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  • Triticum aestivum  (60)
  • nitrogen  (51)
  • stability  (40)
  • Springer  (150)
  • Annual Reviews
  • Blackwell Publishing Ltd
  • 2005-2009
  • 1990-1994  (150)
  • 1980-1984
  • 1955-1959
  • 1992  (150)
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  • 2005-2009
  • 1990-1994  (150)
  • 1980-1984
  • 1955-1959
Year
  • 1
    Electronic Resource
    Electronic Resource
    Characterization of stable matchings as extreme points of a polytope (1992)
    Springer
    Mathematical programming 54 (1992), S. 57-67 
    Details
    ISSN: 1436-4646
    Keywords: Matchings ; stability ; extreme points ; polytope
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract The purpose of this paper is to extend a modified version of a recent result of Vande Vate (1989) which characterizes stable matchings as the extreme points of a certain polytope. Our proofs are simpler and more transparent than those of Vande Vate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01586041
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  • 2
    Electronic Resource
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    Diet-switching by gypsy moth: effects of diet nitrogen history vs. switching on growth, consumption, and food utilization (1992)
    Springer
    Entomologia experimentalis et applicata 64 (1992), S. 225-238 
    Details
    ISSN: 1570-7458
    Keywords: Lymantria dispar (L.) ; diet switching ; nitrogen ; specialization ; plant-animal interactions ; insect behavior
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Gypsy moth (Lymantria dispar (L.) (Lepidoptera: Lymantriidae)) larvae were reared from hatch on 1.25% N or 3.5% N artificial diet (previous diet) and switched reciprocally to the other diet (current diet) after molting into the second, third, fourth, or fifth instar. The nitrogen concentration of food consumed during previous instars had a strong residual effect on the growth rate in subsequent instars when a diet switch was made during instars two through four, but did not affect growth rate of fifth-instar larvae despite effects on food consumption and utilization. In early instars, larvae reared on 1.25% N artificial diet and then switched to 3.75% N diet had lower mass-adjusted growth rates than larvae continuously reared on 3.75% N diet. Conversely, larvae reared on 3.75% N diet and switched to 1.25% N had higher mass-adjusted growth rates than larvae reared continuously on 1.25% N diet. Relative to larvae previously reared on 1.25% N diet, fifth-instar male larvae previously reared on 3.75% N diet had slightly lower consumption rates, higher net growth efficiency (ECD), and higher gross growth efficiency (ECI). Larvae previously reared on 3.75% N diet tended to have lower food assimilation efficiency (AD) and lower nitrogen assimilation efficiency (AD(N)). Although both previous and current diet nitrogen concentration strongly affected larval growth and food utilization, the interaction term between these was not significant for any response variables except ECD and ECI. Because the interaction term reflects the effect of switching per se, the results indicate that there was a metabolic cost associated with switching, but no inherent net cost or benefit of diet-switching to growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00341086
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  • 3
    Electronic Resource
    Electronic Resource
    Phthalocyanine-containing polymers (1992)
    Springer
    Journal of inorganic and organometallic polymers and materials 2 (1992), S. 79-85 
    Details
    ISSN: 1572-8870
    Keywords: Phthalocyanines ; polymers ; siloxanes ; conductivity ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The author's work on the incorporation of phthalocyanines into inorganic polymers is reviewed. The synthesis of poly(siloxane phthalocyanines) and the synthesis and characterization of fluoro(phthalocyanine) Group III compounds and their conducting derivatives are described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00696537
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  • 4
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    Analytical relationships between the ionization of 1,3-dicarbonylic ligands and stability of their Cr(III), Ni(II), Co(II) and Cu(II) 1∶1 chelates (1992)
    Springer
    Journal of solution chemistry 21 (1992), S. 1145-1152 
    Details
    ISSN: 1572-8927
    Keywords: Chromium(III) ; β-diketones ; β-diketonates ; chelation ; complexation ; correlation ; stability ; equilibrium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract It has been demonstrated that the logarithm of the stability constant of some monochelated chromium(III) compounds, with structurally similar 1,3-dicarbonylic species, is linearly related to the negative logarithm of the acid ionization constant of the ligand. Graphical and analytical correlations which could be useful in predicting equilibrium constants of chromium(III)-β-diketonates, as well as other first-row transition metal derivatives, have been developed. A quantitative evaluation of the complexes stability has been carried out, providing information about the effects of ligand substituents on the equilibrium constants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00651860
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  • 5
    Electronic Resource
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    On the rate-determining step and the role of potassium in the catalytic synthesis of ammonia (1992)
    Springer
    Catalysis letters 13 (1992), S. 45-53 
    Details
    ISSN: 1572-879X
    Keywords: Ammonia ; synthesis ; nitrogen ; rate-determining step ; potassium promotion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The simple concept of a single rate-determining step, the dissociation of N2(a), in ammonia synthesis is inconsistent with experimental results. It is proposed that three reaction steps, N2(a) → 2N(a) (1) N(a) + H(a)→NH(a) (2) NH3(a)→NH3(g) (3) are dominant in determining the rate of synthesis. Under industrial conditions reactions (2) and (3) are more important than (1). The role of K+ as promoter in these reactions is discussed, especially as an “anchor” for adsorbed oxygen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00770946
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  • 6
    Electronic Resource
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    A study of nitrogen and carbon dioxide chemisorption on platinum black (1992)
    Springer
    Catalysis letters 16 (1992), S. 159-164 
    Details
    ISSN: 1572-879X
    Keywords: Chemisorption ; nitrogen ; carbon dioxide ; platinum ; water gas shift reaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The relationship between sites responsible for nitrogen chemisorption and sites responsible for stronger adsorption of carbon dioxide on platinum black is reported. A 2 to 1 ratio has been found between molecules of more strongly adsorbed carbon dioxide and molecules of nitrogen chemisorbed on individual samples. This relationship has allowed us to deduce the structure of chemisorbed carbon dioxide. Carbon dioxide is relatively weakly chemisorbed on platinum. Reasons for the weakness of this chemisorption are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00764366
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  • 7
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    Interval stability and interval covering property in finite posets (1992)
    Springer
    Order 9 (1992), S. 163-175 
    Details
    ISSN: 1572-9273
    Keywords: Primary 06A07 ; secondary 05C70 ; Partial order ; interval ; stability ; covering ; Sperner property ; symmetric chains ; NP-completeness
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract Given a finite ranked posetP, let α(P) be the maximum size of a subset ofP such that no two elements of it belong simultaneously to some interval ofP and let ϱ(P) be the minimum number of intervals covering all elements ofP. We say thatP has the strong interval stability property (resp. the strong interval covering property) if for each subposetP′ induced by consecutive levels ofP, i.e.,P′=P (l)∪...∪P (u), one has α(P′)=max{|P (l)|, |P (u)|} (resp. ϱ(P′)=max{|P (l)|, |P (u)|}). We prove these properties for several classes of posets and discuss some general facts concerning the numbers α(P) and ϱ(P), e.g., NP-completeness and min-max relations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00814408
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  • 8
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    Stationary waiting time derivatives (1992)
    Springer
    Queueing systems 12 (1992), S. 369-389 
    Details
    ISSN: 1572-9443
    Keywords: Perturbation analysis ; stability ; stochastic difference equations ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract We investigate the stability of waiting-time derivatives when inputs to a queueing system-service times and interarrival times-depend on a parameter. We give conditions under which the sequence of waiting-time derivatives admits a stationary distribution, and under which the derivatives converge to the stationary regime from all initial conditions. Further hypotheses ensure that the expectation of a stationary waiting-time derivative is, in fact, the derivative of the expected stationary waiting time. This validates the use of simulation-based infinitesimal perturbation analysis estimates with a variety of queueing processes. We examine waiting-time sequences satisfying recursive equations. Our basic assumption is that the input and its derivatives are stationary and ergodic. Under monotonicity conditions, the method of Loynes establishes the convergence of the derivatives. Even without such conditions, the derivatives obey a linear difference equation with random coefficients, and we exploit this fact to find stability conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01158809
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  • 9
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    Stability of token passing rings (1992)
    Springer
    Queueing systems 11 (1992), S. 7-33 
    Details
    ISSN: 1572-9443
    Keywords: Token passing rings ; stability ; substability ; ergodicity ; Markov chains ; Loynes' scheme ; stochastically dominant ; Little's formula ; regenerative processes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract A sufficient stability condition for the standard token passing ring has been “known” since the seminal paper by Kuehn in 1979. However, this condition was derived without formal proof, and the proof seems to be of considerable interest to the research community. In fact, Watson observed that in the performance evaluation of token passing rings, “it is convenient to derive stability conditions ... (without proof)”. Our intention is to fill this gap, and to provide a formal proof of thesufficient and necessary stability condition for the token passing ring. In this paper, we present the case when the arrival process to each queue is Poisson but service times and switchover times are generally distributed. We consider in depth a gatedl-limited (l≤ ∞) service discipline for each station. We also indicate that the basic steps of our technique can be used to study the stability of some other multiqueue systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01159285
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  • 10
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    Stable steady state of some population models (1992)
    Springer
    Journal of dynamics and differential equations 4 (1992), S. 161-190 
    Details
    ISSN: 1572-9222
    Keywords: Delay differential equations ; equilibrium ; stability ; limiting equations ; population dynamics ; 34K20 ; 34K25 ; 92A15
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract Applying an analytical method and several limiting equations arguments, some sufficient conditions are provided for the existence of a unique positive equilibriumK for the delay differential equationx=−γx+D(x t ), which is the general form of many population models. The results are concerned with the global attractivity, uniform stability, and uniform asymptotic stability ofK. Application of the results to some known population models, which shows the effectiveness of the methods applied here, is also presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01048159
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  • 11
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    Stability estimates in inverse scattering (1992)
    Springer
    Acta applicandae mathematicae 28 (1992), S. 1-42 
    Details
    ISSN: 1572-9036
    Keywords: 35R30 ; Inverse scattering ; stability ; noisy data
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract An algorithm is given for calculating the solution to the 3D inverse scattering problem with noisy discrete fixed energy data. The error estimates for the calculated solution are derived. The methods developed are of a general nature and can be used in many applications: in nondestructive evaluation and remote sensing, in geophysical exploration, medical diagnostics, and technology.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00047029
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  • 12
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    A new interpolation procedure for adapting Runge-Kutta methods to delay differential equations (1992)
    Springer
    BIT 32 (1992), S. 634-649 
    Details
    ISSN: 1572-9125
    Keywords: AMS(MOS): 65L20 ; CR: 5.17 ; delay differential equations ; numerical solution ; Runge-Kutta methods ; interpolation procedures ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract This paper deals with adapting Runge-Kutta methods to differential equations with a lagging argument. A new interpolation procedure is introduced which leads to numerical processes that satisfy an important asymptotic stability condition related to the class of testproblemsU′(t)=λU(t)+μU(t−τ) with λ, μ ε C, Re(λ)〈−|μ|, and τ〉0. Ifc i denotes theith abscissa of a given Runge-Kutta method, then in thenth stept n−1→t n :=t n−1+h of the numerical process our interpolation procedure computes an approximation toU(t n−1+c i h−τ) from approximations that have already been generated by the process at pointst j−1+c i h(j=1,2,3,...). For two of these new processes and a standard process we shall consider the convergence behaviour in an actual application to a given, stiff problem.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01994847
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  • 13
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    On a class of variational equations transformable to the Gauss hypergeometric equation (1992)
    Springer
    Celestial mechanics and dynamical astronomy 53 (1992), S. 145-150 
    Details
    ISSN: 1572-9478
    Keywords: Monodromy matrix ; Gauss hypergeometric equation ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A new class of linear ordinary differential equations with periodic coefficients is found which can be transformed to the Gauss hypergeometric equation, and therefore the monodromy matrices are computable explicitly. These equations appear as the variational equations around a straight-line solution in Hamiltonian systems of the form H = T(p) + V(q), where T(p) and V(q) are homogeneous functions of p and q, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00049462
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  • 14
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    Effects of small external forces on the planar oscillation of a cable connected satellites system (1992)
    Springer
    Celestial mechanics and dynamical astronomy 53 (1992), S. 219-226 
    Details
    ISSN: 1572-9478
    Keywords: Artificial satellite ; dissipative forces ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The effects of small external dissipative and disturbing forces on the non-linear planar oscillation of a cable connected satellites system in the central gravitational field of earth have been studied. Typical non-linear oscillation's phenomena arizing from the aforesaid external forces are shown to take place. The presence of these forces enables the application of asymptotic methods of the theory of non-linear oscillations due to Bogoliubov and Mitropolsky to the equation characterizing the non-linear oscillation of the system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00052610
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  • 15
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    The influence of nutritional and genetic factors on larval performance of the cinnabar moth, Tyria jacobaeae (1992)
    Springer
    Entomologia experimentalis et applicata 62 (1992), S. 29-36 
    Details
    ISSN: 1570-7458
    Keywords: Alkaloids ; cinnabar moth ; insect genetics ; larval performance ; Lepidoptera ; nutritional ecology ; nitrogen ; sugar ; Tyria jacobaeae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In a laboratory experiment using full-sibs, 60% of the variation in pupal weight of the monophage Tyria jacobaeae L. (Lepidoptera, Arctiidae) could be explained by variation in the nitrogen concentration of the food plant, Senecio jacobaea L. and only 4% by variation in sugar concentration. Larval weight and growth rates of young and old larvae were also positively correlated with nitrogen and sugar concentration. Developmental time was negatively correlated with nitrogen concentration. In a second experiment full-sib families differed significantly in larval weight at day 7, mortality, growth rate and developmental time. Pupal weight did not differ significantly among families, but was positively correlated with nitrogen concentration of Senecio. Larval performance was not significantly influenced by concentrations of sugars or alkaloids. We conclude that larval performance of Tyria during most of the larval period is mainly determined by genetic factors, but pupal weights are primarily determined by nitrogen concentration of the food plant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00185638
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  • 16
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    Real-time feedback scheduling of flexible manufacturing systems (1992)
    Springer
    Journal of intelligent and robotic systems 6 (1992), S. 51-63 
    Details
    ISSN: 1573-0409
    Keywords: Scheduling ; flexible manufacturing systems ; stability ; feedback
    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 A genetic manufacturing environment is considered. The emphasis is on small-lot, discrete, and asynchronous type of manufacturing systems rather than high volume and continuous type. Two classes of scheduling policies are proposed to render the machine stable. The policies are of feedback type. The decision is made in real-time and on-line.
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    URL: http://dx.doi.org/10.1007/BF00314697
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  • 17
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    Force control of robots with nonlinearities (1992)
    Springer
    Journal of intelligent and robotic systems 6 (1992), S. 219-240 
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    ISSN: 1573-0409
    Keywords: Force control ; slip-stick friction ; stability
    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 This paper explores two practical issues related to the force control of manipulators. The first issue examined is how system stability is effected by commonly occurring manipulator nonlinearities, such as sampled-data, control signal saturation and slip-stick friction. It is shown that discretely implemented force control algorithms can drive the feedback force controlled manipulator into a limit cycle, even for a very small sampling period that by far satisfies Shannon's sampling theorem. The bounds of stability are enhanced by the presence of control signal saturation and slip stick friction. The second issue investigated is the inclusion of a high gain inner position loop as a means to minimize the unpredictability in the steady state error due to slip-stick friction. In order to support the theoretical conclusions, experiments were performed with the PUMP 560 industrial robot testbed facility developed at Colorado State University.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00248017
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  • 18
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    A structural approach to robust stability of polynomials (1992)
    Springer
    Multidimensional systems and signal processing 3 (1992), S. 421-425 
    Details
    ISSN: 1573-0824
    Keywords: Convex combination ; polynomial ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract A sufficient condition for Hurwitz stability of a convex combination of two stable polynomials is obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01940234
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  • 19
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    Effect of foliar sprayings of urea during or after anthesis on dry matter and nitrogen accumulation in the grain of two wheat cultivars ofT. aestivum L. (1992)
    Springer
    Nutrient cycling in agroecosystems 31 (1992), S. 79-84 
    Details
    ISSN: 1573-0867
    Keywords: Wheat ; nitrogen ; grain protein content ; grain filling ; urea spraying
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The objective of this work was to determine the effect of foliar urea spraying during or after anthesis, on dry matter and nitrogen accumulation in the wheat grain of two cultivars, differing in grain protein content. The experiment was carried out in the field, and 20 kg N ha−1 as urea (46-0-0) was sprayed at anthesis, 7 or 14 days after anthesis. Dry weight, N content and N percentage of the grain were determined at several stages of its development. Neither the rate nor the duration of dry matter accumulation in the grain was significantly modified by N sprayings at anthesis or later and, consequently, not its final weight. Nitrogen sprayings at anthesis or later increased the grain N content and N percentage at ripeness in both cultivars, but to a greater extent in the low grain protein cultivar. Greater N content in the grain was attributed to a rapid uptake of the N applied and not to a longer duration of the period of N accumulation. The different responses of the cultivars to N sprayings can be related to differences in N demand, and is probably associated, also, to a genetic ability to accumulate N in the grain.
