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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    Convergent xylem widening among organs across diverse woody seedlings
    Zhong, Mengying ; Castro-Díez, Pilar ; Puyravaud, Jean Philippe ; Sterck, Frank J. ; Cornelissen, Johannes H.C. - \ 2019
    New Phytologist 222 (2019)4. - ISSN 0028-646X - p. 1873 - 1882.
    leaf area - organs - plant size - stem height - tissue density - vessel diameter - xylem anatomy

    Xylem conduit diameter (D max ) of woody angiosperm adults scales with plant size and widens from the stem apex downwards. We hypothesized that, notwithstanding relative growth rate (RGR), growth form or leaf habit, woody seedling conduit D max scales linearly with plant size across species; this scaling should be applicable to all vegetative organs, with consistent conduit widening from leaf via stem to main root and coupling with whole-leaf area and whole-stem xylem area. To test these hypotheses, organ-specific xylem anatomy traits and size-related traits in laboratory-grown seedlings were analyzed across 55 woody European species from cool-temperate and Mediterranean climates. As hypothesized, conduit D max of each organ showed similar scaling with plant size and consistent basipetal widening from the leaf midvein via the stem to the main root across species, independently of growth form, RGR and leaf habit. We also found a strong correlation between D max and average leaf area, and between stem xylem area and whole-plant leaf area. We conclude that seedlings of ecologically wide-ranging woody species converge in their allometric scaling of conduit diameters within and across plant organs. These relationships will contribute to modeling of water transport in woody vegetation that accounts for the whole life history from the trees’ regeneration phase to adulthood.

    Air purification by house plants : a literature survey
    Visser, Pieter de - \ 2017
    Bleiswijk : Wageningen Plant Research (Report / WPR 695) - 19
    air quality - plants - research - root systems - leaf area - luchtkwaliteit - planten - onderzoek - wortelsystemen - bladoppervlakte
    Within the project ‘Plant champion air purification’, a public-private cooperation, a literate survey was carried out to explore recent findings on the possibilities of plants to purify indoor contaminated air. Literature was searched in academic journals, on the internet and within reports recently carried out for the horticultural sector. Here this knowledge is shortly described. Plants generally have the capacity to assimilate hydrophilic Volatile Organic Compounds (VOCs) like formaldehyde without harm. Lipophilic VOCs are less well assimilated and follow different uptake pathways. Differences between plant species can sometimes be related to amount of leaves, wax layer composition, stomatal conductance or hairs. Apart from the green plant parts, the roots, the micro-organisms and rooting medium have a role in air purification. The research in plant chambers mainly generated knowledge on short term uptake of volatiles, but the uptake mechanisms and the long-term performances of plants are only partly understood. The research on upscaling of lab results to air purification in rooms within buildings is still in its infancy. A few good studies have been done and show promising results, but most research was statistically poor. More research is needed to extrapolate the findings from lab research to practice.
    Philosophising about The New Crop : 'Open crop can bring forward production and save energy'
    Gelder, Arie de - \ 2016
    horticulture - greenhouse horticulture - vegetables - tomatoes - plant development - crop production - energy saving - yields - leaf area - agricultural research

    Research into the extreme removal of leaves from tomato plants has yielded surprising results. Not only does it seem possible to bring forward production by removing extra leaves but it also saves energy. The challenge now will be to see if the results achieved in research units at Wageningen UR Greenhouse Horticulture can be reproduced in practice

    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.

    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.
    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.

    Bladschade bij Potanthurium: onderzoek naar mogelijke oorzaken, 2012
    Garcia Victoria, Nieves - \ 2013
    pot plants - anthurium - leaf area - damage - plant pests - agricultural research
    Physiological ecology of the frankincense tree
    Mengistu Woldie, T. - \ 2011
    Wageningen University. Promotor(en): Frans Bongers; G. Fetene, co-promotor(en): Frank Sterck. - S.l. : s.n. - ISBN 9789085859277 - 127
    boswellia - koolstof - ecologie - plantenfysiologie - tappen (rubber) - bosgebieden - koolhydraten - bladoppervlakte - bomen - harsen - harswinning - ethiopië - boswellia - carbon - ecology - plant physiology - tapping - woodlands - carbohydrates - leaf area - trees - resins - resin extraction - ethiopia

