Variabilités verticale et temporelle des acides gras d'un phytoplancton lacustre au cours d'un cycle nycthéméral

Vertical and temporal variability in the content and composition of fatty acids in the lake phytoplankton were studied during a diel cycle (48 h). There is temporal variability in total fatty acid (FA) content per biomass unit but it is not strictly diurnal. In contrast, polyunsaturated FA with 20–22 C chains and unsaturated FA/ saturated FA ratio are higher during the day than during the night.The temporal variability was not as great as the variability is between sampling depths characterized by different phytoplankton assemblages. Phytoplankton composition and physiological state were the principal factors affecting FA composition. Thus, a C16:1w7/C18:1w9 ratio distinguishes between diatoms, with a high level of C16 unsaturated FA, and dinoflagellates with C18 unsaturated FA. This ratio was different at the surface and at 20 m depth, where the phytoplankton had the same taxonomic composition but a different physiological activity.

     

Response of coastal phytoplankton to ammonium and nitrate pulses: seasonal variations of nitrogen uptake and regeneration

Seasonal variation in uptake and regeneration of ammonium and nitrate in a coastal lagoon was studied using ¹⁵N incorporation in particulate matter and by measuring changes in particulate nitrogen. Uptake and regeneration rates were two orders of magnitude lower in winter than in summer. Summer uptake values were 2.8 and 2.2 mol N.l^–1.d^–1 for ammonium and nitrate, respectively. Regeneration rates were 2.9 and 2.1 mol N.l^–1.d^–1 for ammonium and nitrate respectively. Regeneration/uptake ratios were often below one, indicating that water column processes were not sufficient to satisfy the phytoplankton nitrogen demand. This implies a role of other sources of nitrogen, such as macrofauna (oysters and epibionts) and sediment. Phytoplankton was well adapted to the seasonal variations in resources, with mixotrophic dinoflagellates dominant in winter, and fast growing diatoms in summer. In winter and spring, ammonium was clearly preferred to nitrate as a nitrogen source, but nitrate was an important nitrogen source in summer because of high nitrification rates. Despite low nutrient levels, the high rates of nitrogen regeneration in summer as well as the simultaneous uptake of nitrate and ammonium allow high phytoplankton growth rates which in turn enable high oyster production.     

Phytoplankton around Elephant Island,Antarctica

Phytoplankton studies were conducted in a 4·10⁴ km² grid around Elephant Island, Antarctica, during January–March 1991. In addition to profiling studies at 50 stations during each of two cruises, pumped surface water was used to continuously record in vivo chlorophyll-a (chl-a) fluorescence and beam attenuation coefficients (c_t). Measurements on discrete samples included chl-a, phytoplankton organic carbon (A_c), and total particulate organic carbon (POC). Equations were developed which permitted contour-mapping of chl-a and POC throughout the entire grid based on continuous measurements of in vivo chl-a fluorescence and c_t values. Phytoplankton abundance increased from January–February (cruise I) to February–March (cruise II) as evidenced by mean surface chl-a values (0.8 and 1.34 g l^–1, respectively) and mean A_c values for the upper 20 m of the water column (21.3 and 39.8 g Cl^–1, respectively). Microplankton accounted for 29% (cruise I) and 40% (cruise II) of the total phytoplankton, based on direct measurements of chl-a. Patterns for integrated values of chl-a, A_c and POC were similar to patterns of concentrations in surface waters. The richest areas of phytoplankton were north of Elephant and King George Islands, which coincided with high krill density areas.     

Entwicklungsgeschichte und Ultrastruktur von Pollenkitt und Exine bei nahe verwandten entomophilen und anemophilen Angiospermensippen derAlismataceae,Liliaceae, Juncaceae,Cyperaceae, Poaceae undAraceae

Some closely related members of the monocotyledonous familiesAlismataceae, Liliaceae, Juncaceae, Cyperaceae, Poaceae andAraceae with variable modes of pollination (insect- and wind-pollination) were studied in relation to the ultrastructure of pollenkitt and exine (amount, consistency and distribution of pollenkitt on the surface of pollen grains). The character syndromes of pollen cementing in entomophilous, anemophilous and intermediate (ambophilous or amphiphilous) monocotyledons are the same in principal as in dicotyledons. Comparing present with former results one can summarize: 1) The pollenkitt is always produced in the same manner by the anther tapetum in all angiosperm sub-classes. 2) The variable stickiness of entomophilous and anemophilous pollen always depends on the particular distribution and consistency of the pollenkitt, but not its amount on the pollen surface. 3) The mostly dry and powdery pollen of anemophilous plants always contains a variable amount of inactive pollenkitt in its exine cavities. 4) A step-by step change of the pollen cementing syndrome can be observed from entomophily towards anemophily. 5) From the omnipresence of pollenkitt in all wind-pollinated angiosperms studied one can conclude that the ancestors of anemophilous angiosperms probably have been zoophilous (i.e. entomophilous) throughout.

