Wechselwirkungen zwischen Boden-Huminstoffen und Metall-Ionen I. Isolierung und Charakterisierung der Boden-Huminstoffe

Interactions between soil humic substances and metal ions I. Isolation and characterization of the soil humic substances From two horizons of a podzol humic acids and fulvic acids were isolated by two different methods. The obtained samples were characterized by elemental analysis, the determination of the ash and moisture content, functional group analysis as well as FTIR-, ¹H-NMR-, and ¹³C-NMR-spectroscopic examinations. In spite of the different isolation methods humic and fulvic acids show great similarities. A higher oxidized state and a lower content of aromatic structural features are clearly observed in the fulvic acids in contrast to humic acids. Besides aromatic structural elements, distinct aliphatic sections were detected in the investigated samples, which showed a lower concentration in the less transformed fractions of the Ahe-horizon.     

Wechselwirkungen von Huminstoffen mit Peptiden

Interactions of Humic Substances with Peptides By means of the model reaction of p-benzoquinone with a number of peptides it has been shown that electron donor acceptor complexes between the reactants are formed. This mechanism could be verified by spectroscopic measurements and gas exchange investigations. The takings of differential spectra in the ultraviolett region are showing modifications which are caused by the reaction of the peptides with the humic substances of a peaty soil. They are traced back to the enlarged dissociation of the phenolic hydroxyl of the L-tyrosyl-glycine, which is caused by the formation of the charge transfer complexes with the humic substances. By gel permeation chromatography in equilibrium state the binding of peptides to the humic substances is verified and quantitative statements are possible.     

Wechselwirkungen von Huminstoffen mit Aminosäuren

Interaction of Humic Acid with Amino Acids By means of the charge-transfer complexes between p-benzoquinone and a number of amino acids, this possible mechanism of the reaction of humic acids with amino acids has been pointed out in principle. The mechanism has been confirmed for the humic acids by the absorption spectra in the ultraviolett and visible range and an increase of the dissoziation of the phenolic hydroxyl of the tyrosine molecule. The quantitative aspect of this binding has been dealt with by gelfiltration in a state of equilibrium. 70 μmol of tyrosine were found to be bound by one gram of a synthetic humis acid.     

Beziehung zwischen Kationen/Anionen-Aufnahme von Rotklee und Protonenabscheidung der Wurzeln

Relationship between the cation/anion uptake and the release of protons by roots of red clover Red Clover was cultivated in Mitscherlich pots on a brown podzolic soil. Besides a low N rate at the beginning of the experiment, the clover received only symbiontically fixed N. Soil pH dropped under clover from 7.2 to 4.5 during a period of 14 months. During this time seven cuts were obtained. In a parallel pot experiment with rye-grass grown on the same soil and under the same environmental conditions but supplied with NH₄NO₃ after each clipping, no drop in soil pH was observed. In the aerial plant parts of clover the cation excess was high and amounted to about 60 % of the H⁺ quantity required for the decrease in soil pH from 7.2 to 4.5. It is concluded that the cations taken up in excess were electrostatically balanced by an equivalent amount of protons secreted by the roots into the soil. The alcalinity assessed in the upper plant parts of clover was approximately equivalent to the cation excess. It is therefore supposed that the H⁺ release from roots resulted in an alkalinization in the plant cells which in return led to a synthesis of organic anions being equivalent to the amount of H⁺ released.     

Wechselwirkungen von Mikroorganismen und Tonmineralen-eine Übersicht

Relationships Between Soil Microorganisms and Clay Minerals-a Review Clay minerals belong to the most important environmental factors in soils, influencing the composition and metabolic activity of soil microflora. Their influence on bacteria, actinomycetes and microscopic fungi is very complex and includes trophogenic relationships, cation exchange capacity, sorptive activity, osmotic and other physico-chemical effects in microbial environments. In this review, different effects of clay minerals on soil microorganisms and also the influence of microorganisms on the clay minerals are briefly discussed.     

Eine Kombination der Thermogravimetrie mit der 15N-Tracertechnik zur Untersuchung von Huminsäurepräparaten

A combination of thermal analyses and ¹⁵N tracer technique for investigation of humic acids Differences in humic acids of two extreme variants of three long-term trials due to a three years intensive fertilization in a pot experiment are also to be found by means of thermogravimetry. Additionally the ¹⁵N contents of humic acids were investigated at certain temperatures according to the peaks given by thermogravimetric study. The ¹⁵N isotope is also incorporated in higher molecular compounds. The ¹⁵N content varies due to differences in humus content and composition of the soils used.     

