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
    Wageningen University & Research
    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 Publ.no. 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.
    J. African soil yields surprise - Is it begonia scapigera?
    Doorenbos, J. - \ 1982
    The Begonian 49 (1982). - p. 147 - 149.
    Tuinbouw, een verzameling vrij sterk uiteenlopende bedrijfstakken
    Doorenbos, J. - \ 1981
    TNO-project : tijdschrift voor toegepaste wetenschappen 9 (1981)11. - p. 385 - 393.
    Lots of names, but it's Begonia oxyloba
    Doorenbos, J. - \ 1981
    The Begonian 48 (1981)6. - p. 136 - 138.
    De bloemproduktie van gerbera
    Leffring, L. - \ 1981
    Landbouwhogeschool Wageningen. Promotor(en): J. Doorenbos. - Wageningen : Leffring - 86
    asteraceae - snijbloemen - groei - sierplanten - plantenontwikkeling - asteraceae - cut flowers - growth - ornamental plants - plant development
    The morphology of gerbera seedlings was studied in order to establish which factors determine flower yield and to see whether there are differences between the plants concerning their characteristics.

    The gerbera has a sympodial rhizome which forms 7 - 24 leaves before initiating a flower bud. This flower is formed by the apical meristem. Almost simultaneously a second flower bud develops in the axil of the uppermost leaf primordium while a vegetative axis develops in the axil of the second leaf primordium from the top. After a number of leaves (2 - 8; see Chapter 2) this axis forms a terminal flower bud, a lateral flower and again a vegetative continuation. The sympodium thus formed, has been regarded as the main stem.

    Shoots initiated in the lower leaf axils are called lateral shoots; these also show sympodial growth.

    Results of a one-year experiment with seedlings show a positive correlation (at flower initiation as well as after 1 year) between the number of lateral shoots and the number of leaves and flowers. No correlation was found, however, between leaf production and flower yield, although as the number of leaves increases the production of flower buds is promoted. This can be explained by flower bud abor tion: the more leaves, the higher the percentage of aborting flower buds.

    In order to investigate the influence of external factors on the plant characte ristics important for flower production, four different phaenotypes have been propagated vegetatively and subjected to treatments with different daylengths, light intensities and temperatures.

    I. Daylength
    All clones performed best at a daylength of 8 to 10 hours. Short day (8 hours) promotes flower yield as compared to long day (16 hours) because under short day conditions
    - the main axis shows earliest flowering and also the highest number of continua tions,
    - the highest number of lateral shoots are initiated and also form the highest amount of continuations,
    - these combined reactions of main axis and lateral shoots result in optimum flower bud formation.
    Daylength does not seem to influence flower bud abortion.

    II. Light intensity
    High light intensity increases flower yield. This has been demonstrated in an experiment with high and low light intensities, as well as in all experiments carried out in autumn when the amount of natural light is diminishing. The reason is that under high light intensity conditions:
    - the highest number of lateral shoots are formed, with a high number of conti nuations,
    - consequently flower bud production is larger,
    - the highest flower bud abortion is found during the months with the lowest light intensity.
    In the experiment with different light intensities no difference in abortion ra te could be found, however.

    III. Temperature

    Low temperature enhances all the effects caused by short day: more lateral shoots are initiated and more shoots flower. Low temperature also causes less flower bud abortion than high temperature in this case. Under high light intensity conditions low temperature enhances the above mentioned effects by accelerated continuation of the lateral shoots as compared with high temperature. The reason for this pheno menon is the formation of less leaves per continuation at low temperature.

    All clones showed the same tendency in their reaction to daylength and light in tensity, although there were quantitative differences. With respect to the tem perature the clones behave differently: three of them prefer a low temperature, while the fourth prefers a high temperature.