     

Responses of phytoplankton to experimental fertilization with ammonium and phosphate in an African soda lake

Summary Phytoplankton abundance in tropical lakes is more often judged to be limited by nitrogen than phosphorus, but seldom does the evidence include controlled enrichments of natural populations. In January 1980 we performed the first experimental fertilization in an equatorial African soda lake, Lake Sonachi, a small, meromictic volcanic crater lake in Kenya. During our study the natural phytoplankton abundance was ca. 80 g chl a/l, and the euphotic zone PO₄ and NH₄ concentrations were less than 0.5 M. In the monimolimnion PO₄ reached 180 M and NH₄ reached 4,600 M. Replicate polyethylene cylinders (5 m long, 1.2 m³) were enriched to attain 10 M PO₄ and 100 M NH₄. Phytoplankton responses were measured as chlorophyll, cell counts and particulate N, P and C. After two days, the chlorophyll increase in the P treatment was significantly higher than the control (P<0.01) while the N treatment was not. After five days the molar N/P ratio of seston was the same in the N treatment and control (23) but only 6 in the P treatment. The molar N/P ratio of seston in an unenriched Lake Sonachi sample was 21 and in samples from Lakes Bogoria and Elmenteita, two shallow soda lakes in Kenya, the ratios were 12 and 70 respectively. We conclude that limitation of phytoplankton abundance by phosphorus can occur even in some tropical African soda lakes.     

Phytoplankton dynamics,primary productivity and community metabolism in a north-central Texas pond

Phytoplankton diversity, primary productivity and community metabolism were measured for 1 year in a 0.94 ha pond located in north-central Texas. Gross primary production ranged from 4.5 to 46.8 kcal m⁻² day⁻¹ ( =22.0 kcal m⁻² day⁻¹) and community metabolism ranged from 7.3 to 32.4 kcal m⁻² day⁻¹ ( =14.8 kcal m⁻² day⁻¹). Average production/respiration ratio (1.5) showed that the pond was principally autotrophic. Photosynthetic efficiency (gross primary production/0.5 total solar radiation) ranged from 0.32 to 2.8 with a mean of 1.2. Phytoplankton diversity based on numbers and biomass fluctuated greatly. Highest gross primary productivity occurred during Cyanophyta blooms in late summer-early fall when species diversity was minimal. Water temperature and turbidity, which governed light penetration, were the principal determinants of primary production.     

Phytoplankton biomass and primary production in semi-enclosed reef lagoons of the central Great Barrier Reef,Australia

Phytoplankton biomass and primary production rates within semi-enclosed reef lagoons of the central Great Barrier Reef were compared with adjacent shelf waters. Chlorophyll concentrations and surface primary production rates were usually higher in lagoons although seasonal differences were only significant during the summer. Nitrate concentrations were higher in lagoons than in shelf waters year-round. Nano- (<20 m size fraction) or pico-phytoplankton (<2 m size fraction) dominated phytoplankton biomass and production within reef lagoons throughout the year. Net phytoplankton (>10–20 m size fraction), however, were relatively more important in both reef lagoons and open shelf waters during the summer. Biomass-specific production within lagoons (range 41–90 mg C mg chl^–1 day^–1) was high, regardless of season. Lagoonal phytoplankton production (range 0.2–1.6 g C m^–2 day^–1) was directly correlated with standing crop and inversely related to lagoon flushing rates. Phytoplankton blooms develop within GBR reef lagoons during intermittent calm periods when water residence times exceed phytoplankton generation times.     