    Keywords: Boswellia papyrifera, carbon balance, drylands, Ethiopia, frankincense, tapping

    The degradation of frankincense tree dominated woodlands has been attributed to climatic
    conditions and human activities. We lack however information on how such factors influence the
    resource balance and productivity of trees. The aim of this study was to evaluate the impact of
    resin tapping on the whole tree carbon gain, storage and allocation pattern of frankincense trees
    (Boswellia papyrifera (Del.) Hochst) in the dry woodlands of northern Ethiopia. I hypothesized
    that the intensive resin tapping of frankincense trees reduces tree vitality, particularly under
    relatively dry conditions. I established experimental plots in the highland woodlands of
    Abergelle and the lowland woodlands of Metema, and applied tapping treatments to similar sized
    adult trees (DBH 20 +/- 3cm). For these trees I also collected data on leaf gas exchange, crown
    traits, carbon storage, carbon allocation, growth and frankincense production during a period of
    two years (2008-2009).
    Trees follow similar leaf gas exchange patterns in contrasting environments, but differ in
    annual crown carbon gain between highland and lowland sites. Highland trees of Boswellia had a
    higher photosynthetic capacity, were exposed to higher light conditions, but had a shorter leaf
    lifespan than lowland trees. Integrating these effects, I showed that the annual crown carbon gain
    is higher in the highland trees than in lowland trees. Lowland trees are mainly constrained by
    clouded conditions and resultant low light levels during the wet season, limiting their carbon
    gain. Moreover, carbon gain was also restricted by atmospheric drought, and much less by soil
    water deficit during the growing season. The production of frankincense was not affected by the
    annual tree carbon gain implying that trees with smaller total leaf area may suffer sooner from
    carbon starvation by tapping.
    Tapping reduced storage carbohydrate concentrations in wood, bark and root tissues
    indicating that continuous tapping depletes the carbon reserves. A large part of the carbohydrate
    concentration in the plant tissues was starch. Boswellia trees have more total nonstructural
    carbohydrates (TNC) concentrations and pool sizes in wood than in root and bark tissues.
    Because tapped trees face depleting carbon storage pools during the dry tapping season and
    cannot fully replenish these pools during the wet season, tapped trees may face higher risks of
    carbon starvation compared to untapped trees in the long term.
    Estimated total annual carbon sinks to the different plant components were 38-68% of the
    annual carbon gain in both study sites. However, Boswellia trees also establish mycorrhizal
    associations which may consume an additional 20% of gross primary production. On a wholetree
    basis, the percentage of autotrophic respiration may exceed all other costs. The foliage
    construction costs and incense production are the second and third largest carbon sinks,
    respectively. Contrary to our expectation, the sum of all dry season carbon costs was higher than
    the total amount of consumed TNC during the dry season. The high carbon costs during the dry
    season imply that trees do not fully depend on TNC to pay for the carbon costs during the dry
    season. With the exception of carbon allocation to foliage production and maintenance, a higher
    gross primary production does not enhance an overall increase in carbohydrate investments in
    the other sinks. Therefore, the carbon allocation pattern is constrained not exclusively by the
    absolute amount of carbon gained but also by other factors.
    The results clearly indicate that continuous tapping depletes the amount of stored carbon,
    the leaf area production and the reproductive effort. These negative effects were however site
    specific and could possibly be apparent sooner for smaller trees than for larger ones. Thus,
    guidelines for resin tapping of Boswellia trees should consider tapping intensity, tapping
    frequency, environmental conditions and tree size and should focus on maintaining vital trees
    and populations for the future.

