Influence of microbial activity and soil moisture on herbicide immobilization in soils

Mobility, extractability, and disappearance of the herbicides diuron, terbuthylazine, metolachlor, and pendimethalin were examined in incubation experiments with two topsoil samples of different natural microbial activity and after sterilization. Soil moisture was held constant at 10, 40, and 60 % WHC. In other variants, the soil water content was changed during the incubation. The four herbicides reveal a fairly different extent of microbial and chemical degradation and immobilization. The herbicide mobility – expressed by coefficients of partition between adsorbed and dissolved herbicide amounts – decreases at a lower rate and extent, when the microbial activity is low or the soil is sterile. With increasing initial soil moisture, also herbicide mobility and extractability increase; but in the course of time, abiotic immobilization occurs to a higher extent. When soil moisture changes during the incubation, formerly non‐extractable herbicide fractions (up to 40 % of the applied amounts) become extractable. Kinetics of herbicide immobilization follow an empirical sigmoidal function, which describes three periods of immobilization. The three‐period shape of the curve and its possible reasons are discussed for the data of the incubation experiments as well as for the results of a long‐term field trial with diuron.     

Structural stability and prebiotic properties of resistant starch type 3 increase bile acid turnover and lower secondary bile acid formation

Microbial metabolism is essential in maintaining a healthy mucosa in the large bowel, preferentially through butyrate specific mechanisms. This system depends on starch supply. Two structurally different resistant starches type 3 (RS3) have been investigated with respect to their resistance to digestion, fermentability, and their effects on the composition and turnover of bile acids in rats. RSA (a mixture of retrograded maltodextrins and branched high molecular weight polymers), which is more resistant than RSB (a retrograded potato starch), increased the rate of fermentation accompanied by a decrease of pH in cecum, colon, and feces. Because they were bound to RS3, less bile acids were reabsorbed, resulting in a higher turnover through the large bowel. Because of the rise of volume, the bile acid level was unchanged and the formation of secondary bile acids was partly suppressed. The results proved a strong relation between RS3, short chain fatty acid production, and microflora. However, butyrate specific benefits are only achieved by an intake of RS3 that result in good fermentation properties, which depend on the kind of the resistant starch structures.     

Mikrosonden- und Röntgenbeugungs-Untersuchungen an Tonbelägen von lessivierten Böden aus Löß

Microprobe and x-ray diffraction studies of clay coatings in leached soils derived from loess Point analyses of Si, Al, K, Mg, Ca, Fe, Mn, as well as of Zn and Pb of clay coatings in soil thin sections from illuvial horizons of four leached soils were carried out using an electron microprobe (EMA). The K, Mg, Si, and Al content, the Si/Al-molar ratio of coatings and XRD-analyses indicate that the clay coatings consist mainly of illitic clay minerals. This suggests either a mineral-specific displacement of illite or the formation of illitic clay coatings from migrated smectite or expanded illite (“illitization”) through subsequent K uptake. The clay coatings show, with the exception of Fe, Mn, Zn and Pb, only little variation in their chemical composition within the same horizon. Between the horizons of the investigated soils, however, distinct differences in the total element content, especially in the K content may occur. The strong vertical variation of the K content in clay coatings in some horizons is probably due to acidic conditions and lateral infiltration which lead to an increased weathering of illite and the depletion of K. The EMA results show that Pb is predominantly bound in Fe-Mn-Oxide coatings on the surface of clay minerals or in Fe-Mn-Oxide precipitates within clay coatings. Microanalyses of K depleted clay coatings indicate on the other hand an increased fixation of Zn in expanded illites.     

Inoculation of cereal crops and forage grasses with nitrogen-fixing rhizosphere bacteria: Possible causes of success and failure with regard to yield response – a review

Recent field inoculation trials with Azospirillum and Azotobacter spp. applied to cereal and forage crops have shown extremely different results in yield response. Some aspects of bacteria-plant interactions affecting yield response are discussed. These include provision of fixed nitrogen, specificity and adaptation to root habitat, influence of microbial metabolites, enhancement of VA-mycorrhiza, displacement of deleterious rhizosphere microorganisms, differences between host plant genotypes, competitive ability and longevity of inoculants. Based on these considerations, needs for further research will be outlined.     

