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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    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
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