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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    Optimization of productivity and quality of irrigated tomato (Solanum lycopersicum L.) by smallholder farmers in the Central Rift Valley area of Oromia, Ethiopia
    Gemechis, Ambecha O. - \ 2017
    Wageningen University. Promotor(en): P.C. Struik, co-promotor(en): B. Emana. - Wageningen : Wageningen University - ISBN 9789463431576 - 262
    solanum lycopersicum - irrigation - crop production - optimization - photosynthesis - chlorophyll - gas exchange - water use efficiency - crop yield - ethiopia - solanum lycopersicum - irrigatie - gewasproductie - optimalisatie - fotosynthese - chlorofyl - gasuitwisseling - watergebruiksrendement - gewasopbrengst - ethiopië

    Tomato (Solanum lycopersicum L.) is a vegetable crop with high potential to contribute to poverty reduction via increased income and food security. It is widely grown by smallholders, has high productivity and its demand is increasing. Ethiopia produced about 30,700 Mg of tomatoes on 5,027 ha annually in 2014/2015. Average yields are only 6.1 Mg ha-1, below the world average yields. There is both a need and a potential to increase tomato production per unit area.

    The aim of this thesis is to analyze the irrigated tomato production systems of smallholder farmers in Ethiopia, to survey and characterize the tomato in selected ecoregions and seasons, and to identify yield-limiting or yield-reducing factors and opportunities to enhance yield by using a combination of surveys and field experiments. Field experiments on optimization of yield and quality of field-grown tomato were carried out at Ziway, Ethiopia, for two seasons to study the impact of different irrigation practices applied, based on local empirical practices, deficit irrigation, or crop water requirement.

    This thesis begins with a survey of tomato production systems. The survey details the area and production in various zones and for each of these zones yield- determining, yield-limiting, and yield-reducing factors and opportunities for improving yield and quality are indicated. It also avails area, production and yield data for each growing season and typifies the production systems in these zones. Low temperature (cold) from October-January and shortage of improved seeds are recognized as yield-determining factors, whereas insufficient water and nutrient (fertilizer) supply proved to be yield-limiting factors across zones. Late blight (Phytophthora infestans), Fusarium wilt (Fusarium oxysporum) and different pests and weeds are identified as yield-reducing factors in the zones. Experienced growers who have access to extension service recorded significant yield increment. Farmers Research Groups improved actual average yield with the use of improved technology (improved varieties and quality seed), and better efficiencies of water and fertilizer use. This study quantified influences of irrigation systems and strategies on growth-determining tomato features. Variation in irrigation systems and strategies accounted for variation in growth and dry matter accumulation. Greater performance for yield-related traits was obtained with drip irrigation based on crop water requirement for tomato varieties. Examination of plants showed also that local empirical irrigation is responsible for the occurrence of Phytophthora root rot, whereas deficit irrigation proved cause for occurrence of Fusarium wilt (Fusarium oxysporum), blossom end rot and broome rape (Orobanche ramosa) on roots or leaves, stems or fruits.

    The experiments on irrigation scheduling with different irrigation systems and strategies gave useful indications on the possibility to improve commercial yield (CY) and water use efficiency. Promising results on CY and agronomical water use efficiency of tomato were achieved with drip irrigation based on crop water requirement, while for the biological water use efficiency higher value was obtained with deficit drip irrigation in both seasons. The findings indicate that the CY was decreased significantly for deficit by 50% in drip irrigation and deficit by 50% in furrow irrigation in both seasons. Mean CY for drip irrigation according to crop water requirement increased by 51% and 56% compared with deficit drip irrigation, whereas furrow irrigation based on crop water requirement increased by 52% and 54% compared with deficit furrow in Experiments 1 and 2, respectively. However, water use efficiency decreased with the increasing water volume.

    Simultaneous measurements of rate of photosynthesis based on gas exchange measurements and the thylakoid electron flux based on chlorophyll fluorescence were used to investigate physiological limitations to photosynthesis in leaves of deficit irrigated tomato plants under open field situations. Combined leaf gas exchange/chlorophyll fluorescence measurements differentiated the treatments effectively. Reduction in rate of photosynthesis, stomatal conductance and the maximum quantum efficiency of photosystem II varied across seasons of all varieties, whereas leaf temperature was increased by deficit irrigation in all varieties. Among varieties studied, Miya was found relatively tolerant to deficit irrigation. Stomatal limitation of rate of photosynthesis increased significantly as a result of water stress suggesting a strong influence of the stomatal behaviour.

