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.

    We have a manual that explains all the features 

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    Carbon dioxide fertilization offsets negative impacts of climate change on Arabica coffee yield in Brazil
    Verhage, Fabian - \ 2017
    Arabica coffee yield simulation model - productivity - elevated CO2 concentration - carbon dioxide fertilization - climate change impact assessment - global warming - irrigation
    This collection unites the most important files used to assess the impact of climate change on Arabica coffee in Brazil under a RCP4.5 scenario by 2040-2070, as described by Verhage, Anten & Sentelhas (2017). These files are provided to encourage the further verification, development and application of the Arabica coffee yield simulation model. In addition, the collection includes a short description and try-out of the agro-ecological zoning model, developed by Doorenbos & Kassam (1979) for the Food and Agriculture Organization (FAO), applied on Arabica coffee. This model was excluded from the final study, but the work might still be of use to other researchers.
    Animal and run variation for rumen degradation determined with the in situ method
    Lacombe, S. ; Dijkstra, J. ; Jacobs, M. ; Doorenbos, J. ; Laar, H. van - \ 2017
    - p. 396 - 396.
    Effect of different levels of rapidly degradable carbohydrates calculated by a simple rumen model on performance of lactating dairy cows
    Doorenbos, J. ; Martín-Tereso, J. ; Dijkstra, J. ; Laar, H. van - \ 2017
    Journal of Dairy Science 100 (2017)7. - ISSN 0022-0302 - p. 5422 - 5433.
    Dairy cow - Milk production - Rapidly degradable carbohydrate - Rumen model

    Aggregating rumen degradation characteristics of different carbohydrate components into the term modeled rapidly degradable carbohydrates (mRDC) can simplify diet formulation by accounting for differences in rate and extent of carbohydrate degradation within and between feedstuffs. This study sought to evaluate responses of lactating dairy cows to diets formulated with increasing levels of mRDC, keeping the supply of other nutrients as constant as possible. The mRDC content of feedstuffs was calculated based on a simple rumen model including soluble, washable, and nonwashable but potentially degradable fractions, as well as the fractional degradation and passage rates, of sugar, starch, neutral detergent fiber, and other carbohydrates. The mRDC term effectively represents the total amount of carbohydrates degraded in the rumen within 2 h after ingestion. Fifty-two lactating Holstein cows (of which 4 were rumen fistulated) were assigned to 4 treatments in a 4 × 4 Latin square design. Treatments were fed as a total mixed ration consisting of 25.4% corn silage, 23.1% grass silage, 11.6% grass hay, and 39.9% concentrate on a dry matter basis. Differences in mRDC were created by exchanging nonforage neutral detergent fiber-rich ingredients (mainly sugar beet pulp) with starch-rich ingredients (mainly wheat) and by exchanging corn (slowly degradable starch) with wheat (rapidly degradable starch) in the concentrate, resulting in 4 treatments that varied in dietary mRDC level of 167, 181, 194, or 208 g/kg of dry matter. Level of mRDC did not affect dry matter intake. Fat- and protein-corrected milk production and milk fat and lactose yield were greatest at 181 mRDC and decreased with further increases in mRDC. Milk protein yield and concentration increased with increasing mRDC level. Mean rumen pH and diurnal variation in ruminal pH did not differ between treatments. Total daily meal time and number of visits per meal were smaller at 181 and 194 mRDC. Despite milk production responses, increasing dietary mRDC levels, while maintaining net energy and intestinal digestible protein as well as other nutrients at similar levels, did not influence rumen pH parameter estimates and had minor effects on feeding behavior. These results indicate that aggregating rapidly degradable carbohydrate content into one term may be a simple way to further improve predictability of production responses in practical diet formulation for lactating dairy cows.