Trophic relationships of the sea ice meiofauna in Frobisher Bay,Arctic Canada

Summary A distinct fauna consisting mainly of nematodes, harpacticoid and cyclopoid copepods, rotifers, turbellarians and polychaete larvae, inhabits the lower levels of the sea ice in Frobisher Bay. Similar faunas are found throughout circumpolar regions. Thirteen taxa of the Frobisher Bay ice fauna were entirely herbivorous. Their food consisted of 26 genera of algae dominated by Chlamydomonas, Nitzschia, Navicula and Chaetoceros. There was a clear tendency to feed on the most abundant ice algae, hence little evidence of selective feeding. High algal food concentrations in the ice (estimated at 5000 g C/l) were in sharp contrast with the scant nourishment available from phytoplankton under the ice (8 g C/l) from mid-winter until the start of the summer bloom. Algal stocks and estimated productivity rates indicate that ice meiofaunal food requirements may be met by the ice algae. All the major ice meiofaunal species are well adapted to feeding within the ice. All are small enough to enter brine channels and secure particulate prey from surfaces within confined spaces. The ice meiofaunal species are major consumers of the ice algae and therefore important links in the transfer of energy from the ice to pelagic and benthic predators, including fishes, birds and mammals.     

Studies in Festuca. II. Fertility relationships between species of sections bovinae and scariosae,and their affinities with Lolium

Crossability anf F₁ hybrid fertility were studied using chromosome races (species or infra-specific taxa) representative of broad-leaved fescues in sections bovinae and scariosae. Hybrids were also obtained with Lolium multiflorum. The hybridization results, when considered in relation to morphology, cytology, and geographical distribution, support the idea that the Moroccan fescues studied here are more closely related amongst themselves, than to taxa from outside this region. These findings are discussed in relation to the evolution of the polyploids.     

Spontane Mutationen bei Essigsäurebakterien

Zusammenfassung Mit einer modifizierten Penicillintechnik konnten aus Acetobacter-Populationen, die von einem prototrophen Klon stammten, spontane auxotrophe Mutanten isoliert werden. Bei sechs von acht untersuchten Stämmen wurden auxotrophe Mutanten gefunden. Die Häufigkeit dieser Mutanten betrug 10^-6.Die Auxotrophie, welche je nach Stamm auf Äthanol- oder Glucose-Medium auftrat, äußerte sich als Bedarf für Hefeextrakt. Hefeextrakt konnte durch Alanin, Prolin oder Glutaminsäure nicht ersetzt werden. Die Mutation von prototroph auf Äthanol-Medium zu auxotroph auf Äthanol-Medium hatte keine Änderung der spezifischen Aktivitäten der Schlüsselenzyme des Glyoxylsäurecyclus zur Folge.Es wurden auch spontane Mutanten gefunden, welche die partikelgebundene Äthanoldehydrogenase verloren hatten und dadurch unfähig waren, Äthanol zu oxydieren oder als C-Quelle zu verwerten.Bei den spontanen, auf Äthanol-Medium auxotrophen Mutanten handelt es sich um Mutationen von einer Art des Frateurschen Systems in eine andere. Mutanten, welche die partikelgebundene Äthanoldehydrogenase verloren haben, gehören definitionsgemäß nicht mehr in die Gattung Acetobacter. Die Bedeutung solcher interspezifischer und intergenerischer Mutationen für die Arteinteilung innerhalb der Essigsäurebakterien wird diskutiert.

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Spontaneous mutations in acetic acid bacteria

Summary 8 prototrophic Acetobacter-strains were examined for spontaneous auxotrophic mutants. Using a modification of the Penicillin technique, there were detected auxotrophic mutants in 6 strains. The mutant frequency was 10^-6.Auxotrophy manifested itself as a requirement for yeast extract. Alanine, proline and glutamic acid could not replace yeastextract. In addition to the auxotrophic mutants there were found spontaneous mutants, which had lost the particulate ethanol-dehydrogenase and therefore had become unable to oxidise ethanol.The mutation from prototrophic on minerals-ethanol medium to auxotropic on minerals-ethanol medium represents a mutation from one species of Frateur's system into an other species. Mutants which have lost the particulate ethanol-dehydrogenase belong no more to the genus Acetobacter. The importance of such interspecific and intergeneric mutations for the taxonomy of acetic acid bacteria is discussed.

