Effect of the Hierarchical Position of Individuals in a \u3ci\u3eMedicago sativa\u3c/i\u3e Stand on Shoot Respiration

The influence of the hierarchical position on the relationship between C gains and C losses (respiration) of individuals was investigated in a alfalfa (Medicago sativa) stand. The hierarchical position that an individual occupied was defined by its height relative to the stand height. Stands were established by arranging potted individual plants at a density of 400 plants m-2. Stands were grown in growth cabinets. 13C steady-state labelling was used to assess C fixation (Cnew) by individuals during a photoperiod of 16 h. Respiration of shoots was measured during the following 8 h dark period. The amount of Cnew used in shoot respiration (Cnew,R) was calculated from the rate of respiration and the isotopic composition of respiratory CO2. The rate of Cnew,R of each individual was proportional to the product of Cnew and the hierarchical position of the individual. For individuals in high hierarchical positions, Cnew,R was about 10 % of Cnew. This proportion decreased with decreasing hierarchical position. Conversely, the amount of C respired by the consumption of other substrates (Cold,R) was about 0.5 % of the shoot C mass. This was true for all plants, independent of their hierarchical position. It was concluded that plants getting into low hierarchical positions had to invest increasingly more carbohydrates from reserves to sustain maintenance needs

Effects of Nitrogen Supply and Nitrogen Form on Intrinsic Water-Use Efficiency in Temperate, Semi-Natural Grasslands under Rising Atmospheric CO\u3csub\u3e2\u3c/sub\u3e

Carbon uptake and water loss of plants are controlled by the regulation of carbon assimilation rate (A) and stomatal conductance (gs). Any changes in these parameters under rising atmospheric CO2 concentration (ca) influence plant water-use efficiency and can affect carbon and water relations in grassland ecosystems. Time-series analyses of intrinsic water-use efficiency (Wi) of C3 grassland vegetation during the 20th century have shown that carbon uptake relative to water loss generally increased (Köhler et al. 2010, 2012; Barbosa et al. 2010). Short-term experiments suggest that nitrogen (N) supply (Stitt and Krapp 1999) and N form (Bloom et al. 2011) also play a role. We hypothesize that any increase in Wi should be stronger in swards with high N availability and with ammonium (NH4)-N instead of nitrate (NO3)-N fertilization

-46 -Multifunctional Grasslands in a Changing World Volume I Grasslands/Rangelands Resources and Ecology--Ecology of Grasslands/Rangelands

Key Points: The use of stable isotope analysis in grassland science has increased enormously in the last two decades. It is providing insight into the functioning of grassland systems, including aspects such as the biogeochemical cycles of carbon, nitrogen and water, C 3 :C 4 vegetation dynamics, the nutritional ecology of grassland fauna, and the (agro)ecology of cattle production systems. This paper deals with the natural stable isotope compositions of three major bioelements (carbon, nitrogen and oxygen) and how they behave in organisms and ecosystems, and it describes examples of recent research progress in the ecology of grassland systems, which were made with the help of stable isotope analysis. Introduction Until 1990 stable isotope analysis was used only sporadically in grassland research. Today, more than 6% of all 'grassland' publications appearing in the ISI Web of Science data base employ stable isotope analysis. Several reviews and books have been published in the last years, which covered various aspects of the application of natural stable isotope analysis in ecology and in the study of stable isotope behaviour in the environment and in organisms (e.g

Video-assisted Thoracoscopic Resection of a Small Pulmonary Nodule after Computed Tomography-guided Localization with a Hook-wire System: Experience in 45 Consecutive Patients