    Effect of TMR differing in rapidly fermentable carbohydrate content on dry matter intake, milk yield, milk composition and rumen pH in Holstein Friesian dairy cows
    Laar, H. van; Bikker, J.P. ; Dijkstra, J. ; Martin-Tereso, J. ; Doorenbos, J. - \ 2014
    In: Proceedings of the 30th Biennial Conference of the Australian Society of Animal Production. - Australian Society of Animal Production - p. 82 - 82.
    Technical note: Evaluation of an ear-attached movement sensor to record cow feeding behavior and activity
    Bikker, J.P. ; Laar, H. van; Rump, P. ; Doorenbos, J. ; Meurs, K. van; Griffioen, G.M. ; Dijkstra, J. - \ 2014
    Journal of Dairy Science 97 (2014)5. - ISSN 0022-0302 - p. 2974 - 2979.
    dairy-cattle - monitoring rumination - automatic system - coefficient - agreement - ovulation - time
    The ability to monitor dairy cow feeding behavior and activity could improve dairy herd management. A 3-dimensional accelerometer (SensOor; Agis Automatisering BV, Harmelen, the Netherlands) has been developed that can be attached to ear identification tags. Based on the principle that behavior can be identified by ear movements, a proprietary model classifies sensor data as “ruminating,” “eating,” “resting,” or “active.” The objective of the study was to evaluate this sensor on accuracy and precision. First, a pilot evaluation of agreement between 2 independent observers, recording behavior from 3 cows for a period of approximately 9 h each, was performed. Second, to evaluate the sensor, the behavior of 15 cows was monitored both visually (VIS) and with the sensor (SENS), with approximately 20 h of registration per cow, evenly distributed over a 24-h period, excluding milking. Cows were chosen from groups of animals in different lactation stages and parities. Each minute of SENS and VIS data was classified into 1 of 9 categories (8 behaviors and 1 transition behavior) and summarized into 4 behavioral groups, namely ruminating, eating, resting, or active, which were analyzed by calculating kappa (¿) values. For the pilot evaluation, a high level of agreement between observers was obtained, with ¿ values of =0.96 for all behavioral categories, indicating that visual observation provides a good standard. For the second trial, relationships between SENS and VIS were studied by ¿ values on a minute basis and Pearson correlation and concordance correlation coefficient analysis on behavior expressed as percentage of total registration time. Times spent ruminating, eating, resting, and active were 42.6, 15.9, 31.6, and 9.9% (SENS) respectively, and 42.1, 13.0, 30.0, and 14.9% (VIS), respectively. Overall ¿ for the comparison of SENS and VIS was substantial (0.78), with ¿ values of 0.85, 0.77, 0.86, and 0.47 for “ruminating,” “eating,” “resting,” and “active,” respectively. Pearson correlation and concordance correlation coefficients between SENS and VIS for “ruminating,” “eating,” “resting,” and “active” were 0.93, 0.88, 0.98, and 0.73, and 0.93, 0.75, 0.97, and 0.35, respectively. In conclusion, the results provide strong evidence that the present ear sensor technology can be used to monitor ruminating and resting behavior of freestall-housed dairy cattle. Our results also suggest that this technology shows promise for monitoring eating behavior, whereas more work is needed to determine its suitability to monitor activity of dairy cattle.
    The effect of natural alternatives for anti-microbial growth promoters in broiler diets
    Hartog, L.A. den; Gutierrez del Alamo Oms, A. ; Doorenbos, J. ; Flores Minambres, A. - \ 2005
    In: Proceedings 15th European symposium on poultry nutrition, Balatonfüred, Hungary, 2005 Balatonfüred, Hungary : - p. 212 - 220.
    The application of the net energy system for swine
    Rijnen, M.M.J.A. ; Doorenbos, J. ; Mallo, J.J. ; Hartog, L.A. den - \ 2004
    - p. 1 - 16.
    The sections of Begonia including descriptions, keys and species lists (Studies in Begoniaceae VI).
    Doorenbos, J. ; Sosef, M.S.M. ; Wilde, J.J.F.E. de - \ 1998
    Wageningen : Wageningen Agricultural University (Wageningen Agricultural University papers 98-2) - ISBN 9789057820076 - 266
    begonia - begoniaceae - soorten - taxonomie - identificatie - determinatietabellen - sierplanten - bloemen - amerika - afrika - azië - begonia - begoniaceae - species - taxonomy - identification - keys - ornamental plants - flowers - america - africa - asia
    Digesta passage at the terminal ileum in pigs.
    Leeuwen, P. van; Doorenbos, J. ; McCracken, K.J. ; Ebbinge, J.B. ; Verstegen, M.W.A. - \ 1997
    In: Proc. VIIth Int. Symp. Digestive Physiology in Pigs, J.-P. Laplace et al. (eds.), Saint Malo, France. EAAP 88 - p. 530 - 534.
    Biosystematics of Begonia squamulosa Hook.f. and affiliated species in section Tetraphila A.DC.
    Arends, J.C. - \ 1992
    Agricultural University. Promotor(en): L.J.G. van der Maesen; J. Doorenbos, co-promotor(en): J.J.F.E. de Wilde. - S.l. : Arends - ISBN 9789067542111 - 223
    begoniaceae - planten - identificatie - embryologie - groei - plantenontwikkeling - afrika - begoniaceae - plants - identification - embryology - growth - plant development - africa

