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  • Triticum aestivum  (853)
  • nitrogen  (794)
  • kinetics  (727)
  • Springer  (2,371)
  • Periodicals Archive Online (PAO)
  • 101
    Electronic Resource
    Electronic Resource
    The Kinetics of Transposable Element Autoregulation (2000)
    Springer
    Genetica 108 (2000), S. 229-237 
    Details
    ISSN: 1573-6857
    Keywords: autoregulation ; dimerization ; kinetics ; post-transcriptional regulation ; transposable elements (TEs)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Kinetic modeling of the self-regulatory mechanisms of transposable elements (TEs) involving interactions of one or a few gene products makes predictions that are often at odds with observed results. In particular, explanations of TE autorepression at high copy number that invoke a decrease in number of active monomers through dimerization, amyloidization, and protein-mRNA binding to create an inactive state are not supported by analysis of the corresponding kinetic models. This is also true for similar mRNA–mRNA binding models. Self-repression in marineras well as other TEs can, however, be explained by a host-independent model in which inactive dimers compete with monomers for TE binding sites at the ends of the element. This model would also allow heterodimer poisoning to down-regulate transposition in the presence of divergent nonautonomous elements, since nondivergent monomers would be required at both TE ends for transposition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004172703790
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  • 102
    Electronic Resource
    Electronic Resource
    Control of the Mitochondrial Permeability Transition Pore by High-Affinity ADP Binding at the ADP/ATP Translocase in Permeabilized Mitochondria (2000)
    Springer
    Journal of bioenergetics and biomembranes 32 (2000), S. 91-96 
    Details
    ISSN: 1573-6881
    Keywords: Permeability transition ; ADP/ATP translocase ; kinetics ; adenosine diphosphate ; carboxya tractyloside ; bongkekic acid ; mitochondria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Low levels of ADP binding at the ADP/ATP translocase caused inhibition of the Ca2+-inducedpermeability transition of the mitochondrial inner membrane, when measured using the shrinkage assay on mitochondria, which have already undergone a transition. Inhibition was preventedby carboxyatractyloside, but potentiated by bongkrekic acid, which increased the affinity forinhibition by ADP. This suggests that inhibition was related to the conformation of thetranslocase. Ca2+ addition was calculated to remove most of the free ADP. Ca2+ added after ADPinduced a slow decay of the inhibition, which probably reflected the dissociation of ADP fromthe translocator. We conclude that the probability of forming a permeability transition pore(PTP) is much greater when the translocase is in the CAT conformation than in the BKAconformation, and, in the absence of CAT and BKA, the translocator is shifted between theBKA and CAT conformations by ADP binding and removal, even in deenergized mitochondria with no nucleotide gradients.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005568630151
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  • 103
    Electronic Resource
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    Distribution and Exudation of Allelochemicals in Wheat Triticum aestivum (2000)
    Springer
    Journal of chemical ecology 26 (2000), S. 2141-2154 
    Details
    ISSN: 1573-1561
    Keywords: Allelopathy ; phenolic acids ; 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one ; DIMBOA ; GC-MS-MS ; wheat ; Triticum aestivum ; weed suppression ; annual ryegrass ; Lolium rigidum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Wheat allelopathy has potential for weed suppression. Allelochemicals were identified in wheat seedlings, and they were exuded from seedlings into agar growth medium. p-Hydroxybenzoic, trans-p-coumaric, cis-p-coumaric, syringic, vanillic, trans-ferulic, and cis-ferulic acids and 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA) were identified in both the shoots and roots of 17-day-old wheat seedlings and their associated agar growth medium. Wheat accessions with previously identified allelopathic activity tended to contain higher levels of allelochemicals than poorly allelopathic ones. The allelopathic compounds present in the shoots generally also were identified in the roots and in the agar medium. Allelochemicals were distributed differentially in wheat, with roots normally containing higher levels of allelochemicals than the shoots. When the eight allelochemicals were grouped into benzoic acid and cinnamic acid derivatives, DIMBOA, total coumaric, and total ferulic acids, the amount of each group of allelochemicals was correlated between the roots and the shoots. Most of the allelochemicals identified in the shoots and roots could be exuded by the living roots of wheat seedling into the agar growth medium. However, the amounts of allelochemicals in the agar growth medium were not proportional to those in the roots. Results suggest that wheat plants may retain allelochemicals once synthesized. The presence of allelochemicals in the agar growth medium demonstrated that wheat seedlings were able to synthesize and to exude phytotoxic compounds through their root system that could inhibit the root growth of annual ryegrass.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005520500110
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  • 104
    Electronic Resource
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    Jasmonate-Induced Responses of Nicotiana sylvestris Results in Fitness Costs Due to Impaired Competitive Ability for Nitrogen (2000)
    Springer
    Journal of chemical ecology 26 (2000), S. 915-952 
    Details
    ISSN: 1573-1561
    Keywords: Nicotiana sylvestris ; nitrogen ; nicotine ; allocation ; growth ; reproduction ; induced defenses ; costs of defense
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract We present the first evidence for a fitness cost of an inducible response that is detectable in a nitrogen (N) currency. Nicotine is an induced defense in Nicotiana sylvestris that can utilize 5–8% of the plant's total N, an investment that apparently cannot be recouped by metabolism. Induced nicotine production is endogenously regulated by jasmonic acid (JA), and we treated leaves with the methyl ester of this wound hormone (MeJA) in quantities (0, 25, 250 μg) known to elicit changes in endogenous JA and subsequent nicotine responses comparable to those elicited by mechanical wounding and herbivory in this species. We grew plants in competition chambers (CCs) in which three same-sized plants could compete for a communal but fixed pool of 15NO3 to quantify the outcome of competition for this fitness-limiting resource that is used both in defense and seed production. Competition profoundly increased all measures of growth and reproductive performance measured per milligram of N acquired. While plants acquired all the N supplied to them in the hydroponic solution, plants grown in CCs (as