bluuebunny/crossref_metadata_2025_split huggingface dataset:
The role of cytoplasmic streaming in symplastic transport
Authors: PICKARD W. F. 
Published: March 2003

ABSTRACTThe distributing of materials throughout a symplastic domain must involve at least two classes of transport steps: plasmodesmatal and cytoplasmic. To underpin the latter, the most obvious candidate mechanisms are cytoplasmic streaming and diffusion. The thesis will be here advanced that, although both candidates clearly do transport cytoplasmic entities, the cytoplasmic streaming per se is not of primary importance in symplastic transport but that its underlying molecular motor activity (of which the streaming is a readily visible consequence) is. Following brief tutorials on low Reynolds number flow, diffusion, and targeted intracytoplasmic transport, the hypothesis is broached that macromolecular and vesicular transport along actin trackways is both the cause of visible streaming and the essential metabolically driven cytoplasmic step in symplastic transport. The concluding discussion highlights four underdeveloped aspects of the active cytoplasmic step: (i) visualization of the real‐time transport of messages and metabolites; (ii) enumeration of the entities trafficked; (iii) elucidation of the routing of the messages and metabolites within the cytoplasm; and (iv) transference of the trafficked entities from cytoplasm into plasmodesmata.
Dark chilling imposes metabolic restrictions on photosynthesis in soybean
Authors: VAN HEERDEN P. D. R. , KRÜGER G. H. J. , LOVELAND J. E. , PARRY M. A. J. , FOYER C. H. 
Published: March 2003

ABSTRACTDark chilling inhibited photosynthesis in two soybean [Glycine max (L.) Merr.] cultivars (Fiskeby V and Maple Arrow). The inhibition of CO2 assimilation was characterized by a simultaneous decrease in stomatal conductance (Gs) and intercellular CO2 concentration (Ci) in Maple Arrow, whereas a similar decrease in Gs in Fiskeby V occurred without any change in Ci. Dark chilling had little effect on total ribulose‐1, 5‐bisphosphate carboxylase/oxygenase (Rubisco) activity, Rubisco protein content or Rubisco activation state in the subsequent light period. Chilling reduced the abundance of the nocturnal Rubisco inhibitor, 2‐carboxyarabinitol 1‐phosphate, only in Fiskeby V. The abundance of Rubisco small subunit transcripts was enhanced in both cultivars as a result of dark chilling. Dark chilling decreased the maximal extractable activities and activation states of stromal fructose‐1,6‐bisphosphatase (FBPase) and NADP‐malate dehydrogenase but had no effect on sucrose phosphate synthase or leaf sucrose and starch contents. It is concluded that dark chilling‐induced limitations on CO2 assimilation are predominantly due to metabolic restrictions rather than to direct effects on electron transport reactions and that stromal FBPase is particularly susceptible to dark chilling.
The ecological significance of long‐distance water transport: short‐term regulation, long‐term acclimation and the hydraulic costs of stature across plant life forms
Authors: MENCUCCINI M. 
Published: March 2003

ABSTRACTPlant hydraulic conductance, namely the rate of water flow inside plants per unit time and unit pressure difference, varies largely from plant to plant and under different environmental conditions. Herein the main factors affecting: (a) the scaling between whole‐plant hydraulic conductance and leaf area; (b) the relationship between gas exchange at the leaf level and leaf‐specific xylem hydraulic conductance; (c) the short‐term physiological regulation of plant hydraulic conductance under conditions of ample soil water, and (d) the long‐term structural acclimation of xylem hydraulic conductance to changes in environmental conditions are reviewed. It is shown that plant hydraulic conductance is a highly plastic character that varies as a result of multiple processes acting at several time scales. Across species ranging from coniferous and broad‐leaved trees to shrubs, crop and herbaceous species, and desert subshrubs, hydraulic conductance scaled linearly with leaf area, as expected from first principles. Despite considerable convergence in the scaling of hydraulic properties, significant differences were apparent across life forms that underlie their different abilities to conduct gas exchange at the leaf level. A simple model of carbon allocation between leaves and support tissues explained the observed patterns and correctly predicted the inverse relationships with plant height. Therefore, stature appears as a fundamental factor affecting gas exchange across plant life forms. Both short‐term physiological regulation and long‐term structural acclimation can change the levels of hydraulic conductance significantly. Based on a meta‐analysis of the existing literature, any change in environmental parameters that increases the availability of resources (either above‐ or below‐ground) results in the long‐term acclimation of a less efficient (per unit leaf area) hydraulic system.
Induction of resistance in cocoa against Crinipellis perniciosa and Verticillium dahliae by acibenzolar‐ S‐methyl (ASM)
Authors: Resende M. L. V. , Nojosa G. B. A. , Cavalcanti L. S. , Aguilar M. A. G. , Silva L. H. C. P. , Perez J. O. , Andrade G. C. G. , Carvalho G. A. , Castro R. M. 
Published: March 2003