    This study deals with the systematics of plants belonging to a part of Begonia section Tetraphila that occur in tropical Africa. Six taxa are recognized and accorded the rank of species. The names of three of these taxa, viz.: B. elaeagnifolia Hook.f., B. longipetiolata Gilg and B. squamulosa Hook.f., have been published validly by their authors. Engler (1921) considered B. longipetiolata to be conspecific with B. squamulosa , but as the result of the present study the former name is reinstated. The other three taxa: B. karperi J.C. Arends, B. pelargoniiflora J.J. de Wilde & J.C. Arends and B. rwandensis J.C. Arends, are new species described for the first time. All six species treated here are delimited from the other 24 species in the section Tetraphila by the combination of features mentioned in Chapter 1.

    Many features have been studied in preserved field collections, while quite a few data have been obtained from observations of living plants of B. elaeagnifolia , B. karperi , B. longipetiolata and B. squamulosa , both in the wild and in the greenhouse.

    From the review of previous taxonomic treatments in Chapter 2 it appears that, in the past, vegetative features have been overemphasized in the recognition and the delimitation of the taxa dealt with here. In Chapters 4 to 8 the results of detailed morphological, anatomical and karyological studies are discussed and compared with data from previous investigations in Begonia.

    Both B. elaeagnifolia and B. squamulosa comprise diploid as well as tetraploid populations. The 4x populations, which are interpreted to be interracial autopolyploids, are confined to the Crystal Mts in Gabon (Chapter 4).

    As to vegetative structures (Chapter 5), stems and leaves usually show few specific differences. For example, both the stem and the leaf blade in B. rwanden sis are thicker than those in the superficially very similar B. karperi. Both species have peltate leaves with an actinodromous venation, while the leaf venation in the other species is simple craspedodromous. The ratio of the length of the largest leaf blade and the length of the longest internode of a specimen is, in combination with reproductive features, often indicative for the identity of that particular specimen. The dimension and the shape of the leaf blades are hardly useful for the delimitation of the species recognized here.

    The leaf margins are provided with tiny teeth which are both 'violoid' and 'tylate'. The apices of the teeth often include cells with suberized walls. Because of further suberization of tissue of both the teeth and adjacent parts of the blade, there may be regions of wound cork on the margin of older leaves. Complex hydathodes, which are associated with tracheids from vein terminations, are present on the upper surface of the leaf margin, including the teeth. The petioles of B. longipetiolata and B. pelargonifflora are usually canaliculate, whereas those of the remaining species are more or less terete. The indumentum of all the plants studied consists of short-stalked dentate scales, which according to their shape form an intergrading morphological series.

    Several reproductive features are discussed in Chapter 6. As far as the number of flowers and the comparative length of the axes in the cymoid inflorescences are concerned, the species are usually distinct. The vascular anatomy of female flowers shows that the outer perianth segments are homologous with sepals and the inner ones with petals. The stamens have poricidal anthers. The 'front side' of the zygomorphic androecium in a lateral flower is always oriented towards the main inflorescence axis. The anther pores of the stamens on the front side of the androecium of B. longipetiolata have an adaxial orientation in relation to the main inflorescence axis, but in B. squamulosa their orientation is abaxial.

    Although specific trends in both the number of stamens and the number of styles can be discerned, stamen number as well as style number are not constant specific characters. The anthers in B. pelargoniiflora and B. rwandensis are longer than those in the other species studied. Except for B. longipetiolata, whose style surface below the style arms and the stigmatic band is more or less papillose, that surface in the other species is smooth. In B. squamulosa the smooth style surface carries some dentate scales.

    The ovaries investigated show both an axial and a parietal placentation in a single ovary. In B. longipetiolata, each septum with its two placental lobes is cross-shaped in transverse section, while, as far as could be studied, that in the other species is T- or arrow-shaped. The ovules in B. squamulosa have a pleurotropous position in the ovarial cavities, whereas those in the other species are epitropous. The number of styles does not always correspond with the number of septa and/or locules in the same gynoecium.

    The placentae in the ovaries in B. elaeagnifolia , B. longipetiolata and B. squamulosa are supplied by two almost independent vascular systems. The finding of two systems, viz.: an axial and a parietal system, is in line with the observation of Charpentier et al. (1989) that the ontogeny of the ovary in Begoniaceae is determined by both a single axial meristern in the ovary base and several parietal meristems on the ovary wall. The present study supports Reitsma's (1983) hypothesis that in section Tetraphila the septa are more or less 'placental' (Chapter 7).

