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  • Springer  (137)
  • 2000-2004  (137)
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  • Springer  (137)
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  • 1
    Electronic Resource
    Electronic Resource
    Stabilization of smoothness priors time-varying autoregressive models (2000)
    Springer
    Circuits, systems and signal processing 19 (2000), S. 423-435 
    Details
    ISSN: 1531-5878
    Keywords: Time-varying autoregressive models ; stability ; smoothness priors ; Tihkonov regularization ; constrained optimization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The stability of time-varying autoregressive (AR) models is an important issue in such applications as time-varying spectrum estimation and electroencephalography simulation and estimation. In some cases, such as time-varying spectrum estimation, the models that exhibit roots near unit moduli are difficult to use. Thus a tighter stability condition such as stability with a positive margin is needed. A time-varying AR model is stable with a positive margin if the moduli of the roots of the time-varying characteristic polynomial are somewhat less than unity for every time instant. Recently, a new method for the estimation of the time-varying AR models was introduced. This method is based on the interpretation of the underdetermined time-varying prediction equations as an ill-posed inverse problem that is solved by Tikhonov regularization. The method is referred to as the deterministic regression smoothness priors (DRSP) scheme. In this paper, a stabilization method in which the DRSP scheme is augmented with nonlinear stability constrainst is proposed. The problem is formulated so that stability with a positive margin can also be achieved. The problem is solved iteratively with an exterior point algorithm. The performance of the algorithm is studied with a simulation. It is shown that the proposed approach is well suited to stable modeling of signals containing narrowband transitions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01196156
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  • 2
    Electronic Resource
    Electronic Resource
    Stability of constant coefficient linear singular systems with delay (2000)
    Springer
    Circuits, systems and signal processing 19 (2000), S. 13-25 
    Details
    ISSN: 1531-5878
    Keywords: Singular systems ; delay ; consistency condition ; stability ; instability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract In this paper, the general class of singular systems with delay and linear constant coefficient singular systems with delay are discussed. First, several definitions of stability are presented for singular systems with delay, and general sufficient stability conditions and instability conditions are obtained. Second, stability and instability are analyzed for linear constant coefficient singular systems with delay.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01229989
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  • 3
    Electronic Resource
    Electronic Resource
    The Dynamics of a Fish Stock Exploited in Two Fishing Zones (2000)
    Springer
    Acta biotheoretica 48 (2000), S. 207-218 
    Details
    ISSN: 1572-8358
    Keywords: Dynamical population ; fishing efforts ; metapopulation ; time scales ; aggregation method ; equilibrium ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This work presents a specific stock-effort dynamical model. The stocks correspond to two populations of fish moving and growing between two fishery zones. They are harvested by two different fleets. The effort represents the number of fishing boats of the two fleets that operate in the two fishing zones. The bioeconomical model is a set of four ODE's governing the fishing efforts and the stocks in the two fishing areas. Furthermore, the migration of the fish between the two patches is assumed to be faster than the growth of the harvested stock. The displacement of the fleets is also faster than the variation in the number of fishing boats resulting from the investment of the fishing income. So, there are two time scales: a fast one corresponding to the migration between the two patches, and a slow time scale corresponding to growth. We use aggregation methods that allow us to reduce the dimension of the model and to obtain an aggregated model for the total fishing effort and fish stock of the two fishing zones. The mathematical analysis of the model is shown. Under some conditions, we obtain a stable equilibrium, which is a desired situation, as it leads to a sustainable harvesting equilibrium, keeping the stock at exploitable densities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010208910738
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  • 4
    Electronic Resource
    Electronic Resource
    Performance analysis of a slotted-ALOHA protocol on a capture channel with fading (2000)
    Springer
    Queueing systems 34 (2000), S. 1-35 
    Details
    ISSN: 1572-9443
    Keywords: multiple access ; CDMA ; rates of convergence ; stability ; functional limit theorems ; transient analysis ; Markov-modulated capture channel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract We consider the slotted ALOHA protocol on a channel with a capture effect. There are M 〈 ∞ users each with an infinite buffer. If in a slot, i packets are transmitted, then the probability of a successful reception of a packet is q i. This model contains the CDMA protocols as special cases. We obtain sufficient rate conditions, which are close to necessary for stability of the system, when the arrival streams are stationary ergodic. Under the same rate conditions, for general regenerative arrival streams, we obtain the rates of convergence to stationarity, finiteness of stationary moments and various functional limit theorems. Our arrival streams contain all the traffic models suggested in the recent literature, including the ones which display long range dependence. We also obtain bounds on the stationary moments of waiting times which can be tight under realistic conditions. Finally, we obtain several results on the transient performance of the system, e.g., first time to overflow and the limits of the overflow process. We also extend the above results to the case of a capture channel exhibiting Markov modulated fading. Most of our results and proofs will be shown to hold also for the slotted ALOHA protocol without capture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019192600091
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  • 5
    Electronic Resource
    Electronic Resource
    Normal Form Invariants Around Spin-orbit Periodic Orbits (2000)
    Springer
    Celestial mechanics and dynamical astronomy 78 (2000), S. 227-241 
    Details
    ISSN: 1572-9478
    Keywords: stability ; normal form ; spin-orbit resonance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We consider a model of spin-orbit interaction, describing the motion of an oblate satellite rotating about an internal spin-axis and orbiting about a central planet. The resulting second order differential equation depends upon the parameters provided by the equatorial oblateness of the satellite and its orbital eccentricity. Normal form transformations around the main spin-orbit resonances are carried out explicitly. As an outcome, one can compute some invariants; the fact that these quantities are not identically zero is a necessary condition to prove the existence of nearby periodic orbits (Birkhoff fixed point theorem). Moreover, the nonvanishing of the invariants provides also the stability of the spin-orbit resonances, since it guarantees the existence of invariant curves surrounding the periodic orbit.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011161605935
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  • 6
    Electronic Resource
    Electronic Resource
    A New ADI Scheme for Solving Three-Dimensional Parabolic Equations with First-Order Derivatives and Variable Coefficients (2000)
    Springer
    Journal of computational analysis and applications 2 (2000), S. 293-308 
    Details
    ISSN: 1572-9206
    Keywords: parabolic equations ; ADI scheme ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract An ADI scheme for solving three-dimensional parabolic equations withfirst-order derivatives and variable coefficients has been developed basedon our previous papers and the idea of the modified upwind differencescheme. This ADI scheme is second-order accurate and unconditionallystable. Further, a small parameter can be chosen which makes it suitablefor simulating fast-transient phenomena or for computations on fine spatialmeshes. The method is illustrated with numerical examples.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010108620966
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  • 7
    Electronic Resource
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    A Multiclass Feedback Queueing Network with a Regular Skorokhod Problem (2000)
    Springer
    Queueing systems 36 (2000), S. 327-349 
    Details
    ISSN: 1572-9443
    Keywords: multiclass networks ; networks with feedback ; Skorokhod Problem ; Skorokhod Mapping ; Lipschitz continuity ; stability ; load conditions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract We consider a four-class two-station network with feedback, with fluid inputs and a head-of-the-line generalized processor sharing discipline at each station. We derive the Skorokhod Problem associated with the network and obtain algebraic sufficient conditions for Lipschitz continuity of the associated Skorokhod Map. This provides the first example of a multiclass network with feedback for which the associated Skorokhod Problem has been proved to be regular. As an elementary application, we show that under the conditions which guarantee Lipschitz continuity the network is stable if and only if the usual load conditions apply.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011037419624
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  • 8
    Electronic Resource
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    Bifurcation Phenomena from Standing Pulse Solutions in Some Reaction-Diffusion Systems (2000)
    Springer
    Journal of dynamics and differential equations 12 (2000), S. 117-167 
    Details
    ISSN: 1572-9222
    Keywords: singular perturbation ; standing pulses ; stability ; Hopf bifurcation ; reaction-diffusion system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract Bifurcation phenomena from standing pulse solutions of the problem $$\varepsilon \tau u_t = \varepsilon ^2 u_{xx} + f(u,v),{\text{ }}v_t = v_{xx} + g(u,v)$$ is considered. ε(〉0) is a sufficiently small parameter and τ is a positive one. It is shown that there exist two types of destabilization of standing pulse solutions when τ decreases. One is the appearance of travelling pulse solutions via the static bifurcation and the other is that of in-phase breathers via the Hopf bifurcation. Furthermore which type of destabilization occurs first with decreasing τ is discussed for the piecewise linear nonlinearities f and g.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009098719440
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  • 9
    Electronic Resource
    Electronic Resource
    Activity and stability of Cu/ZnO/Al2O3 catalyst promoted with B2O3 for methanol synthesis (2000)
    Springer
    Catalysis letters 68 (2000), S. 55-58 
    Details
    ISSN: 1572-879X
    Keywords: promoting effect ; B2O3 ; Cu/ZnO/Al2O3 catalyst ; methanol synthesis ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The addition of B2O3 to a Cu/ZnO/Al2O3 catalyst increased the activity of the catalyst for methanol synthesis after an induction period during the reaction. The stability of the B2O3-containing Cu/ZnO/Al2O3 catalyst was greatly improved by the addition of a small amount of colloidal silica to the catalyst.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019010831562
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  • 10
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    Stability and excitation of potassium promoter in iron catalysts – the role of KFeO2 and KAlO2 phases (2000)
    Springer
    Catalysis letters 67 (2000), S. 129-134 
    Details
    ISSN: 1572-879X
    Keywords: potassium desorption ; stability ; excitation ; iron catalyst ; Rydberg atoms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Well‐characterized catalyst model compounds of KAlO2 and KFeO2 are investigated by thermal desorption of potassium from the material. The desorbing fluxes of ions, atoms and highly excited states (field ionizable Rydberg states) were studied with surface and field ionization detectors in a vacuum apparatus. From the Arrhenius plots the activation energies for desorption of K and K+ were determined. The chemical state of potassium at the surfaces is concluded to be: ionic on KAlO2 (with the K desorption barrier of 1.76 eV) and covalent on KFeO2 (barrier of 2.73 eV). These results agree with the data obtained earlier for industrial catalysts for ammonia and styrene production. They are interpreted in terms of the Schottky cycle, which is completed for KAlO2 and fails for KFeO2. This failure indicates a non‐equilibrium desorption process. K Rydberg states are only found to desorb from KFeO2, in agreement with the suggestion that such states in some way are responsible for the catalytic activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019013504729
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  • 11
    Electronic Resource
    Electronic Resource
    Stability of Linear Inequality Systems Measured by the Hausdorff Metric (2000)
    Springer
    Set-valued analysis 8 (2000), S. 253-266 
    Details
    ISSN: 1572-932X
    Keywords: Hausdorff metric ; linear inequality systems ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract In this paper, we propose a Hausdorff metric to measure the “distance” between two linear inequality systems on a real normed space X. For this topology, which comes through a pseudo-metric in the set Σ of linear inequality systems, the closedness of the feasible set mapping is studied, and at the same time a characterization of the stability of the subset Σ c of consistent sytems is given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008701026782
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  • 12
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    Stability Properties of a Bond Portfolio Management Problem (2000)
    Springer
    Annals of operations research 99 (2000), S. 251-265 
    Details
    ISSN: 1572-9338
    Keywords: stochastic programming ; bond portfolio management ; interest ratescenarios ; stability ; sensitivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Notes: Abstract The bond portfolio management problem is formulated as a multiperiod two-stage or multistage stochastic program based on interest rate scenarios. These scenarios depend on the available market data, on the applied estimation and sampling techniques, etc., and are used to evaluate coefficients of the resulting large scale mathematical program. The aim of the contribution is to analyze stability and sensitivity of this program on small changes of the coefficients – the (scenario dependent) values of future interest rates and prices. We shall prove that under sensible assumptions, the scenario subproblems are stable linear programs and that also the optimal first-stage decisions and the optimal value of the considered stochastic program possess acceptable continuity properties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019275817688
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  • 13
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    Destabilization for quasivariational inequalities of reaction-diffusion type (2000)
    Springer
    Applications of mathematics 45 (2000), S. 161-176 
    Details
    ISSN: 1572-9109
    Keywords: reaction-diffusion system ; unilateral conditions ; quasivariational inequality ; Leray-Schauder degree ; eigenvalue ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract We consider a reaction-diffusion system of the activator-inhibitor type with unilateral boundary conditions leading to a quasivariational inequality. We show that there exists a positive eigenvalue of the problem and we obtain an instability of the trivial solution also in some area of parameters where the trivial solution of the same system with Dirichlet and Neumann boundary conditions is stable. Theorems are proved using the method of a jump in the Leray-Schauder degree.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1023033910657
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  • 14
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    Diagonally implicit Runge–Kutta methods for 3D shallow water applications (2000)
    Springer
    Advances in computational mathematics 12 (2000), S. 229-250 
    Details
    ISSN: 1572-9044
    Keywords: numerical analysis ; shallow water problems ; DIRK methods ; stability ; 65L06 ; 65L20 ; 65M12 ; 65M20
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract We construct A‐stable and L‐stable diagonally implicit Runge–Kutta methods of which the diagonal vector in the Butcher matrix has a minimal maximum norm. If the implicit Runge–Kutta relations are iteratively solved by means of the approximately factorized Newton process, then such iterated Runge–Kutta methods are suitable methods for integrating shallow water problems in the sense that the stability boundary is relatively large and that the usually quite fine vertical resolution of the discretized spatial domain is not involved in the stability condition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018969203026
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  • 15
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    On the Robustness of Gaussian Elimination with Partial Pivoting (2000)
    Springer
    BIT 40 (2000), S. 62-73 
    Details
    ISSN: 1572-9125
    Keywords: Gaussian elimination ; stability ; pivoting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract It has been recently shown that large growth factors might occur in Gaussian Elimination with Partial Pivoting (GEPP) also when solving some plausibly natural systems. In this note we argue that this potential problem could be easily solved, with much smaller risk of failure, by very small (and low cost) modifications of the basic algorithm, thus confirming its inherent robustness. To this end, we first propose an informal model with the goal of providing further support to the comprehension of the stability properties of GEPP. We then report the results of numerical experiments that confirm the viewpoint embedded in the model. Basing on the previous observations, we finally propose a simple scheme that could be turned into (even more) accurate software for the solution of linear systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022314201484
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  • 16
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    Runge-Kutta Methods for the Numerical Solution of Stiff Semilinear Systems (2000)
    Springer
    BIT 40 (2000), S. 611-639 
    Details
    ISSN: 1572-9125
    Keywords: Runge-Kutta methods ; stability ; convergence ; stiff problems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract This paper studies the stability and convergence properties of general Runge-Kutta methods when they are applied to stiff semilinear systems y′(t) = J(t)y(t) + g(t, y(t)) with the stiffness contained in the variable coefficient linear part. We consider two assumptions on the relative variation of the matrix J(t) and show that for each of them there is a family of implicit Runge-Kutta methods that is suitable for the numerical integration of the corresponding stiff semilinear systems, i.e. the methods of the family are stable, convergent and the stage equations possess a unique solution. The conditions on the coefficients of a method to belong to these families turn out to be essentially weaker than the usual algebraic stability condition which appears in connection with the B-stability and convergence for stiff nonlinear systems. Thus there are important RK methods which are not algebraically stable but, according to our theory, they are suitable for the numerical integration of semilinear problems. This paper also extends previous results of Burrage, Hundsdorfer and Verwer on the optimal convergence of implicit Runge-Kutta methods for stiff semilinear systems with a constant coefficients linear part.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022332200092
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  • 17
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    Stochastic Methods for Ill-Posed Problems (2000)
    Springer
    BIT 40 (2000), S. 226-240 
    Details
    ISSN: 1572-9125
    Keywords: Stochastic differential equations ; regularisation ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract This paper is devoted to the numerical analysis of ill-posed problems of evolution equations in Banach spaces using certain classes of stochastic one-step methods. The linear stability properties of these methods are studied. Regularisation is given by the choice of the regularisation parameter as α = $$\sqrt {\tau _n }$$ , where τ n is the stepsize and provides the convergence on smooth initial data. The case of the approximation of well-posed problems is also considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022386822865
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  • 18
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    Hydraulic analysis of free-surface flows with solidification (2000)
    Springer
    Archive of applied mechanics 70 (2000), S. 17-29 
    Details
    ISSN: 1432-0681