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    URL: http://dx.doi.org/10.1007/BF01064230
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  • 20
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    Influence of delaying flood and preflood nitrogen application on dry-seeded rice (1992)
    Springer
    Nutrient cycling in agroecosystems 32 (1992), S. 55-59 
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    ISSN: 1573-0867
    Keywords: 15N ; nitrogen ; rice ; soil N ; N fertilizer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In the southern U.S. rice belt it is recommended that rice (Oryza sativa L.) grown in the dry-seeded, delayed flood cultural system have the preflood N fertilizer applied and the field flooded at the fourth to fifth leaf stage of plant development. The objective of this field study was to determine if delaying the flood and preflood N application past the fifth leaf stage was detrimental to rice total N and fertilizer15N uptake, total dry matter, and grain yield. This study was conducted on a Crowley silt loam (Typic Albaqualfs) and a Perry clay (Vertic Haplaquepts). The preflood N fertilizer and flood were delayed 0, 7, 14, or 21 d past the fourth to fifth leaf stage, after which time a permanent flood was established and maintained until maturity. All treatments received 20.5 g N m−2 as15N-labeled urea in three topdress applications. All plant and soil samples were taken at maturity. Harvest index increased as the preflood N and flood were delayed past the 4 to 5 leaf stage. Total N in the grain + straw either decreased or showed a decreasing trend as the N and flood were delayed. Similarly, uptake of native soil N decreased as flood was delayed. Conversely, percent recovery of fertilizer N in the rice plant and the plant-soil system increased as the preflood N and flood were delayed. Rice grain yield was not significantly affected by delaying the preflood N and flood up to 21 d.
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    URL: http://dx.doi.org/10.1007/BF01054394
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  • 21
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    Fertilizer value of pig slurries processed by the Promest procedure (1992)
    Springer
    Nutrient cycling in agroecosystems 32 (1992), S. 61-70 
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    ISSN: 1573-0867
    Keywords: Pig slurry ; processing ; relative efficiency index ; N ; P ; K ; organic carbon ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In the Netherlands, pig slurries are processed to improve their fertilizer value as well as handling and application. The relative efficiency index (REI) of N, P and K and the stability of organic carbon (C) in test products of processed pig slurries (PPS) were determined in pot and incubation experiments. The dry and easily manageable PPS were produced according to the Promest procedure. The mineral fraction of total N varied from 60 to 88%. It consisted mainly of nitrate. About 25% of the organic N was rapidly mineralized. The REI of N varied from 66 to 92%. After application REI of P from pelletized PPS varied from 41 to 62% in the first half year. The REI of P in ground but non-pelletized PPS varied from 81 to 100%. The REI of K was estimated to be 100%. PPS contained less easily decomposable organic C than untreated pig slurry due to the anaerobic digestion step in the processing procedure. About 34% of the organic C disappeared as methane and carbon dioxide during processing. It was concluded that processing improved the fertilizer value of PPS compared with that of untreated pig slurry.
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    URL: http://dx.doi.org/10.1007/BF01054395
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  • 22
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    Impact of Eucalyptus tereticornis Sm. shelterbelts on crops (1992)
    Springer
    Agroforestry systems 20 (1992), S. 253-266 
    Details
    ISSN: 1572-9680
    Keywords: allelopathy ; shelterbelt ; soil phytotoxins ; Cicer arietinum ; Lens esculentum ; Triticum aestivum ; Brassica oleracea ; Trifolium alexandrinum ; Eucalyptus tereticornis ; Brassica campestris cv toria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The economic yield of chickpea, lentil, wheat, cauliflower, barseem, and toria in a 12-m-wide strip to the south of 8 ± 1-year-old Eucalyptus tereticornis shelterbelts (three different locations) was reduced by more than half. Among all the crops under study, the yield of chickpea was reduced by the maximum extent. The content of soil phytotoxins was maximum in the litter-free top soil surface, compared to that at 30 or 60 cm depths, at all distances from the Eucalyptus. Maximum content of phytotoxins was found at 1 m from the tree line for all depths. These soil phytotoxins impaired the germination of Lens esculentum, thus indicating an allelopathic effect. It is included that the poor perfornce of crops in the sheltered area is related to an allelopathic effect of the Eucalyptus.
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    URL: http://dx.doi.org/10.1007/BF00053143
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  • 23
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    Nutrient-chlorophyll trajectories across trophic gradients (1992)
    Springer
    Aquatic sciences 54 (1992), S. 58-76 
    Details
    ISSN: 1420-9055
    Keywords: Eutrophication ; lake management ; phosphorus ; nitrogen ; chlorophyll-a ; slope estimator
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We estimate the response of chl-a (mg · m−3) to changes in concentrations of total phosphorus (TP) by calculating the slopeS = Δchl-a/ΔTP in chl-a =f(TP) graphs. Results show that in years where algae are P-limited oligotrophic lakes respond less (median slope 0.21) to changes in nutrient concentrations than eutrophic lakes, (median slope 0.31) and these again less than hypereutrophic lakes, (median slope 1.02). We find no saturation value for the slope within the TP range considered (6–480 mg · m−3). Chl-a in eutrophic lakes responds more frequently to non-nutrient factors than oligotrophic and hypereutrophic lakes. Results obtained by replacing TP with a new nutrient parameter, TP′ = 0.056 · TP · IN0.226, in which inorganic nitrogen, IN, is factored in, suggest that nitrogen has an influence on chl-a in oligotrophic lakes. Blue-green algae respond less to changes in TP than other algal species, e.g., diatoms.
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    URL: http://dx.doi.org/10.1007/BF00877264
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    A reinforcement connectionist approach to robot path finding in non-maze-like environments (1992)
    Springer
    Machine learning 8 (1992), S. 363-395 
    Details
    ISSN: 0885-6125
    Keywords: Connectionism ; reinforcement learning ; robot path finding ; stability ; reactive systems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract This paper presents a reinforcement connectionist system which finds and learns the suitable situation-action rules so as to generate feasible paths for a point robot in a 2D environment with circular obstacles. The basic reinforcement algorithm is extended with a strategy for discovering stable solution paths. Equipped with this strategy and a powerful codification scheme, the path-finder (i) learns quickly, (ii) deals with continuous-valued inputs and outputs, (iii) exhibits good noise-tolerance and generalization capabilities, (iv) copes with dynamic environments, and (v) solves an instance of the path finding problem with strong performance demands.
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    URL: http://dx.doi.org/10.1007/BF00992702
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    A Reinforcement Connectionist Approach to Robot Path Finding in Non-Maze-Like Environments (1992)
    Springer
    Machine learning 8 (1992), S. 363-395 
    Details
    ISSN: 0885-6125
    Keywords: Connectionism ; reinforcement learning ; robot path finding ; stability ; reactive systems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract This paper presents a reinforcement connectionist system which finds and learns the suitable situation-action rules so as to generate feasible paths for a point robot in a 2D environment with circular obstacles. The basic reinforcement algorithm is extended with a strategy for discovering stable solution paths. Equipped with this strategy and a powerful codification scheme, the path-finder (i) learns quickly, (ii) deals with continuous-valued inputs and outputs, (iii) exhibits good noise-tolerance and generalization capabilities, (iv) copes with dynamic environments, and (v) solves an instance of the path finding problem with strong performance demands.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022684924132
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    Plant competition and disease in genetically diverse wheat populations (1992)
    Springer
    Oecologia 91 (1992), S. 82-92 
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    ISSN: 1432-1939
    Keywords: Plant disease ; Genetic diversity ; Frequency-dependence ; Triticum aestivum ; Puccinia striiformis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The direct and indirect effects of plant genetic diversity on epidemics and the influence of disease on plant competition were investigated using the wheat (Triticum aestivum)/stripe rust (Puccinia striiformis) system. Replacement series consisting of a susceptible and a resistant wheat genotype or two wheat genotypes susceptible to different races of stripe rust were grown in the presence and absence of the pathogen. Stripe rust severity, number of seed heads, seed yield, and seed weight were determined separately for each wheat genotype in the mixtures and the pure stands. The frequency of susceptible genotypes in a mixture explained up to 67% of the variation in disease severity. However, competitive interactions among plant genotypes sometimes appeared to alter susceptibility and obscured the relationship. In pure stands of single genotypes, disease severity explained between 52 and 58% of the variation in seed yield. In mixtures, coefficients of determination were only 10 and 31%, suggesting a strong influence of plant-plant interactions on seed yield. These results suggest that host-parasite coevolutionary models need to account for the strong effect that specific plant genotype combinations may have on disease severity and plant reproduction.
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    URL: http://dx.doi.org/10.1007/BF00317245
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    In vitro pollen maturation and successful seed production in detached spikelet cultures in wheat (Triticum aestivum L.) (1992)
    Springer
    Sexual plant reproduction 5 (1992), S. 286-291 
    Details
    ISSN: 1432-2145
    Keywords: Triticum aestivum ; Spikelet culture ; In vitro pollen maturation ; Gametophytic selection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Two spring wheat genotypes (cv Orofen and Chinese Spring) were compared for their in vitro pollen maturation capacity in detached spikelet cultures in a defined solid medium. Under these in vitro conditions Chinese Spring produced normal trinucleate pollen in 66.8% and Orofen in only 37.5%. In both cultivars the pollen maturation process from the middle uninucleate stage took approximately 3 days longer in vitro than in vivo. The pollen maturation time depended on the microspore developmental stage at the time that the culturing started. The viability, germination capacity, and fertilizing ability of the in vitro matured pollen also differed between the two genotypes. The seed set achieved in vitro (averagely 12.8%) offers promise for the practical application of this method for producing controlled or selected offspring.
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    URL: http://dx.doi.org/10.1007/BF00197380
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    Intracellular motility, the actin cytoskeleton and germinability in the pollen of wheat (Triticum aestivum L.) (1992)
    Springer
    Sexual plant reproduction 5 (1992), S. 247-255 
    Details
    ISSN: 1432-2145
    Keywords: Wheat ; Triticum aestivum ; Pollen germinability ; Intracellular movement ; Actin cytoskeleton ; Effects of dehydration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The tricellular pollen of wheat germinates rapidly on a receptive stigma without the often protracted activation period characteristic of bicellular pollens. This is associated with a high level of hydration in the mature pollen and the absence of a dormancy period. Intracellular movement of organelles continues throughout development; in the mature pollen along pathways related both to the aperture site and the distribution of the amyloplasts in the vegetative cell. The movement pathways reflect the organisation of the actin cytoskeleton, elements of which are already focused upon the germination site at the time of dispersal, a disposition only achieved during rehydration and activation in bicellular pollens. Dehydration after dispersal rapidly arrests movement, disrupts the actin cytoskeleton and leads to loss of germinability. These effects are irreversible, again in contrast to the situation found in bicellular pollens such as those of the Liliaceae, species of which have been shown to be capable of withstanding several cycles of hydration and dehydration while still retaining some capacity for germination.
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    URL: http://dx.doi.org/10.1007/BF00197374
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    Embryogenic cell suspensions of Triticum aestivum x Leymus angustus F1 hybrids: characterization and plant regeneration (1992)
    Springer
    Plant cell reports 11 (1992), S. 81-85 
    Details
    ISSN: 1432-203X
    Keywords: Cell suspension ; Somatic embryogenesis ; Triticum aestivum ; Leymus angustus ; Plant regeneration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Embryogenic cell suspension cultures were established from Triticum aestivum X Leymus angustus F1 hybrids, using compact nodular calli derived from inflorescence segments. Calli originating from leaf segments did not give rise to stable cell suspensions. Growth measurements of the cell suspensions revealed that they continued rapid growth up to 10 days after subculturing. Flow cytometric studies of the cell cycle over a 7 day culture period showed that the majority of cells were in G1 phase while the rest were either in S or G2. During the 7 days of culture, no significant differences in DNA distribution patterns were observed. The cells from suspension cultures produced somatic embryos when they were transferred to different solid media. The embryos germinated and gave rise to plantlets which were successfully rooted and transferred to soil.
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    URL: http://dx.doi.org/10.1007/BF00235258
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    Plant regeneration from long term suspension culture-derived protoplasts of hexaploid wheat (Triticum aestivum L.) (1992)
    Springer
    Plant cell reports 11 (1992), S. 262-265 
    Details
    ISSN: 1432-203X
    Keywords: Triticum aestivum ; embryogenic suspension cultures ; protoplasts ; regeneration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Highly regenerable callus cultures have been obtained from immature embryos of hexaploid wheat cv. Oderzo. Friable fast growing calli were induced at high frequency. Suspensions were initiated from the most friable callus lines: they became established in about two months. Suspensions consisted of cell aggregates of 30 to 1000 um in diameter. Upon plating on MS hormone-free medium, suspensions regenerated green plantlets, and their regenerative capability was maintained for at least 10 months. Protoplasts were isolated from 7–8 day old suspension cultures with a yield of 4–6×106 protoplasts/g fresh weight cells. Protoplast culture was either in liquid medium or in a bead-type system with agarose beads. First divisions were detected at day 5. At day 14 visible colonies were detected and the plating efficiency was evaluated between 2 and 8% over the initial number of protoplasts plated. Protoplast-derived calli were cultured in the presence of 1 mg/l IAA and 0.5 mg/l zeatin and were used for reinitiating new suspension cultures. Upon plating onto MS hormone-free medium, with or without the addition of 0.1 mg/l GA3, calliclones were induced to differentiate. Regeneration of complete plantlets, with shoot and roots took about two months. Plantlets were grown in sterile conditions until 12–15 cm height, and were subsequently transplanted in soil.
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    Nuclear genes control changes in the organization of the mitochondrial genome in tissue cultures derived from immature embryos of wheat (1992)
    Springer
    Current genetics 21 (1992), S. 515-520 
    Details
    ISSN: 1432-0983
    Keywords: Nuclear-cytoplasmic interactions ; Mitochondrial genome ; Chondriome variability ; Triticum aestivum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Although the mitochondrial genomes of the Chinese Spring and Aquila varieties of wheat are normaly similar in organization, this is not so in tissue cultures initiated from their immature embryos where the mitochondrial genomes of both are rearranged and in different, characteristic, ways. However, the mitochondrial genomes of tissue cultures of reciprocal F1 crosses between these varieties were almost identical to one another, showing that nuclear genes control the rearrangement processes. These rearrangements are either due to the appearance of new structures or else result from changes in the relative amounts of subgenomic components. The severe reduction in the amount of certain molecular configurations in tissue cultures from reciprocal crosses is probably due to the presence of dominant information in the Aquila nuclear genome. Data obtained from tissue cultures initiated from F2 embryos of the cross Aquila x Chinese Spring suggest that at least two complementary genes are involved in this control. In contrast, the presence of new molecular arrangements appears to be under the control of a dominant allelic form of a Chinese Spring gene or genes. Thus, this study demonstrates that at least two sets of nuclear genes control the reorganization of the mitochondrial genome which occurs when tissue cultures are initiated from the immature embryos of wheat.