    The investigation of pollen grains usually corroborates with Van den Berg's (1984) conclusions regarding the pollen morphology and pollen-type of the species studied here. However, this study indicates that there appears to be a transition between the B. squamulosa pollen-type and the B. komoensis pollen-type . Pollen grain size may be indicative for the ploidy level of a specimen of either B. elaeagnifolia or B. squamulosa (Chapter 8).

    In Chapter 9, it is discussed why the taxa recognized here are accorded the rank of species. With the exception of B. rwandensis, the species are sympatric and appear to have more or less similar ecological requirements. Various observations and crossing experiments indicate that the sympatric taxa, which may be found growing close together in the same locality, are reproductively isolated.

    Within their basic distribution several of the species have a localized topography that coincides with presumed African pleistocene rain forest refuges. It is inferred that gene flow among local populations is limited, while the possibility of gene flow among populations from geographically separated regions can be excluded. Finally, the phylogenetic relationships of the species are discussed.

    The taxonomic treatment in Chapter 10 includes a key to the species. They are described, typified and illustrated. Full synonymy, references to taxonomic literature and all the available material are cited. Distribution maps show where the species have been collected.

    Growth and development in Achimenes cultivars
    Vlahos, J.C. - \ 1991
    Agricultural University. Promotor(en): J. Doorenbos. - S.l. : Vlahos - 132
    sierplanten - potplanten - groei - plantenontwikkeling - licht - fotoperiode - fotoperiodiciteit - schaduw - achimenes - binnen kweken (van planten) - ornamental plants - pot plants - growth - plant development - light - photoperiod - photoperiodism - shade - achimenes - indoor culture

    Achimenes is a herbaceous perennial of the Gesneriaceae family. Its origin is Central and South America. It has been cultivated as a pot plant since the Victorian era. Extensive hybridization has produced many attractive cultivars which have been Introduced in commercial floriculture both In the United States and Europe. Commercial Achimenes cultivars have short erect stems bearing flowers in the axils of the leaves and form rhizomes at the tips of underground stolons. At the end of the growing period, in late summer, the plants enter a period of senescence and rhizomes undergo a period of dormancy before they sprout for a new plant production in early spring . Thus cultivation of Achimenes is limited to one crop per year.

    The aim of the present study was to describe the effect of the environment, mainly light and temperature, on plant growth and development In order to realize optimum flower and / or rhizome production . Moreover the possibilities to manipulate plant development and release of rhizomes from dormancy by means of growth regulators are indicated.

    Vegetative growth and flower development

    Growth and flowering were strongly affected by treatments involving duration, intensity and quality of light (Chapters 1 through 4). Longer photoperiods increase vegetative growth in most Achimenes cultivars. LD (16 h) increased plant height, shoot weight and number of flowers compared to SD (8 h). Increased duration of illumination, of the same light level, increased shoot dry weight and reduced plant height (Chapter 2). When the same daily light integral was maintained, long day i.e. low light Intensity favoured growth and flowering and increased relative growth rate (Chapter 3). This is due to increase in net assimilation rate but not in leaf area ratio suggesting a better light use efficiency when a low light intensity is combined with longer days. When daylength was extended with low intensity incandescent light (low R/ FR ratio) total leaf area , total dry weight of the plant and leaves Increased . Fluorescent light (high R/ FR ratio) had no effect on total dry weight of the plant. Number of flowers was not influenced by light quality except in 'Rosenelfe' where number of axillary shoots was suppressed by incandescent light and flowering was promoted by fluorescent light . Furthermore, light duration and quality influenced calculated parameters of growth. Daylength extension by either incandescent or fluorescent low intensity light increased relative growth rate , net assimilation rate and lowered leaf area ratio (Chapter 4).

    Vegetative and generative growth were Influenced by the temperature treatments. Higher temperatures Increased plant height, number of leaf whorls and flowers and reduced time to anthesis (Chapters 2 and 4). At 25 °C , total leaf area and total dry weight of the plant increased compared to 17 °C Application of gibberellic acid (GA 3 ) alone or in combination with benzyladenine (BA) and 1 or naphthalenacetic acid (NAA) increased plant height and weight of aerial plant parts but number of flowers was not affected (Chapters 6 and 7). The growth retardants Ancymidol, Paclobutrazol and 5-3307 suppressed plant height and development of axillary shoots and flowers in 'Viola'. The effects of the growth retardant treatments were more pronounced under shade rather under full sunlight. The growth regulators used in this study do not cause any desirable effects in Achimenes as plants become either too tall (GA 3 ) or stunted (retardants) with subsequent adverse effects on flowering (Chapter 8).