    Keywords: Key words free-surface flow ; solidification ; strip casting ; steady state ; nonuniqueness ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary The paper is concerned with a one-dimensional analysis of plane open-channel flow with continuous solidification. The process is of relevance for recent developments in the casting of steel and other metals. The bottom of the channel consists of a rotating casting roll and a horizontal cooling table, where the solidified material is withdrawn with given velocity. The study is restricted to the region downstream of the top of the casting roll. Surface tension is neglected. In the main part of the analysis inviscid fluid flow is considered since the Reynolds number is very large in the applications. It is found that the steady-state solutions are nonunique in a certain parameter range. In addition to a continuous solution, there are two solutions including hydraulic jumps, with one hydraulic jump being located on the casting roll, the other one on the cooling table. Regarding the stability of the non unique solutions, the evolution of disturbances is investigated numerically as an initial-value problem. It is concluded that the hydraulic jump on the cooling table is unstable, while the other discontinuous solution as well as the continuous solution are stable for sufficiently small disturbances. Which stable solution is attained in the steady state, depends on the history of the process. Friction at the liquid/solid interface is taken into account in the last part of the analysis. A constant friction coefficient is assumed. It is found that the history of the process determines the steady-state solution if, and only if, the friction coefficient is sufficiently small. For larger values of the friction coefficient, the steady-state solution is unique and independent of the history of the transient process. Furthermore, for sufficiently large friction coefficients, stable hydraulic jumps are found, in contrast to the inviscid case, also on the cooling table.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004199900031
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  • 19
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    Concerning a Technique for Increasing Stability of Climbing Robots (2000)
    Springer
    Journal of intelligent and robotic systems 27 (2000), S. 195-209 
    Details
    ISSN: 1573-0409
    Keywords: wall-climbing robot ; electromagnetic grippers ; stability ; additional support element ; sliding and turning over conditions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Legged-climbing robot is considered. Each foot of the robot has an electromagnet system for robot"s holding on a metal surface. This surface can be both vertical and inclined, including negative slope. Analytical calculation of robot stability under turn over or sliding conditions has been made. Critical slopes have been determined. One of these slopes corresponds to minimal reserve of robot stability towards sliding and another to minimal reserve of robot stability towards turning-over. As total reserve of stability of a robot is always equal to the minimal one of these reserves. Additional support elements of elastic material with high coefficient of friction, along with electromagnet, allows to increase minimal reserve of robot stability towards sliding. The use of such support elements leads to redistributing force of normal support reaction between electromagnet (which surface has low coefficient of friction) and additional support element (which surface has high coefficient of friction). It is just what leads to increasing the total friction force and as a consequence to increasing of minimal reserve of robot stability towards sliding.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008158332368
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  • 20
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    Perron–Frobenius Theory and Symmetry of Solutions to Nonlinear PDE's (2000)
    Springer
    Letters in mathematical physics 53 (2000), S. 313-320 
    Details
    ISSN: 1573-0530
    Keywords: partial differential equations ; nonlinearities ; symmetries ; stability ; minimization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Notes: Abstract We suggest a simple but general method of establishing symmetry properties of stable solutions of nonlinear elliptic equations. The method relies on characterization of symmetry breaking with a help of zero modes and on a generalization of the Perron–Frobenius theory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007622208894
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  • 21
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    Simultaneous Records of Methane and Nitrous Oxide Emissions in Rice-Based Cropping Systems under Rainfed Conditions (2000)
    Springer
    Nutrient cycling in agroecosystems 58 (2000), S. 131-139 
    Details
    ISSN: 1573-0867
    Keywords: automated closed chamber method ; wheat ; cowpea ; slow-release nitrogen fertilizer ; residue management ; denitrification ; methane sink ; rainfall
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Rainfed rice (Oryza sativa L.)-based cropping systems are characterized by alternate wetting and drying cycles as monsoonal rains come and go. The potential for accumulation and denitrification of NO3 − is high in these systems as is the production and emission of CH4 during the monsoon rice season. Simultaneous measurements of CH4 and N2O emissions using automated closed chamber methods have been reported in irrigated rice fields but not in rainfed rice systems. In this field study at the International Rice Research Institute, Philippines, simultaneous and continuous measurements of CH4 and N2O were made from the 1994 wet season to the 1996 dry season. During the rice-growing seasons, CH4 fluxes were observed, with the highest emissions being in organic residue-amended plots. Nitrous oxide fluxes, on the other hand, were generally nonexistent, except after fertilization events where low N2O fluxes were observed. Slow-release N fertilizer further reduced the already low N2O emissions compared with prilled urea in the first rice season. During the dry seasons, when the field was planted to the upland crops cowpea [Vigna unguiculata (L.) Walp] and wheat (Triticum aestivum L.), positive CH4 fluxes were low and insignificant except after the imposition of a permanent flood where high CH4 fluxes appeared. Evidences of CH4 uptake were apparent in the first dry season, especially in cowpea plots, indicating that rainfed lowland rice soils can act as sink for CH4 during the upland crop cycle. Large N2O fluxes were observed shortly after rainfall events due to denitrification of accumulated NO3 −. Cumulative CH4 and N2O fluxes observed during this study in rainfed conditions were lower compared with previous studies on irrigated rice fields.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009842502608
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  • 22
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    Stability of Attractive Bose–Einstein Condensates (2000)
    Springer
    Journal of statistical physics 101 (2000), S. 731-746 
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    ISSN: 1572-9613
    Keywords: attractive Bose–Einstein condensates ; nonlinear Schrödinger equation ; stability ; ground state ; variational arguments
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We propose the critical nonlinear Schrödinger equation with a harmonic potential as a model of attractive Bose–Einstein condensates. By an elaborate mathematical analysis we show that a sharp stability threshold exists with respect to the number of condensate particles. The value of the threshold agrees with the existing experimental data. Moreover with this threshold we prove that a ground state of the condensate exists and is orbital stable. We also evaluate the minimum of the condensate energy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026437923987
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  • 23
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    Improved growth and water use efficiency of cherry saplings under reduced light intensity (2000)
    Springer
    Ecological research 15 (2000), S. 385-392 
    Details
    ISSN: 1440-1703
    Keywords: photosynthesis ; Prunus avium ; relative growth rate ; shading ; total plant water use efficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Cherry (Prunus avium L.) saplings were grown under natural sunlight (controls) or moderate shading (up to 30%, depending on the incident light intensity and the hour of the day). Reduced light intensity increased the dry mass of each of the plant components studied. Consequently, the total dry mass of shaded plants was significantly greater than that of controls at the end of the growing season. However, the diurnal trend in the level of photosynthesis (per unit of leaf area) of shaded plants was similar to the controls in August, but lower in September. As the growing season proceeded, reduced photosynthetic rates, thinner mesophyll and larger specific leaf area in the shaded plants indicated that leaf development had adapted to shaded conditions throughout the growing season. It is suggested that increased growth of shaded plants was caused by a higher initial relative growth rate and a greater whole-plant photosynthesis. Shading consistently reduced transpiration over the season, therefore improving water use efficiency of shaded leaves. Our results suggest that a moderate reduction in light intensity can be a useful method for improving growth and saving water in hot and dry environments.
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    URL: http://dx.doi.org/10.1046/j.1440-1703.2000.00359.x
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    On the Stability of Functional Equations and a Problem of Ulam (2000)
    Springer
    Acta applicandae mathematicae 62 (2000), S. 23-130 
    Details
    ISSN: 1572-9036
    Keywords: stability ; functional equations ; Cauchy difference ; semigroup ; inequalities ; approximate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract In this paper, we study the stability of functional equations that has its origins with S. M. Ulam, who posed the fundamental problem 60 years ago and with D. H. Hyers, who gave the first significant partial solution in 1941. In particular, during the last two decades, the notion of stability of functional equations has evolved into an area of continuing research from both pure and applied viewpoints. Both classical results and current research are presented in a unified and self-contained fashion. In addition, related problems are investigated. Some of the applications deal with nonlinear equations in Banach spaces and complementarity theory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006499223572
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    Debonding of the interface as 'crack arrestor' (2000)
    Springer
    International journal of fracture 105 (2000), S. 57-79 
    Details
    ISSN: 1573-2673
    Keywords: Interface toughness ; interface debonding ; stability ; adhesive interface ; bimaterial.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract In this paper, we studied the interface debonding when a crack perpendicularly approaches an interface between two dissimilar elastic materials. An interface toughness law was first defined according to an adhesive model governing the interface fracture. By analysing the interaction between the normally approaching crack and the interface crack and by tacking account of the adhesive forces at ends of the interfacial crack, a model for studying the interface debonding and the debonding stability was established. It is observed that the interface debonding toughness depends strongly on the mixed mode locally produced over the plastic adhesive zone of the interface. Moreover, the interface debonding may be unstable, i.e. the interface debonding length may jump from an initial value to a certain final value under critical remote loading. This jump may be surprisedly important in certain cases. These results agree with the experimental works gathered so far and can be used to explain the mechanism of 'crack arrestor' formed by an interface.
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    URL: http://dx.doi.org/10.1023/A:1007603809972
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    Effects of Ca2+ on the Activity and Stability of Methanol Dehydrogenase (2000)
    Springer
    The protein journal 19 (2000), S. 469-473 
    Details
    ISSN: 1573-4943
    Keywords: Methanol dehydrogenase ; Ca2+ ; binding ; activity ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The effects of exogenously added Ca2+ on the enzymatic activity and structural stability of methanol dehydrogenase were studied for various Ca2+ concentrations. Methanol dehydrogenase activity increased significantly with increasing concentration of Ca2+, approaching saturation at 200 mM Ca2+. The effect of Ca2+ on the activation of MDH was time dependent and Ca2+ specific and was due to binding of the metal ions to the enzyme. Addition of increasing concentration of Ca2+ caused a decrease of the intrinsic tryptophan fluorescence intensity in a concentration-dependent manner to a minimum at 200 mM, but with no change in the fluorescence emission maximum wavelength or the CD spectra. The results revealed that the activation of methanol dehydrogenase by Ca2+ occurred concurrently with the conformational change. In addition, exogenously bound Ca2+ destabilized MDH. The potential biological significance of these results is discussed.
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    URL: http://dx.doi.org/10.1023/A:1026597314542
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    The Energy Budget of Coral Polyps (2000)
    Springer
    Russian journal of marine biology 26 (2000), S. 389-398 
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    ISSN: 1608-3377
    Keywords: hermatypic coral ; zooxanthella ; photosynthesis ; respiration ; energy budget
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We analyzed the recent data on the distribution of the photosynthetic energy of zooxanthellae in corals and the models of interactions between the plant and animal cells in the course of matter and energy exchange developed based on this information. The models of energy exchange of animals symbiotic with zooxanthellae are characterized by the following features: (1) A flow chart of carbon or energy fluxes is the main form of representation of the energetics in native symbiotic organisms. (2) The relations between the symbionts are relatively adequately revealed and correspond to the modern notions; however, the intensities of the energy fluxes ascribed to these relations are dependent on the experimental and design methods used by the authors. (3) The inputs into the energy budget consist of the autotrophic production of zooxanthellae and the heterotrophy of the polyp. The energy expenditures comprise excretion, respiration, development, and growth of the animal and algae. (4) The differences between the species, genera, and phyla of animals that develop symbiotic relations with zooxanthellae are confined to the absolute values of energy fluxes in the organism.
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    URL: http://dx.doi.org/10.1023/A:1009497303413
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    Bifurcations of a cantilevered pipe conveying steady fluid with a terminal nozzle (2000)
    Springer
    Acta mechanica Sinica 16 (2000), S. 264-272 
    Details
    ISSN: 1614-3116
    Keywords: nonlinear dynamics ; bifurcation ; stability ; fluid-solid interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract This paper studies interactions of pipe and fluid and deals with bifurcations of a cantilevered pipe conveying a steady fluid, clamped at one end and having a nozzle subjected to nonlinear constraints at the free end. Either the nozzle parameter or the flow velocity is taken as a variable parameter. The discrete equations of the system are obtained by the Ritz-Galerkin method. The static stability is studied by the Routh criteria. The method of averaging is employed to examine the analytical results and the chaotic motions. Three critical values are given. The first one makes the system lose the static stability by pitchfork bifurcation. The second one makes the system lose the dynamical stability by Hopf bifurcation. The third one makes the periodic motions of the system lose the stability by doubling-period bifurcation.
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    URL: http://dx.doi.org/10.1007/BF02487667
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    Long-term monitoring of benthic macroinvertebrate community structure: a perspective from a Colorado river* (2000)
    Springer
    Aquatic ecology 34 (2000), S. 261-278 
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    ISSN: 1573-5125
    Keywords: discharge effects on lotic invertebrates ; disturbance ; persistence ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Temporal and spatial trends were examined in benthic macroinvertebrate and physical-chemical data collected for at least ten years at ten sites along the plains reach of the Cache la Poudre River, Colorado, USA. A distinct longitudinal environment gradient was found as many of the water chemistry parameter levels changed downstream from the reference site. Seasonal Kendall analyses on individual sites indicated that several chemical parameters, including conductivity, un-ionized NH3-N and NO2-N have increased since the beginning of the study within most sites. Levels of some parameters (e.g., dissolved oxygen, un-ionized NH3-N) violated aquatic life standards a few times during the study. Over 175 taxa of macroinvertebrates (primarily insects) were collected in the study reach from 1981–1996. Results from detrended correspondence analyses (DCA) on macroinvertebrate data indicated that this stretch of the river exhibited little longitudinal change beyond the two farthest upstream sites. There was a decline in macroinvertebrate density and total number of taxa within most individual sites during 1983–1984, corresponding with the highest recorded discharge in 75 years (1983) and a prolonged, heavy spring runoff in 1984. Taxa richness and density recovered to pre-1983 levels within a few months to a year following the high flows at most sites. These findings suggested that the macroinvertebrate assemblages had low resistance to disturbance, but high resilience. However, the results from DCAs and Kendall's Coefficient of Concordance (W) on individual sites for the entire study period suggested a similar macroinvertebrate community structure through time. It would appear that the composition and abundance of the lotic macroinvertebrate assemblages in the Poudre River has remained relatively constant over the long-term. This has occurred even with some potentially negative changes in water chemistry and increased urban development.
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    URL: http://dx.doi.org/10.1023/A:1009989510721
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    Influence of chlorophyll concentrations on the reliability of measurements with an oxygen electrode when studying photosynthetic efficiency in bioassays using microalgae (2000)
    Springer
    Journal of applied phycology 12 (2000), S. 63-67 
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    ISSN: 1573-5176
    Keywords: Euglena gracilis ; Chlamydomonas reinhardtii ; photosynthesis ; oxygen electrode ; Light Pipette ; bioassay ; chlorophyll concentration ; algae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Euglena gracilis and Chlamydomonas reinhardtii were used as model organisms to establish the best conditions for studying photosynthetic efficiency using the Light Pipette – experimental system, which enables sensitive detection of changes in oxygen evolution/consumption and an easy collection and digitalisation of data. Chlorophyll concentrations of 0.005, 0.025, 0.050 and 0.075 mgmL-1 were investigated using different light regimes. Cultures of E. gracilis at the same chlorophyll concentration absorbed more light(measured at 580 μmol m-2 s-1) than those of C. reinhardtii. Cell density had a considerable effect on the reliability of measurements. Chlorophyll concentrations between 0.025 mgChl ml-1 and 0.050 mgChlml-1 can be recommended when applying the Light Pipette system in bioassays using microalgae.
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    URL: http://dx.doi.org/10.1023/A:1008189230953
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    Effect of UV radiation on photoinhibition of marine macrophytes in culture systems (2000)
    Springer
    Journal of applied phycology 12 (2000), S. 159-168 
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    ISSN: 1573-5176
    Keywords: Chlorophyll fluorescence ; Chondruscrispus ; Macrocystis pyrifera ; photosynthesis ; photoinhibition ; outdoor culture system ; Ulvalactuca ; UV-radiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The present study examined the effect of UV andphotosynthetically active radiation (PAR) onphotoinhibition and recovery in the Phaeophyte Macrocystis pyrifera, the Rhodophyte Chondruscrispus and the Chlorophyte Ulva lactuca underoutdoor culture conditions. There was an increase inphotoinhibition as a consequence of high exposure toUV-B radiation in M. pyrifera, however, highlevels of PAR accounted for most of thephotoinhibition in C. crispus and U.lactuca. Photodamage by UV-A, UV-B and PAR wascompletely repaired within 5 h and effective quantumyield reached pretreatment values in the three speciesstudied. Species were less susceptible tophotoinhibition after being incubated for 5 d underhigh exposures of natural irradiance suggesting aphotoadaptive process. The recovery of the effectivequantum yield was impaired by long exposure to highlevels of UV-B in C. crispus and UV-A, UV-B andPAR in M. pyrifera. This suggests a differentkind of damage by UV-A and PAR radiation, one to thephotosynthetic apparatus and another which affects therepair mechanism of some species. There was anincrease in UV-absorption (λ 330 nm) in M. pyrifera and C. crispus within four days ofthe initiation of the experiment suggesting that thesespecies photoprotect their photosynthetic system whenexposed to elevated UV and PAR levels.