Beziehung zwischen dem Stickstoff-Entzug der Pflanzen und der Abnahme von spezifisch gebundenem NH4-N im Boden

Relationship between the N uptake of plants and the mobilization of nonexchangeable NH₄-N In a pot experiment with ryegrass (Lolium multiflorum) the relationship between the release of nonexchangeable NH₄⁺ and the N uptake of plants was studied. For this purpose the surface soil of an alluvial soil and of a grey brown podsolic soil was labelled with ¹⁵NH₄-N. The following results were obtained: After treating the soil with 15-N the alluvial soil contained 4,55 mg and the grey brown podsolic soil 1,64 mg nonexchangeable ¹⁵NH₄-N/100 g soil. In the alluvial soil 72% and in the grey brown podsolic soil 66% of the nonexchangeable ¹⁵NH₄⁺ had been released during the growing season when ryegrass was planted. However, without plants there was no change in the content of labelled nonexchangeable NH₄⁺ in the alluvial soil or only a slight decrease in the grey brown podsolic soil. A highly significant correlation was found between the ¹⁵NH₄-N released and the ¹⁵N uptake of ryegrass in the alluvial soil (r = 0,78⁺⁺⁺) as well as in the grey brown podsolic soil (r = 0,98⁺⁺⁺).     

Stickstoff-Assimilation in der Wurzel und Transport von N-Verbindungen mit dem Blutungssaft der Wurzeln in Abhängigkeit von der Mn-Versorgung

Nitrogen Assimilation in Roots and the Transport of Nitrogen Compounds in the Bleeding Sap of Roots in relation to Manganese Nutrition. The assimilation of nitrogen in the roots of 27 days old pumpkin plants was examined in relation to manganese nutrition. The transport of nitrogen compounds in the xylem was determined in roots and in the bleeding sap of roots using nitrate as the N-source. The maximum NO₃ content in the roots was observed in the Mn treatment which resulted in the highest shoot yields (0.05 ppm Mn). The bleeding sap of this treatment was lowest in nitrate concentration, but showed the highest rate of transport of organic nitrogen compounds. In experiments with ¹⁵N in the nutrient solution the isotope was found in the roots in organic and in inorganic compounds. The composition of the fraction of free amino acids differed between roots and xylem sap. In the bleeding sap glutamine was especially dominant. In the roots the amino acid composition depended on the extent of Mn-supply. Lowest glutamine concentrations were found in the xylem sap from the treatment with maximum shoot yields. A numerical difference was found in the xylem sap between organic N (N_(org)) and the amino acid nitrogen. This difference which account for more than 50 % of the organically bound nitrogen is suggested to be made up in part by low molecular weight peptides, amino sugars and other compounds. In Mn deficiency a general reduction in the intensity of nitrogen metabolism was found. With Mn toxicity the N assimilation activity was more intensive than for the low Mn supply. Simultaneously, however, the transport of organic N compounds from the root was lower.     

Zusammenhang zwischen hydraulischer und mechanischer Bodenstabilität in Abhängigkeit von der Belastungsdauer

Interaction between mechanically and hydraulically affected soil strength depending on time of loading Soil‐deformation analysis often only considers the direct effects of mechanical stress on changes in void ratio or pore functions while the interaction between hydraulic and mechanical processes is seldomly mentioned. Thus, we analyzed the effect of mechanical stress and time of soil settlement on changes in soil strength and the corresponding interactions between stress‐dependent changes in pore water pressure on precompression stress for a clayey silt. Disturbed samples with a bulk density of 1.4 g cm^–3 and a water content of 25 g (100 g)^–1 were compressed for four time steps (10–240 min) at eight stresses (20–400 kPa) with four replications. During the experiments, the changes of pore water pressure and void ratio were registered. With increasing time of stress application, we determined an increased soil strain. The higher the stress‐application time, the smaller gets the void ratio and the precompression stress value. Parallel to these variations in settlement, we also found changes in the pore‐water‐pressure values. This is a consequence of decreasing pore diameter while the water saturation increases. Thus, the proportion of neutral stresses on total stress increases which coincides with a change of water suction (= unsaturated) conditions up to even positive pore‐water‐pressure values (from less negative to positive pore water pressure values). From our experiments, we can conclude that the changes in pore‐water‐pressure values already occur at normal stress values smaller than the precompression stress. This underlines the increasing sensitivity of soil deformation processes close to the internal soil strength. The results support the idea, that in order to quantify the mechanical strength of structured unsaturated soils, we always have to determine the changes in pore‐water‐pressure values, too.     