    Rhizome formation and development

    In general rhizome development seemed to be correlated to shoot growth. Daylength hardly influences number of rhizomes, however, in some cultivars number and fresh weight of rhizomes increase in SD (Chapter 1). LD or continous ligh tdid not inhibit rhizome formation and development (Chapter 2). Higher irradiance levels, increased number and dry weight of rhizomes, along with increases in dry weight of the aerial parts, indicating that rhizome development depends largely on the accumulation of metabolites provided by increased assimilation of the above ground parts. light quality ( incandescent vs. fluorescent light) affected dry weight of rhizomes depending on the cultivar. Fluorescent light increased dry weight of rhizomes in 'Flamenco' only. Number of rhizomes was not affected by light quality. Temperature had no effect on rhizome development or on rhizome weight ratio (percentage of dry matter incorporated into rhizomes ) as shown in Chapters 2 and 4.

    Application of GA3 reduced rhizome weight ratio whereas the combination of BA and NAA increased dry weight of rhizomes (Chapter 7). BA also increased fresh weight of rhizomes whereas GA3 reduced it (Chapter 3). The use of growth retardants, however, did not promote rhizome development but in some cases even reduced it. This finding confirms that rhizome development depends on good shoot growth.

    Sprouting of rhizomes

    Freshly harvested rhizomes are released from dormancy with either benzyladenine (BA) or giberrellic acid (GA 3). Soaking rhizomes of 'English Waltz' in a BA solution (50 mg.l -1) and keeping them at 25 °C in the dark for two weeks resulted in the highest percentage of sprouting . Soaking rhizomes of 'Viola' in GA 3(50 mg.l -1) for 16 h also promoted sprouting depending on subsequent storage treatment. Continous light during storage inhibited sprouting whereas in continous darkness at 21 or 25 °C resulted in 100% sprouting in three weeks. When rhizomes were cut in half the apical halves always sprouted first and more than the basal ones. Rhizomes which had been treated with GA 3produced taller plants with more leaf whorls, flowering earlier with more flowers. High temperature pretreatment of rhizomes increases the number of flowers produced. This is the result of the promotive effect of temperature on sprouting which subsequently affects flowering. Earlier sprouting ensures earlier flowering.

    Varietal differences

    Several cultivars were studied. Plant height, number of axillary shoots, flowers , earliness , number and dry weight of rhizomes are clearly cultivar characteristics usually not influenced by environmental factors. Certain cultivars are slow in forming rhizomes. During the period of the experiments 'Blauer Planet' did not form any rhizomes at all. 'Prima Donna' , 'Viola ' and 'Hilda' formed very few. In 'Hilda' the relative growth rate was lower than in in 'Flamenco ' or 'Rosenelfe'. Responses to temperature also varied among cultivars. 'Rosenelfe' and 'Hilda' were the most responsive and this was due to increased net assimilation rate at higher temperatures (Chapter 4).Leaf morphology was responsible for some of the differences observed. 'Early Arnold' had greater total leaf area and total dry weight of leaves and plant due to a high net assimilation rate which was attributed to its large thin leaves, 'Linda' on the other hand, had a low net assimilation rate because of its many and small leaves which caused more internal shading. It is concluded that differences in the mean values for net assimilation rate and leaf area ratio are responsible for the differences observed among cultivars.

    Levels of endogenous hormones may be responsible for some differences among cultivars. 'Flamenco' had a low shoot weight whereas rhizome dry weight was high. It also responded to the far red light treatment by decreasing the dry weight of rhizomes. Relative growth rate and fresh weight per rhizome were greater in 'Flamenco' rather than in 'Hilda' or 'Viola'. It was shown that the number of flowers is correlated to height of the main stem and number of leaf whorls. Furthermore, 'Rosenelfe', 'Blau Import' and 'Tetraelfe' had a higher number of flowers per plant as they bear flowers in clusters of 3 to 9 from the leaf axils where the other cultivars bear only one or two. All cultivars tested flowered regardless of daylength thus confirming that Achimenes is a day neutral plant.

    It is concluded that it is possible to control growth and flowering in Achimenes through temperature and light, the latter being the more crucial factor . Dormancy of rhizomes can be broken and sprouting enhanced with the use of growth substances. Thus the time interval between two growing seasons can be shortened. However, additional light, at least of the same levels and/or duration as in the present experiments, should be given during winter months. The right choice of cultivar, depending on the intended purpose of cultivation (flower or rhizome production) is also an important factor to consider. Growth regulators are not recommended for application to whole plants except for the purpose of increasing rhizome production.