The benzothiadiazole compound acibenzolar‐S‐methyl (ASM) was assessed as an inducer of resistance against Crinipellis perniciosa, agent of witches’ broom, and Verticillium dahliae, agent of vascular wilt, both on cocoa. ASM induced a reduction in incidence of witches’ broom of up to 84·5% when sprayed 30 days before inoculation on cocoa seedlings of cv. Catongo. ASM also induced a reduction in severity of Verticillium wilt to 55·4% on cv. Theobahia. For both pathosystems, effects of dose on disease were not clearly observed. The efficacy of the inducer increased with the interval between sprayings and the respective inoculations with the pathogens. In another experiment, the effect of ASM on the control of witches’ broom on cocoa seedlings was compared with that of cuprous oxide and tebuconazole, all sprayed 15 days before inoculation. ASM reduced disease incidence by 60·1% compared with the inoculated control. ASM was superior to tebuconazole, and there was also a tendency for ASM to be better than cuprous oxide. To understand the mechanism of action of ASM as an inducer of resistance, alterations in the levels of total phenolics, polyphenol oxidases and peroxidases were evaluated 3, 15 and 30 days after spraying of seedlings of cv. Catongo. Enzyme activities from seedlings of cv. Theobahia were evaluated 30 days after spraying. On cv. Catongo, no significant differences in total phenolic content and polyphenol oxidase activity were detected after spraying. However, an increase in peroxidase activity was detected at all times of evaluation. On cv. Theobahia, significant increases in activities of peroxidase and polyphenol oxidase were detected, indicating that defence responses due to ASM were dependent on host genotype.
Effects of benzothiadiazole and acetylsalicylic acid on β‐1,3‐glucanase activity and disease resistance in potato
Authors: Bokshi A. I. , Morris S. C. , Deverall B. J. 
Published: March 2003

Benzothiadiazole (BTH), as Bion WG50, and acetylsalicylic acid (ASA) treatments of potato foliage of field‐ and glasshouse‐grown potato plants were compared for control of two foliar diseases, early blight (Alternaria solani) and powdery mildew (Erysiphe cichoracearum). The effect of these treatments on harvested tubers wound‐inoculated with the dry rot fungus (Fusarium semitectum) was also evaluated. BTH (50 mg a.i. L−1) gave almost complete control of both foliar pathogens on inoculated glasshouse‐grown plants and reduced the severity of leaf spotting diseases (mainly early blight) in the field. BTH (100 mg a.i. L−1) and ASA (400 mg a.i. L−1) reduced the severity of dry rot in field‐grown tubers in some post‐harvest wound‐inoculated treatments but not others and a similar reduction occurred with tubers inoculated post‐harvest from BTH‐treated plants grown under glasshouse conditions. BTH treatment increased β‐1,3‐glucanase activity in leaves > stem > tubers > stolons but not in roots. Increased enzyme activity was recorded for up to 45 days post‐treatment.
Decreasing Ratios of Phosphocreatine to β‐ATP Correlates to Progressive Acute Rejection in a Concordant Mouse Heart to Rat Xenotransplantation Model
Authors: Lukes D. J. , Madhu B. , Kjellström C. , Gustavsson M. L. , Mjörnstedt L. , Olausson M. , Soussi B. 
Published: March 2003

