Does nectar reward affect rarity and extinction probabilities of orchid species? An assessment using historical records from Belgium and the Netherlands

The long-term persistence of plant populations may partly depend on pollination processes and seed production. The exact role of pollination in determining plant population viability still remains largely unclear. Orchid species have often been shown to be pollinator limited. Especially, non-rewarding species are characterized by infrequent pollinator visits and low seed set. Therefore, it can be hypothesized that, if overall population fitness of orchid species is influenced by seed production, non-rewarding species should be more prone to local extinction than rewarding species. To study the importance of nectar reward on orchid persistence, we collected historical records about the distribution of 32 orchid species in Flanders (Belgium) and 37 orchid species in the Netherlands. For both regions, present distribution patterns were compared with historical data. Between 1930 (Flanders) or 1950 (the Netherlands) and 2000, 26 (81%) species showed decreases in distribution range in Flanders, eight of which had gone extinct, whereas 29 (78%) species showed declines in distribution area in the Netherlands, five of which went extinct. Contrary to previously reported results, orchid distribution patterns were not related to nectar reward. There was also no significant relationship between nectar reward and extinction for both regions. Orchids typically occurring in wet grasslands and heathlands suffered greater losses than orchids typically confined to forest habitats or calcareous grasslands. We conclude that the production of nectar does not represent a safeguard for local extinction of orchid species. Habitat loss and other deterministic threats associated with habitat fragmentation and deterioration are more important determinants of orchid persistence.     

Horseradish peroxidase-catalyzed cross-linking of feruloylated arabinoxylans with beta-casein

Heterologous conjugates of wheat arabinoxylan and beta-casein were prepared via enzymatic cross-linking, using sequential addition of the arabinoxylan to a mixture of beta-casein, peroxidase, and hydrogen peroxide. The maximal formation of adducts between the beta-casein and the feruloylated arabinoxylan was reached at a protein-to-arabinoxylan ratio of 10:1, in combination with a molar ratio hydrogen peroxide to substrate of 2:1 and a molar protein-to-enzyme ratio between 10(2) and 10(4). The protein-arabinoxylan adducts were separated from the arabinoxylan homopolymers by size exclusion and anion exchange chromatography. The molar ratio protein:arabinoxylan in the purified conjugates varied between 0.1 and 5.6. This is the first report on the large-scale enzymatic preparation of heterologous protein-arabinoxylan conjugates.     

Detecting interaction(s) and assessing the impact of component subsets in a chemical mixture using fixed-ratio mixture ray designs

An important environmental and regulatory issue is the protection of human health from potential adverse effects of cumulative exposure to multiple chemicals. Earlier literature suggested restricting inference to specific fixed-ratio rays of interest. Based on appropriate definitions of additivity, single chemical data are used to predict the relationship among the chemicals under the zero-interaction case. Parametric comparisons between the additivity model and the model fit along the fixed-ratio ray(s) are used to detect departure from additivity. Collection of data along reduced fixed-ratio rays, where subsets of chemicals of interest are removed from the mixture and the remaining compounds are at the same relative ratios as considered in the full ray, allow researchers to make inference about the effect of the removed chemicals. Methods for fitting simultaneous confidence bands about the difference between the best fitting model and the model predicted under additivity are developed to identify regions along the rays where significant interactions occur. This general approach is termed the “single chemicals required” (SCR) method of analysis. A second approach, termed “single chemicals not required” (SCNR) method of analysis, is based on underlying assumptions about the parameterization of the response surface. Under general assumptions, polynomial terms for models fit along fixed-ratio rays are associated with interaction terms. Consideration is given to the case where only data along the mixture rays are available. Tests of hypotheses, which consider interactions due to subsets of chemicals, are also developed.     

Removal of Formic Acid from Wastewater using Three-Phase Three-Dimensional Electrode Reactor

A new electrochemical reactor, three-phase three-dimensional electrode reactor, was designed and used to investigate theremoval of formic acid from simulated wastewater. The experimental results were assessed in term of Chemical OxygenDemand (COD) removal efficiency. The results showed that the three-phase three-dimensional electrodes could effectively removeformic acid. Its COD removal efficiency was much higher than those of two-dimensional electrodes and common three-dimensionalelectrodes, respectively. The COD removal efficiency of the three-phase three-dimensional electrodes using air as a spargegas increased 13.5% relative to that using nitrogen as a spargegas. The observation indicated that the sparged air in the three-phase three-dimensional electrodes not only participated insome physical processes but also played an important role in electrochemical reactions to assist COD removal.     