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    Effect of a cationic cellulosic polymer on gametophytes of Laminaria digitata (Laminariaceae, Phaeophyta): Improvement of dispersed `free-living' cultures (2000)
    Springer
    Journal of applied phycology 12 (2000), S. 83-93 
    Details
    ISSN: 1573-5176
    Keywords: fluorescence ; homogeneous culture ; JR125 polymer ; Laminaria ; gametophytes ; photosynthesis ; ultrastructural studies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract As filament aggregation is responsible for heterogeneity of Laminariales gametophyte cultures, a project was conducted to obtain stable homogeneous `free-living' cultures of Laminaria digitatagametophytes. The alga was cultivated at 15 ° Cunder low light and in the presence of a cationic cellulosic polymer, JR125. With 0.1%polymer in the culture medium, the filaments were dispersed and did not adhere to the culture vessel. The absence of any effect of the closely related, but uncharged, polymer LR-250 Natrasol on filament aggregation indicated that the cationic nature of the JR125 molecule was involved in gametophyte dissociation. In the presence of JR125, the gametophytes showed active vegetative growth; the doubling time, measured as chlorophyll concentration, was 5 days. The outer surface of the cell wall was clearly modified by the polymer treatment, as observed by transmission electron microscopy, while neither the inner cell wall or cell organelles were affected. Physiological studies indicated that JR125 treatment did not disturb cell physiology, there being no effecton respiration, photosynthetic activity, sensitivity to high-light stress or modification of pigment or fluorescence characteristics. We have therefore established the conditions for maintaining a stable culture of mixed male and female Laminaria digitata gametophytes in active vegetative growth. The presence of JR 125 in the medium yields a homogeneous culture without cell physiology becoming modified.
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    Lithophytic algae: A major threat to the karst formation of show caves (2000)
    Springer
    Journal of applied phycology 12 (2000), S. 309-315 
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    ISSN: 1573-5176
    Keywords: nuisance algae ; bio-fouling ; photosynthesis ; lightutilisation ; show caves ; control measures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Depending on the intensity, quality and duration ofthe illumination, necessary for viewing show caves,conditions conducive for algal growth are created. Although algae are the major component of this flora,ferns and mosses have also been recorded. Little isknown of the algae, except that they are considered anuisance in terms of discoloration and damage to thekarst formations. The occurrence and possible controlof the algal flora has been studied in the CangoCaves, one of the most important touristic sites inSouth Africa. The algal flora is sparse in speciesdiversity and primitive forms are present. They haveparticular physiological adaptations and usingmicro-oxygen liberation and fluorescence measurements,their photosynthetic characteristics were established. Environmentally friendly control measures wereinvestigated and a solution for their control is proposed.
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    URL: http://dx.doi.org/10.1023/A:1008172227611
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    Physiological and technological considerations for optimising mass algal cultures (2000)
    Springer
    Journal of applied phycology 12 (2000), S. 201-206 
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    ISSN: 1573-5176
    Keywords: photobioreactors ; high yields ; photosynthesis ; single stage reactors ; multistage reactors ; strain selection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The successful coupling between physiology andtechnology is central to the success of algalbiotechnology. Imperative is a proper understandingof the variables and their impacts on biomass and/orbiocompound production. The crux lies inphotosynthesis and the capturing of light energy atthe optimal rate for eventual maximal photochemistry(biosynthesis). It is in the hands of algalbiotechnologists to understand the dynamics andregulatory mechanisms of especially PSII (photosystemII) activity in order to advance this technologyfurther. Biophysical and technological optimisationand design aimed at maximising photon flux capture aresome of the avenues that needs be pursued. This needsto be augmented by molecular, biochemical andphysiological inputs. Unfortunately detailedsystematic analyses of the variables, theirinteraction and possible synergism have rarely beendone. The debate regarding the merits andproductivity in closed, either plate or tubular,vertical or horizontal, and open pond reactors need tobe resolved. Exciting developments regarding onlinemeasurements and feedback control for optimalproductivities are part of the solutions andapproaches that need to be followed. Multistagesystems that not only utilise autotrophic growth andstress components, but also combinedautotrophic/heterotrophic systems could providesolutions to specific production requirements. Theseand other important issues are addressed in theoverview. The challenges facing algalbiotechnologists and future research needs are also discussed.
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    Numerical solutions for a coupled non-linear oscillator (2000)
    Springer
    Journal of mathematical chemistry 28 (2000), S. 325-340 
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    ISSN: 1572-8897
    Keywords: numerical method ; stability ; Hopf bifurcation ; coupled oscillator
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mathematics
    Notes: Abstract A second-order accurate numerical method has been proposed for the solution of a coupled non-linear oscillator featuring in chemical kinetics. Although implicit by construction, the method enables the solution of the model initial-value problem (IVP) to be computed explicitly. The second-order method is constructed by taking a linear combination of first-order methods. The stability analysis of the system suggests the existence of a Hopf bifurcation, which is confirmed by the numerical method. Both the critical point of the continuous system and the fixed point of the numerical method will be seen to have the same stability properties. The second-order method is more competitive in terms of numerical stability than some well-known standard methods (such as the Runge–Kutta methods of order two and four).
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    URL: http://dx.doi.org/10.1023/A:1011025104111
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    Responses of Porphyra linearis (Rhodophyta) to environmental factors under controlled culture conditions (2000)
    Springer
    Journal of applied phycology 12 (2000), S. 535-542 
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    ISSN: 1573-5176
    Keywords: desiccation ; growth ; growth model ; inorganic carbon ; nutrients ; photoperiod ; photosynthesis ; pigments ; Porphyra linearis ; PPF ; respiration ; temperature ; water velocity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effect of environmental parameters on the growthof Porphyra linearis gametophytes was examinedunder controlled conditions, and related to themultilinear regression growth model recently developedfor this seaweed under coastal conditions in theeastern Mediterranean. Growth chambers, a gradienttable, special culture devices and analytical methodswere combined for this culture study.The major factors significantly controlling thegrowth rate of the P. linearis gametophytein glass dishes were: photoperiod, temperature, agein culture, photosynthetic photon flux (PPF), salinityand water dynamics. Maximal growth occurred underdaylength of 12 h, medium temperature (15–20 °C), low PPF (70–140 μmol photon m-2s-1), ambient salinity (30–40 ppt), 1–3 h ofdaily air exposure, and water velocity of 4 cm s-1.Photosynthesis and respiration rates weredominantly affected by daylength and temperature,while the concentration of pigments was dominantlyaffected by PPF and temperature.These conditions correspond well to the optimalnatural growth environment of this local species andare in agreement with the optimum estimated throughthe recently developed outdoor mathematical growthmodel.
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    The effect of reducing light-harvesting pigment on marine microalgal productivity (2000)
    Springer
    Journal of applied phycology 12 (2000), S. 285-290 
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    ISSN: 1573-5176
    Keywords: algal culture ; Chlamydomonas perigranulata ; light-harvesting pigment ; photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The productivity was evaluated of a strain of Chlamydomonas perigranulata isolated from the RedSea. A mutant with small light-harvesting pigments(LHC-1) was obtained by UV mutagenesis. Thechlorophylls content of the wild type was twice ashigh as that of LHC-1, and the initial slope of thephotosynthesis-irradiance curve was higher in the wildtype. However, the maximum photosynthetic activity ona per cell basis was almost the same. It isconcluded that LHC-1 is a mutant with lesslight-harvesting pigment (LHP) than the wild type. Aspreviously reported, the mutant with lower LHP contenthas a higher productivity in a continuous culturesystem, so we compared the productivity of the wildtype and the mutant. The maximum productivity of LHC-1was 1.5 times higher than that of the wild type. Itis suggested that the technique of reducing thecontent of light-harvesting pigment should be madeavailable for other organisms.
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    Development of a STS marker linked to a major locus controlling flour colour in wheat (Triticum aestivum L.) (2000)
    Springer
    Molecular breeding 6 (2000), S. 169-174 
    Details
    ISSN: 1572-9788
    Keywords: AFLP ; flour colour ; STS ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Flour colour is an important quality trait in the production of bread, noodles and other related end products. Current screening for flour colour in breeding programs requires several grams of flour to be milled. In order to screen large numbers of plants, a rapid PCR-based assay is required. We report here the conversion of a codominant AFLP marker linked to a major locus controlling flour colour in hexaploid wheat, to a sequence tagged site (STS) marker for use in marker-assisted selection (MAS). The two-allelic AFLP bands were cloned and sequenced to allow specific primers to be designed. The primers amplified bands of the expected size in the parental varieties and co-segregated with the original AFLP marker in the mapping population. The primers also amplified alleles of the expected size from the DNA of parental lines of two other related mapping populations. Cultivars that contributed to the pedigree of the original parent `Schomburgk' used to generate the mapping population were also screened to determine the origin of the `yellow' allele.
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    Stromatolitic communities in Mediterranean streams: adaptations to a changing environment (2000)
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    Biodiversity and conservation 9 (2000), S. 379-392 
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    ISSN: 1572-9710
    Keywords: climate change ; cyanobacteria ; ectoenzymes ; Mediterranean ; nutrient limitation ; photosynthesis ; stromatolite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A stromatolitic microbial mat extensively covers La Solana streambed, a calcareous Mediterranean stream. This stromatolite shows remarkable biological and physiological diversity. It is mainly composed by cyanobacteria, with Rivularia and Schizothrix as the most abundant taxa. The stromatolite is photosynthetically adaptated to the high irradiances reaching the streambed. Photosynthetically active chlorophyll is present even in the lowest layers of the stromatolite, indicating the presence of well-preserved cyanobacteria in that part. Diffusion of gases and nutrients within the stromatolite can be possible because of the high porosity of the crust. It has been experimentally established that the stromatolite recovers heterotrophic and autotrophic activities in a few hours, after being desiccated for long periods. Recovery after desiccation is indicative of the high resilience of this community to environmental extremes, which are common in Mediterranean climatic regimes. The stromatolitic community is adapted to nutrient limitation, both to low availability of inorganic phosphorus and nitrogen (that constrain growth of primary producers), and to low dissolved organic carbon (mainly affecting heterotrophs). Stromatolitic heterotrophs mainly rely on the organic carbon stored in the crust as the main organic carbon source. These strategies are the direct response of the stromatolite to oligotrophy, and justify the restricted occurrence in stream systems affected by organic pollution.
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    Potential use of Cu2+, K+ and Na+ for the destruction of Caulerpa taxifolia: differential effects on photosynthetic parameters (2000)
    Springer
    Journal of applied phycology 12 (2000), S. 15-23 
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    ISSN: 1573-5176
    Keywords: Caulerpa taxifolia ; chlorophyll fluorescence ; copper ; photosynthesis ; potassium ; respiration ; RubisCO ; sodium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Chemical techniques were investigated in order to eradicate Caulerpa taxifolia, a green alga spreading at a remarkable rate in the Mediterranean Sea. The action of copper, potassium and sodium ions on survival rates and photosynthetic parameters was compared, in order to optimise the conditions of further in situ treatments. The lethal doses were determined and the impact of the studied cations on photosynthesis and respiration rates and PSII photochemistry was analysed from measurements of net oxygen exchanges and chlorophyll fluorescence. The Cu2+ concentrations required to obtain 100% mortality were 15 × 102 to 104 times lower than those of K+ and Na+. Respiration was slightly affected whatever the salt concentration,while photosynthesis could be totally inhibited depending on the applied treatment. Changes in the structure of the Ribulose-1,5-biphosphate carboxylase/oxygenase (RubisCO, EC: 4.1.1.39) were also detected when C. taxifolia under went cation treatments (10 mg L-1 Cu2+, 1h; 20 gL-1 K+, 3 h; 20 g L-1 Na+, 1 h). Given the high concentration and long incubation periods required with K+ and Na+ ions, these cations are not suitable to be used in situ. Our results make possible the utilisation of copper cations following technical approaches such asion-exchange textile covers, which allows a controlled release of cupric ions without dissemination in the marine environment.
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    URL: http://dx.doi.org/10.1023/A:1008108531280
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    1,3-Dihydrobenzo[c]thienylium (thiophthalylium) salts. (Review) (2000)
    Springer
    Chemistry of heterocyclic compounds 36 (2000), S. 115-133 
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    ISSN: 1573-8353
    Keywords: thiophthalylium salts ; methods of preparation ; structure ; stability ; reactivity ; electrophilic properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Methods of preparation, chemical reactions, the structures and reactivity of thiophthalylium ions are reviewed.
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    Solving A $$\underline x $$ = $$\underline b $$ Using a Modified Conjugate Gradient Method Based on Roots of A (2000)
    Springer
    Journal of scientific computing 15 (2000), S. 441-456 
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    ISSN: 1573-7691
    Keywords: modified conjugate gradient method ; conjugate gradient method ; Krylov space ; convergence rate ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract We consider the modified conjugate gradient procedure for solving A $$\underline x $$ = $$\underline b $$ in which the approximation space is based upon the Krylov space associated with A 1/p and $$\underline b $$ , for any integer p. For the square-root MCG (p=2) we establish a sharpened bound for the error at each iteration via Chebyshev polynomials in $$\sqrt A$$ . We discuss the implications of the quickly accumulating effect of an error in $$\sqrt A$$ $$\underline b $$ in the initial stage, and find an error bound even in the presence of such accumulating errors. Although this accumulation of errors may limit the usefulness of this method when $$\sqrt A$$ $$\underline b $$ is unknown, it may still be successfully applied to a variety of small, “almost-SPD” problems, and can be used to jump-start the conjugate gradient method. Finally, we verify these theoretical results with numerical tests.
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    Associative Memories in Infinite Dimensional Spaces (2000)
    Springer
    Neural processing letters 12 (2000), S. 129-144 
    Details
    ISSN: 1573-773X
    Keywords: associative memory ; dynamical systems ; Glauber dynamics ; Hopfield model ; infinite dimensional state space ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract A generalization of the Little–Hopfield neural network model for associative memories is presented that considers the case of a continuum of processing units. The state space corresponds to an infinite dimensional euclidean space. A dynamics is proposed that minimizes an energy functional that is a natural extension of the discrete case. The case in which the synaptic weight operator is defined through the autocorrelation rule (Hebb rule) with orthogonal memories is analyzed. We also consider the case of memories that are not orthogonal. Finally, we discuss the generalization of the non deterministic, finite temperature dynamics.
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    Partial Compensation for Mismatched Uncertain Discrete Systems (2000)
    Springer
    Dynamics and control 10 (2000), S. 47-61 
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    ISSN: 1573-8450
    Keywords: stability ; robust control ; Lyapunov approach ; discrete system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Control design of nonlinear discrete-time uncertain systems with (possibly fast) uncertain parameters is considered. We study the effect of only partially compensating the uncertainty. The optimal choice of a design parameter, which indicates the amount of compensation, is recommended.
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    URL: http://dx.doi.org/10.1023/A:1008395928788
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    Optimal Model Reduction with a Frequency Weighted Extension (2000)
    Springer
    Dynamics and control 10 (2000), S. 255-276 
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    ISSN: 1573-8450
    Keywords: continuous-time systems ; frequency weighted model reduction ; gradient flow ; optimization ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Inthis paper, a model reduction technique based on optimizationis presented. The objective function minimized is the impulseenergy of the overall system. An extension of the technique tothe frequency weighted case is also presented, where single-sidedor double-sided weightings can be incorporated in the reductionprocedure. The paper proposes an alternative to find an optimizationsolution by solving ordinary differential equations which aregradient flow associated with the objective function to be minimized.Two examples are presented to illustrate the effectiveness ofthe method.
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    The Equation of State of Lakes (2000)
    Springer
    Aquatic geochemistry 6 (2000), S. 1-17 
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    ISSN: 1573-1421
    Keywords: lakes ; density ; compressibility ; expansibility ; conductivity ; stability ; pvt properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract In recent years, a number of workers have studied the stability of deep lakes such as Lake Tanganyika, Lake Baikal and Lake Malawi. In this paper, the methods that can be used to determine the effect that the components of lakes have on the equation of state are examined. The PVT properties of Lakes have been determined by using apparent molal volume data for the major ionic components of the lake. The estimated PVT properties (densities, expansibility and compressibilities) of the lakes are found to be in good agreement with the PVT properties (P) of seawater diluted to the same salinity. This is similar to earlier work that showed that the PVT properties of rivers and estuarine waters could also be estimated from the properties of seawater. The measured densities of Lake Tanganyika were found to be in good agreement (± 2 × 10-6 g cm-3) with the values estimated from partial molal properties and the values of seawater at the same total salinity (ST = 0.568‰). The increase in the densities of Lake Tanganyika waters increased due to changes in the composition of the waters. The measured increase in the measured density (45 × 10-6 g cm-3) is in good agreement (46 × 10-6 g cm-3) with the values calculated for the increase in Na+, HCO3 -, Mg2+, Ca2+ and Si(OH)4. Methods are described that can be used to determine the conductivity salinity of lakes using the equations developed for seawater. By combining these relationships with apparent molal volume data, one can relate the PVT properties of the lake to those of seawater.