    Main shoot and lateral shoots influence eachother. When the main shoot is taken away, more lateral shoots are formed; when the lateral shoots are taken away, the main axis continues faster. However, neither treatment increases total flower yield.
    Again the four clones show the same tendency. but the rate of reaction varies. The stronger the apical dominance of the main axis, the stronger also the influence of the lateral shoots on the main axis.

    Defoliation to various degrees serves no purpose, as this does not affect leaf, shoot or flower bud production, nor flower bud abortion, which means that there is no difference in flower yield. This held true for all clones.

    Bloemproduktie bij Alstroemeria 'Walter Fleming'
    Vonk Noordegraaf, C. - \ 1981
    Landbouwhogeschool Wageningen. Promotor(en): J. Doorenbos. - Wageningen : Vonk Noordegraaf - 152
    amaryllidaceae - sierplanten - amaryllidaceae - ornamental plants
    Alstroemeria is a relatively new crop in floriculture and is rapidly increasing in popularity. The plant is a herbaceous perennial and produces flowers that are attractive and long lasting. Some authors refer this genus to the family Amaryllidaceae, other to the Liliaceae, and same prefer a separate family Alstroemeriaceae.

    The erect, unbranched shoots originate from a subterranean sympodial rhizome. Alstroemeria and some closely related genera are characterized by leaves which are twisted 180°, so that the morphological upper side is turned downwards. Under favourable conditions the shoots form terminal umbelliform clusters of flowers. During the growth period the roots thicken into tubers. The research described in this paper has been performed with the hybrid 'Walter Fleming', a cultivar of English origin, general grown in Holland under the name 'Orchid'.

    The aim of this research was to investigate the structure of the plant and its ecological reactions in order to realize optima production conditions and a better timing of the crop.

    SHOOT FORMATION

    Shoots are initiated on a subterranean rhizome and its branches. Under greenhouse conditions, the number of shoots increases rapidly after the winter period. At that tine many rhizomes are active and the shoots grow fast. During flowering and shortly after, however, there is a rest period following which shoot formation is resumed. Until the beginning of the flowering period there is no significant influence of temperature (minimum 9°C) on shoot formation.

    Comparing growth at 17, 21 and 25°C shoot formation was found to increase with. increasing temperature. At 13 and 9°C shoot formation stops in long photoperiod and the plants enter a rest stage, firstly at 13°C and afterwards at 9°C. In the early stage of plant development shoot formation in plants grown at high temperature was stimulated by lowering the temperature and vice versa. Lowering the temperature caused the rhizomes to branch more, while raising the temperature caused more lateral shoots to develop. Rest started in the lateral rhizomes. Dormancy is prevented or broken by high temperature.

    High temperature stimulated shoot formation; there was no evidence of a specific diurnal effect however. High soil temperature also promoted shoot formation. At a temperature of 25°C both flowering and growth were completely inhibited.

    Low light intensity decreased the number of shoots produced. It was difficult however to determine the precise effect of light intensity because of the interaction with temperature.

    Shoot formation was inversely proportional to daylength. LDs inhibited growth of young shoots as well as the branching of rhizomes and SDs reversed the effect.

    FLOWER INITIATION

    Low temperature promoted flowering of Alstroemeria; it decreased the number of nodes below the inflorescence and shoots of more proximal origin flowered earlier. At 25°C and above no flowers were initiated. The number and percentage of generative shoots were not a useful-measure of induction as the number of shoots was also affected by temperature and daylength. The length of the temperature treatment during the 24 hour period had-more influence m flower initiation than either the day or night temperature. High soil temperature had a negative influence, this was more pronounced when the air temperature was high.

    The number and percentage of generative shoots was reduced by very low light intensity. Increasing daylength decreased the number of nodes under the inflorescence and the number of vegetative shoots per rhizome.

    The highest number of flowering shoots were produced at a daylength of 12 hours, which permitted both shoot formation and flower initiation to proceed.

    At a given daylength or temperature the further the shoots were from the proximal end of the rhizome, the earlier they flowered.

