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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    Duurzaamheid als leidraad voor roos : vervolg onderzoek Perfecte Roos: energiezuinig geteeld
    Gelder, Arie de; Warmenhoven, Mary ; Knaap, Edwin van der; Burg, Rick van der - \ 2016
    Bleiswijk : Wageningen UR Glastuinbouw (Rapport GTB 1412) - 50
    rozen - teelt onder bescherming - kasgewassen - glastuinbouw - duurzame landbouw - energiebesparing - elektriciteit - assimilatie - kunstlicht - kunstmatige verlichting - verlichting - koelen - meeldauw - geïntegreerde bestrijding - geïntegreerde plagenbestrijding - roses - protected cultivation - greenhouse crops - greenhouse horticulture - sustainable agriculture - energy saving - electricity - assimilation - artificial light - artificial lighting - lighting - cooling - mildews - integrated control - integrated pest management
    The project Sustainable rose cultivation aimed to achieve a sustainable and energy efficient rose cultivation by a controlled use of assimilation lighting, an optimum use of the cooling and an integrated control strategy for mildew. The production came to 320 stems.m-2 average weight 54 grams. The branch length and bud size varied through the season. There was no saving on electricity. There was a significant saving on heat. The improvement of the energy efficiency was totally determined by the reduction of the heat consumption. The light utilization efficiency was 2:44 g.mol-¹ and increased compared to the previous year. Cooling and forced ventilation had a positive effect on the stem elongation in the autumn. The installation with forced ventilation from above combined with the screen had a favourable effect on the climate, especially in the humidity control under a largely (95-98%) closed screen. The payback period of the investment in airconditioning is within 3 years.
    Understanding photosynthesis important for CO2-dosing and lighting : CAM-plants difficult to deal with
    Heuvelink, E. ; Kierkels, T. - \ 2016
    In Greenhouses : the international magazine for greenhouse growers 5 (2016)1. - ISSN 2215-0633 - p. 14 - 15.
    horticulture - greenhouse horticulture - carbon dioxide - dosage - cam pathway - illumination - photosynthesis - assimilation - kalanchoe - ornamental bromeliads - phalaenopsis - tuinbouw - glastuinbouw - kooldioxide - dosering - cam cyclus - belichting - fotosynthese - assimilatie - kalanchoe - bromelia's als sierplanten - phalaenopsis
    It used to be rare to come across plants that bind CO2 mainly at night: CAMplants. But it’s no longer an exception in the horticultural sector. Nowadays the best-selling pot plant in the Netherlands – phalaenopsis – belongs to this group. This then raises questions such as: When do CAM-plants behave according to the book and when don’t they? And when does it make sense to dose with CO2 and provide lighting?
    Minder blad in winter bij veel meer groente- én sierteeltgewassen mogelijk : Leo Oprel pleit voor denken vanuit de winter
    Kromwijk, Arca ; Gelder, Arie de - \ 2015
    horticulture - greenhouse horticulture - vegetable growing - ornamental horticulture - tomatoes - anthurium - leaf area - biomass - greenhouse experiments - assimilation - winter - energy saving

    Onderzoek met een relatief ‘kale’ tomatenplant gaf vorige winter verrassende resultaten: iets meer productie, iets minder gasverbruik. Dit jaar is een nieuwe proef ingezet. Maar waarom zo’n systeem alleen toepassen bij tomaat? Leo Oprel (Kas als Energiebron) ziet nog veel meer mogelijkheden, ook bij siergewassen. Hij gaat in discussie met de onderzoekers Arca Kromwijk en Arie de Gelder.

    Sturen op balans source en sink ingewikkelde zaak : temperatuur aanpassen aan de beschikbare straling
    Elings, A. ; Heuvelink, E. ; Kierkels, T. - \ 2015
    Onder Glas 2015 (2015)4. - p. 36 - 37.
    glastuinbouw - cultuurmethoden - teelt onder bescherming - lichtregiem - assimilatie - temperatuur - groenten - snijbloemen - plantenontwikkeling - energiebesparing - greenhouse horticulture - cultural methods - protected cultivation - light regime - assimilation - temperature - vegetables - cut flowers - plant development - energy saving
    ‘Met het licht meetelen’ is een bekend principe binnen Het Nieuwe Telen. Het betekent dat je de temperatuur aanpast aan het beschikbare licht. De insteek daarbij is vaak energiebesparing, maar ook vanuit plantkundig oogpunt is dat verstandig. Zo breng je source en sink meer in balans.
    Belichtingsapplicatie : rapportage tot Go/No Go moment
    Gelder, A. de - \ 2014
    Bleiswijk : Wageningen UR Glastuinbouw (Rapport / Wageningen UR Glastuinbouw 1331) - 26
    tuinbouw - kastechniek - glastuinbouw - rozen - belichting - assimilatie - fotosynthese - energiebesparing - internet - computer hardware - horticulture - greenhouse technology - greenhouse horticulture - roses - illumination - assimilation - photosynthesis - energy saving - internet - computer hardware
    In dit project wordt een belichtingsapplicatie ontwikkeld voor op internet waarmee tuinders op belichting kunnen besparen. Het model geeft op basis van de behoefte van de plant, bedrijfsspecifieke informatie en de weersverwachting een dagelijks advies over het gewenste aantal uren belichting.
    Belichting, CO2 en stuurlicht in de lelieteelt: een strategie voor energiebesparing
    Hogewoning, S.W. ; Trouwborst, G. ; Slootweg, G. ; Aanholt, J.T.M. van; Pot, C.S. ; Kok, B.J. - \ 2014
    Bunnik : Plant Lighting - 42
    glastuinbouw - lilium - cultuurmethoden - kooldioxide - dosering - belichting - assimilatie - plantenontwikkeling - groeistadia - lichtsterkte - effecten - greenhouse horticulture - lilium - cultural methods - carbon dioxide - dosage - illumination - assimilation - plant development - growth stages - light intensity - effects
    In de lelieteelt wordt langdurig belicht met een aanzienlijke intensiteit SON-T licht (6000-8000 lux ofwel ~78-104 μmol/m2s). Dit heeft een fors energieverbruik tot gevolg. Het doel van de belichting is (1) zwaardere takken, (2) remming van takstrekking (voorkomen slapheid), (3) verkorting van de teeltduur en (4) voorkomen van knopval en knopverdroging. CO2 dosering wordt niet toegepast in de lelieteelt. Eerder onderzoek van PPO heeft namelijk aangetoond dat CO2-dosering geen effect heeft op het takgewicht van Oriëntal-lelies en slechts een klein effect bij Longiflorums, Aziaten en LA-hybriden. Recent onderzoek door Plant Lighting en Plant Dynamics heeft echter aangetoond dat de fotosynthese van Oriëntals flink toeneemt bij aanvullend CO2. Dit is een schijnbare tegenstelling: Wel meer fotosynthese, maar niet meer takgewicht. Echter, mogelijk heeft lelie slechts een beperkte hoeveelheid assimilaten nodig voor een maximaal takgewicht en gaan extra aangemaakte assimilaten naar de bol. Als dat zo is, dan heeft CO2 dosering inderdaad geen zin bij voldoende belichting, maar wél bij lagere lichtniveaus. Daarom ligt aan dit onderzoek de volgende hoofdhypothese ten grondslag: Bij een suboptimale intensiteit belichting kan met CO2 dosering eenzelfde takgewicht gerealiseerd worden als bij een optimale lichtintensiteit zonder CO2 dosering.
    Optimal leaf area leads to higher production and higher income : Don't prune too many tomato leaves
    Heuvelink, E. ; Kierkels, T. - \ 2014
    In Greenhouses : the international magazine for greenhouse growers 3 (2014)2. - ISSN 2215-0633 - p. 52 - 53.
    glastuinbouw - solanum lycopersicum - plantenontwikkeling - bladoppervlakte - ontbladering - assimilatie - netto-assimilatiesnelheid - groenten - greenhouse horticulture - solanum lycopersicum - plant development - leaf area - defoliation - assimilation - net assimilation rate - vegetables
    Good light interception is the first step to good production. For that you need sufficient leaf area in the greenhouse. But it’s difficult for a grower to determine how much leaf surface area is present. Research is shedding new insight into this aspect.
    Belichtingsapplicatie; een tussenstand
    Gelder, A. de - \ 2014
    glastuinbouw - kasgewassen - belichting - assimilatie - zonne-instraling - lichtregiem - bedrijfsapplicaties - software-ontwikkeling - behoeftenbepaling - greenhouse horticulture - greenhouse crops - illumination - assimilation - insolation - light regime - business software - software engineering - needs assessment
    Assimilatiebelichting op basis van stralingsverwachting en behoefte van het gewas maakt de teler meer bewust van de belichtingsstrategie. Het doel van dit project is de bouw van een applicatie voor advies over belichtingsduur afgestemd op de assimilatenvraag van een gewas en besparing op energie vraag van 10 % voor belichting bij gebruik van de applicatie.
