bluuebunny/crossref_metadata_2025_split huggingface dataset:
Expression of potassium‐transporter coding genes, and kinetics of rubidium uptake, along a longitudinal root axis
Authors: VALLEJO AUGUSTO J. , PERALTA MARIA LUISA , SANTA‐MARIA GUILLERMO E. 
Published: July 2005

ABSTRACTThe pattern of mRNA accumulation of genes coding for the putative potassium transporters HvHAK1A, HvHAK1B, HvHAK2, HvHAK3 and HvAKT1 along seminal roots was studied in K+ starved barley (Hordeum vulgare) plants. Accumulation of these transcripts was lower in young, relative to older root zones, indicating the existence of a coordinated spatial pattern of gene regulation. A study of rubidium (Rb+) uptake kinetics showed that for all root zones transport can be dissected into a linear and a saturable component. Paralleling the pattern of mRNA accumulation the Vmax of the saturable term was lowest in the youngest root zone. No differences in the Rb+ Km or in the linear term were observed among root zones. K+ channel blockers Ba2+, Al3+, and tetraethylammonium exerted no effect on Rb+ uptake from diluted Rb+ solutions, while it was inhibited by Cs+, NH4+, methylamine, and K+ in all root zones. These results show that high‐affinity Rb+ transport over the entire axis is mediated by transporters displaying HAK1‐like properties. The observation of a differential effect of Na+ on Rb+ uptake along roots is compatible with a change in the proportion and/or the activity of those transport entities following a longitudinal gradient.
A mitochondrial half‐size ABC transporter is involved in cadmium tolerance in Chlamydomonas reinhardtii
Authors: HANIKENNE M. , MOTTE P. , WU M. C. S. , WANG T. , LOPPES R. , MATAGNE R. F. 
Published: July 2005

ABSTRACTFive cadmium‐sensitive insertional mutants, all affected at the CDS1 (‘cadmium‐sensitive 1’) locus, have been previously isolated in the unicellular green alga Chlamydomonas reinhardtii. We here describe the cloning of the Cds1 gene (8314 bp with 26 introns) and the corresponding cDNA. The Cds1 gene, strongly induced by cadmium, encodes a putative protein (CrCds1) of 1062 amino acid residues that belongs to the ATM/HMT subfamily of half‐size ABC transporters. This subfamily includes both vacuolar HMT‐type proteins transporting phytochelatin‐cadmium complexes from the cytoplasm to the vacuole and mitochondrial ATM‐type proteins involved in the maturation of cytosolic Fe/S proteins. Unlike the Δsphmt1 cadmium‐sensitive mutant of Schizosaccharomyces pombe that lacks a vacuolar HMT‐type transporter, the cds1 mutant accumulates a high amount of phytochelatin–cadmium complexes. By epitope tagging, the CrCds1 protein was localized in the mitochondria. Even though mitochondria of cds1 do not accumulate important amounts of ‘free’ iron, the mutant cells are hypersensitive to high iron concentrations. Our data show for the first time that a mitochondrial ATM‐like transporter plays a major role in tolerance to cadmium.
Differences in the success of sugar maple and red maple seedlings on acid soils are influenced by nutrient dynamics and light environment
Authors: ST CLAIR SAMUEL B. , LYNCH JONATHAN P. 
Published: July 2005

ABSTRACTVariation in tolerance to nutrient limitations may contribute to the differential success of sugar maple (Acer saccharum Marsh.) and red maple (Acer rubrum L.) on acid soils. The objectives of this study were to examine these relationships as influenced by light environment and test whether sensitivity to nutrient stress is mediated by oxidative stress. First‐year sugar maple and red seedlings were grown on forest soil cores contrasting in nutrient availability under high or low light intensity. Foliar nutrition, photosynthesis, growth and antioxidant enzyme activity were assessed. Photosynthesis and growth of sugar maple were significantly lower on nutrient‐poor soils and were correlated with leaf nutrient status with Ca and P having the strongest influence. For red maple, only chlorophyll content showed sensitivity to the nutrient‐poor soils. High light exacerbated the negative effects of nutrient imbalances on photosynthesis and growth in sugar maple. Antioxidant enzyme activity in sugar maple was highest in seedlings growing on nutrient‐poor soils and was inversely correlated with photosynthesis, Ca, P, and Mg concentrations. These results suggest that: (1) sugar maple is more sensitive to nutrient stresses associated with low pH soils than red maple; (2) high light increases sugar maple sensitivity to nutrient stress; (3) the negative effects of nutrient imbalances on sugar maple may be mediated by oxidative stress.
Temporal photosynthetic carbon isotope signatures revealed in a tree ring through 13CO2 pulse‐labelling
Authors: KAGAWA AKIRA , SUGIMOTO ATSUKO , YAMASHITA KANA , ABE HISASHI 
Published: July 2005

