Research Center for Ornamental Plants

Destelbergen, Belgium

Research Center for Ornamental Plants

Destelbergen, Belgium
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Christiaens A.,Ghent University | Christiaens A.,Research Center for Ornamental Plants | Dhooghe E.,Ghent University | Dhooghe E.,Belgium Institute for Agricultural and Fisheries Research | And 3 more authors.
Scientia Horticulturae | Year: 2012

The increased horticultural interest in Helleborus requires the development of techniques for flowering control. Therefore, we have determined flower initiation and differentiation under natural conditions for Helleborus niger L. and the hybrid Helleborus x ericsmithii B. Mathew. Once flower primordia were present in the underground buds of the plants, the effect of a cold treatment (336, 504 or 672 chilling units (CU)) and a supplemental gibberellic acid (GA 3) application (500mgL -1) on pre-cooled plants was examined. The cold treatment resulted in a progressive decrease of the time to flower. Moreover, when pre-cooled plants received a supplemental GA 3 application early flowering was further enhanced and these plants had a higher number of flowers with longer flower stems and larger flowers. © 2012 Elsevier B.V.

Bangels E.,PCFRUIT | Peusens G.,PCFRUIT | Belien T.,PCFRUIT | Gobin B.,Research Center for Ornamental Plants
Acta Horticulturae | Year: 2011

Pome fruit growers around the world are gradually adopting Integrated Fruit Production (IFP). IFP is defined by the IOBC as the economical production of high quality fruit, giving priority to ecologically safer methods, minimising the undesirable side effects and use of agrochemicals, to enhance the safeguards to the environment and human health. Integrated Pest Management (IPM) is central to IFP and strongly depends on the availability of selective insecticides. Spirotetramat (brand name Movento®) is a very promising active ingredient belonging to the class of tetramic acid derivatives. It has a two-way systemic action, allowing it to move downwards as well as upwards within the plant in the phloem and in the xylem vessels. From 2002 onwards, numerous GEP and non-GEP field trials with this new compound were performed by pcfruit in apple and pear orchards in Belgium. Trials were all executed according to EPPO guidelines. Based on the outcomes of these trials, spirotetramat was proven to be efficient against a broad range of pests. In addition, spirotetramat was shown to have a good safety profile with respect to a range of beneficial arthropods (e.g., Typhlodromus pyri and Anthocoris sp.). Since the withdrawal of a number of plant protection products and limited use of certain broad-spectrum products according to the IFP-guidelines, the control of pest species such as pear sucker (Cacopsylla pyri) and woolly apple aphid (Eriosoma lanigerum) is very complicated at this time. Hence, the introduction of spirotetramat, with good efficacy against several severe pome fruit pests and good beneficial safety, will appreciably strengthen the currently applied IPM control strategies in IFP.

van Laere K.,Belgium Institute for Agricultural and Fisheries Research | Franca S.C.,Ghent University | Vansteenkiste H.,Research Center for Ornamental Plants | van Huylenbroeck J.,Belgium Institute for Agricultural and Fisheries Research | And 3 more authors.
Acta Physiologiae Plantarum | Year: 2011

In this study, we analysed morphological, anatomical and physiological effects of polyploidisation in Spathiphyllumwallisii in order to evaluate possible interesting advantages of polyploids for ornamental breeding. Stomatal density was negatively correlated with increased ploidy level. Stomatal size increased in polyploids. Tetraploid Spathiphyllum plants had more ovate and thicker leaves. The inflorescence of tetraploids had a more ovate and thicker spathum, a more cylindrical spadix and a thicker but shorter flower stalk. Biomass production of the tetraploids was reduced, as expressed by lower total dry weights, and tetraploids produced fewer shoots and leaves compared with their diploid progenitors. Furthermore, tetraploid Spathiphyllum plants were more resistant to drought stress compared with diploid plants. After 15 days of drought stress, diploids showed symptoms of wilting, while the tetraploids showed almost no symptoms. Further, measurements of stomatal resistance, leaf water potential, relative water content and proline content indicated that the tetraploid genotypes were more resistant to drought stress compared with the diploids. © 2010 Franciszek Górski Institute of Plant Physiology, Polish Academy of Sciences, Kraków.

