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Document Server@UHasselt (59.068 recursos)

Repository of the University of Hasselt containing publications in the fields of statistics, computer science, information strategies and material from the Institute for behavioural sciences.

Dept. Chemistry-Biology-Geology (SBG) - Laboratory of Botany

Mostrando recursos 1 - 20 de 121

  1. De fotosynthese anders bekeken

    Guedens, Wanda; Reygel, Patrick; Asperges, Michel
    Fotosynthese-experimenten in het secundair onderwijs bleven tot nog toe beperkt tot het afdekken van Pelargoniumbladeren met aluminiumfolie en het ‘bellenexperiment’ met waterpest (Elodea canadensis)1. Het practicum ‘Microscopische waarnemingen van de fotosynthese’ laat echter toe de vorming van zuurstofgas en zetmeel op microscopische schaal te zien en bovendien wordt de kennis over (bio)chemie en biologie hierbij op een zeer hoog niveau van integreren gebracht.

  2. Real time qPCR expression analysis of some stress related genes in leaf tissue of Pyrus communis cv. Conf??rence after infection with Erwinia amylovora

    Vrancken, K.; Schoofs, H.; Deckers, T.; Valcke, R.
    Hydrogen peroxide plays a critical role in the expression of disease resistance in several plant/pathogen interactions. It serves as a substrate for oxidative crosslinking of various plant cell wall components leading to the reinforcement of the cell structure, as a direct toxin against the pathogen and as a signal molecule for the induction of defence-related genes in the adjacent, still healthy tissues. In plant cells, enzymes and redox metabolites act in synergy to carry out the detoxification of hydrogen peroxide and other reactive oxygen species (ROS). Superoxide dismutase (SOD) catalyses the dismutation of superoxide to hydrogen peroxide, catalase (CAT) dismutates hydrogen peroxide to oxygen and water, and ascorbate peroxidase (APX) reduces hydrogen peroxide...

  3. Evaluation of the photosynthetic activity in transgenic tobacco plants with altered endogenous cytokinin content: lessons from cytokinin

    Cortleven, Anne; Valcke, Roland
    Cytokinin is known to be involved in many processes related to plastid development and function but the exact role of cytokinin in photosynthesis remains elusive. To investigate more profoundly the effects of cytokinin in this process, the photosynthetic activity of transgenic Pssu-ipt and 35S:CKX1 tobacco (Nicotiana tabacum) plants with respectively elevated and reduced endogenous cytokinin content was evaluated. Pigment analysis indicated that elevated endogenous cytokinin content resulted in increased pigment content. Functional analysis of the photosynthetic apparatus by chlorophyll a fluorescence and in vitro electron transport measurements clearly showed that changing the endogenous cytokinin content affects the activity of the photosynthetic apparatus. Surprisingly, both an increase as well as a decrease...

  4. Vakdidactiek: Seminarie practica en demonstraties biologie en natuurwetenschappen

    Reygel, Patrick; Asperges, Michel; Guedens, Wanda
    Deze bijdrage bevat materiaal voor de organisatie van een uitgebreid seminarie in het domein van de vakdidactiek van de Biologie/Natuurwetenschappen. De beschreven workshop en alle experimenten werden in de loop van meerdere jaren getest en gebruikt in een academische lerarenopleiding in het kader van het opleidingsonderdeel Vakdidactiek Biologie/Chemie aan de UHasselt. Het seminarie of een selectie ervan kan ook gebruikt worden in professionele bacheloropleidingen en mits tekstaanpassingen in het Secundair Onderwijs en dit zowel binnen het meeruren pakket Biologie als Natuurwetenschappen.

  5. Onderwijsmethoden en methodische werkvormen geschikt voor lessen biologie en natuurwetenschappen

    Asperges, Michel; Guedens, Wanda; Reygel, Patrick
    Vakdidactiek en -methodiek zijn bij vakleerkrachten niet erg in trek. Het is zelfs moeilijk om recente vakliteratuur voor Vlaanderen over dit onderwerp te vinden. Rond het jaar 1974 startten, op aandringen van Rijksinspectrice Dr. M. De Ridder en zuster Dr. M. Van Dijck, enkele docenten uit het toenmalige regentaat biologie netoverstijgende vergaderingen rond een mogelijke cursus didactiek en methodologie biologie. Dit zou in 1979 resulteren in een handboek. Vooral Deconinck W. (Asperges M. e.a., 1979) werkte inspirerend. Biologie als schoolvak zou van een louter kennisvak - gericht op het kunnen reproduceren van weetjes - veranderen in een wetenschappelijk verantwoord vak...