    We also determined the influence of irrigation systems and strategies on water saving and tomato fruit quality. Using deficit drip irrigation was the best management strategy to optimize water use and tomato quality. Fruit dry matter content, acid content and total soluble solids were significantly higher with deficit drip irrigation than with other treatments.

    From this thesis it appeared that agro-climatic conditions, access to resources and culture all contribute to the relatively low yields of tomato in the Central Rift Valley of Ethiopia. The thesis also proved that significant advances can be made in yield, quality and resource use efficiency.

    Natural genetic variation in Arabidopsis thaliana photosynthesis
    Flood, P.J. - \ 2015
    Wageningen University. Promotor(en): Maarten Koornneef, co-promotor(en): Mark Aarts; Jeremy Harbinson. - Wageningen : Wageningen University - ISBN 9789462575004 - 278
    arabidopsis thaliana - genetische variatie - fotosynthese - genomen - chlorofyl - fenotypen - arabidopsis thaliana - genetic variation - photosynthesis - genomes - chlorophyll - phenotypes

    Oxygenic photosynthesis is the gateway of the sun’s energy into the biosphere, it is where light becomes life. Genetic variation is the fuel of evolution, without it natural selection is powerless and adaptation impossible. In this thesis I have set out to study a relatively unexplored field which sits at the intersection of these two topics, namely natural genetic variation in plant photosynthesis. To begin I reviewed the available literature (Chapter 2), from this it became clear that the main bottleneck restricting progress was the lack of high-throughput phenotyping platforms for photosynthesis. To address this an automated high-throughput chlorophyll fluorescence phenotyping system was developed, which could measure 1440 plants in less than an hour for ΦPSII, a measure of photosynthetic efficiency (Chapter 3). Using this phenotyping platform I screened five populations of Arabidopsis thaliana. Three of these populations resulted from bi-parental crosses and segregated for only two genomes, using these I conducted family mapping (Chapter 4). The final two populations were composed of natural, field collected, accessions and were analysed using a genome wide association approach (Chapter 5). The family mapping approach had greater statistical power due to within population replication and the genome wide association approach had higher mapping resolution due to historical recombination. Both approaches were used to identify genomic regions (loci) which were responsible for some of the variation in photosynthesis observed. The number and average effect of these loci was used to infer the genetic architecture of photosynthesis as a highly complex polygenic trait for which there are many loci of very small effect. In addition to screening these large populations a smaller subset of 18 lines was assayed for natural variation in phosphorylation of photosystem II (PSII) proteins in response to changing light (Chapter 6). This exploratory study indicated that this process shows considerable variation and may be important for adaptation of the photosynthetic apparatus to photosynthetic extremes. The genetic mapping studies just described, focus exclusively on genetic variation in the nuclear genome, whilst this contains the majority of the plants genetic information there is also a store of genetic information in the chloroplast and mitochondria. These genetic repositories contain genes which are essential for photosynthesis and energy metabolism. Any variation in these genes could have a large impact on photosynthesis. To study natural variation in these genomes I developed a new population of reciprocal nuclear-organellar hybrids (cybrids) which could be used to study the effect of genetic variation in organelles whilst controlling for nuclear genetic variation (Chapter 7). Preliminary results indicate that this resource will be of great use in disentangling natural genetic variation in nucleo-organelle interactions. Finally I looked at one chloroplast encoded photosynthetic mutation in more detail (Chapter 8). This mutation had evolved in response to herbicide application and had spread along British railways. When studying this population of resistant plants I found empirical evidence for organelle mediated nuclear genetic hitchhiking. This is a previously undescribed evolutionary phenomenon and is likely to be quite common. In conclusion there is an abundance of genetic variation in photosynthesis which can be used to improve the trait for agriculture and provide insights into novel evolutionary phenomena in the field.