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    URL: http://dx.doi.org/10.1007/BF00351662
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    Allelopathic activity in wheat-conventional and wheat-no-till soils: Development of soil extract bioassays (1992)
    Springer
    Journal of chemical ecology 18 (1992), S. 2191-2221 
    Details
    ISSN: 1573-1561
    Keywords: Cover crops ; wheat ; Triticum aestivum ; soybean ; Glycine max ; soil extracts ; germination bioassays ; phenolic acids ; hydroxamic acids ; allelopathy ; slope analysis ; ivy-leaved morning glory ; Ipomoea hederacea ; crimson clover ; Trifolium incarnalum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The primary objective of this research was to determine if soil extracts could be used directly in bioassays for the detection of allelopathic activity. Here we describe: (1) a way to estimate levels of allelopathic compounds in soil; (2) how pH, solute potential, and/or ion content of extracts may modify the action of allelopathic compounds on germination and radicle and hypocotyl length of crimson clover (Trifolium incarnatum L.) and ivyleaved morning glory (Ipomoea hederacea L. Jacquin.); and (3) how biological activity of soil extracts may be determined. A water-autoclave extraction procedure was chosen over the immediate-water and 5-hr EDTA extraction procedures, because the autoclave procedure was effective in extracting solution and reversibly bound ferulic acid as well as phenolic acids from wheat debris. The resulting soil extracts were used directly in germination bioassays. A mixture of phenolic acids similar to that obtained from wheat-no-till soils did not affect germination of clover or morning glory and radicle and hypocotyl length of morning glory. The mixture did, however, reduce radicle and hypocotyl length of clover. Individual phenolic acids also did not inhibit germination, but did reduce radicle and hypocotyl length of both species. 6-MBOA (6-methoxy-2,3-benzoxazolinone), a conversion product of 2-o-glucosyl-7-methoxy-1,4-benzoxazin-3-one, a hydroxamic acid in living wheat plants, inhibited germination and radicle and hypocotyl length of clover and morning glory. 6-MBOA, however, was not detected in wheat debris, stubble, or soil extracts. Total phenolic acids (FC) in extracts were determined with Folin and Ciocalteu's phenol reagent. Levels of FC in wheat-conventionaltill soil extracts were not related to germination or radicle and hypocotyl length of either species. Levels of FC in wheat-no-till soil extracts were also not related to germination of clover or morning glory, but were inversely related to radicle and hypocotyl length of clover and morning glory. FC values, solute potential, and acidity of wheat-no-till soil extracts appeared to be independent (additive) in action on clover radicle and hypocotyl length. Radicle and hypocotyl length of clover was inversely related to increasing FC and solute potential and directly related to decreasing acidity. Biological activity of extracts was determined best from slopes of radicle and hypocotyl length obtained from bioassays of extract dilutions. Thus, data derived from the water-autoclave extraction procedure, FC analysis, and slope analysis for extract activity in conjunction with data on extract pH and solute potential can be used to estimate allelopathic activity of wheat-no-till soils
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    A moderately repeated DNA sequence of wheat and rye genomes (1992)
    Springer
    Plant molecular biology 18 (1992), S. 603-605 
    Details
    ISSN: 1573-5028
    Keywords: ARS-related DNA repeat ; DNA sequence ; Secale cereale ; Triticum aestivum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A 371 base pair segment (bordered by Hind III and Eco RI cutting sites) of wheat embryo nuclear DNA has been cloned and sequenced. It is AT-rich (68%), shares some sequence features with autonomously replicating sequence (ARS) elements, and occurs in approximately 7600 copies per haploid genome. When used as probe for blot hybridization to Hind III-digested wheat DNA, it gives an irregular series of hybridization bands. Essentially the same hybridization pattern was observed for rye DNA. It is concluded that this segment is distributed irregularly but, apparently, according to the same rule in both wheat and rye genomes.
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    Nucleotide sequence of a nuclear tRNATyr gene from Triticum aestivum (1992)
    Springer
    Plant molecular biology 18 (1992), S. 1207-1208 
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    ISSN: 1573-5028
    Keywords: Triticum aestivum ; nuclear tRNATyr gene ; DNA sequence ; transcription ; processing ; splicing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
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    URL: http://dx.doi.org/10.1007/BF00047729
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    Nucleotide sequence of the internal transcribed spacer region of rDNA in wheat,Triticum aestivum L. (Gramineae) (1992)
    Springer
    Plant molecular biology 20 (1992), S. 159-160 
    Details
    ISSN: 1573-5028
    Keywords: rRNA ; PCR ; ITS ; DNA sequence ; nucleotide ; Triticum aestivum ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
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    URL: http://dx.doi.org/10.1007/BF00029159
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    Sequence and organization of a 7.2 kb region of wheat mitochondrial DNA containing the large subunit (26S) rRNA gene (1992)
    Springer
    Plant molecular biology 20 (1992), S. 347-352 
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    ISSN: 1573-5028
    Keywords: mitochondrial DNA ; repeated sequences ; ribosomal RNA ; t-elements ; Triticum aestivum ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We report the sequence of a 7.2 kilobase pair DNA fragment containing a copy of the wheat mitochondrial gene (rrn26) that encodes the mitochondrial large-subunit ribosomal RNA (26S rRNA). The mature 26S rRNA was determined by direct RNA sequencing to be 3467 nucleotides long, and to share a 5′-terminal pentanucleotide (5′-AUCAU), thought to be important in post-transcriptional processing, with the wheat mitochondrial small-subunit (18S) rRNA. Two other prominent features of the sequence were noted. First, upstream of rrn26 are located two tandem copies of a 70 base pair element containing a putative mitochondrial promoter motif (TCGTATAAAAA). Second, downstream of rrn26 is a sequence element that, if transcribed, would produce and RNA with a secondary structure resembling that of tRNAs but differing sufficiently from the latter structure to preclude any transcript from functioning normally in translation. These upstream and downstream sequence elements may play a role in the expression of rrn26 in wheat mitochondria.
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    The wheat mitochondrial genome contains an ORF showing sequence homology to the gene encoding the subunit 6 of the NADH-ubiquinone oxidoreductase (1992)
    Springer
    Plant molecular biology 20 (1992), S. 395-404 
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    ISSN: 1573-5028
    Keywords: mitochondria ; nad6 ; NADH-ubiquinone reductase ; Triticum aestivum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A region of the mitochondrial (mt) DNA of wheat was studied because of its homology with other plant mtDNAs. Sequence analysis revealed an open reading frame encoding a polypeptide of 247 amino acids. Comparison of the sequence of the putative polypeptide with the protein sequence data of the Swiss-Prot library reveals homology with subunit 6 of the NADH-ubiquinone complex of mitochondria from Marchantia polymorpha, Podospora anserina, Chlamydomonas reinhardtii and of chloroplasts from M. polymorpha and Oryza sativa. No similarity was detected when compared with the subunit 6 of animal mitochondria, probably due to the rapid evolution of the sequence. A single 1.2 kb transcript appears in northern RNA blots. We found 15 edited sites of which only 13 give amino acid changes. This is the first report of a mt nad6 gene in higher plants.
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    Differences in the heat-shock response between thermotolerant and thermosusceptible cultivars of hexaploid wheat (1992)
    Springer
    Theoretical and applied genetics 84 (1992), S. 941-946 
    Details
    ISSN: 1432-2242
    Keywords: Triticum aestivum ; Genetic differences ; Heat-shock proteins ; Heat-shock response ; DNA polymorphism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Heat-shock protein (HSP) gene expression in two wheat lines cv ‘Mustang’ (heat-tolerant) and cv ‘Sturdy’ (heat-susceptible) were analyzed to determine if wheat genotypes differing in heat tolerance also differ in in-vitro HSP synthesis (translatable HSP mRNAs) and steady-state levels of HSP mRNA. Several sets of mRNA were isolated from seedling leaf tissues which had been heat-stressed at 37 °C for various time intervals. These mRNAs were hybridized with HSP cDNA or genomic DNA probes (HSP17, 26, 70, 98, and ubiquitin). Protein profiles were compared using in-vitro translation and 2-D gels. The Northern slot-blot data from the heat-stress treatment provide evidence that the heat-tolerant cv ‘Mustang’ synthesized low molecular weight (LMW) HSP mRNA earlier during exposure to heat shock and at a higher level than did the heat-susceptible cv ‘Sturdy’. This was especially true for the chloroplast-localized HSP. The protein profiles shown by 2-D gel analysis revealed that there were not only quantitative differences of individual HSPs between the two wheat lines, but also some unique HSPs which were only found in the ‘Mustang’ HSP profiles. The high level of RFLP between the two wheat lines was revealed by Southern blot hybridization utilizing a HSP17 probe. These data provide a molecular basis for further genetic analysis of the role of HSP genes in thermal tolerance in wheat.
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    The modification of a common wheat-Thinopyrum distichum translocated chromosome with a locus homoeoallelic to Lr19 (1992)
    Springer
    Theoretical and applied genetics 85 (1992), S. 73-78 
    Details
    ISSN: 1432-2242
    Keywords: Triticum aestivum ; Intergeneric gene transfer ; Allosyndetic recombination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The ‘Chinese Spring’ ph1b and ph2b mutants, as well as the nulli 5B tetra 5D stock were utilized in an attempt to effect homoeologous chromatin exchange between the ‘Indis’ chromosome translocation [derived from Thinopyrum distichum (Thunb.) Löve] and chromosome arm 7DL of common wheat. A homoeoallele of Lr19 and linked genes for yellow flour-pigmentation were utilized as markers. Seven selections with recombinations involving the foreign, translocated segment were recovered. Four of these had white endosperms and were leaf-rust resistant. The remaining lines were leaf-rust resistant and had levels of endosperm pigmentation intermediate to those of ‘Indis’ and ‘Chinese Spring’. The recombined translocation segments coding for white endosperm are no longer associated with chromosome 7D. The original translocated segment may, therefore, not be fully homoeologous to 7DL. The recombinants with white endosperm also lack the stem-rust resitance gene Sr25, but retained the segregation distorter locus, Sd-1. However, it seems as though an enhancer locus (or loci) of Sd-1 had been lost.
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    A comparative evaluation of two methods of selecting locations used for testing spring wheat cultivars (1992)
    Springer
    Theoretical and applied genetics 83 (1992), S. 301-304 
    Details
    ISSN: 1432-2242
    Keywords: Triticum aestivum ; Genotype ; Environment interactions ; Cluster analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary One of the considerations of regional cultivar evaluation programs is to optimize the number of locations used for testing. Although optimization of numbers of locations using cluster analysis has been previously attempted, no objective comparison of methods has yet been made. A new clustering method that uses the pairwise contribution of locations to the cultivar x location mean square as the distance measure (LB) was compared to another method that employs diallel correlations as the distance measure (CL). Data from six spring wheat (Triticum aestivum L. em Thell) cultivars grown at 13 locations for five years were used in the initial cluster analysis. Another set of data, from a separate year, consisting of yields of the original 6 cultivars and a set of 12 independent cultivars was then used to check the validity of the original groupings and to compare the two methods. When the 6 original cultivars were considered, the LB technique was found to be superior to the CL. When the 12 independent cultivars were used, neither method was considered to be superior. Because of the lack of flexibility on the part of the LB method, neither technique could be deemed as fully adequate.
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    Dosage response of rye genes in a wheat background (1992)
    Springer
    Theoretical and applied genetics 84 (1992), S. 1-5 
    Details
    ISSN: 1432-2242
    Keywords: Triticum aestivum ; Secale cerale ; Alien gene expression ; Endosperm protein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A series of hexaploid wheat lines containing zero, two or four doses of rye chromosome arm 1RS was used to investigate the response to changes in dosage by the rye genes when in a wheat background. The quantity of protein produced by the secalin protein genes contained on 1RS was directly related to the number of copies of 1RS present in the line. No response could be detected by representative wheat proteins suggesting that the increase in secalin protein observed was due to an increase in mRNA produced when four copies of the secalin gene was present. These results suggest that increasing the dosage of alien genes introgressed into wheat may be a useful tool for enhancing their expression. Mention of a trade name or proprietary product does not constitute a guarantee, warranty or recommendation of the product by the U.S. Department of Agriculture or the University of Missouri and does not imply its approval to the exclusion of other products that may be suitable.
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    Use of the polymerase chain reaction to detect spacer size heterogeneity in plant 5S-rRNA gene clusters and to locate such clusters in wheat (Triticum aestivum L.) (1992)
    Springer
    Theoretical and applied genetics 83 (1992), S. 684-690 
    Details
    ISSN: 1432-2242
    Keywords: PCR ; 5S-ribosomal RNA ; Non-transcribed spacer ; Triticum aestivum ; Chromosome location
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We have used the polymerase chain reaction to analyse variation in the size of individual 5S-ribosomal gene spacer sequences. This reaction can be used to demonstrate inter- and intraspecific variation in spacer size, and combined with DNA sequencing it may thus be a valuable taxonomic tool. Two sets of nested polymerase chain reaction primers were designed to amplify the nontranscribed spacer DNA between repeated 5S-rRNA genes. These “universal” primers were used to generate fragments from the genomic DNA from several unrelated monocotyledonous plants. Ribosomal RNA spacer sequences generated in these experiments could also be used to locate 5S-rRNA gene clusters on specific chromosomes in hexaploid wheat (Triticum aestivum). Three distinct spacer sizes were observed after amplification. These were assigned locations on chromosomes by analysing amplification products of genomic DNA from nullisomic/tetrasomic and ditelosomic wheat stocks. “Large” 508-bp 5S repeats are located on the short arm of chromosome 5B and “short” 416-bp and 425-bp repeat unit variants are located on the short arms of chromosomes 1B and 1D, respectively. No other loci were detected. The spacer fragments were cloned, sequenced, and shown to be homologous to wheat 5S-rRNA spacers previously identified. Spacers of uniform size but with some sequence heterogeneity were shown to be located at each locus.
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    Geographical variation in heading characters among wheat landraces, Triticum aestivum L., and its implication for their adaptability (1992)
    Springer
    Theoretical and applied genetics 84 (1992), S. 259-265 
    Details
    ISSN: 1432-2242
    Keywords: Heading characters ; Geographical variation ; Adaptation strategy ; Genetic resource ; Triticum aestivum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Heading time and its constituent traits, photoperiodic response, narrow-sense earliness and vernalization requirement, were surveyed for 158 wheat landraces. Wide varietal variation was observed in each character. Nearly half of the variation for each character was explained by a geographical difference in origin. Based on these data and the growing environments in each locality, we analyzed “adaptation strategy”, seen as the adjustment of heading time in terms of differences in the constituent traits, both individually and combined. The difference among localities indicated that wheat landraces had been selected for early heading as an adaptation strategy to water stress and/or high temperature in early summer. This change was caused by a reduction in photoperiodic response and narrow-sense earliness. The vernalization requirement was also reduced for adaptation to relatively mild winters. Adaptation strategy deduced from the variation within each locality was also different amongst localities. In the central region of wheat evolution, where wide variations existed in both photoperiodic response and narrow-sense earliness, the late-heading trait was achieved by either one of these traits individually or both of them combined. On the contrary, in the eastern and the western regions, wide variation in heading time was achieved by the unique combination of photoperiodic response and narrowsense earliness. A sampling strategy for wheat germ plasm is also discussed.
