A new species of Stenobiella Tillyard (Neuroptera, Berothidae) from Australia

Stenobiella variola sp. n., a new species of beaded lacewing (Neuroptera: Berothidae), is described and figured from south-eastern Australia. A preliminary key to Stenobiella species is presented

Application of nitrogen fertilizer to a boreal pine forest has a negative impact on the respiration of ectomycorrhizal hyphae

Aims: There is evidence that increased N inputs to boreal forests, via atmospheric deposition or intentional fertilization, may impact negatively on ectomycorrhizal (ECM) fungi leading to a reduced flux of plant- derived carbon (C) back to the atmosphere via ECM. Our aim was to investigate the impact of N fertilization of a Pinus sylvestris (L.) forest stand on the return of recently photoassimilated C via the ECM component of soil respiration. Methods: We used an in situ, large-scale, 13C-CO2 isotopic pulse labelling approach and monitored the 13C label return using soil gas efflux chambersplaced over three different types of soil collar to distinguish between heterotrophic (RH), autotrophic (RA; partitioned further into contributions from ECM hyphae and total RA) and total (RS) soil respiration. Results: The impact of N fertilization was to significantly reduce RA, particularly respiration via extramatrical ECM hyphae. ECM hyphal flux in control plots showed substantial spatial variability, resulting in mean flux estimates exceeding estimates of total RA, while ECM contributions to RA in N treated plots were estimated at around 30%. Conclusion: Significant impacts on soil C cycling may be caused by reduced plant C allocation to ECM fungi in response to increased N inputs to boreal forests; ecosystem models so far lack this detail

The influence of external nitrogen on carbon allocation to Glomus intraradices in monoxenic arbuscular mycorrhiza

The influence of external nitrogen (N) on carbon (C) allocation and processes related to phosphorus (P) metabolism were studied in monoxenic arbuscular mycorrhiza (AM) cultures of Daucus carota. Fungal hyphae of Glomus intraradices proliferated from colonized roots growing on solid medium into C-free liquid minimal medium with two different N and P levels. Furthermore, we exposed the colonized roots to high or low N availability and then studied the mycelial development. Roots were provided with C-13-glucose in order to follow the C allocation. The mycelium was analysed for phosphatase activity and transcription levels of two nutrient regulated genes. High N availability to the monoxenic AM root reduced the C allocation to the AM fungus while N availability to the mycelium was important for the upregulation of the fungal inorganic phosphorus (Pi)-transporter GiPT. We found that N availability can regulate nutritional processes in arbuscular mycorrhiza. We conclude that negative impacts of N on AM abundance are caused by reduced C allocation from the plant. Upregulation of the fungal Pi-transporter GiPT indicated that increased N availability might induce P limitation in the mycelium

Effects of varied soil nitrogen supply on Norway spruce (Picea abies [L.] Karst.). Pt. 1 and 2 Shoot and root growth and nutrient uptake. Carbon metabolism in needles and mycorrhizal roots

Model experiments were carried out over a period of 3 years to investigate the effect of a variation of nitrogen supply on shoot and root growth, on the uptake of mineral elements, and on carbon allocation in Norway spuce including the formation of mycorrhizal symbiosis. Seedlings were maintained under different light intensities, and nutrients were added either to the total soil volume or only to a discrete soil patch. Increased N-supply effects carbon metabolism by a higher demand for C-skeleton and by Mg-deficiency caused by changes of the activity of the key enzymes PEPC and F26BP. Different N-regimes indicated a shift from starch formation or sucrose export towards amino acid formation with increasing N-supply. Both the spatial distribution of nitrogen and the photosynthesis capacity of the short influence the reaction of coniferous tress to high N-supply. While located N-addition enhanced root growth, the belowground allocation of photoassimilates and the activity of ectomycorrhizal fungii, homogeneously distributed high N-supply decreased the root/shoot ratio, supressed the carbon flow towards roots and decreased the amount of fungal markers (decreased mycorrhization) in the root system. This could adversely affect nutrient aquisition of the host plant upon N-supply. (orig.)Available from FIZ Karlsruhe / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLELand Baden-Wuerttemberg, Stuttgart (Germany)DEGerman