ABSTRACTUsing a combined method of pulse‐labelling trees and analysing detailed distribution of 13C tracer within tree rings, we studied how photo‐assimilates incorporated on a given day are then distributed in a tree ring. A branch of a 4‐year‐old Cryptomeria japonica D.Don tree growing in Tsukuba, Japan was pulse‐labelled with non‐radioactive 13CO2 on two occasions: 29 May 2001 and 18 September 2001. Two discs were cut from the stem on 4 March 2002, one immediately under and the other 0.5 m below the branch and put through high‐resolution δ13C analysis. δ13C peaks were observed in both the earlywood and latewood of the concerned tree ring, corresponding to each pulse‐labelling date. The earlywood peaks was broader than the latewood peaks, possibly reflecting seasonal variation of the width of wood developing zone. Half‐widths of the peaks were measured and used as indicators for the potential time resolution of tree‐ring isotope analysis. The half‐widths of the peaks indicated a time resolution no finer than 8.7–28 and 33–42 d in the early and latewood, respectively. Holocellulose extraction yielded only a slight change to the shape of the δ13C peaks. 13C tracer pulse‐labelled in May and September reached tangentially different locations in the lower disc, suggesting a seasonal change in the pathway of carbohydrates. Local consumption of spring assimilates and long‐distance downward transport of autumn assimilates were also suggested.
Leaf anatomy as a constraint for photosynthetic acclimation: differential responses in leaf anatomy to increasing growth irradiance among three deciduous trees
Authors: OGUCHI R. , HIKOSAKA K. , HIROSE T. 
Published: July 2005

ABSTRACTInterspecific variation in the response to transfer from low to high growth irradiance with respect to anatomical and photosynthetic characteristics was studied in mature leaves of three tree species, Betula ermanii Cham., Acer rufinerve Sieb. et Zucc. and Fagus crenata Blume, which occur in different successional stages in temperate deciduous forests. Transfer from low to high irradiance increased the light‐saturated rate of photosynthesis per unit leaf area (Pmax) significantly in B. ermanii and A. rufinerve, but not in F. crenata. Leaves of B. ermanii grown at low irradiance were relatively thick and had vacant spaces along the mesophyll cell surfaces which was not occupied by chloroplasts or other organelles. After transfer to high irradiance, chloroplasts enlarged to fill the space along with Pmax without an increase in leaf thickness. Leaves of A. rufinerve were plastic in mesophyll cell surface area and in leaf thickness, both of which increased after the transfer to high irradiance, along with an increase in the amount of chloroplasts and in Pmax. On the other hand, F. crenata had little mesophyll cell surface unoccupied by chloroplasts and leaf anatomy was not changed after the transfer. In all species, Pmax was strongly correlated with chloroplast surface area adjacent to the exposed mesophyll surface across different growth irradiances. An increase in Pmax was observed only when chloroplast volume also increased. We conclude that light acclimation potential is primarily determined by the availability of unoccupied cell surface into which chloroplasts expand, as well as by the plasticity of the mesophyll that allows an increase in its surface area.
Contrasting phosphate acquisition of mycorrhizal fungi with that of root hairs using the root hairless barley mutant
Authors: JAKOBSEN IVER , CHEN BAODONG , MUNKVOLD LISA , LUNDSGAARD THORBEN , ZHU YONG‐GUAN 
Published: July 2005