compared those grown in individual chambers—ICs) retained more of this N and produced more biomass, had larger nicotine contents, allocated less of their N to nicotine, produced larger floral stalks with more flowers, aborted fewer flowers, matured more capsules, and produced a greater mass of seed. Plants grown in ICs produced heavier seed, but this difference did not translate into a difference in seed viability. MeJA treatment increased nicotine concentrations in proportion to the amount applied and significantly reduced growth (13–23%) and reproductive (31–44%) performance for plants grown with uninduced competitors, reflecting a large opportunity cost of induction. The effects of MeJA treatment on growth and reproduction were significantly less pronounced for plants grown in ICs. MeJA treatment significantly reduced the ability of plants to compete for [15N]KNO3 (reducing uptake by 9.5% and 23.7% for 25- and 250-μg MeJA-treated plants, respectively); no reductions in N acquisition were found in IC grown plants treated with MeJA. This impairment of competitive ability could account for 41–47% of the jasmonate-induced reductions in biomass by the day 15 harvest and 12–20% of the reductions in seed set and, in addition, created by "opportunity benefit" for neighboring uninduced plants, which grew larger, aborted fewer flowers, and matured more seed (a 28% increase) than did uninduced plants competing with similarly uninduced plants. Competition dramatically increased plant growth and reproductive performance, and MeJA treatment of these high-performing plants significantly reduced their competitive ability, which translated into opportunity costs for induced plants and opportunity benefits for neighboring uninduced plants. Induced plants minimized these fitness costs by reducing their use of recently acquired N for nicotine biosynthesis when growing with competitors. MeJA treatments also altered stalk length, flower production, flower abortion, and allocation to seed mass. In spite of all this plasticity, induced responses incur large fitness costs, costs that could be in part attributed to reductions in competitive ability for N. We conclude that inducibility functions to minimize these costs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005408208826
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  • 105
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    The Relationship Between Rate of Administration of an Intubating Dose of Rocuronium and Time to 50% and 90% Block at the Adductor Pollicis Muscle (2000)
    Springer
    Journal of clinical monitoring and computing 16 (2000), S. 219-222 
    Details
    ISSN: 1573-2614
    Keywords: Neuromuscular relaxants ; rocuronium ; kinetics ; distribution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Medicine
    Notes: Abstract Objective.To determine the relationship between the rate ofrocuronium injection and the onset time of neuromuscular block. Methods.After intravenous induction, 60 female patients (ASA I–II) wereassigned randomly into 3 groups for rocuronium administration within1–15, 15–30 or 30–60 seconds. Acceleromyography of the thumbwas performed using train-of-four (TOF) stimulation. Times to 50% and 90%twitch depression of the first twitch of the TOF stimulation (T1) wererecorded. Results.Injection time significantly influences time to 50%relaxation, but not time to 90% relaxation. Body mass index is negativelycorrelated with time to 50% and 90% relaxation. Conclusions.Weconclude that rate of injection influences only the initial phase ofdevelopment of the block and that slower injection times do not significantlyaffect time to 90% relaxation at the adductor pollicis muscle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009964305762
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  • 106
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    Non-Steady State Monitoring by Respiratory Gas Exchange (2000)
    Springer
    Journal of clinical monitoring and computing 16 (2000), S. 351-360 
    Details
    ISSN: 1573-2614
    Keywords: carbon dioxide ; oxygen ; kinetics ; non-steady state ; cardiac output ; PEEP ; pulmonary embolism ; pulmonary gas exchange monitoring
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Medicine
    Notes: Abstract Traditionally, the study of CO2 and O2 kinetics in the body has been mostly confined to equilibrium conditions. However, the peri-anesthesia period and the critical care arena often involve conditions of non-steady state. The detection and explanation of CO2 kinetics during non-steady state pathophysiology have required the development of new methodologies, including the CO2 expirogram, average alveolar expired PCO2, and CO2 volume exhaled per breath. Several clinically relevant examples of non-steady state CO2 kinetics perturbations are examined, including abrupt decrease in cardiac output, application of positive end-expiratory pressure during mechanical ventilation, and occurrence of pulmonary embolism. The lesser known area of non-steady state O2 kinetics is introduced, including the measurement of pulmonary O2 uptake per breath. Future directions include the study of the respiratory quotient per breath, where the anaerobic threshold during anesthesia is identified by increasing respiratory quotient.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011447500984
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  • 107
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    Effects of excreta return on properties of a grazed pasture soil (2000)
    Springer
    Nutrient cycling in agroecosystems 56 (2000), S. 79-85 
    Details
    ISSN: 1573-0867
    Keywords: exchangeable cations ; nitrogen ; soil carbon ; soil quality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The long term impact of excreta return on some chemical and biological properties of a pasture soil fertilised with sulphur and phosphate was studied in a system that had been with or without excreta for 23 years. Excreta free areas that had developed under electric fencelines, and parallel transects in the paddocks, were sampled to provide this comparison. Sampling was to 300 mm depth in 0–75, 75–150 and 150–300 mm sections. Total carbon and nitrogen were 20% higher in the 0–150 mm soil layer of areas receiving excreta but did not differ in the 150–300 mm layer. Carbon:nitrogen ratios were similar in both systems as was mineralisable nitrogen, both absolutely and as a percentage of total in the 0–75 mm layer. Significantly more N was mineralised in the 75–150 mm layers of the areas receiving excreta but this was reversed in the 150–300 mm layer. Nitrification rate was higher in all layers of the excreta areas. Inorganic and organic P fractions did not differ significantly. Total P was significantly higher in the 0–75 mm layer and significantly lower in the 150–300 mm layer of the excreta areas. Exchangeable potassium was much higher throughout the excreta areas while this was offset by calcium. The sum of the cations was similar in both areas. Excreta affected most of the diagnostic soil tests used for fertiliser recommendations. The soil properties measured did not reflect clearly the differences in productivity that were obvious in the two areas. It is concluded that excreta return has a impact resulting in increased organic matter storage. Short-term effects of urine have a greater impact on productivity. The major effect is on the disposition of cations and available P.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009842727493