Bedeutung der Kalium-Verarmung in der Rhizosphäre und der Tonminerale für die Freisetzung von nichtaustauschbarem Kalium und dessen Bestimmung mit HCl

Significance of K-depletion in the rhizosphere and clay minerals for the release of nonexchangeable potassium and its determination with HCl Experiments were carried out with four different soils (basaltic soil, C-horizon of a keuper, sea alluvium, and a podsolic brown earth from loess) to investigate whether the fractions of exchangeable K and HCl-soluble nonexchangeable K are decreased in root vicinity by the K uptake of ryegrass (Lolium perenne). After a growth period of 70 days with five cuts distinct K depletion profiles were obtained showing that in the direct vicinity of the root the decrease in exchangeable K was the most pronounced. The K depletion in this fraction extended to 2 cm distance from the root zone. Also the concentration of HCl-soluble nonexchangeable K of the interlayers was decreased in root vicinity. It is assumed that the decrease in K concentration in soil solution is a prerequisite for the net release of interlayer K. The decrease in exchangeable K plus HCl soluble nonexchangeable K was equal to the amount of K taken up by the grass from the basaltic- and the alluvial soil. In the case of the podsolic brown earth and the keuper soil, however, much more K was taken up by the grass than was found in the decrease of exchangeable K plus HCl soluble nonexchangeable K. It is assumed that in these two soils the fraction of the HCl soluble K was more altered by the expansion of interlayers during the growth of rye-grass. The net release of interlayer K was neither related to the concentration of exchangeable K, HCl-soluble non-exchangeable K, the K fixation power nor the clay concentration. It is supposed that the net release of interlayer K also depends on clay mineral characteristics.     

Die Böden von Wallhecken in Schleswig-Holstein. II. Aufbau und Umsetzung der organischen Bodensubstanz

Soils of Mound Hedges in Schleswig-Holstein. II. Composition and Transformation of Soil Organic Matter Two Cumulic Anthrosols of mound hedges and the fossil A-horizons below the deposits, were investigated by means of wet chemistry and ¹³C-NMR spectroscopy in order to characterize soil organic matter (SOM) and to compare their SOM with natural and recent soils. The bulk humus of the Cumulic Anthrosols contains a high amount of easily soluble polysaccharides. Despite their high bioavailability sugars, starch and mobile fulvic acids are not completely consumed by microorganisms and translocated into the subsoil. The initial phase of podzolization is indicated due to this process and the very low pH-level of the soils. After deposition about 30 % of the soil carbon in the A-horizons is mineralized. Litter compounds are predominantly decomposed, whereas humic compounds are selectively preserved or newly synthesized. The significance of the humic compounds in the soil organic matter increases after deposition. This is why the potential cation exchange capacity of the fossil Ahorizons is similar to this of the recent ones.     

Zur Untersuchung der verschiedenen Formen von Chlorophyll in der lebenden Pflanze durch Anwendung der Derivativ-Spektrophotometrie

Zusammenfassung Die Anwendung der Derivativ-Spektrophotometrie ermöglicht eine bessere Auflösung der sich sehr stark überlagernden Absorptionsbanden der verschiedenen Chlorophyll a-Formen in vivo im Vergleich zur üblichen spektroskopischen Technik. Untersuchungen von Gleichungen zur Beschreibung der Form von Absorptionsbanden und ihren 1. und 2. Ableitungen führen zu dem Ergebnis, daß sich durch die Differentiation die Halbwertsbreite verringert und damit das Auflösungsvermögen erhöht. Die 2. Ableitung zeigt sich dabei der 1. Ableitung überlegen.Apparative Möglichkeiten für die direkte Registrierung differenzierter Absorptionskurven werden untersucht. Unter Anwendung eines dabei auftretenden einfachen Prinzips wurde eine Apparatur gebaut, mit der neben der Extinktion und ihrer 1. Ableitung auch die 2. Ableitung nach der Wellenlänge registriert werden kann, die bisher nicht für Untersuchungen der Blattpigmente herangezogen wurde.Einige mit diesem Gerät aufgezeichnete Spektren demonstrieren die Vorteile der Derivativ-Spektrophotometrie, insbesondere für die Untersuchung der photosynthetischen Pigmente in vivo.

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Summary The strongly overlapping absorption bands of chlorophyll a forms in vivo are better resolved by derivative spectrophotometry than by ordinary absorption spectra. It was possible to demonstrate by eximation of equations describing the form of absorption bands and their first and second derivatives, that the half width of an absorption band is reduced by differentiation and therefore the resolving power is increased. The second derivative is shown to be superior to the first one.By examining apparative possibilities for recording directly differentiated absorption curves a simple principle was found, according to which an apparatus was constructed, that allows to record the direct absorbance spectrum, its first and its second derivative.Till now the second derivative of the absorption spectrum is not used for studying the leaf pigments.Some spectra, recorded with this apparatus, demonstrate the advantages of derivative spectrophotometry, especially for analysing photosynthetic pigments in vivo.

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