Wolfgang Wiehe

Plant growth stimulation by inoculation with symbiotic and associative rhizosphere microorganisms

SelectedRhizobium bacteria, arbuscular mycorrhiza-forming (AM) fungi and associative bacteria have been shown to stimulate the growth of legumes, gramineae and cruciferae in field experiments on different soil types in temperate regions. A combination of microorganisms with different metabolic capacities (N2-fixation, P-mobilization; production of phytohormones and antibiotics) can partly surpass the effect of single inoculations, or can produce a positive effect where single inoculations are ineffective. Growth stimulation by inoculation requires microorganisms with phytoeffective metabolic characteristics and the ability to survive in the rhizosphere during the growth period. Another prerequisite is an adequate supply of plant assimilates for the production of microbial phytoeffective metabolites. Type of inoculum, method of inoculation and agricultural measures can influence the effect of the inoculation. Research is necessary to extend our knowledge both of basic principles, and about using microorganisms in practice.

Rhizosphere colonization of different crops with growth promoting Pseudomonas and Rhizobium bacteria

Abstract Selected plant growth promoting Pseudomonas and Rhizobium bacteria colonized after inoculation the rhizosphere of wheat, maize, rape, oil radish, pea, alfalfa, and sugar beet in pot experiments. They were not able to move into the phyllosphere. The rate of migration in non-rooted soil was very small. The survival of inoculated bacteria, especially in deeper soil layers, was favoured be seed inoculation in combination with peat as carrier. Soil types (loamy sand, sandy loam, chernozem) had different effects on the strain specific colonization of the crops. No clear relations could be found between the amount of bacterial colonization and growth stimulation effect.

Survival of plant growth promoting rhizosphere bacteria in the rhizosphere of different crops and migration to non-inoculated plants under field conditions in north-east Germany

Abstract Survival of two plant-growth-promoting bacteria, Pseudomonas fluorescens PsIA12 and Rhizobium trifolii R39 (rifampicin-resistant mutants), was studied in the rhizosphere of different crops in field experiments on loamy sand in the years 1993 and 1994 (Muncheberg, Germany). After seed inoculation with a peat formulation the Rhizobium strain colonized the rhizosphere of pea and white lupin as well as that of the non-legumes maize, wheat and rape. While the Rhizobium strain established more or less stable populations during the whole vegetation time, the population of the Pseudomonas strain increased with the vegetative plant development and declined with flowering and maturing of the legumes. In the maize rhizosphere this strain was reisolated only in numbers lower log 3 cfu · g root -1 . Both strains were able to establish small populations up to log 4.8 cfu · g root -1 in the rhizosphere of non-inoculated crops and weeds up to 0.6 m away from inoculated plants.

Membrane properties change in fine-pore aeration diffusers: Full-scale variations of transfer efficiency and headloss

Fine-pore diffusers are the most common aeration system in municipal wastewater treatment. Punched polymeric membranes are often used in fine-pore aeration due to their advantageous initial performance. These membranes are subject to fouling and scaling, resulting in increased headloss and reduced oxygen transfer efficiency, both contributing to increased plant energy costs. This paper describes and discusses the change in material properties for polymeric fine-pore diffusers, comparing new and used membranes. Three different diffuser technologies were tested and sample diffusers from two wastewater treatment facilities were analysed. The polymeric membranes analysed in this paper were composed of ethylene-propylene-diene monomer (EPDM), polyurethane, and silicon. Transfer efficiency is usually lower with longer times in operation, as older, dilated orifices produce larger bubbles, which are unfavourable to mass transfer. At the same time, headloss increases with time in operation, since membranes increase in rigidity and hardness, and fouling and scaling phenomena occur at the orifice opening. Change in polymer properties and laboratory test results correlate with the decrease in oxygen transfer efficiency.

Establishment of plant growth promoting bacteria in the rhizosphere of subsequent plants after harvest of the inoculated precrops

Abstract Rifampicin-resistant mutants of two plant-growth-promoting rhizosphere bacteria, Pseudomonas fluorescens strain PsIA12 and the associative, non-symbiotic Rhizobium leguminosarum bv. trifolii strain R39, were inoculated with different crops in field experiments. Soil from these sites was collected after harvest. Non-inoculated maize, pea, lupine and two weeds (Amaranthus retroflexus, Echinochloa crus-galli ) were subsequently grown in this soil in the greenhouse and tested for colonization with Pseudomonas strain PsIA12 and Rhizobium strain R39. The Rhizobium strain was able to re-establish in the rhizosphere of the plants without nodulation in between, even after dry storage of the soil up to 12 months. It could even colonize a second subsequent plant generation. Highest cell numbers were detected in legumes (mean value log 5.0 cfu · g root -1 ), followed by maize (log 4.3 cfu · g root -1 ) and the weeds ( -1 ). Rhizosphere colonization was modified by the inoculated precrop. The Pseudomonas strain was not able to re-establish cell numbers higher log 3.0 cfu · g root -1 in the rhizosphere.