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    URL: http://dx.doi.org/10.1007/BF00229480
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    Isozyme and cytological markers of some Psathyrostachys juncea accessions (1992)
    Springer
    Theoretical and applied genetics 84 (1992), S. 528-534 
    Details
    ISSN: 1432-2242
    Keywords: Psathyrostachys juncea ; Triticum aestivum ; Isozyme markers ; Chromosome banding ; Intergeneric hybridization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Psathyrostachys juncea (synonymous to Elymus junceus; 2n=2x=14, NN) has unique biotic and abiotic attributes that could contribute towards wheat improvement. The effectiveness of such an intergeneric hybridization program depends greatly on being able to establish diagnostic markers of the alien chromosomes. Isoelectric focusing (IEF) analyses of six enzyme systems have identified five biochemical markers — malate dehydrogenase (MDH), esterase (EST), shikimate dehydrogenase (SKDH), phosphoglucomutase (PGM), and β-amylase (β-AMY) — to be of positive diagnostic value; glucosephosphate isomerase (GPI) banding profiles were of no definite value in the background of Triticum aestivum cvs ‘Chinese Spring’ and ‘Seri-82’, the potential recipients of Ps. juncea chromosomes. The Giemsa C-banding karyotype distinctively separates the Ps. Juncea chromosomes from each other and from those of T. aestivum with little banding site polymorphisms prevalent among its accessions analyzed, indicating the usefulness of C-bands as cytological markers.
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    URL: http://dx.doi.org/10.1007/BF00224148
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    Production and cytogenetic analysis of BC1, BC2, and BC3 progenies of an intergeneric hybrid between Triticum aestivum (L.) Thell. and tetraploid Agropyron cristatum (L.) Gaertn. (1992)
    Springer
    Theoretical and applied genetics 84 (1992), S. 698-703 
    Details
    ISSN: 1432-2242
    Keywords: Triticum aestivum ; Agropyron ; Intergeneric hybrids ; Backcross derivatives ; Chromosome pairing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Intergeneric hybrids between Triticum aestivum cv ‘Chinese Spring’ and Agropyron cristatum 4x (2n= 5x=35, ABDPP genomes) with a high level of homoeologous meiotic pairing between the wheat chromosomes were backcrossed 3 times to wheat. Pollination of the F1 hybrid with ‘Chinese Spring’ resulted in 22 BC1 seeds with an average seed set of 1.52%. Five BC1 plants with 39–41 chromosomes were raised using embryo rescue techniques. Chromosome pairing in the BC1 was characterized by a high frequency of multivalent associations, but in spite of this there was no evidence of homoeologous pairing between chromosomes of wheat and those of Agropyron. All of the plants were self sterile. The embryo rescue technique was again essential to produce 39 BC2 plants with chromosome numbers ranging from 37 to 67. The phenomenon of meiotic non-reduction was also observed in the BC3 progenies. In this generation male and female fertility greatly increased, and meiotic pairing was fairly regular. Some monosomic (2n=43) and double monosomic (2n=44) lines were produced. Analysis of these progenies should permit the extraction of the seven possible wheat-Agropyron disomic addition lines including those with the added chromosomes carrying the genes involved in meiotic non-reduction and in suppression of Ph activity.
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    URL: http://dx.doi.org/10.1007/BF00224171
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    Relation between growth conditions and dormancy of seed potatoes. 1. Effects of nitrogen (1992)
    Springer
    Potato research 35 (1992), S. 355-364 
    Details
    ISSN: 1871-4528
    Keywords: cultivar ; nitrate ; nitrogen ; Solanum tuberosum L. ; tuber
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The duration of dormancy of seed potatoes varies between years and between origins. Therefore, the effects of conditions during crop growth on dormancy of progeny tubers were studied. The effect of nitrogen during tuber bulking on the duration of dormancy was investigated in three field experiments with two cultivars. In addition to an application of 125 kg N/ha at planting, top dressings of 0–150 kg N/ha were given about 2 weeks after tuber initiation. Haulm was pulled about 4 weeks later. The effect of nitrogen rate at planting was also examined in one experiment. Nitrogen top dressings shortened dormancy in all experiments by 5–8 days. An increased nitrogen rate at planting resulted in a shorter dormancy when the duration of dormancy was expressed in days after tuber initiation, but not when it was expressed in days after haulm pulling, probably because extra nitrogen also delayed tuber initiation.
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    URL: http://dx.doi.org/10.1007/BF02357592
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    Relation between growth conditions and dormancy of seed potatoes. 2. Effects of temperature (1992)
    Springer
    Potato research 35 (1992), S. 365-375 
    Details
    ISSN: 1871-4528
    Keywords: cultivar ; heat sprouting ; nitrogen ; second growth ; Solanum tuberosum L. ; sprout ; tuber
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary In two indoor experiments under short day conditions, the effect of temperature during tuber bulking on dormancy of tubers was investigated for cvs Diamant and Désirée. Temperature treatments started after tuber initiation and lasted for 4 weeks, after which the haulm was removed. In Experiment 1, the day/night temperature regimes 18/12, 22/22, 26/18 and 32/12 °C (T18/12 etc.) were compared. In Experiment 2, three day temperatures (18, 24 and 30 °C) were combined with three night temperatures (12, 18 and 24 °C), resulting in nine treatments. The dormancy of cv. Diamant was shortest after very high day temperatures (30–32 °C), but intermediate day temperatures (22–26 °C) had no shortening effect compared to T18/12. Dormancy of cv. Désirée was not shortened, but rather tended to be prolonged by high temperatures (22–32 °C) during growth. High temperatures during growth resulted in more sprouts per tuber after dormancy had ended.
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    The structure of the SF6 molecule and the SF 6 − anion excited states (1992)
    Springer
    Russian chemical bulletin 41 (1992), S. 504-510 
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    ISSN: 1573-9171
    Keywords: electronic structure ; geometry optimization ; electron affinity ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The electronic and geometric structures of the ground state and a number of excited states of the SF6 molecule and the SF 6 − anion have been calculated by the discrete-variation method of the local density-functionals. The anion was found to possess a number of states stable toward the outer electron detachment, and at least one excited state stable toward dissociation. The adiabatic electron affinity (EA) was determined as 3.46 eV at the highest level of theory. This result is correlated to the high EAs of the isovalent compound SeF6 and TeF6; however, it does not agree with the presently accepted experimental estimate of 1.0 ± 0.2 eV for the SF6EA value. The basic anion configuration is octahedral with a S-F bond length of 1.717 Å. The calculated limit for the highest dissociation channel of the ground state SF 6 − → SF 5 − + F is ≈ 1.5 eV lower than the minimum of the total energy of the neutral molecule; this is in good agreement with experimental estimates.
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    The 5S DNA units of bread wheat (Triticum aestivum) (1992)
    Springer
    Plant systematics and evolution 183 (1992), S. 183-194 
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    ISSN: 1615-6110
    Keywords: Poaceae ; Triticum aestivum ; 5S DNA sequences ; chromosomal5S Dna loci ; wheat evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A collection of 44 cloned 5S DNA units fromTriticum aestivum cv. ‘Chinese Spring’ were grouped into 12 sequence-types based on sequence similarity and the respective consensus sequences were then produced. The relationship between these 12 consensus sequences (T. aestivum S 1-S 8 andT. aestivum L 1-L 4), together with two clones sequenced byGerlach andDyer, and the 5S DNA consensus sequences from diploidTriticum spp. were then determined by numerical methods. Both phenetic and cladistic analyses were carried out. The following wheat 5S DNA sequences were found to group with respective sequences from diploidTriticum spp.:T. aestivum S 4, S 6 withT. tauschii S;T. aestivum S 3 withT. monococcum S andT. monococcum S-Rus 7;T. aestivum L 1 andT. aestivum L-G&D withT. speltoides L;T. aestivum L 2, L 3 withT. tauschii L;T. aestivum L 4 withT. monococcum L andT. monococcum L-Rus 12. The analyses suggested that 5 out of the 65S Dna loci present in wheat were identified at the sequence level. The locus that could not be identified in this analysis was the5S Dna-B 1 locus. A group ofT. aestivum sequences (T. aestivum S 1, S 7, S 8, S-G&D) were found to be distinct from the other 5S DNA sequences in the data base. The existence of the distinct group of 5S DNA sequences suggests that there is a gap in our current understanding of wheat evolution with respect to the5S Dna loci.
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    URL: http://dx.doi.org/10.1007/BF00940802
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    The vibration and stability analysis of moderate thick plates by the method of lines (1992)
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    Applied mathematics and mechanics 13 (1992), S. 523-531 
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    ISSN: 1573-2754
    Keywords: moderate thick plate ; vibration ; stability ; method of lines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Mathematics , Physics
    Notes: Abstract The method of lines based on Hu Hai-chang's theory for the vibration and stability of moderate thick plates is developed. The standard nonlinear ordinary differential equation (ODE) system for natural frequencies and critical load is given by use of ODE techniques, and then any indicated eigenvalue could be obtained directly from ODE solver by employing the so-called initial eigenfunction technique instead of the mode orthogonality condition. Numerical examples show that the present method is very effective and reliable.
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    URL: http://dx.doi.org/10.1007/BF02451515
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    Changes in fatty acids, amino acids and carbon/nitrogen biomass during nitrogen starvation of ammonium- and nitrate-grownIsochrysis galbana (1992)
    Springer
    Journal of applied phycology 4 (1992), S. 95-104 
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    ISSN: 1573-5176
    Keywords: amino acids ; biomass ; fatty acids ; Isochrysis ; nitrogen ; starvation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Growth of cells ofIsochrysis galbana with either nitrate or ammonium as the N-source, and the effects of subsequent N-starvation of these cells, were compared. During exponential N-sufficient growth nitrate-grown cells had double the fatty acid content of the ammonium-grown cells but lower concentrations of a few amino acids. Following resuspension in N-free medium the fatty acid content of the ammonium-grown cells increased to that of the nitrate-grown cells, but there was no further increase in fatty acid content on a C-biomass or cellular basis during the following 4 days for either culture. Fatty acid synthesis was continuous during N-starvation, while it occurred during the light-phase only in exponential growth. The proportion of 18:1n9 fatty acid increased from 10 to 25% total fatty acids during N-starvation. Intracellular free amino acid content decreased in a similar manner in both cultures on N-starvation, the ratio of intracellular free amino-N/cell-C falling more rapidly than overall cellular N/C. It was concluded that optimal amino acid and fatty acid content would be attained by growth in the presence of excess nitrate. Measurements of chlorophyll and carotenoid content and ofin vivo fluorescence indicated that these parameters had potential for monitoring the C and N biomass in cultures grown under relatively constant (not necessarily continuous) illumination.
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    Adaptive foraging by predators as a cause of predator-prey cycles (1992)
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    Evolutionary ecology 6 (1992), S. 56-72 
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    ISSN: 1573-8477
    Keywords: dynamics of adaptation ; optimal foraging ; predator-prey cycles ; stability ; type-2 functional response
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary When foraging has costs, it is generally adaptive for foragers to adjust their foraging effort in response to changes in the population density of their food. If effort decreases in response to increased food density, this can result in a ‘type-2’ functional response; intake rate increases in a negatively accelerated manner as prey density increases. Unlike other mechanisms for type-2 responses, adaptive foraging usually involves a timelag, because foraging behaviours do not often change instantaneously with changes in food density or risks. This paper investigates predator-prey models in which there are explicit dynamics for the rate of adaptive change. Models appropriate to both behavioural and evolutionary change are considered. Both types of change can produce cycles under similar circumstances, but under some evolutionary models there is not sufficient genetic variability for evolutionary change to produce cycles. If there is sufficient variability, the remaining conditions required for cycles are surprisingly insensitive to the nature of the adaptive process. A predator population that approaches the optimum foraging strategy very slowly usually produces cycles under similar conditions as does a very rapidly adapting population.
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    URL: http://dx.doi.org/10.1007/BF02285334
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    5S ribosomal gene clusters in wheat: pulsed field gel electrophoresis reveals a high degree of polymorphism (1992)
    Springer
    Molecular genetics and genomics 232 (1992), S. 215-220 
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    ISSN: 1617-4623
    Keywords: 5S ribosomal genes ; Triticum aestivum ; Pulsed field gel electrophoresis ; Genetic fingerprinting ; Hypervariability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The long-range structure of 5S rRNA gene clusters has been investigated in wheat (Triticum aestivum L.) by means of pulsed field gel electrophoresis. Using aneuploid stocks, 5S rRNA gene clusters were assigned to sites on chromosomes 1B, 1D, 513 and 5D. Cluster sizes were evaluated and the copy number of 5S DNA repeats was estimated at 4700-5200 copies for the short repeating unit (410 bp) and about 3100 copies for the long repeat (500 bp) per haploid genome. A comparison of wheat cultivars revealed extremely high levels of polymorphism in the 5S rRNA gene clusters. With one restriction enzyme digest all varieties tested gave unique banding patterns and, on a per fragment basis, 21-fold more polymorphism was detected among cultivars for 5S DNA compared to standard restriction fragment length polymorphisms (RFLPs) detected with single copy clones. Experiments with aneuploid stocks suggest that the 5S rRNA gene clusters at several chromosomal sites contribute to this polymorphism. A number of previous reports have shown that wheat cultivars are not easily distinguished by isozymes or RFLPs. The high level of variation detected in 5S rRNA gene clusters therefore offers the possibility of a sensitive fingerprinting method for wheat. 5S DNA and other macro-satellite sequences may also serve as hypervariable Mendelian markers for genetic and breeding experiments in wheat.
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    URL: http://dx.doi.org/10.1007/BF00279999
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    Growth and mineral nutrition of six rapid-cycling Brassica species in response to seawater salinity (1992)
    Springer
    Plant and soil 139 (1992), S. 285-294 
    Details
    ISSN: 1573-5036
    Keywords: Brassica ; B. campestris ; B. carinata ; B. juncea ; B. naptus ; B. nigra ; B. oleracea ; calcium ; chloride ; potassium ; magnesium ; nitrogen ; sodium ; nutrients ; salinity ; salt-tolerance ; seawater
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The growth of six rapid-cycling lines of Brassica species, B. napus, B. campestris, B. nigra, B. juncea, B. oleracea and B. carinata was inhibited by seawater salinity. Based on the change in dry matter reduction relative to the control at varying concentrations of salts (4, 8 and 12 dS m-1), the relative salt tolerance of these species was evaluated. B. napus and B. carinata were the most tolerant and most sensitive species, respectively, while the other four species were moderately tolerant. The influence of seawater on the concentrations of 12 elements including macronutrients and micronutrients in the shoots of these Brassica plants was characterized to determine the relationship between nutritional disturbance and relative salt tolerance. It was found that seawater salinity had a significant effect on the concentrations of Ca, Mg, K, Cl, Na and total N in the shoots of these plants but only the change in Ca concentration was significantly related to the relative salt tolerance of these six rapid-cycling Brassica species according to a rank analysis of the data. This finding indicates that Ca may play a regulatory role in the responses of Brassica species to saline conditions.
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    URL: http://dx.doi.org/10.1007/BF00009320
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    Nitrogen and phosphorus cycling in relation to stand age of Ecucalyptus regnans F. Muell (1992)
    Springer
    Plant and soil 142 (1992), S. 157-166 
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    ISSN: 1573-5036
    Keywords: Acacia ; Eucalyptus regnans ; decomposition ; litterfall ; nitrogen ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The N and P contents of the litter layer and the return of these nutrients in litterfall were measured in seven stands of Mountain Ash (Eucalyptus regnans) ranging in age from 5 years to about 250 years. Both annual litterfall and nutrient return were correlated with stand basal area and were high compared with other productive eucalypt forests. In contrast, the fall of dead eucalypt leaves was constant with stand age, demonstrating that sites are fully occupied at an early age. Similarly, amounts of N and P in total leaf fall (overstorey plus understorey) were constant with stand age, except for low amounts in the stand aged 40 years where Acacia spp., important fixers of atmospheric N, were not prevalent. The decomposition constant (k) of organic matter in the litter layer decreased with stand age, from 0.31 year-1 at age 5 years to 0.23 year-1 at age 250 years. These constants also applied to N and P, indicating a tight coupling between organic matter decomposition and release of these nutrients from litter. The litter layer released about 30 kg ha-1 of N at age 5 years, and about 70 kg ha-1 at age 80 years. These results are discussed in relation to growth of Mountain Ash following fire, and the subsequent retention and accumulation of N during stand development.