Reacidification Effects on Water Chemistry and Plankton in a Limed Lake in Sweden

Water chemistry and plankton has been monitored in three Lakes in Tyresta National park SE of Stockholm since 1977. Liming operations started in Lake Långsjön and Lake Trehörningen in 1978 and were repeated every 3–5 years, while Lake Årsjön is an unlimed reference Lake. During 1991–1999, the annual pH median in Lake Långsjön and Lake Årsjön ranged between 6.6–7.1 and 5.2–5.8, respectively, and the composition of phyto- and zooplankton in these lakes did not change markedly. After a final treatment in 1991, the liming of Lake Trehörningen was terminated intentionally. As a result, pH decreased from an annual median 7.1 in 1991, to 6.1 in 1999 (5.8 in 1998). Total organic carbon (TOC) did not change markedly during this period, while the levels of calcium decreased. Metals, known to be influenced by acidification, especially cadmium, manganese and aluminium (Al), increased. The labile-inorganic forms of Al also reached higher levels, especially in 1998. Following the decreasing pH, the total number of phytoplankton taxa decreased by ca 40%. Among zooplankton, the cladocerans Holopedium gibberum, Diaphanosoma brachyurum and Daphnia longispina, common during the limed period, became rare.     

BRAC initiative towards promoting gender and social equity in health: a longitudinal study of child growth in Matlab, Bangladesh

OBJECTIVE: To explore the effect of BRAC (formerly Bangladesh Rural Advancement Committee) initiatives towards promoting gender and social equity in health among children of poor mothers who are BRAC members. DESIGN: A cohort of 576 children from the prospective study of a BRAC- International Centre for Diarrhoeal Disease Research, Bangladesh joint research project was analysed. Data were collected three times during 1995-1996 with approximately 4-month intervals. Stunting, defined as height-for-age below minus two standard deviations from the reference median, was the outcome health measure. The study children were stratified into three groups according to their mother's social and BRAC membership status: poor and BRAC member (BM), poor non-member (TG) and non-poor non-member (NTG). SETTING: Matlab, rural area of Bangladesh. SUBJECTS: Children aged 6-72 months. RESULTS: The overall prevalence of stunting was 76%; the highest prevalence was found among TG (84.6%) children and no significant difference was observed between BM and NTG children (67.3% and 69.4%, respectively). In all groups, a significantly larger proportion of girls was stunted compared with boys in the first round. Group-level analysis showed that stunting decreased among all children except BM boys at the end of third round, with the largest decline among BM girls. In contrast, stunting prevalence increased among BM boys. A similar trend was found in the individual-level analysis, where a larger proportion of BM girls recovered from stunting compared with other groups and no recovery was observed among BM boys. At the end of the third round, the nutritional status of BM girls was almost equal to that of the BM boys, while gender inequity remained large among TG and NTG children. CONCLUSION: The BRAC initiative appeared to contribute to a significant equity gain in health for girls, as well as to decreased differences in ill health between the poor and the non-poor.     

Sinapate dehydrodimers and sinapate-ferulate heterodimers in cereal dietary fiber

Two 8-8-coupled sinapic acid dehydrodimers and at least three sinapate-ferulate heterodimers have been identified as saponification products from different insoluble and soluble cereal grain dietary fibers. The two 8-8-disinapates were authenticated by comparison of their GC retention times and mass spectra with authentic dehydrodimers synthesized from methyl or ethyl sinapate using two different single-electron metal oxidant systems. The highest amounts (481 microg/g) were found in wild rice insoluble dietary fiber. Model reactions showed that it is unlikely that the dehydrodisinapates detected are artifacts formed from free sinapic acid during the saponification procedure. The dehydrodisinapates presumably derive from radical coupling of sinapate-polymer esters in the cell wall; the radical coupling origin is further confirmed by finding 8-8 and 8-5 (and possibly 8-O-4) sinapate-ferulate cross-products. Sinapates therefore appear to have an analogous role to ferulates in cross-linking polysaccharides in cereal grains and presumably grass cell walls in general.     

Irrigation with plant extracts in ecofarming increases biomass production and mineral and organic nitrogen content of plants

Seedlings of alfalfa, rape, spinach, and wheat, potted on sandy soil, were irrigated with an aqueous extract of pea shoot (PE, 9.84 g dry weight l^–1) or a solution of Ca, K, Mg, P, and NO₃‐N salts (SS) in a concentration similar to that in PE, for 31–48 days. In comparison to water‐irrigated controls, both SS and PE treated plants showed nearly equal increases in shoot dry weight (29–40 %), whereas PE‐treated plants had higher fresh weights (38–84 %) due to increased succulence. Treatment with SS did not enhance, but sometimes even reduce, the concentrations of Ca, K, Mg, and several trace elements in shoot tissues. In contrast, PE‐treated plants had higher Ca, K, Mg, and organic N, but lower As and Ni contents and were thus of higher nutritive value. Reduced contents of metals in plant tissue correlated with their reduced solubility in the soil solution, which was not due to changes in pH. Fertilizer components such as K and Mg (metals of lower exchange intensity) were incorporated into the soil to release Ca, Sr, and Ba (metals of higher exchange intensity) and reduce the solubility of most trace elements and metal‐complexing humic substances. In addition, application of Ca precipitated heavy metals and humic complexes directly from the soil solution. This effect was partially overcome by PE. Its carboxylic acids could act as phytochelators of metal ions and as mobilizers of the highly diffusible humic substances which carry metals to roots. It is concluded that continuous PE application replaces the quantities of Ca, K, Mg, P, and organic N, but not of NO₃‐N consumed during plant growth. Using PE does not add any relevant quantities of toxic metals to the plant‐soil system.     