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    Surface Instability of Laminated Coatings upon Inelastic Deformation (2000)
    Springer
    Mechanics of composite materials 36 (2000), S. 475-480 
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    ISSN: 1573-8922
    Keywords: stability ; three-dimensional theory ; tribotechnics ; elastoplastic deformations ; viscoelasticity ; surface ; tracking and dead loads ; laminated coating ; piecewise-homogeneous model ; active loading
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The problem of surface instability of laminated coatings with inelastic properties is considered within the framework of a model of piecewise-homogeneous media on the basis of the three-dimensional linearized theory of stability. A general statement of the problem is formulated and the basic characteristic equations are derived. The solutions of particular problems are obtained for elastoplastic and viscoelastic models of solids.
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    Middle Layer Intrusion as an Important Factor Supporting Phytoplankton Productivity at a Tidal Front in Iyo Nada, the Seto Inland Sea, Japan (2000)
    Springer
    Journal of oceanography 56 (2000), S. 131-139 
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    ISSN: 1573-868X
    Keywords: Tidal front ; nutrient ; phytoplankton ; photosynthesis ; stratification ; mixing ; Iyo Nada
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Field observations were conducted to examine the processes governing the phytoplankton distribution and photosynthetic activity in and around a tidal front formed in Iyo Nada, the Seto Inland Sea, Japan. The existence of a middle layer intrusion, which, it has been suggested, moves from the mixed region to the stratified region of the tidal front, was ascertained by the phytoplankton distribution in addition to a T-S diagram. Skeletonema costatum, which originally inhabited the mixed region, was used as the indicator to reveal the intrusion. However, the tip of water containing the S. costatum population did not extend deeply into the stratified region. The velocity of the intrusion seemed to be slow enough to make biological processes, such as nutrient uptake by phytoplankton and subsequent growth, as well as the decrease in cell density due to zooplankton grazing, dominate during the transportation. The patchy distribution of copepod nauplii implied that grazing has an influence on the distribution pattern of phytoplankton. The location of high photosynthetic activity did not coincide spatially with the center of high phytoplankton biomass, suggesting the importance of these biological processes. Therefore, it is considered that the middle layer intrusion plays a role as an inducer of subsequent biological processes at the tidal front by not only supplying nutrients from the mixed region but also by increasing the vertical diffusivity.
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    On the Stability of Nonconservative Systems with Estimation of the Attraction Domain (2000)
    Springer
    Journal of dynamical and control systems 6 (2000), S. 503-510 
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    ISSN: 1573-8698
    Keywords: nonconservative mechanical systems ; stability ; Lyapunov functions ; attraction domain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Mechanical systems subjected to dissipative, gyroscopic, conservative, and also nonconservative positional forces are considered. The question of the effect of dissipative, gyroscopic, and conservative forces on the motion stability of a mechanical systems is determined by classical Kelvin–Chetaev theorems [1]. The presence of nonconservative positional forces considerably complicates the situation and excludes direct application of these theorems. Applying Lyapunov's functions method the condition of asymptotic stability of a mechanical system under the action of all listed above forces is obtained. Moreover, the estimation of the attraction domain in phase space is found. The precession system which is used in the solution of some problems in the applied theory of the gyroscopic systems is also examined. The connection between the stability of origin and precession systems is detected. Theoretical results are applied to the stabilization problem of stationary motion of the balanced gimbal suspension gyro by means of external moments.
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    CO2 gas exchange of benthic microalgae during exposure to air: a technique for the rapid assessment of primary production (2000)
    Springer
    Wetlands ecology and management 8 (2000), S. 273-280 
    Details
    ISSN: 1572-9834
    Keywords: light curves ; mangrove ; microphytobenthos ; photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A method of measuring CO2gas exchange (caused, for example, by microalgal photosynthesis on emersed tidal mudflats) using open flow IR gas analyzers is described. The analyzers are integrated in a conventional portable photosynthesis system (LI-6400, LI-COR, Nebraska, USA), which allows manipulation and automatic recording of environmental parameters at the field site. Special bottomless measuring chambers are placed directly on the surface sediment. Measurements are performed under natural light conditions and ambient CO2concentrations, as well as under different CO2concentrations in air, and various PAR radiation levels produced by a LED light source built into one of the measurement chambers. First results from tidal channel banks in a north Brazilian mangrove system at Bragança (Pará, Brazil) under controlled conditions show a marked response of CO2assimilation to CO2concentration and to irradiance. Photosynthesis at 100 μmol mol−1CO2in air in one sample of a well-developed algal mat was saturated at 309 μmol photons m−2s−1, but increased with increasing ambient CO2concentrations (350 and 1000 μmol mol−1CO2) in the measuring chamber. Net CO2assimilation was 0.8 μmol CO2 m−2s−1at 100 μmol mol−1CO2, 5.9 μmol CO2m−2s−1at 350 μmol mol−1CO2and 9.8 μmol CO2m−2s−1at 1000 μmol mol−1CO2. Compensation irradiance decreased and apparent photon yield increased with ambient CO2concentration. Measurements under natural conditions resulted in a quick response of CO2exchange rates when light conditions changed. We recommend the measuring system for rapid estimations of benthic primary production and as a valuable field research tool in connection with certain ecophysiological aspects under changing environmental conditions.
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    The influence of crop management on the water balance of lupin and wheat crops on a layered soil in a Mediterranean climate (2000)
    Springer
    Plant and soil 221 (2000), S. 239-251 
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    ISSN: 1573-5036
    Keywords: drainage ; duplex soil ; evapotranspiration ; lupin ; waterlogging ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The influence of time of sowing and sowing density on evapotranspiration and drainage loss beneath wheat (Triticum aestivum cv. Spear) and lupin (Lupinus angustifolius cv. Gungurru) crops grown on a layered soil was investigated for three seasons in a Mediterranean climate in Western Australia. The aim of the study was to investigate whether managing crops to maximise their canopy growth would increase their water use and minimise groundwater recharge contributing to dryland salinity. A soil water balance approach was used to estimate evapotranspiration, with changes in soil water content measured with a neutron water meter. The study was carried out on a layered soil typical of agricultural soils in the region with variable depth to clay (0.22–0.38 m) and a marked contrast in hydraulic properties between the topsoil and subsoil. As a result of the low permeability subsoil, a perched water table occurred in the sandy topsoil in each of the three seasons under study during winter when rainfall was high and potential evaporation low. Perched water tables persisted for 2–3 months, with hydraulic gradients consistently downward causing drainage losses to occur. Although crop management had a large influence on shoot and root development, evapotranspiration from the different treatments was generally similar. Drainage losses were not influenced by either crop type, time of sowing or sowing density, because potential evaporation and hence evapotranspiration was low during the period when drainage losses occurred. The total drainage loss measured in each season was different, with losses ranging from 20.1 to 22.2 mm in 1990, from 40.4 to 46.7 mm in 1991 and from 49.4 to 66.6 mm in 1992. The increase in drainage loss from 1990 to 1992 was a result of progressively more seasonal rainfall in 1990, 1991 and 1992. It was concluded that there was little scope to increase water use and decrease deep drainage through crop management for sites with climatic conditions where winter rainfall exceeds potential evaporation.
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    Availability of different forms of sulphur fertilisers to wheat and oilseed rape (2000)
    Springer
    Plant and soil 222 (2000), S. 139-147 
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    ISSN: 1573-5036
    Keywords: elemental sulphur ; oilseed rape ; sulphate ; sulphur fertilisers ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A pot experiment was conducted to compare the availability and efficiency of three sulphur (S) fertilisers to wheat in the first year and oilseed rape in the second year, using six agricultural soils. Four treatments were applied in the initial year: control (no S), two forms of elemental S (either micronised S° particles or a bentonite + S° mixture) and a sulphate fertiliser (ammonium sulphate). In the first year, the micronised S° was as effective as the sulphate fertiliser, both producing similar increases of wheat grain yield (on average 36%) and S uptake (on average 164%) over the control. In contrast, responses to the bentonite + S° form were minimal, indicating a limited S supply. In the second year the control treatment failed to produce seeds in most soils, whereas the micronised S° and sulphate treatments increased seed yields of oilseed rape to an average of 13.4 and 12.9 g pot-1, respectively. The performance of the bentonite + S° varied between soils: two soils produced yields similar to those of the other S fertilisers, while the remaining soils had low yields. To test whether the poor performance of the bentonite clay + S° fertiliser was due to the lack of exposure of the prills to physical weathering in the glasshouse, the effect of freeze-thaw action on the fertilisers performance was assessed in a separate pot experiment. The responses in wheat yield and S uptake showed that freeze-thaw did not enhance the physical disruption of the prills or fertiliser effectiveness. These results suggest that the release of available S from the bentonite + S° mixture was too slow to meet the requirement of wheat and oilseed rape.
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    The effects of irrigation regimes on the water use, dry matter production and physiological responses of paddy rice (2000)
    Springer
    Plant and soil 223 (2000), S. 209-218 
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    ISSN: 1573-5036
    Keywords: dry matter production ; irrigation water use ; leaf senescence ; paddy rice ; photosynthesis ; soil water potential
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In most cases, rice production is associated with flooding irrigation and the efficiency of irrigated water use (WUEi) is generally lower for production of rice than for other crops. We have examined the effects of various irrigation regimes on water consumption in a well-puddled paddy field, as well as on dry matter production, grain yield and physiological responses of the plants. Four sets of conditions were studied, with two replications, in the well-puddled paddy field: Continuous flooding irrigation treatment (CSF); three intermittent irrigation treatments, designated II-0, II-1 and II-2, in which plants were re-irrigated when the water potential of the soil fell below 0, –10, and –20 kPa at a depth of 5 cm, respectively. Water consumption was lower during II-0 than during CSF because the percolation rate was reduced by the reduction in the hydraulic head of the ponded water. Intermittent irrigation led to the repeated shrinking and swelling of soil during II-1 and II-2 and, therefore, soil cracks developed rapidly. Since they became the major routes of water percolation, these soil cracks increased water consumption during II-1 and II-2 above that during CSF and II-0. There were no significant differences in dry matter production and grain yield between CSF and II-0, but both were significantly greater than in the case of II-1 and II-2. Therefore, WUEi increased in the following order: II-0, CSF, II-2, II-1, although the difference was very small between II-1 and II-2. A lower crop growth rate (CGR) resulted from a decrease in the net assimilation rate (NAR) during II-1 and II-2, and there was also a reduction in the leaf area index (LAI) during II-2. Early senescence with ripening and water stress around midday decreased the rate of photosynthesis in leaves, causing the lower NAR. These physiological responses of the plants were responsible for the reduction on the dry matter production and grain yield in the intermittent irrigation.
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    Colonization of wheat by Azospirillum brasilense Cd is impaired by saline stress (2000)
    Springer
    Plant and soil 225 (2000), S. 187-191 
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    ISSN: 1573-5036
    Keywords: Azospirillum brasilense ; 2 ; 4-D ; para-nodules ; saline stress ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effect of saline stress on the colonization of wheat was analyzed by using Azospirillum brasilense Cd carrying the fusion of the reporter gene lacZ (β-galactosidase) with the N2 fixation gene promoter nifA. Colonization was also studied by inducing para-nodules on wheat roots using 2,4-D, establishing that these structures acted as bacterium protected niches. Bacteria grown under standard conditions were distributed along the whole root system, except the elongation zone, and colonized the para-nodules. Bacteria experiencing saline stress were mainly localized at the root tips and the lateral roots. In 2,4-D treated plants, most of the bacteria were present around the basal surface of the modified lateral root structures. Using the MPN method, there were not statistical differences between the numbers of control and stressed bacteria. As this method estimates endophytic colonization in contrast with the one using X-gal, which emphasizes colonization on the root surface, both procedures demonstrated to be necessary, concluding that salt treatment reduced surface colonization (X-gal) but not colonization inside the root. The bacterial counts made on inoculated wheat roots indicated higher numbers of both control and stressed bacteria in roots treated with 2,4-D compared with untreated roots.
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    Selenium accumulation by sequentially grown wheat and rice as influenced by gypsum application in a seleniferous soil (2000)
    Springer
    Plant and soil 227 (2000), S. 243-248 
    Details
    ISSN: 1573-5036
    Keywords: residual effect of gypsum ; rice ; selenium toxicity ; sulphur ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A field experiment was conducted for 2 years on an alkaline calcareous seleniferous soil to study the effect of different levels of gypsum (0.2 – 3.2 t ha−1) applied to wheat only in the first year on Se accumulation by wheat (Triticum aestivum L.) – rice (Oryza sativa L.) cropping sequence. With gypsum application, grain yield of both rice and wheat crops increased by 0.4 – 0.5 t ha−1; the increase in straw yield was 0.4 – 1.1 t ha−1. Significant reduction in Se accumulation by wheat was observed with gypsum application up to 0.8 t ha−1 and its residual effect was evident on the following crops for 2 years. Reduction in Se accumulation varied from 53 to 64% in wheat grain, 46 to 49% in wheat straw, 35 to 63% in rice grain and 36 to 51% in rice straw with an application of gypsum at 0.8 t ha−1. A corresponding increase in S concentration was observed. In the gypsum-treated plots, the ratio of S:Se increased by 6 – 8 times in wheat and 3 – 6 times in rice. Reduction in Se accumulation by crop plants through gypsum application may help in lowering the risk of Se over-exposure of animals and humans that depend on diet materials grown on high selenium soils.
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    Genetic control of aluminum tolerance in mutant lines of the wheat cultivar Anahuac (2000)
    Springer
    Euphytica 114 (2000), S. 47-53 
    Details
    ISSN: 1573-5060
    Keywords: aluminum tolerance ; genetic control ; induced mutations ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The behavior of 17 gamma irradiation mutant lines derived from the aluminum sensitive wheat cultivar `Anahuac' was compared with two sensitive and three tolerant cultivars in nutritent solutions containing seven Al3+ concentrations (0; 0.5; 1; 2; 4; 6 and10 mg/liter), at a temperature of 25 °C and 4.0 pH. Tolerance was measured by the continued growth of the primary roots in a solution without aluminum after 48 hours in a solution containing a known concentration of aluminum. 14 mutant lines were as tolerant to the presence of 10 mg/liter of Al3+ in the treatment solutions as were the tolerant `BH-1146', `IAC-60' and `IAC-24' cultivars. Two mutant lines were tolerant and one was sensitive to the presence of 1 mg/liter of Al3+, while the cultivars `Siete Cerros' and `Anahuac' were sensitive to 1 and 0.5 mg/liter Al3+ in the solutions, respectively. F2 seedlings, obtained from cross among one sensitive and twelve tolerant mutant lines to the sensitive cultivars (`Siete Cerros' or `Anahuac') and the tolerant cultivars (`BH-1146' or `IAC-24') were assessed for tolerance to 2 mg/liter Al3+ in nutritient solutions. The twelve tolerant mutant lines and the tolerant `IAC-60' and `IAC-24' cultivars differed from the sensitive `Siete Cerros' or `Anahuac' cultivars by one pair of dominant alleles. The results indicated that tolerance in the induced mutants was due to a single pair of dominant alleles and that these alleles expressed the same tolerance as `BH-1146' and `IAC-24' cultivars.
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    Detection of wheat-barley translocations by genomic in situ hybridization in derivatives of hybrids multiplied in vitro (2000)
    Springer
    Euphytica 112 (2000), S. 117-123 
    Details
    ISSN: 1573-5060
    Keywords: barley ; GISH ; in situ hybridization ; translocation ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Wheat-barley translocations were identified by genomicin situ hybridization (GISH) in backcross progenies originating from in vitro regenerated wheat (Triticum aestivum L. cv. Chinese Spring) × barley (Hordeum vulgare L. cv. Betzes) hybrids. The regenerated hybrids were pollinated with the wheat line Martonvásári 9 kr1. Five translocated wheat-barley chromosomes were recovered among 51 BC2F2 progeny from the in vitro regenerated wheat × barley hybrids. All were single breakpoint translocations with the relative positions of the breakpoints ranging from the centromere to about 0.8 of the relative arm length. Of the four translocations with intercalary breakpoints, three were transfers of terminal barley segments to wheat chromosomes; one was a transfer of a terminal wheat segment to a barley chromosome. Because of the absence of diagnostic N-bands, the identity of three barley segments could not be determined; in one translocation the barley chromosome involved had a NOR so it must have been 5H or 6H, and the centric translocation was 4HS.2BL. Following selfing, homozygotes of four translocations were selected. The experiment suggests that in vitro culture conditions are conducive for major genome rearrangements in wheat-barley hybrids.