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    Nitrogen and phosphorus cycling in relation to stand age of Eucalypus regnans F. Muell. (1992)
    Springer
    Plant and soil 142 (1992), S. 167-176 
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    ISSN: 1573-5036
    Keywords: Eucalyptus regnans ; mineralization ; nitrification ; nitrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Laboratory and in situ rates of N mineralization in soils from Mountain Ash (Eucalyptus regnans) forests were measured fortnightly for two years in stands aged 9, 40, 80 and about 250 years (overmature), and for one year in stands aged 5 and 46 years. Rates of anaerobic mineralization (the laboratory test) showed little seasonal or annual variation. In contrast, rates of in situ mineralization varied markedly with season, being highest in spring and summer. Anaerobic mineralization was highly correlated with stand age to 80 years, but decreased between ages 80 and 250 years. In situ mineralization also decreased between these two ages, but otherwise was not related to stand age. Hence, the correlation between anaerobic and in situ mineralization along the age sequence was weak, suggesting that the anaerobic test is of maximum utility when this pool is in balance with inputs from decomposing litter (‘steady-state’ ecosystems). Nitrification was strong in stands aged 9, 46, 80 and 250 years and weak in stands aged 5 and 40 years. Within stands, the rate of nitrification during each period of in situ containment was highly dependent on the supply of NH4 ions. Between stands, annual rates of nitrification appear to be related to the balance between the N capital of the site, its rate of turnover, and the demand for N by heterotrophs and vegetation so that if NH4 supply is depleted, little is left for autotrophic nitrifiers.
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    The influence of nitrogen concentration and ammonium/nitrate ratio on N-uptake, mineral composition and yield of citrus (1992)
    Springer
    Plant and soil 147 (1992), S. 13-23 
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    ISSN: 1573-5036
    Keywords: ammonium ; citrus ; nitrate ; NO3 −/NH4 + ratio ; nitrogen ; nutrient solution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In short-term water culture experiments with different 15N labeled ammonium or nitrate concentrations, citrus seedlings absorbed NH4 + at a higher rate than NO3 −. Maximum NO3 − uptake by the whole plant occurred at 120 mg L−1 NO3 −-N, whereas NH4 + absorption was saturated at 240 mg L−1 NH4 +-N. 15NH4 + accumulated in roots and to a lesser degree in both leaves and stems. However, 15NO3 − was mostly partitioned between leaves and roots. Adding increasing amounts of unlabeled NH4 + (15–60 mg L−1 N) to nutrient solutions containing 120 mg L−1 N as 15N labeled nitrate reduced 15NO3 − uptake. Maximum inhibition of 15NO3 − uptake was about 55% at 2.14 mM NH4 + (30 mg L−1 NH4 +-N) and it did not increase any further at higher NH4 + proportions. In a long-term experiment, the effects of concentration and source of added N (NO3 − or NH4 +) on nutrient concentrations in leaves from plants grown in sand were evaluated. Leaf concentration of N, P, Mg, Fe and Cu were increased by NH4 + versus NO3 − nutrition, whereas the reverse was true for Ca, K, Zn and Mn. The effects of different NO3 −-N:NH4 +-N ratios (100:0, 75:25, 50:50, 25:75 and 0:100) at 120 mg L−1 total N on leaf nutrient concentrations, fruit yield and fruit characteristics were investigated in another long-term experiment with plants grown in sand cultures. Nitrogen concentrations in leaves were highest when plants were provided with either NO3 − or NH4 + as a sole source of N. Lowest N concentration in leaves was found with a 75:25 NO3 −-N/NH4 +-N ratio. With increasing proportions of NH4 + in the N supply, leaf nutrients such as P, Mg, Fe and Cu increased, whereas Ca, K, Mn and Zn decreased. Yield in number of fruits per tree was increased significantly by supplying all N as NH4 +, although fruit weight was reduced. The number of fruits per tree was lowest with the 75:25 NO3 −-N:NH4 +-N ratio, but in this treatment fruits reached their highest weight. Rind thickness, juice acidity, and colour index of fruits decreased with increasing NH4 + in the N supply, whereas the % pulp and maturity index increased. Percent of juice in fruits and total soluble solids were only slightly affected by NO3 −:NH4 + ratio.
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    Carbohydrate and nitrogen sources affect respectively in vitro germination of immature ovules and early seedling growth of Impatiens platypetala Lindl. (1992)
    Springer
    Plant cell, tissue and organ culture 31 (1992), S. 211-214 
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    ISSN: 1573-5044
    Keywords: carbohydrate ; germination ; Impatiens L. ; Impatiens platypetala L. ; nitrogen ; tissue culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In vitro germination of 20-day old immature ovules of Impatiens platypetala Lindl. was inhibited at concentrations as low as 50 mM sucrose or mannitol and 100 mM glucose. Younger ovules (12, 14, and 16 days old) were similarly inhibited at 100 mM sucrose. Inorganic nitrogen concentration did not affect germination regardless of ovule age, but seedling fresh weight was significantly less and abnormal development of seedlings was significantly increased by total inorganic nitrogen concentrations higher or lower than 30 mM (at a ratio of 20: 10 mM NO3 -: NH4 +) in the culture medium.
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    Genetic control of a response to the segregation distortion allele, Sd-1d, in the common wheat line ‘Indis’ (1992)
    Springer
    Euphytica 60 (1992), S. 89-95 
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    ISSN: 1573-5060
    Keywords: cuckoo effect ; gametocidal chromosome/gene ; preferential transmission ; Triticum aestivum ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A translocated chromosome segment, derived from Thinopyrum distichum, carries the leaf rust resistance allele Lr19d and a segregation distorter allele, Sd-1d. In translocation heterozygotes, male and female gametophytes lacking the translocation are aborted, the severity of the effect depending on the genotype of the hybrid. The selective abortion of the gametophytes with a normal chromosome 7D appears to be based on the absence of the translocated chromosome rather than the presence of the normal chromosome. The magnitude of the gametocidal response, elicited by Sd-1d, is under multigenic control. A number of chromosomes, the individual effects of which are generally small, may act to suppress or promote the response. Chromosome arms 2AL, 2BL, 5BL and 5DL of ‘Chinese Spring’ were found to reduce sensitivity to the presence of the gametocidal chromosome. Chromosome 3B of ‘Inia 66-1’ also reduce the gametocidal response while chromosome arm 6DS of ‘Chinese Spring’ may promote the effect
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    Genetic analysis and selection for wheat yield in drought-stressed and irrigated environments (1992)
    Springer
    Euphytica 62 (1992), S. 89-96 
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    ISSN: 1573-5060
    Keywords: Triticum aestivum ; wheat ; stress tolerance ; genetic variance ; genetic correlation ; selection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Wheat (Triticum aestivum L.) cultivars grown in the southern Great Plains of the U.S.A. are exposed to a wide range of moisture conditions due to large fluctuations in the amount and frequency of rainfall. Yield stability under those conditions is therefore a desirable trait for wheat breeders. Our primary objective was to quantify various genetic parameters for grain production in drought-stressed and irrigated environments. We also attempted to predict and measure yield responses when selection is practiced in either drought-stressed or irrigated environments, or both. Seventy F2-derived lines from the cross, TAM W-101/Sturdy, were evaluated at Goodwell, OK, under irrigated and naturally drought-stressed conditions in 1987 and 1988. Genetic variance and heritability estimates were higher in the irrigated environment than in the drought-stressed environment. The genetic correlation coefficient for yields in the two environments was 0.20±0.16, indicating that selection of widely adapted genotypes requires testing in both environments. Based on the genetic variance/covariance structure of this particular population, the linear index which maximized the combined expected gain in both environments was 0.66Y1 + 0.34Y2, in which Y1 and Y2 are yields in the irrigated and drought-stressed environments. This index is not expected to apply across all populations; rather, it further supports the hypothesis that testing in either environment alone (drought stressed or irrigated) may not be most effective for increasing either mean productivity or yield under drought stress.
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    URL: http://dx.doi.org/10.1007/BF00037933
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    Genotypic differences in wheat Al tolerance (1992)
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    Euphytica 62 (1992), S. 111-117 
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    ISSN: 1573-5060
    Keywords: aluminium ; root growth ; screening ; tolerance ; Triticum aestivum ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Aluminium tolerance of 83 genotypes from Croatian and Yugoslav Triticum aestivum germplasm was evaluated in nutrient solutions having Al3+ activities of 0, 12.5 and 25 μM. Relative root length (25 μM Al3+/0 Al) of various genotypes ranged from 2 to 97% (from very sensitive to tolerant to Al). No genotype with Al tolerance close to that of very tolerant cultivar Atlas-66 was found. Soil, climatic, fertilization, and liming effects that wheat plants giving seeds for the nutrient solution Al-tolerance screening had been subjected to during their growth cycle did not influence the Al-tolerance ranking. Significant correlation was found between screening wheat for Al tolerance in nutrient solutions and in acid Pseudogley soil amended with five rates of limestone in a greenhouse experiment. Seed protein concentration was significantly related to the Al-tolerance ranking (r2 = 0.962). Such a significant correlation was not obtained in a case of rheological and other quality characteristics of seeds. Al-tolerant wheat genotypes identified in this study will be used in breeding for improved Al tolerance.
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    URL: http://dx.doi.org/10.1007/BF00037936
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    Pre-emptive breeding to control wheat rusts (1992)
    Springer
    Euphytica 63 (1992), S. 103-113 
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    ISSN: 1573-5060
    Keywords: durable resistance ; genetic diversity ; pathogenic variation ; pre-emptive breeding ; Puccinia spp. ; resistance breeding ; Triticum aestivum ; wheat rust
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Pre-emptive or anticipatory breeding for resistance is breeding for resistance to future pathotypes. It is assumed that these will be derivatives of currently frequent pathotypes that need to mutate with respect to single host resistance genes in order to attack widely-grown cultivars. Success in this approach depends on relevant knowledge of the pathogenicity phenotypes and host resistance genes that occur throughout the wheat-growing areas. Because durability of resistance cannot be assumed, resistance breeding strategies are usually supported with the maintenance of genetic diversity to provide buffering against extreme crop losses in the event of significant pathogenic changes.
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    URL: http://dx.doi.org/10.1007/BF00023916
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    Adaptation of barley (Hordeum vulgare L.) to harsh Mediterranean environments (1992)
    Springer
    Euphytica 62 (1992), S. 29-38 
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    ISSN: 1573-5060
    Keywords: adaptation ; barley ; drought ; heading date ; plant ideotype ; principal component analysis ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Barley adapted to the combined stresses of low winter temperatures and terminal drought requires a medium carly heading date, little affected by environmental fluctuations. Two plant ideotypes that are adapted to terminal drought in Mediterranean environments can be distinguished. The first combines early heading with good early vigour, erect winter growth habit, light plant colour, and ability to recover from cold damage. The second combines medium early heading, prostrate winter growth habit, dark winter plant colour which changes to pale green in spring, and cold tolerance. This study was conducted to determine the relationship between consistency in heading date and plant ideotype, and to identify the usefulness of earliness and plant ideotype as criteria for indirect selection for grain yield under drought. Thirty-six two-rowed entries of barley (Hordeum vulgare L.) were sown at 15 environments in northern Syria. Average grain yields ranged from 7 to 331 g/m2; the range in average heading date was 20 days. Consistency in date of heading was related to the second ideotype through vernalization requirement. Early heading was positively correlated with grain yield in most of the environments, but especially in low-yielding environments. After eliminating the effect of heading date, the second plant ideotype was advantageous only under harsh conditions. In early generations, selection under favourable conditions for earliness, prostrate winter growth habit, dark winter plant colour, and cold tolerance is a useful alternative for yield testing, to identify material well adapted to environments experiencing low winter temperatures and terminal drought stress. Selection for the first plant ideotype is proposed for Mediterranean environments with mild winters.
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    URL: http://dx.doi.org/10.1007/BF00036084
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    Role of chromosome 3A in stomatal resistance of winter wheat (1992)
    Springer
    Euphytica 62 (1992), S. 59-62 
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    ISSN: 1573-5060
    Keywords: Triticum aestivum ; stomatal resistance ; chromosome 3A
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Leaf stomatal resistance, through transpiration and photosynthesis control, constitutes a major factor of productivity and adaptation in wheat. The aim of the investigations reported here was to identify chromosomal effects on the expression of the maximum stomatal resistance, determined under optimum conditions of irradiance and water supply. Leaf stomatal resistance was measured, on wheat grown in pots under natural and well-watered conditions, using a LI-COR LI-6200 portable photosynthesis system under a saturating light〉1400 μmol m-1 s-2. Reciprocal sets of chromosome substitution lines between two hard red winter wheat cultivars, Wichita and Cheyenne, were used to identify the chromosomes involved in the expression of this trait. The two parental cultivars were significantly different for the parameter investigated. Chromosome 3A appeared to be involved in the expression of the stomatal resistance value under optimum conditions. Taking into account the relationships previously established between this parameter and some agronomic traits, chromosome 3A might be involved directly in productivity-determining processes or in the adaptation to water conditions, in wheat.
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    URL: http://dx.doi.org/10.1007/BF00036088
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    Relationship between cold resistance, heading traits and ear primordia development of wheat cultivars (1992)
    Springer
    Euphytica 64 (1992), S. 123-130 
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    ISSN: 1573-5060
    Keywords: heading time ; narrow-sense earliness ; photoperiodic response ; Triticum aestivum ; vernalization requirement ; winter hardiness ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary For breeding early heading wheat cultivars with resistance to frost damage which are well adapted to dry areas of West Asia and North Africa, the relationships between winter hardiness, ear primordia development and heading traits, i.e. veernalization requirement, photoperiodic response and narrow-sense earliness, were assessed using a total of 30 genotypes of wheat (Triticum aestivum L.) grown in an experiment in Syria. The results of artificial freezing tests indicated that cultivars with good winter hardiness were to be found only in the winter wheat cultivars which required 50 or more days of vernalization treatment. These winter wheat cultivars did not initiate internode elongation without vernalization even at 95 days after planting. Thus their ear primordia were still underground and were protected from frost injury at this stage. Photoperiodic response and narrow-sense earliness were not associated with winter hardiness and earliness of internode elongation, but were related to the number of days to heading after planting. This indicated the possibility for breeding early heading cultivars with winter hardiness and tiller frost avoidance by combining high vernalization requirement, short narrow-sense earliness and neutral response to photoperiod.
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    URL: http://dx.doi.org/10.1007/BF00023545
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    Past, present and future opportunities in breeding for disease resistance, with examples from wheat (1992)
    Springer
    Euphytica 63 (1992), S. 3-22 
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    ISSN: 1573-5060
    Keywords: wheat ; Triticum aestivum ; yellow (stripe) rust ; Puccinia striiformis ; septoria ; Septoria tritici ; S. nodorum ; eyespot ; Pseudocercosporella herpotrichoides ; resistance genetics ; pathogen variation ; durable resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary This introductory chapter contains some general comments about plant breeding and breeding for disease resistance. The use of disease resistant crop plants is an environmentally favourable method of controlling disease but the process of breeding for disease resistance is subject to several constraints. Among them is the variability of pathogens in relation to host resistance. Some parts of this variation can be resolved into gene-for-gene interactions, but the boundaries within which such interactions can be detected are not sharp. The discussion of this variation is illustrated by reference to some important diseases of wheat, especially yellow rust, septoria and eyespot. The objective of obtaining durable resistance is discussed and some contributions of new genetical and molecular techniques to breeding for resistance are considered. It is suggested that new technology will enhance breeding for disease resistance but that established techniques of plant breeding will remain relevant and important.
