Eine revidierte Liste der bisher beschriebenen Arten der GattungOchromonas

Ohne Zusammenfassung     

Efficacy of plant metabolites of imidacloprid against Myzus persicae and Aphis gossypii (Homoptera: Aphididae)

The metabolism of the chloronicotinyl insecticide imidacloprid is strongly influenced by the method of application. Whilst in foliar application most of the residues on the leaf surface display unchanged parent compound, most of the imidacloprid administered to plants by soil application or seed treatment is metabolized more or less completely, depending on plant species and time. The present study revealed that certain metabolites of imidacloprid which have been described in crop plants are highly active against aphid pests in different types of bioassays. Some of these metabolites showed a high oral activity against the green peach aphid (Myzus persicae), and the cotton aphid (Aphis gossypii). The aphicidal potency of the metabolites investigated was weaker in aphid dip tests than in oral ingestion bioassays using artificial double membranes. The most active plant metabolite was the imidazoline derivative of imidacloprid. The LC₅₀ values of this metabolite for M. persicae and A. gossypii in oral ingestion bioassays were in the lower ppb-range, i.e. 0·0044 and 0·0068 mg litre^-1, respectively. Most of the other reported metabolites showed much weaker activity. Compared to imidacloprid, the imidazoline derivative showed superior affinity to housefly (Musca domestica) head nicotinic acetylcholine receptors, while all other metabolites were less specific than imidacloprid. It seems possible that, after seed treatment or soil application, a few of the biologically active metabolites arising are acting in concert with remaining levels of the parent compound imidacloprid, thus providing good control and long-lasting residual activity against plant-sucking pests in certain crops. © 1998 SCI.     

A trans-disciplinary study on the health risks of cryptosporidiosis from dairy systems in Dagoretti,Nairobi, Kenya: study background and farming system characteristics

This paper characterises the dairy farming system in Dagoretti, Nairobi. Characterisation was part of a broader ecohealth project to estimate the prevalence and risk of cryptosporidiosis and develop risk mitigation strategies. In the project a trans-disciplinary team addressed epidemiological, socioeconomic, environmental and policy aspects of cryptosporidiosis, an emerging zoonosis. This paper also provides background and describes sampling methods for the wider project. Three hundred dairy households were probabilistically sampled from a sampling frame of all dairy households in five of the six locations of Dagoretti, one of the eight districts of Nairobi Province. Randomly selected households identified 100 non-dairy-keeping households who also took part in the study. A household questionnaire was developed, pre-tested and administered in the dry and wet seasons of 2006. An additional study on livelihood and economic benefits of dairying took place with 100 dairy farmers randomly selected from the 300 farms (as well as 40 non-dairy neighbours as a control group), and a risk-targeted survey of environmental contamination with Cryptosporidium was conducted with 20 farmers randomly selected from the 29 farmers in the wider survey who were considered at high risk because of farming system. We found that around 1 in 80 urban households kept dairy cattle with an average of three cattle per household. Cross-breeds of exotic and local cattle predominate. Heads of dairy-keeping households were significantly less educated than the heads of non-dairy neighbours, had lived in Dagoretti for significantly longer and had significantly larger households. There was a high turnover of 10 % of the cattle population in the 3-month period of the study. Cattle were zero grazed, but productivity parameters were sub-optimal as were hygiene and husbandry practices. In conclusion, dairy keeping is a minor activity in urban Nairobi but important to households involved and their community. Ecohealth approaches are well suited to tackling the complex problem of assessing and managing emerging zoonoses in urban settings.     

Disentangling the effect of size and competition: a growth model for Aucoumea klaineana

• Context Okoume (Aucoumea klaineana) is the most important timber species in Gabon, while being classified as vulnerable in the IUCN red list. Thousands of growth measurements for this species have been performed since the 1950s but, because of a lack of integrated analysis, did not bring a consistent view on its growth pattern.
• Aims This study aims at disentangling the effects of tree size and local competition on tree growth.
• Methods A growth model was fitted for okoume, using data from seven sites in Gabon and Congo. The growth model was designed to be useful for forest management, which means that it relied on variables that could be computed using forest inventory data.
• Results A lognormal growth model with a negative response to stand basal area was selected. A significant residual site effect on growth was found, with a slower growth in the sites near the border of the natural range of okoume than in the sites far from it.
• Conclusion Growth strongly responded to local stand attributes such as tree density and basal area. Growth decrease with stand age in monodominant okoume stands was correctly predicted, although tree age was not incorporated into the model.

     

Pilzentwicklung in Fichtenholz unter Schutzgasatmosphäre

Fungal growth in spruce timber stored under low oxygen atmosphere . Fungal growth and species composition in Norway spruce timber (Picea abies) stored under an atmosphere with low oxygen concentration was monitored by isolation techniques. The results were compared with those from unprotected wood and from living trees. The role of potentially antagonistic fungi is discussed.     