Pollet B.,Ghent University | Kromwijk A.,Wageningen UR Greenhouse Horticulture | Vanhaecke L.,Ghent University | Dambre P.,Research Center for Ornamental Plants | And 3 more authors.
Annals of Applied Biology | Year: 2011

Knowledge of the energy saving night temperature (i.e. a relatively cool night temperature without affecting photosynthetic activity and physiology) and a better understanding of low night temperature effects on the photosynthetic physiology of Phalaenopsis would improve their production in terms of greenhouse temperature control and energy use. Therefore, Phalaenopsis'Hercules' was subjected to day temperatures of 27.5°C and night temperatures of 27.0°C, 24.2°C, 21.2°C, 18.3°C, 15.3°C or 12.3°C in a growth chamber. A new tool for the determination of the energy saving night temperature range was developed based on temperature response curves of leaf net CO2 exchange, chlorophyll fluorescence, organic acid content and carbohydrate concentrations. The newly developed method was validated during a complete vegetative cultivation in a greenhouse environment with eight Phalaenopsis hybrids (i.e. 'Boston', 'Bristol', 'Chalk Dust', 'Fire Fly', 'Lennestadt', 'Liverpool', 'Precious', 'Vivaldi') and day/night temperature set points of 28/28°C, 29/23°C and 29/17°C. Temperature response curves revealed an overall energy saving night temperature range for nocturnal CO 2 uptake, carbohydrate metabolism, organic acid accumulation and photosystem II (PSII) photochemistry of 17.1°C to 19.9°C for Phalaenopsis'Hercules'. At the lower end of this energy saving night temperature range, a high malate-to-citrate ratio switched towards a low ratio and this transition seemed to alleviate effects of night chilling induced photoinhibition. At night temperatures of 24°C or higher, the degradation of starch, glucose and fructose indicated an increased respiratory CO2 production. During the greenhouse validation experiment, the differences between the eight Phalaenopsis hybrids with regard to their response to the warm day/cool night temperature regimes were remarkably large. In general, the day/night temperature of 29/17°C led to a significantly lower biomass accumulation and less leaves which were in addition shorter, narrower and smaller in size as compared to the day/night temperature regimes of 28/28°C and 29/23°C. During week 25 of the cultivation period, plants matured and flower initiation steeply increased for all hybrids and in each day/night temperature regime. Before week 25, early spiking was only sufficiently suppressed in the 29/23°C and 29/17°C temperature regimes for three hybrids ('Boston', 'Bristol' and 'Lennestadt') but not in the other five hybrids. Although a considerable biochemical flexibility was demonstrated for Phalaenopsis'Hercules', inhibition of flowering after exposure to a combination of warm days and cool nights appeared to be largely hybrid dependent. © 2011 Association of Applied Biologists.

Pollet B.,Ghent University | Steppe K.,Ghent University | Dambre P.,Research Center for Ornamental Plants | Van Labeke M.-C.,Ghent University | Lemeur R.,Ghent University
Photosynthetica | Year: 2010

