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  • Articles  (496)
  • Articles: DFG German National Licenses  (496)
  • Munksgaard International Publishers  (292)
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  • 1
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    The European physical journal 46 (2006), S. 27-42 
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. The production of forward jets has been measured in deep inelastic ep collisions at HERA. The results are presented in terms of single differential cross sections as a function of the Bjorken scaling variable (xBj) and as triple differential cross sections d3σ/dxBjdQ2 $dp_{t,{\rm jet}}^2$ , where Q2 is the four momentum transfer squared and $p_{t,{\rm jet}}^2$ is the squared transverse momentum of the forward jet. Also cross sections for events with a di-jet system in addition to the forward jet are measured as a function of the rapidity separation between the forward jet and the two additional jets. The measurements are compared with next-to-leading order QCD calculations and with the predictions of various QCD-based models.
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  • 2
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    The European physical journal 46 (2006), S. 93-105 
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: AbstractWe present a study of anomalous electroweak gauge-boson couplings that can be measured in e+e- and γγ collisions at a future linear collider like ILC. We consider the gauge-boson sector of a locally SU(2)×U(1) invariant effective Lagrangian with ten dimension-six operators added to the Lagrangian of the standard model. These operators induce anomalous three-gauge-boson and four-gauge-boson couplings and an anomalous γγH coupling. We calculate the reachable sensitivity for the measurement of the anomalous couplings in γγ→WW. We compare these results with the reachable precision in the reaction e+e-→WW on the one hand and with the bounds that one can obtain from high-precision observables in Z decays on the other hand. We show that one needs both the e+e- and the γγ modes at an ILC to constrain the largest possible number of anomalous couplings and that the Giga-Z mode offers the best sensitivity for certain anomalous couplings.
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  • 3
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    The European physical journal 46 (2006), S. 269-275 
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: AbstractIt has been suggested that the Grothendieck–Teichmüller group GT should act on the Duflo isomorphism of su(2), but the corresponding realization of GT turned out to be trivial. We show that a solvable quotient of the motivic Galois group – which is supposed to agree with GT – is closely related to the quantum coadjoint action on $U_q(sl_2)$ for q a root of unity, i.e. in the quantum group case one has a nontrivial realization of a quotient of the motivic Galois group. From a discussion of the algebraic properties of this realization we conclude that in more general cases than $U_q(sl_2)$ it should be related to a quantum version of the motivic Galois group. Finally, we discuss the relation of our construction to quantum field and string theory and explain what we believe to be the ‘physical reason’ behind this relation between the motivic Galois group and the quantum coadjoint action. This might be a starting point for the generalization of our construction to more involved examples.
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  • 4
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    The European physical journal 46 (2006), S. 61-67 
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: AbstractWe present a new result on the K+→π+π0γ decay measurement using stopped kaons. The best fit to the decay spectrum comprised of 10 k events gives a branching ratio for the direct photon emission of [3.8±0.8 (stat)±0.7 (syst)]×10-6 in the π+ kinetic energy region of 55 to 90 MeV. This result has been obtained with the assumption that there is no component due to interference with the inner bremsstrahlung.
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  • 5
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    The European physical journal 46 (2006), S. 219-224 
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: AbstractIn this work the double vector meson production in ultraperipheral heavy ion collisions is investigated within the BFKL approach. The integrated cross sections and event rates for the processes $AA\rightarrow V_1 V_2 AA$ ( $V_i=\rho, \omega, \phi, J/\Psi, \Upsilon$ ) are computed and theoretical estimates for scattering on both light and heavy nuclei are given for energies of RHIC and LHC.
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  • 6
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    The European physical journal 46 (2006), S. 107-111 
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: AbstractUltra low momentum neutron catalyzed nuclear reactions in metallic hydride system surfaces are discussed. Weak interaction catalysis initially occurs when neutrons (along with neutrinos) are produced from the protons that capture “heavy” electrons. Surface electron masses are shifted upwards by localized condensed matter electromagnetic fields. Condensed matter quantum electrodynamic processes may also shift the densities of final states, allowing an appreciable production of extremely low momentum neutrons, which are thereby efficiently absorbed by nearby nuclei. No Coulomb barriers exist for the weak interaction neutron production or other resulting catalytic processes.
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  • 7
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: AbstractThis paper studies the possibility of direct extraction of the transversity and its accompanying T-odd parton distribution function (PDF) from Drell–Yan (DY) processes with unpolarized pion beam and with both unpolarized and transversely polarized proton targets. At present, such an extraction can be performed with the COMPASS experiment at CERN. The preliminary estimations performed for the COMPASS kinematic region demonstrate that it is quite realistic to extract both transversity and its accompanying T-odd PDF under COMPASS conditions.
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  • 8
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    The European physical journal 46 (2006), S. 1-26 
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: AbstractThe exclusive and semi-exclusive branching ratios of the τ lepton hadronic decay modes ( $h^- \nu_\tau$ , $h^- \pi〈Superscript〉0〈/Superscript〉 \nu_\tau$ , $h^-\pi^0 \pi^0\nu_\tau$ , $h^- \geq2 \pi^0 \nu_\tau$ , $h^- \geq3 \pi^0 \nu_\tau$ , $2h^- h^+ \nu_\tau$ , $2h^- h^+\pi^0\nu_\tau$ , $2h^- h^+ \geq2 \pi^0 \nu_\tau$ , $3h^- 2h^+\nu_\tau$ and $3h^- 2h^+ \geq1 \pi^0 \nu_\tau$ ) were measured with data from the DELPHI detector at LEP.
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  • 9
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    The European physical journal 46 (2006), S. 123-134 
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. Inclusive cross sections for Higgs boson production in proton-proton collisions are calculated in the formalism of unintegrated gluon distributions (UGDFs). Different UGDFs from the literature are used. Although they were constructed in order to describe the HERA deep-inelastic scattering F2 data, they lead to surprisingly different results for Higgs boson production. We present both the two-dimensional invariant cross section as a function of Higgs boson rapidity and transverse momentum, as well as the corresponding projections on rapidity or transverse momentum. We quantify the differences between different UGDs by applying different cuts on interrelations between the transverse momentum of the Higgs and the transverse momenta of both fusing gluons. We focus on the large rapidity region. The interplay of the gluon-gluon fusion and weak-boson fusion in rapidity and transverse momentum is discussed. We find that above pt ∼ 50–100 GeV the weak-gauge boson fusion dominates over gluon-gluon fusion.PACS. 12.38.Bx,12.38.Cy,13.85.Qk,14.70.Hp,14.80.Bn
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  • 10
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    The European physical journal 46 (2006), S. 191-217 
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. The amplitude of the Dalitz decay π0 → e+e– γ is studied and its model-independent properties are discussed in detail. A calculation of radiative corrections is performed within the framework of two-flavor chiral perturbation theory, enlarged by virtual photons and leptons. The lowest meson dominance approximation, motivated by large NC considerations, is used for the description of the π0 –γ*–γ* transition form factor and for the estimate of the NLO low energy constants involved in the analysis. The two photon reducible contributions are included and discussed. Previous calculations are extended to the whole kinematical range of the soft photon approximation, thus allowing for the possibility to consider various experimental situations and observables.
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  • 11
    ISSN: 1572-9729
    Keywords: bioremediation ; Dehalococcoides ; dechlorination ; microcosm ; tetrachloroethane ; trichloroethene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract This study investigated the biotransformation pathways of 1,1,2,2-tetrachloroethane (1,1,2,2-TeCA) in the presence of chloroethenes (i.e. tetrachloroethene, PCE; trichloroethene, TCE) in anaerobic microcosms constructed with subsurface soil and groundwater from a contaminated site. When amended with yeast extract, lactate, butyrate, or H2 and acetate, 1,1,2,2-TeCA was initially dechlorinated via both hydrogenolysis to 1,1,2-trichloroethane (1,1,2-TCA) (major pathway) and dichloroelimination to dichloroethenes (DCEs) (minor pathway), with both reactions occurring under sulfidogenic conditions. In the presence of only H2, the hydrogenolysis of 1,1,2,2-TeCA to 1,1,2-TCA apparently required the presence of acetate to occur. Once formed, 1,1,2-TCA was degraded predominantly via dichloroelimination to vinyl chloride (VC). Ultimately, chloroethanes were converted to chloroethenes (mainly VC and DCEs) which persisted in the microcosms for very long periods along with PCE and TCE originally present in the groundwater. Hydrogenolysis of chloroethenes occurred only after highly reducing methanogenic conditions were established. However, substantial conversion to ethene (ETH) was observed only in microcosms amended with yeast extract (200 mg/l), suggesting that groundwater lacked some nutritional factors which were likely provided to dechlorinating microorganisms by this complex organic substrate. Bioaugmentation with an H2-utilizing PCE-dechlorinating Dehalococcoides spp. -containing culture resulted in the conversion of 1,1,2,2-TeCA, PCE and TCE to ETH and VC. No chloroethanes accumulated during degradation suggesting that 1,1,2,2-TeCA was degraded through initial dichloroelimination into DCEs and then typical hydrogenolysis into ETH and VC.
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  • 12
    ISSN: 1572-9729
    Keywords: community fingerprint ; polycyclic aromatic hydrocarbon ; 16S rRNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Microcosm experiments were conduced in which the surface of marine sediment was contaminated with naphthalene and subjected to either of three different bioremediation schemes, i.e., biostimulation (BS) by supplementing with slow-release nitrogen and phosphorus fertilizers, bioaugmentation (BA) by inoculating with Cycloclasticus sp. E2, an aromatics-degrading bacterium identified to play an important role for aromatic-hydrocarbon degradation in marine environments and combination (CB) of BS and BA. These three schemes were found to be similarly effective for removing naphthalene, while naphthalene disappearance in sediment without any treatment (WT) was slower than those in the treated sediments. Shifts in bacterial populations during and after bioremediation were analyzed by denaturing gradient gel electrophoresis (DGGE) of PCR-amplified 16S rRNA gene fragments. It was found that the Cycloclasticus rRNA type occurred as the strongest bands in the course of naphthalene degradation. Clustering analysis of DGGE profiles showed that bacterial populations in the WT, BS and CB sediments differed consistently from those in the uncontaminated control, while the profile for the BA sediment was finally included in the cluster for uncontaminated control sediments after a 150-day treatment. The results suggest that bioaugmentation with ecologically competent pollutant-degrading bacteria is an ecologically promising bioremediation scheme.
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  • 13
    ISSN: 1572-9729
    Keywords: biodegradation ; Burkholderia ; fenitrothion ; mpd gene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A short rod shaped, gram-negative bacterium strain Burkholderia sp. FDS-1 was isolated from the sludge of the wastewater treating system of an organophosphorus pesticides manufacturer. The isolate was capable of using fenitrothion as the sole carbon source for its growth. FDS-1 first hydrolyzed fenitrothion to 3-methyl-4-nitrophenol, which was further metabolized to nitrite and methylhydroquinone. The addition of other carbon source and omitting phosphorus source had little effect on the hydrolysis of fenitrothion. The gene encoding the organophosphorus hydrolytic enzyme was cloned and sequenced. The sequence was similar to mpd, a gene previously shown to encode a parathion-methyl-hydrolyzing enzyme in Plesiomonas sp. M6. The inoculation of strain FDS-1 (106 cells g−1) to soil treated with 100 mg fenitrothion emulsion kg−1 resulted in a higher degradation rate than in noninoculated soils regardless of the soil sterilized or nonsterilized. These results highlight the potential of this bacterium to be used in the cleanup of contaminated pesticide waste in the environment.
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  • 14
    ISSN: 1572-9729
    Keywords: Delftia acidovorans MC1 ; 2,4-dichlorophenoxyacetic acid (2,4-D) ; 2-(2,4-dichlorophenoxy) propanoic acid (2,4-DP) ; effect of tfdK gene ; simultaneous utilization of 2,4-D and 2,4-DP ; uptake characteristics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Growth of Delftia acidovorans MC1 on 2,4-dichlorophenoxyacetic acid (2,4-D) and on racemic 2-(2,4-dichlorophenoxy)propanoic acid ((RS)-2,4-DP) was studied in the perspective of an extension of the strain’s degradation capacity at alkaline pH. At pH 6.8 the strain grew on 2,4-D at a maximum rate (μmax) of 0.158 h−1. The half-maximum rate-associated substrate concentration (Ks) was 45 μM. At pH 8.5 μmax was only 0.05 h−1 and the substrate affinity was mucher lower than at pH 6.8. The initial attack of 2,4-D was not the limiting step at pH 8.5 as was seen from high dioxygenase activity in cells grown at this pH. High stationary 2,4-D concentrations and the fact that μmax with dichlorprop was around 0.2 h−1 at both pHs rather pointed at limited 2,4-D uptake at pH 8.5. Introduction of tfdK from D. acidovorans P4a by conjugation, coding for a 2,4-D-specific transporter resulted in improved growth on 2,4-D at pH 8.5 with μmax of 0.147 h−1 and Ks of 267 μM. Experiments with labeled substrates showed significantly enhanced 2,4-D uptake by the transconjugant TK62. This is taken as an indication of expression of the tfdK gene and proper function of the transporter. The uncoupler carbonylcyanide m-chlorophenylhydrazone (CCCP) reduced the influx of 2,4-D. At a concentration of 195 μM 2,4-D, the effect amounted to 90% and 50%, respectively, with TK62 and MC1. Cloning of tfdK also improved the utilization of 2,4-D in the presence of (RS)−2,4-DP. Simultaneous and almost complete degradation of both compounds occurred in TK62 up to D = 0.23 h−1 at pH 6.8 and up to D = 0.2 h−1 at pH 8.5. In contrast, MC1 left 2,4-D largely unutilized even at low dilution rates when growing on herbicide mixtures at pH 8.5.