    Het effect van licht op bio-aardappel vergroening in de retail
    Pereira da Silva, F.I.D.G. ; Otma, E.C. - \ 2015
    Wageningen : Wageningen UR & Biobased Research (Rapport / Wageningen UR Food & Biobased Research 1528) - ISBN 9789462573635 - 26
    consumptieaardappelen - achteruitgang (deterioration) - vergroening - chlorofyl - kunstlicht - supermarkten - biologische voedingsmiddelen - aardappelen - voedselkwaliteit - table potatoes - deterioration - greening - chlorophyll - artificial light - supermarkets - organic foods - potatoes - food quality
    Uit peilingen van de Nederlandse Aardappel Organisatie en andere, blijkt dat er nog steeds kwaliteitsgebreken vast te stellen zijn bij de biologische aardappels in het schap. Vergroening lijkt één van de belangrijkste aspecten van de kwaliteitsgebreken te zijn. Het doel van dit projectonderdeel is daarom om te onderzoeken welk type licht in de supermarkt leidt tot de beste resultaten om vergroening van bio-aardappels in het schap tegen te gaan.
    Imaging spectroscopy for ecological analysis in forest and grassland ecosystems
    Homolova, L. - \ 2014
    Wageningen University. Promotor(en): Michael Schaepman, co-promotor(en): Jan Clevers. - Wageningen : Wageningen University - ISBN 9789461738240 - 177
    remote sensing - naaldbossen - alpenweiden - picea abies - bladoppervlakte - ecofysiologie - ecosysteemdiensten - vegetatie - chlorofyl - cartografie - beeldvormende spectroscopie - remote sensing - coniferous forests - alpine grasslands - picea abies - leaf area - ecophysiology - ecosystem services - vegetation - chlorophyll - mapping - imaging spectroscopy

    Terrestrial vegetation is an important component of the Earth’s biosphere and therefore playing an essential role in climate regulation, carbon sequestration, and it provides large variety of services to humans. For a sustainable management of terrestrial ecosystems it is essential to understand vegetation responses to various pressures, to monitor and to predict the spatial extent and the rate of ecosystem changes. Remote sensing (RS) therefore offers a unique opportunity for spatially continuous, and for some type of RS data, also frequent monitoring of terrestrial ecosystems.

    RS of vegetation is a broad research field, where a lot of progress has been made in the last three decades. However, the complexity of interactions between vegetation and solar radiation, constantly modulated by environmental factors, offers room for deeper investigation. Rather than solving one big research problem, this thesis built a few bridges on a way leading towards better understanding of using airborne imaging spectroscopy for ecological analysis in temperate coniferous forests and subalpine grasslands. The research was divided into a theoretical and an applied part. The theoretical part contributed to a critical evaluation of research achievements and challenges in optical RS of plant traits (Chapter 2). The applied part addressed three research topics: i) investigating variability of total to projected leaf area ratio in spruce canopies and its implications on RS of chlorophyll content (Chapter 3), ii) testing chlorophyll retrieval methods based on continuum removal in spruce canopies (Chapter 4), and iii) exploring potentials of imaging spectroscopy to map ecosystem properties and the capacity of subalpine grasslands in providing ecosystem services in comparison with a plant trait-based modelling approach (Chapter 5).

    In Chapter 2, we reviewed achievements and challenges in RS estimation of key plant traits and we concentrated our discussion on eight traits with the strongest potential to be mapped using RS (plant growth and life forms, flammability properties, photosynthetic pathways and photosynthesis activity, plant height, leaf lifespan and phenology, specific leaf area, leaf nitrogen and phosphorous). The review indicated that imaging spectroscopy facilitates better retrievals of plant traits related to leaf biochemistry, photosynthesis and phenology rather than traits related to vegetations structure. Estimation of the canopy structure related traits (e.g. plant height) can certainly benefit from increasing synergies between imaging spectroscopy and active RS (radar or laser scanning). One of major challenges in RS of plant traits is to effectively suppress the negative influences of water absorption and canopy structure, which would facilitate more accurate retrievals of biochemical and photosynthesis-related traits. Secondly, a successful integration of RS and plant ecology concepts would require careful matching of spatial scales of in-situ trait data with RS observations.

    In Chapter 3, measurement methods and variability of total to projected leaf area within spruce crowns were investigated. Comparison of six laboratory methods revealed that methods using an elliptic approximation of a needle shape underestimated total leaf area compared to methods using a parallelepiped approximation. The variability in total to projected leaf area was primarily driven by the vertical sampling position and less by needle age or forest stand age. We found that total leaf area estimation has an important implication on RS of leaf chlorophyll content. An error associated with biased estimates of total leaf area can reach up to 30% of the expected chlorophyll range commonly found in forest canopies and therefore negatively influences the validation of RS-based chlorophyll maps. In Chapter 4, potentials of the continuum removal transformation for mapping of chlorophyll content in spruce canopies were investigated. We tested two methods based on continuum removal: artificial neural networks and an optical index. The optical index was newly designed here and it was based on the spectral continuum between 650 and 720 nm. Both continuum removal based methods exhibited superior accuracy in chlorophyll retrieval compared to commonly used narrow-band vegetation indices (e.g. NDVI, TCARI/OSAVI). The newly designed index was equally accurate, but certainly provided a more operational approach as compared to the neural network.

