Die Bedeutung der Zeit

Reflecting on time and its nature has a long tradition in such fields as philosophy, economy and the social sciences. In environmental sciences, however, time has not been taken into sufficient consideration to date, although many ecologists are indeed aware of its importance. Because of the importance of time for mankind, nature and the surrounding world, an outline incorporating time is possible and would lead to new insights in environmental sciences. Here, our idea of a balanced or “healthy” ecosystem, or the consequences of our actions such as depletion of the ozon layer, the greenhouse effect or floods are taken into consideration. A reflection on time its a basic requirement for our understanding of environmental science, its tools and our environmental and political actions. A consideration of time in environmental sciences means, among other things, to think of and to act in accordance with time scales and the rhythms of man and nature.     

Die Zellwand mariner Phanerogamen

When leaf pieces of marine phanerogams (Zostera, Posidonia, Cymodocea, Thallassia, etc.) are exposed to air by hanging them up, they continue to loose weight constantly until they are completely dry; transpiration proceeds without limitation. The leaves shirnk to about 1/5 or 1/6 of their original volume. If the leaves are transferred back into water, their weight increases within a few minutes through rapid water absorption, and may even exceed the initial value. This rapid absorption of water is attributed to the cell walls, which were folded by cohesion tension in the dried state and unfolded through water absorption, thus enlarging the cell lumina and taking up water. Rate of water absorption decreases after bioling the leaves, after repeated drying and subsequent water uptake, and after ageing (about 1 year). Dried leaves of terrestrial plants also increase in weight when immersed in water, however, absorption proceeds 200 to 500 times slower than by marine phanerogams. On the other hand, dried freshwater plants absorb water just as quickly as dried marine plants; but the absorption of water amounts to only a small percent of their initial weight. These facts demonstrate that in this respect marine flowering plants hold a special place. In comparison to the mesophyll cells the very small epidermis cells have a thick cell wall especially on their outside. This wall can be stained darkly with ruthenium-red and, therefore, could possibly consist of pectic substances. When transferred from salt water into freshwater, the leaves absorb water in a matter of seconds; the epidermis walls swell and become rigid; the weight capacity of the leaves doubles (Posidonia) within 1 min. The epidermis cell walls, which swell easily, are responsible for the fact that the cells of many marine algae normally do not plasmolise. On their outside, the epidermis walls are covered with an extremely thin cuticle which can be isolated easily by applying chromic acid. Under the light microscope different species exhibit specific cuticle structures. Under the electron microscope a network of perforations can be seen.     

Die Photosynthehemmung pflanzlicher Protoplasten

The ecotoxicological effect of rain water on the light-dependent, photosynthetical oxygen production of suspended protoplasts from the bean speciesVicia faba L. was used for the characterization of airborne immissions. The protoplast-biotest — with rain water samples taken in an agricultural area from March to July — showed a clear inhibition of the photosynthetical oxygen production. Simultaneously, chemical analyses on some herbicides were carried out. The concentrations determined, however, did not sufficiently explain the measured inhibition of oxygen production; so, the toxicity yielded was assumed to result from not-analyzed compounds as well as synergistic and additive effects of the rain water constituents.     

Die Kosten des Dieselbooms

Background

In many European states the number of cars equipped with diesel engines has dramatically increased since around ten years. This situation is quantified for Germany. Driven by the political motivation to reduce CO₂-emissions, increase of diesel cars has been stimulated by governmental measures of European as well as state bodies in co-operation with the industry.

Results

Reduction of CO₂-emissions with the help of diesel cars remained relatively small. On contrast, diesel cars are emitting much more of nitric oxides and fine particles compared with gasoline driven cars. Excess emissions by the ‘diesel boom’ are quantified. Health costs and impact on agricultural crops as well as on forestry are estimated with respect to the order of magnitude. Health costs caused by the inhalation of diesel combustion particles emitted by only the excess diesel cars in Germany are in the order of 200 Mio Euro per year. Knowledge gaps of the impact of ultra fine particles as well as of the action of particle traps are demonstrated.

Conclusion and Recommendation

In the public, particle numbers need to be discussed instead of particle emission loads (g km^?1) which have an insufficient correlation to health effects. Much more data are needed as to the toxicologically relevant particle size of <20 nm. Effectiveness and sustainability of a CO₂-reduction strategy by diesel cars are generally questioned.     

Die Bedeutung der Zeit

The consideration of time in environmental research allows new insights into the fundamentals of environmental research and new pathways for perceiving and answering questions which might arise in environmental research. In order to take this all into account, one must realize that ecological systems have a history and that both the spatial aspects and the chronological expansion of these systems must be taken into consideration. Considering temporalities, rhythms and time scales as well as their interdependencies in environmental research and environmental protection enables us to obtain a better understanding. The significance of relationships and functions in ecological systems can be perceived better as well. The impact of pollutants as well as the outcome of human actions in ecology, and in economics and politics, is consequently mandatory for not only a spatial, but also for the involved temporal scales.