Does chemical composition of individual Scots pine trees determine the biodiversity of their associated ground vegetation?

Despite plant secondary metabolites being major determinants of species interactions and ecosystem processes, their role in the maintenance of biodiversity has received little attention. In order to investigate the relationship between chemical and biological diversity in a natural ecosystem, we considered the impact of chemical diversity in individual Scots pine trees (Pinus sylvestris) on species richness of associated ground vegetation. Scots pine trees show substantial genetically determined constitutive variation between individuals in concentrations of a group of secondary metabolites, the monoterpenes. When the monoterpenes of particular trees were assessed individually, there was no relationship with species richness of associated ground flora. However, the chemical diversity of monoterpenes of individual trees was significantly positively associated with the species richness of the ground vegetation beneath each tree, mainly the result of an effect among the non‐woody vascular plants. This correlation suggests that the chemical diversity of the ecosystem dominant species has an important role in shaping the biodiversity of the associated plant community. The extent and significance of this effect, and its underlying processes require further investigation.     

Electron microscopic demonstration of cell surface carbohydrates by means of peroxidase and ferritin complexes of the Lens culinaris lection.

The use of Lens culinaris lectin for electron microscopic detection of D-mannose,- D-glucose and N-acetyl-D-glucosamine like sites on tumor cells, erythrocytes, erythrocyte ghosts, cultured rat liver cells and various tissues of mice is demonstrated. In addition to Lens culinaris lectin-peroxidase reaction (LeL-po reaction) the preparation of active Lens culinaris lectin-ferritin conjugate are described and the specificity of cytochemical reactions are demonstrated. Furthermore experiments by immuno freeze-etching are reported for topological analysis of the lectin receptors.     

The role of genetic and chemical variation of <Emphasis Type="Italic">Pinus sylvestris</Emphasis> seedlings in influencing slug herbivory

This study investigated the genetic and chemical basis of resistance of Pinus sylvestris seedlings to herbivory by a generalist mollusc, Arion ater. Using feeding trials with captive animals, we examined selective herbivory by A. ater of young P. sylvestris seedlings of different genotypes and correlated preferences with seedling monoterpene levels. We also investigated the feeding responses of A. ater to artificial diets laced with two monoterpenes, Δ³-carene and α-pinene. Logistic regression indicated that two factors were the best predictors of whether seedlings in the trial would be consumed. Individual slug variation (replicates) was the most significant factor in the model; however, α-pinene concentration (also representing β-pinene, Δ³-carene and total monoterpenes due to multicollinearity) of needles was also a significant factor. While A. ater did not select seedlings on the basis of family, seedlings not eaten were significantly higher in levels of α-pinene compared to seedlings that were consumed. We also demonstrated significant genetic variation in α-pinene concentration of seedlings between different families of P. sylvestris. Nitrogen and three morphological seedling characteristics (stem length, needle length and stem diameter) also showed significant genetic variation between P. sylvestris families. Artificial diets laced with high (5 mg g⁻¹ dry matter) quantities of either Δ³-carene or α-pinene, were eaten significantly less than control diets with no added monoterpenes, supporting the results of the seedling feeding trial. This study demonstrates that A. ater selectively feed on P. sylvestris seedlings and that this selection is based, in part, on the monoterpene concentration of seedlings. These results, coupled with significant genetic variation in α-pinene concentration of seedlings and evidence that slug herbivory is detrimental to P. sylvestris fitness, are discussed as possible evidence for A. ater as a selective force on the evolution of defensive chemistry in P. sylvestris.     

Influence of a 902.4 MHz GSM signal on the human visual system: investigation of the discrimination threshold

The proximity of a mobile phone to the human eye raises the question as to whether radiofrequency (RF) electromagnetic fields (EMF) affect the visual system. A basic characteristic of the human eye is its light sensitivity, making the visual discrimination threshold (VDThr) a suitable parameter for the investigation of potential effects of RF exposure on the eye. The VDThr was measured for 33 subjects under standardized conditions. Each subject took part in two experiments (RF-exposure and sham-exposure experiment) on different days. In each experiment, the VDThr was measured continuously in time intervals of about 10 s for two periods of 30 min, having a break of 5 min in between. The sequence of the two experiments was randomized, and the study was single blinded. During the RF exposure, a GSM signal of 902.4 MHz (pulsed with 217 Hz) was applied to the subjects. The power flux density of the electromagnetic field at the subject location (in the absence of the subject) was 1 W/m(2), and numerical dosimetry calculations determined corresponding maximum local averaged specific absorption rate (SAR) values in the retina of SAR(1 g) = 0.007 W/kg and SAR(10 g) = 0.003 W/kg. No statistically significant differences in the VDThr were found in comparing the data obtained for RF exposure with those for sham exposure.     

The light sensitivity of the human visual system depends on the direction of view

The near-stable North-South orientation of the natural geomagnetic field provides an ideal basis for navigation. Sailors have used it since ancient times, animals for much longer. Various mechanisms have developed for this purpose. Experiments have pointed to a connection between orientation in the geomagnetic field and light perception. Such observations are supported by theoretical considerations. The underlying interaction should also modulate the light sensitivity of the visual system. Recently we demonstrated the effect of an oscillating field. Here we report the existence of a weak influence of the static field on visual sensitivity in man. By comparison with control experiments, if the directions of view line and field vector coincide the perception threshold of a light stimulus is slightly but significantly increased. This significance is lost if the view line deviates by 10 degrees from the field direction.     

The magnetic field sensitivity of the human visual system shows resonance and compass characteristic

Orientation in the geomagnetic field is essential for many animal species. As yet, the interaction mechanisms of this weak field with the organisms are understood only incompletely. One mechanism in question is the interaction with the photochemical reaction in the retina. We show that the visual sensitivity of man is influenced by periodic sinusoidal inversion of the vertical component of the geomagnetic field. This effect indicates visual fixation in north-south direction and shows a pronounced resonance at a period duration of 110 s. These findings should be helpful in identifying in detail the mechanisms which are influenced by the geomagnetic field.     

Essay in the classification of morning and evening types of activity in the light of the daily course of autonomically influenced body functions

The present study is an attempt for an objective classification of types of activity by determining the daily periodicity of autonomically influenced body functions. On the basis of a questionnaire, the 23 probands of the test group were classified into morning types (7), evening types (11) and indifferent types (5). Then, for a period of 12h from 07(00) to 18(00), 17 different autonomically influenced parameters were recorded and their mean daily courses calculated separately for the probands of the morning and of the evening type. A comparison of the synchronous values showed that the greatest differences occur between the types at 10(00) and 17(00). At these times of the day, a multidimensional variance and discrimination analysis was carried out which resulted in a very good discrimination of the probands at 10(00) and in a satisfactory one at 17(00). At the same time, an evaluation of the individual parameters recorded was carried out according to their informative value. The most important parameters proved to be the vibration threshold, the R wave height, T wave height, peak time of the pupillogram and d.c. resistance of the skin. On the basis of these results, the classification of 10 probands of an independent test group was effected by a discrimination analysis. In 7 cases this resulted in an agreement with the classification according to the questionnaire.