    Biosphere model simulations of interannual variability in terrestrial 13C/12C exchange.
    Velde, I.R. van der; Miller, J.B. ; Schaefer, K. ; Masarie, K.A. ; Denning, S. ; White, J.W.C. ; Krol, M.C. ; Peters, W. ; Tans, P.P. - \ 2013
    Global Biogeochemical Cycles 27 (2013)3. - ISSN 0886-6236 - p. 637 - 649.
    carbon-isotope discrimination - ocean co2 sink - stomatal conductance - c-13 discrimination - atmospheric co2 - cycle - climate - fires - photosynthesis - assimilation
    Previous studies suggest that a large part of the variability in the atmospheric ratio of (CO2)-C-13/(12)CO(2)originates from carbon exchange with the terrestrial biosphere rather than with the oceans. Since this variability is used to quantitatively partition the total carbon sink, we here investigate the contribution of interannual variability (IAV) in biospheric exchange to the observed atmospheric C-13 variations. We use the Simple Biosphere - Carnegie-Ames-Stanford Approach biogeochemical model, including a detailed isotopic fractionation scheme, separate C-12 and C-13 biogeochemical pools, and satellite-observed fire disturbances. This model of (CO2)-C-12 and (CO2)-C-13 thus also produces return fluxes of (13)CO(2)from its differently aged pools, contributing to the so-called disequilibrium flux. Our simulated terrestrial C-13 budget closely resembles previously published model results for plant discrimination and disequilibrium fluxes and similarly suggests that variations in C-3 discrimination and year-to-year variations in C(3)and C-4 productivity are the main drivers of their IAV. But the year-to-year variability in the isotopic disequilibrium flux is much lower (1 sigma=1.5PgCyr(-1)) than required (12.5PgCyr(-1)) to match atmospheric observations, under the common assumption of low variability in net ocean CO2 fluxes. This contrasts with earlier published results. It is currently unclear how to increase IAV in these drivers suggesting that SiBCASA still misses processes that enhance variability in plant discrimination and relative C-3/C(4)productivity. Alternatively, C-13 budget terms other than terrestrial disequilibrium fluxes, including possibly the atmospheric growth rate, must have significantly different IAV in order to close the atmospheric C-13 budget on a year-to-year basis.
    How much CO was emitted by the 2010 fires around Moscow?
    Krol, M.C. ; Peters, W. ; Hooghiemstra, P. ; George, M. ; Clerbaux, C. ; Hurtmans, D. ; McInerney, D. ; Sedano, F. ; Bergamaschi, P. ; Hajj, M. El; Kaiser, J.W. ; Fisher, D. ; Yeshov, V. ; Muller, J.P. - \ 2013
    Atmospheric Chemistry and Physics 13 (2013). - ISSN 1680-7316 - p. 4737 - 4747.
    russian wildfires - emissions - pollution - summer - iasi - assimilation - retrieval - satellite - algorithm - transport
    The fires around Moscow in July and August 2010 emitted a large amount of pollutants to the atmosphere. Here we estimate the carbon monoxide (CO) source strength of the Moscow fires in July and August by using the TM5-4DVAR system in combination with CO column observations of the Infrared Atmospheric Sounding Interferometer (IASI). It is shown that the IASI observations provide a strong constraint on the total emissions needed in the model. Irrespective of the prior emissions used, the optimised CO fire emission estimates from mid-July to mid-August 2010 amount to approximately 24 TgCO. This estimate depends only weakly (<15 %) on the assumed diurnal variations and injection height of the emissions. However, the estimated emissions might depend on unaccounted model uncertainties such as vertical transport. Our emission estimate of 22-27 TgCO during roughly one month of intense burning is less than suggested by another recent study, but substantially larger than predicted by the bottom-up inventories. This latter discrepancy suggests that bottom-up emission estimates for extreme peat burning events require improvements.
    Respiration is necessary for growth and maintenance : growth rate is ten times higher in summer than in winter
    Heuvelink, E. - \ 2013
    In Greenhouses : the international magazine for greenhouse growers 2 (2013)1. - ISSN 2215-0633 - p. 40 - 41.
    glastuinbouw - snijbloemen - sierteelt - plantenontwikkeling - assimilatie - plantenfysiologie - gesloten systemen - seizoengroei - greenhouse horticulture - cut flowers - ornamental horticulture - plant development - assimilation - plant physiology - closed systems - seasonal growth
    Does respiration divert energy away from production or does it lead to more production? The answer is both. Steering plant growth based on respiration is very complicated. However, in a closed greenhouse is should be possible to better control the maintenance respiration.
    What eddy-covariance measurements tell us about prior land flux errors in co 2-flux inversion schemes
    Chevallier, F. ; Wang, T. ; Ciais, P. ; Maignan, F. ; Bocquet, M. ; Moors, E.J. - \ 2012
    Global Biogeochemical Cycles 26 (2012)1. - ISSN 0886-6236 - 9 p.
    carbon-dioxide exchange - interannual variability - soil respiration - atmospheric co2 - pine forests - water-vapor - oak forest - assimilation - uncertainty - grassland
    To guide the future development of CO2-atmospheric inversion modeling systems, we analyzed the errors arising from prior information about terrestrial ecosystem fluxes. We compared the surface fluxes calculated by a process-based terrestrial ecosystem model with daily averages of CO2flux measurements at 156 sites across the world in the FLUXNET network. At the daily scale, the standard deviation of the model-data fit was 2.5 gC·m-2·d-1; temporal autocorrelations were significant at the weekly scale (>0.3 for lags less than four weeks), while spatial correlations were confined to within the first few hundred kilometers (
    Observation uncertainty of satellite soil moisture products determined with physically-based modeling
    Wanders, N. ; Karssenberg, D. ; Bierkens, M.F.P. ; Parinussa, R. ; Jeu, R. de; Dam, J.C. van; Jong, S. de - \ 2012
    Remote Sensing of Environment 127 (2012). - ISSN 0034-4257 - p. 341 - 356.
    passive microwave measurements - improving runoff prediction - vegetation optical depth - ers scatterometer - amsr-e - retrieval - assimilation - validation - algorithm - index
    Accurate estimates of soil moisture as initial conditions to hydrological models are expected to greatly increase the accuracy of flood and drought predictions. As in-situ soil moisture observations are scarce, satellite-based estimates are a suitable alternative. The validation of remotely sensed soil moisture products is generally hampered by the difference in spatial support of in-situ observations and satellite footprints. Unsaturated zone modeling may serve as a valuable validation tool because it could bridge the gap of different spatial supports. A stochastic, distributed unsaturated zone model (SWAP) was used in which the spatial support was matched to these of the satellite soil moisture retrievals. A comparison between point observations and the SWAP model was performed to enhance understanding of the model and to assure that the SWAP model could be used with confidence for other locations in Spain. A timeseries analysis was performed to compare surface soil moisture from the SWAP model to surface soil moisture retrievals from three different microwave sensors, including AMSR-E, SMOS and ASCAT. Results suggest that temporal dynamics are best captured by AMSR-E and ASCAT resulting in an averaged correlation coefficient of 0.68 and 0.71, respectively. SMOS shows the capability of capturing the long-term trends, however on short timescales the soil moisture signal was not captured as well as by the other sensors, resulting in an averaged correlation coefficient of 0.42. Root mean square errors for the three sensors were found to be very similar (± 0.05 m3m- 3). The satellite uncertainty is spatially correlated and distinct spatial patterns are found over Spain.
    Generating spatial precipitation ensembles: impact of temporal correlation structure
    Rakovec, O. ; Hazenberg, P. ; Torfs, P.J.J.F. ; Weerts, A.H. ; Uijlenhoet, R. - \ 2012
    Hydrology and Earth System Sciences 16 (2012)9. - ISSN 1027-5606 - p. 3419 - 3434.
    distributed hydrological model - radar rainfall estimation - ourthe catchment - real - bias - assimilation - resolution - region
    Sound spatially distributed rainfall fields including a proper spatial and temporal error structure are of key interest for hydrologists to force hydrological models and to identify uncertainties in the simulated and forecasted catchment response. The current paper presents a temporally coherent error identification method based on time-dependent multivariate spatial conditional simulations, which are conditioned on preceding simulations. A sensitivity analysis and real-world experiment are carried out within the hilly region of the Belgian Ardennes. Precipitation fields are simulated for pixels of 10 km x 10 km resolution. Uncertainty analyses in the simulated fields focus on (1) the number of previous simulation hours on which the new simulation is conditioned, (2) the advection speed of the rainfall event, (3) the size of the catchment considered, and (4) the rain gauge density within the catchment. The results for a sensitivity analysis show for typical advection speeds > 20 km h(-1), no uncertainty is added in terms of across ensemble spread when conditioned on more than one or two previous hourly simulations. However, for the real-world experiment, additional uncertainty can still be added when conditioning on a larger number of previous simulations. This is because for actual precipitation fields, the dynamics exhibit a larger spatial and temporal variability. Moreover, by thinning the observation network with 50 %, the added uncertainty increases only slightly and the cross-validation shows that the simulations at the unobserved locations are unbiased. Finally, the first-order autocorrelation coefficients show clear temporal coherence in the time series of the areal precipitation using the time-dependent multivariate conditional simulations, which was not the case using the time-independent univariate conditional simulations. The presented work can be easily implemented within a hydrological calibration and data assimilation framework and can be used as an improvement over currently used simplistic approaches to perturb the interpolated point or spatially distributed precipitation estimates.
