Synthesis and insecticidal activities of unsymmetrical bis-arylalkyl ketones. A new structural concept in pyrethroids

Seventeen unsymmetrical bis-arylalkyl ketones were synthesised and their insecticidal activities against Musca domestica, Locusta migratoria, Drosophila melanogaster, Dysdercus cingulatus, Aedes aegypti and Tetranychus urticae were tested. The synergistic effect of piperonyl butoxide on the activities of some of the new ketopyrethroids against Musca domestica was also determined. Several structural variations, including substituent exchange in the aryl moieties, the position of the ketone function and increase or decrease of the length of the carbon chain connecting the two aryl moieties, were made in order to examine the structure-activity relationship. All biological activities were compared with the activity of the ether pyrethroid 2-(4-ethoxyphenyl)-2-methylpropyl 3-phenoxybenzyl ether (MTI-500).     

Colonisation by arbuscular mycorrhizal and fine endophytic fungi in four woodland grasses – variation in relation to pH and aluminium

Acidic soils are harsh environments for plants. One of the major problems is the potential toxicity of aluminium (Al) and hydrogen ions at a pH below 5; another is the shortage of nutrients usually accompanying soil acidity. The aim of this study was to elucidate the relationship between arbuscular mycorrhizal (AM) colonisation and soil acidity (measured by pH and Al concentration) in order to evaluate the possibility that AM fungi facilitate the existence of plants on acidic soils. We sampled tussocks of four grass species, Elymus caninus, Poa nemoralis, Deschampsia cespitosa and Deschampsia flexuosa, together with samples of the surrounding soil, in oak forests of varying soil pH in southern Sweden. We determined pH, easily reacting Al (Al_r), extractable Al (Al_BaCl2) and phosphate in the soil samples, analysed the shoots for Al and phosphorous and quantified the degree of AM and fine endophyte (FE) colonisation in the roots. E. caninus was found on the least acidic soils and had the highest AM colonisation of all the species studied, while D. flexuosa, which was found on the most acidic soils, had the lowest AM colonisation. P. nemoralis and D. cespitosa were intermediate with respect to pH and AM colonisation. The colonisation of AM fungi exceeded FE colonisation for E. caninus and P. nemoralis, while the opposite was true for the two Deschampsia species. Our results indicated a negative relationship between Al_r and the degree of AM colonisation at the within-species level. The low colonisation of AM fungi on acidic soils may to some extent be explained by a sensitivity of AM fungi to Al_r: this parameter showed a stronger negative association with AM colonisation than did pH and Al_BaCl2. We hypothesize that Al toxicity is a critical factor for plant nutrition in forest soils through the impact on symbiotic fungi.     

Silicon fractions in Histosols and Gleysols of a temperate grassland site

The importance of silicon (Si) in nutrition is currently being recognized by its beneficial effects on many crops. Therefore, it is important to determine the soil Si status and to examine different extractants for testing plant‐available Si. Little information is available about the Si status of Histosols and C_org‐rich Gleysols in temperate climate. This study was undertaken (1) to characterize different Si pools in C_org‐rich groundwater soils of an experimental site and (2) to study the influences of small‐scale variability on element distribution. At the experimental site, the thickness of the C_org‐rich layer ranges between 4 and 5 dm overlying fine‐sandy fluvial sediments. Four extractants were evaluated: 0.01 M CaCl₂, 0.5 M acetic acid, 0.1 M sodium pyrophosphate, and 0.1 M Tiron (C₆H₄Na₂O₈S₂ · H₂O). Further, total element content was determined following HNO₃/HF digestion. Calcium chloride–soluble Si shows no significant relations to other parameters analyzed. On the basis of published data, the soils investigated could be classified as Si‐deficient. The Si fraction extracted with acetic acid displays relations to C_org content of the soil and a weak correlation to CaCl₂‐soluble Si, indicating that both solutions extract overlapping but not the same fractions. Sodium pyrophosphate extracts mainly organo‐mineral Fe and Al complexes in the soils studied, which is reflected in a highly positive correlation to C_org. Pyrophosphate‐soluble Si showed a negative relationship to C_org, which means a closer relation of this Si fraction to mineral matter than to C_org. The Tiron solution extracted most Si of all extractants, but this amounts only 1% of the total Si content. Taking into account the element‐specific relationship between pyrophosphate and Tiron‐extractable Fe, Al, and Si, it can be concluded that Tiron dissolves mainly the opaline silica present in Histosols and C_org‐rich Gleysols. The distribution of C_org and ash content shows clear spatial trend at the experimental site, which is correlated to pyrophosphate‐extractable as well as total Si. This small‐scale variability of soil parameters itself is related to a distinct microrelief.     

