Summary The diversity of bacterial nitrogenase genes ( nifH ) and their mRNA transcription in ectomycorrhizas of Corsican pine ( Pinus nigra ) were examined. DNA and RNA were extracted from surface‐sterilized and non‐sterilized Corsican pine roots colonized by the ectomycorrhizal (ECM) fungi, Suillus variegatus and Tomentellopsis submollis . DNA‐derived nifH polymerase chain reaction (PCR) products were obtained from all sampl...

Summary Rhizosphere microorganisms play an important role in soil carbon flow, through turnover of root exudates, but there is little information on which organisms are actively involved or on the influence of environmental conditions on active communities. In this study, a 13 CO 2 pulse labelling field experiment was performed in an upland grassland soil, followed by RNA‐stable isotope probing (SIP) analysis, to determine the...

Summary The influence of liming on rhizosphere microbial biomass C and incorporation of root exudates was studied in the field by in situ pulse labelling of temperate grassland vegetation with 13 CO 2 for a 3‐day period. In plots that had been limed (CaCO 3 amended) annually for 3 years, incorporation into shoots and roots was, respectively, greater and lower than in unlimed plots. Analysis of chloroform‐labile C demonstrated...

Summary The influence of soil structure in controlling leaching of Escherichia coli O157:H7 through soil was investigated under controlled conditions using both intact and repacked soil cores. Leaching rates of E. coli O157:H7 decreased with increasing dry bulk density and were significantly increased by the presence of earthworm ( Lumbricus terrestris ) burrows in repacked cores. For intact cores, the percentage of E. coli O1...

The effect of liming on the flow of recently photosynthesized carbon to rhizosphere soil was studied using 13 CO 2 pulse labelling, in an upland grassland ecosystem in Scotland. The use of 13 C enabled detection, in the field, of the effect of a 4‐year liming period of selected soil plots on C allocation from plant biomass to soil, in comparison with unlimed plots. Photosynthetic rates and carbon turnover were higher in plants...

Summary Naturally bioluminescent fungi, Armillaria mellea and Mycena citricolor , were used to develop a novel, bioluminescence‐based bioassay for toxicity testing. Bioassays were carried out to assess the toxicity of 3,5‐dichlorophenol (3,5‐DCP), pentachlorophenol (PCP), copper and zinc. The results suggested that 60 min was a suitable exposure time for the bioassay. Light reduction was observed in response to 3,5‐DCP, PCP an...

Summary Plant responses to increasing atmospheric CO 2 concentrations have received considerable interest. However, major uncertainties in relation to interactive effects of CO 2 with above‐ and below‐ground conditions remain. This microcosm study investigated the impacts of CO 2 concentration on plant growth, dry matter partitioning and rhizodeposition as affected by: (i) photon flux density (PFD), and (ii) growth matrix. Pla...