in solutions of polyethylene glycol makes the seeds desiccation tolerant. Dehydration results in increased K <sup><font size="-1">+</font></SUP>leakage from isolated embryos, in contrast to intact seeds that do not leak due to K <sup><font size="-1">+</font></SUP>-impermeable endosperm cells. T <sub><font size="-1">50</font></sub> decreases during storage. The decrease of T <sub><font size="-1">50</font></sub> and the loss of seed viability show a similar positive relationship to temperature and moisture content during storage. Besides the rise of T <sub><font size="-1">50</font></sub> , pre-incubation at 15 °C also enhances the capacity of seeds to germinate at increasingly more negative osmotic potentials of the incubation medium (Ψπe). The effect is characterized by the minimal Ψπe of the incubation medium for 50% germination (Ψ <sub><font size="-1">50</font></sub> ). Pre-incubation at 30 °C has an opposite effect. The change of Ψ <sub><font size="-1">50</font></sub> does not correspond with a change in concentration of amino nitrogen compounds. Both actual water potential (Ψ) and osmotic potential (Ψπ), as determined with a psychrometer, are not correlated with changing Ψ <sub><font size="-1">50</font></sub> values. Calculations based on the general equation of hydraulic cell growth indicate that changes in T <sub><font size="-1">50</font></sub> are correlated with parallel changes in the yield threshold (Y) of turgor pressure. Changes in Y appear to occur mainly in the seed envelope.
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