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  • 15
    ISSN: 1572-9729
    Keywords: composting ; crude oil ; olive mill wastewater ; olive oil mills ; olive tree branches ; olive tree leaves ; sludge ; woodchips
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The aim of this paper was to evaluate the use of different bulking agents in different ratios as a means to control, optimise and eventually reduce the duration of the thermophilic period in two-phase olive oil mill sludge (OOMS) composting. The bulking agents used were: (i) olive tree leaves (OTL), (ii) olive tree shredded branches (OTB) and (iii) woodchips (WDC). The selection of these materials was based on their abundance and availability on the island of Crete, the southernmost point of Greece. The ratios studied were: Pile 1, OOMS:OTL in 1:1 v/v; Pile 2, OOMS:WDC in 1:1.5 v/v; Pile 3, OOMS:OTL in 1:2 v/v; Pile 4, OOMS:OTL:OTB in 1:1:1 v/v; and Pile 5, OOMS:OTL:OTB in 1:1:2 v/v. The composting system used was that of windrows with the volume of each pile approximately 20–25 m3. The experiments took place over two consecutive years. A composting turner was used and turnings were performed at one and two week intervals. In each pile a variety of physiochemical parameters were monitored. Temperature remained high in all five trials. Piles 1, 2, 3, 4 and 5 temperatures recorded values of above 50 °C for 106, 158, 160, 175 and 183 days, respectively. Volumes were reduced by approximately 67%, 62%, 63%, 80% and 84%, respectively. Temperature remained high, mainly due to the presence in large amounts of oily substances which during their complete oxidation release important amounts of energy and aid the cometabolism of more stable molecules such as lignin. This process is better described as the slow “burning” of a “fuel” mixture in an “engine” than composting. This approach is based on the extensive similarities of this process to that of crude oil sludge or similar waste composting.
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  • 16
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    The European physical journal 46 (2006), S. 247-254 
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: AbstractWe propose a modification of standard linear electrodynamics in four dimensions, where effective non-trivial interactions of the electromagnetic field with itself and with matter fields induce Lorentz violating Chern–Simons terms. This yields two consequences: it provides a more realistic and general scenario for the breakdown of Lorentz symmetry in electromagnetism and it may explain the effective behavior of the electromagnetic field in certain planar phenomena (for instance, Hall effect). A number of proposals for non-linear electrodynamics is discussed along the paper. Important physical implications of the breaking of Lorentz symmetry, such as optical birefringence and the possibility of having conductance in the vacuum are commented on.
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  • 17
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    The European physical journal 46 (2006), S. 69-79 
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: AbstractFirst measurements of $K^\star(892)^\pm$ mesons production properties and their spin alignment in $\nu_\mu$ charged current (CC) and neutral current (NC) interactions are presented. The analysis of the full data sample of the NOMAD experiment is performed in different kinematic regions. For ${K^\star}^+$ and ${K^\star}^-$ mesons produced in $\nu_\mu$ CC interactions and decaying into $K^0 \pi^\pm$ we have found the following yields per event: $(2.6\pm0.2(\text{stat.})\pm0.2(\text{syst.}))\%$ and $(1.6\pm0.1(\text{stat.})\pm0.1(\text{syst.}))\%$ respectively, while for the ${K^\star}^+$ and ${K^\star}^-$ mesons produced in $\nu\text{NC}$ interactions the corresponding yields per event are: $(2.5\pm0.3(\text{stat.})\pm0.3(\text{syst.}))\%$ and $(1.0\pm0.3(\text{stat.})\pm0.2(\text{syst.}))\%$ . The results obtained for the $\rho_{00}$ parameter, $0.40\pm0.06(\text{stat.})\pm0.03(\text{syst.})$ and $0.28\pm0.07(\text{stat.})\pm0.03(\text{syst.})$ for $K^\star(892)^+$ and $K^\star(892)^-$ produced in $\nu_\mu$ CC interactions, are compared to theoretical predictions tuned on LEP measurements in $e^+e^-$ annihilation at the $Z^0$ pole. For $K^\star(892)^+$ mesons produced in $\nu\text{NC}$ interactions the measured $\rho_{00}$ parameter is $0.66\pm0.10(\text{stat.})\pm0.05(\text{syst.})$ .
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  • 18
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    The European physical journal 46 (2006), S. 255-267 
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. In gauge theories parallel transporters (PTs) $\mathcal{U}(C)$ along paths C play an important role. Traditionally they are unitary or pseudoorthogonal maps between vector spaces. We propose to abandon unitarity of parallel transporters and with it the a priori assumption of metricity in general relativity. A *-operation on parallel transporters serves as a substitute for it, and this *-operation is proven to be unique on group theoretical grounds. The vierbein and the spin connection appear as distinguishable parts of a single de Sitter gauge field with field strength F. The action takes the form $\frac{3}{16\pi G\Lambda}\int\text{tr}(\boldsymbol{F}\wedge\boldsymbol{F}i\boldsymbol{\gamma}_{5})$ and both the Einstein field equations with arbitrarily small but nonvanishing cosmological constant Λ and the condition of vanishing torsion are obtained from it. The equation of motion for classical massive bodies turns out to be de Sitter covariant.
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  • 19
    ISSN: 1434-6052
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    Topics: Physics
    Notes: Abstract. High-precision analyses of supersymmetry parameters aim at reconstructing the fundamental supersymmetric theory and its breaking mechanism. A well defined theoretical framework is needed when higher-order corrections are included. We propose such a scheme, Supersymmetry Parameter Analysis SPA, based on a consistent set of conventions and input parameters. A repository for computer programs is provided which connect parameters in different schemes and relate the Lagrangian parameters to physical observables at LHC and high energy e + e- linear collider experiments, i.e., masses, mixings, decay widths and production cross sections for supersymmetric particles. In addition, programs for calculating high-precision low energy observables, the density of cold dark matter (CDM) in the universe as well as the cross sections for CDM search experiments are included. The SPA scheme still requires extended efforts on both the theoretical and experimental side before data can be evaluated in the future at the level of the desired precision. We take here an initial step of testing the SPA scheme by applying the techniques involved to a specific supersymmetry reference point.
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  • 20
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    The European physical journal 46 (2006), S. 81-91 
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    Topics: Physics
    Notes: AbstractWe have reconsidered theoretical upper bounds on the scalar boson masses within the two-Higgs-doublet model (THDM), employing the well-known technical condition of tree-level unitarity. Our treatment provides a modest extension and generalization of some previous results of other authors. We present a rather detailed discussion of the solution of the relevant inequalities and offer some new analytic formulae as well as numerical values for the Higgs mass bounds in question. A comparison is made with the earlier results on the subject that can be found in the literature.
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  • 21
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    The European physical journal 46 (2006), S. 157-178 
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    Topics: Physics
    Notes: AbstractUsing the parallel/orthogonal space method, we calculate the planar two-loop three-point diagram and two rotated reduced planar two-loop three-point diagrams. Together with the crossed topology, these diagrams are the most complicated ones in the two-loop corrections necessary, for instance, for the decay of the Z0 boson. Instead of calculating particular decay processes, we present a new algorithm which allows us to perform arbitrary next-to-next-to-leading order (NNLO) calculations for massive planar two-loop vertex functions in the general mass case. All integration steps up to the last two are performed analytically and will be implemented under xloops as part of the Mainz xloops-GiNaC project. The last two integrations are done numerically using methods like VEGAS and Divonne. Thresholds originating from Landau singularities are found and discussed in detail. In order to demonstrate the numerical stability of our methods we consider particular Feynman integrals which contribute to different physical processes. Our results can be generalized to the case of the crossed topology.
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  • 22
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    The European physical journal 46 (2006), S. 225-233 
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    Topics: Physics
    Notes: AbstractThe functional integration over the auxiliary bosonic variables of cubic order related with the effective action of the Nambu–Jona–Lasinio model with ’t Hooft term has recently been obtained in the form of a loop expansion. Even numbers of loops contribute to the action, while odd numbers of loops are assigned to the measure. We consider the two-loop corrections and analyse their effect on the low-lying pseudoscalar and scalar mass spectra, quark condensates and weak decay constants. The results are compared to the leading order calculations and other approaches.
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  • 23
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    The European physical journal 46 (2006), S. 151-156 
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    Topics: Physics
    Notes: AbstractWe discuss a new leading-order parameterization of generalized parton distributions of the proton, which is based on the idea of duality. In its minimal version, the parameterization is defined by the usual quark singlet parton distributions and the form factors of the energy-momentum tensor. We demonstrate that our parameterization describes very well the absolute value, the Q2-dependence and the W-dependence of HERA data on the total DVCS cross section and contains no free parameters in the HERA kinematics. The parameterization suits the low-xBj region especially well, which allows us to advocate it as a better alternative to the frequently used double distribution parameterization of the GPDs.
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  • 24
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    The European physical journal 46 (2006), S. 113-122 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: AbstractReporting to the Dirac wave-packet prescription where it is formally assumed the fermionic nature of the particles, we shall demonstrate that chiral oscillations implicitly aggregated to the interference between positive and negative frequency components of mass eigenstate wave-packets introduce some small modifications to the standard neutrino flavor conversion formula. Assuming the corresponding spinorial solutions of a ‘modified’ Dirac equation, we are specifically interested in quantifying flavor coupled with chiral oscillations for a fermionic Dirac-type particle (neutrino) non-minimally coupling with an external magnetic field B . The viability of the intermediate wave-packet treatment becomes clear when we assume B orthogonal/parallel to the direction of the propagating particle.
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  • 25
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. We analyze the dependence of heavy quark free energies on the baryon chemical potential μb in 2-flavor QCD by performing a 6th order Taylor expansion in the chemical potential which circumvents the sign problem. The bare quark mass at $\hat m / T = 0.4$ corresponds to a pion mass of about 770 MeV and is thus not in the range of physical quark masses but the quark mass dependence is known to be small above Tc. At Nτ = 4 the lattices are coarse, however, we are using improved (p4 staggered) fermions. The Taylor expansion coefficients of color singlet and color averaged free energies are calculated and from this the expansion coefficients for the corresponding screening masses are determined. We find that for small μb the free energies of a static quark-antiquark pair decrease in a medium with a net excess of quarks and that screening is well described by a screening mass which increases with increasing μb. The μb-dependent corrections to the screening masses are well described by perturbation theory for T ≳ 2Tc. In particular, we find for all temperatures above Tc that the expansion coefficients for singlet and color averaged screening masses differ by a factor 2.PACS. 11.15.Ha, 11.10.Wx, 12.38Gc, 12.38.Mh
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    The European physical journal 46 (2006), S. 235-245 
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. We consider the possibility that photons of noncommutative U(1) gauge theory can make bound states. Using the potential model, developed based on the constituent gluon picture of QCD glue-balls, arguments are presented in favor of the existence of these bound states. The basic ingredient of the potential model is that the self-interacting massless gauge particles may get mass by the inclusion of non-perturbative effects.PACS. 02.40.Gh, 11.10.Nx, 12.20.-m
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  • 27
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    The European physical journal 46 (2006), S. 135-145 
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. In this paper we derive an evolution equation for the gluon density in soft gluon cascades emitted from any colored source, in the leading logarithmic approximation of perturbative QCD. We show that this equation has the same form as the BFKL equation in the forward case. An explicit expression for the total cascade wavefunction involving an arbitrary number of soft gluons is obtained. Renormalization of the colored source wavefunction turns out to be responsible for the reggeization of the source.
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  • 28
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    Biodegradation 17 (2006), S. 207-217 
    ISSN: 1572-9729
    Keywords: biodegradation ; DGGE ; K2Ni(CN)4 soil bacterial populations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Metal cyanides are significant contaminants of many soils found at the site of former industrial activity. In this study we isolated bacteria capable of degrading ferric ferrocyanide and K2Ni(CN)4. One of these bacteria a Rhodococcus spp. was subsequently used to bioaugment a minimal medium broth, spiked with K2Ni(CN)4, containing 1 g of either an uncontaminated topsoil or a former coke works site soil. Degradation of the K2Ni(CN)4 was observed in both soils, however, bioaugmentation did not significantly impact the rate or degree of K2Ni(CN)4 removal. Statistical analysis of denaturing gradient gel electrophoresis profiles showed that the topsoil bacterial community had a higher biodiversity, and its structure was not significantly affected by either K2Ni(CN)4 or bioaugmentation. In contrast, profiles from the coke works site indicated significant changes in the bacterial community in response to these additions. Moreover, in both soils although bioaugmentation did not affect rates of biodegradation the Rhodococcus spp. did become established in the communities in broths containing both top and coke works soil. We conclude that bacterial communities from contaminated soils with low biodiversity are much more readily perturbed through interventions such as contamination events or bioaugmentation treatments and discuss the implications of these findings for bioremediation studies.
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  • 29
    ISSN: 1572-9729
    Keywords: acetochlor ; degradation ; isolation ; Pseudomonas oleovorans
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract To date, no pure bacterial cultures that could degrade acetochlor have been described. In this study, one strain of microorganism capable of degrading acetochlor, designated as LCa2, was isolated from acetochlor-contaminated soil. The strain LCa2 is Pseudomonas oleovorans according to the criteria of Bergey’s manual of determinative bacteriology and sequence analysis of the partial 16S rRNA gene. Optimum growth temperature and pH were 35 °C and 8.0, respectively. The strain could degrade 98.03% of acetochlor treated at a concentration of 7.6 mg l−1 after 7 days of incubation and could tolerate 200 mg l−1 of acetochlor. When the acetochlor concentration became higher, the degradation cycle became longer. The acetochlor biodegradation products were identified by GC–MS based on mass spectral data and fragmentation patterns. The main plausible degradative pathways involved dechlorination, hydroxylation, N-dealkylation, C-dealkylation and dehydrogenation.
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  • 30
    ISSN: 1572-9729
    Keywords: bioremediation ; composting ; ecotoxicity ; oil sludge
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The present work attempts to ascertain the efficacy of low cost technology (in our case, composting) as a bioremediation technique for reducing the hydrocarbon content of oil refinery sludge with a large total hydrocarbon content (250–300 g kg−1), in semiarid conditions. The oil sludge was produced in a refinery sited in SE Spain The composting system designed, which involved open air piles turned periodically over a period of 3 months, proved to be inexpensive and reliable. The influence on hydrocarbon biodegradation of adding a bulking agent (wood shavings) and inoculation of the composting piles with pig slurry (a liquid organic fertiliser which adds nutrients and microbial biomass to the pile) was also studied. The most difficult part during the composting process was maintaining a suitable level of humidity in the piles. The most effective treatment was the one in which the bulking agent was added, where the initial hydrocarbon content was reduced by 60% in 3 months, compared with the 32% reduction achieved without the bulking agent. The introduction of the organic fertiliser did not significantly improve the degree of hydrocarbon degradation (56% hydrocarbon degraded). The composting process undoubtedly led to the biodegradation of toxic compounds, as was demonstrated by ecotoxicity tests using luminescent bacteria and tests on plants in Petri dishes.