    Bloei-inductie bij Chrysant onder lange dag : toepassing van LED-licht technologie
    Ieperen, W. van; Hogewoning, S.W. ; Dam, E. ten - \ 2011
    Wageningen : Wageningen Universiteit, Leerstoelgroep Tuinbouwketens - 23
    tuinbouw - glastuinbouw - chrysanthemum - led lampen - klimaatkamerproeven - fotoperiode - bloei-inductie - assimilatie - potplanten - snijbloemen - teeltsystemen - lichtregiem - horticulture - greenhouse horticulture - chrysanthemum - led lamps - growth chamber experiments - photoperiod - flower induction - assimilation - pot plants - cut flowers - cropping systems - light regime
    Deze publicatie beschrijft een onderzoek naar daglengte verlenging tijdens de korte dag bij chrysant met behoud van bloei door sturing met speciale LED belichting. In klimaatkamerproeven met LEDs (zonder natuurlijk licht) kon bij Chrysant bloemknopaanleg worden geïnduceerd onder een lange dag (LD), door de laatste paar uur van de lichtperiode alleen blauw LED-licht te geven. De rest van de lichtperiode werd een combinatie van rood en blauw LED-licht gegeven. Omdat blauw licht fotosynthetisch actief is leverde dit aanzienlijke extra groei op. Echter, wanneer overdag natuurlijk zonlicht of kunstlicht met een zonlichtspectrum werd gegeven, bleek het doorbelichten met blauw LED-licht niet te resulteren in bloei. Langdurig blauw LED-licht kan dus niet zondermeer worden toegepast in de commerciële teelt van pot- en snijchrysant in kassen. Voor toekomstige meerlagen- en andere teeltsystemen zonder natuurlijk licht is het wel een optie. Deze experimenten laten voor het eerst zien dat ook de spectrale samenstelling van het licht overdag invloed heeft op de bloei-inductie bij chrysant.
    A comparison of different inverse carbon flux estimation approaches for application on a regional domain
    Tolk, L.F. ; Dolman, A.J. ; Meesters, A.G.C.A. ; Peters, W. - \ 2011
    Atmospheric Chemistry and Physics 11 (2011). - ISSN 1680-7316 - p. 10349 - 10365.
    atmospheric transport - dioxide exchange - european forests - modeling system - surface fluxes - boundary-layer - co2 fluxes - assimilation - sensitivity - tower
    We have implemented six different inverse carbon flux estimation methods in a regional carbon dioxide (CO2) flux modeling system for the Netherlands. The system consists of the Regional Atmospheric Mesoscale Modeling System (RAMS) coupled to a simple carbon flux scheme which is run in a coupled fashion on relatively high resolution (10 km). Using an Ensemble Kalman filter approach we try to estimate spatiotemporal carbon exchange patterns from atmospheric CO2 mole fractions over the Netherlands for a two week period in spring 2008. The focus of this work is the different strategies that can be employed to turn first-guess fluxes into optimal ones, which is known as a fundamental design choice that can affect the outcome of an inversion significantly. Different state-of-the-art approaches with respect to the estimation of net ecosystem exchange (NEE) are compared quantitatively: (1) where NEE is scaled by one linear multiplication factor per land-use type, (2) where the same is done for photosynthesis (GPP) and respiration (R) separately with varying assumptions for the correlation structure, (3) where we solve for those same multiplication factors but now for each grid box, and (4) where we optimize physical parameters of the underlying biosphere model for each land-use type. The pattern to be retrieved in this pseudo-data experiment is different in nearly all aspects from the first-guess fluxes, including the structure of the underlying flux model, reflecting the difference between the modeled fluxes and the fluxes in the real world. This makes our study a stringent test of the performance of these methods, which are currently widely used in carbon cycle inverse studies. Our results show that all methods struggle to retrieve the spatiotemporal NEE distribution, and none of them succeeds in finding accurate domain averaged NEE with correct spatial and temporal behavior. The main cause is the difference between the structures of the first-guess and true CO2 flux models used. Most methods display overconfidence in their estimate as a result. A commonly used daytime-only sampling scheme in the transport model leads to compensating biases in separate GPP and R scaling factors that are readily visible in the nighttime mixing ratio predictions of these systems. Overall, we recommend that the estimate of NEE scaling factors should not be used in this regional setup, while estimating bias factors for GPP and R for every grid box works relatively well. The biosphere parameter inversion performs good compared to the other inversions at simultaneously producing space and time patterns of fluxes and CO2 mixing ratios, but non-linearity may significantly reduce the information content in the inversion if true parameter values are far from the prior estimate. Our results suggest that a carefully designed biosphere model parameter inversion or a pixel inversion of the respiration and GPP multiplication factors are from the tested inversions the most promising tools to optimize spatiotemporal patterns of NEE.
    How plant architecture affects light absorption and photosynthesis in tomato: towards an ideotype for plant architecture using a functional-structural plant model
    Sarlikioti, V. ; Visser, P.H.B. de; Buck-Sorlin, G.H. ; Marcelis, L.F.M. - \ 2011
    Annals of Botany 108 (2011)6. - ISSN 0305-7364 - p. 1065 - 1073.
    carbon gain - leaf - interception - canopy - morphology - yield - assimilation - efficiency - avoidance - capture
    Background and Aims - Manipulation of plant structure can strongly affect light distribution in the canopy and photosynthesis. The aim of this paper is to find a plant ideotype for optimization of light absorption and canopy photosynthesis. Using a static functional structural plant model (FSPM), a range of different plant architectural characteristics was tested for two different seasons in order to find the optimal architecture with respect to light absorption and photosynthesis. Methods - Simulations were performed with an FSPM of a greenhouse-grown tomato crop. Sensitivity analyses were carried out for leaf elevation angle, leaf phyllotaxis, leaflet angle, leaf shape, leaflet arrangement and internode length. From the results of this analysis two possible ideotypes were proposed. Four different vertical light distributions were also tested, while light absorption cumulated over the whole canopy was kept the same. Key Results Photosynthesis was augmented by 6 % in winter and reduced by 7 % in summer, when light absorption in the top part of the canopy was increased by 25 %, while not changing light absorption of the canopy as a whole. The measured plant structure was already optimal with respect to leaf elevation angle, leaflet angle and leaflet arrangement for both light absorption and photosynthesis while phyllotaxis had no effect. Increasing the length : width ratio of leaves by 1·5 or increasing internode length from 7 cm to 12 cm led to an increase of 6–10 % for light absorption and photosynthesis. Conclusions - At high light intensities (summer) deeper penetration of light in the canopy improves crop photosynthesis, but not at low light intensities (winter). In particular, internode length and leaf shape affect the vertical distribution of light in the canopy. A new plant ideotype with more spacious canopy architecture due to long internodes and long and narrow leaves led to an increase in crop photosynthesis of up to 10 %.
    Lichtmeetprotocol : lichtmetingen in onderzoekskassen meet LED en SON-T belichting
    Dueck, T.A. ; Pot, S. - \ 2010
    Wageningen : Wageningen UR Glastuinbouw/Plant Dynamics and Wageningen Universiteit (Rapport / Wageningen UR Glastuinbouw nr. 302) - 14
    lichtgevende dioden - glastuinbouw - assimilatie - belichting - protocollen - meting - led lampen - light emitting diodes - greenhouse horticulture - assimilation - illumination - protocols - measurement - led lamps
    Gedurende de laatste jaren is er in lichtonderzoek projecten een nieuw fenomeen ontstaan, t.w. de introductie van LEDs als assimilatie belichting in de glastuinbouw. Naar aanleiding daarvan heeft LNV en Productschap Tuinbouw in het kader van Kas als Energiebron opdracht gegeven aan WUR Glastuinbouw om een protocol te schrijven voor het meten van licht in SON-T en LED belichtingsystemen in onderzoekskassen. WUR Glastuinbouw heeft dit meetprotocol opgesteld in samenwerking met Plant Dynamics en WU Tuinbouwproductieketens. Dit protocol is vervolgens besproken en vastgesteld in een platform met Philips, Lemnis Lighting, Hortilux, KEMA en TNO.