Einfluss assoziativer rhizosphärenbakterien auf die äHrstoffaufnahme und den Ertrag von Mais

In mehrjahrigen Feldversuchen (1990–1995) in Nordostdeutschland wurde der Einflus selektierter assoziativer Rhizospharenbakterien auf den Ertrag und die Nahrstoffaufnahme bei Mais untersucht. Der Trockenmasse‐ und Kolbenertrag zur Siloreife bzw. der Samenertrag wurde durch die Bakterienstamme Pseudomonas fluorescens (PsIA12), Agrobacterium rhizogenes (A1A4), Rhizobium trifolii (R39) und z.T. durch Stenotrophomonas maltophilia (PsIB2) in den Jahren 1990 bis 1995 auf lehmigen Sandboden wiederholt signifikant, auf sandigem Lehm zum Teil signifikant erhoht. Maissorten konnen unterschiedlich auf die Bakterieninokulation reagieren. Die Bakterien stimulierten insbesondere bei Jungpflanzen die Wurzelentwicklung und die Nahrstoffaufnahme (N, P, K) aus dem Boden. Sie bildeten Phytohormone (Auxine und z.T. Cytokinine) und uberlebten, auch unter Feldbedingungen, im Rhizospharenraum von Mais wahrend der gesamten Vegetation.

An improved method of sperm selection by glass wool filtration

Summary.  An improved method of sperm selection by glass wool filtration is introduced. After incubation of glass wool filtrates for 30 min at 37 °C in a conical‐shaped 1.5‐ml tube, an enrichment of highly motile spermatozoa was found in the bottom layer of the tube. The effect turned out to be dependent on the conical shape of the tube, as it was not observed in flat‐bottomed tubes. Native ejaculates (obtained from 30 men) and their glass wool filtrates were analysed by cell counter, computer‐assisted sperm‐motility analysis, morphological differentiation and supravital staining of spermatozoa. When 400 µl of ejaculate, diluted with 800 µl of medium, was applied to the top of a column consisting of a 1‐ml disposable syringe barrel gently packed with 15 mg of glass wool to a depth of 6 mm, an enrichment of viable spermatozoa was found in the first three 100‐μl fractions taken from the bottom of the tube. It is the simplicity of this technique that makes it so easily applicable.

Möglichkeiten zur Beeinflussung von Pflanzen-Mikroorganismen-Interaktionen in Böden von Bergbaufolgelandschaften

Der grosflachige Abbau von Braunkohle fuhrt infolge unkontrollierter Bodenverlagerung zur total en Zerstorung naturlicher Okosysteme und zu erhohter Erosion insbesondere auf den Hangflachen. Es werden nicht nur die Pflanzen- und Tiergesellschaften in Mitleidenschaft gezogen, es findet auch eine Verarmung und Veranderung der nativen Mikroorganismengesellschaften gegenuber gewachsenen Kulturboden statt (Schumacher et al. 1990, Huttl et al. 1994).

Etablierung und Überlebensfähigkeit Inokulierter Pflanzenwachstums-Stimulierender Bakterien in der Rhizosphäre von Leguminosen, Mais und Wildpflanzen Unter Freilandbedingungen

Die Etablierung von inokulierten, potentiell wachstumsfordernden Bakterien im sich entwickelnden Wurzelsystem ist eine Grundvoraussetzung fur die Wachstumsforderung der Pflanzen in situ. Als mogliche Wirkprinzipien fur mikrobielle Pflanzenwachstumsforderung werden diskutiert: Erschliesung von Nahrstoffen (Luftstickstoff, Phosphat), Phytohormonwirkungen und Produktion antagonistisch wirkender Substanzen gegen andere (pathogene) Mikroorganismen (Kloepper et al. 1989, Jagnow et al. 1991). Alle diese Mechanismen konnen nur durch einen intensiven Kontakt zwischen Bakterien und Wurzeln zum Tragen kommen (Wiehe et al. 1994). Die Interaktionen zwischen den Partnern konnen mikroorganismen- und pflanzenspezifisch differieren.