    In Chapter 5, mapping of ecosystem properties that underline ecosystem services provided by subalpine grasslands using RS methods was tested and further compared with a statistical plant trait-based modelling approach. Imaging spectroscopy in combination with empirical retrieval methods was partly successful to map ecosystem properties. The prediction accuracy at the calibration phase was comparable to the trait-based modelling approach. Spatial comparison between the two approaches revealed rather small agreement. The average fuzzy similarity between the approaches was around 20% for ecosystem properties, but in case of the total ecosystem service supply it decreased below 10%. However, the RS approach detected more variability in ecosystem properties and thereby in services, which was driven by local topography and microclimatic conditions, which could not be detected by the plant trait-based approach. Especially Chapters 2 and 5 indicated that one of the future RS research directions may be in spatial ecology, i.e. spatially explicit mapping of plant traits, ecosystem properties and ecosystem services. High quality RS data are certainly essential building elements for spatial ecology. But in order to address the effects of climate and land use changes on biodiversity and ecosystems, their properties and services, the integration of in-situ and RS data will be ultimately required. Therefore, more coherent experiments, where in-situ and RS data are measured simultaneously at different spatial scales, are needed in the future.

    Chlorophyll Fluorescence of seeds A non-destructive marker foor seed maturity and seed quality
    Jalink, H. - \ 2010
    fluorescentie - chlorofyl - zaden - methodologie - kwaliteitszorg - rijpheid - fluorescence - chlorophyll - seeds - methodology - quality management - maturity
    A method has been developed for the assessment of maturity and quality of seeds. The method is based on a non-destructive measurement of chlorop¬hyll-a in individual seeds.
    Beoordeling van Zaadkwaliteit met behulp van Chlorofyl Fluorescentie Beelden
    Jalink, H. - \ 2010
    zaadkieming - chlorofyl - embryo's - fluorescentie - zaden - technieken - capsicum - glastuinbouw - seed germination - chlorophyll - embryos - fluorescence - seeds - techniques - capsicum - greenhouse horticulture
    Tijdens het kiemingsproces van zaden wordt o.a. chlorofyl gevormd. Dit chlorofyl wordt aangemaakt door het embryo. Het is gebleken dat de toename van chlorofyl een maat is voor het verloop van het kiemingsproces. Dit chlorofyl kan gevoelig worden gemeten met een fluorescentietechniek.
    Sink stimulation of leaf photosynthesis by the carbon costs of rhizobial and arbuscular mycorrhizal fungal symbioses
    Kaschuk, G. - \ 2009
    Wageningen University. Promotor(en): Ken Giller; Thomas Kuijper, co-promotor(en): Peter Leffelaar; M. Hungria. - [S.l. : S.n. - ISBN 9789085853923 - 160
    fotosynthese - mycorrhizae - source-sink relaties - chlorofyl - fluorescentie - gebruiksefficiëntie - plantenvoeding - photosynthesis - mycorrhizas - source sink relations - chlorophyll - fluorescence - use efficiency - plant nutrition

    Key words: biochemical model of leaf photosynthesis; carbon sink strength; chlorophyll fluorescence; harvest index; leaf protein; leaf senescence; legumes; photosynthetic nutrient use efficiency; Pi recycling; source-sink regulation; ureides