The world's richest tadpole communities show functional redundancy and low functional diversity: ecological data on Madagascar's stream-dwelling amphibian larvae

Background  

Functional diversity illustrates the range of ecological functions in a community. It allows revealing the appearance of functional redundancy in communities and processes of community assembly. Functional redundancy illustrates the overlap in ecological functions of community members which may be an indicator of community resilience. We evaluated patterns of species richness, functional diversity and functional redundancy on tadpole communities in rainforest streams in Madagascar. This habitat harbours the world's most species-rich stream tadpole communities which are due to their occurrence in primary habitat of particular interest for functional diversity studies.     

<Emphasis Type="Italic">Sugarcane yellow leaf virus</Emphasis> introduction and spread in Hawaiian sugarcane industry: Retrospective epidemiological study of an unnoticed,mostly asymptomatic plant disease

Yellow leaf (YL) caused by Sugarcane yellow leaf virus (SCYLV) was first reported as a sugarcane disease in the 1990s, when it had already spread over many parts of the world. The time of introduction into the plantations is unknown. A worldwide screening identified only a few places isolated from cultivar exchange for more than 20 years which appeared SCYLV-free. Control tests with infected cultivars propagated for 12–16 generations by cuttings remained SCYLV-infected, proving that SCYLV is not eliminated by vegetative propagation. De novo infection by SCYLV-vectors in Hawaii occurred only over short distances. To reveal the period when SCYLV was introduced to Hawaii, volunteer sugarcane plants from closed Hawaiian plantations and from previous sites of the Hawaiian Sugarcane Planters′ Association breeding station were tested. The results suggest that SCYLV appeared in the breeding station between 1960 and 1970, whereas the plantations became infested after 1980. Imports in the 1960s obviously introduced the virus to the Hawaiian breeding station from where it spread to susceptible cultivars. Eighty percent of the cultivars, developed between 1973 and 1995, acquired the virus at the breeding station, in some cases within 4 years, indicating the rapid spread of SCYLV in the breeding station. The strain of SCYLV found in a Réunion cultivar in Hawaii, and the differing SCYLV-infection of CP-cultivars which were exported more than 20 years ago, suggested that also Réunion and Florida may still have been SCYLV-free in the 1970s. The study showed that retrospective epidemiology can be conducted on a disease which was unnoticed for more than 20 years.     

Carbohydrate composition of sugarcane cultivars that are resistant or susceptible to <Emphasis Type="Italic">Sugarcane yellow leaf virus</Emphasis>

Sugarcane cultivars with a high (susceptible cultivars) and low (resistant cultivars) virus titer of Sugarcane yellow leaf virus were grown in the field. The carbohydrate composition in green leaf tops and in stems was determined. In RT-PCR of leaf extracts, susceptible cultivars had a high SCYLV-titer, whereas resistant cultivars had a very low titer. The cultivars differed in biomass yield, but these differences were not correlated with susceptibility. However, carbohydrate composition did have susceptibility-specific differences. Hexose levels were lower in green leaf tops and stalks of susceptible (strongly infected) cultivars than in those of resistant (weakly infected) cultivars. The stalks of susceptible cultivars also had less starch than those of resistant cultivars. Thus, the viral susceptibility (and infection) affected sugar metabolism. In addition, a positive correlation between hexose and starch in stems and between hexose and sucrose in green leaf tops was observed. The results from susceptible versus resistant cultivars were the opposite of those in the comparison between infected versus virus-free lines of the same cultivar. The breeding process apparently had unintentionally selected clones with modulated carbohydrate metabolism to avoid or compensate for the adverse effects of SCYLV infection.     