    Air humidity, stomata & transpiration
    Nederhoff, E.M. - \ 2009
    Practical Hydroponics & Greenhouses 2009 (2009)109. - ISSN 1321-8727 - p. 37 - 42.
    hydrocultuur - transpiratie - relatieve vochtigheid - huidmondjes - wateropname (planten) - poriën - bladoppervlakte - hydroponics - transpiration - relative humidity - stomata - water uptake - pores - leaf area
    The plant's water status is the balance of water uptake and water loss. Transpiration (water loss) in influenced by sun, wind humidity, leaf area, and opening of stomatal pores in the leaves.
    Schadedrempels voor Botrytis en Stemphylium in asperge : proefjaren 1999-2005
    Plentinger, M.C. ; Wilms, J.A.M. ; Schepers, H.T.A.M. - \ 2006
    Lelystad : Praktijkonderzoek Plant & Omgeving, Sector AGV
    proeven op proefstations - groenteteelt - veldgewassen - asparagus - gewasbescherming - chemische bestrijding - schimmelziekten - botrytis - stemphylium - bladoppervlakte - productie - station tests - vegetable growing - field crops - asparagus - plant protection - chemical control - fungal diseases - botrytis - stemphylium - leaf area - production
    Op het proefbedrijf PPO AGV te Horst is in 1999 een veldproef aangelegd om een systeem voor gerichte bestrijding van Botrytis en Stemphylium in asperge, met een zo minimaal mogelijk middelengebruik, te ontwikkelen. In de veldproef waren, naast een onbehandeld object, vier varianten opgenomen waarbij gewasbeschermingsmiddelen werden toegepast. Daarnaast lagen drie objecten in de proef waarbij een vroegtijdige aftakeling van het gewas werd gesimuleerd. Door het verwijderen van de helft van het aantal stengels begin augustus, september of oktober werd een indicatie verkregen van het effect van vroegtijdig assimilatieverlies op de productie in volgende jaren. In 2001 tot en met 2005 werd geoogst.
    Jong blad plukken kan heel nuttig zijn
    Heuvelink, E. ; Kierkels, T. - \ 2005
    Onder Glas 2 (2005)3. - p. 4 - 5.
    tuinbouw - vruchtgroenten - opbrengsten - gewasopbrengst - gewasproductie - plantenveredeling - metabolisme - bladoppervlakte - agrarische bedrijfsvoering - glastuinbouw - groenten - horticulture - fruit vegetables - yields - crop yield - crop production - plant breeding - metabolism - leaf area - farm management - greenhouse horticulture - vegetables
    Om vooral bij vruchtgroenten een zo hoog mogelijke productie te behalen is het belangrijk dat een zo groot mogelijk deel van de assimilaten naar de vruchten gaat. In onderzoek gaf het weghalen van één op de twee jonge bladeren een tien procent hogere productie. Wel moet daarbij het aantal vierkante meters bladoppervlak per vierkante meter grondoppervlak op peil blijven
    Meer licht onderscheppen voor meer tomaten
    Kaarsemaker, R.C. - \ 2005
    Groenten en Fruit. Algemeen (2005)29. - ISSN 0925-9694 - p. 14 - 15.
    tomaten - belichting - gewasproductie - bladoppervlakte - licht - solanum lycopersicum - glastuinbouw - tomatoes - illumination - crop production - leaf area - light - solanum lycopersicum - greenhouse horticulture
    Licht is de basis voor de fotosynthese en daarmee de belangrijkste productiefactor voor een tomatengewas. Het gewas moet dan ook zoveel mogelijk licht opvangen. Zowel het totale bladoppervlak als de verticale verdeling van het bladoppervlak zijn daarvoor belangrijk
    Optimaal bladoppervlak levert geld op : voorzichtig zijn met teveel blad plukken bij tomaat
    Heuvelink, E. ; Kierkels, T. - \ 2005
    Onder Glas 2 (2005)2. - p. 14 - 15.
    tomaten - solanum lycopersicum - plantenontwikkeling - bladoppervlakte - bladoppervlakte-index - ontbladering - assimilatie - netto-assimilatiesnelheid - glastuinbouw - groenten - tomatoes - solanum lycopersicum - plant development - leaf area - leaf area index - defoliation - assimilation - net assimilation rate - greenhouse horticulture - vegetables