Biopsies are difficult to perform in rodent heart transplant models without compromising the graft function and therefore other means to evaluate the grafts repeatedly and noninvasively are warranted. The goal of the present study was to measure changes in ratios of high energy phosphorus containing metabolites detected within vivo31Phosphorous Magnetic Resonance Spectroscopy (31P MRS) in a xenotransplantation model and to investigate if these ratios correlated to histological signs of acute xenograft rejection. Thirty‐five heart transplantations were performed (NMRI‐mice to Lewis (RT11) rats). Thirteen heart transplants underwent repeated dailyin vivo31P MRS measurements and 22 grafts were measured on any of 4 postoperative days and thereafter sacrificed for histology. A modified scoring system based on Billingham's criteria was used to stage the rejection process. The median graft survival was 3.0 ± 0.44 (median ± SD) days (n = 17). Significant differences, both overall and interday, could be calculated for the phosphocreatine (PCr)/β‐adenosine triphosphate (β‐ATP) ratios and for the rejection score. The decreases in PCr/β‐ATP ratios correlated significantly to the progressive acute rejection process in the sacrificed grafts (P = 0.01). Further studies are indicated to establish the potential of31P MRS in immunosuppressed recipients of vascularized xenotransplants with prolonged graft survival.
T‐Cell Enforced Invariance of the Antibody Repertoire in the Immune Response Against a Bacterial Carbohydrate Antigen
Authors: Rademaekers A. , Specht C. , Kölsch E. 
Published: March 2003

The humoral response against the bacterial polysaccharide antigen α(1→3) dextran (Dex) is controlled by J558 idiotype‐(Id) specific T cells. These T cells of which the cell clone 178–4 Ts is a representative by all relevant criteria, recognize J558 Id‐bearing B cells in an I‐Ed‐restricted manner. Costimulation via CD28/B7‐1 but not via CD40/CD40L leads to T‐cell activation. These T cells do not only suppress B cells producing the immunoglobulin (Ig)G3 isotype but also support the survival and clonal expansion of J558 Id positive B cells both in vivo and in vitro. This T‐cell mediated dominance of the J558 idiotype limits the appearance of antibodies carrying other more diverse idiotypes which appear in immunized BALB/c nu/nu mice where no regulatory T cells occur. This T‐cell mediated antibody invariance could be a strategy of the immune system responding to highly conserved antigens like polysaccharides, different from those against protein antigens, where diversity is assumed to be the basis for a successful response.
Repeated cycles of submarine channel incision, infill and transition to sheet sandstone development in the Alpine Foreland Basin, SE France
Authors: McCaffrey William D. , Gupta Sanjeev , Brunt Rufus 
Published: March 2003

ABSTRACTThe Grès de Champsaur turbidite system, deposited in a distal setting in the Alpine Foreland Basin of south‐eastern France, exhibits a repeated upsection alternation in sand body geometry between incised channels and sheet sands. The channels form symmetric lenticular erosional features, of width 900–1000 m (measured between the lateral limits of incision) and depth 65–115 m, and can be traced axially for up to 5 km. In each case, the channel fill is capped by a laterally persistent sandy sheet‐form interval, which lies upon a fine‐grained substrate beyond the channel margins. No intrachannel elements have been traced into the substrate sequence, suggesting that, before infill, the channels acted as open sea‐floor conduits of essentially the same dimensions as the preserved channel deposits. The channels are vertically stacked, although axial erosion juxtaposes younger channel axis deposits against the fill of older channels and their channel‐capping sheet sandstones to produce an apparently well‐connected composite sandstone body geometry. The predominant channel‐fill facies comprises coarse‐grained, amalgamated sandstones, which are commonly parallel‐ or cross‐stratified. Subsidiary facies of finer grained sandstone–mudstone couplets and clast‐bearing muddy debrites are commonly preserved as erosional remnants, suggesting a complex channel history of aggradation and erosion. The repeated cycles of channel incision, infill and transition to sheet sandstone development indicate repetitive incision and healing of the palaeo‐sea floor. A model is proposed that links incision to the development of relatively steep axial gradients (parallel to the mean dispersal direction) and the return to sheet‐form deposition to the re‐establishment of lower axial gradients, with the repetitive switch between incisional channels and sheet sandstones driven by changes in sediment input rate against a background of ongoing sea‐floor tilting.
Facies analysis of the Trypali carbonate unit (Upper Triassic) in central‐western Crete (Greece): an evaporite formation transformed into solution‐collapse breccias
Authors: Pomoni‐Papaioannou F. , Karakitsios V. 
Published: March 2003

