Variation of saponin contents in Quillaja saponica Molina

Systematic HPLC analysis of aqueous extracts from bark and woody parts of Quillaja saponaria Mol. ('quillay') growing at three different localities in Central Chile, showed that saponin contents in 100 g of dried plant material ranged from 2.3 g to 15.8 g depending on the extraction method (soxhlet or maceration), the part of the plant analysed and the site of collection. Twigs and barks afforded in most cases extracts with higher levels of saponins as compared to those obtained with woody parts of the same specimen.     

Impacts of rising atmospheric carbon dioxide on model terrestrial ecosystems

In model terrestrial ecosystems maintained for three plant generations at elevated concentrations of atmospheric carbon dioxide, increases in photosynthetically fixed carbon were allocated below ground, raising concentrations of dissolved organic carbon in soil. These effects were then transmitted up the decomposer food chain. Soil microbial biomass was unaffected, but the composition of soil fungal species changed, with increases in rates of cellulose decomposition. There were also changes in the abundance and species composition of Collembola, fungal-feeding arthropods. These results have implications for long-term feedback processes in soil ecosystems that are subject to rising global atmospheric carbon dioxide concentrations.     

Microscale nutrient patches in planktonic habitats shown by chemotactic bacteria

Are nutrients available to microbial communities in micropatches long enough to influence growth and competition? And what are the sources of such patches? To answer these questions, the swimming behavior of chemotactic bacteria in seawater samples was examined. Clusters of bacteria formed in conjunction with cell lysis and excretion by protozoa. These point sources of nutrients spread into spherical patches a few millimeters in diameter and sustained swarms of bacteria for about 10 minutes. Within that time, a large proportion of the nutrients was encountered by bacteria, chemotactic and nonchemotactic alike. Chemotaxis is advantageous for bacteria using patches over a certain size.     

Friction anisotropy and asymmetry of a compliant monolayer induced by a small molecular tilt

Lateral force microscopy in the wearless regime was used to study the friction behavior of a lipid monolayer on mica. In the monolayer, condensed domains with long-range orientational order of the lipid molecules were present. The domains revealed unexpectedly strong friction anisotropies and non-negligible friction asymmetries. The angular dependency of these effects correlated well with the tilt direction of the alkyl chains of the monolayer, as determined by electron diffraction and Brewster angle microscopy. The molecular tilt causing these frictional effects was less than 15 degrees, demonstrating that even small molecular tilts can make a major contribution to friction.     

Biologically based coefficients for partitioning lamb and wool production costs.

Global competition for selling lamb and wool requires sheep producers to effectively prioritize wool and lamb production. Both products are produced simultaneously, and this makes it difficult to differentially assess costs and net returns. This study addressed this issue by developing coefficients for use in financial analysis of lamb and wool profitability across and within five regions of the United States (Eastern, Midwestern, Intermountain West, Great Basin, and Texas). A procedure was developed using a sheep simulation model to partition the amount of nutrients used for lamb and wool production and then using the partitioning information to determine the proportion of costs to be assessed to lamb and wool production. Blackface breed types, when managed without nutritional limitations, had lamb and wool coefficients of .90 and .10, respectively. Wool breeds with unlimited and limited nutrition had lamb coefficients between .80 and .20 and .60 and .40, respectively. In-depth analysis of the Great Basin system indicated that wool and its improvement may contribute as much, if not more, under certain pricing conditions, as increased prolificacy to enterprise profitability. With low lamb prices ($1.32/kg) and moderate wool prices, the partial net returns for a Merino x Rambouillet were higher than the tested prolific breed type ($13.85 vs $11.27/ewe, respectively). This ranking was reversed under high ($2.31/kg) lamb prices ($47.90 vs $55.22, respectively). The derived method provides a basis for analyzing, comparing, and making management and breeding objective decisions.     

Genetic selection and conservation of genetic diversity*

For 100s of years, livestock producers have employed various types of selection to alter livestock populations. Current selection strategies are little different, except our technologies for selection have become more powerful. Genetic resources at the breed level have been in and out of favour over time. These resources are the raw materials used to manipulate populations, and therefore, they are critical to the past and future success of the livestock sector. With increasing ability to rapidly change genetic composition of livestock populations, the conservation of these genetic resources becomes more critical. Globally, awareness of the need to steward genetic resources has increased. A growing number of countries have embarked on large scale conservation efforts by using in situ, ex situ (gene banking), or both approaches. Gene banking efforts have substantially increased and data suggest that gene banks are successfully capturing genetic diversity for research or industry use. It is also noteworthy that both industry and the research community are utilizing gene bank holdings. As pressures grow to meet consumer demands and potential changes in production systems, the linkage between selection goals and genetic conservation will increase as a mechanism to facilitate continued livestock sector development.     

Coupled nitrification-denitrification associated with liquid manure in a gel-stabilized model system

Summary Following the application of liquid manure to soil, the development of the two processes, nitrification and denitrification, was studied in a two-phase model system. A saturated mixture of manure and soil, stabilized with silica gel, was overlain by an aerobic soil phase. Profiles of the redox potential pH, inorganic N, dissolved organic C, nitrification and denitrification potentials, and phospholipid concentrations for an estimate of microbial biomass were measured during a 20-day period. NH ₄ ⁺ diffusing into the aerobic soil was oxidized within 10 mm of the interface, but with only a small accumulation of NO ₂ ^- and NO ₃ ^- . It was estimated that N equivalent to approximately 70% of the NH ₄ ⁺ originally present in the manure was lost through coupled nitrification-denitrification. The potentials for nitrification and denitrification increased 40-and 20-fold, respectively, around the interface. Maximum values were recorded after 14 days. Within 0–5 mm of the anaerobic zone, apparent generation times for NH ₄ ⁺ -oxidizing bacteria of 1.1–1.8 days were estimated between day 1 and day 7. The phospholipid concentration profiles suggested that the biomass within 2 mm on either side of the interface was stimulated throughout the 20-day period.