    Space-time geostatistics for geography: a case study of radiation monitoring across parts of Germany
    Heuvelink, G.B.M. ; Griffith, D.A. - \ 2010
    Geographical Analysis 42 (2010)2. - ISSN 0016-7363 - p. 161 - 179.
    spatiotemporal covariance-models - optimization - assimilation - variogram
    Many branches within geography deal with variables that vary not only in space but also in time. Therefore, conventional geostatistics needs to be extended with methods that estimate and quantify spatiotemporal variation and use it in spatiotemporal interpolation and stochastic simulation. This article briefly summarizes the main concepts of space–time geostatistics. Kriging in space and time can be done in much the same way as it is in a purely spatial setting. The main difficulties are in defining a realistic stochastic model that is assumed to have generated data and in characterizing and estimating the space–time correlation of that model. This article uses a model-based geostatistical approach to characterize space–time variability. The space–time variable of interest is treated as a sum of independent stationary spatial, temporal, and spatiotemporal components, which leads to a sum-metric space–time variogram model. Methods are illustrated with a case study of space–time interpolation of monthly averages of detected background radiation for a 5-year period in four German states.
    40 kg Paprika
    Eveleens-Clark, B.A. ; Lagas, P. ; Driever, S.M. ; Zwinkels, J. ; Vaate, J. Bij de; Kaarsemaker, R.C. - \ 2010
    Bleiswijk/Wageningen/Delfgauw : Wageningen UR Glastuinbouw/DLV Plant/Groen Agro Control - 87
    capsicum - gewasproductie - productiegroei - glasgroenten - tuinbouw - assimilatie - groeimodellen - teeltsystemen - brix - diffuus glas - snoeien - teelt in rijen - capsicum - crop production - production growth - greenhouse vegetables - horticulture - assimilation - growth models - cropping systems - brix - diffused glass - pruning - alley cropping
    Rapport beBestaand uit de volgende onderdelen: 1. Een kasproef, waarin het doel was de productie te verhogen door een combinatie van maatregelen; diffuus glas, verneveling en gewashandelingen 2. Praktijktoepassing en ontwikkeling van een plantmodel dat zetting voorspelt 3. Toetsing van een nieuwe methode om beschikbaarheid van assimilaten voor zetting te meten
    Differences in photosynthetic behaviour and leaf senescence of soybean (Glycine max [L.] Merrill) dependent on N fixation or nitrate supply
    Kaschuk, G. ; Hungria, M. ; Leffelaar, P.A. ; Giller, K.E. ; Kuyper, T.W. - \ 2010
    Plant Biology 12 (2010)1. - ISSN 1435-8603 - p. 60 - 69.
    nitrogen-fixation - pod removal - sink removal - c-3 plants - seed yield - leaves - field - accumulation - assimilation - metabolism
    Biological N2 fixation can fulfil the N demand of legumes but may cost as much as 14% of current photosynthate. This photosynthate (C) sink strength would result in loss of productivity if rates of photosynthesis did not increase to compensate for the costs. We measured rates of leaf photosynthesis, concentrations of N, ureides and protein in leaves of two soybean cultivars (Glycine max [L.] Merrill) differing in potential shoot biomass production, either associated with Bradyrhizobium japonicum strains, or amended with nitrate. Our results show that the C costs of biological N2 fixation can be compensated by increased photosynthesis. Nodulated plants shifted N metabolism towards ureide accumulation at the start of the reproductive stage, at which time leaf N concentration of nodulated plants was greater than that of N-fertilized plants. The C sink strength of N2 fixation increased photosynthetic N use efficiency at the beginning of plant development. At later stages, although average protein concentrations were similar between the groups of plants, maximum leaf protein of nodulated plants occurred a few days later than in N-fertilized plants. The chlorophyll content of nodulated plants remained high until the pod-filling stage, whereas the chlorophyll content of N-fertilized plants started to decrease as early as the flowering stage. These results suggest that, due to higher C sink strength and efficient N2 fixation, nodulated plants achieve higher rates of photosynthesis and have delayed leaf senescence
    Gewasgroei-analyse zet aan tot andere manier van denken : analytisch denken leidt tot beter inzicht in gewas
    Heuvelink, E. ; Kierkels, T. - \ 2009
    Onder Glas 6 (2009)10. - p. 44 - 45.
    tuinbouw - kassen - assimilatie - analyse - plantdichtheid - vruchtgroenten - vergelijkingen - glastuinbouw - gewasgroeimodellen - groenten - horticulture - greenhouses - assimilation - analysis - plant density - fruit vegetables - comparisons - greenhouse horticulture - crop growth models - vegetables
    Door de groei van het gewas te analyseren kan de teler veel opsteken voor de toekomst. Om cirkelredeneringen te voorkomen is het nodig steeds factoren uit te splitsen. Voorwaarde is dat deze factoren gezamenlijk de verklaring opleveren en elkaar niet overlappen. Zo is een eerlijke vergelijking met de prestaties van voorgaande jaren of met die van collega's mogelijk. In het verhaal zijn voorbeelden uitgewerkt van de manier van denken
    Theoretical reconsiderations when estimating the mesophyll conductance to CO2 diffusion in leaves of C3 plants by analysis of combined gas exchange and chlorophyll fluorescence measurements
    Yin, X. ; Struik, P.C. - \ 2009
    Plant, Cell & Environment 32 (2009)11. - ISSN 0140-7791 - p. 1513 - 1524.
    photosynthetic electron-transport - internal conductance - biochemical-model - quantum yield - in-vivo - assimilation - parameters - field - stoichiometry - chloroplasts
    Existing methods to estimate the mesophyll conductance to CO2 diffusion (gm) are often based on combined gas exchange and chlorophyll fluorescence measurements. However, estimations of average gm by these methods are often unreliable either because the range of usable data is too narrow or because the estimations are very sensitive to measurement errors. We describe three method variants to estimate gm, for which a wider range of data are usable. They use curve-fitting techniques, which minimise the sum of squared model deviations from the data for A (CO2 assimilation rate) or for J (linear electron transport rate). Like the existing approaches, they are all based on common physiological principles assuming that electron transport limits A. The proposed variants were far less sensitive than the existing approaches to 'measurement noise' either created randomly in the generated data set or inevitably existing in real data sets. Yet, the estimates of gm from the three variants differed by approximately 15%. Moreover, for each variant, a stoichiometric uncertainty in linear electron transport-limited photosynthesis can cause another 15% difference. Any estimation of gm using gas exchange and chlorophyll fluorescence measurements should be considered with caution, especially when gm is high
    Postprandial oxidative losses of free and protein-bound amino acids in the diet: interactions and adaptation
    Nolles, J.A. ; Verreijen, A.M. ; Koopmanschap, R.E. ; Verstegen, M.W.A. ; Schreurs, V.V.A.M. - \ 2009
    Journal of Animal Physiology and Animal Nutrition 93 (2009)4. - ISSN 0931-2439 - p. 431 - 438.
    growing-pigs - nitrogen-utilization - free lysine - breath test - humans - metabolism - assimilation - catabolism - retention - casein
    Postprandial oxidation of dietary free amino acids or egg white protein was studied using the [13CO2] breath test in rats, as well as in humans. Thirty-eight male rats were assigned to four dietary test groups. Two diets only differed in their protein fraction. Diet I contained 21% egg white protein. For the breath test egg white protein, intrinsically labelled with [1-13C]-leucine, was used as a substrate. Diet II contained the same amino acids as diet I, though not as egg white protein but in free form. Free [1-13C]-leucine was used to label this diet. In addition, two 1:1 mixtures of both diets were used. During the breath test either the free amino acid or the protein fraction was labelled as in diets I or II. The animals were breath-tested following short-term (day 5) and long-term adaptation (day 20) to their experimental diet. For all diets, including the mixed diets, postprandial oxidative losses on day 5 were significantly higher for the free leucine compared with the protein-derived leucine. Differences between free and protein-derived leucine oxidation had, however, largely disappeared on day 20. The human subjects were breath-tested without any adaptation period to the diets. The oxidative losses of free leucine were also higher than those of protein-derived leucine. None of the studies showed any indication for an interaction between the oxidation of protein-derived amino acids and free amino acids. It is concluded that free and protein-derived amino acids in the diet are mainly metabolized independently
    Hogere CO2 - concentratie basis voor meerproductie
    Dieleman, J.A. ; Gelder, A. de - \ 2009
    Groenten en Fruit. Algemeen 2009 (2009)16. - ISSN 0925-9694 - p. 18 - 19.