ABSTRACTComparisons between plant species or cultivars differing in root hair length have indicated a major impact of root hairs on the mycorrhizal dependency of plants with respect to phosphate (P) uptake. The current study aimed to investigate this relationship by comparing directly the mycorrhizal dependency of a spontaneous root hairless mutant, brb, in Hordeum vulgare cv Pallas and its wild type. Both brb and wild type were grown at different soil P levels in association with different mycorrhizal fungi. P uptake of brb and wild type was similar at high P levels, but P uptake by non‐mycorrhizal brb plants at low P levels was substantially lower than that of the non‐mycorrhizal wild‐type plants. However, P uptake of the mutant was much increased by mycorrhizas and with one fungus, the additional P uptake was effectively translated into increased plant growth. Roots of the mutant contained typical colonization structures and a radioactive tracer confirmed P transport by the extraradical mycelium. This is the first direct evaluation of the relative effectiveness of root hairs and mycorrhizas. Mycorrhizas effectively substituted root hairs in P uptake, whereas the additional P was most often used less effectively in promoting plant growth than P provided by root hairs.
Behaviour and dynamics of a hydrothermal plume in Lake Banyoles, Catalonia, NE Spain
Authors: SERRA TERESA , SOLER MARIANNA , JULIÀ RAMON , CASAMITJANA XAVIER , COLOMER JORDI 
Published: July 2005

AbstractA hydrothermal plume forms in Lake Banyoles, NE Spain, as a result of convection above a springwater‐fed suspension cloud ponded on the lake floor. The plume propagates upwards reaching a level of neutral buoyancy from where a turbidity current spreads out laterally. Two‐dimensional temperature and particle concentration measurements show the fate of the hydrothermal plume and its associated turbidity current and reveal its seasonal development. Silt particles transported by the plume have been used as tracers to determine the maximum and equilibrium heights of the plume. When the lake is stratified, the vertical transport of sediment is confined to the lake hypolimnion, as the thermocline limits the vertical propagation of the plume. In contrast, when the lake water column is mixed, the plume reaches the surface of the lake. The field measurements have been compared with models for thermal convection from finite isolated sources. Measurements of the flow velocity at the source of the hydrothermal plume (i.e. the rim current velocity) indicate that cold hypolimnetic water is entrained by the plume. Sedimentation rates measured from sediment traps at the zone where the turbidity current develops vary between 10 and 25 g m−2 day−1, and result from continuous silt particle sedimentation from the turbidity current. Sedimentation rates in traps are higher for stations situated close to the source than those further away (<5 g m−2 day−1). Moreover, the results demonstrate that double diffusive sedimentation from the turbidity current was dominant over grain‐by‐grain settling, causing a mixed distribution of sediments in the region where the turbidity current spreads. The deposition of silt particles could explain the occurrence of silt layers interbedded with biocalcarenites in the littoral zones of the lake and the stratigraphy identified by seismic profiles and cores taken from the lake floor.
Sand grain threshold, in relation to bed ‘stress history’: an experimental study
Authors: PAPHITIS D. , COLLINS M. B. 
Published: July 2005

AbstractBesides particle size, density and shape, the erodibility of a sediment bed depends also upon the exposure to prethreshold velocities in the overlying flow. Such flow effectively rearranges the grains (at and below the bed surface), causing them to become more resistant to subsequent erosion. The effects of the ‘stress history’, leading up to the critical condition for sediment movement, are investigated for unidirectional flows generated in a recirculating laboratory flume. The sediment beds investigated consisted of cohesionless quartz sand grains, with mean grain diameters of 0·194 mm (fine sand), 0·387 mm (medium sand) and 0·774 mm (coarse sand), with narrow particle‐size distributions. The critical (threshold) shear velocity (target value) for the three beds was established, within 2·5 min of increasing the flow from zero velocity. The subsequent experiments were performed under prethreshold velocities at 70% (for 5, 10, 20, 40 and 80 min exposure duration), 80% (for 5, 10, 20, 40 and 80 min exposure duration), 90 and 95% (for 5, 10, 20, 40, 80 and 120 min exposure duration) of the target value. Following exposure to these different prethreshold conditions, the flow was increased then to reach actual critical conditions, within a period of 2·5 min. The critical condition for the initiation of sediment movement was established using visual observation (supplemented by video recordings), according to the Yalin criterion. The results show that if the exposure duration to prethreshold velocities remains constant, then the critical shear velocity increases with increasing prethreshold velocity. Likewise, if the prethreshold velocity remains constant, then the critical shear velocity increases with increasing exposure duration. In some circumstances, the critical shear velocity was found to increase by as much as 27%. An empirical formula is proposed to account for the exposure correction to be applied to the critical shear velocities of sand‐sized sediment beds; this is prior to their inclusion into bedload transport formulae, for an improved prediction of the magnitude and nature of transport.
Bedload path length and point bar development in gravel‐bed river models
Authors: PYRCE RICHARD S. , ASHMORE PETER E. 
Published: July 2005