    Evaluation of techniques to determine the protein digestibility of heat-processed beans for pigs.
    Poel, A.F.B. van der; Doorenbos, J. ; Huisman, J. ; Boer, H. - \ 1991
    Animal Feed Science and Technology 33 (1991). - ISSN 0377-8401 - p. 331 - 341.
    Schorsing en ontslag van de directeur der Gemeenteplantsoenen S.G.A. Doorenbos
    Belder, J. - \ 1988
    Jaarboek / Geschiedkundige Vereniging Die Haghe (1988). - ISSN 0923-2931 - p. 99 - 111.
    Influence of temperature on bud break, shoot growth, flower bud atrophy and winter production of glasshouse roses
    Berg, G.A. van den - \ 1987
    Agricultural University. Promotor(en): J. Doorenbos. - S.l. : Van den Berg - 170
    bloei - bloemen - warmte - sierplanten - plantenontwikkeling - plantenfysiologie - teelt onder bescherming - temperatuur - rosa - flowering - flowers - heat - ornamental plants - plant development - plant physiology - protected cultivation - temperature - rosa

    The influence of temperature in the range 15-22 °C on growth, production, quality and flower bud atrophy ('blindness') of the rose cultivars Sweet Promise and Varlon was studied. The roses were grown in Dutch glasshouse soil under natural light conditions and studied from October until May during 7 successive years. The influence of the distribution of the air temperature between day and night was studied. Besides the usual night-lower-than-day-temperature regime, also the reverse situation was studied. 'Models' were constructed for: bud break, development time from bud break until harvest, shoot and flower bud weight, shoot length, the length, width, volume and freshweight of the flower bud during harvest and the diameter of shoot and neck, in relation to date of bud break and mean daily temperature during shoot growth.

    Complementary studies including roses of the cv. Sweet Promise grown in transferable containers were performed in glasshouses and in growth rooms (Phytotron). In these experiments the interaction of temperature and shoot stage with the development time of a shoot, with shoot weight and with shoot length was studied. Shoot weight showed a clear interaction with temperature if night temperature was higher than day temperature. Various shoot stages showed a different sensitivity to temperature with respect to the formation of flowerless ('blind') shoots. A low night temperature during the period cut until shoot elongation (=4cm) decreased blindness, but increased blindness when given in the next period until the flower bud is clearly visible. Higher night temperatures than those commonly used increased production by decreasing the percentage of blind shoots.

    At a given daily mean temperature an increase in night temperature showed no significant influence on bud break and development time of a shoot but fresh shoot weight and shoot length are significantly reduced, if night temperature increases above day temperature. The mean temperature and the mean irradiance during shoot growth could account for 98 % of the variation in the relevant 'models' when analysed by linear regression analysis. Adding the variable 'relative humidity' to the regression equation explained 97 % of the variation in shoot weight. To explain 87 % of shoot length the variable 'Weight of the Parent shoot' and the square of the temperature had also to be introduced.

    Heavy parent shoots produced heavier daughter shoots than light parent shoots. The difference in fresh weight for daughters of heavy parent shoots compared to those of light shoots decreased in autumn and increased again in spring. If light intensity decreased in autumn, less light was used to produce one gram fresh shoot weight, while under increasing light intensities more light was used.

    Fresh weight production per shoot per day increased with temperature for the cultivar Varlon and as a consequence, the amount of light needed per gram fresh weight decreased. In the period December until the middle of March 'Sweet Promise' showed another, reversed, situation: fresh weight production decreased with temperature. This was caused by the fact that 'Sweet Promise' was weakened more by a raise in temperature than "Varlon'. Production in number of flowers and in grams fresh weight per shrub showed a positive linear correlation with temperature for both cultivars.

    The course of bud break and harvest was studied for 9 night/day temperature combination. A lower temperature resulted in delayed bud break and production.

    The research made it clear that it is possible and profitable to control temperature on the basis of the daily mean temperature or the temperature sum during bud break and shoot growth, instead of in the orthodox way with a fixed night-lower-than-day temperature regime. Practical applications of the results are given for commercial rose growing. Heating glasshouses on a basis of a daily mean temperature or temperature sum instead of a given day and night temperature is a possibility of saving energy, as also is the maintaining of a diurnal period of up till 6 hours with a higher night than day temperature beginning at sunset when the thermal screens are closed.

    Soil heating until 20 °C did not influence production and quality,whilst a 12% reduction in light had a negative effect on both.

