[Rhizospheric organism under the influence of environmental pollution. II. Physiologic efficiency of the microbial biocenosis in fungicide containing soil (author's transl)].

Abstract

Measuring the potential soil respiration according to the incubator method allows the physiological performance of the celluloytic microflora to be determined. Laboratory tests were carried out to analyse catabolic processes after soil samples had been enriched with native cellulose + fungides. As the temporary capacity of mineralization primarily induced by the substrate invariably gives rise to a substrate-specific "change in position" in the microbial biocenosis, the measured values cannot furnish a parameter for microbiological comparisons of the soil content. Preliminary analyses provided information on the processes of depolymerisation of various C-sources and characterized the celluloysis as well as the order of respiration of its monomer. The rising respiration curve markedly drops off after 12 days, because with the CO2 development at its maximum, total and partial respiration alternate, a phenomenon that was verified in soils incubated with glucose 14C (Keefer and Mortensen, 1963; Macura, 1963; Simonart and Mayaudon, 1958). The test results obtained with fungicide-treated soils (dithiocarbamine acid derivatives) allow the conclusion that the fungicides exercise a varying influence: in the cellulolysis the activity of the cellulase systems is reduced depending on the active substance and concentration, but what is surprising is that respiration is stimulated; this applies to amounts of pesticides being 0.75 and 1.5 times the practical quantity applied. Nor have the "dissociation tests" with cellobiose, which is supposed to be the final link of celluloysis, shown any inhibition of the 1.4--glucodimerase or high respiration values comparable with the glucose metabolism. Tests with cellulases (Cx with dimerase function, Messrs. Roehm and Haas, Darmstadt), which are at present being carried out, are expected to support these observations experimentally. Investigations intended to clarify whether an additional administration of Mn2+ and Fe3+ in the presence of Maneb and Ferbam permits interference with possible adsorption and exchange processes have not yet yielded any generally valid results. The results of the open-field investigations also tend to indicate that the mentioned dithio-carbamates determine the magnitude and the extent of the physiological and CO2-ecological processes to a varying degree; it can be seen that a remarkable "capacity fo compensation" is discernible in the succession of the investigated phases of soil-physiological processes which we tried to clarify.