    tuinbouwbedrijven - kassen - tomaten - kooldioxide - assimilatie - fotosynthese - gewasproductie - glastuinbouw - semi-gesloten kassen - geconditioneerde teelt - market gardens - greenhouses - tomatoes - carbon dioxide - assimilation - photosynthesis - crop production - greenhouse horticulture - semi-closed greenhouses - conditioned cultivation
    Op alle bedrijven waar (semi)gesloten wordt geteeld, hebben telers nog vragen over de reacties van het gewas op het nieuwe klimaat. WUR Glastuinbouw voert daarom een onderzoek uit naar de groei van tomaat in geconditioneerde kassen, waarbij veel aandacht wordt besteed aan de fysiologische processen in de plant. Enkele tomatentelers en een adviseur begeleiden dit onderzoek
    Scatterometer-Derived Soil Moisture Calibrated for Soil Texture With a One-Dimensional Water-Flow Model
    Lange, R. de; Beck, R. ; Giesen, N. van de; Friesen, J. ; Wit, A.J.W. de; Wagner, W. - \ 2008
    IEEE Transactions on Geoscience and Remote Sensing 46 (2008)12. - ISSN 0196-2892 - p. 4041 - 4049.
    ers scatterometer - near-surface - assimilation - retrieval - validation - space
    Current global satellite scatterometer-based soil moisture retrieval algorithms do not take soil characteristics into account. In this paper, the characteristic time length of the soil water index has been calibrated for ten sampling frequencies and for different soil conductivity associated with 12 soil texture classes. The calibration experiment was independently performed from satellite observations. The reference soil moisture data set was created with a I-D water-flow model and by making use of precipitation measurements. The soil water index was simulated by applying the algorithm to the modeled soil moisture of the upper few centimeters. The resulting optimized characteristic time lengths T increase with longer sampling periods. For instance, a T of 7 days was found for sandy soil when a sampling period of I day was applied, whereas an optimized T-value of 18 days was found for a sampling period of 10 days. A maximum rmse improvement of 0.5% vol. can be expected when using the calibrated T-values instead of T = 20. The soil water index and the differentiated T-values were applied to European Remote Sensing (ERS) satellite scatterometer data and were validated against in situ soil moisture measurements. The results obtained using calibrated T-values and T = 20 did not differ (r = 0.39, rmse = 5.4% vol.) and can be explained by the averaged sampling period of 4-5 days. The soil water index obtained with current operational microwave sensors [Advanced Wind Scatterometer (ASCAT) and Advanced Microwave Scanning Radiometer-Earth Observation System] and future sensors (Soil Moisture and Ocean Salinity and Soil Moisture Active Passive) should benefit from soil texture differentiation, as they can record on a daily basis either individually or synergistically using several sensors. The proposed differentiated characteristic time length enables the continuation of the soil water index of sensors with varying sampling periods (e.g., ERS-ASCAT).
    Fertilizer residence time affects nitrogen uptake efficiency and growth of sweet corn
    Zotarelli, L. ; Scholberg, J.M.S. ; Dukes, M.D. ; Munoz-Carpena, R. - \ 2008
    Journal of Environmental Quality 37 (2008)3. - ISSN 0047-2425 - p. 1271 - 1278.
    sandy soil - drip irrigation - root systems - nitrate - maize - temperature - recovery - plants - yield - assimilation
    Understanding plant N uptake dynamics is critical for increasing fertilizer N uptake efficiency (FUE) and minimize the risk of N leaching. The objective of this research was to determine the effect of residence time of N fertilizer on N uptake and FUE of sweet corn. Plants were grown in 25 L columns during the fall and spring to mimic short-term N uptake dynamics. Nitrogen was applied either 1, 3, or 7 d before a weekly leaching event, using KNO3 solution (total of 393 kg N ha(-1)). Residence times (t(R)) were t(R)-1, t(R)-3, and t(R)-7 d before weekly removal of residual soil N. Plant N uptake was calculated by comparing weekly N recovery from planted with non-planted columns. During the fall, N uptake values at 70 d after emergence were 59, 73, and 126 kg N ha(-1). During the spring, corresponding values were 54,108, and 159 kgN ha(-1). A linear response of plant growth and yield to the tR was observed under cooler conditions, whereas a quadratic response occurred under warmer conditions. There was correlation between root length density and yield. It is concluded that increasing N fertilizer residence time, which is indicative of better irrigation practices, enhanced overall sweet corn growth, yield, N uptake, and FUE, consequently reduced the risk of N being leached below the root zone before complete N uptake.
    Gewasbelichting met hoogfrequent pulserende LEDs: deel 2: pulserend licht met gelijke lichtsom
    Ruijter, J.A.F. de; Meinen, E. ; Dueck, T.A. - \ 2008
    Wageningen : Wageningen UR Glastuinbouw (59762189-TOS/TCM 08-7006 KEMA ) - 44
    glastuinbouw - lichtsterkte - lichtregiem - belichting - klimaatregeling - teeltsystemen - led lampen - assimilatie - greenhouse horticulture - light intensity - light regime - illumination - air conditioning - cropping systems - led lamps - assimilation
    Assimilatiebelichting neemt een steeds belangrijkere plaats in de Nederlandse glastuinbouw. Dit productiemiddel is echter een grootverbruiker van energie en de lichtuitstoot die met belichting gepaard kan gaan, is een belangrijk thema bij de maatschappelijke acceptatie van deze vorm van glastuinbouw. Uit het oogpunt van zowel energieverbruik, energiekosten als reductie van de lichthinder is het gewenst in de komende jaren assimilatiebelichting verder te verbeteren en beter af te stemmen op de plant, de energievoorziening van de kas en de omgeving. Omdat ten aanzien van de momenteel gangbare hogedruknatriumlampen in de toekomst nog slechts marginale verbeteringen worden verwacht, dient te worden gezocht naar lichttechnologie met doorbraakpotentieel. LED’s (light emitting diodes) lijken dit potentieel te hebben.
    Modelling representation errors of atmospheric CO2 concentrations at a regional scale
    Tolk, L.F. ; Meesters, A.G.C.A. ; Dolman, A.J. ; Peters, W. - \ 2008
    Atmospheric Chemistry and Physics 8 (2008)1. - ISSN 1680-7316 - p. 6587 - 6596.
    broeikasgassen - kooldioxide - klimaatverandering - modellen - emissiereductie - greenhouse gases - carbon dioxide - climatic change - models - emission reduction - mass conservation - transport models - system rams - inversion - fluxes - assimilation - variability - continent - forest
    Inverse modelling of carbon sources and sinks requires an accurate quality estimate of the modelling framework to obtain a realistic estimate of the inferred fluxes and their uncertainties. So-called "representation errors" result from our inability to correctly represent point observations with simulated average values of model grid cells. They may add substantial uncertainty to the interpretation of atmospheric CO2 mixing ratio data. We simulated detailed variations in the CO2 mixing ratios with a high resolution (2 km) mesoscale model (RAMS) to estimate the representation errors introduced at larger model grid sizes of 10¿100 km. We found that meteorology is the main driver of representation errors in our study causing spatial and temporal variations in the error estimate. Within the nocturnal boundary layer, the representation errors are relatively large and mainly caused by unresolved topography at lower model resolutions. During the day, convective structures, mesoscale circulations, and surface CO2 flux variability were found to be the main sources of representation errors. Interpreting observations near a mesoscale circulation as representative for air with the correct footprint relative to the front can reduce the representation error substantially. The remaining representation error is 0.5¿1.5 ppm at 20¿100 km resolution.
    Schimmels veroorzaken merendeel van de plantenziekten : voortdurende wapenwedloop tussen plant en schimmel
    Kierkels, T. ; Heuvelink, E. - \ 2008
    Onder Glas 5 (2008)3. - p. 4 - 5.
    schimmel - plantenziekteverwekkende schimmels - koolhydraten - assimilatie - ziekteresistentie - antagonisten - ondersteunende maatregelen - gewasbescherming - glastuinbouw - moulds - plant pathogenic fungi - carbohydrates - assimilation - disease resistance - antagonists - support measures - plant protection - greenhouse horticulture
    Schimmels kunnen niet zelf assimileren en maken daarom gebruik van dat vermogen van planten. Cruciaal is dat ze planten moeten binnendringen om bij de koolhydraten te kunnen komen. Daartoe hebben ze tal van manieren ontwikkeld, mechanisch en chemisch. De plant op zijn beurt zet blokkades en chemie in om de schimmels te weren. Een goed groeiende, gezonde plant is in het algemeen weerbaar genoeg. Inzicht in de 'wapenwedloop' tussen schimmel en plant wijst een teler de weg naar ondersteunende maatregelen
    Huidmondjes: de poorten van de bladeren : voortdurend balanceren tussen assimilatie en vochtverlies
    Heuvelink, E. ; Kierkels, T. - \ 2008
    Onder Glas 5 (2008)1. - p. 20 - 21.
    kassen - teelt onder bescherming - planten - bladeren - beweging van huidmondjes - huidmondjes - zuurstof - water - klimaatfactoren - lichtsterkte - assimilatie - glastuinbouw - greenhouses - protected cultivation - plants - leaves - stomatal movement - stomata - oxygen - water - climatic factors - light intensity - assimilation - greenhouse horticulture
    Huidmondjes moeten zo ver mogelijk openstaan om CO2 binnen te laten en zoveel mogelijk dicht blijven om vochtverlies te beperken. De plat is voortdurend bezig tussen deze eisen te schipperen. Dag-nachtritme, lichtintensiteit en -kleur, CO2-concentratie en vochttoestand van de plant hebben allemaal hun invloed. Het is voor een teler daarom vrijwel niet mogelijk specifiek op de opening van de huidmondjes te sturen
    Afbakening en testen van het lichtspectrum voor optimale assimilatiebelichting in kassen: kasproef
    Rijssel, E. van; Marissen, A. ; Dueck, T.A. ; Pot, S. - \ 2007
    Wageningen : Wageningen UR Glastuinbouw - 38
    glastuinbouw - belichting - kunstmatige verlichting - kasproeven - tuinbouw - assimilatie - lampen - vruchtgroenten - potplanten - snijbloemen - greenhouse horticulture - illumination - artificial lighting - greenhouse experiments - horticulture - assimilation - lamps - fruit vegetables - pot plants - cut flowers
    De doelstelling van het experiment is kennis te verzamelen over de effecten op de groei en ontwikkeling van glastuinbouwgewassen van een lamp waarin het spectrum verder sterk is verschoven naar een hoge rood/verrood verhouding en met een verrijking in het blauw gedeelte. Deze kennis wordt gebruikt als basis voor het ontwikkelen van nieuwe typen assimilatielampen.