    FLOWERING

    In spring when daylength and temperature are favourable for flower initiation Alstroemeria flowers abundantly. The reduction in the number of nodes below the inflorescence is accompanied by a decrease in the number of days to flowering. The flowering period is markedly compressed by the fact that the youngest shoots i.e. those arising at the distal end of the rhizome, form less nodes below the inflorescence than proximal shoots. In addition, the increasing daylength induces earlier flowering. The influence of a given temperature on the flowering time is the result of its effect on flower initiation and rate of development. High temperature inhibits initiation but promotes development.

    The number of branches per umbel showed an unequal frequency distribution with a clear preference for 3, 5 and 8. This agrees with the phyllotaxis 3/8, which indicates that flower bud differentiation stops more frequently after initiation of a whole spiral than after a partial one. Numbers of branches per umbel are correlated with thickness of the main stem. The number of branches is influenced by daylength but not by temperature. Numbers of flowers per stalk increased with temperature to 21°C, but the differences were not statistically significant. In the greenhouse during winter most flower buds abort as a result of the poor light conditions.

    TUBER FORMATION

    Low temperature and LDs promote both flowering and thickening of the roots. During and just after flowering there was a strong increase in tuber growth. This increase of tuber weight can be attributed to resorption of substrates from the old shoots and their storage in the tubers. The nearly simultaneous swelling of the young, short roots just behind the growing points of the rhizome and the retardation of the growth of the young shoots indicate a common factor controlling both effects.

    FLOWERING TIME

    The main flowering of 'Walter Fleming' grown in greenhouses in the Netherlands occurs in the months of April, May and June, independent of the planting date. Flowering can be advanced by means of artificial lighting, but this should not be continued longer than necessary as shoot formation is retarded. A 4 hour nightbreak of cyclic lighting at an intensity of 100-150 mW over two weeks is suitable. Another method is to extend the daylength to 12 hours, this has only a small adverse effect m shoot formation.

    The high greenhouse temperatures in summer are unfavourable for flowering. A good second crop in late summer may be realized using mobile greenhouses, leaving the plants temporarily outdoors where the temperature is lower. In the greenhouses flower initiation occurs by the natural lowering of temperature during late summer and autumn. The success of this late flush however depends on the time of initiation as decreasing light intensity results in flower bud blasting. For this reason it is not desirable to induce flowering in autumn by extending the daylength.

    REST

    In their native habitat many Alstroemeria species enter a stage of rest during summer, this also occurs in the Netherlands. In 'Walter Fleming' the symptom are highly dependent on temperature and daylength. Low temperature and LD not only promote flowering and tuber growth, but also rest. At high temperature LDs cause only a reduction of shoot growth which disappears in SDs. When plants grow at low temperatures (9 or 13°C) and LDs they enter a state of complete rest, with shoots dying off after flowering. This Test can be broken by a long period of high temperature.

    Removing flower buds or shoots and harvesting flowers diminishes the rest period. When old shoots are left on the plants they promote rest.

    In the discussion this pattern of reactions of 'Walter Fleming' is compared with that of other crops. The reactions are discussed in relation to the climate in the native habitat of the supposed parent species of this hybrid. Since Alstroemeria presents a wide variation of species growing under extremely different climatic conditions, it is to be expected that hybrids my be bred in which flower production and the flowering period can be controlled more easily.