     

Sources and fluxes of particulate organic matter in shallow coastal waters characterized by summer macroaggregate formation

The origin and temporal variation in composition of sedimented particulate organic matter (POM) in the Gulf of Trieste (northern Adriatic) was studied over the year with special reference to the composition and sedimentation of macroaggregates in summer of 1991 using sediment traps.Suspended and sedimented POM, comprising a minor part of the largely inorganic total particulate matter, was prevalently of marine origin and composed mostly of humic substances followed by carbohydrates and proteins. Seasonal variations of particulate proteins and carbohydrates were correlated with variations of phytoplankton biomass. New production, occurring in late spring as a consequence of massive riverine inputs of N, Si and P nutrients in the surface layer of the Gulf, produced high particulate carbohydrate and protein concentrations. Subsequent depletion of introduced nutrients caused the decrease of particulate protein concentration but not that of particulate carbohydrate. The prolonged plankton biosynthesis of carbohydrates successively produced marine snow and later macroaggregates. The macroaggregates were characterized by ¹³C value of –19.9. and their carbohydrates were mostly composed of glucose followed in decreasing order by mannose, fructose, galactose, arabinose, ribose, xylose and fucose, suggesting a prevalent origin from phytoplankton structural heteropolysaccharides. Sedimentation of particulate organic constituents in the summertime, characterized by the massive presence of macroaggregates in the surface layer above the pycnocline, was the highest at a depth of 10 m at the end of this phenomenon, about six weeks after its first appearance. Sedimented macroaggregates were clearly traced by a characteristic ¹³C signal and higher carbohydrate concentrations. The monosaccharide composition was influenced by selective degradation in the water column. Sedimented POM in the bottom layer was, on the other hand, more affected by sediment resuspension. The mean yearly decrease of particulate protein-C and carbohydrate-C by 40–50% in the water column between the depths of 10 and 20 m indicates the preferential utilization of these constituents by microorganisms. The decrease of particulate humic-C is probably more the result of the export of particulate matter from the Gulf. This study also indicates that the macroaggregate formation has little impact on the annual C and N budget in such coastal areas.     

Seepage patterns, pore water, and aquatic plants: hydrological and biogeochemical relationships in lakes

This study documented linkages between lakeshore seepage fluxes, pore water chemistry, and aquatic plants in several lakes of the Adirondack Mountains region of New York, USA. Three replicate stations were set up along each of four different lake shorelines. From June through September 1998 and from snowmelt in April through August 1999, seepage flux was measured with seepage meters. Throughout this time period, lake surface water and pore water chemistry were monitored weekly to biweekly. At each station, leaf tissue chemistry of the water lily Nuphar variegatum was measured once in each year. Sediment chemistry and plant abundance were also measured once in 1998. We found that pore water concentrations of base cations, iron, and zinc were related to the direction, magnitude, and variability of seepage fluxes. Concentrations of base cations, iron, and zinc were both highest and most variable where seepage was low (0 to 50mLm^–2h^–1) in contrast to being more stable where seepage was highest and variable (–608 to 612mLm^–2h^–1). Leaf tissue chemistry and plant abundance were also related to seepage patterns. N. variegatum leaves had elevated zinc content at stations with low average discharge. Knowledge of seepage patterns helped to explain spatial patterns of elevated trace metal content in both pore water and plant tissues. Our work suggests that the hydrological process of lakeshore seepage exerts important controls on lakeshore biogeochemistry.     

Distribution and composition of particulate organic matter in the Ross Sea (Antarctica)

The biochemical composition and spatial distribution of particulate organic matter (POM) were studied in the Ross Sea (Antarctica) in summer 1989 to assess the quantitative role of organic carbon fractions in the cycling of organic matter in the water column. Large differences in chemical composition were observed between surface and deep layers. The results indicated that, despite large geographical differences, POM was quite homogeneous, of phytoplankton origin and mostly detrital. Different ratios were used to investigate the changes in biochemical composition of particulate organic matter in relation to the ice-melting: CN (organic carbonorganic nitrogen ratio) and C-POMPOC (sum of carbohydrate, protein and lipid carbontotal organic carbon ratio) were used to analyse the percentage of refractory organic material. PPRTPCHO (proteincarbohydrate ratio) were used to establish POM age and RNADNA ratios as a relative measure of particulate activity; POCChl a and N-PPRTChl a ratios were used to estimate the autotrophic contribution to the suspended particulate organic matter. Despite its low caloric value (5.3 Kcal g POM^–1), an high caloric content in the photic layer (1.6 Kcal m^–3 of POM and 2.5 Kcal m^–3 of POC) was found thus indicating that a large amount of food was available to higher trophic levels.     