Nowadays, a quest for efficient greenhouse heating strategies, and their related effects on the plant's performance, exists. In this study, the effects of a combination of warm days and cool nights in autumn and spring on the photosynthetic activity and efficiency of Phalaenopsis were evaluated; the latter, being poorly characterised in plants with crassulacean acid metabolism (CAM) and, to our knowledge, not reported before in Phalaenopsis. 24-h CO2 flux measurements and chlorophyll (Chl) fluorescence analyses were performed in both seasons on Phalaenopsis 'Hercules' exposed to relatively constant temperature regimes, 25.5/24.0°C (autumn) and 30/27°C (spring) respectively, and distinctive warm day/cool night temperature regimes, 27/20°C (autumn) and 36/24°C (spring), respectively. Cumulated leaf net CO2 uptake of the distinctive warm day/cool night temperature regimes declined with 10-16% as compared to the more constant temperature regimes, while the efficiency of carbon fixation revealed no substantial differences in both seasons. Nevertheless, a distinctive warm day/cool night temperature regime seemed to induce photorespiration. Although photorespiration is expected not to occur in CAM, the suppression of the leaf net CO2 exchange during Phase II and Phase IV as well as the slightly lower efficiency of carbon fixation for the distinctive warm day/cool night temperature regimes confirms the involvement of photorespiration in CAM. A seasonal effect was reflected in the leaf net CO2 exchange rate with considerably higher rates in spring. In addition, sufficiently high levels of photosynthetically active radiation (PAR) in spring led to an efficiency of carbon fixation of 1. 06-1. 27% which is about twice as high than in autumn. As a result, only in the case where a net energy reduction between the temperature regimes compensates for the reduction in net CO2 uptake, warm day/cool night temperature regimes may be recommended as a practical sustainable alternative. © 2010 Springer Science+Business Media B.V.

Pollet B.,Ghent University | Vanhaecke L.,Ghent University | Dambre P.,Research Center for Ornamental Plants | Lootens P.,Belgium Institute for Agricultural and Fisheries Research | Steppe K.,Ghent University
Plant Cell Reports | Year: 2011

The capability of Phalaenopsis to acclimate its photosynthetic capacity and metabolic activity to cool night temperature conditions is crucial for improving orchid production in terms of efficient greenhouse heating. The extent to which Phalaenopsis possesses acclimation potential and the mechanistic background of the metabolic processes involved, have, however, not been studied before. Plants were subjected to a direct and gradual shift from a day to night temperature regime of 28/28-28/16°C, the cold stress and cold acclimation treatment, respectively. In comparison with the cold stress treatment, the cold acclimation treatment led to a higher malate accumulation and a reduction in leaf net CO2 uptake. Consistently, the contribution of respiratory CO2 recycling to nocturnal malate synthesis was calculated to be 23.5 and 47.0% for the cold stress and cold acclimation treatment, respectively. Moreover, the lower levels of starch measured in the cold acclimated leaves confirmed the suggested enhanced respiratory CO2 recycling, implying that Phalaenopsis CAM operation evolved towards CAM idling. It is, however, plausible that this adjustment was not an effect of the low night temperature per se but a consequence of cool-root induced drought stress. Apart from that, at the start of the photoperiod, membrane stability showed a depression which was directly counteracted by an increased generation of glucose, fructose and sucrose. From these observations, it can be concluded that the observed plasticity in CAM operation and metabolic flexibility may be recognized as important steps in the low night temperature acclimation of Phalaenopsis. © 2011 Springer-Verlag.

Van Labeke M.-C.,Ghent University | Volckaert E.,Research Center for Ornamental Plants
Acta Horticulturae | Year: 2010

Dormant and cold acclimated forest seedlings have a higher stress tolerance after lifting and support longer storage periods without loss of plant vitality and vigour. As dormancy is induced by photoperiod cold acclimatization needs lower temperatures. Cold acclimatization in temperate woody plants is linked to metabolic changes such as an increase of soluble sugars - especially of the oligosaccharides raffinose and stachyose - in bark tissue and in buds. Yet this is a laborious technique for routine analysis of cold acclimatization. Therefore the possibility of electrolyte leakage (EL) to detect cold acclimatization was investigated for six deciduous tree species namely Acer pseudoplatanus, Crataegus monogyna, Fraxinus excelsior, Prunus avium, Quercus rubra and Tilia cordata. As a measure of cold acclimatization or frost hardiness, bud damage following controlled freezing to -18°C and -25°C respectively was assessed. The EL- 18°C and EL- 25°C were correlated with raffinose and stachyose concentrations in the buds. Good correlations were only found for three species. The potential of measuring cold acclimatization by electrolyte leakage is species dependant.