    Uit onderzoek blijkt dat sommige tomatentelers tot 10% meer licht weten te vangen dan andere telers. In principe betekent dat ook een 10% hogere productie. Het onderzoek bewijst: zorg voor een hoge lichtonderschepping door het gewas. Dat zorgt voor een optimale productie en optimale benutting van duur assimilatielicht. Gegevens in bijgaande grafiek: De hoeveelheid licht die het gewas onderschept loopt op naarmate het aantal vierkante meters blad per grondoppervlak groter is, tot een bepaalt maximum is bereikt
    Leaves make a difference in cut rose propagation
    Costa, J.M. ; Pol, P.A. van de - \ 2004
    FlowerTECH 7 (2004)1. - ISSN 1388-8439 - p. 21 - 23.
    rosa - snijbloemen - bladeren - bladoppervlakte - hergroei - rosa - cut flowers - leaves - leaf area - regrowth
    The importance of leaves on the cuttings or stentlings should not be undermined when it comes to the survival and quality of the resulting young plants for cut roses
    Energiebesparing door bladplukken bij paprika: haalbaarheidsstudie op basis van modellen
    Grashoff, C. ; Stanghellini, C. ; Kempkes, F.L.K. ; Elings, A. ; Marcelis, L.F.M. - \ 2003
    Wageningen : Plant Research International (Nota / Plant Research International 310) - 15
    capsicum annuum - bladoppervlakte - bladoppervlakte-index - kassen - teelt onder bescherming - nederland - paprika - energiebesparing - capsicum annuum - leaf area - leaf area index - greenhouses - protected cultivation - netherlands - sweet peppers - energy saving
    Met behulp van simulatiemodellen werd een haalbaarheidsstudie uitgevoerd naar de effecten van bladplukken op energiebesparing en rendementsverbetering bij paprika. Deze studie leverde het volgende op: 蛮 Eenmalige bladpluk (van LAI=6 terug naar LAI=3) geeft een waterbesparing van 11%, een energiebesparing van 5% bij een opbrengststijging van 1%. Het netto financiële resultaat hangt sterk af van de prijzen voor gas, arbeid (voor bladplukken) en product. Voor de berekeningen die het meest overeenkomen met huidig prijspeil schatten wij dat het financiële resultaat ligt tussen € 1050, - winst per hectare (bij een uurloon van € 15,- ) en € 820,- verlies per hectare (bij een uurloon van € 20,-). 蛮 Het gunstigste moment voor bladplukken is in augustus. 蛮 Deze resultaten zijn gebaseerd op de klimaatinstellingen van een teler die nu reeds energiezuinig teelt. Een gemiddelde tuinder gebruikt 10% meer energie, maar de berekende resultaten van bladplukken zijn vergelijkbaar. 蛮 Wekelijks bladplukken lijkt minder perspectiefvol. Weliswaar is de energiebesparing dan groter (8%), maar het positieve effect op productie is kleiner. De kosten voor bladplukken zullen naar verwachting hoger zijn. De resultaten zijn op 11 december 2003 besproken met de tuinders in een vergadering van de Landelijke commissie paprika van LTO. Daarbij is gediscussieerd over de toepassingsmogelijkheden in de praktijk en hebben we de tuinders gevraagd of ze perspectief zien in een nadere toetsing in de praktijk. De tuinders ondersteunen een praktijktoetsing, waarbij ze enkele randvoorwaarden hebben aangegeven. De reacties van de tuinders zijn weergegeven in dit rapport.
    The role of the leaf on the dynamics of growth and rooting of leafy stem cuttings of rose
    Cunha Costa, J.M.R. da - \ 2002
    Wageningen University. Promotor(en): H. Challa; M.T.M. Willemse; U. van Meeteren; P.A. van de Pol; C.J. Keijzer. - S.l. : S.n. - ISBN 9789058086877 - 187
    rosaceae - rozen - stekken - bladeren - wortels - beworteling - stengels - fotosynthese - groei - plantengroeiregulatoren - bladoppervlakte - plantenvermeerdering - voedingsstoffenreserves - rosaceae - roses - cuttings - leaves - leaf area - roots - rooting - stems - photosynthesis - growth - plant growth regulators - propagation - nutrient reserves