PCR-SSCP用于针叶树种遗传分析的可行性

利用松树单倍体胚乳,双倍体的针叶材料,扩增了叶绿体基因组和核基因组的５个ＤＮＡ片段,研究了ＳＳＣＰ这一分析方法的可靠性。结果表明ＳＳＣＰ分析方法具有坚实的分子基础、较高的分辨率和试验重复性。对ＳＳＣＰ谱带在杂交子代和单倍体胚乳的分离分析,证明了ＳＳＣＰ还具有良好的遗传稳定性。     

Climate and forest management influence nitrogen balance of European beech forests: microbial N transformations and inorganic N net uptake capacity of mycorrhizal roots

The effects of local climate and silvicultural treatment on the inorganic N availability, net N uptake capacity of mycorrhizal beech roots and microbial N conversion were assessed in order to characterise changes in the partitioning of inorganic N between adult beech and soil microorganisms. Fine root dynamics, inorganic N in the soil solution and in soil extracts, nitrate and ammonium uptake kinetics of beech as well as gross ammonification, nitrification and denitrification rates were determined in a beech stand consisting of paired sites that mainly differed in aspect (SW vs. NE) and stand density (controls and thinning treatments). Nitrate was the only inorganic N form detectable in the soil water. Its concentration was high in control plots of the NE aspect, but only in canopy gaps and not influenced by thinning. Neither thinning nor aspect affected the abundance of root tips in the soil. Maximum nitrate net uptake by mycorrhizal fine roots of beech, however, differed with aspect, showing significantly lower values at the SW aspect with warm–dry local climate. There were no clear-cut significant effects of local climate or thinning on microbial N conversion, but a tendency towards higher ammonification and nitrification and lower denitrification rates on the untreated controls of the SW as compared to the NE aspect. Apparently, the observed sensitivity of beech towards reduced soil water availability is at least partially due to impaired N acquisition. This seems to be mainly a consequence of reduced N uptake capacity rather than of limited microbial re-supply of inorganic N or of changed patterns of inorganic N partitioning between soil bacteria and roots.     

Possible function of isoleucine in the methyl jasmonate response of <Emphasis Type="Italic">Arabidopsis</Emphasis> to <Emphasis Type="Italic">Phelipanche aegyptiaca</Emphasis>

Resistance of Arabidopsis thaliana to Phelipanche aegyptiaca (syn. Orobanche aegyptiaca) can be induced by exposure of the host to low concentrations of gaseous methyl jasmonate, in a concentration-dependent fashion. Application of methyl jasmonate at marginal concentrations, 10⁻⁸ M, for 12 h reduced infection by 50%. However, if the host plants were supplied with isoleucine at 10⁻³ M, and the isoleucine removed prior to exposure to methyl jasmonate, infection was reduced to less than 20%. The presence of isoleucine throughout the experiment—before, during and after exposure to methyl jasmonate—reduced infection of the host to almost zero. These results suggest that when Arabidopsis is exposed to methyl jasmonate, full activation of the defense mechanisms, including formation of the isoleucine jasmonic acid conjugate, might be limited by the availability of isoleucine in the host. These findings add another factor to the complex interaction between infecting parasite, and evocation of host defense mechanisms.     

Helianthus tuberosus L. als Pilznährsubstrat

Zusammenfassung Es wird über Untersuchungen zur Verwendung von Topinamburrhizomknollen als Nährsubstrat für Pilzkulturen in Abhängigkeit vom jahreszeitlichen Entwicklungszustand der Rhizome und einigen anderen Faktoren sowie über Erfahrungen mit Stammkulturen auf solchen Böden berichtet.

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Summary Experiments made using rhizome-tubers from the Jerusalem-artichoke as a substratum for culturing fungi are given, examining whether seasonal fluctuations are influencing the suitability as a substrate for fungal growth concluding from increase of fall of yields in fungal growth. Facts and data refering to experiences in maintaining stock-cultures on these substrata are reported.

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Der Einfluß niedriger Temperaturen auf den Gärverlauf in Traubenmost und seine Auswirkung auf Zusammensetzung und Qualität des Weines

Zusammenfassung Aufgrund von Labor- und Großversuchen wurde festgestellt, daß sich in jeder Hefepopulation von frisch gekelterten Mosten Organismen finden, mit deren Hilfe es möglich ist, eine Gärung bei Temperaturen zwischen 5 und 10°C durchzuführen. Wenn es sich dabei vermutlich auch nicht um typische Kaltgärhefen handelt, so gelingt es doch ohne Schwierigkeit, das Verfahren der gekühlten Gärung nachSaller ohne Verwendung von speziellen Kaltgärreinhefeansätzen vorzunehmen. Der Einfluß dieses Verfahrens auf die chemische Zusammensetzung der Weine ist nur unbedeutend. Bemerkenswert ist lediglich die höhere Alkoholausbeute und der geringere Anteil an biogenen Säuren.Die Qualität der nach diesem Verfahren gewonnenen Weine übertraf insbesondere bei reifen Mosten und säurearmen Rebsorten die der Vergleichsweine, insbesondere inbezug auf das Bukett und die Fruchtigkeit sowie ihre Reintönigkeit.Herrn Prof. Dr.G. Bredemann zu seinem 80. Geburtstag gewidmet.