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  • 108
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    Transformations and plant uptake of urine N and S in long and short-term pastures (2000)
    Springer
    Nutrient cycling in agroecosystems 56 (2000), S. 109-116 
    Details
    ISSN: 1573-0867
    Keywords: labelled nitrogen ; Lolium perenne ; nitrogen cycling ; root biomass ; straw ; Triticum aestivum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A field trial was carried out to compare the transformations and plant uptake of urine N and S in a short-term pasture from within an arable/pasture ley rotation and a long-term pasture. Animal urine labelled with 15N and 35S was applied to microplots at both sites. These microplots were destructively sampled at various time intervals over 12 months and analysed for 15N and 35S. It is known that soil organic matter accumulates under short-term pastures compared with a long-term pasture in which accumulation and degradation are in balance. Consequently, it was hypothesised that immobilization of urine N and S is more intense in the short-term. However, in this study there was considerably less immobilization of 15N and 35S into soil organic forms under short-term pasture than long-term pasture. This was attributable to a greater pasture dry matter response to urine application under the short-term pasture (due to its inherently low N fertility) resulting in a greater plant uptake of 15N and 35S with less 15N and 35S consequently being available for immobilization. At both sites, all of the applied 35S was accounted for through plant uptake and recovery in the soil, but 21–48% of the 15N was unaccounted for and presumed to have been lost through gaseous emissions. It was concluded that accumulation of soil organic N and S under short-term pastures is likely to be attributable to turnover of plant residues (particularly root material) and does not appear to be related to immobilization in urine patches.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009885413823
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  • 109
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    Nitrogen in percolation water in paddy fields with a rice/wheat rotation (2000)
    Springer
    Nutrient cycling in agroecosystems 57 (2000), S. 75-82 
    Details
    ISSN: 1573-0867
    Keywords: nitrogen ; leaching ; paddy soil ; wheat ; rice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Nitrogen in percolation water was observed in paddy field soil under rice/wheat rotation. Different N-application rates were designed. Porous pipes were installed in triplicate at depths of 30, 60 and 90 cm to collect the water in the period of wheat growth. Suction cups were installed in triplicate at the same depths to collect the water during the period of rice growth. NH4 +, NO3 - and total N in the water were analysed with a continuous-flow nitrogen analyzer. Results showed that nitrate was the predominant form of nitrogen in percolation water during the period of wheat growth. Nitrate leaching was high in early spring after the `tillering fertilisation'. More than 50 mg l-1 of nitrate concentration in percolation water was observed for 30 and 60 cm in depth and more than 15 mg l-1 were observed for 90 cm. The concentration decreased quickly and was very low, less than 2 mg l-1 usually, in the earring stage of wheat. Nitrate in water was low, less than 1.5 mg l-1 usually, when the field was flooded during the period of rice growth. Some soluble organic N existed in the water. Nitrate in percolation water increased when the field was drained. The leaching loss of nitrogen during winter wheat growth period was estimated to be about 3.4% of the N-fertiliser applied at the normal application rate of farmers; for the rice growth period it was around 1.8%. Although a reduced N-application decreased N leaching, it caused a marked decrease in crop yield.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009712404335
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  • 110
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    Nitrogen (N) management in the ‘De Marke’ dairy farming system (2000)
    Springer
    Nutrient cycling in agroecosystems 56 (2000), S. 231-240 
    Details
    ISSN: 1573-0867
    Keywords: nitrogen ; N ; nitrate ; ammonia ; dairy farming ; systems research ; environment ; sandy soils ; groundwater ; leaching
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In the sandy regions of The Netherlands, high losses of N from intensified dairy farms are threatening the environment. Therefore, government defined decreasing maximum levy-free N surplusses for the period 1998–2008. On most dairy farms, the current N surplus has to be reduced by half at least. Farmers fear that realizing these surplusses will be expensive, because it limits application of animal manure, which then has to be exported or additional land has to be bought. Moreover, farmers are worried about the impact on soil fertility. To explore the possibilities for reducing surplusses of average intensive farms by improved nutrient management, farming systems research is carried out at prototype farm ‘De Marke’. Results are compared with results of a commercial farm in the mid-1980s, the moment that systems research started and introduction of the milk quota system put a halt to further intensification. Results indicate that average intensive farms can realise a reduction in N surplus to a level below the defined final maximum, without the need to buy land or to export slurry. Inputs of N in purchased feeds and fertilisers decreased by 56 and 78%, respectively. Important factors are reduced feed intake per unit milk, as a result of a higher milk yield per cow, less young stock and judicious feeding, an improved utilization of ‘home-made’ manure and a considered balance between the grassland and maize area. Changed soil fertility status did not constrain crop production. Nitrate concentration in the upper groundwater decreased from 200 to 50 mg l-1, within a few years.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009885419512
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  • 111
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    Transport of dissolved inorganic nitrogen from the major rivers to estuaries in China (2000)
    Springer
    Nutrient cycling in agroecosystems 57 (2000), S. 13-22 
    Details
    ISSN: 1573-0867