Background: This study is a single-institution validation of video-assisted thoracoscopic (VATS) resection of a small solitary pulmonary nodule (SPN) previously localized by a CT-guided hook-wire system in a consecutive series of 45 patients. Methods: The records of all patients undergoing VATS resection for SPN preoperatively localized by CT-guided a hook-wire system from January 2002 to December 2004 were assessed with respect to failure to localize the lesion by the hook-wire system, conversion thoracotomy rate, duration of operation, postoperative complications, and histology of SPN. Results: Forty-five patients underwent 49 VATS resections, with simultaneous bilateral SPN resection performed in 4. Preoperative CT-guided hook-wire localization failed in two patients (4%). Conversion thoracotomy was necessary in two patients (4%) because it was not possible to resect the lesion by a VATS approach. The average operative time was 50 min. Postoperative complications occurred in 3 patients (6%), one hemothorax and two pneumonia. The mean hospital stay was 5 days (range: 2-18 days). Histological assessment revealed inflammatory disease in 17 patients (38%), metastasis in 17 (38%), non-small-cell lung cancer (NSCLC) in 4 (9%), lymphoma in 3 (6%), interstitial fibrosis in 2 (4%), histiocytoma in one (2%), and hamartoma in one (2%). Conclusions: Histological analysis of resected SPN revealed unexpected malignant disease in more than 50% of the patients indicating that histological clarification of SPN seems warranted. Video-assisted thoracoscopic resection of SPN previously localized by a CT-guided hook-wire system is related to a low conversion thoracotomy rate, a short operation time, and few postoperative complications, and it is well suited for the clarification of SP

Strategies for Accelerating the Development of Catalytic Enantioselective Reactions

The development of enantioselective catalytic processes for the manufacture of chiral intermediates is a very complex endeavor and can be very time consuming and expensive. In this contribution the major issues which might lead to long development times will be discussed and strategies to deal with these problems are described. The general part is illustrated with the approach Solvias has chosen for assisting and supporting the development of enantioselective homogeneous hydrogenation processes, at the moment the most important industrial application of asymmetric catalysis. Special emphasis is given to the application of high-throughput screening (HTS) using a Symyx HiP system and the description of the Solvias portfolio of chiral ligands which makes a broad variety of diphosphine ligands available for all phases of process development from the first screening experiments to the large-scale manufacturing phase. Four case histories serve to illustrate the generic description of the development process

Loss of fungal symbionts at the arid limit of the distribution range in a native Patagonian grass—Resource eco-physiological relations

Crucial to our understanding of plant ecology is the consideration of the eco-physiological responses and constraints of plant–fungal symbioses throughout the native distribution range of their host. We examined key eco-physiological roles of two co-occurring fungal symbionts [Epichloë endophytes and arbuscular mycorrhizal fungi (AMF)] in the endemic grass Hordeum comosum across a wide bioclimatic gradient and contrasting grazing severity. We sampled H. comosum plants along four humid-to-arid transects in Patagonia, Argentina, covering its entire distribution range and determined Epichloë presence, AMF root colonization, nitrogen and phosphorus concentration, intrinsic water-use efficiency (iWUE, the ratio of photosynthesis to stomatal conductance) and 18O-enrichment of cellulose in shoots. Root colonization by AMF increased with Epichloë presence. All plants hosted Epichloë in the humid range of the gradient, but symbioses occurrence decreased towards arid sites which also displayed severe grazing symptoms at site level. Symbiosis with Epichloë correlated positively with shoot nitrogen concentration in the centre of the distribution range, and with shoot phosphorus concentration across the entire distribution range. The site-level relationship of AMF colonization with 18O-enrichment and iWUE suggested that mycorrhiza boosted stomatal conductance in humid environments but curbed it in arid environments. While the interpretation of interactions and potential causalities from observational studies should be done with caution, this study demonstrates distinct correlations between plant–fungal symbiont associations and key resource parameters (phosphorus, nitrogen and iWUE vs. 18O-enrichment). Such correlations may suggest particular functional roles for these symbionts in the ecology of their host plant. A free Plain Language Summary can be found within the Supporting Information of this article.Fil: Casas, Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Recursos Naturales y Ambiente; Argentina. Universitat Technical Zu Munich; AlemaniaFil: Gundel, Pedro Emilio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina. Universidad de Talca; ChileFil: Deliens, Eluney. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Recursos Naturales y Ambiente; ArgentinaFil: Iannone, Leopoldo Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Micología y Botánica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Micología y Botánica; ArgentinaFil: García Martinez, Guillermo. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Patagonia Sur. Estación Experimental Agropecuaria Esquel; ArgentinaFil: Vignale, Maria Victoria. Universidad Nacional de Misiones; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Micología y Botánica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Micología y Botánica; Argentina. Gobierno de la Provincia de Misiones. Instituto Misionero de Biodiversidad (imibio); ArgentinaFil: Schnyder, Hans. Universitat Technical Zu Munich; Alemani