    Van plant tot gewas.
    Doorenbos, J. - \ 1986
    Wageningen : Landbouwuniversiteit Wageningen - 19
    wilde planten - tuinbouw - nieuwe cultuurgewassen - wild plants - horticulture - new crops
    Adventitious shoot formation on leaf cuttings in vivo, a tool in horticulture
    Custers, J.B.M. - \ 1986
    Landbouwhogeschool Wageningen. Promotor(en): J. Doorenbos; R.L.M. Pierik. - Wageningen : Agricultural University - 129
    bollen - bladstekken - verjonging - onderzoek - bulbs - leaf cuttings - regeneration - research

    Adventitious shoot formation implies the regeneration or development of shoots from fully differentiated tissue. Its application has, after the rise of in vitro culture, assumed large proportions. Then the question arose whether in vivo adventitious shoot formation could not be applied more widely in commercial horticulture. To answer this question investigations were made on the regeneration of leaf cuttings and the results are presented in this thesis.

    It was found that the majority of a large number of plant species and cultivars was unable to regenerate shoots on leaf cuttings spontaneously. Various attempts to induce shoot regeneration with the cytokinin 6-benzylaminopurine (BA) were unsuccessful. BA had a positive effect, however, in a few species which regenerated shoots spontaneously (Chapter 1). These findings led to investigation of the effectiveness of plant growth regulator treatments to induce shoot regeneration in four species, Brassica oleracea , Lunaria annua , Nicotiana alata and Ruta graveolens , of which it was known that they were able to regenerate shoots, but which differed in the capacity to do so (Chapter 2). Cytokinins and auxins were applied prior to planting the cuttings as well as after roots had been formed. In all four species the treatments had marked effects. They fitted into two already known reaction patterns: that described by Skoog and Miller (1957) in which shoot regeneration is promoted at a high cytokinin/auxin ratio, and that described by Harris and Hart (1964) in which auxin is promotive for shoot regeneration. A new feature was that leaf cuttings from one and the same species showed both reaction patterns, as was found for Lunaria annua and Nicotiana alata . From these results it was concluded that regulator treatments still can be rather effective.

    As was shown in Chapter 1, simple applications of cytokinin were insufficient to induce shoot regeneration on leaf cuttings of. plant species with low regeneration capacity. Therefore the research was concentrated on one species, chrysanthemum ( Chrysanthemum morifolium ), of which an easy to regenerate genotype, cv. Bravo, and a difficult one, cv. Super Yellow, were used. Chapter 3 describes how shoot regeneration in 'Bravo' can be influenced by environmental factors. As a rule, at moderately high temperatures (13-17 °C) good results were obtained. Pretreatment with low temperature (9 °C) during the rooting phase had an additional favourable effect on the induction of shoot regeneration, whereas high temperature (21 - 25 °C) during the final phase accelerated the realization of the regeneration. Daylength of 8 h (SD) initially delayed the appearance of the adventitious shoots compared with daylength of 16 h (LD), but after some time the percentage of shoot formation was the same under both conditions. The leaf cuttings could not stand a high light intensity (>approx. 30 WM -2), which accelerated senescence and decreased shoot regeneration. Young leaves provided cuttings which regenerated better than those from old leaves, and leaves from vegetative plants were better than those from so-called crown bud plants, i.e. plants which have formed flower buds in LD and which, in general, show less vigorous growth.

    Shoot formation in 'Bravo' started about 18-20 weeks after planting, when the leaf cuttings began to senesce by degrees. This was called late shoot formation. The leaf cuttings from ' Super Yellow ' , studied under the same conditions as ' Bravo ' , never regenerated shoots. Cytokinin applied before planting gave shoot regeneration in both cultivars as early as nine weeks after planting; this was called early shoot formationApplication of auxin, notably indole-3-acetic-acid (IAA), together with cytokinin increased early shoot formation, yet the rate of success always remained very low under various experimental conditions. It was not possible either to establish the optimum concentrations of the regulators. However, low to moderately high temperature (9-17 °C) in the cutting benches was found to be an essential condition (Chapter 4).

    In a number of experiments it was shown that the developmental stage and pretreatments of the stock plants had a pronounced effect on early shoot formation of the chrysanthemum leaf cuttings (Chapter 5). Leaf cuttings from crown bud plants gave much higher percentages of early shoot formation than those from vegetative plants: around 85% at the optimum concentrations of the regulators (BA 6.25 - 12.5 mgl -1+ IAA 45 mgl -1). Small leaves from the inflorescences of plants which are about to start flowering also appeared to be very suitable. The most striking result was noted in leaf cuttings from plants which had stood for about a month in dim light (0.6-6 Wm -2). After 4-6 weeks a few dozens of adventitious buds per cutting arose, scattered over the entire length of the petiole. The pattern of this regeneration closely resembles that of regeneration in vitro. of these buds only a small part developed into plantlets. Moreover, many leaf cuttings were lost by rotting, particularly because they were very etiolated and tender as a result of the stock plant treatment.