Resistenzeigenschaften im Gersten- und Weizensortiment Gatersleben 25. Prüfung von Gersten auf ihr Verhalten gegenüber Gerstengelbmosaik-Virus (barley yellow mosaic virus)

Zusammenfassung Die Pflanzen der geprüften Gersten wurden durch Preßsaftabreibung mit dem Gerstengelbmosaik-Virus (barley yellow mosaic virus, BaYMV) inokuliert. Die meisten Sippen reagierten mit Virussymptomen und mußten als anfällig beurteilt werden (Tab. 1). Die nachgewiesenen resistenten Sippen (Tab. 2) können die genetische Basis der Virusresistenz in der Züchtung verbreitern.

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Resistance in the Gatersleben barley and wheat collection. 25. Testing of barley for reaction to barley yellow mosaic virus (BaYMV)

Summary Plants of the tested barley strains were infected by sap inoculation with barley yellow mosaic virus (BaYMV). Most of the barleys were classified as susceptible (table 1). The resistant strains (table 2) can be used to expand the genetic basis of BaYMV resistance in breeding.

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. 25. ë (barley yellow mosaic virus)

ë (barley yellow mosaic virus, BaYMV). (. 1). (. 2) .

     

Resistenzeigenschaften im Gersten- und Weizensortiment Gatersleben 28. Prüfung von Gersten auf ihr Verhalten gegenüber den BlattlausartenRhopalosiphum padi (L.) undMacrosiphum (Sitobion) avenae (F.)

Zusammenfassung Unter den geprüften Saatgersten (Hordeum vulgare L.) wurden sechs Muster mit Resistenz gegenRhopalosiphum padi (L.) — Resistenz-Indices 4,45 bis 10,10 — und sieben Muster mit Resistenz gegenMacrosiphum (Sitobion) avenae (F.) — Resistenz-Indices 3,20 bis 8,00 — gefunden. MitHordeum turkestanicum Nevski undH. bogdani Wilenski — Resistenz-Indices gegenR. padi 8,45 bzw. 4,96, gegenM. avenae 8,09 bzw. 3,47 — konnten zwei Arten mit Resistenzeigenschaften gegen beide Aphidenarten gefunden werden.

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Resistance in the Gatersleben barley and wheat collection. 28. Reaction of barleys to cereal aphidsRhopalosiphum padi (L.) andMacrosiphum (Sitobion) avenae (F.)

Summary Among the tested barleys (Hordeum vulgare L.) six of the accessions showed resistance toRhopalosiphum padi (L.) — resistance-indices from 4.45 to 10.0-and seven toMacrosiphum (Sitobion) avenae (F.)—resistance-indices from 3.20 to 8.00. The speciesHordeum turkestanicum Nevski andH. bogdani Wilenski-resistance-indices toR. padi 8.45 and 4.96, respectively—and toM. avenae 8.09 and 3.47, respectively—showed resistance characters to both of the aphids.

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. 28. Rhopalosiphum padi (L.) Macrosiphum (Sitobion) avenae (F.)

(Hordeum vulgare L.) Rhopalosiphum padi (L.) — 4,45 10,10; Macrosiphum (Sitobion) avenae (F.) — 3,20 8,00. Hordeum turkestanicum Nevski H. bogdani Wilenski ( R. padi 8,45 4,96, M. avenae 8,09 3,47) .

     

Localization of fractionally charged quasi-particles

An outstanding question pertaining to the microscopic properties of the fractional quantum Hall effect is understanding the nature of the particles that participate in the localization but that do not contribute to electronic transport. By using a scanning single electron transistor, we imaged the individual localized states in the fractional quantum Hall regime and determined the charge of the localizing particles. Highlighting the symmetry between filling factors 1/3 and 2/3, our measurements show that quasi-particles with fractional charge e* = e/3 localize in space to submicrometer dimensions, where e is the electron charge.     

Observation of giant diffusivity along dislocation cores

Diffusion of atoms in a crystalline lattice is a thermally activated process that can be strongly accelerated by defects such as grain boundaries or dislocations. When carried by dislocations, this elemental mechanism is known as "pipe diffusion." Pipe diffusion has been used to explain abnormal diffusion, Cottrell atmospheres, and dislocation-precipitate interactions during creep, although this rests more on conjecture than on direct demonstration. The motion of dislocations between silicon nanoprecipitates in an aluminum thin film was recently observed and controlled via in situ transmission electron microscopy. We observed the pipe diffusion phenomenon and measured the diffusivity along a single dislocation line. It is found that dislocations accelerate the diffusion of impurities by almost three orders of magnitude as compared with bulk diffusion.