Seasonal and diel relationships between the isotopic compositions of dissolved and particulate organic matter in freshwater ecosystems

A study of the isotopic composition of organic matter was conducted in a freshwater marsh over seasonal and diel time scales to determine the sources of dissolved organic matter (DOM) and the processes leading to its formation. Bulk C and N isotopic compositions of the bacterial fraction (0.2–0.7 m) and particulate organic matter (POM; 0.7–10 m) were compared on a seasonal basis with the change in ¹³C of DOM. The bulk isotopic data support the idea that DOM was, in part, derived from the breakdown of larger organic matter fractions. The bacterial fraction and POM were compositionally similar throughout the year, based on a comparison of the ¹³C of individual amino acids in each fraction. Annual variation in the ¹³C of amino acids in DOM was greater relative to the variation in larger fractions indicating that microbial reworking was an important factor determining the proteinaceous component of DOM. The ¹³C enrichment of serine and leucine in each organic matter fraction suggested microbial reworking was an important factor determining organic matter composition during the most productive times of year. Changes in the bulk ¹³C of DOM were more significant over daily, relative to seasonal, time scales where values ranged by 6 and followed changes in chlorophyll a concentrations. Although bulk ¹³C values for POM ranged only from –29 to –28 during the same diel period, the ¹³C of alanine in POM ranged from –30 to –22. Alanine is directly synthesized from pyruvate and is therefore a good metabolic indicator. The ¹³C of individual amino acids in DOM revealed the diel change in the importance of autotrophic versus heterotrophic activity in influencing DOM composition. Diel changes in the ¹³C of phenylalanine, synthesized by common pathways in phytoplankton and bacteria, were similar in both DOM and POM. The diel change in ¹³C of isoleucine and valine, synthesized through different pathways in phytoplankton and bacteria, were distinctly different in DOM versus POM. This disparity indicated a decoupling of the POM and DOM pools, which suggests a greater source of bacterial-derived organic matter at night. The results of this study demonstrate the use of the isotopic composition of individual amino acids in determining the importance of microbial reworking and autotrophic versus heterotrophic contributions to DOM over both diel and seasonal time scales.     

Atomabsorptionsmessungen von Blei,Cadmium, Kupfer,Eisen und Zink im Seston der Ostsee

Zusammenfassung 1. Auf einer Forschungsfahrt in die Ostsee im April/Mai 1973 wurden 100 Sestonproben entnommen und auf ihren Gehalt an Blei, Cadmium, Zink, Kupfer und Eisen mit Hilfe der flammenlosen Atom-Absorptions-Spektrometrie analysiert.2. Die mittlere Konzentration im Seston der Ostsee beträgt für Blei 123 ppm, für Cadmium 5,8 ppm, für Zink 300 ppm, für Kupfer 61 ppm und für Eisen 3535 ppm.3. Im Vergleich zu Metallanalysen ozeanischen Sestons müssen die Blei- und Cadmiumkonzentrationen als stark überhöht angesehen werden.4. Die Konzentrationen des partikulär gebundenen Eisens, Zinks und Kupfers können bis auf lokal stark erhöhte Eisen- und Zinkkonzentrationen als natürlich angesehen werden.5. Arbeitsweise und Meßgenauigkeit der Metallanalytik werden beschrieben.

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Atomic absorption measurements of lead, cadmium, copper, iron and zinc in seston of the Baltic Sea

During a cruise with R. V. Alkor from Kiel Bight to Finnish Bay, nearly 100 seston samples were taken during April/May 1973. Samples from the 23 stations were analyzed for lead, cadmium, copper, iron and zinc by flameless atomic absorption spectrometry. The mean values for lead and cadmium were 123 and 5.8 ppm, respectively; for zinc, 733 ppm, for copper, 61 ppm, and for iron, 3535 ppm. In contrast to trace-metal analyses of off shore seston, the concentrations for lead and cadmium in Baltic-Sea seston are very high; these results are in good agreement with analyses of the dissolved metals. The concentrations of zinc, copper and iron in the particulate matter from the Baltic-Sea, apart from some local influences, agree well with values published from the concentrations in off shore seston. The distribution and variation of the individual values are discussed. The method for analysing the metals and its precision are briefly described.