    Effects of organic matter content on earthworms and nitrogen mineralization in grassland soils
    Vliet, P.C.J. van; Stelt, B. van der; Rietberg, P.I. ; Goede, R.G.M. de - \ 2007
    European Journal of Soil Biology 43 (2007)suppl. 1. - ISSN 1164-5563 - p. S222 - S229.
    lumbricus-terrestris l - land-use history - agroecosystems - assimilation - dynamics - oligochaeta - consumption - abundance - quality - systems
    Earthworms play an important role in the nitrogen cycle in the soil. Through their activities they affect the mineralization of organic matter directly and indirectly. However, the presence of organic matter also affects earthworm abundances. For this study, we selected 2 grasslands differing in organic matter content at nine dairy farms on sandy soils in the Noordelijke Friese Wouden (NFW) in the Netherlands. We expected a larger number of earthworms and a higher mineralization rate in grasslands with a higher organic matter content. We also expected a positive relationship between earthworm abundance and nitrogen mineralization. At each farm the grassland with the highest organic matter content contained the largest number of earthworms (up to 858 worms m(-2)), (r = 0.286 (p = 0.036)). These grasslands also had the highest root biomass (r = 0.504 (p = 0.0001). With an increase in organic matter in the soil (from 5 to 10.2%), potential nitrogen mineralization increased from 138 to 310 kg N-1 ha 6 months(-1). No relationships between the calculated amount of nitrogen mineralized by earthworms and the potential and actual nitrogen mineralization were found. Nitrogen mineralization due to earthworm activities, calculated using production ecological formulas, ranged from 4 to 24 ka N ha(-1) month(-1). (c) 2007 Elsevier Masson SAS. All rights reserved.
    Belichting met LED's maakt nieuwe manier van telen mogelijk: LED's bieden op termijn veel perspectief
    Kierkels, T. ; Ieperen, W. van - \ 2007
    Onder Glas 4 (2007)5. - p. 43 - 45.
    teelt onder bescherming - belichting - lampen - kunstlicht - optische eigenschappen - plantenontwikkeling - assimilatie - landbouwkundig onderzoek - innovaties - glastuinbouw - protected cultivation - illumination - lamps - artificial light - optical properties - plant development - assimilation - agricultural research - innovations - greenhouse horticulture
    Assimilatiebelichting met LED's kan op termijn wellicht een belangrijk deel van de hogedruk natriumlampen vervangen. Voor het zover is, moet er echter nog veel onderzocht worden. Het gaat niet alleen maar om het vervangen van het ene groeilicht door het andere. De nieuwe techniek maakt een totaal andere teelt mogelijk, met hogere producties in het verschiet. Belangrijk is om het gebruik van LED's in een totaal teelt- en kasconcept in te passen
    Ademhaling van plant is nodig voor groei en onderhoud : groeisnelheid in zomer tien keer hoger dan in winter
    Heuvelink, E. ; Kierkels, T. - \ 2007
    Onder Glas 4 (2007)11. - p. 14 - 15.
    bloementeelt - sierplanten - gewassen, groeifasen - plantenontwikkeling - assimilatie - ademhaling - seizoengroei - plantenfysiologie - gesloten systemen - glastuinbouw - snijbloemen - potplanten - floriculture - ornamental plants - crop growth stage - plant development - assimilation - respiration - seasonal growth - plant physiology - closed systems - greenhouse horticulture - cut flowers - pot plants
    Kost ademhaling van de plant productie of levert het productie op? Het antwoord is: allebei. Sturen op ademhaling is een ingewikkelde zaak. Bij een gesloten kas is de onderhoudsademhaling iets om meer rekening mee te houden
    Blad dicht bij komkommers houden
    Dieleman, J.A. - \ 2007
    Groenten en Fruit. Algemeen 2007 (2007)11. - ISSN 0925-9694 - p. 20 - 21.
    tuinbouw - assimilatie - bladeren - organische koolstof - cucumis - plantenfysiologie - gewasproductie - onderzoek - glastuinbouw - horticulture - assimilation - leaves - organic carbon - cucumis - plant physiology - crop production - research - greenhouse horticulture
    Aan een plant is niet te zien hoeveel elk blad bijdraagt aan de groei van die plant. Met 'gemerk CO2' werd in Wageningen duidelijk dat de meeste assimilaten naar de grootste komkommers aan een plant gaan. De assimilaten bewegen zich door de hele plant, maar voor een goede productie is het van belang bladeren en vruchten bij elkaar in de buurt te hebben. Een reportage over onderzoek naar assimilatie door bladeren en de groei van een gewas
    Comparison of different stomatal conductance algorithms for ozone flux modelling
    Büker, P. ; Emberson, L.D. ; Ashmore, M.R. ; Gerosa, G. ; Jacobs, C.M.J. ; Massman, W.J. ; Müller, J. ; Nikolov, N. ; Novak, K. ; Oksanen, E. ; Torre, D. de la; Tuovinen, J.P. - \ 2007
    Environmental Pollution 146 (2007)3. - ISSN 0269-7491 - p. 726 - 735.
    h2o gas-exchange - photosynthesis model - carbon-dioxide - c-3 plants - water - vegetation - co2 - assimilation - ecosystems - atmosphere
    A multiplicative and a semi-mechanistic, BWB-type [Ball, J.T., Woodrow, I.E., Berry, J.A., 1987. A model predicting stomatal conductance and its contribution to the control of photosynthesis under different environmental conditions. In: Biggens, J. (Ed.), Progress in Photosynthesis Research, vol. IV. Martinus Nijhoff, Dordrecht, pp. 221e224.] algorithm for calculating stomatal conductance (gs) at the leaf level have been parameterised for two crop and two tree species to test their use in regional scale ozone deposition modelling. The algorithms were tested against measured, site-specific data for durum wheat, grapevine, beech and birch of different European provenances. A direct comparison of both algorithms showed a similar performance in predicting hourly means and daily time-courses of gs, whereas the multiplicative algorithm outperformed the BWB-type algorithm in modelling seasonal time-courses due to the inclusion of a phenology function. The re-parameterisation of the algorithms for local conditions in order to validate ozone deposition modelling on a European scale reveals the higher input requirements of the BWB-type algorithm as compared to the multiplicative algorithm because of the need of the former to model net photosynthesis (An).