AbstractThe Trypali carbonate unit (Upper Triassic), which crops out mainly in central‐western Crete, occurs between the parautochthonous series (Plattenkalk or Talea Ori‐Ida series, e.g. metamorphic Ionian series) and the Tripolis nappe (comprising the Tripolis carbonate series and including a basal Phyllite–Quartzite unit). It consists of interbedded dolomitic layers, represented principally by algally laminated peloidal mudstones, foraminiferal, peloidal and ooidal grainstones, as well as by fine‐grained detrital carbonate layers, in which coarse baroque dolomite crystals and dolomite nodules are dispersed. Baroque dolomite is present as pseudomorphs after evaporite crystals (nodules and rosettes), which grew penecontemporaneously by displacement and/or replacement of the host sediments (sabkha diagenesis). However, portions of the evaporites show evidence of resedimentation. Pre‐existing evaporites predominantly consisted of skeletal halite crystals that formed from fragmentation of pyramidal‐shaped hoppers, as well as of anhydrite nodules and rosettes (salt crusts). All microfacies are characteristic of peritidal depositional environments, such as sabkhas, tidal flats, shallow hypersaline lagoons, tidal bars and/or tidal channels. Along most horizons, the Trypali unit is strongly brecciated. These breccias are of solution‐collapse origin, forming after the removal of evaporite beds. Evaporite‐related diagenetic fabrics show that there was extensive dissolution and replacement of pre‐existing evaporites, which resulted in solution‐collapse of the carbonate beds. Evaporite replacement fabrics, including calcitized and silicified evaporite crystals, are present in cements in the carbonate breccias. Brecciation was a multistage process; it started in the Triassic, but was most active in the Tertiary, in association with uplift and ground‐water flow (telogenetic alteration). During late diagenesis, in zones of intense evaporite leaching and brecciation, solution‐collapse breccias were transformed to rauhwackes. The Trypali carbonate breccias (Trypali unit) are lithologically and texturally similar to the Triassic solution‐collapse breccias of the Ionian zone (continental Greece). The evaporites probably represent a major diapiric injection along the base of the parautochthonous series (metamorphic Ionian series) and also along the overthrust surface separating the parautochthonous series from the Tripolis nappe (Phyllite–Quartzite and Tripolis series). The injected evaporites were subsequently transformed into solution‐collapse breccias.
Insights into the collection and emplacement of granitic magma based on 3D seismic images of normal fault‐related salt structures
Authors: Quirk  , D’Lemos  , Mulligan  , Rabti  
Published: March 2003

ABSTRACT3D seismic data from salt structures in the Southern North Sea show how viscous fluids tend to migrate towards and flow upwards along the footwalls of active normal faults where zones of low stress are inherent. This process provides one potential solution for the question of how enough space is created to accommodate large granitic bodies in the crust. During episodes of regional extension, granitic melt may collect in the lower crust below normal detachments in domed areas from which magma may be sourced. Subsequently, in the upper crust, emplacement can occur in fault‐bounded laccoliths at rates commensurate with other geological processes.
Promoter tagging with a promoterless ipt gene leads to cytokinin‐induced phenotypic variability in transgenic tobacco plants: implications of gene dosage effects
Authors: Hewelt Andreas , Prinsen Els , Schell Jeff , Van Onckelen Harry , Schmülling Thomas 
Published: March 2003

SummaryTobacco plants have been transformed with a T‐DNA construct harboring a promoterless cytokinin‐synthesizing ipt gene close to the right T‐DNA border. Eighteen out of 85 transgenic clones displayed phenotypic alterations typical for an enhanced cytokinin production. Northern blot analysis confirmed the transcriptional activation of the introduced gene by tagged plant promoters. The concentration of cytokinins, expressed as zeatinriboside equivalents, was increased up to sevenfold in transgenic tissues. These increases in cytokinin levels resulted in major developmental changes. Transgenic clones exhibited to different levels traits of a general cytokinin‐syndrome, i.e. reduced root growth, reduced apical dominance, reduced leaf surface, reduced growth of the stem and retarded leaf senescence or displayed localized and developmentally specific cytokinin‐induced alterations in otherwise normally developing plants. These traits were in particular a simultaneous break of dormancy in all axillary buds before or at the onset of flowering or the reorientation of the developmental pathway of secondary meristems or terminally differentiated cells. This indicates that endogenously produced cytokinins not only influence different growth parameters but have the potential to alter differentiation pattern. The results show that stably inherited developmental alterations due to a general or localized cytokinin overproduction can be obtained by the promoter‐tagging approach. The investigation of gene dosage effects in homozygote plants readresses the question of threshold levels for cytokinin effects on the developmental program of plants.
Arabidopsis late‐flowering fve mutants are affected in both vegetative and reproductive development
Authors: Martínez‐Zapater José M. , Jarillo José A. , Cruz‐Alvarez Marilyn , Roldán Marta , Salinas Julio 
Published: March 2003