     

Growth and development of spotted boll worm, Earias vittella on glanded and glandless cotton and on diet containing gossypol

Survival and growth of Earias vittella (F.) (= fabia Stoll) on glanded (Gossypium barbadense var. Giza-7 and G. thurberi) and glandless (G. hirsutum var. Empire glandless) cotton have been studied. When the larvae were reared on glanded cotton leaves, there was considerable decrease in larval survival, pupation, larval and pupal weight and an increase in the time taken for pupation as compared to those reared on glandless cotton. Similar results were also obtained when the larvae were reared on glandless cotton leaves treated with 1.0% gossypol.

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Wachststum und entwicklung von Earias vitella auf drüsenhaltiger und drüsenloser baumwolle und auf gossypolhaltigen nährböden

Zusammenfassung Die Reaktion von Earias vittella F.-Raupen auf drüsenhaltige Baumwolle (Gossypium barbadense, Var. Giza-7, und auf G. thurberi, eine Wildform) und auf drüsenlose Baumwolle (G. hirsutum Var. Empire glandless) wurde studiert. Bei Aufzucht der Raupen auf drüsenhaltiger Baumwolle wurde einige beträchtliche Reduktion im Uberleben der Raupen, in der Verpuppung, im Raupen- und Puppen-gewicht und eine Zunahme in der Puppendauer gegenüber Tieren von drüsenlosen Pflanzen festgestellt. Von den geprüften Sorten wurde die geringste Überlebensrate und ein langsames Wachstum auf G. thurberi gefolgt von Giza-7 beobachtet. Andererseits wurde immer das beste Überleben und das schnellste Wachstum auf Empire glandless gefunden.Die Frassreaktion verschiedener Raupenstadien auf unterschiedliche Konzentrationen von Gossypol wurde mit dem Blattscheibentest untersucht. Der Prozentsatz fressender frischgeschlüpfter Raupen war bei gossypolbehandelten Scheiben gegenüber unbehandelten Scheiben wesentlich reduziert. Die Frassabhaltung durch Gossypol war auf 4- und 6-tägigen Raupen noch ausgeprägter. Wenn frischgeschlüpfte Raupen durchgehend auf Blättern, die mit 1% Gossypol behandelt waren, gehalten wurden, konnte ein deutlicher negativer Effekt auf Wachstum und Entwicklung festgestellt werden.

     

Characterization of the light field in laboratory scale enclosures of eutrophic lake water (Lake Loosdrecht,The Netherlands)

Light conditions in laboratory scale enclosures (LSE) of shallow, eutrophic Lake Loosdrecht (The Netherlands), including a method for simulating a natural incident light course, are described. Total PAR (400–700 nm) and spectral irradiance distribution were measured at sestonic chlorophyll a and dry weight concentrations 100 mg m^–3 and 16 g m^–3, respectively. Phytoplankton was dominated by Oscillatoria spp. The euphotic depth (Z _eu) was 0.7–1.0 m. Shortly after filling the LSE with lake water, diffuse attenuation coefficients ranged from 14 m^–1 for blue to 5 m^–1 for red light. Around Z _eu, attenuation in the blue region was markedly lower and irradiance reflectance (R) continued to increase; these anomalies were caused by lateral incident light from the LSE's waterbath. Spectrophotometry indicated that absorption was mainly by particles, but dissolved humic substances (gilvin) were also important. The particles were likely to be dominated by detritus absorbing more blue relative to red light. Subsurface R in lake water in the LSE had a maximum around 705 nm and low values in the blue band, but was lower than that previously reported for measurements in situ. Wash-out of detritus, presumably both dissolved and particulate fractions, by flow-through with synthetic medium, greatly affected the spectral reflectance measured outside the LSE. The maximum value of R decreased from 0.022 to 0.009, and the peak shifted to 550 nm.     

Response of Tribolium castaneum larvae to synthetic aggregation pheromone

Responses of larval Tribolium castaneum Herbst. to the synthetic adult aggregation pheromone (4,8-dimethyldecanal) were studied. Larvae of T. castaneum were attracted both by contact and vapour of 4,8-dimethyldecanal at concentrations of 1, 5 and 10 g. g^-1 of medium.