    Genetic and environmental factors affecting growth of Nile tilapia (Oreochromis niloticus) juveniles: modelling spatial correlations between hapas
    Charo-Karisa, H. ; Komen, J. ; Rezk, M.A. ; Reynolds, S. ; Ponzoni, R.W. ; Bovenhuis, H. - \ 2006
    Aquaculture 255 (2006). - ISSN 0044-8486 - p. 586 - 596.
    salmon salmo-salar - quantitative genetics - water temperature - selection - genotype - performance - weight - heritability - assimilation - variability
    The aim of this study was to quantify the environmental and genetic effects on early growth of Nile tilapia, Oreochromis niloticus, in hapa-in-earthen pond systems. In a pilot study, we grew swim-up fry with or without supplementary feed in hapas suspended in fertilized ponds at 5, 10, 15, and 20 fry/m2 densities. In the main experiment, we reared swim-up fry from 25 full-sib families separately for 42 days at 15 fry/m2 density in hapas suspended in two earthen ponds. Hapas were arranged in two column arrays along the sides of the ponds. Ponds were fertilized daily with chicken manure. In addition, fry in one column in each pond were fed twice daily on 40% protein pelleted feed. Results from the pilot study indicated significant effects of stocking density and treatment. In the main experiment, the dietary treatment effect was not significant but there were large differences in growth between ponds. Mean body weight at 42 days was 1.7 g in pond A and 0.4 g in pond B. Fry heritability (h2) of 42-day fry body weight estimated from the whole data set using a univariate model was 0.01 ± 0.06. The bivariate heritability estimates were 0.59 ± 0.19 in pond A and 0.05 ± 0.11 in pond B. The common environmental/hapa (c2) effects were 0.14 ± 0.06 and 0.29 ± 0.07 in respective ponds. We found significant positive spatial autocorrelation (P = 0.02) indicating resemblance in growth of fry in neighboring hapas. Analysis of environmental variables showed that the two ponds differed significantly in dissolved oxygen. The low genetic correlation (rg = - 0.27 ± 0.69) between body weights of fry in both ponds therefore might suggest genotype by environment interactions for tolerance to low dissolved oxygen in Nile tilapia juveniles
    Suiker legt soms een meterslange weg af door de plant
    Arkesteijn, M. ; Dieleman, J.A. - \ 2006
    Onder Glas 3 (2006)11. - p. 27 - 29.
    komkommers - assimilatie - netto-assimilatiesnelheid - plantenfysiologie - teelt onder bescherming - glastuinbouw - groenten - cucumbers - assimilation - net assimilation rate - plant physiology - protected cultivation - greenhouse horticulture - vegetables
    Verslag van onderzoek door PRI naar de verdeling van assimilaten in komkommer. De meeste assimilaten gaan naar de grootste vruchten. Uit weeg- en telonderzoek blijkt dat de afstand tussen de vruchten en het fotosynthetiserende blad niet te groot mag worden om productieverlies te voorkomen. Gegevens in bijgaande figuur: De procentuele verdeling van de hoeveelheid 13C in de plant over de verschillende organen, 24 uur na de start van de behandeling op 9 maart
    Plant kan veel meer produceren dan hij nu doet
    Heuvelink, E. ; Kierkels, T. - \ 2006
    Onder Glas 3 (2006)1. - p. 5 - 7.
    kassen - plantenontwikkeling - lichtregiem - belichting - assimilatie - cultuurmethoden - opbrengsten - productiviteit - glastuinbouw - greenhouses - plant development - light regime - illumination - assimilation - cultural methods - yields - productivity - greenhouse horticulture
    Planten kunnen veel meer presteren dan ze in de praktijk doen. Omdat niet alle omstandigheden optimaal zijn, kan niet het maximum uit de plant gehaald worden. Daarbij is het licht de beperkende factor. Een teler moet daarom proberen het licht zo efficiënt mogelijk om te zetten in een vers product dat hij kan verkopen. Dat kan door zoveel mogelijk licht op de planten te laten vallen, door te zorgen voor voldoende bladmassa, door de assimilaten naar het oogstbare deel te versturen en te kijken naar de hoeveelheid versgewicht
    Can photosynthesis-related parameters be used to establish the activity of acetolactate synthase-inhibiting herbicides on weeds?
    Riethmuller-Haage, I.C.P. ; Bastiaans, L. ; Kropff, M.J. ; Harbinson, J. ; Kempenaar, C. - \ 2006
    Weed Science 54 (2006)6. - ISSN 0043-1745 - p. 974 - 982.
    chlorophyll fluorescence - electron-transport - leaves - light - temperature - maize - assimilation - metabolism - oxidation - responses
    The application of the acetolactate synthase (ALS)¿inhibiting herbicide metsulfuron on greenhouse- and field-grown black nightshade and greenhouse-grown ladysthumb resulted in progressive inhibition of the level of carbon dioxide (CO2) fixation, the relative quantum efficiency of electron transport through photosystem I (PSI) and II (PSII), and the leaf chlorophyll content. Photosynthetic-related measurements, measured 2 to 4 d after treatment (DAT) at photon flux densities of 400 to 500 ¿mol m¿2 s¿1, provided valuable information before the visual symptoms that first appeared at 7 to 10 DAT with the herbicide. Measurements of the quantum efficiency for electron transport by photosystem II and the loss in leaf chlorophyll content appeared to be two of the most practical parameters to use when designing an early detection method to assess the toxicity of metsulfuron. The use of chlorophyll fluorescence would require a comparison of steady-state PSII measurements for control and treated plants, which could be realized by either measuring in time (before/after application) or space (treated/untreated patch)
    Assimilaten uit een komkommerblad: waar gaan ze heen?
    Dieleman, J.A. ; Steenhuizen, J.W. ; Meurs, E.J.J. - \ 2006
    Wageningen : Plant Research International (Nota / Plant Research International 422) - 34
    cucumis sativus - komkommers - assimilatie - fotosynthese - fotosyntheseproducten - source-sink relaties - stofverplaatsing - plantenfysiologie - cucumis sativus - cucumbers - assimilation - photosynthesis - photosynthates - source sink relations - translocation - plant physiology
    In de teelt met beweegbare gewasdraden worden tot de draad 22 bladeren gevormd, op het 19e blad wordt een zijscheut aangehouden. In een experiment wordt nagegaan wat het 20e, 21e en 22e blad voor de komkommers doen. Leveren die assimilaten aan de komkommers, of is het energieverspilling om die bladeren aan te houden?
    Space-time Kalman filtering of soil redistribution
    Heuvelink, G.B.M. ; Schoorl, J.M. ; Veldkamp, A. ; Pennock, D.J. - \ 2006
    Geoderma 133 (2006)1-2. - ISSN 0016-7061 - p. 124 - 137.
    landscape evolution - elevation models - tillage erosion - cesium-137 - geostatistics - water - assimilation - movement - patterns - moisture
    Soil redistribution is the net result of erosion and sedimentation. Assessment of soil redistribution in a given landscape over a given period of time may be done using process-based and empirical approaches. Process-based approaches rely on knowledge of how environmental processes acting in the landscape cause soil to move from one place to another. Empirical approaches rely on measurements of soil redistribution, which may be interpolated in space and time using (geo)statistical methods. In this paper we use space¿time Kalman filtering to combine these two basic approaches. The Kalman filter operates recursively to predict forward one step at a time the soil redistribution from the predicted soil redistribution at the previous time and the measurements at the current time. The methodology is illustrated with a case study from a seven hectare segment site, located on the hummocky till plains of Saskatchewan, Canada. Tillage erosion causes soil to move downward along the steepest gradient, whereby the amount of soil loss per year is assumed linearly related to slope angle. Measurements of cumulative soil redistribution from 1963 to 2000 were derived using Cesium-137 as a tracer. In total 99 measurements were taken, using a regular sampling design with a grid mesh of 25 m. The soil redistribution measurements differed meaningfully from the deterministic model predictions (R2 = 0.389), causing the Kalman filter to make a marked adjustment to the soil redistribution map. The adjustment was particularly strong along the transportation route near the measurement locations. Use of the space¿time Kalman filter to predict soil redistribution is attractive because it makes optimum use of process knowledge and measurements, but routine use of the technique is hampered by the computational load and by parameterisation problems. Sensitivity analyses showed that the model results are most sensitive to the system noise. Future research must therefore be directed to realistic assessment of the errors inflicted by the assumptions and simplifications of the soil redistribution model
    Influence of the acetolactate synthase inhibitor metsulfuron-methyl on the operation, regulation and organisation of photosynthesis in Solanum nigrum
    Riethmuller-Haage, I.C.P. ; Bastiaans, L. ; Harbinson, J. ; Kempenaar, C. ; Kropff, M.J. - \ 2006
    Photosynthesis Research 88 (2006)3. - ISSN 0166-8595 - p. 331 - 341.