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    URL: http://dx.doi.org/10.1007/BF00023908
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    Nitrate and ammonium as nitrogen sources for lupins prior to nodulation (1992)
    Springer
    Plant and soil 139 (1992), S. 247-251 
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    ISSN: 1573-5036
    Keywords: ammonium ; lupins ; nitrate ; nitrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Two cultivars of Lupinus angustifolius L. were grown in a glasshouse in solutions containing NO3 -, NH4 + or NH4NO3 with a total nitrogen concentration of 2.8 M m-3 in each treatment. One cultivar chosen (75A-258) was relatively tolerant to alkaline soils whereas the other (Yandee) was intolerant to alkalinity. Controlled experiments were used to assess the impact of cationic vs. anionic forms of nitrogen on the relative performance of these cultivars. Relative growth rates (dry weight basis) were not significantly different between the two cultivars when grown in the presence of NO3 -, NH4 + or NH4NO3. However, when NO3 - was supplied, there was a modest decline in relative growth rates in both cultivars over time. When plants grown on the three sources of nitrogen for 9 days were subsequently supplied with 15NH4NO3 or NH4 15NO3 for 30 h, NH4 + uptake was generally twice as fast as NO3 - uptake, even for plants grown in the presence of NO3 -. Low rates of NO3 - uptake accounted for the decrease in growth rates over time when plants were grown in the presence of NO3 -. It is concluded that the more rapid growth of 75A-258 than Yandee in alkaline conditions was not due to preferential uptake of NH4 + and acidification of the external medium. In support of this view, acidification of the root medium was not significantly different between cultivars when NH4 + was the sole nitrogen source.
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    URL: http://dx.doi.org/10.1007/BF00009316
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    Influence of plant nutrient concentration on growth rate: Use of a nutrient interruption technique to determine critical concentrations of N, P and K in young plants (1992)
    Springer
    Plant and soil 142 (1992), S. 221-233 
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    ISSN: 1573-5036
    Keywords: critical concentration ; deficiency ; diagnosis ; growth rate ; lettuce ; luxury consumption ; nitrogen ; nitrate ; nutrient requirement ; petiole sap ; phosphorus ; phosphate ; potassium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A method is described for determining the way in which growth rate varies with plant nutrient concentration using a simple nutrient interruption technique incorporating only 2 treatments. The method involves measuring the changes in growth and nutrient composition of otherwise well-nourished plants after the supply of one particular nutrient has been withheld. Critical concentrations are estimated from the relationship between the growth rate (expressed as a fraction of that for control plants of the same size which remained well-nourished throughout) and the concentration of the growth-limiting nutrient in the plants as deficiency developed. Trials of the method using young lettuce plants showed that shoot growth rate was directly proportional to total N (nitrate plus organic N) concentration, and linearly or near-linearly related to K and P concentration over a wide range; the corresponding relationship for nitrate was strongly curvi-linear. Critical concentrations (corresponding to a 10% reduction in growth rate) determined from these results were similar to critical values calculated from models derived from field data, but were generally higher than published estimates of critical concentration (based on reductions in shoot weight) for plants of a similar size. Reasons for these discrepancies are discussed. Nitrate, phosphate or potassium concentrations in sap from individual leaf petioles were highly sensitive to changes in shoot growth rate as deficiency developed, with the slope of the relationships varying with leaf position, due to differences both in their initial concentration and in the rates at which they were utilized in individual leaves. Each nutrient was always depleted more quickly in younger leaves than in older ones, providing earlier evidence of deficiency for diagnostic purposes. Although the plants were capable of accumulating nitrate, phosphate and potassium well in excess of that needed for optimum dry matter production during periods of adequate supply, the rate of mobilization of these reserves was insufficient to prevent reductions in growth rate as the plants became deficient. This brings into question the validity of the conventional concept that luxury consumption provides a store of nutrients which are freely available for use in times of shortage. The implications of these results for the use of plant analysis for assessing plant nutrient status are discussed.
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    URL: http://dx.doi.org/10.1007/BF00010968
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    The effect of nitrogen fertilizer and irrigation on black point incidence in soft white spring wheat (1992)
    Springer
    Plant and soil 140 (1992), S. 41-47 
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    ISSN: 1573-5036
    Keywords: Alternaria alternata ; black point ; fertilization ; irrigation ; nitrogen ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Agronomic studies were conducted to examine the effect of fertilizer N on black point incidence in Fielder soft white spring wheat (Triticum aestivum L. em Thell.). Black point incidence rose with increases in the amount of N supplied either as fertilizer applied during the growing season in irrigation water or as soil N, specifically nitrate, from fertilizer N application in previous years. A comparison of four different irrigation regimes demonstrated that black point incidence was highest under frequent irrigation (irrigate to field capacity at 75% available moisture) and lowest under conventional irrigation (irrigate to field capacity at 50% available soil moisture). In each irrigation regime, disease incidence increased as N rates were raised from 0 to 120 kg ha-1. A residual fertilizer-N study demonstrated in 1985 and 1986 that black point incidence generally rose with increasing levels of nitrogen from either preplant applications in the spring or soil nitrate from the previous year. However, additions of fertilizer N were shown to slightly reduce black point incidence at soil nitrate levels above 150 kg ha-1. A two-year fertilizer N study demonstrated that in treatments receiving the same amount (90 kg ha-1) of fertilizer N, the amount broadcast as a preplant treatment versus the amount applied in irrigation water in a fertigation treatment had no effect on black point incidence, but all fertilized treatments had significantly higher levels of disease than the unfertilized check.
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    URL: http://dx.doi.org/10.1007/BF00012805
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    Effects of variations in soil water potential, depth of N placement, and cultivar on postanthesis N uptake by wheat (1992)
    Springer
    Plant and soil 143 (1992), S. 45-53 
    Details
    ISSN: 1573-5036
    Keywords: 15N ; nitrogen harvest index ; nitrogen uptake efficiency ; soil water potential ; Triticum aestivum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract This study was conducted to investigate the influence of soil water potential, depth of N placement, timing, and cultivar on uptake of a small dose of labeled N applied after anthesis by wheat (Triticum aestivum L.) Understanding postanthesis N accumulation should allow better control of grain protein concentration through proper manipulation of inputs. Two hard, red spring-wheat cultivars were planted in early and late fall each yr of a 2-yr field experiment. Less than 1 kg N ha−1 as K 15NO3 was injected into the soil at two depths: shallow (0.05 to 0.08 m) and deep (0.15 to 0.18 m). In both years an irrigation was applied at anthesis, and injections of labeled N were timed 4, 12, and 20 days after anthesis (DAA). Soil water potential was estimated at the time of injection. Mean recovery of 15N in grain and straw was 57% of the 15N applied. Recovery did not differ between the high-protein (Yecora Rojo) and the low-protein (Anza or Yolo) cultivars. Mean recovery from deep placement was 60% versus only 54% from shallow placement (p 〈 0.01). Delaying the time of injection decreased mean recovery significantly from 58% at 4 DAA to 54% at 20 DAA. This decrease was most pronounced in the shallow placement, where soil drying was most severe. Regressions of recovery on soil water potential of individual cultivar x yr x planting x depth treatments were significant only under the driest conditions. Stepwise regression of 15N recovery on soil water potential and yield parameters using data from all treatments of both years resulted in an equation including soil water potential and N yield, with a multiple correlation coefficient of 0.64. The translocation of 15N to grain was higher (0.89) than the nitrogen harvest index (0.69), and showed a highly significant increase with increase in DAA. This experiment indicates that the N uptake capacity of wheat remains reasonably constant between 4 and 20 DAA unless soil drying is severe.
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    URL: http://dx.doi.org/10.1007/BF00009127
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    Barley response to nitrogen and non-nutritional benefits of legume green manure (1992)
    Springer
    Plant and soil 142 (1992), S. 19-30 
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    ISSN: 1573-5036
    Keywords: barley ; fertilizer ; green manure ; legume ; lentil ; nitrogen ; non-nutritional response
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Green manure application may benefit subsequent crops not only by improving nitrogen (N) fertility but also via non-nutritional mechanisms. The quantification of the latter effect, however, is complicated by the confounding effect of N fertility. Two experiments were conducted in controlled environments to partition the yield response of barley to green manure between N and non-nutritional effects. Each experiment included a factorial of fertilizer N application rates and green manure application rates. The fertilizer was labelled with 15N to facilitate discrimination between N sources. Approximately 24% of the N applied in green manure was assimilated by barley after 45 days (Experiment 1) and 32% was recovered by barley grown to maturity (Experiment 2). Apparent recovery of green manure-N by barley was not appreciably affected by fertilizer application. Regression analysis of the relationship between dry matter yield and plant N uptake demonstrated that yield responses to green manure application were not entirely attributable to improved N fertility. For a given amount of N assimilated by the crop, yields were higher in green manure-amended treatments than in those receiving no green manure. In barley grown to maturity, barley response to N and non-nutritional effects were estimated to be 5.3 and 2.2g pot−1, respectively. The relationship between dry matter yield and N uptake is suggested as a method for distinguishing nutritional and non-nutritional yield responses. This approach assumes that no other nutrient is limiting growth. The presence of non-nutritional benefits observed in this study demonstrates that the agronomic value of green manure is not limited to N release and casts doubt on the assumptions inherent to calculation of fertilizer equivalents.
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    URL: http://dx.doi.org/10.1007/BF00010171
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    Control of relative growth rate by application of the relative addition rate technique to a traditional solution culture system (1992)
    Springer
    Plant and soil 142 (1992), S. 113-122 
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    ISSN: 1573-5036
    Keywords: relative addition rate ; relative growth rate ; traditional solution culture ; Triticum aestivum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The relative addition rate (RAR) technique allows the nutritional control of plant relative growth rate (RGR) by the provision of nutrients at exponential supply rates. The technique, however, was developed with technologically sophisticated aeroponic systems. In this paper, we report on experiments used to adapt the RAR technique to a conventional solution culture system. A background concentration requirement of 36 μM nitrogen (N), with other nutrients supplied in proportion to N, was necessary to produce a constant RGR of Triticum aestivum L. (wheat) at a low RAR. Solution pH changes were reduced by increasing the percentage of NH4 in the nitrogen supply, but the plants exhibited dry weight reductions and symptoms of toxicity above 30% NH4. For wheat, a ratio of 25/75 NH4/NO3 was optimum for minimizing pH changes within the nontoxic range. A test of the effectiveness of the RAR technique using this background concentration and NH4/NO3 ratio showed that RGR increased with RAR with a linear slope of 0.55 and an intercept of 0.07 d-1. Although the relationship between growth rate and nutrient supply was less than the one-to-one dependence of RGR on RAR that has been obtained with more sophisticated apparatus, application of the RAR technique to a conventional solution culture system still affords considerable control of RGR and presents a simple method for growing plants at different levels of nutrient stress and at distinct RGRs.
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    Nitrogen mineralization and its controlling factors in various kinds of temperate humid-zone soils (1992)
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    Plant and soil 144 (1992), S. 31-44 
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    ISSN: 1573-5036
    Keywords: mineralization capacity ; nitrogen ; principal components analysis ; soil incubation ; temperate humid zone ; soils
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The N mineralization capacity of 41 temperate humid-zone soils of NW Spain was measured by aerobic incubation for 15 days at 28°C and 75% of field capacity. The main soil factors affecting organic N dynamics were identified by principal components analysis. Ammonification predominated over nitrification in almost all soils. The mean net N mineralization rate was 1.63% of the organic N content, and varied according to soil parent materials as follows: soils on basic and ultrabasic rocks 〈 soils over acid metamorphic rocks 〈 soils developed over sediments 〈 soils over acid igneous rocks 〈 soils on limestone. The N mineralization capacity was lower in natural soils than in cropped soils or pastures. The accumulation of organic matter (C and N) seems to be due to poor mineralization which was caused, in decreasing order of importance, by high exchangeable H-ion levels, high Al and Fe gel contents and, to a lesser extent (though more markedly in cropped soils), by silty clay texture and exchangeable Al ions.
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    Wheat growth responses of cultivars to H+ concentration (1992)
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    Plant and soil 146 (1992), S. 55-59 
    Details
    ISSN: 1573-5036
    Keywords: acid soils ; low pH ; Triticum aestivum ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Shoot length (cm), shoot fresh weight (g/pot), root length (cm), and root fresh weight (g/pot) were measured on six cultivars of wheat (Triticum aestivum L. cv Saluda, C9733, Gore, Stacy, FL301, and FL302) grown at pH 6.0, 5.5, 5.0, 4.5, or 4.0 for 14 days in ‘white quartz flintshot’ sand. Plants were watered on alternate days with pH-adjusted buffer solutions. All measured plant parameters decreased as H+ concentration increased from pH 6.0 to 4.0. Decreased lengths of shoots and roots were similar among the cultivars as the pH decreased. This indicated a uniform response of wheat cultivars to excess H+ concentration in the soil solution; however, the decrease in shoot and root length was only about 50% as large as was previously reported for sorghum [Sorghum bicolor (L.) Moench.].
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    Preliminary results from a microscopic examination on the effects of aluminium on the root tips of wheat (1992)
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    Plant and soil 146 (1992), S. 83-87 
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    ISSN: 1573-5036
    Keywords: aluminium ; electron microscope ; light microscope ; Triticum aestivum ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Root tips from aluminium (Al) tolerant (Waalt) and Al sensitive (Warigal) wheat (Triticum aestivum (L). Thell.) cultivars exposed to low concentrations of Al (10 μM) for 10, 24 and 72 hours were examined under the light and electron microscope. After fixing and embedding, longitudinal and transverse thin and ultrathin sections were cut. There was no evidence of Al damage to the root tips of the Al tolerant cultivar under both the light and electron microscope. For the Al sensitive cultivar, Al had no observable effect on the root tips 10 hours after Al addition when examined under the light microscope. When examined under an electron microscope, electron dense globular deposits were observed between the cell wall and cell membrane of the epidermal cells. There was not obvious damage to the cell cytoplasm. Two or 3 days after Al addition, light microscopy showed that the cells in the root tips had become swollen and extensively vacuolated. The tissues appeared disorganised and degenerate, particularly in the epidermis and outer cortical cells. The electron microscope also revealed a thickening of the cell wall. The cell wall was broken down, particularly in the epidermis in the region 4–6 mm from the root tip. The tissue in the meristematic area was largely intact.
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    Can maize cultivars with low mineral nutrient concentrations in the grains help to reduce the need for fertilizers in third world countries? (1992)
    Springer
    Plant and soil 146 (1992), S. 227-231 
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    ISSN: 1573-5036
    Keywords: cultivars ; grains ; maize ; nitrogen ; phosphorus ; potassium ; tropical climate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract An earlier study revealed considerable genotypic variation in grain N, P and K concentrations (GNC, GPC and GKC, respectively) in tropical maize. The expression of varietal differences in GNC, GPC and GKC, however, may depend on environmental conditions such as the N status of the soil. Two tropical maize hybrids (Suwan 2301 and CP 1) with comparable yielding capacity, but contrasting GNCs, GPCs and GKCs, were therefore grown at four levels of N in a field experiment at Farm Suwan (Thailand, latitude 14.5°N). Suwan 2301 exhibited a higher GNC than did CP 1 at all rates of N, but large differences in GPC and GKC were found only at high N fertilization. This was obviously due to individual grain yield responses of the cultivars to increasing rates of N fertilizer, demonstrating that grain nutrient concentrations are, at least in part, functions of the amount of grain carbohydrates which dilute a genetically and environmentally fixed amount of grain P and K. As compared to Suwan 2301, CP 1 accumulated less N, P and K in the grains at almost all levels of N fertilization, confirming our hypothesis that the cultivation of maize genotypes with low grain mineral nutrient concentrations may help third-world cash-crop farmers to reduce the need for scarce and costly mineral fertilizers. This finding has to be verified at reduced availability of soil −P, −K, and water.
