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  • 1
    ISSN: 1432-2048
    Keywords: Daucus ; Embryogenic potential ; Gene expression ; mRNA ; Somatic embryogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Somatic embryogenesis can be synchronized by enriching carrot (Daucus carota L.) suspension cultures for small, dense clusters of cells termed proembryogenic masses (PEMs). Gene-expression programs of PEMs were compared with those of embryonic and mature tissues by in-vitro translation of representative mRNA populations and by nucleic-acid hybridization. Analysis of invitro-translated polypeptides by two-dimensional polyacrylamide gel electrophoresis revealed striking similarities between the mRNA populations of PEM and torpedo-stage embryos; substantial differences, however, were observed when in-vitro translation products of PEMs and torpedo embryos were compared with those of hypocotyls and leaves. Northern blots of RNA isolated from PEMs, staged embryos, and mature carrot tissues were hybridized with cDNA probes for Dc3, Dc5 and Dc13; these cDNA recombinants represent mRNAs that are regulated during carrot somatic embryogenesis. The pattern of expression of these embryo-regulated transcripts was similar in PEMs and somatic embryos but differed in other carrot tissues. These results indicate that many of the molecular processes of embryogenesis are already established in PEMs in the presence of auxin. Additional experiments indicate the utility of Dc3 as a molecular marker for the acquisition of embryogenic potential.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1570-7458
    Keywords: simulation model ; temperature sum ; phenology ; juvenile-hormone mimic ; Insect Growth Regulator ; Integrated Pest Management ; apple orchard ; Pandemis heparana ; Adoxophyes orana ; Tortricidae ; leafrollers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Résumé Le contrôle des Tordeuses par les régulateurs de croissance d'Insectes (IGR), à activité d'hormone juvénile, est un progrès majeur dans la recherche pour la lutte intégrée contre les ennemis des vergers de pommiers. L'IGR appliqué lors de l'apparition du dernier stade larvaire des Tordeuses, perturbe ainsi la métamorphose ultérieure. Afin de prévoir le moment d'apparition des différents stades, et plus particulièrement du dernier stade larvaire, des modèles de simulation du développement de Pandemis heparana (Denn. et Schiff.) et Adoxophyes orana (F.v.R.) ont été élaborés à partir d'expériences et en se basant sur des résultats de la littérature. Le modèle est basé sur l'examen de la variable d'état, la température étant la variable discriminante suivie. Les courbes simulées d'apparition des larves de dernier stade, des nymphes et des papillons correspondent aux observations faites sur les larves récoltées dans la nature et élevées jusqu'au stade adulte dans un insectarium en plein air. Le taux de capture dans les pièges à phéromone présente un retard par rapport aux courbes calculées et observées pour l'éclosion des nymphes. Différentes causes peuvent être attribuées à cette différence, mais l'influence d'aucune d'elles n'a été étudiée. Afin de déterminer si le moment de l'application d'IGR peut être lié à une somme de températures, les courbes d'apparition des larves de dernier stade ont été étudiées en relation avec les sommes de températures portant sur plusieurs années. Les observations concernant l'apparition des larves de dernier stade ne couvrant que 2 années, des courbes simulées ont été utilisées à cet effet. L'emploid de la relation liant le moment de l'apparition à la somme des températures permet de n'avoir à calculer que les sommes de températures pour déterminer le moment opportun de l'application des IGR.
    Notes: Abstract Control of leafrollers using Insect Growth Regulators with juvenile-hormone acitivity (IGR) is a major issue in research on Integrated Pest Management in apple orchards. The IGR is applied at the time of emergence of the last-larval instar of leafrollers, thus causing a disturbance of metamorphosis. Simulation models on the development of Pandemis heparana (Denn. et Schiff.) and Adoxophyes orana (F.v.R.) were developed, partly on the basis of experiments, partly on data from literature, to predict the time of emergence of the various stages, particularly of the last-larval instar and the pupa. The models use the state-variable approach, and include only temperature as a driving variable. Simulated curves of emergence of last-instar larvae, pupae and moths corresponded well with observations on field-collected larvae, reared to adult stage in an outdoor insectary. The curves of pheromone trap catches showed a delay relative to the calculated and observed curves for the eclosion of pupae. To investigate whether the time of IGR application could be related to a temperature sum, the relation between emergence curves of last-instar larvae and temperature sums was studied for several years. For this purpose simulated curves were used, because observations on emergence of last-instar covered only a few years.
    Type of Medium: Electronic Resource
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