    Begonia californica: is it really B. boissieri?
    Doorenbos, J. - \ 1981
    The Begonian 48 (1981)5. - p. 108 - 110.
    A Begonia grown as a vegetable
    Doorenbos, J. - \ 1981
    The Begonian 48 (1981)1. - p. 4 - 17.
    The yellow-flowering species from Africa
    Doorenbos, J. - \ 1980
    The Begonian 47 (1980). - p. 12 - 37.
    Borneo's large-flowered Begonia burbidgei
    Doorenbos, J. - \ 1980
    The Begonian 47 (1980). - p. 105 - 112.
    Begonia rhopalocarpa, a begonia with colourful fruit
    Doorenbos, J. - \ 1980
    The Begonian 47 (1980). - p. 102 - 103.
    Begonia lindleyana: straightening out the confusion
    Doorenbos, J. - \ 1980
    The Begonian 47 (1980)9. - p. 244 - 248, 253.
    Two Begonia species from Java new to cultivation
    Doorenbos, J. - \ 1980
    The Begonian 47 (1980)8. - p. 213 - 215.
    A farewell to Begonia 'nuri'
    Doorenbos, J. - \ 1980
    The Begonian 47 (1980)12. - p. 326 - 327.
    Begonia vitifolia and other elusive tree-like begonias
    Doorenbos, J. - \ 1979
    The Begonian 46 (1979). - p. 234 - 240.
    The Omati-begonia cultivated
    Doorenbos, J. - \ 1978
    The Begonian 45 (1978). - p. 199 - 201.
    Spontaneoous mutation as a source of clonal variation on deciduous fruits
    Doorenbos, J. - \ 1977
    Acta Horticulturae 75 (1977). - ISSN 0567-7572 - p. 13 - 18.
    X-ray induced mutations in Begonia x hiemalis
    Doorenbos, J. ; Karper, J.J. - \ 1976
    The Begonian 43 (1976). - p. 97 - 99.
    Flowering and vegetative propagation of pyrethrum (Chrysanthemum cinerariaefolium Vis.) in vivo and in vitro
    Roest, S. - \ 1976
    Landbouwhogeschool Wageningen. Promotor(en): J. Doorenbos, co-promotor(en): R.L.M. Pierik. - Wageningen : Centre for Agricultural Publishing and Documentation - ISBN 9789022006221 - 105
    asteraceae - bloemen - vruchten - medicinale planten - plantenontwikkeling - plantenorganen - plantenfysiologie - vegetatieve organen van de plant - asteraceae - flowers - fruits - medicinal plants - plant development - plant organs - plant physiology - plant vegetative organs
    The influence of climatic conditions was investigated on flowering behaviour of pyrethrum ( Chrysanthemum cinerariaefolium Vis.). At low temperatures high numbers of plants initiated high numbers of flower heads. Both the development of the initiated flower heads and the vegetative development of the plants were stimulated by higher temperatures.
    The second aspect was the development of methods of vegetative propagation in vivo and in vitro. Through a culture of peduncle explants in vitro detailed information was obtained about the initiation and development of adventitious roots. With these data the process of adventitious root formation of shoot cuttings in vivo was optimalized. In practice this method of vegetative propagation in vivo may be useful for a fast multiplication of selected healthy plants with high yields of pyrethrins. Vegetative propagation was also achieved by initiation and development of adventitious shoots on capitulum explants cultivated in vitro and subsequent adventitious root formation of detached shoots. This procedure was applicable for vegetative propagation of several other Compositae.

    Begonia 'Velvet Queen'
    Doorenbos, J. - \ 1976
    The Begonian 43 (1976). - p. 271 - 271.
    Begonia Mysteries II: What is Begonia alnifolia?
    Doorenbos, J. - \ 1976
    The Begonian 43 (1976). - p. 262 - 264.
    Begonia mysteries I; the misleading red dot
    Doorenbos, J. - \ 1976
    The Begonian 43 (1976). - p. 211 - 213, 227.
    Begonia 'Kew species'
    Doorenbos, J. - \ 1976
    The Begonian 43 (1976). - p. 246 - 249.
    Chromosome numbers in Begonia.3.
    Legro, R.A.H. ; Doorenbos, J. - \ 1973
    Netherlands Journal of Agricultural Science 21 (1973)2. - ISSN 0028-2928 - p. 167 - 170.
    Chromosome numbers in. Begonia. 2.
    Legro, R.A.H. ; Doorenbos, J. - \ 1971
    Netherlands Journal of Agricultural Science 19 (1971)3. - ISSN 0028-2928 - p. 176 - 183.
    Chromosome numbers in Begonia.
    Legro, R.A.H. ; Doorenbos, J. - \ 1969
    Netherlands Journal of Agricultural Science 17 (1969)3. - ISSN 0028-2928 - p. 189 - 202.
    Effects of temperature and light on growth, flowering and corm formation in Freesia
    Mansour, B.M.M. - \ 1968
    Wageningen University. Promotor(en): J. Doorenbos. - Wageningen : Veenman - 76
    sierplanten - iridaceae - groei - plantenontwikkeling - ornamental plants - iridaceae - growth - plant development