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  • 31
    ISSN: 1572-9729
    Keywords: activated sludge ; dichlorophenol ; monooxygenation ; nicotinamide adenine dinucleotide ; phenolics ; specific growth rate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The two-tank accelerator/aerator modification of activated sludge significantly increases the biodegradation of hydrocarbons requiring initial monooxygenation reactions, such as phenol and 2,4-dichlorophenol (DCP). The small accelerator tank has a controlled low dissolved oxygen (DO) concentration that can enrich the biomass in NADH + H+. It also has a very high specific growth rate (μacc) that up-regulates the biomass’s content of the monooxygenase enzyme. Here, we develop and test the ACCEL model, which quantifies all key phenomena taking place when the accelerator/aerator system is used to enhance biodegradation of hydrocarbons requiring initial monooxygenations. Monooxygenation kinetics follow a multiplicative relationship in which the organic substrates (phenol or DCP) and DO have separate Monod terms, while the biomass’s content of NADH + H+ has a first-order term. The monooxygenase enzyme has different affinities (K values) for phenol and DCP. The biomass’s NADH + H+ content is based on a proportioning of NAD(H) according to the relative rates of NADH + H+ sources and sinks. Biomass synthesis occurs simultaneously through utilization of acetate, phenol, and DCP, but each has its own true yield. The ACCEL model accurately simulates all trends for one-tank and two-tank experiments in which acetate, phenol, and DCP are biodegraded together. In particular, DCP removal is affected most by DOacc and the retention-time ratio, Θacc/Θtotal. Adding an accelerator tank dramatically increases DCP removal, and the best DCP removal occurs for 0.2 〈 DOacc  〈 0.5 mg/l and 0.08 〈 Θacc/Θtotal 〈 0.2. The rates of phenol and DCP utilization follow the multiplicative relationship with a maximum specific rate coefficient proportional to μacc. Finally, μacc increases rapidly for Θacc/Θtotal 〈 0.25, acetate removal in the accelerator fuels the high μacc, and the biomass’s NADH + H+ content increases very dramatically for DOacc 〈 0.25 mg/l.
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  • 32
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    Physiologia plantarum 125 (2005), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Wounding, as during excision and preparation of lettuce (Lactuca sativa L.) leaf tissue for salads, induces the synthesis and accumulation of phenolic compounds that participate in subsequent reactions that cause tissue browning. Exposure of excised 5-mm mid-rib segments of romaine lettuce leaf tissue to vapors of mono-carboxylic acids or aqueous solutions of mono-carboxylic acids or their salts inhibited wound-induced phenolic accumulation (WIPA) and subsequent tissue browning. The decline in phenolic content followed a quadratic curve with increasing concentration, reaching a maximum inhibition after 60 min of 74 ± 8% for 50 mM sodium acetate (2 carbons, C2) and 91 ± 4% for 20 mM sodium decanoate (capric acid, C10). Respiration (i.e. carbon dioxide production) was unaffected by concentrations of formic, acetic, or propionic acids that reduced wound-induced phenolic content or that increase ion leakage from the tissue into an isotonic mannitol solution. However, WIPA was suppressed up to 70% at concentrations (20 mM acetate) that did not increase ion leakage over that of water controls. Various acetate salts (i.e. ammonium, calcium, magnesium, and sodium) all produced the same level of inhibition. The effectiveness of the compounds increased with increasing number of carbons in the molecule from 1 to 10, and was unaffected by whether the carbons were a straight chain or branched or whether the treatment was delayed by up to 6 h. The effectiveness of butyrate (C4) in reducing WIPA (27% reduction at 20 mM) was less than that predicted from the response of the two adjacent mono-carboxylates similarly applied: propionate (C3) (62%) and valerate (C5) (73%). It appears that, unlike the n-alcohols, mono-carboxylates are not interfering with the synthesis or propagation of a wound signal but are interfering with subsequent steps in the production and accumulation of wound-induced phenolic compounds.
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    Physiologia plantarum 125 (2005), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Pearl millet, Pennisetum glaucum, is capable of adapting to severely dry environmental conditions. In order to elucidate the mechanism of adaptation to highly dehydrated conditions, we selected both tolerant (IP8210) and susceptible (IP8949) accessions from a total of 15 pearl millet accessions and characterized their morphological and physiological responses to severe drought stress. When these selected accessions were stressed with a severe drought treatment, the leaves of IP8210 exhibited upright folding, a response that effectively reduces the evaporative surface area of the canopy. On the contrary, the leaves of IP8949 exhibited wilting and did not appear to adapt to the drought stress. In comparison with IP8949, the capacity of osmotic adjustment (OA) was greater in both younger leaves and stems of IP8210, while their decrease in relative water content was different. IP8210 accumulated higher concentrations of NO3– than IP8949 in response to drought stress. In addition to inorganic solutes, several organic components such as sucrose, glucose, quaternary ammonium compounds, and amino acids including proline were also accumulated. IP8210 tended to accumulate more amino acids, typically due to the accumulation of asparagine and proline, while IP8949 accumulated more soluble sugars. While it is possible that K+ and NO3– were the major components contributing to osmotic regulations, sugars and amino acids might also function as a cytoprotectant, in addition to their role as osmoprotectants. Collectively, these results demonstrate that the morphological adaptation of leaf folding, OA in both the younger leaves and the stem, and the accumulation of NO3– and amino acids during earlier stress period contribute to superior drought tolerance that was exhibited in IP8210 of pearl millet.
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  • 34
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    Physiologia plantarum 125 (2005), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The C3 halophyte Suaeda salsa L. grown under the high concentration of NaCl (200 mM) was used to investigate the role of the hydrogen peroxide (H2O2)-scavenging system [catalase, ascorbate peroxidase, glutathione reductase (GR), ascorbic acid, and glutathione (GSH)] in removal of reactive oxygen species. The activity of catalase (CAT, EC 1.11.1.6), ascorbate peroxidase (APX, EC 1.11.1.11), and GR (EC 1.6.4.2) increased significantly after 7 days of NaCl treatment. The isoform patterns of CAT and GR were not affected, but the staining intensities were significantly increased by NaCl treatment. Activities of both the thylakoid-bound APX or GR and stromal APX (S-APX) or GR in the chloroplasts were markedly enhanced under high salinity. Fifty percent of APX in the chloroplasts is thylakoid-bound APX. S-APX and GR activity represented about 74–78 and 64–71% of the total soluble leaf APX and GR activity, respectively. Salt treatment increased the contents of ascorbic acid and GSH. By contrast, a decreased content of H2O2 was found in the leaves of NaCl-treated S. salsa. The level of membrane lipid peroxidation decreased slightly after NaCl treatment. The plants grew well with high rate of net photosynthesis under high salinity. These data suggest that upregulation of the H2O2-scavenging system in plant cells, especially in the chloroplasts, is at least one component of the tolerance adaptations of halophytes to high salinity.
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  • 35
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    Physiologia plantarum 125 (2005), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The photosynthetic performance of the cyanobacterium Synechocystis sp. PCC 6803 exposed to intermittent light was studied by measuring oxygen evolution, respiration and the fluorescence parameters for maximum efficiency of excitation energy capture by photosystem II (PSII) reaction centres (Fv/Fm), PSII quantum yield (ΔF/Fm1) and non-photochemical quenching (NPQ). Cultures were pre-acclimated to constant light conditions. Block and sinusoidal light regimes were tested using four photon-flux densities (PFDs) applied in light/dark intervals of 1:1, 5:5 and 10:10 min. Light use was higher under the sinusoidal light regime compared with the block regime. The accumulated gross photosynthesis of the cyanobacterium was lower under intermittent light conditions compared with predictions from the photosynthesis-irradiance curve (PI curve). The respiration rates were similar for all light/dark intervals tested. However, the respiration slightly increased with increasing oxygen production for both block and sinusoidal light regime. NPQ, ΔF/Fm′ and Fv/Fm depended on the PFD rather than on the duration of the light/dark intervals tested, and there was no detected influence of the two applied light regimes.
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  • 36
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    Physiologia plantarum 125 (2005), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Fructose analog, psicose, and glucose analog, mannose, inhibited root growth of lettuce seedlings. Psicose is phosphorylated by hexokinase and fructokinase (EC 2.7.1.4) to psicose-6-phosphate with no known capacity for further metabolism. Mannose is phosphorylated by hexokinase (EC 2.7.1.1) to mannose-6-phosphate which is further metabolized very slowly. Hexokinase is known to have a sugar-sensing function and possibly triggers a signal cascade resulting in changes of several gene expressions. It was determined, compared with the behaviour of mannose, whether psicose inhibits the root growth through this system. The addition of phosphate into the growth medium of lettuce seedlings did not affect the inhibition by psicose and mannose, and both sugars did not reduce adenosine triphosphate (ATP) level in the roots, suggesting that the inhibition is not due to phosphate starvation and ATP depletion. The inhibiting effects of psicose and mannose were overcome by adding sucrose into the medium, which suggests that the inhibition is not caused by accumulation of psicose-6-phosphate or mannose-6-phosphate in the seedlings. Mannoheptulose, a specific competitive inhibitor of hexokinase, defeated the mannose-induced inhibiting but was not able to relieve the psicose-induced inhibition. Thus, the phosphorylation of mannose by hexokinase may trigger a signal cascade resulting in the growth inhibition of lettuce roots, which is consistent with the hypothesis established in Arabidopsis. However, psicose cannot inhibit the growth of lettuce roots via a hexokinase-mediated pathway, and the phosphorylation of psicose by fructokinase might trigger a hexokinase-independent signal cascade resulting in the growth inhibition.
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    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The pools of photoprotective molecules respond to changes in the environmental conditions and sometimes to leaf ageing. We asked to what extent both factors contribute to the contents of α-tocopherol and xanthophyll cycle [V + A + Z (VAZ)] pigments. To address this question, we used boxtree (Buxus sempervirens) as model species because its leaves are long-lived and evergreen and are subjected to a succession of different stress conditions during their lifespan. In three age classes of sun and shade leaves of this species, seasonal changes in photoprotective compounds were followed during 15 months and a leaf age interval of 40 months was covered. As could be expected, VAZ and α-tocopherol pools increased in parallel during stress periods (summer and winter), but only VAZ recovered to the initial pools once stress disappeared. As a result, the basal α-tocopherol level increased linearly in a time-dependent manner that was also higher in sun leaves of this species when compared with shade leaves, and in fact, the rate of tocopherol increase was directly proportional to irradiance in another evergreen (Laurus nobilis). To study whether light dependency of tocopherol accumulation is observed in other species, we performed a literature survey that revealed that this age-dependent tocopherol increase was significant in sun leaves from 65% of the species for which age-dependent tocopherol changes have been reported, and it was on average 2.2-fold higher in sun leaves as compared with shade leaves. We conclude that there are two components in the α-tocopherol pool, one dynamic that responds to environmental changes and one age-related which increases linearly with time in a light-dependent manner. The physiological meaning of the latter remains obscure.
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  • 38
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: B-function genes determine the identity of petals and stamens in the flowers of model plants such as Arabidopsis and Antirrhinum. Here, we show that a putative B-function gene BpMADS2, a birch homolog for PISTILLATA, is expressed in stamens and carpels of birch inflorescences. We also present a novel birch gene BpMADS8, a homolog for APETALA3/DEFICIENS, which is expressed in stamens. Promoter-GUS analysis revealed that BpMADS2 promoter is active in the receptacle of Arabidopsis flower buds while BpMADS8 promoter is highly specific in mature stamens. BpMADS2 promoter::BARNASE construct prevented floral organ development in Arabidopsis and tobacco. In birch, inflorescences with degenerated stamens and carpels were obtained. BpMADS8::BARNASE resulted in degeneration of stamens in Arabidopsis and birch causing male sterility. In tobacco, only sepals were developed instead of normal flowers. The results show that the BpMADS2::BARNASE construct can be used to specifically disrupt floral organ development in phylogenetically distant plant species. The stamen-specific promoter of BpMADS8 is a promising tool for biotechnological applications in inducing male sterility or targeting gene expression in the late stamen development.
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  • 39
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    Physiologia plantarum 125 (2005), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: We have used yeast two-hybrid screens and biochemical methods to identify glycolytic enzymes that interact with subcellular structures in hypoxic maize seedlings. As binding domain-bait fusion constructs, we have cloned actin, cytosolic aldolase, the three sucrose synthase (SUS) isoforms SUS1, SUS3, and SH1 as well as the SNF1-related protein kinase into yeast and identified cytosolic isoforms of glyceraldehyde 3-phosphate dehydrogenase (GAPDH), enolase, tubulin, and mitochondrial porin voltage-dependent anion channel protein (VDAC) as well as protein kinases and proteins involved in ubiquitinylation and proteasome-linked degradation as interacting activation domain-prey clones. The results were further confirmed using overlay blots (VDAC) as well as co-polymerization and co-precipitation assays (tubulin and actin). Some results were obtained that support the idea of metabolite and modification effects on the association, namely guanosine triphosphate (GTP)/MgCl2 was necessary for the binding of enolase to actin. GAPDH is inactivated upon association with tubulin but then serves to stabilize the microtubules. The findings support the idea of the dynamic formation of locally associated complexes of enzymes involved in sucrose breakdown and glycolysis in plant cells depending on their metabolic state.
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  • 40
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    Physiologia plantarum 125 (2005), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Acid invertases play a key role in sugar metabolism, and the plant hormone abscisic acid (ABA) enhances sugar accumulation in crop sink organs, but information about the relationship between ABA and acid invertases has been limited. The present experiments were done with both in vivo pre-incubation of the grape (Vitis vinifera × V. labrusca L.) berry tissues in ABA-containing medium and in vivo infiltration of ABA into the intact berries. The results show that ABA activates both the soluble and cell wall-bound acid invertases during fruit development by enhancing their activities and amounts as assessed by immunoblotting or enzyme-linked immunosorbent assay. This activation was pH, time course and ABA dose dependent. The serine/threonine protein kinase inhibitors K252a, staurosporine and H7 and acid phosphatase increased the activation of ABA-induced acid invertase, but the tyrosine protein kinase inhibitor quercetin strongly suppressed the ABA-induced effects, suggesting that a complex reversible protein phosphorylation is involved in the ABA-induced activation of acid invertases. The effects of the protein kinase inhibitors were dependent on the in vivo state of the tissues but independent of the expression of acid invertases. Two ABA analogues, (–)-ABA and trans-ABA, had no effect on acid invertases, showing that the ABA-induced activation of acid invertases is specific to the physiologically active form of ABA. These data suggest that ABA may be involved in fruit development by activating acid invertases.