Lommelen E.,Zoological Institute | Wenseleers T.,Zoological Institute | Johnson C.A.,The American Museum of Natural History | Drijfhout F.P.,Keele University | And 2 more authors.
Journal of Insect Behavior | Year: 2010

Approximately 150 ant species are facultatively or obligately queenless whereby mated workers assume the role of the queen. In many of these species a reproductive dominance hierarchy is established by way of aggressive interactions. Top-ranking workers, which are typically the most fecund, acquire a characteristic cuticular hydrocarbon profile. We studied the temporal dynamics of this chemical change and associated interplay with observed aggressive interactions in an experimentally orphaned colony of the facultatively queenless ant Gnamptogenys striatula. Our observations and chemical analyses demonstrate that chemical fertility signals played a major role in the establishment of a dominance hierarchy and aggression settled dominance relationships only when ants had identical hydrocarbon profiles. Moreover, individuals with a higher potential fertility, in this experiment reflected in a higher ovariole number, are shown to have a better chance of becoming a reproductive. © 2010 Springer Science+Business Media, LLC.

Heylen K.,Catholic University of Leuven | Gobin B.,Fruitteenweg | Gobin B.,Research Center for Ornamental Plants | Arckens L.,Catholic University of Leuven | And 2 more authors.
Apidologie | Year: 2011

This study describes the impact of sublethal doses of 4 pesticides on size and morphology of the honeybee worker's hypopharyngeal glands. This gland plays an essential role in brood care by young workers, and thus colony growth. Contaminating 7 day old caged bees, we sampled after 1 day and 1 week for Captan-, Imidacloprid- and Indoxacarb-treated bees and after 1, 2, 3, 4, 5 and 7 days for Fenoxycarb-treated bees. The glands' acini 1 week post-treatment were all significantly smaller in treated bees. However, lightand electron microscopy showed hardly any difference between controls and gland cells, treated with Captan, Imidacloprid or Indoxacarb. Yet upon Fenoxycarb-treatment, acini showed a decrease in size, a granular texture and unorganized cytoplasm more quickly than normal. Indeed, after only 7 days, Fenoxycarb-treated glands displayed features typical of the onset of foraging in older bees. © INRA/DIB-AGIB/EDP Sciences, 2010.

Schamp B.,Research Center for Ornamental Plants | Pauwels E.,Research Center for Ornamental Plants | Gobin B.,Research Center for Ornamental Plants
Acta Horticulturae | Year: 2012

Recent developments show that Light Emitting Diodes (LED) can most likely not replace High Pressure Sodium (HPS) lights for full production cycles. However, the typical discrete spectral properties of LEDs make them highly suitable for (1) steering plant or flower development at specific growth stages and (2) providing optimal light at close distances to the plant, e.g., in multi-layered systems. We explored this potential to steer flowering induction in the Ghent azalea (Rhodondendron simsii). We developed an optimal light recipe for multi-layered forcing. Rhododendron simsii cultivation necessitates a forcing period in order to obtain intense flower colors and uniform flowering. Forcing requires three weeks 21°C, 70-80% RH and 91 μmol m-2 s-1 light intensity. This means extreme high energy input in winter. HPS lights have a high degree of heat radiation preventing their use in multi-layered systems. Since LEDs seems suitable, to determine the optimal wavelength composition and intensities we compared four LED-units equipped with different amounts of Red, Far-Red and Blue light with conventional HPS lamps and a control. Except for the control, none of the lighting treatments received external sunlight to mimic multi-layered conditions. The experiment was repeated eight times. Measurements indicated increased flower size under additional lighting. All three wavelengths are necessary for optimal flower quality, although red light is of far greater importance then blue light. Light intensities of 91 μmol m-2 s-1 with LED give comparable or even better results than HPS. With LED, the necessary lighting period can be reduced compared to HPS lights. Our results show potential for the use of LED in multi-layered systems for the forcing of azalea, with potential to reduce energy cost remarkably. © ISHS 2012.

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