    One of the most fascinating processes in plant physiology and agronomy is the capability of legumes to associate symbiotically with rhizobial bacteria and arbuscular mycorrhizal (AM) fungi. The legumes supply photosynthates in exchange for nitrogen, derived from biological N2 fixation, and soil nutrients mainly phosphate, obtained from foraging of AM fungi from the soil. The rhizobial and arbuscular mycorrhizal symbioses each may use 4-16% of recently fixed photosynthates to maintain their activity, growth and reserves, but in turn, may supply 100% of the plant nutrient requirements. The C costs of the symbioses are often assumed to limit plant productivity due to photosynthate competition between the microsymbiont and the host. In addition, the C costs are often used as an entry point to understand the evolution of the symbioses.
    It is intriguing that despite of the symbiotic C costs, plants associated with rhizobia and/or AM fungi often produce more biomass and grains than fertilized plants. Increases in plant growth are traditionally attributed to improved plant nutrition and enhanced photosynthesis. This thesis gives evidence that plants – and particularly legumes – are able to overcome any putative C limitation associated with rhizobial and AM fungal symbioses by increasing the rates of photosynthesis due to sink stimulation, over and above the expected nutritional benefits from the symbioses. Sink stimulation of photosynthesis is a consequence of increased C demand from photosynthesis, which increases the export of triose-P from chloroplasts, recycling more inorganic phosphates and activating more photosynthetic enzymes. In the thesis, I report a literature study, which provides a framework for the quantification of sink stimulation of photosynthesis. Apparently, sink stimulation of photosynthesis by symbioses just equals the C costs, which in the long term is still beneficial for plant growth. Sink stimulation of photosynthesis implies that plants and symbioses are not limited by photosynthates, which means that the cost : benefit theories for symbioses need to be re-conceptualized.
    Photosynthesis is limited by three biochemical processes: rubisco activity, electron transport, and triose-P export (often referred as sink limitation). In Chapter 3, I apply a biochemical model expressing these three limitations in CO2 response curves of soybean (Glycine max [L.] Merrill) inoculated with rhizobial strains with putative different C costs (Bradyrhizobium japonicum CPAC 390 or CPAC 7) or fertilized with KNO3, to understand the effects of rhizobial symbioses on the photosynthetic capacity. Plants associated with putatively more expensive strains have higher photosynthetic capacity than those associated with less ‘expensive strains’. The effect of sink stimulation of photosynthesis is evident because plants with higher triose-P export rates consistently had higher rates of electron transport and rubisco activity. These results suggest that the C costs of rhizobial symbioses generate feedbacks between the rates of triose-P export with rubisco activity and electron transport rates.
    I also describe three subsequent experiments with two different soybean varieties nodulated with two rhizobial strains or fertilized with two doses of KNO3 fertilizer. Plants associated with rhizobial symbioses always had higher rates of photosynthesis and accumulated less starch in the leaves than N-fertilized plants throughout the whole cycle. Furthermore, nodulated plants maintained higher chlorophyll concentrations for a longer period than N-fertilized plants. Both photosynthesis and N2 fixation were synchronized over the plant cycle. One of the conclusions of Chapter 4 is that C costs of rhizobial symbioses lead to sink stimulation of photosynthesis, which in turn, delays leaf senescence. These mechanisms together are likely to contribute for increase in plant productivity.
    Overall, the thesis indicates that the C costs of symbioses are not disadvantageous, as usually thought. Higher activity of rhizobial and AM fungal symbioses results in sink stimulation of photosynthesis, which leads to higher plant growth over time. Sink stimulation of photosynthesis implies that the microsymbionts and plants are not limited by photosynthate. Increased rates of photosynthesis in initial stages of plant development delay the rates of leaf senescence in the later stages of plant development. The C costs of symbioses bring advantages to the plant’s adaptation under elevated CO2 concentration, because they remove the sink limitation of photosynthesis. It means that effectiveness of the symbioses (the capacity to supply nutrients) is more important than the C costs or the efficiency with which photosynthates are used.