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Reaktion von Tribolium castaneum Larven auf synthetisches Aggregationspheromon

Zusammenfassung Die Reaktionen der Larven von T. castaneum auf das kunstliche Aggregations pheromon (4,8-dimethyldecanal) in Versuchen in Petrischalen untersucht. Die Larven wurden angezogen, wenn sie mit Pheromon auf Filterpapier oder mit verdampftem Pheromon in Kontakt kamen. Diese Reaktion wurde bei Konzentrationen von 1, 5 und 10 g · g^-1 Medium festgestellt. Die höchste Konzentration rief die grosste Reaktion hervor. Fruhe Larvenstadien zeigten stärkere Reaktionen als spatere Stadien.

     

Chlorophylle und Carotinoide der Chaetophorineae (Chlorophyceae,Ulotrichales)

Zusammenfassung Bei der Untersuchung der Pigmente und des Stoffwechsels der Chaetophorineen wurden drei Stämme der Chaetophoracee Microthamnion kuetzingianum Naegeli näher analysiert. Neben den üblichen Chloroplastenpigmenten: Chlorophyll a und b, - und -Carotin, -Cryptoxanthin, Lutein, Zeaxanthin, Antheraxanthin, Violaxanthin, Neoxanthin und Neoxanthin Neo A konnte Siphonaxanthin identifiziert werden (ca. 30–40% der Gesamtcarotinoide). Es war nicht in den Chaetophoraceen Draparnaldia glomerata, Chaetophora elegans und Stigeoclonium helveticum var. maius zu finden. Dieses für viele Gattungen der Bryopsidales (= Siphonales) typische Keto-Carotinoid wurde damit auch außerhalb dieser Ordnung nachgewiesen. Seine Bedeutung als Leitcarotinoid wird diskutiert.

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Chlorophylls and carotenoids of the Chaetophorineae (Chlorophycea, Ulotrichales) 1. Siphonaxanthin in Microthamnion kuetzingianum Naegeli

Summary In the forthcoming series of papers we are going to investigate the chlorophylls and carotenoids of the members of the subordo Chaetophorineae (ordo: Ulotrichales). Three strains of Microthamnion kuetzingianum Naegeli have already been studied. In addition to the usual chloroplast pigments: chlorophyll a and b, -and -carotene, -cryptoxanthin, lutein, zeaxanthin, antheraxanthin, violaxanthin, neoxanthin, and neoxanthin neo A—siphonaxanthin was found (approx. 30–40% of total carotenoids). This keto-carotenoid does not occur in Chaetophora elegans, Draparnaldia glomerata, and in Stigeoclonium helveticum var. maius. Since Siphonaxanthin is typical for many genera of the Bryopsidales (= Siphonales) the chemotaxonomical significance of its occurrence outside this order is discussed.

     

Deposition of radiocesium to the soil by stemflow,throughfall and leaf-fall from beech trees

The amount of Chernobyl-derived¹³⁷Cs transferred to the soil by stemflow, throughfall (precipitation under the tree crown), and leaffall from three beeches was investigated as a function of time in the growing seasons of 1991 and 1992. Up to 70 Bq/week was deposited with the stemflow, mainly in dissolved form (<0.45 µm)=" rather=" than=" in=" particulate=" form=" (=">0.45 µm). The ratio of dissolved radiocesium to particulate radiocesium was about 10 in the stemflow. It varied considerably with time, but since these variations followed the same pattern for all three trees, they indicated a common cause to be responsible for the fractionation of radiocesium (e.g. meteorological conditions for bark weathering). A significant correlation was observed for the amount of dissolved¹³⁷Cs (in Bq) and the amount of stemflow (in liters). The¹³⁷Cs concentration in the stemflow (in Bq/1), however, decreased with increasing stemflow intensity (in Bq/week). For particulate radiocesium such correlations were not detected. Up to 5 Bq/m² per week was deposited with the throughfall from the canopy, mainly in particulate form (ratio dissolved radiocesium to particulate radiocesium = 0.34). The mean total annual amounts of¹³⁷Cs deposited to the ground (dissolved+particulate) for the three trees were: stemflow: 1991 600 Bq; 1992 460 Bq; throughfall: 1991 and 1992 100 Bq/m² each; leaffall: 1992 10 Bq/m². The data indicate that at present a substantial amount of the radiocesium in the leaves derives already from root uptake.Dedicated to Professor W. Jacobi on the occasion of his 65th birthday