AbstractLow‐sinuosity meandering gravel‐bed flume experiments were employed to investigate spatial patterns of deposition, which point to patterns of channel development related to the pool and bar morphology. At channel‐forming discharges, fluorescent bedload tracers indicate that deposition is typically focused around the point bar apex, downstream of the apex (contributing to downstream bar migration), and at the bar head/riffle surface. Seven flume experimental runs illustrate a sequence of point bar development related to the spatial patterns of tracer deposition, and the related path length distribution. At early stages of bar formation, transport is from the scour zone across the point bar head to the bar apex and bar margin downstream of the apex. As the point bar develops, bedload transport across the bar decreases, as transport along the channel thalweg increases and sediment is deposited along the bar margin. Deposition cells appear to move from downstream to upstream of the bar apex as this sequence of bar formation progresses. At low (non‐channel‐forming) discharges, transport occurs to the bar head/riffle surface with very little material being transported to the apex region or point bar interior. The implication is that there is an inherent connection between the loci of particle deposition and point bar formation, largely controlled by the morphology of the channel.
Pre‐vegetation alluvial fan facies and processes: an example from the Cambro‐Ordovician Rozel Conglomerate Formation, Jersey, Channel Islands
Authors: WENT DAVID J. 
Published: July 2005

AbstractPrior to the Silurian a lack of land vegetation is expected to have influenced the processes of sedimentation on alluvial fans, principally by causing increased rates of run‐off and erosion in the fan catchments. In the Cambro‐Ordovician Rozel Conglomerate Formation, this effect was central to the generation of alluvial fan deposits that are unusually deficient in sand and clay, despite being sourced from a catchment dominated by sandstone and mudstone. Seven facies are identified, interpreted as representing the deposits of: (i) shallow stream and sheetfloods, (ii) channelized, non‐cohesive debrisflows, (iii) sub‐aerial mud‐rich debrisflows, (iv) sub‐aqueous mud‐rich debrisflows, (v) low energy streams that reworked abandoned fan sectors, (vi) a sandflat‐playa lake system and (vii) talus slopes. The first two facies are both clast‐supported conglomerate, comprise 98% of the deposit, and represent deposition on active depositional lobes and in the fan head trench. The remaining facies are the products of infrequent sedimentary processes, fan abandonment processes and marginal sub‐environments. The facies assemblage in many ways mimics that of a modern‐day, water‐lain, arid region fan. However, the palaeolatitude of these fans was high and the climate is inferred to have been cool and wet. The near absence of sandstone and mudstone beds with few mudflows is ascribed to rapid hinterland uplift and high rates of erosion resulting in minimal chemical breakdown of source rocks in the catchments. Such high rates of erosion are in turn ascribed to a combination of frequent rainstorms and an absence of vegetation cover.
Modelling ancient tides: the Upper Carboniferous epi‐continental seaway of Northwest Europe
Authors: WELLS MARTIN R. , ALLISON PETER A. , HAMPSON GARY J. , PIGGOTT MATTHEW D. , PAIN CHRISTOPHER C. 
Published: July 2005

AbstractDue to a lack of modern analogues, debate surrounds the importance of tides in ancient epi‐continental seas. However, numerical modelling can provide a quantitative means of investigating palaeo‐tidality without recourse to analogues. Finite element modelling of the European Upper Carboniferous epi‐continental seaway predicts an exceedingly low Lunar tidal range (ca 5 cm in the open water regions of the UK and Southern North Sea). The Imperial College Ocean Model (ICOM) uses finite element methods and an unstructured tetrahedral mesh that is computationally very efficient. The accuracy and sensitivity of ICOM tidal range predictions were tested using bathymetric data from the present‐day Mediterranean Sea. The Mediterranean Sea is micro‐tidal and varies in depth up to 5·4 km with an average depth of 1–2 km. ICOM accurately predicts the tidal range given both a realistic, but smoothed, bathymetry and a straight sided basin with a uniform depth of 1 km. Variation in uniform depth from 100 to 3000 m with and without islands consistently predicts micro‐tidality, demonstrating that the model is robust and the effect of bathymetric uncertainty on model output is relatively small. The extremely low tidal range predicted for the European Upper Carboniferous is thus deemed robust. Putative Upper Carboniferous tidal deposits have been described in the UK and southern North Sea, but are represented by cyclic rhythmites and are limited to palaeo‐estuaries. Calculations based on an embayed coast model show that the tidal range could have been amplified to ca 1 m in estuaries and that this is sufficient to form cyclic rhythmites. Without tidal mixing, the tropical equatorial heat and salinity enhancement would promote stratification in the open water body. The introduction of organic matter probably caused anoxia, biotic mortality and carbon accumulation, as evidenced by numerous black ‘marine‐band’ shales.
Quantification of the dry aeolian deposition of dust on horizontal surfaces: an experimental comparison of theory and measurements
Authors: GOOSSENS DIRK 
Published: July 2005