    Scope

    When Freesias are planted throughout the year several problems arise. In some months, flowers are produced too rapidly and abundantly, with a corresponding loss in quality; in other months, flower production is limited and too slow. Simultaneously, there is a great variation in stem length, in number and shape of the flowers and in corm production.

    This study was undertaken to establish the effect of the two major inveronmental factors, temperature and light, on the characteristics mentioned, from the moment of planting to the harvest of the corms.

    Conclusions

    From this study on the effect of temperature and light on the development of the Freesia plant, the following conclusions could be drawn:

    Effects of temperature in the range of 9-24°C:

    1. Sprouting of the corms was promoted by high temperature (experiments 1,4,19).

    2. The number of leaves was reduced (i.e., Rower initiation was promoted) by low temperature, and increased by high temperature, especially 21° and 24°C (experiments 1, 3, 4, 5, 19). There was a further reduction by a pretreatment at 5°C during 4 weeks (experiment 7). There was no specific effect of day or night temperature (experiment 4).

    3. The number of days to flowering reached a minimum at 18' (experiments 1, 3, 5, 19, 20; in experiment 4 the optimal temperature was 15°C and in experiment 2 it was 21°C. The night temperature was especially important (experiments 4, 5). There was a further reduction in the number of days to flowering by a pretreatment at 5°C for 3 or 4 weeks (experiment 7).

    4. The number of flowers in the main inflorescence was increased by high temperature (experiments 1-5, 19, 20; in experiment 3 there was a reduction at 24°C but it was also increased by a pretreatment at 5°C during 1 or 2 weeks (experiment 7).

    5. The number of lateral stems was reduced by high temperature; the greatest number was formed at 12°C (experiment 3) or 15°C (experiments 1, 2). A low night temperature was especially important (experiment 5).

    6. Stem length reached an optimum at 21 °C (experiments 1- 5, 19, 20); 24°C was unfavourable, especially in later stages (experiment 3). The effect of day temperature was much stronger than that of night temperature (experiments 4, 5). Stem length increased after a pretreatment at 5' during 1-2 weeks, but 4 weeks 5° led to stunted growth (experiment 7).

    7. Corm dry weight increased with the temperature (experiments 1, 2, 4, 19). The effect of day temperature was stronger than that of the night temperature (experiment 4, 5). Corm weight was reduced after a pretreatment at 5° during 3 or 4 weeks (experiment 7).

    8. The number of cormlets was decreased by high temperature (experiments 1-4, 19). A pretreatment of 1-2 weeks at 5°C increased it, but 4 weeks 5°C led to a decrease (experiment 7).

    Effects of the photoperiod in the range of 8 to 16 hrs:

    9. Leaf number was reduced (i.e. flower initiation was promoted) by short day (experiments 8, 12, 13, 19). The cultivar 'Sonata' was more responsive than 'Rijnveld's Golden Yellow' (experiment 15).

    10. The development of the inflorescence was strongly promoted in the early stages by short day (experiments 12, 13, 19) but later stages were promoted by long day, although not as strongly (experiments 11, 12).

    11. The number of flowers in the main inflorescence was reduced by long day (experiments 8, 10, 14), especially in the later stages (experiment 15). Long day also reduced the percentage of open flowers (experiments 9-12).

    12. The number of lateral stems decreased with the daylength (experiments 8-14) which was especially effective in later stages (experiment 15).

