Das Pyrenoid als Ort der Chlorophyllbildung im Algenchloroplasten

Zusammenfassung In der Pyrenoidstärke von Mesotaenium caldariorum konnte durch Messung der Doppelbrechungsdispersion Chlorophyll nachgewiesen werden. Das Chlorophyll, bei dem es sich wahrscheinlich um Chlorophyll a handelt, ist in der Pyrenoidstärke in ähnlicher Weise geordnet eingelagert wie im Chloroplasten. Das am Pyrenoid gebildete Chlorophyll gelangt mit der Pyrenoidstärke in das Stroma des Chloroplasten, die Pyrenoidstärke wird dadurch zur Stromastärke. Die Stärke kommt im Stroma allmählich zur Auflösung, wodurch das Chlorophyll an den Ort seiner Wirkung gelangt.Meinem Vater und Lehrer Hans Wartenberg zum 65. Geburstag gewidmet.     

Lichtbedingte pH-Erniedrigung in einem Chloroplasten-Kompartiment als Ursache der enzymatischen Violaxanthin-→ Zeaxanthin-Umwandlung; Beziehungen zur Photophosphorylierung

Ohne Zusammenfassung

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Light dependent decrease of the pH-value in a chloroplast compartment causing the enzymatic interconversion of violaxanthin to zeaxanthin; relations to photophosphorylation

     

Das Pyrenoid als Ort der Chlorophyllbildung im Algenchloroplasten. II

Die Pyrenoidstärke von Mesotaenium caldariorum enthält Chlorophyll mit Extinktionsmaxima bei λ = 435 und 675 nm. Zugabe von 5-Aminolävulinsäure (ALA, 10^?3 M/L) erhöht die Chlorophyllkonzentration in der Pyrenoidstärke und mit zeitlicher Verzögerung auch im Chloroplastenraum. Am Pyrenoid tritt das Konzentrationsmaximum neun Stunden nach Zugabe der ALA auf, im Chloroplastenraum erst nach 60 Stunden. Nach Behandlung mit ¹⁴C-ALA ist Radioaktivität mikroautoradiographisch zunächst nur am Pyrenoid (Maximum nach neun Stunden) nachzuweisen, im Chloroplastenraum erst zeitlich verzögert (Maximum nach 60 Stunden). 84 Stunden nach Zugabe der ALA hat sich die Radioaktivität gleichmäßig über den Chloroplasten verteilt.     

Tchernobyl : le vrai, le probable et le faux

The Japanese earthquake and tsunami drew attention worldwide to nuclear power plant accidents and associated health risks. Since Chernobyl 25 years ago, several studies were published and we now have precise information concerning the long-term health of the population living near nuclear power plants and also in different European countries. The authors hope to bring some answers to the key questions from the public concerning radioactive units used and their significance, the evaluation of the number of radio-induced cancers within the different countries of Europe, other eventual health effects and the problem of possible congenital anomalies. Finally, French public perception on nuclear risk is examined and the feedback of the Japanese experience is evoked.     

L'évolution parallèle des Juraphyllitidae euroboréaux et téthysiens au Pliensbachien: le rôle des contraintes internes et externes

Au Pliensbachien, un trend morphologique se developpe chez les Tragophyllocerassimpliquant un mécanisme hétérochronique (paedomorphose par néoténie) pour I'acquisition d'une morphologie suboxycône. Ce changement morphologique majeurest concomitant avecl'ingression de ces formes dans les mers de plateforme euroboréale ob la compétition inter-taxons est forte. Cette option morphofonctionnelle et évolutive, canalisée essentiellement par des contraintes externes étant amorcée, le genre va I'exploiter dans la mesure de ses possibilités (potentialités intrinsèques) en perfectionnant son oxycônie. Au contraire dans les mers téthysiennes, les Juraphyllites ne montrent pas d'évolution pour la morphologie de la coquille; celle-ci reste subplatycône durant tout le Lias moyen et il n'y a pas de changements environnementaux majeurs (milieux tamponnés). En outre la prolifération d'ornementations plus grossières, aussi bien chez les Juraphyllites que chez les Tragopbylloceras, correspond probablement à une meilleure exploitation des biomes d'Europe du NW et de la Téthys à une période bien précise qui est le Carixien moyen. Ce développement d'ornementation similaire chez des taxons partageant un héritage évolutif commun mais séparés paléogéographiquement, évoque le rôle prépondérant des contraintes internes. Ainsi l'évolution des Juraphyllites des Tragophyllocerasau Lias moyen paraît donc ètre un exemple de parallèlisme au sens strict du terme.□Évolution, hétérochronies, Juraphyllitidae, Lias, ontogenèse, Paléogéographie. A morphological trend in the Pliensbachian Tragophyllocerns involves a heterochronic process (paedomorphosis by neoteny) to acquire a suboxycone morphology. This major morphological change is concomitant with the ‘ingression’ of Tragophylloceras in the Euroboreal platform seas, where competition between taxa was strong. This functional-morphological and evolutionary option is mainly canalized by extrinsic constraints. Exploring these possibilities, Tragophylloceras then exploits and improves the oxycone option. By contrast, in the Tethyan seas, Juraphyllites shows no change in shell coiling; it stays subplatycone during all the Pliensbachian. There is no major environmental change. Moreover, the proliferation of coarser ornamentation in Juraphyllitesand Tragophylloceras probably corresponds to a better exploitation of the Euroboreal and Tethyan marine habitats during the Middle Carixian. The development of similar ornamentation in palaeogeographically separate taxa with a common evolutionary origin is mainly canalized by intrinsic constraints. The evolution of Juraphyllites and Tragophylloceras appears to be a good example of parallelism sensu stricto. □ Evolution, heterochrony, Juraphyllitidae, Lios, ontogeny, palaeogeography.     