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    Selecting zinc-efficient cereal genotypes for soils of low zinc status (1992)
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    Plant and soil 146 (1992), S. 241-250 
    Details
    ISSN: 1573-5036
    Keywords: Avena sativa ; genotypic differences ; grain zinc ; Hordeum vulgare ; Triticum aestivum ; zinc concentration ; zinc deficiency ; zinc uptake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Deficiencies of zinc are well known in all cereals and cereal-growing countries. From physiological evidence reported elsewhere, it would appear that a critical level for zinc is required in the soil before roots will either grow into it or function effectively; it is likely the requirement is frequently not met in deep sandy, infertile profiles widespread in southern Australia. Because fertilizing subsoils is impractical, this paper presents arguments for breeding cereal varieties with root systems better able to mobilise zinc from soil sources of low availability. Other agronomic arguments are presented in support of breeding for zinc efficiency. Significant genetic variation for this character is described for wheat, barley and oats. Linkage to other efficiency traits (e.g., manganese) is poor suggesting independent mechanisms and genetic control not linked to gross root system geometry. Zinc efficiency traits for sandy and clayey soils appear to be genetically different. Zinc-efficient genotypes absorb more zinc from deficient soils, produce more dry matter and more grain yield but do not necessarily have the highest zinc concentrations in tissue or grain. Although high grain zinc concentration also appears to be under genetic control, it is not tightly linked to agronomic zinc efficiency traits and may have to be selected for independently. High grain zinc is considered a desirable quality factor which not only contributes to the seedling vigour of the next generation but could increase the nutritional value of the grain in areas where a high dependence on grains for food may result in zinc deficiency in humans.
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    URL: http://dx.doi.org/10.1007/BF00012018
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    Abiotic factors regulating nitrogen transformations in the organic layer of acid forest soils: Moisture and pH (1992)
    Springer
    Plant and soil 147 (1992), S. 69-78 
    Details
    ISSN: 1573-5036
    Keywords: abiotic factors ; ectorganic layer ; forest ; mineralization ; moisture ; nitrification ; nitrogen ; pH ; regulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The relationships between nitrogen transformations and moisture and pH in coniferous forest litter were determined using laboratory incubation experiments. A linear relation between gravimetric moisture content and nitrification was found within the whole studied range of moisture conditions (10–290% ODW). Net nitrogen mineralization increased linearly with moisture content up to 140% ODW. At higher moisture contents, net mineralization was found to be independent of moisture. Relative nitrification was found to be a linear function of moisture content. The dependence of the CO2 production rates on moisture in the coniferous litter decreased from low to high moisture availability. Due to a nearly linear relationship between gravimetric moisture content and log-(water potential) within the investigated moisture range, the same type of relationships were found with this latter parameter as well. The relationship between nitrogen transformations and pH was studied by means of the addition of different amounts of HCl and NaOH during short incubation experiments (1 week). Nitrification was found to be a negative linear function of the H-ion concentration within the range of 0.04 (pH 4.40) and 0.36 (pH 3.45) mmol H-ion L−1. At a higher H-ion concentration and thus at a lower pH than 3.45, no nitrate was produced any more. No relationship between net mineralization and pH was found.
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    URL: http://dx.doi.org/10.1007/BF00009372
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    Root-induced nitrogen mineralisation: A nitrogen balance model (1992)
    Springer
    Plant and soil 139 (1992), S. 253-263 
    Details
    ISSN: 1573-5036
    Keywords: carbon ; exudation ; mineralisation ; nematode ; nitrogen ; protozoa ; rhizosphere ; root ; uptake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The possibility is examined that carbon (C) released into the soil from a root could enhance the availability of nitrogen (N) to plants by stimulating microbial activity. Two models are described, both of which assume that C released from roots is used by bacteria to mineralise and immobilise soil organic N and that immobilised N released when bacteria are grazed by bacterial-feeding nematodes or protozoa is taken up by the plant. The first model simulates the individual transformations of C and N and indicates that root-induced N mineralisation could supply only up to 10% of the plant's requirement, even if unrealistically ideal conditions are assumed. The other model is based on evidence that about 40% of immobilised N is subsequently taken up by the plant. A small net gain of N by the plant is shown (i.e. the plant takes up more N than it loses through exudation), although with exudate of up to C:N 33:1 less than 6% of the plant's requirement is supplied by root-induced N mineralisation. It is argued, however, that rhizosphere bacteria do not use plant-derived C to mineralise soil organic N to any great extent and that in reality root-induced N mineralisation is even less important than these models indicate.
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    URL: http://dx.doi.org/10.1007/BF00009317
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    Improving nitrogen-fixing systems and integrating them into sustainable rice farming (1992)
    Springer
    Plant and soil 141 (1992), S. 57-67 
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    ISSN: 1573-5036
    Keywords: aquatic legumes ; Azolla ; Cyanobacteria ; flooded rice soils ; nitrogen ; N2 fixation ; tropics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract This paper summarizes recent achievements in exploiting new biological nitrogen fixation (BNF) systems in rice fields, improving their management, and integrating them into rice farming systems. The inoculation of cyanobacteria has been long recommended, but its effect is erratic and unpredictable. Azolla has a long history of use as a green manure, but a number of biological constraints limited its use in tropical Asia. To overcome these constraints, the Azolla-Anabaena system as well as the growing methods were improved. Hybrids between A. microphylla and A. filiculoides (male) produced higher annual biomass than either parent. When Anabaena from high temperature-tolerant A. microphylla was transferred to Anabaena-free A. filiculoides, A. filiculoides became tolerant of high temperature. Azolla can have multiple purposes in addition to being a N source. An integrated Azolla-fish-rice system developed in Fujian, China, could increase farmers' income, reduce expenses, and increase ecological stability. A study using Azolla labeled with 15N showed the reduction of N losses by fish uptake of N. The Azolla mat could also reduce losses of urea N by lowering floodwater-pH and storing a part of applied N in Azolla. Agronomically useful aquatic legumes have been explored within Sesbania and Aeschynomene. S. rostrata can accumulate more than 100kg N ha-1 in 45 d. Its N2 fixation by stem nodules is more tolerant of mineral N than that by root nodules, but the flowering of S. rostrata is sensitive to photoperiod. Aquatic legumes can be used in rainfed rice fields as N scavengers and N2 fixers. The general principle of integrated uses of BNF in rice-farming systems is shown.
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    URL: http://dx.doi.org/10.1007/BF00011310
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    Effects of pre-storage conditions on storage of in vitro cultures of Nephrolepis exaltata (L.) Schott and Cordyline fruticosa (L.) A. Chev. (1992)
    Springer
    Plant cell, tissue and organ culture 28 (1992), S. 167-174 
    Details
    ISSN: 1573-5044
    Keywords: dark ; in vitro storage ; light ; stability ; temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In vitro cultures of Nephrolepis exaltata and Cordyline fruticosa were stored at 5°, 9° or 13°C, at a low irradiance (3–5 μmol m−2 s−1) or in darkness. Prior to storage the cultures were subjected to 18°, 21°, 24° or 27°C and 15, 30 or 45 μmol m−2 s−1 in a factorial combination. The optimal storage conditions for Nephrolepis were 9°C in complete darkness. These cultures were still transferable to a peat/perlite mixture at the end of the experimental period of 36 months. The optimal storage conditions for Cordyline were 13°C and a low light level (±3–5 μmol m-2 s-1). When the pre-storage conditions were normal growth room conditions (24°C and 30 μmol m-2 s-1), in vitro cultures could be stored for 18 months. With the most favourable pre-storage treatment (18°C and 15 μmol m-2 s-1) some cultures still had green shoots after 36 months of storage, but did not survive transfer to peat/perlite. Pre-conditioning before storage was most favourable for Nephrolepis, and not that important, but still favourable, for Cordyline. There was an interaction between pre-storage temperature and pre-storage irradiance. For both species a high irradiance level was less favourable than a low irradiance level when combined with high growth room temperatures.
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    URL: http://dx.doi.org/10.1007/BF00055513
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    Use of the gene pools of Triticum turgidum ssp. dicoccoides and Aegilops squarrosa for the breeding of common wheat (T. aestivum), through chromosome-doubled hybrids (1992)
    Springer
    Euphytica 59 (1992), S. 213-220 
    Details
    ISSN: 1573-5060
    Keywords: Triticum turgidum ssp. dicoccoides ; wild emmer wheat ; Aegilops squarrosa ; synthethic hexaploid wheat ; breeding common wheat ; Triticum aestivum ; meiosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Novel amphiploids or synthetic hexaploid wheats, derived from eleven accessions of Triticum turgidum ssp. dicoccoides (wild emmer wheat, AABB, 2n=28) and eight accessions of Aegilops squarrosa (goat grass, DD, 2n=14) were studied. Most amphiploids were normal, vigorous and fertile. Among amphiploids a wide variation for morphological characteristics was observed. The glumes were found very tenacious and the rachis tough, or nearly so. First metaphase of meiosis proved to be quite regular; however, some aneuploid offspring occurred in successive generations. In F1 hybrids between T. aestivum (common wheat, AABBDD, 2n=42) ‘Chinese Spring’ and the synthetic hexaploids the rate of chromosome association was lower than in both parents, and significant differences were observed between amphiploids. Multivalents occurred in very low frequencies in these F1 hybrids. The rate of chromosome association in a hybrid between two synthetic hexaploids was found to be very low. The results are discussed in terms of genetic interactions and structural differences between the genomes of the respective species.
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    URL: http://dx.doi.org/10.1007/BF00041274
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    Variation observed among bread wheat Wants found in durum fields on Rhodes in 1987 (1992)
    Springer
    Genetic resources and crop evolution 39 (1992), S. 3-7 
    Details
    ISSN: 1573-5109
    Keywords: Triticum aestivum ; bread wheat ; Triticum durum ; durum wheat ; variation ; Rhodos
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Bread wheat plants contaminating two adjacent durum wheat fields near Tholos, Rhodos, could be classed in two groups. The origin of these two groups is unknown.
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    URL: http://dx.doi.org/10.1007/BF00052649
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    Effects of phytoplankton on the elemental composition (C, N, P) of suspended particulate material in the lower river Rhine (1992)
    Springer
    Hydrobiologia 235-236 (1992), S. 479-489 
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    ISSN: 1573-5117
    Keywords: River Rhine ; phytoplankton ; suspended material ; carbon ; nitrogen ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The spatial and temporal distribution of element concentrations were monitored together with chlorophyll a as an indicator of algal density to assess the effect of phytoplankton on the elemental composition (C, N, P) of suspended materials in the lower Rhine. The high concentrations of particulate C, N and P in the river were found to decrease in the delta and to increase again in the estuarine turbidity zone. Phytoplankton blooms increased the concentrations of particulate C, N, and P significantly in the upstream part of the river. In summer 1989, 15–65% of the particulate C and 20–75% of the particulate N were attributable to phytoplankton. Together with published data these observations indicate that in eutrophic rivers, the input of organic materials from the catchment is strongly modified and supplemented by in situ growth of phytoplankton. During seaward transport the phytoplankton and the particulate elements disappeared from the river water concomitantly with the suspended matter, indicating an increased retention of these elements due to sedimentation. In contrast, soluble ammonia, nitrite and phosphate increased in the tidal reaches of the river because of local input in the harbour and city of Rotterdam and because of mineralization. Therefore the total nutrient load of the Rhine estimated at the German/Dutch border does not reflect the actual input into the sea.
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    URL: http://dx.doi.org/10.1007/BF00026236
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    Nutrient loading and drainage channel response in a ricefield system (1992)
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    Hydrobiologia 230 (1992), S. 193-200 
    Details
    ISSN: 1573-5117
    Keywords: nitrogen ; phosphorus ; ricefield system ; drainage channels ; mediterranean Deltas
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nitrogen and phosphorus released into the water of a main drainage channel in the Ebro Delta was measured during a period of rice cultivation. An increase in total nitrogen and phosphorus in its different forms in accordance with the increase in cultivated area drained was observed. A significant correlation between the release of nutrients into the water and the nutrient load, for both nitrogen and phosphorus, if we consider the release of nutrients per unit of length of the channel and increased total phosphorus content of the water that flows through it during the period of rice cultivation. Physical and chemical changes in the water as a result of ricefield metabolism may explain the differences observed in nitrogen and phosphorus cycles between Ebro and Rhône Deltas, two mediterranean deltaic systems where a large area with similar drainage system is used for rice cultivation.
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    URL: http://dx.doi.org/10.1007/BF00036565
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    Regeneration of inorganic phosphorus and nitrogen from decomposition of seston in a freshwater sediment (1992)
    Springer
    Hydrobiologia 228 (1992), S. 71-81 
    Details
    ISSN: 1573-5117
    Keywords: nutrient regeneration ; phosphorus ; nitrogen ; sediment ; lakes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The mineralization of phosphorus and nitrogen from seston was studied in consolidated sediment from the shallow Lake Arreskov (July and November) and in suspensions without sediment (July). In the suspension experiment, phosphorus and nitrogen were mineralized in the same proportions as they occurred in the seston. During the 30 days suspension experiment, 47 and 43% of the particulate phosphorus and nitrogen, respectively, was mineralized with constant rates. Addition of seston to the sediment had an immediate enhancing effect on oxygen uptake, phosphate and ammonia release, whereas nitrate release decreased due to denitrification. The enhanced rates lasted for 2–5 weeks, while the decrease in nitrate release persisted throughout the experiment. The increase in oxygen uptake (equivalent to 21% of the seston carbon) was, however, only observed in the July experiment. The release of phosphorus and nitrogen from seston decomposing on the sediment surface differed from the suspension experiments. Thus, between 91 and 111% of the phosphorus in the seston was released during the experiments. Due to opposite directed effects on ammonium and nitrate release, the resulting net release of nitrogen was relatively low. A comparison of C/N/P ratios in seston, sediment and flux rates indicated that nitrogen was mineralized faster than phosphorus and carbon. Some of this nitrogen was lost through denitrification and therefore not measurable in the flux of inorganic nitrogen ions. This investigation also suggests that decomposition of newly settled organic matter in sediments have indirect effects on sediment-water exchanges (e.g. by changing of redox potentials and stimulation of denitrification) that modifies the release of mineralized phosphate and nitrogen from the sediment.
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    URL: http://dx.doi.org/10.1007/BF00006478
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    The influence of flushing on nutrient dynamics, composition and densities of algae and transparency in Veluwemeer, The Netherlands (1992)
    Springer
    Hydrobiologia 233 (1992), S. 187-196 
    Details
    ISSN: 1573-5117
    Keywords: eutrophication ; lake restoration ; flushing ; Veluwemeer ; algal species ; transparency ; phosphorus ; nitrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Total phosphorus and chlorophyll decreased significantly after reduction of the external phosphorus loading and the start of flushing Veluwemeer with polder water in 1979. Flushing of Veluwemeer has had a large impact on nutrient dynamics. Especially in the first winter, dilution was the main cause of changes in water quality. On a longer term the increase of the inactivation of phosphorus in sediments is important. Oscillatoria agardhii has been brought to the margins of its habitat. Three successive cold winters were an additional causal factor in the disappearance of Oscillatoria agardhii and the dominance of diatoms and green algae from 1985 onwards. Due to higher detritus and inorganic suspended matter concentrations transparency increased less than expected. Since 1985 chlorophyll only contributes for a small percentage to the transparency. In the present situation further improvement of the water quality of Veluwemeer is questionable, as the phosphorus concentration in the lake and the polder water is almost the same. Therefore it is recommanded to shift flushing operations, at least in the winter period, from Veluwemeer towards Wolderwijd.
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    The daily pattern of nitrogen uptake by phytoplankton in dynamic mixed layer environments (1992)
    Springer
    Hydrobiologia 238 (1992), S. 37-52 
    Details
    ISSN: 1573-5117
    Keywords: ammonium ; cyanobacteria ; diel ; diurnal ; mixing ; nitrate ; nitrogen ; periodicity ; phytoplankton ; protein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The transport and assimilation of the various forms of biologically available nitrogen by phytoplankton, and the subsequent biosynthesis of N-containing macromolecules, have the potential to respond in different ways during the daily growth cycle. This review examines five types of effect that may influence the daily pattern of nitrogen uptake and metabolism: light versus dark (the day/night cycle); changes in irradiance during the day (including the diurnal rise and fall in photon fluence rates); circadian rhythms (endogenous patterns of variation which may continue in the absence of external environmental forcing); periodic variations in exogenous nitrogen supply; and the 24-hour dynamics of stratification and mixing. The hydrodynamic effects operate through a variety of direct and indirect controls, and can substantially modify the diel rhythmicity of phytoplankton growth.