    Key words : Rosa hybrida , cut-rose, propagation, cuttings, leaf, rooting, root initiation, root growth, axillary primary shoot, severance, photosynthesis, carbohydrates, reduced sink activity, planting material, quality

    The present study aims at better understanding the relation between photosynthesis of the original leaf, carbohydrates, rooting and growth of single node leafy stem cuttings of rose. This knowledge can be used to improve success and efficiency in propagation and improving the uniformity of the planting material of cut roses derived form cuttings.

    The effects of the original leaf area on the growth of cuttings of Rosa hybrida Madelon ®were investigated during the first 10 weeks after severance. Total plant dry weight, and dry weight of the roots in particular, were proportionally related with the original leaf area of cuttings. When leaf area was modified, leaf area duration was linearly related to the rooting and growth of cuttings during the first 21 days of propagation. The presence of the leaf during the first week of propagation was critical for survival and its removal caused stem rot. This was caused by low carbohydrate concentrations.

    Cuttings remained photosyntheticaly active after severance. Photosynthetic rates decreased immediately after severance, but recovered up to 70% of the rates measured on leaves on mother plants and remained constant during propagation. The PSII efficiency decreased during propagation with a simultaneous increase in its heterogeneity across the leaflets (patchiness) which may be attributed to decreased sink activity rather then to water stress. The root and shoot tissues accounted for about 70% of the increase in total fresh weight after 21 days of propagation, whereas the remaining 30% increase was due to dry weight accumulation in the leaf and stem. About 55% of the dry weight accumulated consisted of carbohydrates, in particular starch, which accumulated mainly in the first 14 days in leaves and stem tissues (pith and medullar rays). This accumulation may be explained by reduced meristematic sink activity following severance. In fact, the newly formed roots and primary shoot after 21 days of propagation only represented 10% of the total dry weight of cuttings.

    Reduced light integrals and low CO 2 concentrations resulted in reduced rooting and growth of cuttings and decreased carbohydrate levels. Number of roots, and particularly, dry weight of roots, were linearly related with total dry weight accumulation during the 21 days of propagation showing that photosynthetic activity of cuttings during propagation influences both root initiation and growth. The effects of low light, low CO 2 concentration, and leaf area reduction on rooting and growth of cuttings were similar indicating that these effects could be explained to a great extent by photosynthesis. Growth in general depended on the length of the period cuttings were photosynthetically active during propagation. An exception was the growth of the axillary primary shoot, which was more negatively affected by reduced photosynthetic activity in the first 11 days of propagation. Root initiation was also more negatively affected by low photosynthetic activity in the first 11 days of propagation whereas root growth responded to the integral of photosynthesis. Cuttings were able to efficiently use reserves for growth. Optimal rooting and further growth of cuttings rely on the synthesis of new photosynthates because storage is limited in single node stem cuttings.

    Rooting of cut roses directly related to leaves
    Costa, M. - \ 2002
    FlowerTECH 5 (2002)3. - ISSN 1388-8439 - p. 16 - 17.
    rosa - snijbloemen - hergroei - wortels - bladoppervlakte - fotosynthese - rosa - cut flowers - regrowth - roots - leaf area - photosynthesis
    Experimenten met Rosa hybrida Madelon, om het verband tussen resterend bladoppervlak na de oogst van de roos en de hergroei van de wortels te vinden
    Manipulating the physiological quality of in vitro plantlets and transplants of potato
    Mehari, T. - \ 2000
    Agricultural University. Promotor(en): P.C. Struik; W.J.M. Lommen. - S.l. : S.n. - ISBN 9789058083302 - 230
    solanum tuberosum - aardappelen - in vitro kweek - microvermeerdering - zaadproductie - transplantaten - groei - groeianalyse - bladoppervlakte-index - bladoppervlakte - lichtpenetratie - ophoping van drogestof - stikstof - temperatuur - acclimatisatie - solanum tuberosum - potatoes - in vitro culture - micropropagation - seed production - transplants - growth - growth analysis - leaf area index - leaf area - light penetration - dry matter accumulation - nitrogen - temperature - acclimatization

    In vitro techniques have been introduced in potato seed production systems in recent years. This research project aimed at studying the morphological and physiological changes in plants and crops in the last three phases of a seed production system that included an in vitro multiplication, an in vitro normalisation (growing cuttings to rooted plantlets), a transplant production, and a tuber production (field) phase.

    Leaf area was identified as an important plant parameter for plant growth in the normalisation and transplant production phases. Explants and plantlets with larger initial leaf area performed better than those with smaller initial leaf area. In vitro treatments mainly affected leaf area of transplants through their effects on early above-ground leaf area. Leaf area increase was better described by logistic than by exponential or expolinear curves in all phases of growth, suggesting restriction of leaf area increase in all phases.

    Low temperature decreased leaf and stem dry weights in all phases, and increased tuber fresh and dry yields, average tuber weight, leaf/stem ratio, specific leaf area and harvest index in the tuber production phase. Growing in vitro plants at low normalisation temperatures increased leaf and total plant dry weights early in the transplant production and tuber production phases. It resulted in higher tuber yields, heavier individual tubers and higher harvest index.