    Visiontechnieken brengen zichtbare en onzichtbar kenmerken in beeld
    Pekkeriet, E.J. - \ 2008
    Onder Glas 5 (2008)12. - p. 5 - 7.
    tuinbouwbedrijven - sierplanten - machine vision - computertechnieken - videocamera's - chlorofyl - gewaskwaliteit - infraroodspectrofotometrie - röntgenstraling - glastuinbouw - groenten - potplanten - market gardens - ornamental plants - machine vision - computer techniques - video cameras - chlorophyll - crop quality - infrared spectrophotometry - x radiation - greenhouse horticulture - vegetables - pot plants
    Binnen de glastuinbouw wordt de 2D-visiontechniek al volop toegepast bij het sorteren en het bepalen van de kwaliteit. Nieuw is het aansturen van een robotarm. Nog nieuwer zijn de verschillende 3-D-technieken, zoals lasertriangulatie, stereovisie, 'volumetric intersection' en visiontechnieken die buiten het zichtbare spectrum werken
    Optimalisatie van de stikstofbemesting van Engels raaigras
    Schoot, J.R. van der - \ 2007 2007 (2007)15 jan.
    akkerbouw - stikstofmeststoffen - lolium perenne - zaadproductie - chlorofyl - bemesting - rassen (planten) - cultivars - mestgiften - stikstof - arable farming - nitrogen fertilizers - lolium perenne - seed production - chlorophyll - fertilizer application - varieties - cultivars - dressings - nitrogen
    In het stikstofadvies voor Engels raaigras, zoals vastgesteld in onderzoek van PA(G)V in de periode 1978-1984, wordt geen onderscheid gemaakt naar typen en rassen en wordt aanbevolen de benodigde hoeveelheid stikstof éénmalig in het vroege voorjaar te verstrekken. Gezien de grote verschillen in gewasstructuur en ontwikkelingssnelheid die er bij de verschillende typen en rassen van Engels raaigras bestaan, kan het stikstofadvies vermoedelijk worden verfijnd. Deling van de stikstofgift kan, al of niet met behulp van de chlorofylmeter, daarnaast ook zorgen voor lagere oogstrisico's of betere opbrengsten. In opdracht van het Productschap Granen, Zaden en Peulvruchten is daarom onderzoek uitgevoerd naar typen en rassen bij verschillende bemestingsniveau's, de gebruiksmogelijkheden van de chlorofylmeter en de effecten van deling van stikstof.
    Herstelmaatregelen in ondiepe meren: zijn de verbeteringen blijvend?
    Nes, E.H. van; Lammens, E. ; Roijackers, R.M.M. ; Veeningen, R. - \ 2007
    H2O : tijdschrift voor watervoorziening en afvalwaterbehandeling 40 (2007)1. - ISSN 0166-8439 - p. 29 - 32.
    meren - eutrofiëring - baggeren - chlorofyl - fosfaten - nitraten - evaluatie - onderzoek - herstel - vissen - nederland - denemarken - biologisch waterbeheer - maatregelen - eutrophication - dredging - chlorophyll - phosphates - nitrates - evaluation - research - rehabilitation - fishes - netherlands - denmark - lakes - biological water management - measures
    In deze studie evalueren we gegevens van 28 Nederlandse en 50 Deense meren waar effectgericht maatregelen zijn toegepast, waaronder voornamelijk actief biologisch beheer door afvissen van brasem en blankvoorn. Daarnaast zijn in sommige meren ook andere maatregelen toegepast, zoals baggeren en chemische fosfaatfixatie in het sediment. In meer dan de helft van de gevallen was actief biologisch beheer succesvol op de korte termijn. In sommige gevallen nam niet alleen het chlorofyl-, maar ook de fosfor- en stikstofgehaltes sterk af. Op de lange termijn was de heldere toestand in de meeste gevallen echter niet stabiel
    Weed-It : selectieve onkruidbestrijding m.b.v. een chlorophyl-sensor
    Zedde, H.J. van de; Timmermans, A.J.M. - \ 2007
    onkruidbestrijding - chlorofyl - sensors - weed control - chlorophyll - sensors
    Eén van de oplossingen om te komen tot een milieuvriendelijker en kosteneffectieve manier van onkruidbeheer is het selectief behandelen van onkruid daar waar het daadwerkelijk groeit. Greenvision heeft een machine ontwikkeld voor selectieve onkruidbestrijding op verhardingen
    Aanvullende COCO-berekeningen in het kader van nazorg van het DynAqua-project (kokkelkweek deel)
    Vries, P. de; Veenstra, F.A. - \ 2007
    Den Helder : IMARES (Rapport / Wageningen IMARES nr. C096/07) - 23
    schaaldieren - kokkels - groei - groeitempo - groeimodellen - watertemperatuur - chlorofyl - zwevende deeltjes - organische stof - mariene ecologie - shellfish - clams - growth - growth rate - growth models - water temperature - chlorophyll - suspended solids - organic matter - marine ecology
    COCO (COmputer COckle model) is ontwikkeld door het voormalig Nederlands Instituut voor Visserij Onderzoek (RIVO), tegenwoordig bekend als Wageningen IMARES. COCO berekent ondermeer de groei van een individuele kokkel, maar kan ook informatie met betrekking tot de productie van pseudo-feces opleveren. Het model bevat feedback loops bij de opname en het metabolisme van voedsel en het verdelen van koolstof naar de verschillende interne toestandsvariabelen: somatisch weefsel, opslag (glycogeen), organische schelpmatrix en gameten. In de eerste plaats is het de bedoeling met deze rapportage een sterkere link van de COCO-modelberekeningen (uitgevoerd in het kader van het DynAqua-project) met de praktijk te leggen. Hieraan wordt vorm gegeven met aanvullende berekeningen, die in dit rapport beschreven worden.