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    Phytoplankton and zooplankton community structure after nutrient additions to the oligotrophic Lake Hecklan, Sweden (1992)
    Springer
    Hydrobiologia 243-244 (1992), S. 147-155 
    Details
    ISSN: 1573-5117
    Keywords: fertilization ; phosphorus ; nitrogen ; phytoplankton ; zooplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Lake Hecklan, in central Sweden, was fertilized with phosphorus and nitrogen during thermal stratification (late May-early Oct) 1984–1987. The nutrient additions were relatively small and raised the total phosphorus concentrations from 6 to 10 µg l−1. The working hypothesis was that this moderate increase in the phosphorus concentration could increase the phytoplankton biomass without adverse changes in the planktonic community structure. The fertilization increased the phytoplankton biomass from 0.1 to a maximum of 2 mm3 l−1. Chrysophyceae and Cryptophyceae dominated throughout the experimental period. Thus, the phytoplankton composition remained typical for a Swedish forest lake and provided a potential for increased zooplankton growth. An increased growth of zooplankton was indicated by increased biomass of Cladocera and Copepoda in 1984 and 1985, and by increased fecundity of herbivorous zooplankton.
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    Predictability of streamflow and particulate organic matter concentration as indicators of stability in prairie streams (1992)
    Springer
    Hydrobiologia 242 (1992), S. 7-18 
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    ISSN: 1573-5117
    Keywords: POM ; prairie streams ; predictability ; stability ; stream flow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Predictability of stream discharge and particulate organic matter (POM) in the water column was estimated, using Colwell's indices of constancy and contingency, for 6 Texas prairie streams (1 each of 2nd, 3rd, and 4th order with intermittent or perennial discharge). Stream discharge in these 6 prairie streams varied between 0 and 36000 1 s−1, depending on the stream and season. Predictability (P) of discharge in these streams ranged from 0.45 to 0.62, within the range of values expected for North American streams. Predictability of stream discharge was not significantly different between streams. Particulate organic matter concentrations in these prairie streams are relatively low, ranging from 0.25 to 4.00 mg AFDM 1−1. Predictability of POM concentration in these streams was high, ranging from 0.75 to 0.85, and was largely the result of constancy of POM concentrations. Within the different POM size classes, Fine POM (FPOM) had the highest predictability (P = 0.89−0.96). In spite of relatively unpredictable stream discharge, POM remained fairly constant providing a measure of habitat predictability and stability.
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    Exchange of N2O and CH4 between the atmosphere and soils in spruce-fir forests in the northeastern United States (1992)
    Springer
    Biogeochemistry 18 (1992), S. 119-135 
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    ISSN: 1573-515X
    Keywords: N2O ; CH4 ; red spruce ; balsam fir ; spruce-fir ; forests ; nitrogen ; deposition ; nitrification ; mineralization ; denitrification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract We measured the exchange of N2O and CH4 between the atmosphere and soils in 5 spruce-fir stands located along a transect from New York to Maine. Nitrous oxide emissions averaged over the 1990 growing season (May–September) ranged from 2.1 ug N2O-N/m2-hr in New York to 0.4 ug N2O-N/m2-hr in Maine. The westernmost sites, Whiteface Mtn., New York and Mt. Mansfield, Vermont, had the highest nitrogen-deposition, net nitrification and N2O emissions. Soils at all sites were net sinks for atmospheric CH4 Methane uptake averaged over the 1990 growing season ranged from 0.02 mg CH4-C/M2-hr in Maine to 0.05 mg CH4-C/m2-hr in Vermont. Regional differences in CH4 uptake could not be explained by differences in nitrogen-deposition, soil nitrogen dynamics, soil moisture or soil temperature. We estimate that soils in spruce-fir forests at our study sites released ca. 0.02 to 0.08 kg N2O-N/ha and consumed ca. 0.74 to 1.85 kg CH4 C/ha in the 1990 growing season.
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    Nitrogen immobilization in leaf litter at two Mediterranean ecosystems of SW Spain (1992)
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    Biogeochemistry 15 (1992), S. 213-228 
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    ISSN: 1573-515X
    Keywords: immobilization ; leaf litter decomposition ; lignin ; Mediterranean ecosystem ; nitrogen ; tannin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Nitrogen immobilization in relation to the dynamics of lignin and tannins in nine different types of leaf litter was investigated during a 2-yr study at two Mediterranean ecosystems of SW Spain. Net nitrogen immobilization for all the species was higher in a forest than in the more nutrient-poor soil of a shrubland. Absolute amount of lignin increased in both ecosystems in the first 2–4 months whereas tannin rapidly decreased in the same time period. Increases in lignin were significantly correlated to losses of tannins during decomposition. Initial tannin content was the best predictor of the maximum amount of immobilized nitrogen in litter in both ecosystems. Mechanisms that could explain the immobilization of nitrogen in litter are discussed.
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    Effects of nitrogen: phosphorus supply ratios on nitrogen fixation in agricultural and pastoral ecosystems (1992)
    Springer
    Biogeochemistry 18 (1992), S. 19-35 
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    ISSN: 1573-515X
    Keywords: Dinitrogen fixation ; nitrogen ; phosphorus ; competition ; legumes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract An analysis of data compiled from the literature confirms a strong inverse relationship between annual rates of nitrogen fixation and the soil nitrogen content in agricultural and pastoral ecosystems. However, this inverse relationship is strongly modified by the rate of application of phosphorus fertilizer, which strongly influences the activities of both symbiotic and non-symbiotic nitrogen fixing organisms. In the case of symbiotic legumes, the response of N-fixation to N and P is in part a result of changes in legume dominance within the plant community. These results, as well as supporting data presented from a review of experiments on nitrogen fixation in a variety of other terrestrial and aquatic ecosystems, provide important support for the hypothesis that phosphorus availability is a key regulator of nitrogen biogeochemistry.
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    URL: http://dx.doi.org/10.1007/BF00000424
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    Carbon and nitrogen limitations of soil microbial biomass in desert ecosystems (1992)
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    Biogeochemistry 18 (1992), S. 1-17 
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    ISSN: 1573-515X
    Keywords: microbial biomass-N ; desert ; carbon ; nitrogen ; shrubland ; grassland ; playa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Microbial biomass nitrogen was measured in unamended (dry) and wetted soils in ten shrubland and grassland communities of the Chihuahuan desert, southern New Mexico, by the fumigation-extraction method. Microbial biomass-N in dry soils was undetectable. Average microbial biomass-N in wetted soils among all plant communities was 15.3 μg g-1 soil. Highest values were found in the communities with the lowest topographic positions, and the minimum values were detected in the spaces between shrubs. Microbial biomass was positively and significantly correlated to soil organic carbon and extractable nitrogen (NH4 + + NO3 -). In a stepwise multiple regression, organic carbon and extractable nitrogen accounted for 40.9 and 5.6%, respectively, of the variance in microbial biomass-N among all the samples. Among communities, the soil microbial biomass was affected by the ratio of carbon to extractable nitrogen. Our results suggest a succession in the control of microbial biomass from nitrogen to carbon when the ratio of carbon to nitrogen decreases during desertification.
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    Soil nutrient dynamics in response to irrigation of a Panamanian tropical moist forest (1992)
    Springer
    Biogeochemistry 19 (1992), S. 1-25 
    Details
    ISSN: 1573-515X
    Keywords: nitrogen ; phosphorus ; soil fertility ; tropical forest
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract We measured concentrations of soil nutrients (0–15 and 30–35 cm depths) before and after the dry season in control and dry-season irrigated plots of mature tropical moist forest on Barro Colorado Island (BCI) in central Panama to determine how soil moisture affects availability of plant nutrients. Dry-season irrigation (January through April in 1986, 1987, and 1988) enhanced gravimetric soil water contents to wet-season levels (ca. 400 g kg−1 but did not cause leaching beyond 0.8 m depth in the soil. Irrigation increased concentrations of exchangeable base cations (Ca2+, Mg2+, K+, Na+), but it had little effect on concentrations of inorganic N (NH4 +C, NO3 − and S (SO4 2−). These BCI soils had particularly low concentrations of extractable P especially at the end of the dry season in April, and concentrations increased in response to irrigation and the onset of the rainy season. We also measured the response of soil processes (nitrification and S mineralization) to irrigation and found that they responded positively to increased soil moisture in laboratory incubations, but irrigation had little effect on rates in the field. Other processes (plant uptake, soil organic matter dynamics) must compensate in the field and keep soil nutrient concentrations at relatively low levels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00000572
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  • 96
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    Contribution of inoculation with azolla combined with nitrogen, phosphorus and zinc to rice in Nile Delta (1992)
    Springer
    World journal of microbiology and biotechnology 8 (1992), S. 579-584 
    Details
    ISSN: 1573-0972
    Keywords: Azolla ; fertilization ; nitrogen ; phosphate ; rice ; zinc
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Rice performance, in terms of plant height, productive tillering, yield and N-contents of grain and straw, harvest index (grain yield as a percentage of grain plus straw yields) and relative fertilizer N-use efficiency (kg grain yield/kg fertilizer-N) was enhanced by urea, ZnSO4 and green manuring withAzolla caroliniana. Unlike urea fertilizer, calcium superphosphate increased the rate of azolla field colonization and promoted a thick, healthy dark-green mat of the fern. Response to ZnSO4 was higher in the azolla-free sub-subplots. Application of ZnSO4 corrected symptoms of Zn deficiency in rice but the addition of calcium superphosphate in the absence of Zn intensified the symptoms of Zn deficiency.
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    URL: http://dx.doi.org/10.1007/BF01238792
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  • 97
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    Chemical variation within and between individuals ofPlantago lanceolata (Plantaginaceae) (1992)
    Springer
    Journal of chemical ecology 18 (1992), S. 985-995 
    Details
    ISSN: 1573-1561
    Keywords: Plantago lanceolata ; iridoid glycosides ; aucubin ; catalpol ; nitrogen ; plant size ; plant-insect interactions ; chemical variation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Variation in concentrations of leaf nitrogen and iridoid glycosides was examined in replicate plants of five genotypes ofPlantago lanceolata (Plantaginaceae) grown in an experimental garden. Nitrogen concentration and iridoid glycoside concentration were affected by leaf age. New leaves had nitrogen concentrations 1.7 to 2.7 times higher than mature leaves. Catalpol concentration was highest in new and intermediate-aged leaves. The concentration of aucubin, the biosynthetic precursor to catalpol, was higher in intermediate-aged leaves than in mature leaves, in three of five genotypes. Consequently, the proportion of aucubin relative to total iridoid glycosides increased as leaves aged. Concentration of iridoid glycosides was not correlated with plant size. Plant genotype significantly affected concentration of nitrogen and iridoid glycosides, as well as plant size. Thus, major indicators of hostplant quality for insect herbivores varied considerably both within and among plant genotypes and individuals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00980057
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  • 98
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    Effect of nitrogen and water uptake on yield of wheat (1992)
    Springer
    Nutrient cycling in agroecosystems 31 (1992), S. 5-8 
    Details
    ISSN: 1573-0867
    Keywords: Water use- efficiency ; nitrogen ; nitrogen fertilization ; Triticum aestivum L. ; water-nitrogen interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract For 2 years, field experiments were conducted to study the direct and interactive effects of water and nitrogen uptake at different growth stages on grain yield of wheat, grown on coarse textured alluvial soil of Ludhiana. Twelve treatments comprising 3 irrigation regimes and 4 rates of N were imposed. The N and irrigation regimes showed significant interaction, especially during the drier year. Grain yield was better explained with water uptake and N uptake, when partitioned over different growth stages than with total uptake. The sensitivity factor for water uptake was higher at the reproductive stage (λ = 1.60) than at the vegetative (λ = 1.05) and maturation (λ = 0.38) stages. Contrary, yield was more sensitive to N uptake during the vegetative stage than the reproductive and the maturation stages. Sensitivity of grain yield to water uptake was higher at higher N application rates. Yield predictability was much better (R2 = 0.98) when N and water uptake at different growth stages were combined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01064221
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  • 99
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    Electronic Resource
    The influence of tillage and cropping-intensity on cereal response to nitrogen, sulfur, and phosphorus (1992)
    Springer
    Nutrient cycling in agroecosystems 31 (1992), S. 15-19 
    Details
    ISSN: 1573-0867
    Keywords: Tillage ; crop rotation ; cereal grain ; wheat ; nitrogen ; sulfur ; phosphorus ; no-till
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Efficient fertilizer use is a prerequisite for achieving optimum crop yield while avoiding environmental contamination. Cereal response to nitrogen (N), sulfur (S), and phosphorus (P) were determined for 6 years under differing tillage [conventional-till (CT) vs. no-till (NT)] and intensity of cropping (cereal/fallow vs. cereal/cereal). Semidwarf white winter wheat (Triticum aestivum L.) alternated yearly with either fallow or spring cereal [barley (Hordeum vulgare L.) or spring wheat] on a Typic Haploxeroll soil in a 415 mm rainfall zone. Fertilizer treatments were no fertilizer (None), N only (N), N plus S (NS), and N plus S plus P (NSP). Average application rate, when applied, was 109 kg N, 18 kg S, and 11 kg P ha−1. Average cereal yield without fertilizer was 1.82 t ha−1. Nitrogen increased grain yield in 6 of 6, S in 4 of 6, and P in 3 of 6 years, with P and S response significant the remaining years at the 10% probability level. Average yield increases were 1.11 t ha−1 for N, 0.93 t ha−1 for S, and 0.47 t ha−1 for P. The NT/CT yield ratio was 0.60, 0.75, 0.93, and 0.95 with None, N, NS, and NSP addition, respectively, indicating that N and S deficiency were more severe in no-till. Limited increase in the NT/CT ratio with P addition indicated that P deficiency was less affected by tillage. Winter wheat always yielded less under NT than CT regardless of fertility, whereas spring cereals reached equality when fertilized with NSP. Annually-cropped wheat yielded 52, 67, 89, and 90% of wheat after fallow with None, N, NS, and NSP, respectively. Thus N and S, but not P, deficiency was more intense with increased frequency of cropping. Adequate fertility was a prime prerequisite for efficient yield in all systems.
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    URL: http://dx.doi.org/10.1007/BF01064223
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  • 100
    Electronic Resource
    Electronic Resource
    The role of manganese and nitrogen nutrition in the susceptibility of wheat plants to take-all in Western Australia (1992)
    Springer
    Nutrient cycling in agroecosystems 31 (1992), S. 35-41 
    Details
    ISSN: 1573-0867
    Keywords: Manganese ; nitrogen ; wheat ; Triticum aestivum L. ; take-all (Gaeumannomyces graminis)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Five field experiments are described which measured the effect of take-all on grain yield of wheat when 5 levels of manganese fertilizer were applied in a factorial combination with 5 different types of nitrogen fertilizer. Ammonium nitrogen fertilizer, either as ammonium sulphate or ammonium chloride, lowered the severity of take-all. By contrast, sodium nitrate had no effect on the incidence and severity of take-all. Ammonium chloride and ammonium sulphate were equally effective at controlling take-all, suggesting that the chloride or sulphate ion had little or no effect on the disease. Manganese sulphate decreased take-all severity at two trial sites. Where manganese was deficient, an application of manganese lowered the severity of take-all, had no effect on the incidence and increased the dry matter and grain yields of the wheat plants. There were no beneficial effects of applied manganese if the wheat plants were adequately supplied with soil manganese. The results suggest that take-all is more severe where plants are deficient in either manganese or nitrogen. The work also suggests that manganese deficiency is not necessarily the reason why the wheat plants grown on the acid soils of south-west Western Australia are prone to take-all.
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    URL: http://dx.doi.org/10.1007/BF01064225
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