    Keywords: biogeochemistry ; estuary ; nitrogen ; river ; transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Long-term results of the monthly measurement of dissolved inorganic nitrogen (DIN) concentrations in three major rivers in China are presented. These data are combined with river discharge data to calculate the DIN loads discharged into the ocean. About 774.90 × 103, 55.38 × 103and 144.55 × 103tons of DIN were transported to their respective estuaries each year by the Changjiang, the Huanghe and the Zhujiang in 1980–1989, mainly in the form of nitrate (〉 80 percent). The annual transport of DIN and mean concentration of nitrate in the Changjiang had increased drastically (four-fold) in the last 29 years, especially during the 1980s. Although nitrate concentrations of the Zhujiang and the Huanghe had also increased in the 1980s, their total annual loads of DIN varied mainly with annual runoff volumes, showing no obvious uptrends. Our results also demonstrate that the majority of the DIN load of each river was transported in the high-flow period (70–80 percent). A positive relationship is observed between the annual DIN transport of the Changjiang and the annual application of chemical fertilizers in its catchment. The annual DIN loads of the Huanghe and the Zhujiang were influenced mainly by runoff volume, and also by application of chemical fertilizers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009896032188
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  • 112
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    Nitrogen mobilization in Asia (2000)
    Springer
    Nutrient cycling in agroecosystems 57 (2000), S. 1-12 
    Details
    ISSN: 1573-0867
    Keywords: Asia ; fertilizer ; ammonia ; food ; greenhouse effect ; nitrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The addition of anthropogenic N by food and energy production to the global environment contributes to the greenhouse effect, acid deposition, photochemical smog, stratospheric ozone depletion and eutrophication of fresh and marine waters. On a global basis, anthropogenic N mobilization is greater then natural sources of bio-reactive N. Currently, Asia is a hotspot of N mobilization and distribution to downwind and downstream environments, primarily due to food production. Asia's contribution will continue to increase, not only due to population growth, but also to increases in the per capita consumption of food and energy. This paper provides an overview of the global N cycle, presents an analysis of N dynamics within agroecosystems, examines N mobilization in Asia and discusses possible rates of N mobilization in the future.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009832221034
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  • 113
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    Removal of Sulfate, Phosphate and Colored Substances in Wastewater Effluents using Feldspar (2000)
    Springer
    Water resources management 14 (2000), S. 417-434 
    Details
    ISSN: 1573-1650
    Keywords: adsorption ; feldspar ; industrial effluent ; pollution control ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: Abstract Feldspar, among many natural substances such as termitemount-clay, saw-dust, kaolinite and dolomite, offers asignificant removal ability for sulfate, phosphate, and coloredsubstances. Optimization of experimental parameters such assolution pH and flow rate reveals, that the maximum efficiency forremoval of phosphate, sulfate, and colored substances is about42, 52, and 73% respectively. X-ray diffraction, adsorptionisotherm and recovery studies suggest, that the removal processof anions occurs via ion exchange in conjunction with surfaceadsorption. Furthermore, reaction rate studies indicate thatthe removal of the selected pollutants by feldspar follows first-order kinetics. Although the percent removal, under the optimized conditions, is higher for laboratory prepared solutions, efficiency is a little less for industrial effluentsdue to interferent effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011171330097
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  • 114
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    Pruning effects on root distribution and nutrient dynamics in an acacia hedgerow planting in northern Kenya (2000)
    Springer
    Agroforestry systems 50 (2000), S. 59-75 
    Details
    ISSN: 1572-9680
    Keywords: below-ground competition ; carbohydrates ; nitrogen ; nutrient leaching ; resin cores
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Tree pruning is a common management practice in agroforestry for mulching and reducing competition between the annual and perennial crop. The below-ground effects of pruning, however, are poorly understood. Therefore, nutrient dynamics and root distribution were assessed in hedgerow plantings of Acacia saligna (Labill.) H.L. Wendl. after tree pruning. Pruning to a height of 1.5 m was carried out in March and September 1996. In July and October 1996, the fine root distribution (〈 2 mm) and their carbohydrate contents were determined at three distances to the tree row by soil coring. At the same time, foliar nutrient contents were assessed, whereas nutrient leaching was measured continuously. The highest root length density (RLD) was always found in the topsoil (0–0.15 m) directly under the hedgerow (0–0.25 m distance to trees). Pruning diminished the RLD in the acacia plots at all depths and positions. The relative vertical distribution of total roots did not differ between trees with or without pruning, but live root abundance in the subsoil was comparatively lower when trees were pruned than without pruning. In the dry season, the proportion of dead roots of pruned acacias was higher than of unpruned ones, while the fine roots of unpruned trees contained more glucose than those of pruned trees. Pruning effectively reduced root development and may decrease potential below-ground competition with intercropped plants, but the reduction in subsoil roots also increased the danger of nutrient losses by leaching. Leaching losses of such mobile nutrients as NO3− were likely to occur especially in the alley between pruned hedgerows and tended to be higher after pruning. The reduced size of the root system of pruned acacias negatively affected their P and Mn nutrition. Pruning also reduced the function of the trees as a safety net against the leaching of nutrients for both NO3− and Mn, though not for other studied elements. If nutrient capture is an important aim of an agroforestry system, the concept of alley cropping with pruning should be revised for a more efficient nutrient recycling in the system described here.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006498709454
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  • 115
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    Microbalance and Related Studies of High-temperature Superconductors (2000)
    Springer
    Journal of thermal analysis and calorimetry 62 (2000), S. 353-363 
    Details
    ISSN: 1572-8943