    electron-transport - leaves - chlorsulfuron - maize - assimilation - efficiencies - herbicides - reduction - oxidation - p-700
    The influence of the acetolactate synthase inhibitor metsulfuron-methyl on the operation of the photosynthetic apparatus was examined on 4-weeks-old climate chamber-grown Solanum nigrum plant. To have an indication on the relative performance of the photosynthetic apparatus of ALS-treated plants, the level of carbon dioxide (CO2) fixation, the relative quantum efficiency of photosystem I (¿PSI) or photosystem II (¿PSII) electron transport and leaf chlorophyll content were assessed for both control and treated plants at 2, 4 and 7 days after application of the herbicide. Results indicated a progressive inhibition of the level of CO2 fixation, the relative quantum efficiency of photosystem I (¿PSI) and II (¿PSII) electron transport and the leaf chlorophyll content already 2 days after application of the herbicide. The linear relationship between the photosystem I and II was unaltered by herbicidal treatment and was sustained under conditions where large changes in pigment composition of the leaves occurred. It appears that the stress-induced loss of leaf chlorophyll is not a catastrophic process but rather is the consequence of a well-organised breakdown of components. Under photorespiratory and non-photorespiratory conditions, the relationship between the index of electron transport flow through photosystem I and II and the rate of CO2 fixation is altered so that electron transport becomes less efficient at driving CO2 fixation. Keywords Herbicide - Photosystem I - Photosystem II - Quantum efficiency - Sulfonylurea - CO2 fixation - Chlorophyll - Chlorophyll fluorescence
    Flexibele meerdaagse temperatuurinstelling op basis van de assimilatenbalans van het gewas
    Elings, A. ; Zwart, H.F. de; Janse, J. ; Buwalda, F. ; Marcelis, L.F.M. - \ 2006
    Wageningen : Plant Research International (Nota / Plant Research International 383) - 68
    milieubeheersing - verwarming - teelt onder bescherming - kassen - assimilatie - fotosynthese - glastuinbouw - energiebesparing - environmental control - heating - protected cultivation - greenhouses - assimilation - photosynthesis - greenhouse horticulture - energy saving
    Temperatuur speelt een belangrijke rol bij de regulatie van de assimilatenbalans. In het project 'Meerdaagse temperatuur instelling op basis van de assimilatenbalans van het gewas' wordt op zoek gegaan naar een nieuwe energiebesparende temperatuursturing. Voor het voorbeeldgewas komkommer zijn er berekeningen met het INTKAM gewasgroeimodel van PRI en het KASPRO kasklimaatmodel van PRI uitgevoerd. Evenwicht in de assimilatenbalans kan een aanzienlijke energiebesparing opleveren, zonder productieverlies
    Assessing options to increase water productivity in irrigated river basins using remote sensing and modelling tools
    Dam, J.C. van; Singh, R. ; Bessembinder, J.J.E. ; Leffelaar, P.A. ; Bastiaanssen, W.G.M. ; Jhorar, R.K. ; Kroes, J.G. ; Droogers, P. - \ 2006
    International Journal of Water Resources Development 22 (2006)1. - ISSN 0790-0627 - p. 115 - 133.
    crop - assimilation
    In regions where water is more scarce than land, the water productivity concept (e.g. crop yield per unit of water utilized) provides a useful framework to analyse crop production increase or water savings in irrigated agriculture. Generic crop and soil models were applied at field and regional scale, together with geographical and satellite data to analyse water productivity in Sirsa District (India). In this district certain parts show a serious decline in groundwater levels and water shortage, while other parts experience a serious rise of groundwater levels, causing waterlogging and salinization. The regional analysis showed a large spatial variability of water productivity, net groundwater recharge and salinization. Scenario analysis showed that improved crop husbandry, reallocation of canal water from fresh to saline groundwater areas and reduction of seepage losses in saline groundwater areas are effective measures to increase the overall water productivity and to attain sustainable irrigation in Sirsa District.
    Aanvullend rapport gasgestookte assimilatiebelichting : eindrapportage
    Sonneveld, P.J. - \ 2005
    Wageningen : Agrotechnology & Food Innovations (Rapport / Wageningen UR, Agrotechnology & Food Innovations 563b) - 5
    verlichting - kunstmatige verlichting - belichting - kunstlicht - assimilatie - lampen - aardgas - energiebehoud - warmteuitwisseling - teelt onder bescherming - plantenontwikkeling - glastuinbouw - lighting - artificial lighting - illumination - artificial light - assimilation - lamps - natural gas - energy conservation - heat exchange - protected cultivation - plant development - greenhouse horticulture
    Vruchtzetting paprika spel van vraag en aanbod
    Marcelis, L.F.M. ; Heuvelink, E. - \ 2005
    Groenten en Fruit. Algemeen (2005)33. - ISSN 0925-9694 - p. 20 - 21.
    capsicum - teelt - cultuurmethoden - vruchtzetting - hormonen - zaadzetting - assimilatie - plantenfysiologie - groeimodellen - gewasopbrengst - relatie tussen groei en oogst - capsicum - cultivation - cultural methods - fructification - hormones - seed set - assimilation - plant physiology - growth models - crop yield - growth yield relationship
    Voor een goede productie bij paprika is niet het aantal bloemen, maar het aantal gezette vruchten de beperkende factor. De zetting wordt vooral bepaald door de beschikbaarheid van assimilaten. Die beschikbaarheid wordt bepaald door de aanmaak van deze suikers en de vraag ernaar van al gezette vruchten. De effecten van vraag en aanbod van assimilaten werden door Plant Research International en Wageningen Universiteit opgenomen in een groeimodel, dat op basis van klimaatgegevens en enkele teeltgegevens de groei en productie berekent. Met behulp van dit groeimodel bleek de zetting van te voren redelijk te voorspellen
    Energiebesparing mobiele belichting roos
    Marissen, N. ; Elings, A. ; Snel, J.F.H. ; Warmenhoven, M.G. ; Meinen, E. ; Dijkhuis, P. ; Kouwenhoven, D. ; Schrama, P.M.M. ; Uenk, D. - \ 2005
    Naaldwijk : Praktijkonderzoek Plant en Omgeving (PPO rapport 41616002) - 64
    rosa - rozen - aanvullend licht - kunstlicht - fotosynthese - assimilatie - simulatiemodellen - groeianalyse - rosa - roses - supplementary light - artificial light - photosynthesis - assimilation - simulation models - growth analysis
    Over mobiele belichting wordt al jarenlang op verschillende manieren gedacht: enerzijds zou het een manier zijn om lage lichtintensiteiten goed te verdelen over het gewas, anderzijds zou het een manier zijn om energie te besparen, doordat met minder lampen hetzelfde groei-effect werd verwacht. De ‘bewijzen’ van meerproductie onder mobiel licht, vergeleken met dezelfde of een hogere lichtsom waren alleen afkomstig uit praktijkproeven. Een echte fysiologische verklaring voor de vermeende effecten van mobiel licht is nooit gegeven en getoetst. Eén van de theorieën veronderstelt een beter gebruik van het licht (daglicht én assimilatielicht) doordat er af en toe een lichtpuls van hogere intensiteit de planten raakt. Ook zou het op gang komen van de fotosynthese tijdens de lichtpuls beter zijn dan bij continue belichting, zodat wanneer het daglicht fluctueert, de fotosynthese sneller op gang komt in de lichte perioden. Een eventuele betere regulatie van de opening van de huidmondjes (waar de CO2 door naar binnen moet) is ook genoemd. Om te bepalen of er positieven effecten van mobiele belichting zijn en of ze te verklaren zijn uit de eigenschappen van de fotosynthese is een proef met roos uitgevoerd. In deze proef is gekozen voor de zogenaamde ‘lange slag’ mobiele belichting. Dat wil zeggen dat de lampen een lange weg afleggen boven het gewas (in dit project ca 10 meter) en dat de lichtintensiteit tussen twee lichtpulsen in heel laag of nihil is. Ook is er geen achtergrondbelichting van vaste assimilatiebelichting bij de mobiele belichting. De lichtintensiteit voor de planten onder mobiele lampen varieert ‘s nachts daardoor van heel hoog tot nul. In de rozenpraktijk wordt ondertussen vooral belicht met ‘korte slag’ belichting, waar de weg van de lampen meestal van poot tot poot is, dus 4 à 5 meter, en waarbij er wél achtergrondbelichting is van vaste lampen. Deze planten ondervinden dus wel een wisselende lichtintensiteit, maar ‘s nachts wordt de lichtintensiteit nooit nul. Te verwachten is dat de fysiologische verschillen tussen mobiele en vaste belichting bij een lange-slag belichting groter zijn dan bij een korte-slag belichting.
    Vergelijking van de organische stofmodellen MOTOR en MINIP
    Heinen, M. ; Willigen, P. de - \ 2005
    Wageningen : Alterra (Alterra-rapport 1260) - 49
    organische stof - bodem - modellen - simulatiemodellen - stikstof - koolstof - assimilatie - degradatie - organic matter - soil - models - simulation models - nitrogen - carbon - assimilation - degradation
    In dit technisch document wordt kort beschreven de theorie van de modellen MINIP en MOTOR, welke beiden de afbraak van organische materialen beschrijven. Er worden uitdrukkingen gegeven voor de mineralisatie van koolstof en van stikstof. Beiden modellen beschrijven mineralisatie als een exponentiele afbraak: in MINIP is de afbraakconstante tijdsafhankelijk, terwijl in MOTOR deze constant is. MINIP is een vastgesteld concept, terwijl MOTOR de gebruiker de vrijheid geeft een eigen poolconcept op te stellen, en transformaties van eerste orde (eventueel tweede orde) tussen de diverse pools op te stellen. Empirisch is vastgesteld dat speciale MOTOR pools concepten vrijwel identieke koolstof afbraak kunnen berekenen als MINIP, maar dat de stikstofmineralisatie iets afwijkt. Een willekeurig ander poolsconcept binnen MOTOR kan ook geheel andere stikstofmineralisatie berekenen dan MINIP. Omdat de filosofie tussen beiden modellen nogal verschillend is, met name omdat MOTOR geen vast omschreven concept is, is het niet mogelijk om op theoretische basis aan te geven welk model ‘het beste’ is
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