High photosynthetic capacity of a winter annual in death valley

Camissonia claviformis, a winter annual of Death Valley, California, that fixes carbon dioxide by the C(3) mechanism, has an in situ photosynthetic rate at midday in spring of nearly 6 nanomoles of carbon dioxide per square centimeter per second-an exceptionally high rate. Camissonia fixes absorbed noon sunlight in the 400- to 700-nanometer region into chemical energy with an efficiency of 8.5 percent, which is 80 percent of that theoretically possible for intact leaves. This performance is primarily due to an unusual capacity to utilize high irradiances. Factors associated with this include a high stomatal conductance to carbon dioxide and high levels of soluble protein and ribulose-1,5-diphosphate carboxylase.     

A C. elegans CLIC-like protein required for intracellular tube formation and maintenance

The Caenorhabditis elegans excretory canal is composed of a single elongated and branched cell that is tunneled by an inner lumen of apical character. Loss of the exc-4 gene causes a cystic enlargement of this intracellular tube. exc-4 encodes a member of the chloride intracellular channel (CLIC) family of proteins. EXC-4 protein localizes to various tubular membranes in distinct cell types, including the lumenal membrane of the excretory tubes. A conserved 55-amino acid domain enables EXC-4 translocation from the cytosol to the lumenal membrane. The tubular architecture of this membrane requires EXC-4 for both its formation and maintenance.     

Venus's southern polar vortex reveals precessing circulation

Initial images of Venus's south pole by the Venus Express mission have shown the presence of a bright, highly variable vortex, similar to that at the planet's north pole. Using high-resolution infrared measurements of polar winds from the Venus Express Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) instrument, we show the vortex to have a constantly varying internal structure, with a center of rotation displaced from the geographic south pole by ~3 degrees of latitude and that drifts around the pole with a period of 5 to 10 Earth days. This is indicative of a nonsymmetric and varying precession of the polar atmospheric circulation with respect to the planetary axis.     

Clay plains and geomorphic history of the central Sudan A review

The paper presents an analysis of the Sudan clay plain. Total plain area is 500,000 sq. km., but the paper focuses on an area of 90,000 sq. km.In the east-central Sudan an old erosion surface between600m× 730m above sea level is probably Miocene in age. The main plainlands lie 200 – 300 m below this and date from entertiary times. Evidence of an “African” surface may occur on skeletal volcanoes near Gedaref.Downwarping along NNW-SSE lines formed distinctive basins including the Blue Nile basin. Sediments accumulated in the basins and a sequence of arkose, paludal sandy clay, alluvial sand, silt and clay in the Blue Nile basin is capped by modern silt and clay which has weathered to form a clay soil.The clays on the plain vary in age from upper Pliocene to modern though the weathering seems in balance with a somewhat wetter climate than at present. The clays dominantly on almost level plains are alluvial or lacustrine. The remainder is residual or colluvial weathered material on flat but extremely gently sloping interfluves on higher ground.The clay of the aggradational plains in the Blue Nile basin has been reworked continuously by the rivers and is therefore, much younger than the clay on the degradational plains which is upper Pliocene to Middle Phistocene in age. The present Blue Nile flows in a wide alluvial valley with the channel incised up to 24 m below the general plain.     

Soil catenas to estimate ages of movements on normal fault scarps, with an example from the Wasatch fault zone, Utah, USA

Trenches excavated across fault scarps on a 13 ka delta surface at Brigham City, Utah, USA, document four types of soil-catena phenomena. First, the relict summit soil is eroded at the scarp crest, and its components incorporated into the accumulating colluvial wedge at the scarp base. Second, the pre-faulting soil weakens laterally as it is traced scarpward beneath the colluvial wedge from a relict position beyond the scarp toe. Third, soils developed on individual colluvial wedges and on the underlying, pre-faulting surface merge downslope to form a cumulative soil profile at the scarp toeslope. Fourth, soil horizons thicken downslope, probably due to the combined affect of more available moisture, water infiltration, and sediment accumulation.Two soil catenas were used to evaluate the applicability of a continuity approach to paleoearthquake dating, by which percentages of total development time represented by each soil at a fault scarp footslope could be estimated. The continuity approach sets total soil development at the scarp footslope, including any buried pre-faulting soil plus the sum development of all colluvial wedge soils corrected by a slope factor (F), equal to total soil development at the scarp summit. Soil development was characterized by Profile Development Index (PDI) and pedogenic clay parameters, using facies models to estimate parent material values for genetically-different colluvial units, and recognizing inherited soil components in colluvial wedges as parent material properties. The F slope factor, used to correct colluvial wedge soils for development attributable to slope position rather than age, was checked by using a nearby fluvial scarp as an independent control. Our soil data, when compared to independent age estimates, imply that rates of soil development have not been constant over the last 13 ka at Brigham City, but rather were considerably higher than average between 13 ka and 8.3 ka. Higher rates are probably due to a relatively high influx of eolian dust during the late Pleistocene to early Holocene following the lowering of Lake Bonneville, a large paleolake in the western USA. These variable rates of soil development preclude using the continuity approach for paleoearthquake dating at Brigham City. However, promising results showing that generally consistent F factors can be calculated for fault and fluvial scarps leave open the possibility that in areas where soil development rates have been relatively constant over the time period in question, the continuity approach may be a broadly applicable method for paleoearthquake dating.     

小麦根高亲和NO_3~-转运体全长基因(TaNRT2.1)的克隆和鉴定

 在前期获得的 pTaAF 的工作基础上,采用 RACE 方法进一步克隆和鉴定了小麦根 NO3 转运体全长基因-(TaNRT2.1)。将TaNRT2.1和已知的硝态氮转运体基因家族进行同源性比较,指出TaNRT2.1属于HATS中的NRT2家族。Southern　印迹揭示小麦基因组中有1个TaNRT2.1拷贝。Northern　分析示出硝态氮可瞬时诱导TaNRT2.1　mRNA积累,NO 处理 1 h　TaNRT2.1　mRNA很快增加,4　h 达到最大,24　h恢复至诱导前水平,具根专一表达特点。 - 3