Isolement d'une alcool déshydrogénase chez Rhizobium et rôle dans le métabolisme indolique

Rhizabium meliloti contains an alcohol dehydrogenase (E.C.1.1.1.1.) which can be isolated by breaking the cells. This soluble enzyme was purified 16.1-fold by fractional precipitations with ammonium sulfate followed by gel filtration on Sephadex. The activity of the enzyme was tested with various aldehydes as substrates in the presence of NADH. Indole-3-acetaldehyde (IAAld) can be reduced to tryptophol (Tr-ol), and the optimal pH for this reaction is ca. 6.5. The reaction can be reversed, and Tr-ol is oxidised in the presence of NAD, but is was found that the yield was very poor; the optimal pH was ca. 8.6. This alcohol dehydrogenase is responsible for Tr-ol formation in Rhizobium, but under our experimental conditions tryptophol cannot really be considered as a precursor of IAAld and indole-3-acetic acid.     

Mouvements nycthéméraux foliaires chez le Cassia fasciculata inversé dans le champ de la pesanteur

Nyctinastic movements of leaves of Cassia fasciculata inversed in the field of gravity. Plants of Cassia fasciculata Michx, were grown under controlled conditions with a diurnal rhythm of 14 h light and 10 h dark. The nyctinastic movements performed by the leaves were observed by time lapse photography, on plants inverted in the field of gravity and compared to those recorded on plants remaining in natural position. The movements were observed on leaves from which the petiolar gland has been removed as well as on leaves in which it has been preserved. In plants inverted in the field of gravity, the leaflet movements were not disturbed but the petiolar ones were opposite to those observed on plants in natural position and smaller in amplitude (52 and 15 degrees difference between maximum and minimum positions respectively). This was not influenced by the removal of the petiolar gland. Inverting plants greatly shortened duration of closing and time spent maximally closed while increasing both duration of opening and time spent maximally opened. Removal of the petiolar gland did not influence the opening-closing schedule of the plants in normal position but in inverted plants it caused marked changes in this schedule. These results are discussed in connection with what is known about IAA. K⁺ and amyloplasts and their role in causing changes in pulvinus turgor.     

Corrélations de croissance entre le mycélium et les rhizomorphes chez le Sphaerostilbe repens

Correlation of Growth between Mycelium and Rhizomorphs in Sphaerostilbe repens In Sphaerostilbe repens Berkeley and Broome, cultured on a solid medium in Petri dishes, growth of mycelium and chizomorphs depends on the thickness of the culture medium underlying the thallus. On shallow layers of agar medium, aggregated units were fewer and rhizomorph growth reduced. Vegetative mycelium which starts growth earlier than rhizomorphs contributed to inhibit the development of these latter. On deep layers of substrate, rhizomorphs were numerous, elongated rapidly, and eventually inhibited undifferentiated mycelium. – There was no evidence for the involvement of any inhibitor substance diffusing into culture medium or located in the thallus. Development of aerial mycelium and rhizomorphs, could, on the contrary, be interpreted as nutritional competition between these two parts of the colony.     

microRNAs – kleine Moleküle ganz groß

microRNAs, regulators of complex phenotypes microRNAs (miRNAs) are small, non‐coding RNAs that regulate a number of biological processes, including development. Due to their mode of action some miRNAs are also causally involved in diseases like cancer. miRNAs bind base‐complementary mRNAs and lead to either degradation of the bound mRNAs or translational repression. Both result in decreased protein levels of the particular target. miRNA selectivity is governed via a very short, just six to seven nucleotides long, ”seed" sequence which is likely to exist in many mRNAs. miRNAs are, therefore, believed to target a larger number of mRNAs, each, leading to the concerted regulation of functionally connected proteins and to thus substantially contribute to phenotypes. We have performed several screenings which suggest that, indeed, many miRNAs regulate a larger number of proteins. However, we also showed that the proteins we tested were regulated by a larger number of miRNAs each. The complexity of miRNA regulation opens new avenues towards reaching a molecular understanding of disease phenotypes via the integrated consideration of coordinated regulations.     

Beiträge zur Kenntnis der Zusammensetzung Fetter Öle in verschiedenen Teilen einer Pflanze

Ohne ZusammenfassungMit 1 Textabbildung.Dissertation der Philosophischen Fakultät der Universität Leipzig.     

Rôle des polyphénols dans la croissance. Définition ďun modèle expérimental chez Lycopersicum esculentum

Using young plants of Lycopersicum esculentum Mill., we attempt to define a system for a new evaluation of the physiological role of polyphenols, particularly of their regulating properties on growth and development, Exogenously supplied qoinic acid causes an important increase of the phenolic content and a reduced growth of the plants. The decrease in size is proportional to the stimulation of the phenolic pool and is equally obtained using other precursors of aromatic compounds like phenylalanine and cinnamic acid. Non-precursors of polyphenols structurally related to quinic acid are ineffective. It appears from these data that polyphenol levels and growth could be related in tomato plant and that this material would be convenient for studies on interactions between growth and polyphenols.