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  • 41
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    Topics: Biology
    Notes: Onions were grown in environmentally controlled growth chambers for 85 days to investigate the effect of relatively low light intensity (350 µmol m−2 s−1) at two different total irradiance periods (12-h and 24-h photoperiods) on growth and photosynthetic performance. To test whether photosynthetic downregulation occurred due to carbohydrate feedback, we used onions that differed in bulb-forming capacity. Allium fistulosum (L. cv. ‘Kinka’) is a non-bulbing onion, with potentially limited carbohydrate storage capacity, while Allium cepa (L. cv. ‘Cal 296’) is a bulb-forming onion with possibly greater carbohydrate storage capacity. In A. fistulosum, photosynthetic downregulation was observed in 24-h plants as indicated by reductions in the light- and CO2-saturated photosynthetic capacity (Asat and Amax, respectively) by 26%, reduced maximum rate of carboxylation (Vcmax) by ribulose-1,5-biphosphate carboxylase/oxygenase (Rubisco) by 33%, reduced maximum rate of electron transport (Jmax) by 27% and 3-fold higher foliar sugar concentration. In contrast, the photosynthetic and biochemical capacity of A. cepa was not affected by exposure to 24-h photoperiod, presumably because substantial amounts of foliar carbohydrates were re-allocated to bulbs. In 24-h A. cepa, up to 84% of total plant mass was allocated to bulbs, while in 12-h plants, more mass was allocated to leaves. Production of greater leaf area in 12-h plants compared with 24-h plants compensated for lower total daily irradiance such that 12-h and 24-h plants of both species exhibited similar daily total leaf net CO2 exchange and plant mass at the end of the experiment.
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    Physiologia plantarum 125 (2005), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Few studies have investigated the interaction of ultraviolet (UV)-B radiation and CO2 concentration on plants. We studied the combined effects of UV-B radiation and CO2 concentration on canola (Brassica napus cv. 46A65) under four growth conditions – ambient CO2 with UV-B (control), elevated CO2 with UV-B, ambient CO2 without UV-B, and elevated CO2 without UV-B – to determine whether the adverse effects of UV-B are mitigated by elevated CO2. Elevated CO2 significantly increased plant height and seed yield, whereas UV-B decreased them. Elevated CO2 ameliorated the adverse effects of UV-B in plant height. UV-B did not affect the physical characteristics of leaf but CO2 did. Certain flower and fruit characteristics were affected negatively by UV-B and positively by CO2. UV-B did not affect net photosynthesis, transpiration and stomatal conductance but decreased water use efficiency (WUE). Elevated CO2 significantly increased net photosynthesis and WUE. Neither UV-B nor CO2 affected chlorophyll (Chl) fluorescence. UV-B significantly decreased Chl b and increased the ratio of Chl a/b. Elevated CO2 decreased only the ratio of Chl a/b. UV-B significantly increased UV-absorbing compounds while CO2 had no effect on them. Both UV-B and CO2 significantly increased epicuticular wax content. Many significant relationships were found between morphological, physiological, and chemical parameters. This study showed that elevated CO2 can partially ameliorate some of the adverse effects of UV-B radiation in B. napus.
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    Physiologia plantarum 125 (2005), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Xyloglucan endotransglucosylase/hydrolases (XTHs) are thought to be involved in various aspects of plant development by modifying the structure of xyloglucan cross-links. To address one of the roles of XTHs in plant growth, we identified an XTH, VrXTH1, in the mungbean through a differential reverse transcriptase-polymerase chain reaction. The deduced amino acid sequence of VrXTH1 shows high similarity to other XTHs. In addition, a signal peptide consisting of 17 amino acids is found at the N-terminus. The gene expression of VrXTH1 was differentially regulated in tissues and was higher in hypocotyls and stems than it was in other tissues. The steady state level of VrXTH1 transcripts was closely related to the elongation regions of hypocotyls. Notably, in the elongation region of hypocotyls, most VrXTH1 mRNAs were limited to the epidermis and to some layers of the cortex that act as growth-limiting tissue. Growth-promoting hormones, such as auxin and brassinolide, strongly enhanced mRNA accumulation of VrXTH1. However, abscisic acid, a hormone which is antagonistic to auxin, acted as a downregulator. Overall, VrXTH1 seems to play a role in plant growth at the gene level and, thus, by possibly altering cell wall morphogenesis in mungbean hypocotyls.
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    Physiologia plantarum 125 (2005), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The light-induced de-epoxidation of xanthophylls is an important photoprotective mechanism in plants and algae. Exposure to ultraviolet radiation (UVR, 280–400 nm) can change the extent of xanthophyll de-epoxidation, but different types of responses have been reported. The de-epoxidation of violaxanthin (V) to zeaxanthin (Z), via the intermediate antheraxanthin, during exposure to UVR and photosynthetically active radiation (PAR, 400–700 nm) was studied in the marine picoplankter Nannochloropsis gaditana (Eustigmatophyceae) Lubián. Exposures used a filtered xenon lamp, which gives PAR and UVR similar to natural proportions. Exposure to UVR plus PAR increased de-epoxidation compared with under PAR alone. In addition, de-epoxidation increased with the irradiance and with the inclusion of shorter wavelengths in the spectrum. The spectral dependence of light-induced de-epoxidation under UVR and PAR exposure was well described by a model of epoxidation state (EPS) employing a biological weighting function (BWF). This model fit measured EPS in eight spectral treatments using Schott long pass filters, with six intensities for each filter, with a R2 = 0.90. The model predicts that 56% of violaxanthin is de-epoxidated, of which UVR can induce as much as 24%. The BWF for EPS was similar in shape to the BWF for UVR inhibition of photosynthetic carbon assimilation in N. gaditana but with about 22-fold lower effectiveness. These results demonstrate a connection between the presence of de-epoxidated Z and the inhibition under UVR exposures in N. gaditana. Nevertheless, they also indicate that de-epoxidation is insufficient to prevent UVR inhibition in this species.
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  • 45
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    Physiologia plantarum 125 (2005), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SULTR2;1 is a low-affinity sulfate transporter expressed in the vascular tissues of roots and leaves for interorgan transport of sulfate in Arabidopsis thaliana. Transgenic Arabidopsis carrying a fusion gene construct of SULTR2;1 5′-promoter region and β-glucuronidase coding sequence (GUS) demonstrated that within the reproductive tissues, SULTR2;1 is specifically expressed in the bases and veins of siliques and in the funiculus, which connects the seeds and the silique. The antisense suppression of SULTR2;1 mRNA caused decrease of sulfate contents in seeds and of thiol contents both in seeds and leaves, as compared with the wildtype (WT). The effect of antisense suppression of SULTR2;1 on seed sulfur status was determined by introducing a sulfur-indicator construct, p35S::βSRx3:GUS, which drives the expression of GUS reporter under a chimeric cauliflower mosaic virus 35S promoter containing a triplicate repeat of sulfur-responsive promoter region of soybean β-conglycinin β subunit (βSRx3). The mature seeds of F1 plants carrying both the SULTR2;1 antisense and p35S::βSRx3:GUS constructs exhibited significant accumulation of GUS activities on sulfur deficiency, as compared with those carrying only the p35S::βSRx3:GUS construct in the WT background. These results suggested that SULTR2;1 is involved in controlling translocation of sulfate into developing siliques and may modulate the sulfur status of seeds in A. thaliana.
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  • 46
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    Physiologia plantarum 125 (2005), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The expression of totipotency in plant protoplasts is a complex developmental phenomenon and is affected by genetic and physiological factors. Polyamines (PAs) are known to be involved in a variety of growth and developmental processes in higher plants, as well as in adaptation to stresses. In this study, we present the homeostatic characteristics of the endogenous PA putrescine (Put), spermidine (Spd), and spermine (Spm) in totipotent (T) and non-totipotent (NT) tobacco protoplasts and in recalcitrant (R) grapevine protoplasts. T-tobacco protoplasts, with high division rates, have the highest level of endogenous PAs. In these protoplasts, the soluble-hydrolyzed fraction predominates and increases, and the insoluble-hydrolyzed fraction also increases, whereas soluble (S) PAs decrease rapidly during culture. The isolation process contributes to the increased Put levels, which are higher in freshly isolated NT-tobacco protoplasts than in T-protoplasts. During culture, total Put predominates over Spd and Spm, and the highest accumulation is found in T-protoplasts. Ornithine decarboxylase and arginase activities both increase in T-protoplasts, whereas arginine decarboxylase activity causes Put accumulation in NT-tobacco protoplasts. R-grapevine protoplasts show a different PA profile, mostly due to the lower PA content, the higher S-fraction, and the higher ratio of Spm to total PAs. The data suggest that the levels and metabolism of the intracellular PAs could be related to the expression of totipotency of plant protoplasts.
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  • 47
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    Physiologia plantarum 124 (2005), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In the southeast of the Qinghai-Tibetan Plateau of China, sea buckthorn (Hippophae rhamnoides L.), which is a thorny nitrogen-fixing deciduously perennial shrub, has been widely used in forest restoration as the pioneer species. In our study, two contrasting populations from the low and high altitudinal regions were employed to investigate the effects of drought, ultraviolet-B (UV-B) and their combination on sea buckthorn. The experimental design included two watering regimes (well watered and drought stressed) and two levels of UV-B (with and without UV-B supplementation). Drought significantly decreased total biomass, total leaf area and specific leaf area (SLA), and increased root/shoot ratio, fine root/coarse root ratio and abscisic acid content (ABA) in both populations. However, the high altitudinal population was more responsive to drought than the low altitudinal population. On the other hand, elevated UV-B induced increase in anthocyanins in both populations, whereas the accumulation of UV-absorbing compounds occurred only in the low altitudinal population. The drought-induced enhancement of ABA in the high altitudinal population was significantly suppressed in the combination of drought and elevated UV-B. Moreover, significant drought × UV-B interaction was detected on total biomass in both populations, total leaf area and fine root/coarse root in the low altitudinal population, and SLA in the high altitudinal population. These results demonstrated that there were different adaptive responses between two contrasting populations, the high altitudinal population exhibited higher tolerance to drought and UV-B than the low altitudinal population.
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  • 48
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Deoxyhypusine synthase (DHS; EC 2.5.1.46) mediates the first of two enzymatic reactions that convert inactive eukaryotic translation initiation factor-5A (eIF-5A) to an activated form, thought to facilitate translation. A full-length cDNA clone encoding canola (Brassica napus cv. Westar) DHS was isolated from a cDNA-expression library prepared from senescing leaves. Transgenic canola lines with suppressed DHS expression were obtained by introducing a transgene expressing antisense 3′-UTR canola DHS cDNA under the regulation of the constitutive cauliflower mosaic virus 35S (CaMV-35S) promoter. Transformed seed was obtained by vacuum infiltration of canola inflorescences using the protocol developed for Arabidopsis with modifications. The resultant transgenic plants had reduced levels of leaf DHS protein and exhibited delayed natural leaf senescence. Suppression of DHS also increased leaf size by 1.5- to two-fold and resulted in increases in seed yield of up to 65%. Moreover, the enhanced performance of transgenic plants reflected increased tolerance to chronic sublethal stress. When wild-type and transgenic plants were grown in 6-inch pots, the increase in seed yield accruing from suppression of DHS was approximately 4.5-fold greater than when the plants were grown in 12-inch pots. Thus, suppression of DHS appears to ameliorate the effects of sublethal stress engendered by growth in small containers.
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  • 49
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    Physiologia plantarum 124 (2005), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In higher plants, the xylem vessels functionally connect the roots with the above-ground organs. The xylem sap transports various organic compounds, such as proteins and amino acids. We examined drought and rewatering-inducible changes in the amino acid composition of root xylem sap collected from Cucurbita maxima roots. The major free amino acids in C. maxima root xylem sap were methylglycine (MeGly; sarcosine) and glutamine (Gln), but MeGly was not detected in the xylem sap of cucumber. MeGly is an intermediate compound in the metabolism of trimethylglycine (TMG; betaine), but its physiological effects in plants are unknown. Drought and rewatering treatment resulted in an increase in the concentration of MeGly in root xylem sap to 2.5 mM. After flowering, the MeGly concentration in the xylem sap dropped significantly, whereas the concentration of Gln decreased only after fruit ripening. One milli molar MeGly inhibited the formation of adventitious roots and their elongation in C. maxima, but glycine, dimethylglycine, or TMG had no effect. Similar effects and the inhibition of stem elongation were observed in shoot cuttings of cucumber and Phaseolus angularis. These observations seem to imply a possible involvement of xylem sap MeGly in the physiological responses of C. maxima plants to drought stress.
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  • 50
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    Physiologia plantarum 124 (2005), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In this work we present the first study of the behaviour of tobacco plants, under saline conditions, grafted to salinity-resistant rootstocks of tomato cultivars. To test the viability and efficiency of this grafting technique in tobacco plants subjected to salinity, we analyse the production of foliar biomass and different quality parameters in this crop. With this aim, Nicotiana tabacum cv. Sevilla (scion) was grafted to two cultivars of Lycopersicum esculentum (rootstocks): cv. Jaguar (Sevilla/Jaguar) and cv. Brillante (Sevilla/Brillante). Furthermore, as controls, tobacco plants of cv. Sevilla were used grafted to themselves (Sevilla/Sevilla) and non-grafted plants of cv. Sevilla. Plants were grafted by needle graft following the procedure described by Rivero RM, Ruiz JM, Romero L (2002) Role of grafting in horticultural plants, pp 229–254. In the present work, we demonstrate that the graft of tobacco scions with tomato rootstocks is an effective agricultural approach to improve production and quality in tobacco leaves under conditions of saline stress. Our results show that the rootstock of the cv. Brillante best induced salt resistance in tobacco cv. Sevilla, registering the lowest foliar concentrations of Na+ and Cl–, the lowest lipid peroxidation and the highest proline and sugar concentrations. Overall, this is reflected in better biomass production of the aerial part of the plant. Finally, it is noteworthy that grafting in tobacco plants to tomato rootstocks essentially eliminates foliar nicotine levels (reduced to 1%). These results are of great importance, as this technique implies a rapid, efficient and natural alternative in increasing tobacco-leaf quality and thus reducing harmful effects of this alkaloid on the health of smokers.
