Factorial correspondence analysis of oligochaeta communities according to eutrophication level

In 1976, 31 sediment cores were taken between the 50 and 310 m isobaths in Lake Geneva (Switzerland). Communities of Tubificidae and Lumbriculidae were used to characterize sampling stations. These results were analysed with factorial correspondence analysis. Differences in worm communities, due to microdistribution and seasonal variation inside location, were small compared with differences between sampling stations. Locations from a previous study classified as polluted and not polluted by chemical and biological criteria were entered into the analysis as reference stations. Distance on the factorial plots between studied and reference stations indicated their pollution level. Positions of worm species around sampling locations allowed these to be classified as indicators of pollution level. Since 1962 pollution has modified worm communities between the 150 and 310 m isobaths. Deep water stations, where oxygen is low, have a fauna similar to shallow water stations near the sewage outfall of Vidy. Tubifex tubifex is present in the most polluted conditions. Stylodrilus heringianus is an indicator of unpolluted conditions. Potamothrix vejdovskyi, P. heuscheri and P. hammoniensis can be used to indicate a gradient of increasing pollution.     

Golgi fractions from livers of control and ethanol-intoxicated rats. Enzymic and morphologic properties following rapid isolation

Following rapid isolation, it has been found that Golgi apparatus from ethanol-intoxicated animals contain high levels of galactosyltransferase but also detectable glucose-6-phosphatase and microsomal esterase, as well as 5′-nucleotidase activity. In experiments carried out in parallel on littermate animals but without intoxication, similar recoveries and specific activities of the four enzymes were observed. Morphologic analysis of Golgi fractions isolated from control animals demonstrated no striking morphologic difference to those from the ethanol-intoxicated animals. Indeed, using galloyl glucoselead staining techniques to mark the lipoprotein particles in situ, it was found that all Golgi apparatus of hepatocytes from control animals were marked by very low density lipoprotein particles. It is therefore concluded that within the limits of the present analyses, Golgi fractions isolated from control animals are as valid as those isolated from ethanol-intoxicated rats.     

Lowering of water level and algal biomass in Lake Kinneret

An unusual situation accompanied the rapid lowering of the lake level which took place during the period 1972–1975 as a result of low amounts of precipitation. The dominant alga of the lake (Peridinium cinctum f. westii), usually blooming from January to May, developed two months later than in previous years. The small and short peak of diatoms and green algae, which used to appear in January, extended until march, delaying the appearance of the winter bloom. The replacement of the non-grazed Peridinium having a high C : P ratio by the actively grazed diatoms and green algae having a low C : P ratio led to a substantial decrease of algal standing crop in the water. The chain of limnological events leading to the biological modification is investigated and its bearing on water quality is discussed.     

Intra- and Inter-Plant Level Correlations among Floral Traits in <Emphasis Type="Italic">Iris Gracilipes</Emphasis> (Iridaceae)

Although the sizes of individual flowers within one plant vary, few studies to date have investigated correlations among floral traits at the intra-plant level. Variations of the pleiotropic genes or linkage disequilibrium of genes, those have been said to create larger correlations between some combinations of traits than others at the inter-plant level, cannot predict intra-plant level correlations. In this study, correlations between several combinations of floral traits, including the number and volume of pollen grains and ovules, were investigated at both intra- and inter-plant levels in Iris gracilipes. The pattern of intra-plant level correlations was similar to that of inter-plant level correlations with some exceptions; correlations between functionally related traits tended to be larger than others at both levels. For example, correlations between sepal and petal size, and between petaloid style and filament length were large at both levels. This may be explained by the genetic and the developmental relationships between some combinations of traits, rather than by (co)variations of the peculiar properties of the individual plants such as genetic variations. Co-ordinat`ing editor: X. Pico     

Crown allometry and growing space efficiency of Norway spruce (Picea abies [L.] Karst.) and European beech (Fagus sylvatica L.) in pure and mixed stands

In pure and mixed stands of Norway spruce ( Picea abies [L.] Karst.) and European beech ( Fagus sylvatica L.) we have analyzed crown allometry and growing space efficiency at the tree level and have scaled this from tree level to stand level production. Allometry is quantified by the ratio A between the relative growth rates of laterally and vertically oriented tree dimensions. Efficiency parameters, EOC for efficiency in space occupation, EEX for efficiency in space exploitation, and EBI for efficiency in biomass investment, were evaluated, based on quantity and quality of growing space and were measured using crown size and competition index. The evaluation reveals why pure stands of spruce are preferred by foresters, even though the natural vegetation would be dominated by beech. Spruce occupies its share of resources intensively by means of tightly packed pillar-like crowns, whereas beech seizes resources extensively by means of a multi-layered, veil-like canopy. With a given relative biomass increment, beech achieves a 57 % higher increment in crown projection area and a 127 % higher increment in height due to its particular capacity of lateral and vertical expansion. Beech trees are approximately 60 % more efficient in space occupation than spruce trees, however, on average, they are about 70 % less efficient in space exploitation. As a vertical fast growing tree, spruce is efficient in space exploitation under constant conditions, but far more susceptible to disturbances and less well equipped to overcome them when compared with beech. Beech is weaker in terms of space exploitation, while being superior in space occupation, where it encircles competitors and fills gaps after disturbances, which is a successful long-term strategy. A mixture of the two species reduces stand level production by 24 % in comparison to a pure spruce stand, however, when considering enhanced stabilization of the whole stand and risk distribution in the long term, the mixed stand may exceed the production level of pure spruce stands. EEX reflects a strong ontogenetic drift and competition effect that should be considered when scaling from tree to stand level production.     