  6. De fotosynthese anders bekeken

    Guedens, Wanda; Reygel, Patrick; Asperges, Michel
    Fotosynthese-experimenten in het secundair onderwijs bleven tot nog toe beperkt tot het afdekken van pelargoniumbladeren met aluminiumfolie en het ‘bellenexperiment’ met waterpest (Elodea canadensis). Het practicum microscopische waarnemingen van de fotosynthese laat echter toe de vorming van zuurstofgas en zetmeel op microscopische schaal te zien en bovendien wordt de kennis over (bio)chemie en biologie hierbij op een zeer hoog niveau van integreren gebracht.

  7. Analysis of the photosynthetic apparatus in transgenic tobacco plants with altered endogenous cytokinin content: a proteomic study

    Cortleven, Anne; NOBEN, Jean-Paul; VALCKE, Roland
    Background: Cytokinin is a plant hormone that plays a crucial role in several processes of plant growth and development. In recent years, major breakthroughs have been achieved in the elucidation of the metabolism, the signal perception and transduction, as well as the biological functions of cytokinin. An important activity of cytokinin is the involvement in chloroplast development and function. Although this biological function has already been known for 50 years, the exact mechanisms remain elusive. Results: To elucidate the effects of altered endogenous cytokinin content on the structure and function of the chloroplasts, chloroplast subfractions (stroma and thylakoids) from transgenic...

  8. How much do resin-based dental materials release? A meta-analytical approach

    Van Landuyt, K. L.; NAWROT, Tim; Geebelen, B.; De Munck, J.; Snauwaert, J.; Yoshihara, K.; Scheers, Hans; Godderis, Lode; Hoet, P.; Van Meerbeek, B.
    Objectives. Resin-based dental materials are not inert in the oral environment, and may release components, initially due to incomplete polymerization, and later due to degradation. Since there are concerns regarding potential toxicity, more precise knowledge of the actual quantity of released eluates is necessary. However, due to a great variety in analytical methodology employed in different studies and in the presentation of the results, it is still unclear to which quantities of components a patient may be exposed. The objective of this meta-analytical study was to review the literature on the short-and long-term release of components from resin-based dental materials,...

  9. Can bacteria associated with willow explain differences in Cd-accumulation capacity between different cultivars?

    WEYENS, Nele; SCHELLINGEN, Kerim; DUPAE, Joke; CROES, Sarah; VAN DER LELIE, Daniel; VANGRONSVELD, Jaco
    Phyoremediation has been proposed as an economically interesting alternative for remediation of metal contaminated soils. It can be applied on extended and diffusely contaminated areas and targets the "bioavailable" fraction of metals, which is the most relevant fraction from an environmental risk assessment perspective. The most important drawback is the long time period required for remediation process. Main limiting factors for an efficient phytoextraction are plant availability of metals, metal uptake and phytotoxicity. These constraints can be conquered by (1) choosing plant cultivars with both high metal uptake capacity and high biomass production; by (2) increasing metal availability and uptake...

  10. Dalytyphloplanida (Platyhelminthes: Rhabdocoela) from Andalusia, Spain, with the description of four new species

    VAN STEENKISTE, Niels; TESSENS, Bart; KRZNARIC, Kathleen; ARTOIS, Tom
    Nineteen taxa of Dalytyphloplanida Willems et al., 2006 collected from southwestern Andalusia are discussed. Although most taxa were found in freshwater, three are marine, one occurred in brackish water and Protoplanella simplex Reisinger, 1924 was even collected in a dry, limnoterrestrial habitat. Four taxa are new to science. Castrada purgatorialis n. sp., Castrada paradisea n. sp. and Strongylostoma devleeschouweri n. sp., all belong to the Typhloplanidae Graff, 1905. The first two species differ from other species of Castrada Schmidt, 1861 by the presence of a large accessory bursa and the morphology of the copulatory atrium. C. purgatorialis n. sp. has...

  11. Lead toxicity to wildlife: Derivation of a critical blood concentration for wildlife monitoring based on literature data

    Buekers, J.; STEEN REDEKER, Erik; Smolders, E.
    Generic risk assessments of lead (Pb) toxicity to wildlife puts soil Pb limits below the natural background. The Tissue Residue Approach (TRA) is an alternative method by which the current risk of Pb to wildlife can be assessed and avoids uncertainties about Pb exposure routes or bioavailability of environmental Pb. About 80 toxicity studies were reviewed of which 19 experimental and 6 field studies with mammals and birds were selected. Blood lead concentration (Pb-B, mu g Pb/dL) was used as the index of exposure. The highest No Observed Effect Concentrations (NOECs) varied about 1600-fold among species and tests when expressed...