AbstractEight techniques to quantify the deposition of aeolian dust on horizontal surfaces were tested in a wind tunnel. The tests included three theoretical techniques and five measurement techniques. The theoretical techniques investigated were: the gradient technique, the inferential technique without grain‐shape correction, and the inferential technique corrected for grain shape. The measuring techniques included the following surrogate surfaces: a water surface, a glass surface, a metal surface, a vertical array of metal plates, and an inverted frisbee filled with glass marbles. The efficiency of the techniques was investigated for the sediment as a whole (all grain sizes together) as well as for a large number of grain sizes extending from 1 to 104 μm. The surrogate surfaces showed more or less comparable catch efficiencies, although the water surface nearly always caught the highest quantities of dust and the marble‐filled frisbee and the vertical array of metal plates the lowest quantities of dust. The dust fluxes calculated by theoretical methods were markedly different from those obtained by direct measurements. The fluxes calculated by the inferential technique approximated those of the direct measurements only for grain sizes between 30 and 40 μm. For smaller and coarser grains, deviations from the measured fluxes were high. The gradient method, in its turn, provided extremely low calculated fluxes for grains in all size classes investigated. The latter technique was not considered very reliable for the dust used in the tests.
Sediment suspension dynamics and a new criterion for the maintenance of turbulent suspensions
Authors: LEEDER MIKE R. , GRAY THOMAS E. , ALEXANDER JAN 
Published: July 2005

AbstractThe vertical component of the turbulent flow acceleration term, , is used to determine the net positive vertical force that may support a suspended sediment load. A dimensionless criterion, Λ, is proposed for the maintenance of suspension, defined as the ratio of the maximum vertical turbulent stress to immersed weight of the suspended load above a unit bed area. In order that a suspension be maintained:
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where v ′ is instantaneous vertical turbulent velocity, σ and ρ are solid and fluid densities, respectively and m is the suspended load dry mass. The Λ criterion is dynamic, being a ratio of stresses and is analogous in this respect to Shields dimensionless stress criterion, θ, for the initiation of bedload motion. The new criterion is successful in predicting the maintenance of steady‐state suspended sediment transport in open channel shear flow and deposition from non‐uniform particulate density flows of wall jet type.
Bar and dune development during a freshet: Fraser River Estuary, British Columbia, Canada
Authors: VILLARD P. V. , CHURCH M. 
Published: July 2005

AbstractBi‐weekly multi‐track sonar surveys collected along a 2‐km reach of the estuarine South Arm of the Fraser River, British Columbia, Canada, during seasonal high flows document the initiation, development and interaction of dune and bar morphologies. Bedforms of several scales developed in well‐delineated fields. Bedforms that appear to fit accepted equilibrium depth‐scaling developed in the main channel during rising discharge when there was little local aggradation. During the rising stage, a bar also formed along the tidal shelf of the channel, migrated downstream and expanded into the main channel. Dunes that formed along the bar crest, a region of rapid deposition, lagged flow conditions and were larger than expected based on depth‐scaling relations. The larger dunes developed simultaneously, although bar growth lagged dune development and was initially partially obscured by the more rapidly developing dune field. It appears that rapid deposition enhances dune development along the channel tidal shelf to dimensions larger than would be expected by simple depth‐scaling rules. Smaller dunes that fit equilibrium depth‐scaling relations re‐established themselves throughout the study area during falling discharge when there was again little or no aggradation. Bed‐material transport rates estimated from the migration rates of the large dunes suggest that, at high flows, the dunes transport the majority of the material found within the bar.