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    Epicuticular waxes and regulation of ear wetting and pre-harvest sprouting in barley and wheat (2000)
    Springer
    Euphytica 112 (2000), S. 157-166 
    Details
    ISSN: 1573-5060
    Keywords: barley ; cer ; β-diketone ; glaucous ; pre-harvest sprouting ; waxes ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Morphological features of the cereal ear, including awns, alter pre-harvest sprouting damage by changing the rate of water absorption during rainfall. In this paper, the potential for wheat (Triticum sp.) arid barley (Hordeum vulgare L.) waxes to reduce sprouting by increasing water repellency of the mature ear has been examined. Six barley F2 populations segregating for different non-glaucous single-gene mutants controlling waxes on ears were examined. Water repellency was assessed by measuring both the contact angle of a water drop placed on the lemma surface (internal angle) and by repetitive weighings of whole ears during their exposure to simulated rainfall. The lemma of glaucous (wild type) lines had larger water drop contact angles, an indication of poorer spread of water over the surface. In simulated rainfall, ears of the glaucous lines showed a clear reduction of wetting (20–30% less) and, after 72 h of wetting, their in-ear sprouting was reduced by 50 to 65%. When pre-wet, the glaucous ears also shed water more readily when shaken to simulate the combined effect of wind and rainfall. To reduce pre-harvest sprouting of barley it may be possible to screen visually for ears that are more glaucous but a more specific screen would be to select for lemma water drop contact angle since it is a good indicator of ear wettability and so allows differences in surface properties to be assessed. For bread wheat (T. aestivumL.), as for barley, the more glaucous the ear, the greater the water drop contact angle and the more tubular surface wax coverage seen in scanning electron microscope images. In addition, surface wax amount apparently affected in-ear wettingin lines of durum wheat, (T. turgidum L.). Possible genetic relationships between waxy/waxless genes in wheat and barley are suggested with the aim, ultimately, of altering ear glaucousness to give increased water repellency and a reduction of in-ear sprouting of wheat.
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    Cross prediction in bread wheat germplasm using single seed descent lines (2000)
    Springer
    Euphytica 113 (2000), S. 65-70 
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    ISSN: 1573-5060
    Keywords: cross prediction ; grain yield ; recombinant inbred lines ; single seed descent ; wheat ; yellow rust
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Populations of F6 recombinant inbred lines, generated by single seed descent from a half diallel among eight bread wheat lines adapted to the East African highlands, were used to identify those crosses that were more likely to produce cultivars which combined resistance to yellow rust with improved yield. Crosses having the most resistant line as one parent offered the best prospect of success, particularly those which produced F1hybrids exhibiting better parent heterosis. For plot grain yield there was a highly significant correlation between the observed and predicted rankings of the recombinant inbred line populations for the proportion of individual lines equalling or surpassing the target value. For yellow rust severity, however, this correlation was non-significant when a target value of zero was used. Adopting a slightly less stringent target of 0.25, coupled with the omission of two aberrant populations, increased this correlation significantly. The plant breeding implications of these results are discussed.
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    URL: http://dx.doi.org/10.1023/A:1003985429998
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    Evaluation of grain yield and its components in wheat cultivars and landraces under near optimal and drought conditions (2000)
    Springer
    Euphytica 113 (2000), S. 43-52 
    Details
    ISSN: 1573-5060
    Keywords: cultivars ; drought stress ; droughtsusceptibility index ; landraces ; wheat ; yield
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In a 2-years experiment, 30 wheat cultivars and 21 landraces from different countries were tested under near optimum and drought stress conditions. Plant height, number of sterile spikelets per spike, spikelets per spike, number of kernels per spike, kernel weight per spike, 1000 kernel weight and grain yield were evaluated. The number of kernels per spike, 1000 kernel weight and especially yield were more sensitive to drought stress in the cultivars than plant height and number of spikelets per spike, while in the landraces these traits did not differ under drought stress compared to near optimum conditions. The average yield of cultivars was significantly better than the average yield of landraces under near optimum as well as drought stress conditions. Path coefficient analysis showed that for cultivars under near optimum conditions there was no significant direct association of any of the analysed characters with yield, while under drought stress conditions, number of kernels per spike had a significant positive direct effect. Under drought stress conditions, the number of sterile spikelets displayed a negative direct effect, while kernel weight per spike had a positive direct effect on yield. Hierarchical cluster analysis was used as a tool to classify cultivars and landraces according to their yield ability under near optimum and drought stress conditions. Among the cultivars, two groups out of five and among one of three in the landraces were characterised by high yields in both near optimum as well as under drought stress conditions. These genotypes may serve as sources of germplasm for breeding for drought tolerance.
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    URL: http://dx.doi.org/10.1023/A:1003997700865
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    Interaction effects of phosphorus and zinc on photosynthesis, growth and yield of dwarf bean grown in two environments (2000)
    Springer
    Plant and soil 220 (2000), S. 219-228 
    Details
    ISSN: 1573-5036
    Keywords: growth ; light intensity ; Phaseolus vulgaris L. ; phosphorus–zinc interaction ; photosynthesis ; yield ; zinc deficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Two experiments were conducted in a factorial combination of three Zn levels (0, 10 and 40 mg Zn kg-1 soil) and two P levels (0 and 200 mg P kg-1 soil). Experiment 1 was carried out during winter in a heated glasshouse, and experiment 2 during summer under a rain shelter. Plants of dwarf bean (Phaseolus vulgaris L., cv. Borlotto nano) were grown in pots filled with sandy soil. In both experiments, leaf Zn concentration was reduced by the addition of P to plants grown at low Zn supply. However, leaf Zn concentration lower than the critical level was observed only during experiment 2, and the main effects of low Zn were reductions of internode length, light use efficiency and maximum photosynthetic rate. In plants with leaf Zn concentration lower than the critical level, saturating irradiance levels fell from ∼1000 μmol m-2 s-1 PPFD to ∼300–400 μmol m-2 s-1 PPFD. Reduction of net photosynthesis was observed from the beginning of flowering and led to decreased seed production.
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    URL: http://dx.doi.org/10.1023/A:1004705008101
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    Comparative response of wheat and oilseed rape to nitrogen supply: absorption and utilisation efficiency of radiation and nitrogen during the reproductive stages determining yield (2000)
    Springer
    Plant and soil 220 (2000), S. 189-205 
    Details
    ISSN: 1573-5036
    Keywords: biomass ; intercepted radiation ; nitrogen nutrition ; oilseed rape ; radiation use efficiency ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract We investigated the response of spring wheat and oilseed rape to nitrogen (N) supply, focusing on the critical period for grain number definition and grain filling. Crops were grown in containers under a shelter and treated with five combinations of applied N. Wheat and oilseed rape produced comparable amounts of biomass and yield when corrected for the costs of biomass synthesis (SC). From the responses of biomass and yield to late N applications and the apparent contribution of mobilised biomass to yield, it seems that the yield of oilseed rape was more source-limited during grain filling than that of wheat, particularly at the medium and high N levels. Both species recovered equal amounts of N from the total available N in the soil and had similar N use efficiencies, expressed as yield per unit of N absorbed. However, oilseed rape had higher efficiency to convert absorbed N in biomass, but lower harvest index of N than wheat. Oilseed rape had similar or lower root biomass than wheat, depending on N level, but higher root length per unit soil volume and specific root length. The specific uptake rate of N per unit root dry weight during the critical period for grain number determination was higher in oilseed rape than in wheat. In wheat, N limitation affected growth through a similar or lower reduction in radiation use efficiency corrected for synthesis costs (RUESC) than in the cumulative amount of intercepted photosynthetically active radiation (IPARc). In oilseed rape, lower growth due to N shortage was associated more with RUESC than IPARc, during flowering while during grain filling both components contributed similarly to decreased growth. RUESC and the concentration of N in leaves and inflorescence (LIN%) decreased from flowering to maturity and were curvilinearly related. Oilseed rape tended to have higher RUESC than wheat at high N supply during the critical period for grain number determination, and generally lower during grain filling. The reasons for these differences and possibilities to increase yield potential are discussed in terms of the photosynthetic efficiency of the different organs and changes in source–sink ratio during reproductive stages.
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    URL: http://dx.doi.org/10.1023/A:1004757124939
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    Leaf water characteristics and drought acclimation in sunflower genotypes (2000)
    Springer
    Plant and soil 223 (2000), S. 155-162 
    Details
    ISSN: 1573-5036
    Keywords: drought acclimation ; Helianthus annuus L. ; photosynthesis ; pressure-volume curves ; water relations ; water stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The responses of leaf water parameters to drought were examined using three sunflower (Helianthus annuus L.) genotypes. Osmotic potential at full water saturation (π100), apoplastic water fraction (AWF) and bulk elastic modulus (BEM) were determined by pressure-volume curve analysis on well watered or on water-stressed plants (−1.0 MPa Ψ1 〈 −1.5 MPa) previously drought-pretreated or not. The drought-pretreated plants were subjected to a 7-day drought period (predawn leaf water potential reached −0.9 MPa) followed by 8 days of rewatering. In well watered plants, all genotypes in response to drought acclimation displayed a significantly decreased π100 associated with a decrease in the leaf water potential at the turgor-loss point (decrease in Ψtlp was between 0.15 and 0.21 MPa, depending on the genotype). In two genotypes, drought acclimation affected the partitioning of water between the apoplastic and symplastic fractions without any effect on the total amount of water in the leaves. As a third genotype displayed no modification of AWF and BEM after drought acclimation, the decreased π100 was only due to the net accumulation of solutes and was consistent with the adjustment of the photochemical efficiency observed previously in this genotype in response to drought acclimation. In water-stressed plants, the osmotic adjustment (OA) can increase further beyond that observed in response to the drought pretreatment. However, the maintenance of photosynthetic rate and stomatal conductance at low leaf water potentials not only depends on the extent of osmotic adjustment, but also on the interaction between OA and AWF or BEM. Adaptative responses of leaf water parameters to drought are thus quite contrasted in sunflower genotypes.
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    URL: http://dx.doi.org/10.1023/A:1004849509673
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    Photosynthesis, respiration, and carbon allocation of two cool-season perennial grasses in response to surface soil drying (2000)
    Springer
    Plant and soil 227 (2000), S. 17-26 
    Details
    ISSN: 1573-5036
    Keywords: photosynthesis ; root respiration ; carbon allocation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The study was conducted to investigate carbon metabolic responses to surface soil drying for cool-season grasses. Kentucky bluegrass (Poa pratensis L.) and tall fescue (Festuca arundinaceae Schreb.) were grown in a greenhouse in split tubes consisting of two sections. Plants were subjected to three soil moisture regimes: (1) well-watered control; (2) drying of upper 20-cm soil (upper drying); and (3) drying of whole 40-cm soil profile (full drying). Upper drying for 30 d had no dramatic effects on leaf water potential (Ψleaf) and canopy photosynthetic rate (Pn) in either grass species compared to the well-watered control, but it reduced canopy respiration rate (Rcanopy) and root respiration rate in the top 20 cm of soil (Rtop). For both species in the lower 20 cm of wet soil, root respiration rates (Rbottom) were similar to the control levels, and carbon allocation to roots increased with the upper soil drying, particularly for tall fescue. The proportion of roots decreased in the 0-20 cm drying soil, but increased in the lower 20 cm wet soil for both grass species; the increase was greater for tall fescue. The Ψleaf, Pn, Rcanopy, Rtop, Rbottom, and carbon allocation to roots in both soil layers were all significantly higher for upper dried plants than for fully dried plants of both grass species. The reductions in Rcanopy and Rtop in surface drying soil and increases in root respiration and carbon allocation to roots in lower wet soil could help these grasses cope with surface-soil drought stress.
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    URL: http://dx.doi.org/10.1023/A:1026512212113
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    Response of tomato plants to chilling stress in association with nutrient or phosphorus starvation (2000)
    Springer
    Plant and soil 226 (2000), S. 99-106 
    Details
    ISSN: 1573-5036
    Keywords: chilling ; chlorophyll fluorescence ; nutrient ; phosphorus ; photosynthesis ; starvation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The experiments were conducted on two tomato cultivars: Garbo and Robin. Mineral starvation due to plant growth in 20-fold diluted nutrient solution (DNS) combined with chilling reduced the rate of photosynthesis (P N) and stomatal conductance (g) to a greater extent than in plants grown in full nutrient solution (FNS). In phosphate-starved tomato plants the P N rate and stomatal conductance decreased more after chilling than in plants grown on FNS. In low-P plants even 2 days after chilling the recovery of CO2 assimilation rate and stomatal conductance was low. A resupply of phosphorus to low-P plants (low P + P) did not improve the rate of photosynthesis in non-chilled plants (NCh) but prevented PN inhibition in chilled (Ch) plants. The greatest effect of P resupply was expressed as a better recovery of photosynthesis and stomatal conductance, especially in non-chilled low P + P plants. The F v/F m (ratio of variable to maximal chlorophyll fluorescence) decreased more during P starvation than as an effect of chilling. Supplying phosphorus to low-P plants caused the slight increase in the F v/F mratio. In conclusion, after a short-term chilling in darkness a much more drastic inhibition of photosynthesis was observed in nutrient-starved or P-insufficient tomato plants than in plants from FNS. This inhibition was caused by the decrease in both photochemical efficiency of photosystems and the reduction of stomatal conductance. The presented results support the hypothesis that tomato plants with limited supply of mineral nutrients or phosphorus are more susceptible to chilling.
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    URL: http://dx.doi.org/10.1023/A:1026497104077
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    Improvement of resistance to Fusarium head blight by recurrent selection in an intermating breeding spring wheat population using the dominant male-sterile gene ms 2 (2000)
    Springer
    Euphytica 112 (2000), S. 79-88 
    Details
    ISSN: 1573-5060
    Keywords: Fusarium head blight ; intermating breedingpopulation ; male-sterile gene ms 2 ; recurrent selection ; resistance ; Triticum aestivum L. ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Four cycles of recurrent selection for FHB resistance were conducted in an intermating wheat breeding population using the dominant male-sterile gene ms 2 during 1987–1991.Five cycles of phenotypic mass selection for male-sterile plants were evaluated using the soil-surface inoculation method in Experiment I. Experiment II evaluated changes in FHB scores during five cycles of progeny selection for fertile plants using the single-floret inoculation method. In Experiment I, the average level of FHB response increased to MR level in C4, compared to MS level in C0. The numbers of infected spikelets and diseased kernels decreased 0.32 and 2.68 per cycle, respectively. In Experiment II, the average level of FHB response increased to R level in C4F1. The numbers of infected spikelets and diseased kernels decreased 0.93 and 4.58 per cycle, respectively. In both experiments, the largest selection gains were realized in the first cycle. The frequencies of R and MR individuals were increased significantly. The frequencies of individuals with FHB response equal and/or superior to Sumai 3 were increased to 5–8% in C4 and 25% in C4F1after the fourth cycle. Agronomic traits tended to be slightly improved in selected populations. Compared to 2% in C0, about 34% of lines superior in both FHB resistance and agronomic traits in C4F1 were selected to enter the conventional breeding program for further evaluation. Sixty three semidwarf lines superior in both FHB resistance and yield potential were selected from the F5 generations derived from C1F1 to C4F1. From them, two resistant cultivars with high-yielding potential were developed and commercialized in the Lower Yangtze Valley. Recurrent selection appears to be highly effective and feasible in shifting the average FHB response of the intermating population in the desirable direction, thereby enhancing the frequency of resistant individuals.
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    URL: http://dx.doi.org/10.1023/A:1003850123088
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    The inheritance and expression of grain texture in wheat, as measured by a microtome procedure (2000)
    Springer
    Euphytica 112 (2000), S. 261-265 
    Details
    ISSN: 1573-5060
    Keywords: grain texture ; microtome ; quality ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Although grain texture has been extensively studied, there is still some controversy about its mode of inheritance. The aim of this study was to use a microtome method to determine the inheritance of grain texture. The backcross method was used with a hard, well adapted cultivar, M29519 as recurrent parent, and Edwall, a soft cultivar with good biscuit-making quality, as donor. Segregation ratio's for grain texture were calculated after each backcross. The backcross derivates M29519 (soft) and M29519 (hard) and the donor and recurrent parents were also compared for biscuit-making quality. The microtome method was found to be very effective to determine grain texture. In this study grain softness was determined by a single dominant gene. M29519 (hard) and the recurrent parent did not differ significantly for any quality characteristics. M29519 (hard) and M29519 (soft) differed significantly for seven characteristics associated with biscuit-making quality, and M29519 (soft) produced a significantly larger biscuit diameter than M29519 (hard). M29519 (soft) differed significantly from the donor parent for six of the measured characteristics. Despite this, M29519 (soft) produced a biscuit similar in diameter to that of the donor parent. Therefore, although the transfer of the softness genes into a different genetic background did not transfer all the factors generally associated with good biscuit-making quality, it did produce a biscuit that did not differ significantly from that of the donor.