    Zonder magnesium zouden planten niet groen zijn
    Heuvelink, E. ; Kierkels, T. - \ 2007
    Onder Glas 4 (2007)9. - p. 40 - 41.
    chlorofyl - plantenfysiologie - plantenontwikkeling - magnesium - fysiologische functies - gewassen, groeifasen - voedingsstoffenbehoeften - glastuinbouw - chlorophyll - plant physiology - plant development - magnesium - physiological functions - crop growth stage - nutrient requirements - greenhouse horticulture
    Magnesium is het centrale element in het molecuul van het bladgroen. Bij een gebrek kleuren daarom de bladeren geel tussen de nerven. Zware metalen kunnen de plaats van magnesium in het bladgroen innemen. De plant kan dan niet meer assimileren. Magnesium is verder belangrijk bij heel veel processen in de plant
    Green vegetables and colon cancer: the mechanism of a protective effect by chlorophyll
    Vogel, J. de - \ 2006
    Wageningen University. Promotor(en): M.B. Katan; Roelof van der Meer. - [S.l. ] : S.n. - ISBN 9789085043478 - 151
    colorectaal kanker - bladgroenten - chlorofyl - vlees - carcinogenese - ratten - dierproeven - colorectal cancer - leafy vegetables - chlorophyll - meat - carcinogenesis - rats - animal experiments
    One of the important environmental determinants of the risk of colon cancer is the composition of the diet. Regular consumption of high amounts of red meat increases colon cancer risk. In contrast, consumption of green vegetables decreases the risk of colon cancer. This thesis provides a molecular mechanism of how these two dietary components might modulate colon cancer risk.
    Applying prior knowledge to model batch keeping-quality of cucumber batches
    Schouten, R.E. ; Tijskens, L.M.M. ; Kooten, O. van; Jongbloed, G. - \ 2004
    In: Bayesian statistics and quality modelling in the agro-food production chain : proceedings of the Frontis workshop on Bayesian statistics modelling in the agro-food production chain, Wageningen, The Netherlands 11 - 14 May 2003 / van Boekel, M.A.J.S., Stein, A., van Bruggen, A.H.C., Wageningen : Frontis (Wageningen UR Frontis series Vol. 3) - ISBN 9781402019166 - p. 71 - 80.
    komkommers - houdbaarheid (kwaliteit) - variatie - chlorofyl - rijp worden - cultivars - bewaartijd - bewaarfysiologie - kleur - cucumbers - keeping quality - variation - chlorophyll - ripening - cultivars - storage life - postharvest physiology - colour
    Keeping-quality of individual cucumbers is limited by the green colour; the keeping-quality of batches of cucumbers is limited by the time it takes before 5␘f the cucumbers in the batch reach a predefined colour limit. From literature concerning the synthesis and degradation of chlorophyll and a published colour model (Schouten, Tijskens and Van Kooten 2002) it is known that colour behaviour of individual cucumbers depends on the concentration of protochlorophyllide (Pchl), at harvest. Here a model for the synthesis and degradation of Pchl is proposed for individual cucumbers, assuming that light conditions during growth are a major factor for Pchl synthesis. Subsequently, this individual Pchl model is expanded to a batch model that describes the variation in the Pchl concentration by assuming that differences between cucumbers of the same batch are primarily caused by differences in light conditions during growth. Pchl data were obtained from colour data from six batches from three cultivars (¿Volcan¿, ¿Beluga¿ and ¿Borja¿) over two growing seasons. Pchl data were gathered per batch and compared with the proposed batch model. The variation in the Pchl concentration per batch could be described satisfactorily in terms of the parameters of the proposed Pchl batch model: batch maturity, batch variation (due to differences in light conditions during growth on a batch level) and a cultivar-dependent factor. Estimating this cultivar-dependent factor for new cultivars could be a tool for cucumber-breeding companies to obtain cultivars with an increased keeping-quality. Keywords: Biological variation; postharvest; preharvest; precursor
    Onttrekking en natuurlijke productie van schelpdieren in de Nederlandse Waddenzee in de periode 1976-1999
    Brinkman, A.G. ; Smaal, A.C. - \ 2003
    Wageningen : Alterra (Alterra rapport 888) - 243
    schaal- en schelpdierenvisserij - schaaldieren - draagkracht - ecologie - voedingsstoffen - eutrofiëring - biomassa productie - modellen - chlorofyl - nederland - waddenzee - shellfish fisheries - shellfish - carrying capacity - ecology - nutrients - eutrophication - biomass production - models - chlorophyll - netherlands - wadden sea