A general description of detachment for multidimensional modelling of biofilms

A general method for describing biomass detachment in multidimensional biofilm modelling is introduced. Biomass losses from processes acting on the entire surface of the biofilm, such as erosion, are modelled using a continuous detachment speed function F(det). Discrete detachment events, i.e. sloughing, are implicitly derived from simulations. The method is flexible to allow F(det) to take several forms, including expressions dependent on any state variables such as the local biofilm density. This methodology for biomass detachment was integrated with multidimensional (2D and 3D) particle-based multispecies biofilm models by using a novel application of the level set method. Application of the method is illustrated by trends in the dynamics of biofilms structure and activity derived from simulations performed on a simple model considering uniform biomass (case study I) and a model discriminating biomass composition in heterotrophic active mass, extracellular polymeric substances (EPS) and inert mass (case study II). Results from case study I demonstrate the effect of applied detachment forces as a fundamental factor influencing steady-state biofilm activity and structure. Trends from experimental observations reported in literature were correctly described. For example, simulation results indicated that biomass sloughing is reduced when erosion forces are increased. Case study II illustrates the application of the detachment methodology to systems with non-uniform biomass composition. Simulations carried out at different bulk concentrations of substrate show changes in biofilm structure (in terms of shape, density and spatial distribution of biomass components) and activity (in terms of oxygen and substrate consumption) as a consequence of either oxygen-limited or substrate-limited growth.     

Positive and negative effects of riverine input on the estuarine green alga <Emphasis Type="Italic">Ulva intestinalis</Emphasis> (syn. <Emphasis Type="Italic">Enteromorpha intestinalis</Emphasis>) (Linneaus)

An approach based on a digital elevation model (DEM) was used to untangle the confounding effects of long-term water-level fluctuations and increasing human population on the cover of emergent vegetation in Cootes Paradise Marsh, a degraded coastal wetland in Lake Ontario, Canada. Data for 20 observations between 1934 and 1993 were used in the analysis. First, we calculated the inundated area based on the DEM, a derived measurement that reflected the bathymetry of the marsh and the mean water level for a particular year. Then Mantel correlations and regression analyses were used to analyze the relationships between emergent cover and corresponding water level, inundated area, and human population, respectively. Results of the simple and partial correlations indicated that areal change of emergent plants was significantly correlated with inundated area after controlling for the effect of water level fluctuation; however, there was no significant correlation between emergent cover and water level after controlling for inundated area. This is an important consideration when multiple sites from the same Great Lake are compared since the same water level may correspond to vastly different inundated areas for different marshes. Changes in emergent cover were also significantly correlated with human population after controlling for water level effects. Altogether, inundated area explained 83.1% of the variation, human population explained 4.2%, and the interaction between population and inundated area explained an additional 4.3% of the remaining variation in areal emergent cover. This indicates that the synergistic effect of high water level (expressed as inundated area) and increased human population induced greater detrimental impact on the emergent plants than did either stressor alone.     

Regeneration of androgenic embryos in apple (<Emphasis Type="Italic">Malus x domestica</Emphasis> Brokh.) <Emphasis Type="Italic">via</Emphasis> anther and microspore culture

Based on optimized protocols for anther and microspore culture in apple (Malus x domestica Borkh.), the regeneration phase and the efficiency of the processes in general were compared by using the same androgenic material of two experimental years. Microspore culture resulted in an increase in embryo induction depending on the genotype (Höfer 2004), however anther culture was superior to microspore culture in the total number of regenerated plants. The regeneration process in anther and microspore culture is similar. Two developmental pathways were observed: 1) secondary embryogenesis followed by adventitious shoot formation and 2) direct adventitious shoot formation from primary embryos. Induction and regeneration processes are delayed in microspore culture as compared with anther culture. The reasons for the reduced regeneration efficiency in microspore culture are discussed.     

No-effect level in the mutagenic activity of the drug cyproterone acetate in rat liver. Part I. Single dose treatment

The anti-androgen and progestagen cyproterone acetate (CPA) is known to cause liver tumors in rats. The drug has been identified recently as a mutagen in the liver of female transgenic lambdalacI (Big Blue) rats at high doses after an expression time of 6 weeks. A dose of 50 mg CPA/kg BW, however, did not increase the mutation frequency (MF) of controls indicating a no-effect level of mutagenicity [Carcinogenesis 19 (1998) 241]. The present study was performed to assess the existence of a no-effect level of mutagenicity. In order to figure out conditions of maximum response, the time course of the MF was determined after administration of a single dose of 100 mg CPA/kg BW to female Big Blue rats. The MF showed a strong initial rise to a maximum 2 weeks after CPA administration accompanied by a corresponding increase of cell proliferation and of DNA adduct levels. Thereafter, the MF decreased within further 2 weeks to one third of the maximum level which was maintained for another 4 weeks. The DNA adduct levels decreased only by 15% during this time period suggesting that mutated hepatocytes were eliminated predominantly. A dose dependence curve determined at a fixation time of 2 weeks revealed a no-effect level of 5 mg CPA/kg BW for mutagenicity. In conclusion, our findings indicate that the length of the observation period may be a critical determinant for the outcome of a mutagenesis study in rat liver. Furthermore, the existence of a no-effect level for the mutagenicity of CPA in rat liver was confirmed. However, it has to be clarified whether the dose of 5 mg CPA/kg BW corresponding to the "transient" type of mutations or the previous dose of 50 mg CPA/kg BW related to a "permanent" type of mutations is more relevant for the assessment of the genotoxic risk.