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  • 51
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    Physiologia plantarum 124 (2005), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Cucumber seedling radicles decrease in chilling tolerance as they increase in length or decrease in vigor. The protein content of the apical 5 mm of the radicle decreased with decreases in chilling tolerance (R2 = 0.92). This general reduction in protein content was reflected in a decrease of six dehydrin-like proteins with apparent molecular weights of 13.0, 15.0, 16.8, 23.0, 26.8, and 33.5 kDa. The disappearance of naturally occurring dehydrin-like proteins in cucumber seedling radicles as they elongate or lose vigor was correlated with a loss of chilling tolerance. Exposure to an osmotic (0.6 M mannitol) or heat (2 min at 45°C) stress enhanced chilling tolerance. The osmotic-shock treatment induced both chilling tolerance and the appearance or strengthening of dehydrin-like proteins previously present in radicles. The heat-shock treatment also induced high levels of chilling tolerance and protein(s) that reacted with a 23 and 70 kDa antibody. However, these heat-shock protein (HSPs) did not cross react with the probe for dehydrin-like proteins. When organized into high, medium, and low chilling tolerance groups, radicle that were chilling tolerant contained either the 13.0 and 16.8 kDa dehydrin-like proteins, or the 15.0 and 23.0 kDa dehydrin-like proteins, or the 23 or 70 kDa HSP.
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  • 52
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    Physiologia plantarum 124 (2005), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Despite the major impacts of fire on plants, responses to fire damage have not been closely studied on the level of gene expression. Here, we present analyses of novel transcripts from tomato (Lycopersicon esculentum cv. Heinz), which are systemically upregulated in leaves after a distant leaf is wounded by flame. Nine cDNA fragments were isolated from a subtractive cDNA library of leaf tissue 1 h after flaming. Using data mining and polymerase chain reaction (PCR), full-length open-reading frames were predicted, amplified, and then sequenced. Real-time (RT)-PCR using leaf RNA after flaming confirmed the systemic accumulation of 4 and 7 transcripts within 30 and 60 min, respectively, before returning to basal levels within 3 h. During this same time course, proteinase inhibitor I levels gradually increased over 30-fold in 6 h. Expression analyses also showed that eight of the transcripts are present in unwounded leaf, stem, and root tissues. The predicted proteins include an acyl carrier, adenylyl sulfate reductase, PS II oxygen-evolving complex protein 3, anion : sodium symporter, chloroplast-specific ribosomal protein, a histidine triad family protein, and an unknown wound/stress-related protein. Homologs of several of these proteins have been associated with other types of wound and stress responses. It appears that, within an hour after being damaged by fire, plants systemically upregulate a variety of genes involved with basic cell metabolism and upkeep, in addition to classic defense genes such as proteinase inhibitors.
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  • 53
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    Physiologia plantarum 124 (2005), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Among the longest cell types known in plants, cotton fibers are economically important seed trichomes that provide a unique single-celled model system for studying fundamental biological processes. Functional genomic approaches have served to characterize dynamic changes to the cotton fiber transcriptome in response to developmental signals that control fiber morphogenesis at the level of a single cell. The genetic complexity of the fiber transcriptome is very high and accounts for as much as 45–50% of the genes in the cotton genome. In addition to a large diverse group of constitutively expressed genes, expression profiling of the transcriptome revealed two developmentally regulated stage-specific expression patterns that define rapid cell elongation during primary cell wall (PCW) synthesis relative to secondary cell wall biogenesis. In developing cotton fibers, many fiber genes involved in PCW synthesis and turgor-driven cell expansion are differentially expressed in a manner that parallels the growth rate. Characterization of the cotton fiber transcriptome has immediate applications in agricultural biotechnology and molecular breeding programs geared toward the genetic improvement of yield and fiber quality.
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  • 54
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    Physiologia plantarum 124 (2005), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Methyl salicylate (MeSA) is thought to have a major role in biotic and abiotic stresses by acting as a signal to trigger the oxidative burst, which is needed to activate gene expression in plant stress responses. To assess the potential effects of sustained foliar accumulation of MeSA on plant stress tolerance, the extent of photo- and antioxidant protection, lipid peroxidation and visual leaf area damage were evaluated in MeSA-treated (c. 60 nl l−1 in air) and control holm oak (Quercus ilex L.) plants exposed to heat stress. Control plants showed an increase in foliar MeSA levels up to 1.8 nmol [gDW]−1 as temperature increased and they displayed tolerance to temperatures as high as 45°C, which might be attributed, at least in part, to enhanced xanthophyll de-epoxidation and increases in ascorbate and α-tocopherol. MeSA-treated plants showed a sustained foliar accumulation of this compound, with values ranging from 10 to 23 nmol [gDW]−1 throughout the experiment. These plants showed lower ascorbate and tocopherol levels and higher oxidative damage at 50°C than controls, as indicated by enhanced malondialdehyde levels and leaf area damage and lower maximum efficiency of PSII photochemistry (Fv/Fm ratio). These results demonstrate that a sustained foliar accumulation of MeSA is detrimental to plant function and that it can reduce thermotolerance in holm oak by altering antioxidant defences.
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  • 55
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    Physiologia plantarum 124 (2005), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The virescent character is a genetic variant in pigmentation characterized by a delay in greening. Seedlings of the virescent mutants v1, v2, v3, v4, v13, v16, v18, v19 and v26 of maize exhibit chlorosis when grown at low temperature. Chlorotic leaves contain plastids that appear to have been arrested at an early stage of development. The results indicated that V16, V2, V3 and V4 loci control early stages of chloroplast development while V1, V13 and V19 may play a role at the end of development. The mutations in the V18 and V26 loci may control an intermediate step. At the pigment level, the virescent mutants of maize differ widely from analogous mutations existing in other plants. The mutations were characterized by a reduced amount of chlorophyll a and b (up to 100 times in v16) and chlorophyll a/b ratio above normal (up to 13.7 in v16). Lutein content was reduced in all mutants (less than 3% in v16 compared to wild type) but v13, while pigments of the xanthophyll cycle were found at higher levels in v1 and v13 (more than 10 and 90%, respectively). The v2, v3, v4, v16 and v18 mutants that are most depleted in β-carotene (36 times less in average than wild type) are also deprived in D1 and D2 polypeptides. Moreover, the v2, v3, v4, v16 and v18 mutants characterized by a lower accumulation in lutein are most depleted of light-harvesting complex II. All mutants possess a functioning, fully reversible, non-photochemical quenching mechanism. This is most developed in the v13 and v19 mutants (φn = 0.48 and 0.44, respectively). These two mutants also have a relatively high primary photochemical yield for photosystem II and a functioning photosystem I (φp = 0.23 and 0.39, respectively). The most interesting mutant is v13 that shows severe chlorosis and possesses the most effective non-photochemical quenching mechanism(s), which is thought to provide protection against excess photon absorption by photosystem II.
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  • 56
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A UV-B exclusion-experiment was conducted in the high Arctic Zackenberg, NE Greenland, in which Salix arctica leaves during most of the growing season were fixed perpendicular to the solar zenith angle, thereby receiving maximal solar radiation. Covered with Teflon and Mylar foil, the leaves received approximately 90 and 40% of the ambient UV-B irradiance, respectively. The effects were examined through recordings of chlorophyll a fluorescence transients, determination of biomass and analysis of total carbon and nitrogen content and amount of soluble flavonoids in the leaves. The processing of light was analysed by means of the chlorophyll a fluorescence transient, using the so-called JIP test, as evolved by Reto J. Strasser and his coworkers. Reduction of the UV-B irradiance caused a rise in many of the fluorescence parameters during July, but not in August (late season). Thus increases in the efficiency that an absorbed photon will be trapped by the PSII reaction centre with the resultant reduction of QA to QA– (ET0/ABS = FV/FM) and the efficiency that an electron residing on QA– will enter the intersystem electron transport chain (ET0/TR0) were observed in reduced UV-B. Moreover, estimated per cross-section of leaf sample, the number of active PSII reaction centres (RC/CSM) and electron transport rate (ETM/CSM) and all performance indexes (PIABS, PICSo and PICSm) were increased in reduced UV-B. The total soluble flavonoid content was highest in ambient UV-B. The treatment effects on fluorescence parameters that were directly measured (e.g. F0 and FM) and those that were derived (e.g. quantum efficiencies, parameters per PSII reaction centres and per cross-section of leaf sample) are discussed in relation to one another, in relation to daily and seasonal variation, and from the perspective of evaluating the relative importance of UV-B of donor and acceptor side capacity in Photosystem II. In conclusion, the experimental set-up and non-invasive measurements proved to be a sensitive method to screen for effects of UV-B stress.
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  • 57
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The basidiomycete Piriformospora indica interacts with Arabidopsis roots and mimics an arbuscular mycorrhiza. A MATH [meprin and TRAF (tumour necrosis factor receptor-associated factor) homology] domain-containing (MATH) protein at the plasma membrane of Arabidopsis roots is one of the first components to respond to the presence of this fungus. MATH proteins are involved in nodule formation in Medicago and protein degradation in the Arabidopsis cytosol. They exhibit sequence similarities to meprins, extracellular peptidases which cleave (signal) peptides, and to TRAFs, intracellular proteins which interact with receptor kinases at the plasma membrane. Fifty-nine genes for MATH proteins are present in the Arabidopsis genome. Members of this protein family are predicted to be found in the ER–plasma membrane–extracellular space continuum, in the nucleus–cytosol compartment and in organelles. In this article, we describe this novel class of plant genes. We also use MS-MS analyses to identify the subcellular localization of individual members of the MATH protein family in Arabidopsis thaliana.
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  • 58
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    Physiologia plantarum 124 (2005), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Maize (Zea mays L., line F2) plants were grown in the field under high or low fertilization input to monitor the metabolic, biochemical and molecular events occurring in young vegetative leaves and in the different leaf stages along the main axis in plants harvested 15 days after silking. This study shows that in maize which possess large sinks represented by the seeds, nitrogen (N) management is different compared with tobacco in which sink strength is much lower and mostly limited to young developing leaves. Although in young leaves nitrate assimilation predominates in both species, ammonium assimilation exhibits some species-specific differences with respect to inorganic and organic N metabolite accumulation during leaf ageing. These differences are likely to be related to the high sink strength of the ear in maize, which continuously imports carbon and N assimilates during grain filling. Consequently, a number of cytosolic glutamine synthetase isoenzymes are expressed during leaf ageing to maintain a constant flux of reduced N necessary for the synthesis of organic N molecules used either for leaf protein synthesis or directly translocated to the grain. This situation contrasts with that found in tobacco for which leaf ammonium assimilation in the plastids is shifted to the cytosol during the transition from sink leaves to source leaves. These species-specific differences for N assimilation and recycling are discussed in relation to the evolution of leaf photosynthetic activity and leaf senescence, which both seem to be largely dependent on the different sink strength in each species.
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  • 59
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    Physiologia plantarum 124 (2005), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Effect of low temperature on anthocyanin accumulation in seedlings of Alternanthera bettzickiana and activity changes of calmodulin (CaM) and Ca2+-ATPase under low temperature were studied. Results indicate that the increase of anthocyanin content was obviously paralleled not only by the activity of CaM but also by the activity of Ca2+-ATPase. In addition, seedlings were pretreated with CaM antagonist [chlorpromazine (CPZ)] before low-temperature treatment in order to further investigate whether CaM plays a role in anthocyanin accumulation. CPZ pretreatment inhibited the activity of CaM and Ca2+-ATPase and caused a reduction in anthocyanin levels. Hence, it is concluded that CaM and Ca2+-ATPase were directly correlated with anthocyanin accumulation under low temperature, Ca2 ± CaM may be involved in low-temperature signal transduction leading anthocyanin synthesis.
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  • 60
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    Physiologia plantarum 124 (2005), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Arabinogalactan-proteins (AGPs) are a class of large hydroxyproline-rich glycoproteins (HGRPs) found in almost all plant species, and have been implicated in various plant growth and developmental processes including xylogenesis. A total of six AGP-like genes or gene families have been cloned from differentiating pine xylem. In this study, seven different members of the ptaAGP5 gene family with between 54% and 73% similarity at the amino acid level were newly identified. Gene-specific primers were designed and relative transcript levels of 11 loblolly pine AGP and AGP-like genes were examined using real-time reverse transcription-polymerase chain reaction (RT-PCR) analysis. Expression was examined in different tissues: earlywood and latewood; xylem from two populations; drought-stressed and well-watered roots; compression, opposite and vertical wood; and in vitro cultured cells induced for lignification. The different loblolly pine AGP and AGP-like genes showed varying expression patterns under the different conditions, suggesting different functions for each loblolly pine AGP. The results from this study also suggest that some AGPs are associated with xylogenesis, but not with lignification, and that different xylem AGPs probably have different functions.
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  • 61
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The effects of soil drying on the activity of nitrate reductase (NR; EC 1.6.6.6) were studied in Helianthus annuus L. and non-nodulated Lupinus albus L. plants growing under two nutrient supply regimes. NR activity was assessed in leaf and root extracts by measuring the activity of the unphosphorylated active form (NRact), the maximal extractable activity (NRmax) and the activation state. To obtain an insight into potential signalling compounds, nitrate, free amino acids and soluble sugars were also quantified. In both species, foliar NRact and NRmax were negatively affected by soil drying and a decreased supply of nutrients, the observed changes in NR activity being linearly correlated with the depletion of nitrate. Similar results were obtained in the roots of sunflower. Conversely, in white lupin roots, NRmax was found to be independent of tissue nitrate concentration. Regardless of the species and organ, the activation state of the enzyme was unaffected by the nutrient supply regime. In well-watered sunflower roots, only about 50% of the existing NR was unphosphorylated, but the activation state increased significantly in response to drought. In contrast, lupin roots always exhibited NR activation state values close to 80%, or even higher. At the leaf level, the NR activation state was hardly changed in response to soil drying. The observed changes in the concentrations of soluble sugars and free amino acids are discussed in terms of their possible contribution to the variations in NR activity.
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  • 62
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    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The phototransformation of protochlorophyllide forms was studied in epicotyls of dark-germinated pea (Pisum sativum L. cv. Zsuzsi) seedlings. Middle segments were illuminated with white or 632.8 nm laser flash or continuous light at room temperature and at −15°C. At low light intensities, photoreduction could be distinguished from bleaching. 77 K fluorescence emission spectra were measured, difference spectra of illuminated and non-illuminated samples were calculated and/or the spectra were deconvoluted into Gaussian components. The 629 nm-emitting protochlorophyllide form, P629 (Pxxx where xxx is the fluorescence emission maximum), was inactive. For short-period (2–100 ms) and/or low-intensity (0.75–1.5 µmol m−2 s−1) illumination, particularly with laser light, the transformation of P636 into the 678 nm-emitting chlorophyllide form, C678 (Cxxx where xxx is the fluorescence emission maximum), was characteristic. This process was also found when the samples were cooled to −15°C. The transformation of P644 into C684 usually proceeded in parallel with the process above as a result of the strong overlap of the excitation bands of P636 and P644. The Shibata shift of C684 into a short-wavelength form, C675–676, was observed. Long-period (20–600 s) and/or high-intensity (above 10 µmol m−2 s−1) illumination resulted in the parallel transformation of P655 into C692. These results demonstrate that three flash-photoactive protochlorophyllide forms function in pea epicotyls. As a part of P636 is flash photoactive, its protochlorophyllide molecule must be bound to the active site of a monomer protein unit [Böddi B, Kis-Petik K, Kaposi AD, Fidy J, Sundqvist C (1998) The two short wavelength protochlorophyllide forms in pea epicotyls are both monomeric. Biochim Biophys Acta 1365: 531–540] of the NADPH:protochlorophyllide oxidoreductase (EC 1.3.1.33). Dynamic interconversions of the protochlorophyllide forms into each other, and their regeneration, were also found, which are summarized in a scheme.