    Keywords: controlled environment ; high-T c superconductors ; kinetics ; microgravimetric investigations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Many properties of oxide superconductors depend on the oxygen concentration and its distribution in the samples. The microgravimetric method is very useful to study of oxide superconductors, as it allows investigations in vacuum and controlled environments in classical applications: thermogravimetric analysis for the study of solid-state reactions, determinations of oxygen contents in redox reactions and the combined measurement of mass and additional parameters, e.g. evolved gas analysis etc. Single-phase samples of high-temperature superconductors were synthesized from stoichiometric mixtures of high-purity oxides and carbonates. Appropriate amounts of the precursor powders were homogenized manually or by a mechanical ball mill and subsequently calcined at temperatures in the 800 to 950°C range with intermediate grinding to ensure homogenous reaction. The lattice parameters of all preparations were controlled, in both initial and final experiments, by the X-ray powder method (CuKα radiation), using a Stadi P (Stoe) diffractometer with a position-sensitive detector. It is well known that temperature and mass can be measured with an accuracy higher by orders of magnitude than it is still possible for the thermoanalyst to determine the transformation temperatures or the mass changes due to overlapping partial reactions. Applications of Cahn microbalance to study of high-temperature superconductors are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010192804471
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  • 116
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    Studies on Non-isothermal Kinetics of the Thermal Decomposition of Eu2(BA)6(bipy)2 (2000)
    Springer
    Journal of thermal analysis and calorimetry 62 (2000), S. 747-755 
    Details
    ISSN: 1572-8943
    Keywords: benzoic acid ; europium complex ; kinetics ; non-isothermal ; thermal decomposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The thermal decomposition of Eu2(BA)6(bipy)2 (BA=C2H5N– 2, benzoate; bipy=C10H8N2, 2,2'-bipyridine)and its kinetics were studied under the non-isothermal condition by TG-DTG, IR and SEM methods. The kinetic parameters were obtained from analysis of the TG-DTG curves by the Achar method, the Madhusudanan-Krishnan-Ninan (MKN) method, the Ozawa method and the Kissinger method. The most probable mechanism function was suggested by comparing the kinetic parameters. The kinetic equation for the first stage can be expressed as: dα/dt=Aexp(–E/RT)3(1–α)2/3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026785727479
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  • 117
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    Dsc Evaluations in F.c.c. Solid Solutions of Short-range-order Kinetics As Influenced by Bound Vacancies (2000)
    Springer
    Journal of thermal analysis and calorimetry 63 (2000), S. 397-413 
    Details
    ISSN: 1572-8943
    Keywords: Cu–5 at%Zn ; DSC ; F.C.C. (Face Centered Cubic) ; kinetics ; short-range-order ; solute-vacancy complexes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A modified first order kinetic law, which describes the roles of bound and unbound vacancies, is proposed in order to predict defect decay and short-range-order kinetics of quenched binary alloys during linear heating experiments. The model has been applied to differential scanning calorimetry (DSC) curves of Cu–5 at%Zn quenched from different temperatures. Activation energy for migration of solute-vacancy complexes was also assessed from the kinetics of short-range-order using DSC traces. A value of 89.5±0.32 kJ mol–1 was obtained. The relative contribution of bound and unbound vacancies to the ordering process as influenced by quenching temperature was determined. In conjunction, a parametric study of the initial total defect concentration and effective energy for defect migration was performed in order to envisage their influence on the calculated DSC profiles.
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    Influence of DSC Measurement Conditions on Kinetic Parameters of Thermal Decomposition of 2,4,6-trinitrotoluene (2000)
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 25-33 
    Details
    ISSN: 1572-8943
    Keywords: DSC ; kinetics ; thermal decomposition ; 2,4,6-trinitrotoluene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract An autocatalytic model involving the limited solubility of volatile catalytic products was applied to the thermal decomposition of 2,4,6-trinitrotoluene. The critical supersaturation of the thermal decomposition products with the catalytic properties was higher at a low heating rate. Decrease of the sample mass led to an increased critical supersaturation of the decomposition products. This is probably a result of the greater contribution of products adsorption on the aluminium pan surface. It is presumed that the differences observed in the rate constant are connected with the uncontrolled critical supersaturation of the volatile thermal decomposition products.
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    URL: http://dx.doi.org/10.1023/A:1010108115336
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    Positronium Spin-Conversion Reactions Promoted by 3d Complexes in Highand Low-Spin States (2000)
    Springer
    Structural chemistry 11 (2000), S. 341-346 
    Details
    ISSN: 1572-9001
    Keywords: Positronium chemistry ; kinetics ; spin-exchange reactions ; high- and low-spin 3d complexes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Continuing in our work on the correlations between the rate constants, k CR, of the ortho into para-positronium conversion reactions, CR, promoted by complexes of various 3d ions and the metal electron delocalization β caused by the ligands, the relationship between the parameters of the correlation lines pertinent to highand low-spin complexes of CrII, MnII, and CoII ions was ascertained. Moreover, it was experimentally verified, for the first time, that the statistical probability of the CR promoted by paramagnetic compounds with S = 1/2 is three times larger than that of the CR caused by compounds with S 〉 1/2.
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    Acoustic and Volumetric Virial Coefficients of Nitrogen (2000)
    Springer
    International journal of thermophysics 21 (2000), S. 1033-1044 
    Details
    ISSN: 1572-9567
    Keywords: intermolecular potential ; nitrogen ; speed of sound ; virial coefficients
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Speeds of sound in nitrogen were measured at temperatures between 170 and 400 K at amount-of-substance densities between 40 and 400 mol·m−3. From these measurements, second and third acoustic virial coefficients were obtained. The parameters of two- and three-body isotropic intermolecular potential-energy models were optimized in a simultaneous fit to the second and third acoustic virial coefficients and the ordinary second and third virial coefficients of nitrogen reported by Nowak et al. The results, which shows that the acoustic and ordinary virial coefficients are mutually consistent, may be used to predict second and third virial coefficients, and their acoustic counterparts, over a wide range of temperatures. The parameters of an anisotropic site-site potential-energy model were also obtained from a fit to the acoustic and ordinary second virial coefficients alone.