    Fertilising plants with higher nitrogen (40 versus 10 mg N per plant) during transplant production resulted in plants with higher groundcover in the field. This led to higher interception of solar radiation and higher tuber yield in one of the two experiments. Growing plants at higher temperature (26/20 versus 12/18 °C) during transplant production increased leaf area at the end of the transplant production phase. After transplanting to the field, it resulted in crops with higher groundcover, which intercepted more incoming solar radiation. Yield tended to be higher, but differences could not be assessed as statistically significant. A glasshouse experiment showed that high temperature during transplant production increased leaf and stem dry weights in the tuber production phase, but reduced tuber dry weights and harvest index when temperatures during tuber production were high. Thus, high temperature during transplant production may favour haulm growth and light interception in the field, but may also reduce dry matter partitioning to tubers.

    Conditions in the tuber production phase were found to be of greater importance for final yield than conditions and treatments in earlier phases.

    Strategies to optimise the production and use of propagules and transplants should focus on achieving leafy starting material, reducing stress during changes in environment and optimising conditions during tuber production. Production of transplants should be adjusted to the expected growth conditions in the tuber production phase.

    Key words:Solanum tuberosum L., in vitro plantlet, seed production, normalisation, transplant production, tuber production, acclimatisation, leaf area, groundcover, logistic growth, temperature, nitrogen, dry matter production, specific leaf area, harvest index, radiation interception, radiation use efficiency.

    Plant morphology, environment, and leaf area growth in wheat and maize
    Bos, H.J. - \ 1999
    Agricultural University. Promotor(en): P.C. Struik; J. Vos. - S.l. : Bos - ISBN 9789058080035 - 149
    tarwe - maïs - plantenmorfologie - bladoppervlakte - temperatuur - lichtrelaties - plantdichtheid - groeimodellen - wheat - maize - plant morphology - leaf area - temperature - light relations - plant density - growth models
    Leaf area expansion of wheat (Triticum aestivum L.) and maize (Zea mays L.) plants, as contrasting representatives of the Gramineae family, was analysed. Seven variables were identified that together completely determine leaf area expansion of the plant: leaf appearance rate per tiller, specific site usage (fraction of buds that ultimately develop into a visible tiller at a specific site), Haun Stagedelay (indicating the timing of tiller appearance relative to the parent tiller), leaf elongation rate, leaf elongation duration, maximum leaf width and a leaf shape variable.

    Experiments with spaced plants in growth chambers yielded equations in which the effects of leaf and tiller position, temperature and photosynthetic photon flux density (PPFD) were quantified for each leaf area variable. In non-tillering species maize, leaf appearance rate and leaf elongation rate were higher, and leaf elongation duration was shorter at higher temperatures. At higher PPFD values, leaf appearance rate and maximum leaf width were higher and leaf elongation rate was lower. In wheat, the effects of temperature and PPFD were qualitatively equal to those in maize, except that there was no effect of PPFD on maximum leaf width. In the tillering species wheat, specific site usage was higher at lower temperatures and higher PPI'D values. Equations were developed for the effects of leaf position on leaf elongation rate and maximum leaf width.

    This knowledge was used in the analysis of effects of plant density in growth chamber and field experiments. Plant density mainly affected leaf appearance rate in maize and specific site usage in wheat. For both species, the effects of plant density on these variables seemed well related to local assimilate availability.

    Based upon the morphological framework presented, a simulation model was developed for wheat using the principles of object orientation. Plant related processes were strictly simulated at organ level. The simulation results showed clear differences in leaf area expansion for leaves at different positions in the plant.

    The morphological framework can be used for experimental analysis of leaf area growth, revealing mechanisms regulating leaf area growth of plants. The simulation model is flexible and can be easily extended for different environmental conditions and plant species.
    De toepasbaarheid van lichttransmissie - metingen onder boomkronen bij het vaststellen van de vitaliteit van bomen : een orienterend onderzoek
    Roest, P.B. van der; Kopinga, J. - \ 1989
    Wageningen : De Dorschkamp (Rapport / "De Dorschkamp" Instituut voor Bosbouw en Groenbeheer nr. 561) - 39
    bosbouw - bomen - gezondheid - meting - instrumenten (meters) - gereedschappen - merken - dendrometers - schuifmaten - relascopen - bladoppervlakte - forestry - trees - health - measurement - instruments - tools - marking - dendrometers - callipers - relascopes - leaf area
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