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  • 63
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    Physiologia plantarum 124 (2005), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Expression of selected genes in relation to phosphate (Pi) starvation and sugar sensing was studied in leaves of Arabidopsis. Excised leaf segments with different P status were supplied with combinations of Pi and sugars. Sugar-inducible genes, encoding β-amylase (β-AMY) and chalcone synthase (CHS), were also induced by P deficiency, and were more strongly regulated by sugars when leaf segments originated from P-starved plants. Furthermore, transcript levels of the P-starvation-inducible genes ACP5 (encoding an acid phosphatase), RNS1 (encoding a ribonuclease), and IPS1 (unknown function) increased in response to exogenously applied sugars. Supply of Pi to the leaf segments reversed both P-starvation-induced and sugar-induced gene expression. These interactions reveal a close relationship between P and sugar sensing. To differentiate between hexokinase-dependent and hexokinase-independent sugar sensing the effect of the glucose analogue 2-deoxyglucose and gene expression in the hexokinase-1 deficient mutant, gin2-1, were studied. Both β-AMY and CHS were induced by supplying sucrose to excised leaves but not by 2-deoxyglucose, confirming that these genes are regulated by hexokinase-independent sugar sensing. In the gin2-1 mutant both β-AMY and CHS responded clearly to P starvation excluding that hexokinase-1 mediates the response to P. Similarly, the P-responding genes, IPS1 and RNS1 were repressed by addition of Pi also in the gin2-1 mutant. In conclusion, several phosphate starvation-induced genes are also sugar-induced and hexokinase-independent sugar sensing in Arabidopsis is strongly intensified by phosphate starvation.
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  • 64
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    Physiologia plantarum 124 (2005), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: S-Adenosylmethionine decarboxylase (SAMDC, E.C. 4.1.4.50) is a key enzyme involved in the polyamine (PA) biosynthetic pathway. An understanding of how SAMDC genes are regulated is important for elucidating the molecular basis of PA biosynthesis and the role of PAs in plant growth and development. However, information regarding transcriptional regulation of SAMDC has been limited. In an attempt to address this question, we isolated four cDNAs from mustard (Brassica juncea), designated BJSAMDC1, BJSAMDC2, BJSAMDC3 and BJSAMDC4, encoding predicted SAMDC. A comparison of deduced amino acid sequence revealed that they are highly homologous to other plant SAMDCs. These proenzymes also possess the conserved cleavage domain and putative PEST sequence for SAMDC. Northern analysis showed that the SAMDC transcripts were most abundant in reproductive organs and roots but that the level was low in young leaves and petioles. Meanwhile, SAMDC expression in the leaf was up-regulated differentially in response to stress such as chilling and exogenous ACC. The effect of exogenous PAs on SAMDC expression appears to be divergent. While putrescine up-regulated the expression of BJSAMDC1, spermidine and spermine down-regulated its expression. Furthermore, mannitol was also shown to up-regulate SAMDC expression in a gene-specific manner, in which the BJSAMDC1 transcript increases but other SAMDC transcripts are not affected.
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  • 65
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    Physiologia plantarum 123 (2005), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: FtsH is a membrane-bound ATP-dependent metalloprotease complex found in prokaryotes and organelles of eukaryotic cells. It consists of one or two trans-membrane helices at its amino-terminus, a highly conserved ATPase domain, which relates it to the AAA protein family, and a zinc-binding domain towards its carboxy-terminus that serves as the proteolytic site. Most bacteria contain a single FtsH gene, but the cyanobacterium Synechocystis has four. The Arabidopsis thaliana genome contains 12 genes encoding FtsH proteins, nine of them can be targeted to chloroplasts, whereas the other three are mitochondrial. Chloroplast FtsH protease is located in the thylakoid membrane, where it forms complexes, most likely hexamers, whose ATPase and proteolytic domains are exposed to the stroma. It is involved in the degradation of the D1 protein of photosystem II reaction centre during its repair from photoinhibition, as well as in the degradation of unassembled proteins in the thylakoid and the stroma. In Arabidopsis, FtsH2 is the most abundant isomer, followed by FtsH5, 8 and 1. This hierarchy is well reflected in the severity of the variegated phenotype of mutants in these genes.
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  • 66
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    Physiologia plantarum 123 (2005), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Lon-, Clp- and FtsH-like proteases, members of three families of ATP-dependent proteases derived from bacterial ancestors, have been identified in plant mitochondria. Classifications of mitochondrial-specific paralogues of plant ATP-dependent proteases, based on targeting prediction programs and different experimental methods, are compared. Accumulating evidence points to similarities in the structure and the mechanisms of action used by various ATP-dependent proteases. Therefore, before focusing on plant mitochondrial ATP-dependent proteases, the paper discusses general features of ATP-dependent proteases. To date, information about structure and function of plant mitochondrial Lon-like, Clp-like and FtsH-like proteases is rather scarce, but indicates that these enzymes, like their bacterial and eukaryotic homologues, combine proteolytic and chaperone-like activities to form mitochondrial protein quantity and quality control system in plants.
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  • 67
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    Physiologia plantarum 123 (2005), S. 0 
    ISSN: 1399-3054
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    Topics: Biology
    Notes: Several studies have shown that protease inhibitors can suppress programmed cell death in various plant species and plant tissues. This is especially true of caspase inhibitors that can block programmed cell death and its marker DNA laddering. There are up to six different caspase-like activities that can be measured in plant extracts, the most prominent being caspase1-like and caspase3-like. These activities can be located in vacuoles and also in the nucleus or the cytoplasm. This represents a striking apparent similarity with animal programmed cell death. Because there are no caspase orthologue in plant genomes, a major challenge is to identify these proteases. Recently two proteases with caspase-like activities have been recognized as belonging to two different protease families that are not closely related to animal caspases. Various other protease families have been implicated and this suggests that complex protease networks have been recruited for the plant cell demise.
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  • 68
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    Topics: Biology
    Notes: Soil salinity is a major factor affecting crop productivity worldwide. This study explores mechanisms that contribute to salt tolerance in rice (Oryza sativa L.). Hydroponically grown, 2-week-old salt tolerant and sensitive indica rice varieties, Pokkali and Jaya, respectively, were exposed to a 48-h stress period with NaCl (0–250 mM). When exposed to 200 mM NaCl, micromolar levels of external Ca2+ elevated survival of both varieties. The Ca2+ levels required were lower for Pokkali than for Jaya, but resulted in significantly higher survival. Estimates of Na+ and K+ in root and shoot compartments were made by flame photometry, while X-ray microanalysis was used to localize Na+ in the extracellular matrix of the shoot. Transpirational bypass flow was estimated using the apoplastic tracer, 8-hydroxypyrene-1,3,6-trisulphonic acid, trisodium salt. Our data demonstrate a Ca2+-dependent reduction in Na+ transport to shoots, which correlated with a decline in bypass flow and of Na+ in the transpirational stream. In addition, the Na+ that enters the shoot is partitioned among several distinct compartments. Survival is inversely correlated with Na+ levels in the shoot apoplastic fluid, which surrounds the cell and influences cytosolic composition. Pokkali maintained lower Na+ in its apoplast compared with the salt sensitive Jaya at the same total shoot Na+. Na+ in the apoplast appears to be regulated by sequestration into intracellular compartments. This sink supplements the primary response of reducing Na+ influx into the shoot and effectively buffers the apoplastic fluid in Pokkali. All of these mechanisms are operational in Jaya as well but are deployed less effectively.
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  • 69
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    Physiologia plantarum 125 (2005), S. 0 
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    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: An experiment was performed to elucidate interspecific differences in survival time of grass species subjected to an extreme climatic event. We exposed eight grass species to a simulated heat wave in the field (‘free air’ temperature increase at 11°C above ambient) combined with drought. We determined whether interspecific differences in survival time were related to the responses of the species to the imposed stress or could be explained by their ecophysiological or morphological characteristics in unstressed conditions. Surprisingly, there was no effect of specific leaf area, but species with a higher total leaf area survived longer. This may arise from a greater water reserve in the plant as a whole, which could delay the desiccation of the meristem, or from reduced evaporation due to a higher leaf area index. Species in which the decrease in light-saturated stomatal conductance (gs) and photosynthetic CO2 uptake rate (Amax) was strongly related to the decrease in soil water availability (measured as soil relative water content and stress duration) survived longer than species in which gs and Amax likewise declined but responded more to daily fluctuations in irradiance, temperature, and vapor pressure deficit during the heat wave. We, therefore, hypothesize that interspecific differences in stress survival time might be related to the extent to which stomata react to changes in soil water conditions relatively to changes in other environmental and physiological factors. The results suggest that resistance to extremes is governed by other mechanisms than resistance to moderate drought.
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  • 70
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    Physiologia plantarum 124 (2005), S. 0 
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    Topics: Biology
    Notes: Rice (Oryza sativa L.) seeds were soaked for 18 h in distilled water in the absence (–PBZ) or presence (+PBZ, a triazole) of 100 mg l−1 paclobutrazol and then air dried. These air-dried seeds were germinated in the dark and then cultivated in a Phytotron. Twelve-day-old –PBZ and +PBZ seedlings were treated or not with CdCl2. Cd toxicity was judged by the decrease in biomass production, decrease in chlorophyll and protein content, increase in NH4+ content and induction of oxidative stress. The results indicated that PBZ applied to seeds was able to protect rice seedlings from Cd toxicity. On treatment with CdCl2, the abscisic acid (ABA) content increased in +PBZ leaves, but not in –PBZ leaves. The decrease in the transpiration rate of –PBZ seedlings by CdCl2 was less than that of +PBZ seedlings. Exogenous application of the ABA biosynthesis inhibitor, fluridone (Flu), reduced ABA accumulation, increased the transpiration rate and Cd content, and decreased the Cd tolerance of +PBZ seedlings. The effects of Flu on the Cd toxicity, transpiration rate and Cd content were reversed by the application of ABA. It seems that the PBZ-induced Cd tolerance of rice seedlings is mediated through an accumulation of ABA.
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  • 71
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    Physiologia plantarum 125 (2005), S. 0 
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    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A comparison was performed of the tetrapyrrole transformations that occur upon irradiation of epicotyl or leaves of dark-grown Pisum sativum L. (var. Zsuzsi, Hungary). High performance liquid chromatography analysis after continuous or flash-irradiation showed that the biosynthetic pathway from protochlorophyllide (Pchlide) to chlorophyll (Chl) a was markedly slowed down at the step of the reduction of geranylgeranyl(gg)-Chl to dihydrogeranylgeranyl (dhgg)-Chl in epicotyls, whereas phytyl-Chl was synthesized in leaves subjected to the same light treatments. Quantitative pigment analysis during continuous irradiations of different intensities also showed that significant Pchlide photodestruction occurred in epicotyls even under weak light. When both Pchlide and chlorophyllide and/or chlorophylls were present in epicotyls, Pchlide photodestruction was faster under 630-nm light than under 670-nm light, which indicates that this process is most efficiently promoted by Pchlide excitation. Pre-incubation of epicotyl segments with 10 mM ascorbate partly alleviated pigment photodestruction in white light. It is concluded that formation of photoactive Pchlide–Pchlide oxidoreductase complexes is important to prevent fast pigment photooxidation after Pchlide accumulation in the dark.
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    Physiologia plantarum 124 (2005), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Ethylene is produced by plants in response to a wide variety of environmental signals and mediates several developmental processes in higher plants. We investigated whether ethylene has a regulatory function in nodulation in the actinorhizal symbiosis between Discaria trinervis and Frankia BCU110501. Roots of axenic D. trinervis seedlings showed aberrant growth and reduced elongation rate in the presence of ethylene donors [i.e. 2-aminocyclopropane carboxylic acid (ACC) and 2-chloroethylphosphonic acid (CEPA)] in growth pouches. By contrast, inhibitors of ethylene synthesis (aminoethoxyvinylglycine, AVG) or perception (Ag+) did not modify root growth. This indicates that the development of D. trinervis roots is sensitive to elevated ethylene levels in the absence of symbiotic Frankia. The drastic response to higher ethylene levels did not result in a systemic impairment of root nodule development. Nodulation occurred in seedlings inoculated with Frankia BCU110501 in the presence of ethylene donors or inhibitors. Overall, the ability of the seedlings to shut down nodule formation in the younger portions of the root (i.e. to autoregulate nodulation) was not significantly impaired by a modification of endogenous ethylene levels. In contrast, we detected subtle changes in the nodulation pattern of the taproots. As a result of exposing the roots to CEPA, less nodules developed in older portions of the taproot. In line with this observation, AVG or Ag+ caused the opposite effect, i.e. a slight increase in nodulation of the mature regions of the taproot. These results suggest that ethylene is involved in modulating the susceptibility for nodulation of the basal portion of D. trinervis seedling roots.
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    Physiologia plantarum 125 (2005), S. 0 
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    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Feedback de-excitation (FDE) is a process that protects photosystem II from damage during short periods of overexcitation. Arabidopsis thaliana mutants lacking this mechanism have reduced fitness in environments with variable light intensities. We have assayed the physiological consequences of mutations resulting in the lack of FDE and analysed the differences between field-grown plants and plants grown under fluctuating light in the laboratory. We show that FDE is an important mechanism in short-term responses to fluctuating light. Anthocyanin and carbohydrate levels indicated that the mutant plants were stressed to a higher degree than wild-type (WT) plants. Field-grown mutants were photo-inactivated to a greater degree than WT, whereas mutant plants in the fluctuating light environment in the laboratory seemed to downregulate the photosynthetic quantum yield, thereby avoiding photo-damage but resulting in impaired growth in the case of one mutant. Finally, we provide evidence that FDE is most important under conditions when photosynthesis limits plant growth, for example during flower and seed development.