    Onderzocht is in hoeverre de factoren die de draagkracht van het Waddenzee-ecosysteem voor schelpdieren bepalen onderhevig zijn aan lange-termijnveranderingen. Draagkracht is hierbij gedefinieerd als de maximale biomassa van schelpdieren die in de Waddenzee kan bestaan. Gebruik is gemaakt van het dynamische simulatiemodel EcoWasp; het systeemgedrag is doorgerekend voor de periode 1976-1999. Daarnaast is met behulp van een statistische toetsing de relatie tussen de conditie van schelpdieren en het gehalte aan chlorofyl onderzocht. Het onderzoek heeft zich beperkt tot de westelijke helft van de Nederlandse Waddenzee.
    Chlorophyll Fluorescence : a general description and nomenclature
    Rosenqvist, E. ; Kooten, O. van - \ 2003
    In: Practical Applications of Chlorophyll Fluorescence in Plant Biology / Dell, J.R., Toivonen, P.M.A., Dordrecht, the Netherlands : Kluwer Academic Publishers - ISBN 9781402074400 - p. 31 - 77.
    fluorescentie - chlorofyl - source-sink relaties - fluorescence - chlorophyll - source sink relations
    A general description and nomenclature of chlorophyll fluorescence with attention to: where chlorophyll fluorescence comes from, how it is measured and what do the measurements reflect
    Lake age and water level affect the turbidity of floodplain lakes along the lower Rhine
    Roozen, F.C.J.M. ; Geest, G.J. van; Ibelings, B.W. ; Roijackers, R.M.M. ; Scheffer, M. ; Buijse, A.D. - \ 2003
    Freshwater Biology 48 (2003). - ISSN 0046-5070 - p. 519 - 531.
    geologische sedimentatie - waterkwaliteit - troebelheid - chlorofyl - vegetatie - oppervlaktewater - uiterwaarden - waterstand - rijn - geological sedimentation - water quality - turbidity - chlorophyll - vegetation - surface water - river forelands - water level - river rhine - wind-induced resuspension - sediment resuspension - benthivorous fish - shallow lakes - hydrological connectivity - phytoplankton biomass - community structure - chlorophyll-a - plankton
    1. We sampled a set of 93 lakes situated in the floodplains of the lower River Rhine in search for morphometric and other factors that explain their variation in clarity. 2. Lakes with a drop in summer water level were less turbid at the time of sampling, mainly because of a lower concentration of inorganic suspended solids (ISS). 3. We also found that older lakes were more turbid than younger lakes and that this was largely because of an increase in phytoplankton. 4. Water clarity was positively related to lake depth and the presence of vegetation. 5. Model calculations indicated that the underwater light climate was strongly affected by chlorophyll and ISS, the latter being the dominant factor affecting Secchi depth. Dissolved organic carbon (DOC) was less important. 6. The high concentration of ISS suggests that intensive resuspension occurs in most of the lakes. Using a simple wave model, and assuming that vegetation protects sediments against resuspension, we could eliminate wind resuspension as an important process in 90% of the lakes, leaving resuspension by benthivorous fish as probably the most important factor determining transparency. 7. Chlorophyll a concentration showed a strong positive correlation to ISS concentration, suggesting that resuspension may also have a positive effect on phytoplankton biomass in these lakes. 8. In conclusion, in-lake processes, rather than river dynamics, seem to be driving the turbidity of floodplain lakes along the lower River Rhine.
    Monitoring crops using chlorophyll fluorescence
    Costa, J.M. ; Snel, J.F.H. ; Harbinson, J. - \ 2003
    FlowerTECH 6 (2003)4. - ISSN 1388-8439 - p. 2 - 4.
    remote sensing - toepassingen - chlorofyl - fotosynthese - fluorescentie - bloementeelt - instrumenten (meters) - applications - chlorophyll - photosynthesis - fluorescence - floriculture - instruments
    Met chlorofyl-fluorescentiemetingen de fotosynthese van planten meten
    An Introduction to Chlorophyll Fluorescence
    Harbinson, J. ; Rosenqvist, E. - \ 2003
    In: Practical Applications of Chlorophyll Fluorescence in Plant Biology / Dell, J.R., Toivonen, P.M.A., Dordrecht, the Netherlands : Kluwer Academic Publishers - ISBN 9781402074400 - p. 1 - 29.
    fluorescentie - chlorofyl - fotosynthese - fluorescence - chlorophyll - photosynthesis
    Photosynthesis is a physiological process that couples the energy of light to certain metabolic changes in biochemical reactions, via photochemical processess. It is the purpose of this chapter to lay out the basic physical and physiological processess associated with this coupling and to show how the biochemical changes are linked to other physical processess that allow us to measure the operation and progress of the coupling of light-absorption to physiology
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