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    URL: http://dx.doi.org/10.1023/A:1003908707708
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    Recurrent selection in oat for adaptation to diverse environments (2000)
    Springer
    Euphytica 113 (2000), S. 195-205 
    Details
    ISSN: 1573-5060
    Keywords: Avena ; genetic correlation ; genotype-environmentinteraction ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In order to test if selection can improve a population's adaptation to diverse environments simultaneously, three cycles of recurrent selection based on grain yield in Iowa, Idaho, and Norway were practiced in an oat (Avena sativaL.) population developed from North American, Scandinavian, and wild species (A. sterilis L.) germplasm sources. Specific objectives were to determine if selection: increased mean yields across environments and within all environments; changed the genetic correlation of yields in different environments; and changed genetic variation for yield within the population. We evaluated 100 to 210 randomly-chosen families from each cycle of selection at three Iowa locations, in Idaho, and in Norway for two years. Grain yield within each location and mean yields across locations increased significantly over cycles of selection. Mean yields across locations expressed as a percent of the original population mean increased at a rate of 2.6% per year. Several families from the third cycle population exhibited both high mean yields across locations and consistently high yields within all locations. Average genetic correlations of yield in different environments were higher in the second cycle than in the original population. A trend of reduced genetic variation and heritability was observed in Iowa only. These results suggest that we successfully improved mean population yield both within and across locations, and yield stability across environments, and in developing families with outstanding adaptation to diverse environments.
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    URL: http://dx.doi.org/10.1023/A:1003933421378
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    Resistance to septoria nodorum blotch in the Aegilops tauschii accession RL5271 is controlled by a single gene (2000)
    Springer
    Euphytica 113 (2000), S. 227-231 
    Details
    ISSN: 1573-5060
    Keywords: disease resistance ; incubation period ; infection frequency ; Stagonospora nodorum ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Septoria nodorum blotch is the most important leaf disease of wheat in Western Australia. A potentially useful source of resistance has been identified in an accession of Aegilops tauschii. To study the genetics of resistance of this source a cross was made between the resistant Ae. tauschii accession, RL5271, and a susceptible accession, CPI110889. The resistant parent took significantly longer to develop symptoms, developed significantly fewer lesions and expressed significantly lower levels of disease than the susceptible parent. The F1 mean response for disease severity indicated there was no complete dominance. The F3 families were classified using three approaches. In the first approach the individual F3 plant response was used to classify the F3 families. In the second approach the F3 family means and standard errors were used to classify the F3 families. In the final approach Best Linear Unbiased Predictors of disease score and standard error for each F3 family derived from a REML analysis were used to classify the F3 families. The genotypic ratios generated by each of the approaches suggested that resistance is controlled by a single gene. The effectiveness of the resistance and its simple genetic control in the Ae. tauschii, accession RL5271 may be a useful resistance source for use in a bread wheat breeding program.
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    URL: http://dx.doi.org/10.1023/A:1003981525052
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    Isolation of mildew resistant wheat-rye translocation lines from a double substitution line (2000)
    Springer
    Euphytica 115 (2000), S. 167-172 
    Details
    ISSN: 1573-5060
    Keywords: alien genetic variation ; chromosome translocation ; powdery mildew ; resistance ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A powdery mildew resistant double disomic wheat-rye substitution line carrying rye chromosomes 1R and 2R was crossed with normal bread wheats. The F2 generation was analysed cytologically by C-banding. Wheat-rye chromosome translocations involving both rye chromosomes 1R and 2R were frequent in F2. Lines with translocations of 1R and 2R were harvested separately. After four generations of selfing and selection for mildew resistance and fertility, fully fertile resistant lines were selected and analysed cytologically. Lines with 1BL/1RS and 2BS/2RL translocations were identified. The resistance on chromosome 1RS could not be shown to be different from control varieties carrying the same rye segment, while the resistance on 2RL is much broader than the earlier known 2RL derived resistance in the line Transec.
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    URL: http://dx.doi.org/10.1023/A:1004018500970
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    Tolerance of a field grown soybean cultivar to elevated ozone level is concurrent with higher leaflet ascorbic acid level, higher ascorbate-dehydroascorbate redox status, and long term photosynthetic productivity (2000)
    Springer
    Photosynthesis research 64 (2000), S. 77-87 
    Details
    ISSN: 1573-5079
    Keywords: ascorbic acid ; ascorbate-glutathione cycle ; bean yield ; dehydroascorbate ; ozone ; photosynthesis ; soybean ; vegetative yield
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We examined the characteristics of ascorbic acid (ASC) level, dehydroascorbate (DHA) level, and the ASC–DHA redox status in the leaflets of two soybean cultivars grown in a field environment and exposed to elevated ozone (O3) levels. These two cultivars, one that preliminary evidence indicated to be O3-tolerant (cv Essex), and one that was indicated to be O3-sensitive (cv Forrest), were grown in open-top chambers during the summer of 1997. The plants were exposed daily to a controlled, moderately high O3 level (≈58 nl l−1 air) in the light, beginning at the seedling stage and continuing to bean maturity. Concurrently, control plants were exposed to carbon-filtered, ambient air containing a relatively low O3 level (≈24 nl l−1 air) during the same period. Elevated O3 did not affect biomass per plant, mature leaf area accretion, or bean yield per plant of cv Essex. In contrast, elevated O3 level decreased the biomass and bean yield per plant of cv Forrest by approximately 20%. Daily leaflet photosynthesis rate and stomatal conductance per unit area did not decrease in either cultivar as a result of prolonged O3 exposure. A 10% lower mature leaflet area in O3-treated cv Forrest plants contributed to an ultimate limitation in long-term photosynthetic productivity (vegetative and bean yield). Possible factors causing cv Essex to be more O3 tolerant than cv Forrest were: 1) mature leaflets of control and O3-treated cv Essex plants consistently maintained a higher daily ASC level than leaflets of cv Forrest plants, and 2) mature leaflets of cv Essex plants maintained a higher daily ASC–DHA redox status than leaflets of cv Forrest plants.
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    URL: http://dx.doi.org/10.1023/A:1026508227189
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    Crystallization of dimers of the manganese-stabilizing protein of Photosystem II (2000)
    Springer
    Photosynthesis research 64 (2000), S. 167-177 
    Details
    ISSN: 1573-5079
    Keywords: dynamic light scattering ; mass spectrometry ; oxygen evolution ; photosynthesis ; protein crystallization ; protein structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The manganese-stabilizing protein (MSP) of Photosystem II was purified from spinach photosynthetic membranes. The MSP was crystallized in the presence of calcium. Despite the apparent purity of the isolated protein, the crystals grew to only about 0.05 mm in their largest dimension. The MSP was analyzed to identify possible sources of protein heterogeneity that could hinder crystal growth. Tandem reverse-phase HPLC/ electronspray ionization mass spectrometry analysis of the MSP showed a major peak and four smaller peaks. All five peaks had molecular masses of 26 535, as expected for mature MSP, indicating the absence of heterogeneities due to covalent modifications. MALDI mass spectroscopy was utilized to identify heterogeneities in the MSP oligomeric state. These measurements showed that purified MSP in solution is a mixture of monomers and dimers, while solubilized MSP crystals contained only dimers. Size-exclusion chromatography and dynamic light scattering were used to probe the effect of the crystallization conditions on the MSP. Size-exclusion chromatography of concentrated MSP showed the presence of aggregates and monomers, while dilute MSP contained monomers. Dynamic light scattering experiments in the absence, or in the presence of 10–50 mM or 100 mM calcium, yielded calculated molecular mass values of 34 kDa, 48 kDa and 68 kDa, respectively. These changes in the observed molecular mass of the MSP could have been caused by the formation of dimers and higher oligomers and/or significant conformational changes. Based on the results reported in this study, a model is presented which details the effect of oligomeric heterogeneity on the inhibition of MSP crystal growth.
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    URL: http://dx.doi.org/10.1023/A:1006453718502
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    Analysis of the role of detergent mixtures on the crystallization of the reaction center of Photosystem II (2000)
    Springer
    Photosynthesis research 65 (2000), S. 249-259 
    Details
    ISSN: 1573-5079
    Keywords: dynamic light scattering ; membrane protein crystallization ; photosynthesis ; thermoluminescence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have recently reported the crystallization of the reaction center of Photosystem II in the presence of detergent mixtures [Adir N (1999) Acta Crystallogr D Biol Crystallogr D55: 891–894]. We have used high performance liquid chromatography, dynamic light scattering, native gel electrophoresis and thermoluminescence measurements to characterize the interaction between these detergent mixtures and RC II, to try and understand their role in the crystallization process. Size exclusion HPLC and dynamic light scattering confirmed that the isolated RC II used for crystallization was exclusively monomeric. Dynamic light scattering measurements show that the detergent mixtures formed single micelles within a limited range of hydrodynamic radii. Both size exclusion HPLC and dynamic light scattering were used to follow the interaction between the detergent mixtures and monomeric RC II. These techniques revealed a decrease in the detergent mixture treated RC II particle size (with respect with the untreated RC II), and that RC II from solubilized crystals contained particles of the same size. Native gel electrophoresis showed that this change in apparent size is not due to the disintegration of the internal structure of the RC II complex. Thermoluminescence measurements of solubilized RC II crystals showed charge recombination from the S2,3QA − state, indicating that RC II remains functionally viable following detergent mixture treatment and crystallization. The role of the detergent mixtures in the crystallization of RC II is discussed.
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    URL: http://dx.doi.org/10.1023/A:1010618527974
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    Kinetic imaging of chlorophyll fluorescence using modulated light (2000)
    Springer
    Photosynthesis research 66 (2000), S. 3-12 
    Details
    ISSN: 1573-5079
    Keywords: herbicide ; instrumentation ; mutant selection ; photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Fluorometers that measure the kinetics of chlorophyll fluorescence have become invaluable tools for determining the photosynthetic performance of plants. Many of these instruments use high frequency modulated light to measure the rate, efficiency and regulation of photosynthesis. The technique is non-invasive and is effective under diverse environmental conditions. Recently, imaging fluorometers have been introduced that reveal variability in photosynthesis over the surface of a leaf or between individual plants. Most imaging instruments depend on continuous light or low frequency modulated light for fluorescence excitation, which imposes serious limitations on measurements of the fluorescence parameters, especially the minimum fluorescence (F0) and variable fluorescence (FV). Here, we describe a new instrument that combines the advantage of high frequency modulated light with two-dimensional imaging of chlorophyll fluorescence. The fluorometer produces dynamic images of chlorophyll fluorescence from leaves or plants, providing accurate mapping of F0 and FV, and non-photochemical quenching. A significant feature of the instrument is that it can record fluorescence images of leaves in daylight under field conditions.
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    URL: http://dx.doi.org/10.1023/A:1010729821876
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    Airborne test of laser pump-and-probe technique for assessment of phytoplankton photochemical characteristics (2000)
    Springer
    Photosynthesis research 66 (2000), S. 45-56 
    Details
    ISSN: 1573-5079
    Keywords: chlorophyll ; energy quenching ; fluorescence ; LIDAR ; photochemistry ; photosynthesis ; Photosystem II ; phytoplankton ; pump and probe ; remote sensing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Initial results of the airborne LIDAR measurement of photochemical quantum yield, ΦPo, and functional absorption cross-section, σPS II, of Photosystem II (PS II) are reported. NASA's AOL3 LIDAR was modified to implement short-pulse pump-and-probe (SP-P&P) LIDAR measurement protocol. The prototype system is capable of measuring a pump-induced increase in probe-stimulated chlorophyll fluorescence, ΔF/Fsat, along with the acquisition of `conventional' LIDAR-fluorosensor products from an operational altitude of 150 m. The use of a PS II sub-saturating probe pulse increases the response signal but also results in excessive energy quenching (EEQ) affecting the ΔF/Fsat magnitude. The airborne data indicated up to a 3-fold EEQ-caused decline in ΔF/Fsat, and 2-fold variability in the EEQ rate constant over a spatial scale a few hundred kilometers. Therefore, continuous monitoring of EEQ parameters must be incorporated in the operational SP-P&P protocol to provide data correction for the EEQ effect. Simultaneous airborne LIDAR measurements of ΦPo and σPS II with EEQ correction were shown to be feasible and optimal laser excitation parameters were determined. Strong daytime ΔF/Fsat decline under ambient light was found in the near-surface water layer over large aquatic areas. An example of SP-P&P LIDAR measurement of phytoplankton photochemical and fluorescent characteristics in the Chesapeake Bay mouth is presented. Prospects for future SP-P&P development and related problems are discussed.
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    URL: http://dx.doi.org/10.1023/A:1010764420934
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    Carbohydrate regulation of leaf development: Prolongation of leaf senescence in Rubisco antisense mutants of tobacco (2000)
    Springer
    Photosynthesis research 63 (2000), S. 1-8 
    Details
    ISSN: 1573-5079
    Keywords: acclimation ; photosynthesis ; rbcL ; rbcS ; source strength
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Previous investigations have shown that increased source strength as a result of elevated CO2 can alter the timing of the phases of change that occur in photosynthetic rates during dicot leaf ontogeny [Miller et al. (1997) Plant Physiol 115: 1195–1200]. To evaluate the converse situation of decreased source strength, we examined leaf development in rbcS antisense mutants of tobacco. These mutants have depressed Rubisco levels and decreased rates of carbohydrate production. We found that antisense leaves are longer-lived than wild type leaves and that this appeared to be due to a prolongation of the senescence phase of development, as monitored by photosynthetic rates, chlorophyll content, and the abundance and activity of Rubisco. Declines in these parameters during leaf ontogeny in both the wild type and mutant plants were generally accompanied by coordinate reductions in the levels of rbcS mRNA and rbcL mRNA, as well as by reductions in chloroplast rRNA, chloroplast DNA and total protein. We suggest that the prolongation of senescence in the antisense leaves is due to an impact of source strength on leaf developmental programming that occurs, at least in part, at the level of transcript abundance of nuclear and chloroplast genes for chloroplast rRNAs and proteins. We hypothesize that plants are capable of sensing a range of source strength conditions to initiate and modulate leaf developmental programming.
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    URL: http://dx.doi.org/10.1023/A:1006367719639
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    An FTIR study on the structure of the oxygen-evolving Mn-cluster of Photosystem II in different spin forms of the S2 state (2000)
    Springer
    Photosynthesis research 63 (2000), S. 47-57 
    Details
    ISSN: 1573-5079
    Keywords: Fourier transform infrared spectroscopy ; Mn-cluster ; oxygen evolution ; photosynthesis ; Photosystem II ; vibrational spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The S2 state of the oxygen-evolving Mn-cluster of Photosystem II (PS II) is known to have different forms that exhibit the g =2 multiline and g = 4.1 EPR signals. These two spin forms are interconvertible at 〉 200 K and the relative amplitudes of the two signals are dependent on the species of cryoprotectant and alcohol contained in the medium. Also, it was recently found that the mutiline form can be converted to the g = 4.1 form by absorption of near-infrared light by the Mn-cluster itself at around 150 K [Boussac et al. (1996) Biochemistry 35: 6984–6989]. We have used light-induced Fourier transform infrared (FTIR) difference spectroscopy to study the structural difference in these two S2 forms. FTIR difference spectra for S2/S1 as well as for S2QA -/S1QA measured at cryogenic temperatures using PS II membranes in the presence of various cryoprotectants, and monohydric alcohols did not show any specific differences except for intensities of amide I bands, which were larger when ethylene glycol or glycerol was present in addition to sucrose. This result was interpreted due to more flexible movement of the protein backbones upon S2 formation with a higher cryoprotectant content. Light-induced difference spectra measured at 150 K using either blue light without near-infrared light or red plus near-infrared light also did not show any detectable difference. In addition, a different spectrum upon near-infrared illumination at 150 K of the PS II sample in which the S2 state had been photogenerated at 200 K exhibited no meaningful signals. These results indicate that the two S2 forms that give rise to the multiline and g = 4.1 signals have only minor differences, if any, in the structures of amino-acid ligands and polypeptide backbones. This conclusion suggests that conversion between the two spin states is caused by a spin-state transition in the Mn(III) ion rather than valence swapping within the Mn-cluster that would considerably affect the vibrations of ligands.
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    URL: http://dx.doi.org/10.1023/A:1006362118267
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    Accumulation and leakage of abscisic acid during embryo development and seed dormancy in wheat (2000)
    Springer
    Plant growth regulation 30 (2000), S. 253-260 
    Details
    ISSN: 1573-5087
    Keywords: abscisic acid (ABA) ; dormancy ; mature germination ; seed ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Seed dormancy develops latein embryogenesis after a period of potential prematuregermination and has been associated with levels ofabscisic acid (ABA) in, and sensitivity to, ABA ofembryos. In wheat (Triticum aestivum L.)embryos, there are two peaks in levels of ABA duringdevelopment: the first occurs 25 days afterpollination (DAP) and the second from 35 to 40 DAP. The first peak of ABA appears to be associated withthe development of the embryo's sensitivity to ABAsince such sensitivity was altered in seeds on earsthat were incubated in a solution of ABA from 15 and20 DAP. In the embryos of Kitakei wheat, a line thatexhibits dormancy, the second peak, at around 35 DAP,was more prolonged in comparison to Chihoku, anon-dormant line. The results support the proposedinvolvement of ABA in the formation and maintenance ofseed dormancy during middle and late embryogenesis. When developing embryos were incubated in water,embryonic ABA leaked out from the embryos, inparticular between 30 and 40 DAP. Prematuregermination observed between 30 and 40 DAP might berelated to such leakage of ABA from embryos.