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  • 74
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    Physiologia plantarum 125 (2005), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In plant tissue, a wound signal is produced at the site of injury and propagates or migrates into adjacent tissue where it induces increased phenylalanine ammonia lyase (PAL, EC 4.3.1.5) activity and phenylpropanoid metabolism. We used excised mid-rib leaf tissue from Romaine lettuce (Lactuca sativa L., Longifolia) as a model system to examine the involvement of components of the phospholipid-signaling pathway in wound-induced phenolic metabolism. Exposure to 1-butanol vapors or solutions inhibited wound-induced increase in PAL activity and phenolic metabolism. Phospholipases D (EC 3.1.4.4), an enzyme involved in the phospholipid-signaling pathway is specifically inhibited by 1-butanol. Re-wounding tissue, in which an effective 1-butanol concentration had declined below active levels by evaporation, did not elicit the normal wound response. It appears the 1-butanol-treated tissue developed resistance to wound-induced increases in phenylpropanoid metabolism that persisted even when active levels of 1-butanol were no longer present. However, a metabolic product of 1-butanol, rather than 1-butanol itself, may be the active compound eliciting persistence resistance. Inhibiting a subsequent enzyme in the phospholipid-signaling pathway, lipoxygenase (LOX; EC 1.13.11.12) with 1-phenyl-3-pyrazolidinone (1P3P) or reducing the product of LOX activity with diethyldithio-carbamic acid (DIECA) also inhibited wound-induced PAL activity and phenolic accumulation. The effectiveness of 1-butanol, DIECA, and 1P3P declined as the beginning of the 1-h immersion period was delayed from 0 to 4 h after excision. This decline in effectiveness is consistent with involvement of the inhibitors in the production or propagation of a wound signal. The wound signal in lettuce moves into adjacent tissue at 0.5 cm h−1, so delaying application would allow the signal to move into and induce the wound response in adjacent tissue before the delayed application inhibited synthesis of the signal. Salicylic acid (SA) inhibits allene oxide synthase (AOS, EC 4.2.1.92), another enzyme in the phospholipid-signaling pathway. Exposure to 1 or 10 mM SA for 60 min reduced wound-induced phenolic accumulation by 26 or 56%, respectively. However, 1 mM SA lost its effectiveness if applied 3 h after excision, while 10 mM SA remained effective even when applied 4 h after excision. At 1 mM, SA may be perturbing the wound signal through inhibition of AOS, while at 10 mM it appears to have some generally inhibitory effect on subsequent phenolic metabolism. These data further implicate the phospholipid-signaling pathway in the generation of a wound signal that induces phenolic metabolism in wounded leaf tissue.
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  • 75
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    Topics: Biology
    Notes: Many higher plants accumulate free proline (Pro) to counteract osmotic stress. To examine the role of free Pro in salt resistance, we suppressed the tobacco Pro dehydrogenase (NtProDH) gene using a double-stranded RNA interference technique in tobacco Bright Yellow 2 cells. Northern blot analysis showed reduced levels of the NtProDH transcripts in the transgenic line. The free Pro level in transgenic cells was about 1.2- to 3.0-fold, and the Pro dehydrogenase activity was about 4.9–32.2% of those in wild-type (WT) cells. The transgenic cells had an appearance markedly different from that of WT cells. Microscopic analysis revealed that the transgenic tobacco cells were mostly barrel shaped as in a filament, cylindrical and small. In synchronous cultures, transgenic cells showed more active cell division than WT cells. Hypersensitivity to exogenous Pro increased in the transgenic tobacco cells. The transgenic cells showed an increased osmotolerance, perhaps by free Pro accumulation.
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  • 76
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    Topics: Biology
    Notes: This study examined tobacco (Nicotiana tabacum cv. Petit Havana SR1) leaf respiration in the dark, utilizing both wild-type plants and transgenic plants with increased or decreased levels of alternative oxidase (AOX) protein. AOX represents a non-energy-conserving branch in mitochondrial electron transport. Inhibitor studies showed that the maximum possible flux of electrons to AOX (AOX capacity) correlated with the level of AOX protein present in the different plant lines. A comparison of the plants using online 18O isotope discrimination was done to determine whether AOX protein level would impact the actual steady-state partitioning of electrons to AOX (AOX engagement). Under a range of pretreatment and measurement conditions, there was little if any effect of AOX protein level on the degree of engagement. This suggests that the metabolic conditions inherent to a particular growth condition and/or the biochemical regulatory properties of AOX itself are the critical factors that control partitioning. Interestingly, we found that measurement temperature and water status are parameters that may have some influence over AOX engagement.
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  • 77
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    Topics: Biology
    Notes: A (1→3),(1→4)-β-glucan synthase catalysing the synthesis of (1→3),(1→4)-β-glucan (mixed-linkage glucan) was investigated using microsomal membranes prepared from developing barley (Hordeum vulgare L. cv. Shikokuhadaka 97) endosperms harvested 21 days after flowering. The microsomal fraction produced (1→3),(1→4)-β-glucan by incorporation of [14C]Glc from UDP-[14C]Glc. The production of (1→3),(1→4)-β-glucan was ascertained by specific enzymatic digestion with endo-(1→3),(1→4)-β-glucanase (lichenase; EC 3.2.1.73) from Bacillus amyloliquefaciens, which released a radiolabelled trisaccharide (3-O-β-cellobiosyl-glucose) and a tetrasaccharide (3-O-β-cellotriosyl-glucose), the diagnostic oligosaccharides for the identification of (1→3),(1→4)-β-glucan. Digestion of the products with exo-(1→3)-β-glucanase (EC 3.2.1.58) from Basidiomycete QM806 released radiolabelled Glc, indicating that not only (1→3),(1→4)-β-glucans but also (1→3)-β-glucans (callose) had been formed due to the presence of (1→3)-β-glucan (callose) synthase (EC 2.4.1.34) in the microsomal fraction. The activity of (1→3),(1→4)-β-glucan synthase was maximal at pH 9.0 and at 25°C and in the presence of at least 2 mM Mg2+. The apparent Km and Vmax values for UDP-Glc were 0.33 mM and 480 pmol min−1 mg protein−1, respectively. Investigating the dependence of enzyme activity on developmental stage (7–35 days after flowering) of the endosperms, we found an increase of activity during the initial development reaching a maximum at 19 days, followed by a gradual decrease as the endosperms matured. The amount of (1→3),(1→4)-β-glucan in the cell walls of the endosperms, however, increased gradually towards maturation, even after 19 days. Analysing the relationship between enzyme activity and (1→3),(1→4)-β-glucan deposition in cell walls of endosperms prepared from 12 different barley varieties harvested 11–22 days after flowering showed that some varieties had both low activity and low glucan content, and in some both were high. But for several other varieties, the availability of donor substrate and other factors seem to influence the production of (1→3),(1→4)-β-glucan as well.
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    Topics: Biology
    Notes: Red clover, Trifolium pratense L., is the dominant forage legume in Sweden and is usually harvested twice per year, once in June and once in August. Two 15N-based methods –15N isotopic dilution (ID) and 15N natural abundance (NA) – were used to study N2 fixation from spring until first harvest in late June, from first to second harvest in late August, and from second harvest until first frost in autumn in Umeå, Sweden. The material studied comprized three neighbouring fields carrying a first year ley, a second year ley and a third year ley. For the 15N ID method, small amounts of highly enriched 15N-nitrate were added to experimental plots. The non-legumes in the plots, essentially Phleum pratense L. together with Festuca pratensis L., served as reference plants for both the ID and 15N NA measurements. Dry matter, N and 15N were separately analysed in leaves (laminae), stems (including petioles), stubble and roots. The proportion of N derived from air (pNdfa) was then calculated for each plant part and for whole plants. Estimates of the proportion of N derived from N2 fixation (pNdfa) were always very high, usually ≥0.8. Generally, estimates of pNdfa obtained by the ID and NA methods were similar, but the ID method gave higher estimates of pNdfa than the NA method when the highest N2 fixation levels were recorded, at the August harvest. Regression analyses suggest that estimates of pNdfa in leaves could provide useful indications of pNdfa in shoots and whole T. pratense plants, thus avoiding the need for time-consuming root analyses.
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    Topics: Biology
    Notes: Trehalose exists in most living organisms and functions as a storage carbohydrate and as an osmoprotectant in yeast, fungi, and bacteria. Trace amount of endogenous trehalose was detected in flowering plants, and the trehalose biosynthetic pathway was essential for embryo maturation in Arabidopsis. Conversely, exogenous trehalose was toxic to higher plants and severely curtailed root and shoot growth. In the current study, 30 mM trehalose was added to 2-week-old liquid cultures containing Arabidopsis thaliana (Columbia ecotype) seedlings. Densely stained granular particles were detected in the extracellular space of cotyledons and roots of trehalose-treated seedlings using transmission electron microscopy. Expression levels of 91 transcripts were altered by 1–6 h of trehalose treatment using DNA microarray analysis, and 65 of these encoded either known proteins or putative proteins with known functions. The exogenous trehalose treatment altered transcript levels of transcription factors, cell wall modification, nitrogen metabolism, and stress-related, defense-related, and fatty acid biosynthesis genes. Many of the transcripts altered by exogenous trehalose treatment were associated with the ethylene and methyl jasmonate-signaling pathways. The above findings suggested that trehalose, or metabolites derived from trehalose, are important regulators of plant gene expression in higher plants.
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    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Elevated atmospheric CO2 concentration [CO2] and different levels of nitrogen (N) nutrition can influence the amount of excess excitation energy in photosystem (PS) II and related photosynthetic properties. The interactive effect of two [CO2] levels (ambient: 360 µM M−1 and elevated: 720 µM M−1) and two N levels (high: 700 mg N plant−1 and low: 100 mg N plant−1) on these properties was examined in seedlings of Japanese white birch (Betula platyphylla var. japonica) using simultaneous measurements of gas exchange and chlorophyll fluorescence. Photosynthetic acclimation to elevated [CO2], as indicated by a decline in carboxylation efficiency (CE), was observed in plants grown at elevated [CO2] especially under low N. Elevated [CO2] resulted in a decrease in area-based leaf N content (Narea) irrespective of N treatment. The adverse effect of elevated [CO2] and low N on CE may have been exacerbated by a greater accumulation of leaf sugar and starch contents in these plants leading to a lower electron transport rate (ETR). While these plants also showed higher non-photochemical quenching (NqP) that could offset the reduction in energy dissipation through ETR to some extent, they still have a higher risk of photoinhibition from excessive excitation energy in PSII as indicated by a decrease in photochemical quenching (qP). However, chronic photoinhibition was not observed in plant grown at elevated [CO2] and low N because they showed no difference in Fv/Fm (the maximum photochemical efficiency of PSII) from those grown at ambient [CO2] and low N after an overnight dark adaptation. High levels of NqP in plants grown at elevated [CO2] and low N reflect a near saturation of thermal energy dissipation. This impaired capacity of photoprotection would render these plants more vulnerable to photoinhibition in the event of additional environmental stresses such as drought, low or high temperature.
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  • 81
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    Physiologia plantarum 125 (2005), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Carbon isotope ratio of leaf dry matter, δ13C, was measured on species occurring within Baiyin desert community, consisting of valley, slope and ridge microhabitats, and within Shandan desert community, consisting of Gobi desert and seasonal flooded creek microhabitats, in Northwest China. δ13C of C3 species increased with a decrease in soil water availability, suggesting that water-use efficiency (WUE) increased with decreasing soil moisture, whereas for all C4 species, δ13C tended to decrease with decreasing soil water availability, suggesting that WUE also increased with decreasing soil moisture. Above results indicated that water-use pattern was conservative under drought for C4 and C3 plants. In this present study, C4 species' occurrences within different microhabitats were investigated and C4 plants were observed to be absent and/or scarce within relatively lower soil moisture microhabitats, whereas they occurred and/or even had a high abundance within relatively higher soil moisture microhabitats, suggesting limited moisture available was a key factor of limiting C4 distribution in arid region of Northwest China.
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  • 82
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    Physiologia plantarum 125 (2005), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The expression and activity of type 1 NAD(P)H dehydrogenase (NDH-1) were investigated in Synechocystis PCC 6803 cells during different growth phases (i.e. lag, logarithmic, stationary and decline phases). The relative amount of NDH-1, estimated by Western blot analysis using antibodies against NdhH, NdhI and NdhK, increased more than two-fold during growth from the lag to the logarithmic phase and then decreased after the logarithmic phase to reach lowest levels after 15 days (decline phase). The activity of light-dependent NADPH oxidation and cyclic electron flow around photosystem I (PSI) changed nearly in parallel with the amount of NdhH, NdhI and NdhK in cells across the growth phases. In contrast, the activity of photosynthetic O2 evolution and respiratory O2 uptake was not significantly different across phases of growth; the fluctuation of the activity at different phases was within 40%. These results suggested that the activity of light-dependent NADPH oxidation and PSI-cyclic electron flow are restricted by the amount of NDH-1 and that other factor(s) are limiting the rates of photosynthesis and respiration.
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  • 83
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    Physiologia plantarum 124 (2005), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Arabinogalactan proteins (AGPs) are abundant plant cell-surface proteoglycans widely distributed in plant species. Crossed electrophoresis patterns of AGPs isolated from cultured cells before and after protonemata development differed, indicating that AGPs are involved in protonemata differentiation and development. Moreover, the addition of β-glucosyl Yariv reagent (βglcY), which binds specifically to AGPs, inhibits protonemata differentiation in cells of the liverwort Marchantia polymorpha L. cultured in protonemata-inducing medium. Transmission electron microscopic examination revealed that βglcY caused conspicuous disorder at the cell surface and the accumulation of abnormal structures between the plasma membrane and the cell wall. These results suggest that AGPs/βglcY complexes caused disturbances at the cell surface and inhibited cell-wall synthesis required for protonemata differentiation. Our results indicate that AGPs play a significant role in cell-wall synthesis during the protonemata-differentiation process of M. polymorpha.