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    An Improved Greenspan Acoustic Viscometer (2000)
    Springer
    International journal of thermophysics 21 (2000), S. 983-997 
    Details
    ISSN: 1572-9567
    Keywords: acoustic resonator ; argon ; Greenspan viscometer ; helium ; helium-xenon mixture ; methane ; nitrogen ; speed of sound ; viscosity of gases ; xenon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract An improved Greenspan acoustic viscometer (double Helmholtz resonator) was used to measure the viscosity of gases at temperatures from 250 to 400 K and at pressures up to 3.4 MPa. The improvements include a vibration damping suspension and the relocation of the fill duct. The fill duct, which is needed to supply gas to the resonator, was connected to the center of the resonator to eliminate acoustic coupling between the resonator and the manifold. In anticipation of handling corrosive gases, all surfaces of the apparatus that are exposed to the test gas are made of metal. The viscometer was tested with argon, helium, xenon, nitrogen, and methane. Isothermal measurements were carried out at 298.15 and 348.15 K and at pressures up to 3.2 MPa. Without calibration, the results differed from published viscosity data by −0.8% to +0.3% (0.47% r.m.s.). These results are significantly better than previous results from Greenspan viscometers. The measurements also yielded the speed of sound, which differed from literature data by +0.16% to +0.20% (0.18% r.m.s.). Adding empirical effective-area and effective-volume corrections to the data analysis decreased the r.m.s. deviations to 0.12% for the viscosity and to 0.006% for the speed of sound. No unusual phenomena were encountered when the viscometer was tested with a helium-xenon mixture between 250 and 375 K.
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    Tithonia diversifolia as a green manure for soil fertility improvement in western Kenya: A review (2000)
    Springer
    Agroforestry systems 49 (2000), S. 201-221 
    Details
    ISSN: 1572-9680
    Keywords: biomass transfer ; integrated nutrient management ; nitrogen ; nutrient cycling ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Tithonia diversifolia, a shrub in the family Asteraceae, is widely distributed along farm boundaries in the humid and subhumid tropics of Africa. Green biomass of tithonia has been recognized as an effective source of nutrients for lowland rice (Oryza sativa) in Asia and more recently for maize (Zea mays) and vegetables in eastern and southern Africa. This paper reviews the potential of tithonia green biomass for soil fertility improvement based on recent research in western Kenya. Green leaf biomass of tithonia is high in nutrients, averaging about 3.5% N, 0.37% P and 4.1% K on a dry matter basis. Boundary hedges of sole tithonia can produce about 1 kg biomass (tender stems + leaves) m−1 yr−1 on a dry weight basis. Tithonia biomass decomposes rapidly after application to soil, and incorporated biomass can be an effective source of N, P and K for crops. In some cases, maize yields were even higher with incorporation of tithonia biomass than with commercial mineral fertilizer at equivalent rates of N, P and K. In addition to providing nutrients, tithonia incorporated at 5 t dry matter ha−1 can reduce P sorption and increase soil microbial biomass. Because of high labor requirements for cutting and carrying the biomass to fields, the use of tithonia biomass as a nutrient source is more profitable with high-value crops such as vegetables than with relatively low-valued maize. The transfer of tithonia biomass to fields constitutes the redistribution of nutrients within the landscape rather than a net input of nutrients. External inputs of nutrients would eventually be required to sustain production of tithonia when biomass is continually cut and transferred to agricultural land.
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    URL: http://dx.doi.org/10.1023/A:1006339025728
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    An efficient method for in vitro regeneration from immature inflorescence explants of Canadian wheat cultivars (2000)
    Springer
    Plant cell, tissue and organ culture 60 (2000), S. 69-73 
    Details
    ISSN: 1573-5044
    Keywords: cereals ; tissue culture ; Triticum durum ; Triticum aestivum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Fertile, green plants were regenerated from immature inflorescence explants from each of four Canadian wheat cultivars. The cultivars were representative of four classes of Canadian wheat. Explants from immature inflorescences of three size ranges were cultured on two types of media: MSI/MSR, which contains 1650 mg l-1 NH4NO3and sucrose as a carbon source, and BII/BIR, which contains 250 mg l-1 NH4NO3and maltose as a carbon source. Regeneration from all cultivars was significantly better on BII/BIR media than on MSI/MSR media. On BII/BIR media, `AC Karma', `Plenty', and `Fielder' gave the highest number of shoots per 10 explants, where the explants were derived from immature inflorescences 5.1 to 10.0 mm in length. 'Columbus' did not regenerate on MSI/MSR medium, and regenerated poorly on BII/BIR medium. Differences were found between cultivars with regard to the number of regenerant plants produced with the best treatments: `Plenty' produced 16.1 shoots per 10 explants, `AC Karma' 12.4, `Fielder' 6.4, and `Columbus' 2.2.
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    Control and inheritance of resistance to yellow rust in Triticum aestivum-Lophopyrum elongatum chromosome substitution lines (2000)
    Springer
    Euphytica 111 (2000), S. 57-60 
    Details
    ISSN: 1573-5060
    Keywords: biochemical marker ; gene location ; Lophopyrum elongatum ; Puccinia striiformis ; stripe rust ; substitution line ; Triticum aestivum ; yellow rust
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A set of T. aestivum-L. elongatum chromosome substitution lines was tested for yellow rust resistance at the seedling stage. Inheritance of the resistance and esterase-5 (Est-5) variation were studied. The results demonstrated that L.elongatum carried a new gene(s) conferring yellow rust resistance. This gene was dominant and located on chromosome 3E of L. elongatum. The biochemical locus encoding Est-5was also located on chromosome 3E, and co-segregated with theYr gene(s) in the wheat background. The transmission frequencies of chromosome 3E in 3E(3A) × CS, 3E(3B) × CS and 3E(3D) × CS hybrids were scored.None of the hybrids transmitted the alien chromosome at thetheoretical maximum rate, but the transmission frequencies ofchromosome 3E in F2 populations of 3E(3A) × CS and 3E(3D) × CS were significantly higher than in thatof 3E(3B) × CS.