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    URL: http://dx.doi.org/10.1023/A:1006320614530
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    Morphoagronomic and biochemical variation in an Argentinean landrace of wheat (2000)
    Springer
    Genetic resources and crop evolution 47 (2000), S. 281-284 
    Details
    ISSN: 1573-5109
    Keywords: agronomic traits ; isozymes ; landrace ; Triticum aestivum ; variation ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A sample of an Argentinean landrace of wheat showed considerable variation in most of the evaluated morphological and agronomic characters. However, analyses with high molecular glutenins and two isozyme systems, known to be highly polymorphic among current cultivars, revealed very little or no variation, respectively. The large difference in the observed variation between morphoagronomic and biochemical characters is discussed.
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    URL: http://dx.doi.org/10.1023/A:1008711903949
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    New applications of photoacoustics to the study of photosynthesis (2000)
    Springer
    Photosynthesis research 66 (2000), S. 13-31 
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    ISSN: 1573-5079
    Keywords: photosynthesis ; photoacoustic ; optoacoustic ; spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Photoacoustic methods offer unique capabilities for photosynthesis research. Phenomena that are readily observed by photoacoustics include the storage of energy by electron transport, oxygen evolution by leaf tissue at microsecond time resolution, and the conformational changes of photosystems caused by charge separation. Despite these capabilities, photoacoustic methods have not been widely exploited in photosynthesis research. One factor that has contributed to their slow adoption is uncertainty in the interpretation of photoacoustic signals. Careful experimentation is resolving this uncertainty, however, and technical refinements of photoacoustic methods continue to be made. This review provides an overview of the application of photoacoustics to the study of photosynthesis with an emphasis on the resolution of uncertainties in the interpretation of photoacoustic signals. Recent developments in photoacoustic technology are also presented, including a microphotoacoustic spectrometer, gas permeable photoacoustic cells, the use of photoacoustics to monitor phytoplankton populations, and the use of photoacoustics to study protein dynamics.
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    URL: http://dx.doi.org/10.1023/A:1010788504886
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    Short-pulse pump-and-probe technique for airborne laser assessment of Photosystem II photochemical characteristics (2000)
    Springer
    Photosynthesis research 66 (2000), S. 33-44 
    Details
    ISSN: 1573-5079
    Keywords: chlorophyll ; fluorescence ; LIDAR ; photosynthesis ; Photosystem II ; pump and probe ; remote sensing ; singlet-singlet quenching ; singlet-triplet quenching
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The development of a technique for laser measurement of fPhotosystem II (PS II) photochemical characteristics of phytoplankton and terrestrial vegetation from an airborne platform is described. Results of theoretical analysis and experimental study of pump-and-probe measurement of the PS II functional absorption cross-section and photochemical quantum yield are presented. The use of 10 ns probe pulses of PS II sub-saturating intensity provides a significant, up to 150-fold, increase in the fluorescence signal compared to conventional `weak-probe' protocol. Little effect on the fluorescence yield from the probe-induced closure of PS II reaction centers is expected over the short pulse duration, and thus a relatively intense probe pulse can be used. On the other hand, a correction must be made for the probe-induced carotenoid triplet quenching and singlet-singlet annihilation. A Stern-Volmer model developed for this correction assumes a linear dependence of the quenching rate on the laser pulse fluence, which was experimentally validated. The PS II saturating pump pulse fluence (532 nm excitation) was found to be 10 and 40 μmol quanta m−2 for phytoplankton samples and leaves of higher plants, respectively. Thirty μs was determined as the optimal delay in the pump-probe pair. Our results indicate that the short-pulse pump-and-probe measurement of PS II photochemical characteristics can be implemented from an airborne platform using existing laser and LIDAR technologies.
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    URL: http://dx.doi.org/10.1023/A:1010795820025
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    Acclimation response of spring wheat in a free-air CO2 enrichment (FACE) atmosphere with variable soil nitrogen regimes. 2. Net assimilation and stomatal conductance of leaves (2000)
    Springer
    Photosynthesis research 66 (2000), S. 79-95 
    Details
    ISSN: 1573-5079
    Keywords: acclimation ; climate change ; CO2 ; down-regulation ; global change ; photosynthesis ; stomatal conductance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Atmospheric CO2 concentration continues to rise. It is important, therefore, to determine what acclimatory changes will occur within the photosynthetic apparatus of wheat (Triticum aestivum L. cv. Yecora Rojo) grown in a future high-CO2 world at ample and limited soil N contents. Wheat was grown in an open field exposed to the CO2 concentration of ambient air [370 μmol (CO2) mol−1; Control] and air enriched to ∼200 μmol (CO2) mol−1 above ambient using a Free-Air CO2 Enrichment (FACE) apparatus (main plot). A High (35 g m−2) or Low (7 and 1.5 g m−2 for 1996 and 1997, respectfully) level of N was applied to each half of the main CO2 treatment plots (split-plot). Under High-N, FACE reduced stomatal conductance (g s) by 30% at mid-morning (2 h prior to solar noon), 36% at midday (solar noon) and 27% at mid-afternoon (2.5 h after solar noon), whereas under Low-N, g s was reduced by as much as 31% at mid-morning, 44% at midday and 28% at mid-afternoon compared with Control. But, no significant CO2 × N interaction effects occurred. Across seasons and growth stages, daily accumulation of carbon (A′) was 27% greater in FACE than Control. High-N increased A′ by 18% compared with Low-N. In contrast to results for g s, however, significant CO2 × N interaction effects occurred because FACE increased A′ by 30% at High-N, but by only 23% at Low-N. FACE enhanced the seasonal accumulation of carbon (A′′) by 29% during 1996 (moderate N-stress), but by only 21% during 1997 (severe N-stress). These results support the premise that in a future high-CO2 world an acclimatory (down-regulation) response in the photosynthetic apparatus of field-grown wheat is anticipated. They also demonstrate, however, that the stimulatory effect of a rise in atmospheric CO2 on carbon gain in wheat can be maintained if nutrients such as nitrogen are in ample supply.
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    URL: http://dx.doi.org/10.1023/A:1010646225929
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    Respiration and plasma membrane ATPase in strawberry stolons (2000)
    Springer
    Plant growth regulation 30 (2000), S. 163-170 
    Details
    ISSN: 1573-5087
    Keywords: ATPase ; bioenergetics ; Fragaria ananassa Duch ; growth ; ion transport ; photosynthesis ; proton transport ; respiration ; source-sink ; strawberry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The biochemical, physiological and anatomical properties of strawberry (Fragaria ananassa Duch.) cv. 'Cambridge Favourite' stolons were studied during growth. ATPase activity was measured, in microsomal and plasma membrane fractions, along with chlorophyll determination, in-situ photosynthesis measurements and scanning electron microscopy (SEM) and X-ray microanalysis of stolon cross-sections. Potassium-stimulated ATPase activity and proton-pumping, both together indicating the presence of plasma membrane ATPase, was greatest in the stolon tip, the tissue with the fastest growth and respiratory activity. The enzyme activity and respiration gradient from the tip of the stolon to the base was concomitant with xylem development which was more differentiated in the base than in the tip. These cross-sections also showed 30% greater amounts of calcium and potassium of the cryo-preserved basal part relative to the stolon tip. This gradient existed independent of the presence of daughter plants. A hypothesis is presented which suggests that for the long-distance longitudinal transport of nutrients this gradient between stolon tip and base is likely to be involved in stolon growth.
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    URL: http://dx.doi.org/10.1023/A:1006314629955
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    Chlorophyll fluorescence transients of Photosystem II membrane particles as a tool for studying photosynthetic oxygen evolution (2000)
    Springer
    Photosynthesis research 65 (2000), S. 41-52 
    Details
    ISSN: 1573-5079
    Keywords: chlorophyll fluorescence ; EPR ; heat effect ; manganese complex ; oxygen-evolution ; photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The rise of the chlorophyll fluorescence yield of Photosystem II (PS II) membranes as induced by high-intensity actinic light comprises only two distinct phases: (1) the initial O-J increase and (2) the subsequent J-P increase. Partial inhibition of the PS II donor side by heating or washing procedures which remove peripheral PS II proteins or cofactors of the oxygen-evolving complex results in decrease of magnitude and rate of the J-P phase. The rate constant of the J-P increase is directly proportional to the steady-state rate of oxygen evolution; complete suppression of the J-P phase corresponds to full inhibition. A characteristic dip after J-level is observed only in Tris-washed or severely heated PS II membranes; manganese release correlates with appearance of the dip after J-level as verified by EPR spectroscopy. Presence of stabilizing cosolutes (glycine betaine, sucrose) or addition of donor-side cofactors (bicarbonate, chloride, calcium) to PS II membranes before heating (47 °C, 5 min) diminishes J-P phase suppression and prevents dip appearance, whereas the addition after heating is without effect. In conclusion, analysis of chlorophyll fluorescence transients of PS II membranes is a potentially useful tool for investigations on photosynthetic oxygen evolution. A decreased rate of the J-P phase can be employed as a convenient indicator for partial inhibition of oxygen-evolution activity; the appearance of a dip after J-level is suggestive of manganese release.
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    URL: http://dx.doi.org/10.1023/A:1006469809812
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    The effect of CO2 enrichment on leaf photosynthetic rates and instantaneous water use efficiency of Andropogon gerardii in the tallgrass prairie (2000)
    Springer
    Photosynthesis research 65 (2000), S. 121-129 
    Details
    ISSN: 1573-5079
    Keywords: big bluestem ; C4 ; elevated CO2 ; photosynthesis ; water use efficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Open-top chambers were used to study the effects of CO2 enrichment on leaf-level photosynthetic rates of the C4 grass Andropogon gerardii in the native tallgrass prairie ecosystem near Manhattan, Kansas. Measurements were made during a year with abundant rainfall (1993) and a year with below-normal rainfall (1994). Treatments included: No chamber, ambient CO2 (A); chamber with ambient CO2 (CA); and chamber with twice-ambient CO2 (CE). Measurements of photosynthesis were made at 2-hour intervals, or at midday, on cloudless days throughout the growing season using an open-flow gas-exchange system. No significant differences in midday rates of photosynthesis or in daily carbon accumulation as a result of CO2 enrichment were found in the year with abundant precipitation. In the dry year, midday rates of photosynthesis were significantly higher in the CE treatment than in the CA or A treatments throughout the season. Estimates of daily carbon accumulation also indicated that CO2 enrichment allowed plants to maximize carbon acquisition on a diurnal basis. The increased carbon accumulation was accounted for by greater rates of photosynthesis in the CE plots during midday. During the wet year, CO2 enrichment decreased stomatal conductance, which allowed plants to decrease transpiration while still photosynthesizing at rates similar to plants in ambient conditions. During the dry year, CO2 enrichment allowed plants to maintain photosynthetic rates even though stomatal conductance and transpiration had been reduced in all treatments due to stress. Estimates of instantaneous water-use efficiency were reduced under CO2 enrichment for both years.
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    URL: http://dx.doi.org/10.1023/A:1006489919192
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    Nitrogen ligation to the manganese cluster of Photosystem II in the absence of the extrinsic proteins and as a function of pH (2000)
    Springer
    Photosynthesis research 65 (2000), S. 175-185 
    Details
    ISSN: 1573-5079
    Keywords: electron paramagnetic resonance ; extrinsic proteins ; manganese cluster ; oxygen evolution ; photosynthesis ; Photosystem II
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Three extrinsic proteins (PsbO, PsbP and PsbQ), with apparent molecular weights of 33, 23 and 17 kDa, bind to the lumenal side of Photosystem II (PS II) and stabilize the manganese, calcium and chloride cofactors of the oxygen evolving complex (OEC). The effect of these proteins on the structure of the tetramanganese cluster, especially their possible involvement in manganese ligation, is investigated in this study by measuring the reported histidine-manganese coupling [Tang et al. (1994) Proc Natl Acad Sci USA 91: 704–708] of PS II membranes depleted of none, two or three of these proteins using ESEEM (electron spin echo envelope modulation) spectroscopy. The results show that neither of the three proteins influence the histidine ligation of manganese. From this, the conserved histidine of the 23 kDa protein can be ruled out as a manganese ligand. Whereas the 33 and 17 kDa proteins lack conserved histidines, the existence of a 33 kDa protein-derived carboxylate ligand has been posited; our results show no evidence for a change of the manganese co-ordination upon removal of this protein. Studies of the pH-dependence of the histidine–manganese coupling show that the histidine ligation is present in PS II centers showing the S2 multiline EPR signal in the pH-range 4.2–9.5.
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    Characterization of chloroplast psbA transformants of Chlamydomonas reinhardtii with impaired processing of a precursor of a photosystem II reaction center protein, D1 (2000)
    Springer
    Plant molecular biology 42 (2000), S. 353-363 
    Details
    ISSN: 1573-5028
    Keywords: Chlamydomonas reinhardtii ; chloroplast transformation ; photosynthesis ; photosystem II ; processing ; psbA gene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract One of the photosystem II reaction center proteins, D1, is encoded by the psbA gene and is synthesized as a precursor form with a carboxyl-terminal extension that is subsequently cleaved between Ala-344 and Ser-345. We have generated three psbA transformants of the green alga Chlamydomonas reinhardtii in which Ala-344 or Ser-345 have been substituted with Pro or Glu (A344P, S345E, and S345P) to understand the effects of the amino acid substitutions on the processing of the precursor D1. S345E grew photoautotrophically and showed PSII activity like the wild type. However, A344P and S345P were unable to grow photoautotrophically and were significantly photosensitive. A344P was deficient in the processing of precursor D1 and in oxygen-evolving activity, but assembled photosystem II complex capable of charge separation. In contrast, both precursor and mature forms of D1 accumulated in S345P cells from the logarithmic phase and the cells evolved oxygen at 18% of wild-type level. However, S345P cells from the stationary phase contained mostly the mature D1 and showed a twofold increase in oxygen-evolving activity. The rate of processing of the accumulated pD1 was estimated to be about 100 times slower than in the wild type. It is therefore concluded that the functional oxygen-evolving complex is assembled when the precursor D1 is processed, albeit at a very low rate. These results suggest the functional significance of the amino acid residues at the processing site of the precursor D1.
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    Isolation and characterization of the wheat prolyl isomerase FK506-binding protein (FKBP) 73 promoter (2000)
    Springer
    Plant molecular biology 42 (2000), S. 489-497 
    Details
    ISSN: 1573-5028
    Keywords: ABA-responsive ; FKBP73 ; promoter ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The wheat FK506-binding protein (FKBP) 73 is a member of the peptidyl prolyl cis-trans isomerase gene family, which catalyses the interconversion between the cis and trans forms of the peptide bond preceding proline residues in proteins. A 3.5 kb sequence 5′ upstream of the ATG codon of the wheat FKBP73 was isolated from a wheat genomic library, and characterized by deletion analysis and transient expression in wheat embryos. The 1517 bp fragment is referred to as the full promoter due to the maximal activity of the fused luciferase reporter gene. Sequence analysis revealed the presence of three abscisic acid (ABA)-responsive elements (ABREs) proximal to coupling elements (CE1-like), a putative lectin box, two putative binding sites for the myb transcription factor and a 36 bp fragment which exhibits 100% identity to the pSau3A9 clone located in the centromeric region of wheat chromosomes. In a transient expression assay the promoter preserved the tissue specificity described in vivo, namely it is expressed only in germinating embryos and young shoots. The promoter was induced 1.9-fold by ABA, the minimal promoter was designated at −221 and the TATA box located at −137. The inducibility by ABA and the expression during germination may indicate that FKBP73 belongs to the group of genes induced by ABA upon germination.
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    Intron-mediated gusA expression in tritordeum and wheat resulting from particle bombardment (2000)
    Springer
    Plant molecular biology 42 (2000), S. 615-622 
    Details
    ISSN: 1573-5028
    Keywords: introns ; maize ubiquitin promoter ; tritordeum ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The promoterless maize ubiquitin first exon and intron fragment can drive gusA expression in immature tritordeum inflorescences and immature wheat scutella. In fluorescence assays, this fragment induces gusA expression in tritordeum inflorescences to 50 times higher than background. The activity of the complete promoter, exon and intron cassette was up to 20 000-fold higher than background but the maize ubiquitin promoter in isolation had very low activity. A construct with the maize alcohol dehydrogenase first exon and intron had low activity, visible in histochemical assays. Both intron sequences have promoter-like features and in the ubiquitin intron there is a sequence homologous to the opaque-2-binding box. We suggest that the combination of these elements may explain the promoter activity detected in these introns.