    13. There were no unequivocal effects of photoperiod on stem length experiments 9, 12, 15).

    14. Corm dry weight was proportional to daylength (experiments 8, 10, 12, 14), although it was sometimes lower again in the longest photoperiod (experiments 9, 11).

    15. The number of cormlets was greatest in short day (experiments 8-13).

    Effect of light intensity:

    16. Light intensity had little effect on the number of leaves (experiments 10, 13, 17), but low light intensity delayed flower initiation (experiments 13, 14), flower development (experiments 10, 13, 14, 17). It also reduced the number of flowers in the main inflorescence (experiments 13, 14, 17) and the precentage of open flowers (experiment 17). High light intensity increased the number of lateral stems (experiment 13). Stem length was usually slightly promoted by low light intensity (experiment 14, 17). Corm dry weight was proportional to light quantity (experiment 13, 14, 16, 17). The number of cormlets was reduced by low light intensity (experiment 10).

    Comparison of effects on light and temperature:

    17. Within the given ranges of these two factors the effect of temperature was usually greater than that of light. Only the number of lateral stems was determined primarily by the light conditions. As a rule, a higher temperature had a similar effect as a longer photoperiod (experiments 19, 20).

    Effect of planting date (experiment 21):

    18. The greatest number of leaves (and also the longest time to flower initiation) was found after planting in May and June, the smallest number of leaves after planting in February. The minimum number of days to flower initiation occurred after planting between November and January.

    19. The minimum number of days between planting and flowering occurred after planting in January and February; plants started in May took the longest time to flower.

    20. The number of flowers on the main inflorescence reached a maximum after planting in May and June and a minimum after planting between October and February.

    21. The number of lateral stems was high in plants started in June and low after planting in November and April.

    22. Stem length and plant height were greatest after planting between June and August and smallest after planting in February and March.

    23. Corm and cormlet dry weight were highest after planting in summer and low after planting in winter; the number of days between planting and harvest showed the opposite trend.

    Effect of planting density (experiment 21):

    24. In comparison to plants at a small distance, those at a wider distance were shorter, had more lateral stems and more flowers, a greater corm dry weight and more cormlets.

    25. The number of days to flowering was not affected by the planting density when the plants were started between November and March. Plants started between March and August flowered earlier when at a smaller distance; those started between September and November, however, flowered slightly earlier when at a greater distance.

    Selectieve teelt van tulpen gebaseerd op produktie-analyse
    Hekstra, G. - \ 1968
    Wageningen University. Promotor(en): J. Doorenbos. - Wageningen : Pudoc - ISBN 9789022001639 - 83
    tulpen - liliaceae - bloembollen - teelt - selectie - tulips - liliaceae - ornamental bulbs - cultivation - selection
    In tulip cultivation many stocks of good producing varieties in course of time showed a decrease in production of large marketable bulbs. Meanwhile the number of small bulbs in these stocks increased. This phenomenon was investigated. It was attributable to three causes: contamination of the stock by either foreign material ('thieves') or mutants originating from the variety itself ('wild'); a wrong temperature treatment of the planting material; differences in production between the several bulb types growing at different places in the mother bulb.

    The newly produced bulbs were named, after the scale of the mother bulb in whose axil they were formed, as A, B, C, and D for the fleshy scales (from inside to exterior) and H for the dry tunic. The production pattern of all types and grades was studied during three years. Especially the A and H bulbs were superior to the others in productivity. Second were B bulbs, followed by C and D. This productivity was not concerned with weight increase but to growth of the main bulb and offset number, which should not be too high.

    Based on these results a selection scheme was proposed to eliminate all bulbs inferior in productivity. This scheme was the basis for tulip cultivation with selection in the meantime, so that productivity of the stock stayed maximum.