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  • 84
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    Physiologia plantarum 124 (2005), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: When grown at a low P supply, Hakea prostrata R.Br. (Proteaceae) develops dense clusters of determinate branch roots, termed ‘proteoid’ or ‘cluster’ roots and accumulates Mn in its leaves. The aim of this study was to vary the production of cluster roots and assess the relationship between Mn uptake and cluster-root mass. We collected native soil from a location inhabited by H. prostrata and amended this with ‘high’ and ‘low’ amounts of insoluble or soluble P. After 14 months, we measured the impact of the treatments on cluster-root development and the [P], [Mn], [Fe], [Zn] and [Cu] in young (expanding) and mature leaves. Dry mass and leaf area increased with increasing P availability in the soil, but growth decreased at the highest soluble [P], which caused symptoms of P toxicity. The [P] in young leaves (1.3–2.7 mg g−1 DM) exceeded that in older leaves (0.28–0.85 mg g−1 DM), except when plants were grown with soluble P (3.2–21 mg g−1 DM). Cluster-root formation was inhibited when leaf [P] increased; [P] in young leaves, rather than that in old leaves, appeared to be the factor that determined the proportion of the root mass invested in cluster roots. Old leaves of all treatments had [Mn] from 90 to 120 µg g−1 DM, except for plants grown at high levels of soluble P, when [Mn] decreased below 30 µg g−1 DM. The [Mn] and [Zn] in old leaves and the [Cu] in young leaves were positively correlated with the fraction of roots invested in cluster roots. These findings support our hypothesis that cluster roots play a significant role in micronutrient acquisition, and also provide an explanation for Mn accumulation in leaves of H. prostrata, and presumably Proteaceae in general.
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  • 85
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 3-Deoxyanthocyanins provide bright orange-red colours to flowers of some members of the Gesneriaceae, including sinningia (Sinningia cardinalis). We examined 3-deoxyanthocyanin biosynthesis in sinningia, in particular, the expression of key flavonoid biosynthetic genes and the activities of the encoded proteins. Two abundant 3-deoxyanthocyanins, luteolinidin 5-O-glucoside and apigeninidin 5-O-glucoside, three flavone glycosides, luteolin 7-O-glucoside, luteolin 7-O-glucuronide and apigenin 7-O-glucuronide, and the cinnamic acid verbascoside were identified in sinningia petal tissue. Small amounts of a 3-hydroxyanthocyanin were also detected in a limited region of the petal. cDNA clones for three flavonoid enzymes, flavanone 3-hydroxylase (F3H), dihydroflavonol 4-reductase/flavanone 4-reductase (DFR/FNR) and anthocyanidin synthase (ANS), were isolated from a sinningia cDNA library made from petal RNA and used to measure transcript abundance during petal development. Only very low levels of F3H transcript were detected, while DFR/FNR transcript was highly abundant. ANS transcript levels were intermediate between these two. The F3H cDNA was shown to encode a functional F3H protein by complementation of the phenotype of an Antirrhinum majus F3H mutant. The recombinant DFR/FNR had activity against both flavanone and dihydroflavonol substrates to a comparable extent. The results suggest a mechanism of 3-deoxyflavonoid biosynthesis in sinningia similar to that reported for Zea mays, in which lack of F3H activity allows action of the DFR/FNR on flavanone substrates and production of flavan-4-ols. These are then likely converted to 3-deoxyanthocyanins through the action of the ANS and subsequent glucosylation.
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  • 86
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    Physiologia plantarum 124 (2005), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The responses of photosynthetic gas exchange, chlorophyll fluorescence, activities of antioxidant enzymes and lipid membrane peroxidation of two contrasting Picea asperata Mast. populations to 30% of full sunlight (shade) and full sunlight (sun) were investigated under well-watered and drought conditions. Two contrasting populations were from the wet and dry climate regions in China, respectively. For both populations tested, drought resulted in lower needle relative water content (RWC), CO2 assimilation rate (A), stomatal conductance (gs) and effective PSII quantum yield (Y), and higher non-photochemical quenching (qN), superoxide dismutase (SOD), ascorbate peroxidase (APX) activities as well as malondialdehyde (MDA) levels and electrolyte leakage in sun plants, whereas these changes were not significant in shade plants. For the wet climate population, shade plants showed higher chlorophyll contents (Chla, Chlb and Chla + b) than sun plants under both well-watered and drought conditions. Our study results implied that shade, applied together with drought, ameliorated the detrimental effects of drought. On the other hand, compared with the wet climate population, the dry climate population was more tolerant to drought in the sun treatment, as indicated by less decreases in A and mass-based leaf nitrogen content (Nmass), more responsive stomata, greater capacity for non-radiative dissipation of excitation energy as heat (analysed by qN), and higher level of antioxidant enzyme activities as well as lower MDA content and electrolyte leakage. These results demonstrated that the different physiological strategies were employed by the P. asperata populations from contrasting climate regions when the plants were exposed to drought and shade.
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  • 87
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    Physiologia plantarum 123 (2005), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Strains of Arabidopsis thaliana that lack a DNA glycosylase to recognize and remove 7,8-dihydro-8-oxoguanine from their DNA are expected to be compromised in their ability to deal with this highly mutagenic base, which is formed in the presence of reactive oxygen species (ROS). We have identified two strains, one containing a Ds insertion in an exon of the gene that codes for oxoguanine glycosylase and one containing a T-DNA insertion in the gene that codes for formamidopyrimidine glycosylase (both EC 3.2.2.23), and have crossed them to produce the double mutant. The homozygous mutant strains showed no phenotypic difference from the wild type in growth, development or reproductive potential under either normal conditions or conditions known to induce the formation of ROS. The lack of phenotype may be ascribed to the redundant nature of the base excision repair pathway in Arabidopsis. Longer multigenerational studies may be needed to determine the quantitative selective advantage of individual DNA glycosylase genes.
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  • 88
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    Physiologia plantarum 123 (2005), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The combined effects of inorganic phosphate (Pi) insufficiency and CO2 enrichment on metabolite levels and carbon partitioning were studied using roots of 9-, 13- and 17-day-old barley seedlings (Hordeum vulgare L. cv. Brant). Plants were grown from seed in controlled environment chambers providing 36 ± 1 Pa (ambient) or 100 ± 2 Pa (elevated) CO2 and either 1.0 mM (Pi sufficient) or 0.05 mM (Pi insufficient) Pi. When values were combined for both Pi treatments, plants grown under enhanced CO2 showed increased root dry matter, adenylates (ATP + ADP), glutamine and non- structural carbohydrates other than starch. In contrast with shoots, enhanced CO2 partially reversed the inhibition of root dry matter formation imposed by Pi insufficiency. The Pi-insufficient treatment also increased sucrose, glucose and fructose levels in barley roots. The Pi and CO2 treatments were additive, so that the highest soluble carbohydrate levels were observed in roots of Pi-insufficient plants from the elevated CO2 treatment. Pi limitation decreased dry matter formation, acid-extractable Pi, nitrate, hexose-phosphates, glutamate, glutamine and acid invertase activity of barley roots in plants grown in both ambient and elevated CO2. Adenylate levels in roots were unaffected by the moderate Pi insufficiency described here. Thus, the reduced hexose-phosphate levels of Pi-insufficient roots were not likely to be the result of low adenylate concentrations. The above results suggest that the capacity of barley roots to utilize carbohydrates from the shoot is inadequate under both Pi-insufficient and CO2-enriched treatments. In addition, the Pi and CO2 treatments used here alter the nitrogen metabolism of barley roots. These findings further emphasize the importance of avoiding nutrient stress during CO2 enrichment experiments.
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    Physiologia plantarum 123 (2005), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The plant hormone auxin plays a crucial role in the upstream regulation of many processes, making the study of its action particularly interesting to understand plant development. In this review we will focus on the effects auxin exerts on cell cycle progression, more specifically, during the initiation of lateral roots. Auxin fulfils a dominant role in the initiation of a new lateral root primordium. How this occurs remains largely unknown. Here we try to integrate the classical auxin signalling mechanisms into recent findings on cell cycle regulation. How both signalling cascades are integrated appears to be complex and is far from understood. As a means to solve this problem we suggest the use of a lateral root-inducible system that allows investigation of the early signalling cascades initiated by auxin and leading to cell cycle activation.
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  • 90
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    Physiologia plantarum 123 (2005), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The sesquiterpenoid hormone abscisic acid (ABA) regulates many aspects of plant growth and development. It has been difficult, however, to understand how this hormone functions in a myriad of events. Genetic analysis, particularly in Arabidopsis, has identified genes that modulate ABA responsiveness, but a molecular framework has not been developed to explain how these genes direct ABA-mediated developmental events. Certainly, some of the diversity of processes influenced by ABA is a result of crosstalk with other signalling pathways. In other cases, the complex development of a multicellular organism with different cell types and growth conditions throughout its life cycle also increases the possible output signals of ABA action. In this article, we touch on some of these issues in the context of ABA signalling during embryogenesis. On a more speculative level, we propose that a developmental and molecular framework of ABA action in the embryo may be gained from two chemically related terpenoid signalling hormones in animals: juvenile hormone (JH) and retinoic acid (RA). Many of the developmental issues with regard to ABA action in plant embryos are mirrored in JH studies from invertebrates, and the molecular action of RA in vertebrates suggests that transcriptional regulation is a direct output of RA addition. Both of these systems may be useful in furthering our developmental and molecular understanding of ABA action in plants.
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  • 91
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    Physiologia plantarum 123 (2005), S. 0 
    ISSN: 1399-3054
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    Topics: Biology
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  • 92
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    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Since 1995 the role of fungal hypaphorine in plants has been widely investigated and its IAA-antagonist activity recognized. Evidence of competitive antagonism includes organ development, gene expression or molecule–molecule interaction levels. Based on present knowledge, three sites of hypaphorine/IAA competition and subsequent signalling pathways have been hypothesized: the extracellular signalling pathway, the intracellular signalling pathway, and the transmembrane signalling pathway. Hypaphorine with other active indole alkaloids should be regarded as a new class of IAA antagonist finely regulating specific steps of plant growth or development.
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  • 93
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    Physiologia plantarum 123 (2005), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The plant hormone auxin has long been known to play a crucial role in plant growth and development, but how it affects so many different processes has remained a mystery. Recent evidence from genetic and molecular studies has begun to reveal a possible mechanism for auxin action. In this article we will present an overview with specific emphasis on auxin's role in roots of Arabidopsis thaliana, focusing on cell division, elongation and differentiation.
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  • 94
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    Physiologia plantarum 123 (2005), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Drought stress is the major limitation to crop productivity. However, crops are genetically complex with many loci contributing quantitatively to a given physiological trait. Nonetheless, significant in-roads into the molecular mechanisms of drought-adaptive responses have been made from the use of Arabidopsis thaliana. In this special review, we will discuss results gleaned from reverse and forward genetic studies that revealed the involvement of both ABA-dependent and ABA-independent components. In particular, mutant analyses have highlighted the surprising prevalence of RNA metabolism in many key steps. We will also discuss our recent use of infrared thermography to visualize stomatal closure in response to dehydration as a means to identify novel regulatory genes. This has allowed us to recover mutations belonging to at least eight complementation groups. Analysis of six of these loci revealed that all of their corresponding mutations affect either abscisic acid (ABA) biosynthesis or perception. Hence, in contrast to molecular studies on gene networks which pointed to the clear existence of multiple ABA-independent pathways in the control of dehydration tolerance, our results reinforce ABA-based signalling pathways as the predominant factor in primary or rapid responses. Finally, we will provide some details learned from the molecular analysis of OPEN STOMATA1 (OST1), a gene that encodes an ABA-activated kinase issued from this targeted genetic approach.
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    Physiologia plantarum 123 (2005), S. 0 
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  • 96
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    Ecology of freshwater fish 14 (2005), S. 0 
    ISSN: 1600-0633
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract –  Predicting species distributions has important implications for the conservation and management of freshwater fishes, particularly in areas such as the Great Plains, USA where human impacts have resulted in extirpations and declines for numerous native species. There are a number of statistical approaches for constructing distributional models; the accuracy of each is likely dependent on the nature of the environmental gradients, species responses to those gradients and the spatial extent of the modelling. Thus, it is important to compare multiple approaches across species and habitats to identify the most effective modelling approach. Using geographical information system (GIS) derived characteristics of stream segments as predictors, we tested the model performance of three methodologies – linear discriminant function analysis, classification trees and artificial neural networks (ANN) – for predicting the occurrence of 38 fish species in a Great Plains river basin. Results showed that all approaches predicted species occurrences with relatively high success. ANN generally were the best models, in that they generated the most significant models (35 of 38 species) and most accurately predicted species presence for the greatest number of species (average correct classification = 81.1%). The importance of GIS variables for predicting stream fish occurrences varied among species and modelling techniques, but were generally strong predictors of species distributions, including the federally endangered Topeka shiner Notropis topeka. In summary, predictive models should be viewed as both competitive and complementary methodologies for establishing quantitative linkages between fish species and their environment. Our study demonstrates the potential utility of such an approach for guiding conservation efforts for stream fishes of the Great Plains, USA.
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  • 97
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    Ecology of freshwater fish 14 (2005), S. 0 
    ISSN: 1600-0633
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract –  We measured growth of pike larvae (Esox lucius) fed with freshwater and brackish-water zooplankton by monitoring larval wet weight during 18 days. The fish food was analysed for species composition, carbon, nitrogen and fatty acids. Further, we analysed fish larval faecal pellet production. Larval weight was significantly higher in fresh water than in brackish water with natural zooplankton as food. Growth, given as wet weight, showed a significant relationship with zooplankton (〉100 μm) food carbon and highly unsaturated fatty acids, 20:5ω3, 22:6ω3, ω6 fatty acids and the ω3/ω6 fatty acid ratio. Phytoplankton fatty acids (10–50 μm), such as polyunsaturated fatty acids, 20:5ω3, 22:6ω3 and the ω3 fatty acids also correlated strongly with the wet weight of pike larvae. We demonstrated that several factors impact on pike larval growth.
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    Ecology of freshwater fish 14 (2005), S. 0 
    ISSN: 1600-0633
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 99
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    Ecology of freshwater fish 14 (2005), S. 0 
    ISSN: 1600-0633
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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    Oxford, UK : Munksgaard International Publishers
    Ecology of freshwater fish 14 (2005), S. 0 
    ISSN: 1600-0633
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract –  Predation risk allocation hypothesis predicts that a prey's response to predator depends on prey's previous experience on predator. Here we tested whether the group of three perch respond differentially to pike, predator of perch, depending on the timing of high constant (HC) and high unpredictable (HU) risk periods within low constant risk periods in short-term (10 h) experiments, and whether the response is stronger during a HU risk period than during a HC risk period. Perch clearly erected the dorsal fin in response to predation risk treatments (pike odour only, odour and visible pike). Decrease in activity and increase in shoaling behaviour were observed mainly during high risk periods. However, the perch's responses to pike did not differ statistically between periods of various levels of predation risk or depending on the timing of high risk situations within constant low risk periods, and thus, suggesting that perch respond mainly to changes in the current predation risk.
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