University of Hohenheim

About: University of Hohenheim is a education organization based out in Stuttgart, Germany. It is known for research contribution in the topics: Population & Soil water. The organization has 8585 authors who have published 16406 publications receiving 567377 citations.

Standard methods for varroa research

Abstract: SummaryVery rapidly after Varroa destructor invaded apiaries of Apis mellifera, the devastating effect of this mite prompted an active research effort to understand and control this parasite. Over a few decades, varroa has spread to most countries exploiting A. mellifera. As a consequence, a large number of teams have worked with this organism, developing a diversity of research methods. Often different approaches have been followed to achieve the same goal. The diversity of methods made the results difficult to compare, thus hindering our understanding of this parasite. In this paper, we provide easy to use protocols for the collection, identification, diagnosis, rearing, breeding, marking and measurement of infestation rates and fertility of V. destructor. We also describe experimental protocols to study orientation and feeding of the mite, to infest colonies or cells and measure the mite's susceptibility to acaricides. Where relevant, we describe which mite should be used for bioassays since their beha...

Structure and function of the soil microbial community in microhabitats of a heavy metal polluted soil.

Abstract: Particle-size fractionation of a heavy metal polluted soil was performed to study the influence of environmental pollution on microbial community structure, microbial biomass, microbial residues and enzyme activities in microhabitats of a Calcaric Phaeocem In 1987, the soil was experimentally contaminated with four heavy metal loads: (1) uncontaminated controls; (2) light (300 ppm Zn, 100 ppm Cu, 50 ppm Ni, 50 ppm V and 3 ppm Cd); (3) medium; and (4) heavy pollution (two- and threefold the light load, respectively) After 10 years of exposure, the highest concentrations of microbial ninhydrin-reactive nitrogen were found in the clay (2–01 μm) and silt fractions (63–2 μm), and the lowest were found in the coarse sand fraction (2,000–250 μm) The phospholipid fatty acid analyses (PLFA) and denaturing gradient gel electrophoresis (DGGE) separation of 16S rRNA gene fragments revealed that the microbial biomass within the clay fraction was predominantly due to soil bacteria In contrast, a high percentage of fungal-derived PLFA 18 : 2ω6 was found in the coarse sand fraction Bacterial residues such as muramic acid accumulated in the finer fractions in relation to fungal residues The fractions also differed with respect to substrate utilization: Urease was located mainly in the phosphatase >urease >xylanase Heavy metal pollution did not markedly change the similarity pattern of the DGGE profiles and amino sugar concentrations Therefore, microbial biomass and enzyme activities seem to be more sensitive than 16S rRNA gene fragments and microbial amino-sugar-N to heavy metal treatment

Distribution and function of proteoid roots and other root clusters

Abstract: Proteoid roots are bottlebrush-like clusters of rootlets which form along lateral roots. They are characteristic of most species of the Proteaceae, which are mainly distributed in Australia and South Africa. Homologous root clusters are present in species of the Casuarinaceae, Mimosaceae, Fabaceae, Myricaceae and Moraceae. Many similarities exist between these species in relation to morphology and function of root clusters. Many are non-mycorrhizal and are highly efficient in phosphorus (P) acquisition. In these species, proteoid roots and proteoid-like root clusters are abundant when grown on infertile soils. Their formation is predominantly affected by the P status of the plants, being induced at low P levels and repressed at high P levels. Proteoid roots and proteoid-like root clusters play an important role in acquisition of P and other mineral nutrients. Although increase in root surface area may be a contributing factor, in many species these roots excrete large amounts of organic acids and phenolics. The excretion of these compounds in a small soil volume gives rise to extensive nutrient mobilization by acidification, reduction and chelation of sparingly soluble forms of P and micronutrients such as Fe and Mn.