    Effects of light and temperature on growth and flowering of carnation (Dianthus caryophyllus L.)
    Abou Dahab, A.M. - \ 1967
    Wageningen University. Promotor(en): J. Doorenbos. - Wageningen : Veenman - 68
    caryophyllaceae - sierplanten - groei - plantenontwikkeling - caryophyllaceae - ornamental plants - growth - plant development
    Both a long photoperiod and strong illumination strongly promoted growth and flowering. These conditions diminished the number of leaf pairs below the flower and promoted growth of flower buds from initiation to bud emergence from the leaves. The subsequent phases to anthesis were little affected by photoperiod and light intensity. Other characters such as stem length, stem diameter, leaf length and width, flower diameter and petal number were affected more by strength than by duration of illumination.

    Flower induction was promoted by cold (5°C). But as soon as the flower had been initiated, its development was promoted by warmth.

    Carnations were planted the year round at two-week intervals. The shortest time between planting and harvest was 4 months, after planting in April, the longest 8 months, after planting in September. Treatment at 5°C for three weeks reduced the time to the first crop when plants were started between July and November and increased it in plantings between January and June. There was no residual effect of cold on the second crop.

    Vertraagde onverenigbaarheid by die ent-kombinasie van tamatie op Datura stramonium
    Erasmus, S.P. - \ 1965
    Wageningen University. Promotor(en): J. Doorenbos. - Wageningen : Veenman
    cultuurmethoden - solanum lycopersicum - tomaten - cultural methods - solanum lycopersicum - tomatoes
    Glasshouse tomatoes grafted onto Datura stramonium could grow vigorously to 1 metre in height, then suddenly wilt and die. Several experiments under glass in spring, summer and autumn studied the nature of this delayed incompatibility. The results suggested that the wilting was caused by a gradually developing imbalance. To test this hypothesis plants were treated to give different distributions of growth between tomato graft and datura rootstock. Factors investigated were the fruit crop, assimilation surface, light energy, additional shoot development, a 'feeding' tomato shoot with about 8 leaves just above the graft union from which the apex and all other growing organs were removed.

    It was concluded that if root growth was depressed more or stimulated less than shoot growth, the plant wilted. If root growth was stimulated more than shoot growth, wilting was prevented.

    Erasmus investigated how increased suction tension influenced wilting in grafted plants grown in nutrient solution. The values for osmotic pressure of the solutions were raised 49 days after planting by different amounts of NaCl. The wilting in fruiting grafted plants was caused by the higher proportion of shoot to root.

    Veredeling van witlof voor het trekken zonder dekgrond
    Huyskes, J.A. - \ 1963
    Wageningen University. Promotor(en): J. Doorenbos. - Bennekom : Modern - 72
    cichorium intybus - cichorei - teelt - cultuurmethoden - cichorium intybus - chicory - cultivation - cultural methods
    Forcing of Belgian endive without covering soil could improve work efficiency. Existing varieties gave loose instead of well closed heads. To improve this, a study was made of factors determining head formation, with covering soil. Roots should be exposed to a certain amount of cold, if they were to form a good head. The later the variety, the more cold was required. Roots to be forced without covering soil needed extra cold. Varieties must be bred for this purpose.

    The breeder could use the need for cold as a criterion in selection for earliness and to improve the uniformity of his varieties. The length of the core was negatively correlated with the need for cold. This character was also of use in testing of varieties. The result of early forcing could be improved by previously cooling the roots.

    Practical trials on forcing without covering soil and selection for core length confirmed the results of the research.