    From the observation that the stock plant had such a strong influence a hypothesis was put forward regarding the process of shoot regeneration (Chapter 5 and General Discussion). In leaf cuttings from normally grown plants it is likely that regeneration inhibiting factors exist in the tissues surrounding the place of regeneration. Pretreatment of the stock plants reduces this inhibition and then the leaf cuttings can respond to shoot regeneration inducing factors like cytokinin, i.e. leaf cuttings are physiologically conditioned by the pretreatment. This hypothesis holds not only for early but also for late shoot formation where no regulators are applied just before planting the cuttings. In late shoot formation the physiological conditioning only starts when the leaf cuttings are gradually senescing. Moreover, this hypothesis explains why in vitro regeneration generally is easier than the in vivo regeneration described here: in the small explants commonly used in vitro there is only a low amount of surrounding tissue left which can inhibit shoot regeneration. Thus the small size of the in vitro explants will have the same effect as the stock plant pretreatment in the case of in vivo regeneration. From a practical point of view, however, excision of small explants is much easier than pretreatment of whole plants. Therefore, it was concluded that in plant species with a low to moderately high regeneration capacity, like in chrysanthemum studied here, in vivo shoot regeneration cannot match the results in vitro.

    For practical application, in vitro shoot regeneration should be preferred to in vivo regeneration in the case of recalcitrant species. For species with a high regeneration capacity, however, it is not so clear which of the two procedures has to be chosen. Shoot regeneration in plants with such a high regeneration capacity is described in Chapters 6 and 7; it concerns certain 'Elatior' -begonia (Begonia x hiemalis ) cultivars. In general with Begonia spp. SD and low temperature promote shoot regeneration, but literature on 'Elatior'- begonias contains different views on this aspect. Our experiments showed that only a short period of SD (4-14 days), applied either to the stock plants or to the cuttings, was favourable, promoting the early phase of adventitious bud initiation. A long period of SD (>28 days) applied to the cuttings had an adverse effect on the growth of these buds; no shoots emerged from the soil. Low temperature had not the same effect as SD and shoot regeneration was generally better when high temperatures (21-25 °C) were used in the cutting benches (Chapter 6).

    The effects of regulators on regeneration in Begonia spp. generally fit well into the reaction pattern as described by Skoog and Miller (1957): cytokinin promotes shoot regeneration and auxin root regeneration. When applied to the 'Elatior'- begonias, however, BA had an adverse effect; the number of initiated adventitious buds was increased, but shoot growth and development were completely disturbed and inhibited. A low auxin concentration (IAA 0.2-1 mgl -1) promoted adventious shoot formation. Combination of high BA concentration (25 mgl -1) with high IAA concentration (5-25 mgl -1) led to regeneration of many buds, distributed all along the petiole, but only a small number developed into shoots (Chapter 7).

    It was supposed that with the 'Elatior'-begonias the investigated factors influence mainly the last phases of the regeneration process, bud initiation and shoot development. The earlier phase of shoot regeneration induction proceeds rapidly and presents no problems. So in this respect there is no reason to change over to in vitro procedures.

    Finally, from the results presented in this thesis conclusions were drawn concerning efforts to attain a wider application of in vivo adventitious shoot formation in horticultural practice. On the one hand such efforts are very meaningful for species with a high regeneration capacity, on the other hand they are not for species with a low capacity. For the latter, in vitro procedures can be used with a much better result than the in vivo procedures.

    Domestication of Begonia
    Doorenbos, J. - \ 1985
    Acta botanica neerlandica 34 (1985). - ISSN 0044-5983 - p. 230 - 231.
    S.G.A. Doorenbos leven en werk
    Belder, J. - \ 1984
    Dendroflora (1984). - ISSN 0374-7247
    amenity and recreation areas - biographies - design - forestry - gardens - green belts - public gardens - public parks - silvicultural characters
    Kalanchoe at Wageningen
    Karper, J.J. ; Doorenbos, J. - \ 1983
    The Garden 108 (1983). - p. 237 - 239.
    Begonia pearcei, a favorite early tuberous species
    Doorenbos, J. - \ 1982
    The Begonian 49 (1982)1. - p. 30 - 33, 39.
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