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    Russian wheat aphid-induced protein alterations in spring wheat (2000)
    Springer
    Euphytica 111 (2000), S. 199-203 
    Details
    ISSN: 1573-5060
    Keywords: Diuraphis noxia (Mordvilko) ; protein ; Russian wheat aphid ; Triticum aestivum ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The Russian wheat aphid (RWA), Diuraphis noxia (Mordvilko), has become a perennial, serious pest of wheat (Triticum aestivum L.) in the western United States. Current methodologies used to enhance RWA resistance in wheat germplasm could benefit from an understanding of the biochemical mechanisms underlying resistance to RWA. This study was initiated to identify specific polypeptides induced by RWA feeding that may be associated with RWA resistance. The effects of RWA feeding on PI 140207 (a RWA-resistant spring wheat) and Pavon (a RWA-susceptible spring wheat) were examined by visualizing, silver-stained denatured leaf proteins separated by two-dimensional polyacrylamide gel electrophoresis. Comparisons of protein profiles of noninfested and RWA-infested Pavon and PI 140207 revealed a 24-kilodalton-protein complex selectively inhibited in Pavon that persisted in PI 140207during RWA attack. No other significant qualitative or quantitative differences were detected in RWA-induced alterations of protein profiles. These results suggest that RWA feeding selectively inhibit synthesis and accumulation of proteins necessary for normal metabolic functions in susceptible plants.
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    URL: http://dx.doi.org/10.1023/A:1003866626723
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    Carbon dioxide enrichment and nitrogen fertilization effects on cotton (Gossypium hirsutum L.) plant residue chemistry and decomposition (2000)
    Springer
    Plant and soil 220 (2000), S. 89-98 
    Details
    ISSN: 1573-5036
    Keywords: Carbohydrates ; CO2 ; lignin ; nitrogen ; proanthocyanidins ; soil respiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Increased atmospheric carbon dioxide (CO2) concentration will likely cause changes in plant productivity and composition that might affect soil decomposition processes. The objective of this study was to test to what extent elevated CO2 and N fertility-induced changes in residue quality controlled decomposition rates. Cotton (Gossypium hirsutum L.) was grown in 8-l pots and exposed to two concentrations of CO2 (390 or 722 μmol mol-1) and two levels of N fertilization (1.0 or 0.25 g l-1 soil) within greenhouse chambers for 8 wks. Plants were then chemically defoliated and air-dried. Leaf, stem and root residues were assayed for total non-structural carbohydrates (TNC), lignin (LTGA), proanthocyanidins (PA), C and N. Respiration rates of an unsterilized sandy soil (Lakeland Sand) mixed with residues from the various treatments were determined using a soda lime trap to measure CO2 release. At harvest, TNC and PA concentrations were 17 to 45% higher in residues previously treated with elevated CO2 compared with controls. Leaf and stem residue LTGA concentrations were not significantly affected by either the elevated CO2 or N fertilization treatments, although root residue LTGA concentration was 30% greater in plants treated with elevated CO2. The concentration of TNC in leaf residues from the low N fertilization treatment was 2.3 times greater than that in the high N fertilization treatment, although TNC concentration in root and stem residues was suppressed 13 to 23% by the low soil N treatment. PA and LTGA concentrations in leaf, root and stem residues were affected by less than 10% by the low N fertilization treatment. N concentration was 14 to 44% lower in residues obtained from the elevated CO2 and low N fertilization treatments. In the soil microbial respiration assay, cumulative CO2 release was 10 to 14% lower in soils amended with residues from the elevated CO2 and low N fertility treatments, although treatment differences diminished as the experiment progressed. Treatment effects on residue N concentration and C:N ratios appeared to be the most important factors affecting soil microbial respiration. The results of our study strongly suggest that, although elevated CO2 and N fertility may have significant impact on post-harvest plant residue quality of cotton, neither factor is likely to substantially affect decomposition. Thus, C cycling might not be affected in this way, but via simple increases in plant biomass production.
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    Effect of potassium starvation on the uptake of radiocaesium by spring wheat (Triticum aestivum cv. Tonic) (2000)
    Springer
    Plant and soil 220 (2000), S. 27-34 
    Details
    ISSN: 1573-5036
    Keywords: plant uptake ; potassium ; potassium starvation ; radiocaesium ; Triticum aestivum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Short term experiments were carried out to investigate the effect of internal tissue potassium concentration on the uptake of radiocaesium by spring wheat (Triticum aestivum cv. Tonic). The results showed that potassium starvation increased Cs influx rates by a factor of 10 compared with non-starved plants. Solution to plant tissue transfer factor (TF) values also increased by around an order of magnitude after potassium starvation treatment. The enhancement of Cs influx rates by potassium starvation could be offset by an increase in external potassium concentration: this effect is minimal at external potassium concentrations greater than approximately 200 μM (8 mg L-1). This reveals that Cs influx into plant roots is subject to control by both internal and external potassium status. The kinetics of Cs uptake by potassium in starved and non-starved plants can be described adequately by the Michaelis-Menten equation. It was shown that potassium starvation substantially reduces the Km value from approximately 28 to 6 μM, which suggests that starvation treatment increases significantly the affinity of plant roots for Cs+. Mechanisms involved in K-Cs interactions during plant uptake are discussed in this paper. Finally, the relevance of such mechanisms as determinants of radiocaesium uptake by plants growing under different ecological conditions is emphasised.
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    Nutrient limitations in wet, drained and rewetted fen meadows: evaluation of methods and results (2000)
    Springer
    Plant and soil 220 (2000), S. 35-47 
    Details
    ISSN: 1573-5036
    Keywords: drainage ; fertilisation ; nature management ; nitrogen ; nutrient contents ; nutrients ; peat ; phosphate ; potassium ; restoration ; rewetting ; shoot biomass ; species richness ; wetlands
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Restoration of wet grassland communities on peat soils involves management of nutrient supply and hydrology. The concept of nutrient limitation was discussed as well as its interaction with drainage and rewetting of severely drained peat soils. Different methods of assessing nutrient limitation were compared and the type and extent of nutrient limitation were determined for several wet grassland communities. It was concluded that a full-factorial field fertilisation experiment is the most preferable method. Plant tissue analyses and soil chemical analyses were considered less suitable, although they may provide helpful additional information. Fertilisation experiments in the laboratory using sods or using test plants appear to be the proper means to study mechanisms or processes, but have a restricted predictive value for field situations. Generalising the results, it seems that many relativily undisturbed grassland plant communities on peaty soils are characterised by N limitation. Phosphate limitation for vegetation on peat soils is mainly observed in specific circumstances such as extreme calcium richness, high concentrations of Fe or as a result of drainage or long-term hay cropping. The latter two may also cause K limitation. Rewetting is regarded as a prerequisite in restoring wet grassland communities. Further restoration measures to influence nutrient availability depend on aims of the management and the individual site conditions.