  12. Cytokinins affect the structure and function of the photosynthetic apparatus: a multidisciplinary approach

    CORTLEVEN, Anne

  13. Selection of plastid- and nuclear-encoded reference genes to study the effect of altered endogenous cytokinin content on photosynthesis genes in Nicotiana tabacum

    CORTLEVEN, Anne; REMANS, Tony; Brenner, Wolfram G.; VALCKE, Roland
    Selection and use of appropriate reference genes as internal controls in real-time reverse transcription PCR (RT-PCR) assays is highly important for accurate quantification of gene expression levels. Since some photosynthetic genes are encoded in the nuclear genome and others in the chloroplast genome, we evaluated both nuclear- and plastid-encoded candidate reference genes. Six plastid-encoded candidate reference genes were derived from Arabidopsis microarray data and three plastid-and five nuclear-encoded reference genes were derived from literature. Cytokinins influence photosynthetic gene expression, so we evaluated the expression stability of the candidate reference genes in transgenic Nicotiana tabacum plants with elevated or diminished cytokinin...

  14. Comparative proteome analysis of four Erwinia amylovora strains with different pathogenicity

    THOELEN, Mieke; NOBEN, Jean-Paul; ROBBEN, Johan; VALCKE, Roland; Deckers, T.
    Fire blight, caused by the bacterium Erwinia amylovora, affects most species of the Malaceae and some species in other families of the Rosales. The severity of the disease results from its destructive character on the one hand and the lack of effective control methods on the other hand. To gain a better insight into the degree of virulence and the sensitivity to oxidative stress, the proteome of four strains of Erwinia amylovora was studied. The strains used were E. amylovora LMG2024 and PD437, which are moderately pathogenic, PFB5, which is highly, and BG16, which is very highly pathogenic. The bacteria...

  15. Comparative proteome analysis from Erwinia amylovora grown in vitro and in planta

    THOELEN, Mieke; NOBEN, Jean-Paul; ROBBEN, Johan; VALCKE, Roland; Deckers, T.
    Fire blight, caused by the bacterium Erwinia amylovora, affects most species of the Malaceae and some species in other families of the Rosales. The severity of the disease results from its destructive character on the one hand and the lack of effective control methods on the other hand. To gain a better insight into the infection process and proteins involved, the proteome of bacteria grown in vitro and in planta (M9 kloon 29, apple rootstocks) was studied. After two-dimensional electrophoresis, differentially regulated protein spots were excised, trypsinized and analysed by LC-ESI-MS/MS. A total of 127 differentially expressed proteins were identified...

  16. Prediction of Physiological Disorders in Pears Using Non-Invasive Fluorescence Techniques

    VALCKE, Roland
    The determination of the physiological state of fruits using non-invasive techniques is very much in progress. Parameters which meet consumer expectations such as sugar content, acidity, flesh firmness, internal quality, etc., are traditionally determined with destructive techniques on a fruit sample which is conventionally considered representative of all the harvested fruit. Currently, non-destructive evaluation methods using near-infrared spectroscopy (NIRs), X-ray, acoustic methods and electronic noses are being tested on several fruit and vegetables, with the aim of identifying parameters which could estimate maturity more properly. A major challenge in fruit evaluation is the ability to detect physiological disorders, induced by...

  17. The Use of Gibberellins and Prohexadione-Ca Treatments for Fruit Set improvement on 'Conference' Pear

    Vanthournout, Sofie; Valcke, Roland; Deckers, T.
    Since the growth regulator chlormequat chloride (CCC) was removed from the market in Belgium in 1998, pear growing in intensive training systems has become more difficult and fruit growers are looking for alternative ways to control the vegetative growth of the pear trees. Prohexadione-Ca, a new growth regulator with good reported results oil apple trees, is much less effective on pear trees and call have a negative effect on return bloom. The best way to control the vegetative vigour of a fruit tree is to induce regularity in its productivity, which can be achieved by a treatment with gibberellins, but...

  18. Study of transgenic tobacco plants containing the ipt-gene under control of a tetracycline-inducible promoter

    QUANTEN, Lieve

  19. Cadmium responses in Arabidopsis thaliana: a study focusing on Subcellular localization

    Van Belleghem, Frank
    Cadmium (Cd), which is known to be very toxic to plants, animals and humans, is a relatively rare element. However, since the 19th century, industrial activities have contaminated extensive areas with cadmium, which presents a considerable environmental threat. Also in Belgium there are several locations with Cd contamination. For instance, in the north east of Belgium, an area as large as 280 km2 has become contaminated with Zn, Cd and Pb, because of the historic presence of several zinc smelters. Cross-sectional population studies in that area have demonstrated a positive correlation between the high Cd concentrations in various crops and...

  20. Development of a chlorophyll fluorescence imaging system for the quality assessment of fruits and vegetables

    CISCATO, Massimo

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