Serodiagnosis of pearl millet resistance to downy mildew by quantitating cell wall P/HRGP using polyclonal antiserum Pab-P/HRGP

Proline/hydroxyproline-rich glycoprotein (P/HRGP) level in pearl millet genotypes resistant to downy mildew increase after inoculation with the oomycete pathogen Sclerospora graminicola. Using purified P/HRGPs from pearl millet cell walls, polyclonal antibodies (Pab-P/HRGP) were raised in rabbit. Based on this antiserum, an enzyme immunoassay was developed that displays a linearity detection range from 0.01 to 10 μg P/HRGP. Western blot analysis, confirming the induction of three marker P/HRGPs in the infected resistant genotype, and immunocytochemical studies on P/HRGP localization either in epidermal peelings or in suspension-cultured cells demonstrated the specificity of the antiserum. Besides its characterization, Pab-P/HRGP was employed to screen various genotypes of pearl millet for fast, sensitive and specific detection of induced P/HRGPs upon infections. The results presented are discussed with presumed importance to downy mildew disease and the use of this new antiserum in pearl millet screening for disease resistance.     

Soil water storage appears to compensate for climatic aridity at the xeric margin of European tree species distribution

Based on macroecological data, we test the hypothesis whether European tree species of temperate and boreal distribution maintain their water and nutrient supply in the more arid southern margin of their distribution range by shifting to more fertile soils with higher water storage than in their humid core distribution range (cf. soil compensatory effects). To answer this question, we gathered a large dataset with more than 200,000 plots that we related to summer aridity (SA), derived from WorldClim data, as well as soil available water capacity (AWC) and soil nutrient status, derived from the European soil database. The soil compensatory effects on tree species distribution were tested through generalized additive models. The hypothesis of soil compensatory effects on tree species distribution under limiting aridity was supported in terms of statistical significance and plausibility. Compared to a bioclimatic baseline model, inclusion of soil variables systematically improved the models’ goodness of fit. However, the relevance measured as the gain in predictive performance was small, with largest improvements for P. sylvestris, Q. petraea and A. alba. All studied species, except P. sylvestris, preferred high AWC under high SA. For F. sylvatica, P. abies and Q. petraea, the compensatory effect of soil AWC under high SA was even more pronounced on acidic soils. Soil compensatory effects might have decisive implications for tree species redistribution and forest management strategies under anthropogenic climate change. Therefore, soil compensatory effects deserve more intensive investigation, ideally, in studies combining different spatial scales to reduce the uncertainty associated with the precision of soil information.     

Element concentrations and storage in the aboveground biomass of limed and unlimed Norway spruce trees at Höglwald

Twenty years after the application of dolomitic limestone to a well growing, mature Norway spruce stand at Höglwald, Southern Germany an amount of magnesium equal to the input by liming has left the rooting zone. However, 80% of the applied calcium was retained by the ecosystem. A detailed biomass investigation was carried out in order to elaborate whether the stand shows any nutritional benefits and if the aboveground tree biomass represents a sink for calcium and magnesium after liming. Stem wood, bark, branches, twigs, and needles were analysed for the major nutrients. Needles showed higher calcium and magnesium concentrations and significantly lower potassium concentrations on the limed plot. Surprisingly, limed trees had significantly lower magnesium concentrations in the bark but higher concentrations in twigs and needles than unlimed trees. In addition, significantly lower concentrations for potassium, sulphur, and phosphorus were measured in the bark of limed trees, whereas the element concentrations in the wood were rather similar between the two treatments. The low potassium concentrations in bark and needles indicate an impeded potassium uptake after liming presumably due to a calcium potassium antagonism. Magnesium is probably used to compensate the relative lack of potassium. The small differences in the calculated nutrient storage of limed and unlimed trees, however, suggest that the aboveground biomass can be excluded as a relevant sink for the applied calcium and magnesium at the Höglwald site.     

On the role of sawdust in the development of mastitis in cows

Sawdust was aspirated into one of the teatcups of the milking unit by induced liner slip during milking of 10 cows, which were then slaughtered. Sawdust particles were recovered from the interior of the quarters, the teat skin and the inside of the liners corresponding to both treated and untreated teats, and from the milk claw and the bucket as well. Sterile sawdust was introduced into the teat cisterns of three quarters of one cow. Clinical mastitis developed. The investigation was initiated by an outbreak of Serratia-mastitis in a dairy herd and supports the view that the outbreak was caused by contaminated sawdust used as litter in combination with improper detachment of the milking units. Widening of the impact concept is propsosed.