    A literature survey of seepage in canals : preliminary report L7
    Doorenbos, J. - \ 1963
    Wageningen : ILRI - 59
    bibliografieën - kanalen - kanalen, klein - efficiëntie - irrigatiewater - lekkage - bekledingen - verliezen - verzegelen - kwel - bibliographies - canals - channels - efficiency - irrigation water - leakage - linings - losses - sealing - seepage
    Op zoek naar de optimale groeivoorwaarden voor het gewas
    Doorenbos, J. - \ 1963
    Wageningen : Unknown Publisher - 17
    tuinbouw - planten - klimaat - seizoenen - ecologie - gewassen - landbouw - fenologie - acclimatisatie - plantkunde - horticulture - plants - climate - seasons - ecology - crops - agriculture - phenology - acclimatization - botany
    Rede Wageningen
    Interaction of vernalization, photoperiod and light intensity in floral initiation of endive.
    Harrington, J.F. ; Verkerk, K. ; Doorenbos, J. - \ 1959
    Netherlands Journal of Agricultural Science 7 (1959)1. - ISSN 0028-2928 - p. 68 - 74.
    Effect of gibberellic acid on sprouting of potatoes.
    Doorenbos, J. - \ 1958
    Netherlands Journal of Agricultural Science 6 (1958)4. - ISSN 0028-2928 - p. 267 - 270.
    Oogstspreiding
    Doorenbos, J. - \ 1957
    Wageningen : Veenman - 22
    klimaatfactoren - kouderesistentie - gewassen, groeifasen - droogteresistentie - bodemfactoren - groeistadia - fenologie - plantenveredeling - planten - teelt onder bescherming - zouttolerantie - stress - temperatuurresistentie - fysische factoren - climatic factors - cold resistance - crop growth stage - drought resistance - edaphic factors - growth stages - phenology - plant breeding - plants - protected cultivation - salt tolerance - stress - temperature resistance - physical factors
    Review of the literature on dormancy in buds of woody plants
    Doorenbos, J. - \ 1953
    Wageningen : Veenman (Mededelingen van de Landbouwhogeschool te Wageningen dl. 53, verhandeling 1) - 23
    houtachtige planten - slaaptoestand - knoppen - woody plants - dormancy - buds
    The cytology of the genus cyclamen
    Haan, I. de; Doorenbos, J. - \ 1951
    Wageningen : Veenman (Mededelingen van de Landbouwhogeschool te Wageningen dl. 51, verh. 7)
    Taxonomy and nomenclature of cyclamen
    Doorenbos, J. - \ 1950
    Wageningen : Veenman (Mededelingen van de Landbouwhogeschool te Wageningen dl. 50, verhandeling 2)
    cyclamen - biologische naamgeving - taxonomie - cyclamen - biological nomenclature - taxonomy
    The history of the "Persian" cyclamen
    Doorenbos, J. - \ 1950
    Wageningen : [s.n.] (Publicatie / Laboratorium voor Tuinbouwplantenteelt no. 88) - 29
    geschiedenis - sierplanten - primulaceae - cyclamen - history - ornamental plants - primulaceae - cyclamen
    Opheusden als boomteeltcentrum
    Doorenbos, J. - \ 1950
    Wageningen University. Promotor(en): E.W. Hofstee. - Assen : Van Gorcum - 87
    houtachtige planten als sierplanten - plantenkwekerijen - agrarische geschiedenis - betuwe - gelderland - ornamental woody plants - nurseries - agricultural history - betuwe - gelderland
    The district, its social structure, its development, technical and economic aspects of Opheusden as a tree-growing centre were. discussed. The earliest information on tree growing at Opheusden was from 1656. It had always formed part of the mixed holding. Large-scale nurseries of the type found in the rest of the Netherlands never developed in Opheusden. Through the particular structure of farming and the social relationships of the community, tree growing lagged behind for a long time in Opheusden and only adapted itself with difficulty to market requirements. This difficulty was also associated with the limited variety of culture possible on the clay soil. Until 1932 times had frequently been prosperous, while the independence of the holdings made the farmers less vulnerable to set-backs. After the Second World War, in which the village had been almost entirely destroyed, a healthy spirit of enterprise had grown up among the villagers, so that the future could be viewed with optimism. This enterprise was visible in the effort put into reconstruction, in the activeness of the local association of tree-growers, the high membership of the Dutch General Inspection Service for Field Crops and the greater desire for technical education.

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