Pollen and seed morphology of Nordic Draba (Brassicaceae): phylogenetic and ecological implications

Pollen and seed morphology were examined in 54 diploid and allopolyploid populations representing 15 Nordic species of the taxonomically complex genus Draba. The pollen size was strongly correlated with chromosome number, but it was unreliable for inferring the exact ploidal level of individual populations. Five main pollen types were recognized based on sculpturing of the exine. Two populations of D. lactea had conspicuously different exine sculpturing, supporting a previous hypothesis based on molecular data that this hexaploid is polyphyletic and has been derived from various combinations of diploid species. The pollen morphological data are also consistent with the hypotheses that the 16-ploid D. corymbosa is an intersectional allopolyploid derived from the sections Draba and Chrysodraba , that the hexaploid D. cinerea is a progenitor of the decaploid D. arctica , and that D. crassifolia and D. adamsii represent isolated allopolyploid lineages. The seed size and weight were only weakly correlated with chromosome number, but showed a close relationship to habitat ecology. The largest seeds were observed in species typical of closed habitats, in which seedling establishment probably is limited by competition with mosses. The seed coat surface had a characteristic verrucate reticulum, but the differentiation among species was vague or absent. The seed size and colour, however, distinguish some species, e.g., in the D. alpina complex, which otherwise are morphologically very similar.     

Continuous production of L-alanine from fumarate in a two-stage membrane reactor

Summary L-alanine was produced continuously from fumaric acid by means of soluble aspartase and L-aspartate--decarboxylase. The two reaction steps were carried out in two membrane reactors in series at different pH and temperature. The retention of the soluble enzymes within the reactor vessels was achieved by means of ultrafiltration membranes.     

Revision and affinities ofGalium (Rubiaceae) in Madagascar

The only representatives ofRubiaceae-Rubieae in Madagascar are five species ofGalium. G. thunbergianum andG. chloroionanthum are essentially afromontane species, ± widely distributed in both the African mainland and Madagascar. The new speciesG. andringitrense andG. ankaratrense are endemic to Madagascar but show close affinities to two afromontane—afroalpine groups from the African mainland, theG. simense—G. ruwenzoriense andG. glaciale complex respectively.G. polyacanthum (new combination) exhibits certain primitive morphological traits and appears to be an old Madagascan endemic without close allies. New chromosome counts for populations from the African mainland demonstrate thatG. chloroionanthum andG. simense are 4x (x=11). Distribution patterns and origins of theGalium species in Madagascar and their relationships with African taxa are discussed.     

Effect of abscisic acid on CO2 exchange in Lemna gibba

The effects of abscisic acid (ABA) on photosynthesis, dark respiration, and photorespiration were studied in Lemna gibba L. plants. The initial concentration of ABA in the nutrient solution was 10⁻⁷M and in a few experiments, 10⁻⁶M. The cultures were grown in the same solution for time periods ranging from one hour to 12 days. Net photosynthesis, measured as CO₂ uptake by infrared gas analyser technique, was inhibited after four hours of ABA treatment and reached a minimum after four to seven days depending on the time of the year. After 12 days a substantial recovery of photosynthesis was observed. Dark respiration was significantly stimulated after two to seven days of ABA treatment but then returned to the control level. The transient effects of ABA on photosynthesis and dark respiration corresponded to the previously measured time course of [¹⁴C]-ABA uptake by Lemna . Photorespiration measured as oxygen inhibition of photosynthesis was not affected by ABA.     

Volatile constituents of Cupressus dupreziana and the sesquiterpenes of Cupressus sempervirens

Analysis of wood essential oil of Cupressus dupreziana revealed 26 components: 13 monoterpenes and 13 sesquiterpenes. The main components were carv     

Megagyrolithes ardescensis N. Gen., N. SP.,Trace fossile nouvelle du Valanginien d'Ardeche (France)

A new trace fossil corresponding to a spiral burrow is described in the Upper Valanginian of the Ardèche area (France). It seems to be restricted to marine hemipelagic facies (outer shelf and upper slope).     

In vitro adhesion of tufted oral streptococci toBacterionema matruchotii

The adhesive interaction between the ectosymbionts of the corn cob configuration (CCC), a naturally occurring bacterial consortium in human dental plaque, was studied. In vitro association was produced in mixed cultures consisting ofBacterionema matruchotii and streptococci resemblingStreptococcus sanguis previously isolated from human CCC. Phase-contrast, selective immunofluorescence, and scanning electron microscopy showed that in this aggregative system, a tuftlike polar structure typical of the coccal epibiont mediated binding to the core filament. This aggregative model provides evidence that a specialized structure on the cell surface of epiphytic organisms may participate in interbacterial adherence.     

Réflexions critiques sur l'écologieet la systématique des Lingules actuelles et fossiles

New topics on ecology and systematics of recent and fossil Lingulids lead to an obvious revision of our knowledges on this zoological group. At first, the recent species need systematics and taxonomy on the bases of new described specific criteria (as, morphology of deltidial areas, muscle disposition); the results are briefly indicated. But, in fossil species, disorder and disparity of used characteristics are emphasized.The general conceiving on ecology of Lingulids are reviewed and discussed, especially on bathymetry and salinity; sediment and oxygenation conditions; taphocoenosis and lingulid «communities. On recent species, all these points are also studied, especially some ecological requirements (salinity, bathymetry, grain size), and mechanism of burrowing ability, burrow living positions in the sediments, as shell preservations after death and fossilization, to facilitate the paleobiotope interpretations. Recent animals are euryhalin, surviving at salinities from about 13 to 42‰; they could be considered as well adapted to waters with strong salinity fluctuations. They show preference to fine sand bottoms (lowest particle size about 40–60 μm). Their bathymetric distribution occurs between 0 and about 500 m (Lingula especially between 5–50 m; Glottidia 15–70 m). The isotherms 8–10°C seem to restrict their geographical and bathymetric distribution.Therefore, some post-palaeozoic lingulid bedsare studied or redescribed on the bases of the above discussed characteristics, and new interpretations on the environmental situation are given (Trias of Vosges Mountains; Oligocene from Japan; Eocene of London Basin). More caution must be used in study of fossil Lingulids that are not especially animals living in infralittoral bottoms with low salinity and deficient oxygenation, as generally accepted.