Mathematische Auswertung von Dichtegradienten zur Molekulargewichtsbestimmung von DNS mit Hilfe der EDV 1

Zusammenfassung Es wird ein EDV-Programm für den HP 9810 A zur rationellen Auswertung des Sedimentationsverhaltens von DNS im alkalischen Saccharosegradienten, insbesondere zur Berechnung wichtiger Kennzahlen für das Molekulargewicht und für die Bruchhäufigkeiten von DNS beschrieben. Voraussetzung dafür sind Radioaktivitätsprofile und Eichung des Gradienten mit Hilfe von Standard-DNS ausgehend von der Approximationsformel vonBurgi undHershey (1963).Im Programm hat der ExponentK den in unseren Eichläufen ermittelten Wert 0,353.Die Ausgabe der Daten und der Ergebnisse erfolgt als Ausdruck über eine rechnergesteuerte Schreibmaschine. Außerdem ist die graphische Wiedergabe über den rechnergesteuertenx- y-Schreiber vorgesehen. Der graphische Teil des Programms erlaubt es, die Versuchsvarianten (Gradienten) in quantitativer Relation mit unterschiedlicher Normierung auszuwerten, wie es speziell in Experimenten zur DNS-Reparatur notwendig ist.

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Computer program to analyse the molecular weight of DNA from sedimentation profiles

Summary A computer programm for the desk-top calculator HP 9810A to analyse sedimentation profiles and to calculate the weight average (Mw) and the number-average molecular weight (Mn) of DNA as well as of their breakage parameters (Nw andNn) is presented. The calculations are based on the radioactivity profiles of tritium-labelled DNA sedimented in alkaline sucrose gradients using a liquid scintillation spectrometer.With the aim of the approximation formula fromBurgi undHershey (1963) the exponentK has been estimated from the sedimentation of standard DNA with standard conditions and yields to 0.353.The data are printed out by mean of a computer-controlled typewriter or as a plot by mean of a computer-controlledX- Y plotter. The drawing program is adapted for different modes of standardisation. The most significant capabilities of the program are the estimation of the molecular weight and breakage number of any fraction or region of the sedimentation profile. In addition the graphic plot permits by use of different standardisation the estimation of quantitative changes under the experimental conditions.

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HP 9810A. (Mw, Mn Nw, Nn) () . , , , , — (1963). 0,353. . . , .

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Herrn Prof. Dr. Drs. h. c.Hans Stubbe zum 75. Geburtstag gewidmet.     

Ecological basis of parasite control: Trematodes with special reference to fascioliasis

In this paper the main ecological components of selected animal trematode infection cycles are considered with regard to the possibilities of control. The geographical distributions of Fasciola hepatica, F. gigantica, Paramphistomum microbothrium, Schistosoma bovis and S. mattheei are compared in relation to the distribution patterns of their snail intermediate hosts. In order to constitute an effective lifecycle host, intermediate host and the eggs and freeliving stages of the parasite overlap in the effective biotope. Comparing the biotopes of the different trematodiases it becomes evident that they have much in common particularly as the snail intermediate hosts occupy identical niches in a food-chain in which the pollution by the host species results in abundant food for the snail. Moreover, the physical activaties of herbivores, e.g. trampling down the turf, create favourable habitats for the intermediate host.The dynamic nature of the freshwater snail habitats characteristic for trematodiasis, regularly results in a complete disappearance of the effective biotopes in the field. With regard to the parasite these effects are overcome by a long life-expectancy of egg producing parasites in the host population. Small scale changes in availability of appropriate hosts for successful cercarial establishment are compensated by the extended period of cercarial shedding from the snail population.These features in combination with the survival of eggs and the grazing and drinking behaviour characteristics of the hosts tend to stabilize the potential oscillations in transmission rate. Because of the complicated nature of interdependency within the host-trematode-intermediate host complex, the ecological base with regard to practical measures is fundamentally wide. However, the pressure upon the situation by social and economic conditions limits operative possibilities considerably.