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    URL: http://dx.doi.org/10.1023/A:1006331831858
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    A rapid induction by elicitors of the mRNA encoding CCD-1, a 14 kDa Ca2+-binding protein in wheat cultured cells (2000)
    Springer
    Plant molecular biology 42 (2000), S. 807-817 
    Details
    ISSN: 1573-5028
    Keywords: Ca2+-binding protein ; EF-hand ; elicitor ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Intracellular Ca2+ has been implicated in the signal transduction processes during the development of the plant defense system against fungal pathogens. From wheat cultured cells that had been treated with the elicitor derived from Typhula ishikariensis, the ccd-1 gene encoding a 14 kDa Ca2+-binding protein with an acidic amphiphilic feature was isolated. The ccd-1-encoded protein (CCD-1) shares homology to the C-terminal half domain of centrin, a Ca2+-binding protein conserved in eukaryotes. Unlike typical eukaryotic centrins, CCD-1 contains only one Ca2+-binding loop, which corresponds to the one in the fourth EF-hand from the N-terminus of centrin. The recombinant CCD protein expressed in Escherichia coli bound to a phenyl-Sepharose column in the presence of Ca2+ and was eluted out by EGTA. It also showed a Ca2+-dependent electrophoretic mobility shift on the non-denaturing polyacrylamide gel. The ccd-1 mRNA expression was rapidly induced by treatment with fungal and chitosan oligosaccharide elicitors, implying that it might have a role in transducing Ca2+ signals provoked by the elicitors. The expression of the ccd-1 mRNA was induced by treatment with A23187, and the induction was suppressed by La3+ or 1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid (BAPTA). This study suggests the involvement of intracellular Ca2+ in the elicitor-induced mRNA expression of a novel class of Ca2+-binding proteins conserved in higher plants.
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    Characterization of site-directed mutants in manganese-stabilizing protein (MSP) of Synechocystis sp. PCC6803 unable to grow photoautotrophically in the absence of cytochrome c-550 (2000)
    Springer
    Plant molecular biology 43 (2000), S. 33-41 
    Details
    ISSN: 1573-5028
    Keywords: cytochrome c-550 ; manganese-stabilizing protein (MSP) ; photosynthesis ; PSII ; Synechocystis sp. PCC6803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract To investigate the interaction between the manganese-stabilizing protein (MSP) and cytochrome c-550 (cyt. c-550) of the photosystem II (PSII) complex in the cyanobacterium Synechocystis sp. PCC6803, three site-directed amino acid substitution mutants in MSP (MSP-D159N, MSP-R163L, MSP-D159N/R163L) were created by single and double amino acid substitution mutagenesis. The modified psbO genes encoding the mutants forms of MSP were used to transform a single-deletion mutant ΔpsO strain lacking MSP as well as a double-deletion strain ΔpsbO:ΔpsbV lacking both MSP and cyt. c-550. The mutant forms of MSP were expressed in each case and all permitted autotrophic growth in strains expressing cyt. c-550. However, when the MSP mutations were introduced into a strain which lacks cyt. c-550 (ΔpsbV), the two single amino acid substitution mutants (ΔpsbV:MSP-D159N and ΔpsbV:MSP-R163L) failed to grow photoautotrophically. These strains exhibited coupled O2-evolving activity of 68–77% compared to the wild-type control using CO2 as an electron acceptor and maximal uncoupled O2-evolution rates of 42–57% using 2,6-dichloro-p-benzoquinone (DCBQ) as an artificial electron acceptor. Interestingly, when the two amino acid substitutions were together in the absence of cyt. c-550 (ΔpsbV:MSP-D159N/R163L), the mutant grew photoautotrophically and the oxygen-evolving activities were higher than in the single mutants. This indicates that the MSP-D159N mutant suppresses the non-autotrophic phenotype of MSP-R163L (or vice versa) in the absence of cyt. c-550. The possibilities of a direct (ionic) or indirect interaction between D159 and R163 of MSP are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006419928712
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  • 92
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    Determination of primary structure of amberjack myosin heavy chain and its relationship with structural stability of various fish myosin rods (2000)
    Springer
    Fish physiology and biochemistry 23 (2000), S. 283-294 
    Details
    ISSN: 1573-5168
    Keywords: amberjack ; myosin heavy chain ; cDNA ; α-helix ; coiled coils ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The structural stability of fish myosin depends upon species and temperatures of water in which fish live. Primary, secondary, and quaternary structures of myosin heavy chain (MyHC) from three species of fish living at different temperature ranges have been compared with those of rabbit MyHC in order to investigate the differences in stability. Primary structure of MyHC, although being accessible for warm-water and cold-water fish (carp and walleye pollack), was not available in previous for tropical-water fish literature; so in this study primary structure of MyHC of the tropical-water fish amberjack has been determined by cloning and sequencing its cDNA. The MyHC has 1938 amino acid residues (AA), which are almost as much as as those of carp and walleye pollack. The amberjack MyHC is 91–95% homologous with other fish and rabbit MyHCs. There is a discernible difference between animal species with stable myosin rod (amberjack, carp, and rabbit) and walleye pollack with unstable rod. Stable rod species have a high probability of forming coiled-coil around the COOH-terminal end of the rod, while the pollack has a low coiled-coil formation probability. In addition, the average scores of the coiled-coil for myosin rod were rabbit (1.738) 〉 amberjack (1.691) 〉 carp (1.680) 〉 walleye pollack (1.674) which correlated exactly with the observed stability. The results suggest that coiled-coil forming ability, particularly around the COOH-terminal end, directs structural stability of fish myosin rod.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011176105285
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  • 93
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    Neocentric activity of rye 5RL chromosome in wheat (2000)
    Springer
    Chromosome research 8 (2000), S. 543-554 
    Details
    ISSN: 1573-6849
    Keywords: genomic in-situ hybridization ; meiosis ; neocentromere ; rye ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The neocentric activity of a constriction located on the long arm of rye 5R chromosome (5RL) was analysed. It is not observed in normal rye but it is unusually stretched in bivalents involving 5RL telosomes in wheat–ditelosomic 5RL addition lines. In 20% of metaphase I cells, the 5RL bivalent presents the centromeres oriented to one pole and the constrictions oriented towards the opposite pole with a strong tension. In 5% of the cells, the constriction was able to orient the bivalent to the poles without tension in the centromeres. Sister chromatid cohesion, which is one of the distinct features of centromeric function, is persistent at the constriction in delayed 5RL chromosomes at anaphase I. Neither the elongation of the constriction nor the neocentric activity was observed at second meiotic division or mitosis. FISH studies showed that the 5RL constriction lacked detectable quantities of two repetitive DNA sequences, CCS1 and the 180-bp knob repeat, present at cereal centromeres and neocentromeres, respectively. We propose that, under special conditions, such as the wheat background, the normally non-centromeric DNA present at this region of 5RL acquires a specific chromatin structure, differentiated as an elongated constriction, which is able to function as a centromere.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009275807397
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  • 94
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    Distribution and Exudation of Allelochemicals in Wheat Triticum aestivum (2000)
    Springer
    Journal of chemical ecology 26 (2000), S. 2141-2154 
    Details
    ISSN: 1573-1561
    Keywords: Allelopathy ; phenolic acids ; 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one ; DIMBOA ; GC-MS-MS ; wheat ; Triticum aestivum ; weed suppression ; annual ryegrass ; Lolium rigidum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Wheat allelopathy has potential for weed suppression. Allelochemicals were identified in wheat seedlings, and they were exuded from seedlings into agar growth medium. p-Hydroxybenzoic, trans-p-coumaric, cis-p-coumaric, syringic, vanillic, trans-ferulic, and cis-ferulic acids and 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA) were identified in both the shoots and roots of 17-day-old wheat seedlings and their associated agar growth medium. Wheat accessions with previously identified allelopathic activity tended to contain higher levels of allelochemicals than poorly allelopathic ones. The allelopathic compounds present in the shoots generally also were identified in the roots and in the agar medium. Allelochemicals were distributed differentially in wheat, with roots normally containing higher levels of allelochemicals than the shoots. When the eight allelochemicals were grouped into benzoic acid and cinnamic acid derivatives, DIMBOA, total coumaric, and total ferulic acids, the amount of each group of allelochemicals was correlated between the roots and the shoots. Most of the allelochemicals identified in the shoots and roots could be exuded by the living roots of wheat seedling into the agar growth medium. However, the amounts of allelochemicals in the agar growth medium were not proportional to those in the roots. Results suggest that wheat plants may retain allelochemicals once synthesized. The presence of allelochemicals in the agar growth medium demonstrated that wheat seedlings were able to synthesize and to exude phytotoxic compounds through their root system that could inhibit the root growth of annual ryegrass.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005520500110
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  • 95
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    Caffeic Acid-Induced Changes in Plant–Water Relationships and Photosynthesis in Leafy Spurge Euphorbia esula (2000)
    Springer
    Journal of chemical ecology 26 (2000), S. 2095-2109 
    Details
    ISSN: 1573-1561
    Keywords: Caffeic acid ; allelopathy ; plant water balance ; photosynthesis ; chlorophyll fluorescence ; 13C carbon isotopes ; leafy spurge ; Euphorbia esula ; small everlasting ; Antennaria microphylla
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Leafy spurge (Euphorbia esula), a native perennial weed introduced from Eurasia around the turn of the century, disrupts natural and agroecosystems across much of the Northern Great Plains. While leafy spurge displaces many native plant species, it has been demonstrated that small everlasting (Antennaria microphylla), a native perennial, is allelopathic to leafy spurge. Caffeic acid (CA), one of three compounds isolated from small everlasting, inhibits leafy spurge seed germination, root elongation, and callus culture growth. This study investigated the mechanism of this interference at the whole-plant level. Results indicate that inhibition of growth in leafy spurge after exposure to CA is primarily due to a disruption of plant–water relations. Leafy spurge cuttings were propagated in 0.5 strength Hoagland's nutrient solution for 30 days. For treatments, six plants were transferred into nutrient medium amended with either 0.1 or 0.25 mM CA for a period of 30 days. To determine the effect of pH, two additional groups of six plants were grown in nutrient medium adjusted with HCl corresponding to pH levels of plants treated with CA (pH 5.5–5.8 for 0.1 mM CA and pH 4.5–4.8 for 0.25 mM CA). By day 12 of the treatment period, plants treated with both levels of CA had significantly higher leaf diffusive resistances than control plants. Plants grown at the corresponding pH levels experienced higher diffusive resistances later in the treatment period (day 21). Transpiration was similarly affected with treated plants showing relatively higher transpiration rates compared to controls. Chlorophyll fluorescence was significantly lower than controls in all treated plants by end of the treatment period. The stable carbon isotope ratio (13C:12C) in these plants was higher than controls. These data show that a disruption of plant water relations is the primary mechanism of plant growth inhibition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005564315131
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  • 96
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    Nitrogen in percolation water in paddy fields with a rice/wheat rotation (2000)
    Springer
    Nutrient cycling in agroecosystems 57 (2000), S. 75-82 
    Details
    ISSN: 1573-0867
    Keywords: nitrogen ; leaching ; paddy soil ; wheat ; rice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Nitrogen in percolation water was observed in paddy field soil under rice/wheat rotation. Different N-application rates were designed. Porous pipes were installed in triplicate at depths of 30, 60 and 90 cm to collect the water in the period of wheat growth. Suction cups were installed in triplicate at the same depths to collect the water during the period of rice growth. NH4 +, NO3 - and total N in the water were analysed with a continuous-flow nitrogen analyzer. Results showed that nitrate was the predominant form of nitrogen in percolation water during the period of wheat growth. Nitrate leaching was high in early spring after the `tillering fertilisation'. More than 50 mg l-1 of nitrate concentration in percolation water was observed for 30 and 60 cm in depth and more than 15 mg l-1 were observed for 90 cm. The concentration decreased quickly and was very low, less than 2 mg l-1 usually, in the earring stage of wheat. Nitrate in water was low, less than 1.5 mg l-1 usually, when the field was flooded during the period of rice growth. Some soluble organic N existed in the water. Nitrate in percolation water increased when the field was drained. The leaching loss of nitrogen during winter wheat growth period was estimated to be about 3.4% of the N-fertiliser applied at the normal application rate of farmers; for the rice growth period it was around 1.8%. Although a reduced N-application decreased N leaching, it caused a marked decrease in crop yield.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009712404335
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  • 97
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    Numerical Investigation of a Stability Theorem Arising from the 2-Dimensional Analysis of an Iterative Optimal Control Algorithm (2000)
    Springer
    Multidimensional systems and signal processing 11 (2000), S. 109-124 
    Details
    ISSN: 1573-0824
    Keywords: 2-D linear systems ; optimal control ; stability ; unit memory linear repetitive processes ; numerical methods
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Because many optimal control problems require solution using iterative procedures they fall naturally in the realm of 2-D systems where the two dimensions are response time horizon and iteration index, respectively. The paper uses this observation to employ 2-D systems theory, in the form of unit memory repetitive process techniques, to analyse local stability and convergence behaviour of a continuous optimal control algorithm based on dynamic system optimisation and parameter estimation. Existing work is extended to incorporate unmatched terminal constraints. Necessary and sufficient conditions for stability are obtained whose evaluation require the solution of a difficult eigenvalue problem. The paper shows how solutions can be achieved using numerical and graphical facilities of MATLAB.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008490731182
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  • 98
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    The Jump Behavior and Stability Analysis for 2-D Singular Systems (2000)
    Springer
    Multidimensional systems and signal processing 11 (2000), S. 339-358 
    Details
    ISSN: 1573-0824
    Keywords: 2-D systems ; descriptor systems ; singular systems ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract In this paper, we discussthe jump behavior and stability problems for 2-D linear shift-invariantsingular systems under the standard boundary conditions. It isshown that once a boundary condition or the input is inadmissiblein the classical sense, a group of non-causal or backward jumpsof the system states will be incited. This interpretation releasesthe conventional admissibility constraints on the boundary conditionsand inputs. Based on this observation, a systematic stabilitytheory is developed for 2-D singular systems. The well-knownbasic stability theorem for the 1-D singular systems or 2-D regularsystems is thus extended to the 2-D singular case.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008429611994
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  • 99
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    Electronic Excited States of the CP29 Antenna Complex of Green Plants: A Model Based on Exciton Calculations (2000)
    Springer
    Journal of biological physics 26 (2000), S. 321-339 
    Details
    ISSN: 1573-0689
    Keywords: CP29 ; electronic excited states ; energy transfer ; LHCII ; light-harvesting complexes ; photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract We have suggested a model for the electronic excited states of the minorplant antenna, CP29, by incorporating a considerable part of the currentinformation offered by structure determination, site-directed mutagenesis,and spectroscopy in the modeling.We have assumed that the electronic excited states of the complex havebeen decided by the chlorophyll-chlorophyll (Chl) and Chl-proteininteractions and have modeled the Coulombic interaction between a pairof Chls in the point-dipole approximation and the Chl-protein interactionsare treated as empirical fit parameters.We have suggested the Qy dipole moment orientations and the siteenergies for all the chlorophylls in the complex through a simultaneoussimulation of the absorption and linear dichroism spectra.The assignments proposed have been discussed to yield a satisfactoryreproduction of all prominent features of the absorption, linear and circulardichroism spectra as well as the key spectral and temporal characteristics ofthe energy transfer processes among the chlorophylls.The orientations and the spectral assignments obtained by relatively simpleexciton calculations have been necessary to provide a good point ofdeparture for more detailed treatments of structure-function relationship inCP29. Moreover, it has been discussed that the CP29 model suggested canguide the studies for a better understanding of the structure-functionrelationship in the major plant antenna, LHCII.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010352731838
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  • 100
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    Electron spin-lattice relaxation studies of different forms of the S2 state multiline EPR signal of the Photosystem II oxygen-evolving complex (2000)
    Springer
    Photosynthesis research 66 (2000), S. 189-198 
    Details
    ISSN: 1573-5079
    Keywords: electron spin-lattice relaxation rate ; manganese ; oxygen-evolving complex ; photosynthesis ; Photosystem II
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The pulsed EPR inversion recovery sequence has been utilized to monitor the temperature dependence of the electron spin-lattice relaxation rate of the Mn cluster of the Photosystem II oxygen evolving complex poised in a variety of S 2 state forms giving rise to g = 2 multiline EPR signals. A previous study (Lorigan and Britt (1994) Biochemistry 33: 12072–12076) showed that for PS II membranes treated with 5% ethanol, the S 2 state Mn cluster relaxes via the Orbach spin-lattice relaxation mechanism, where the relaxation is enhanced via phonon scattering off an excited state spin manifold, in this case at an energy of Δ = 36.5 cm−1 above the S = 1/2 ground state giving rise to the multiline EPR signal. Parallel experiments are reported for PS II membranes with 5% methanol, treated with ammonia, and following short and long term dark adaptation. In each case, the temperature dependence of the electron spin-lattice relaxation rate is consistent with Orbach relaxation, and the range of excited state energies is relatively narrow (33.8 cm−1 ≤ Δ ≤ 39.7 cm−1). In addition, short term dark adapted (6 min, ‘active state’) PS II membranes show biphasic recovery traces which indicate that a minority fraction of the oxygen evolving complexes are trapped in a form with greatly slowed spin-lattice relaxation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010604607891
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