SummaryThe development of wild‐type Arabidopsis thaliana (L.) Heyhn and two late‐flowering fve mutants has been analysed under different environmental conditions. In wild‐type plants, short‐day photoperiods delay the floral transition as a consequence of lengthening all the developmental phases of the plant. Moreover, short days also alter the inflorescence structure by reducing the internode elongation and delaying the establishment of the floral developmental programme in the lateral meristems of the inflorescence and co‐florescences. Mutations at the FVE locus cause a delay in flowering time, and a change in the inflorescence structure, similar to the effect of short photoperiods on wild‐type plants. However, the effect of the fve mutations is additive to the effect of short days, and all the aspects of the Fve phenotype are corrected by vernalization. These results seem to indicate that FVE is not simply involved in timing the transition from vegetative to reproductive growth, but that it could play a role during all stages of plant development.
Immunolocalization of freezing‐tolerance‐associated proteins in the cytoplasm and nucleoplasm of wheat crown tissues
Authors: Houde Mario , Daniel Claude , Lachapelle Mario , Allard France , Laliberté Sylvie , Sarhan Fathey 
Published: March 2003

SummaryA protein family associated with the development of freezing tolerance in wheat has been identified. This protein family is Gramineae‐specific and coordinately regulated by low temperature. Antibodies directed against the 50 kDa (WCS120) protein recognize at least 5 members of this family. Using these antibodies, the cellular content and location of this protein family was determined in cold‐acclimated wheat seedlings. Western analyses of subcellular fractions indicated the presence of all members of the family in the cytosolic and purified nuclear fractions. These proteins accumulated to 0.9% of soluble proteins after 21 days of cold acclimation in winter wheat. This represents a cellular concentration of 1.34 µM. Immunohistochemical localization showed that these proteins are highly expressed in the vascular transition zone. No detectable expression was found in mature xylem, in the shoot apical meristem or lateral root primordia. This differential tissue expression suggests that the sensitive cells near the regions where water tends to freeze first require a higher amount of these proteins. This observation is consistent with the fact that regrowth after freezing stress is highly dependent on the viability of this region of the crown. Electron microscopy analysis using immunogold labelling showed that these proteins are present in the cytoplasm and in the nucleoplasm. They are not found in cell walls or other organelles. In vitro cryoprotective assays indicated that the WCS120 protein (PD50 of 10 µg ml−1 or 0.2 µM) are as effective as BSA and sucrose (at 250 mM) against freezing denaturation of lactate dehydrogenase. These results suggest that this protein family may be involved in a general mechanism of protection in the soluble fraction of the cell. Their presence in the nucleoplasm may also suggest a possible protective function of the transcriptional machinery. The high hydrophilicity, the abundance and stability of these proteins to boiling suggest that they may provide a particular micro‐environment needed for cell survival in the sensitive vascular transition zone during freezing stress.
Ethylene regulates the timing of leaf senescence in Arabidopsis
Authors: Grbić Vojislava , Bleecker Anthony B. 
Published: March 2003

SummaryThe plant hormone ethylene influences many aspects of plant growth and development, including some specialized forms of programmed senescence such as fruit ripening and flower petal senescence. To study the relationship between ethylene and leaf senescence, etr1‐1, an ethylene‐insensitive mutant in Arabidopsis, was used. Comparative analysis of rosette leaf senescence between etr1‐1 and wild‐type plants revealed that etr1‐1 leaves live approximately 30% longer than the wild‐type leaves. Delayed leaf senescence in etr1‐1 coincided with delayed induction of senescence‐associated genes (SAGs) and higher expression levels of photosynthesis‐associated genes (PAGs). In wild‐type plants, exogenous ethylene was able to further accelerate induction of SAGs and decrease expression of PAGs. The extended period of leaf longevity in etr1‐1 was associated with low levels of photosynthetic activity. Therefore, the leaves in etr1‐1 functionally senesced even though the apparent life span of the leaf was prolonged.