Metabolism and fate of triazophos in rats

The excretion patterns and tissue residues were determined after single and repeated oral dosing of rats with triazophos-¹⁴C Within 4 days after a single oral dose 76.3 % of the ¹⁴C was excreted in the urine and 21.0% in the faeces. After daily application for 12 days 69.5–83.4% of the label was eliminated in urine and 30.9–18.1 % in the faeces. Following prolonged application, however, elimination is distinctly slower. Distribution of radioactive residues in organs and tissue in both test series showed no appreciable or critical concentrations of radioactivity, with the exception of the gastrointestinal tract (contents and walls). Unchanged triazophos and l-phenyl-1,2,4-triazol-3-ol-3-¹⁴C were excreted in the faeces. Renewed release of other metabolites into the gastrointestinal tract apparently does not take place. The following metabolites are detected in the urine: urea-¹⁴C (approx. 85% of the radioactivity excreted with the urine); and three compounds as conjugates with glucuronic acid, i.e. 1-phenyl-l,2,4-triazol-3-ol-3-¹⁴C (approx. 3%), l-phenylsemicarbazide-3-¹⁴C (approx. 5%), and semicarbazide-¹⁴C (approx. 5%). Two further metabolites, so far unidentified, occurred in small quantities.     

Wirkung von Neem-Produkten auf höhere Pflanzen und ihre mögliche Nutzung zur Reduzierung der Seitentriebe von Kulturpflanzen sowie zur Unkrautbekämpfung – eine Bestandsaufnahme

The neem tree (Azadirachta indica A. Juss) offers many possibilities of usage. In plant protection mostly the insecticidal activity of neem products is important. In different parts of the plant several biologically active substances occur. One is the active ingredient azadirachtin, which already is commercially used as an insecticide against insect pests. Some active ingredients of neem may be systemically taken up by the treated plants. Often a rapid decomposition occurred which was enhanced by UV radiation. Therefore formulated neem products often need a UV blocker to elongate their activity. After the application of neem products within plant protection sometimes phytotoxic effects could be observed on different plant species. This phytotoxicity can be used to reduce suckers on tobacco plants and recently also on eucalyptus plants. The existing trials to use neem products for weed control mostly concentrated on the direct treatment of some parasitic weeds like Cuscuta, Orobanche and Striga as well as on a few other weeds (e.g. Echinochloa crus-galli). Mostly the growth of the weeds which were often repeatedly treated with high dosages was reduced, but many plants remained still alive. At present the potential of neem products for an effective weed control is not sufficiently investigated. As a consequence of some already known insecticidal and microbiocidal activities of many neem products also side effects on parts of the epigeic and soil fauna and on the nitrification should be considered after usage for weed control.     

Fire place preferences of forest visitors in northwestern Switzerland: Implications for the management of picnic sites

Some recreational activities in urban forests can cause extensive damage to soil and vegetation. In Switzerland, forest visitors frequently build fires outside picnic sites for barbecuing. This indicates that the existing picnic sites are either not attractive enough for these visitors, or that there are not enough sites for all the visitors during peak days. We used an on-site survey to assess the requirements of picnickers in two forest areas in the vicinity of Basle. Results showed that the existing picnic sites do not meet the requirements of some visitor groups, causing the respective visitors to make their own fires in locations that suit them better. There was a preference for sites near streams, away from forest roads and close to open spaces. Furthermore, while some visitors highly appreciated the well-equipped official sites, others preferred more natural infrastructure with pieces of stones forming a fire ring rather than concrete rims, and logs to sit on instead of benches. Picnic sites that are closer to the requirements of visitors who normally steer away from official sites might reduce the number of self-made fire rings. The study shows that understanding visitor behaviour is a prerequisite for the implementation of measures to reduce ecological impacts.     

Productivity of mixed versus pure stands of oak (Quercus petraea (Matt.) Liebl. and Quercus robur L.) and European beech (Fagus sylvatica L.) along an ecological gradient

The mixture of beech (Fagus sylvatica L.) and oak (sessile oak, Quercus petraea (Matt.) Liebl., and pedunculate oak, Q. robur L.) is of considerable importance in Europe and will probably become even more important under climate change. Therefore, the performance of oak and beech in mixture was compared with the species’ growth in pure stands. Data from 37 long-term mixing experiments in Poland, Germany and Switzerland were pooled for analysis of mixing effects on stand productivity and possible interrelationships with mixing portions or site conditions. We found that on average, mixed stands of oak and beech exceeded biomass productivity in pure stands by 30 % or 1.7 t ha^?1 year^?1, as the growth of both species was benefitted by the mixture. However, that the interaction actually ranged from facilitation and overyielding on poor sites to underyielding on fertile sites triggered by competition. An empirically derived interaction model showed volume and dry mass growth changing in mixed stands from gains of 50 % to losses of 10 % depending on site conditions. It is concluded that the analysed mixture grows in accordance with the stress-gradient hypothesis and that our results suggest a site-specific relationship between species mixture and biomass productivity. As a consequence, an adequate species mix should result in increased productivity under steady state as well as climate change.     

Is heterosis an artefact governed by the choice of scale?

When estimating heterosis it is often necessary to transform either the data or, within the context of generalized linear models, the linear predictor, to satisfy certain assumptions. In this note it will be argued that the amount of heterosis is scale-dependent varying with the kind of transformation. The same applies for the examination of dominance in quantitative genetics. We exemplify the varying heterotic effect with phenotypic data of maize roots. Either a data transformation or a generalized linear mixed model with appropriately chosen link function is applied to the data. It is concluded that care should be exercised when transforming data in phenotypic as well as quantitative-genetic studies because partial dominance or heterosis may be removed by a suitably chosen transformation. With data transformations, even overdominance or better parent heterosis may disappear. When a data transformation is needed to meet the usual statistical assumptions such as normality and homogeneity of variance, a back-transformation to the original scale may be necessary, depending on what is deemed the appropriate scale for assessing genetic effects.     

Extending Finlay–Wilkinson regression with environmental covariates

Finlay–Wilkinson regression is a popular method for analysing genotype–environment interaction in series of plant breeding and variety trials. It involves a regression on the environmental mean, indexing the productivity of an environment, which is driven by a wide array of environmental factors. Increasingly, it is becoming feasible to characterize environments explicitly using observable environmental covariates. Hence, there is mounting interest to replace the environmental index with an explicit regression on such observable environmental covariates. This paper reviews the development of such methods. The focus is on parsimonious models that allow replacing the environmental index by regression on synthetic environmental covariates formed as linear combinations of a larger number of observable environmental covariates. Two new methods are proposed for obtaining such synthetic covariates, which may be integrated into genotype-specific regression models, that is, criss-cross regression and a factor-analytic approach. The main advantage of such explicit modelling is that predictions can be made also for new environments where trials have not been conducted. A published dataset is employed to illustrate the proposed methods.