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    Temporal changes in C, P and N concentrations in soil solution following application of synthetic sheep urine to a soil under grass (2000)
    Springer
    Plant and soil 222 (2000), S. 1-13 
    Details
    ISSN: 1573-5036
    Keywords: carbon ; defoliation ; nitrogen ; phosphorus ; sheep urine ; soil solution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract We have determined the temporal changes in the concentration of dissolved organic carbon (DOC) and P and N components in soil solution following application of synthetic sheep urine (500 kg N ha-1) to a brown forest soil in boxes sown with Agrostis capillaris. Three contrasting defoliation treatments (no cutting, single cut before urine application and regular cutting twice per week) plus a fallow soil were studied. The synthetic urine contained 15N labelled urea and was P-free. Intact soil cores were taken after 2, 7, 14, 21 and 56 d and centrifuged to obtain soil solution. The urea in the synthetic urine was rapidly hydrolysed in the soil, increasing soil solution pH, DOC and total dissolved phosphorus (TDP) concentrations. For the regularly defoliated sward, DOC and P reached maximum concentrations (4000 mg DOC L-1 and 59 mg TDP L-1) on day 7. From their peak values, pH and DOC and P concentrations generally decreased with time and at day 56 were near those of the control. Concentrations of NH4 + and NO3 - in the no-urine treatments fluctuated and the greatest treatment differences were between the fallow soil and the soil sown with grass. Adding synthetic urine increased NH4 + concentrations during the first week, but NO3 - concentrations decreased. This was consistent with the 15N labelling of the NO3 - pool which required 3 weeks to reach that of 15NH4 +. Dissolved organic nitrogen (DON) reached a maximum value at day 7 with a concentration of 409 mg N L-1. The DON in soil solution contained no detectable amounts of 15N label indicating that it was derived from sources in the soil. Differences in soil solution composition related to the effect of the other cutting treatments and the fallow treatment were small compared to the effect of synthetic urine addition.
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    Spatial heterogeneity of soil respiration and related properties at the plant scale (2000)
    Springer
    Plant and soil 222 (2000), S. 203-214 
    Details
    ISSN: 1573-5036
    Keywords: carbon ; geostatistics ; nitrification potential ; nitrogen ; pH ; root biomass ; soil respiration ; spatial Heterogeneity ; variability scale
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Geostatistical techniques were used to quantify the scale and degree of soil heterogeneity in 2 m2 plots around 9-year-old poplar trees and within a wheat field. Samples were taken during two years, on an unaligned grid, for analysis of soil respiration, C and N content, available P, gravimetric moisture, pH, nitrification potential, and root biomass. Kriged maps of soil respiration, moisture, and C content showed strong spatial structure associated with poplar trees but not with wheat rows. All soil properties showed higher autocorrelation in June than in April. Isopleth patchiness for all variates was less in June. This was associated with lower respiration rates due to lower litter decomposition. From the degree and scale of heterogeneity seen in this study, we conclude that the main causes of soil heterogeneity at this scale (2 m2) are likely to be found at micro scales controlled in part by plant root and plant residue patterns. These must be understood in the evaluation of ecosystem processes.
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    Long-term effects of elevated atmospheric CO2 on below-ground biomass and transformations to soil organic matter in grassland (2000)
    Springer
    Plant and soil 224 (2000), S. 85-97 
    Details
    ISSN: 1573-5036
    Keywords: carbon ; CO2 enrichment ; nitrogen ; particulate organic matter ; roots ; tallgrass prairie
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract We determined the effects of elevated [CO2] on the quantity and quality of below-ground biomass and several soil organic matter pools at the conclusion of an eight-year CO2 enrichment experiment on native tallgrass prairie. Plots in open-top chambers were exposed continuously to ambient and twice-ambient [CO2] from early April through late October of each year. Soil was sampled to a depth of 30 cm beneath and next to the crowns of C4 grasses in these plots and in unchambered plots. Elevated [CO2] increased the standing crops of rhizomes (87%), coarse roots (46%), and fibrous roots (40%) but had no effect on root litter (mostly fine root fragments and sloughed cortex material 〉500 μm). Soil C and N stocks also increased under elevated [CO2], with accumulations in the silt/clay fraction over twice that of particulate organic matter (POM; 〉53 μm). The mostly root-like, light POM (density ≤1.8 Mg m-3) appeared to turn over more rapidly, while the more amorphous and rendered heavy POM (density 〉1.8 Mg m-3) accumulated under elevated [CO2]. Overall, rhizome and root C:N ratios were not greatly affected by CO2 enrichment. However, elevated [CO2] increased the C:N ratios of root litter and POM in the surface 5 cm and induced a small but significant increase in the C:N ratio of the silt/clay fraction to a depth of 15 cm. Our data suggest that 8 years of CO2 enrichment may have affected elements of the N cycle (including mineralization, immobilization, and asymbiotic fixation) but that any changes in N dynamics were insufficient to prevent significant plant growth responses.
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    Influence of decomposer food web structure and nitrogen availability on plant growth (2000)
    Springer
    Plant and soil 225 (2000), S. 153-165 
    Details
    ISSN: 1573-5036
    Keywords: carbon ; decomposer food web ; indirect effects ; microbes ; nitrogen ; plant growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract We studied the sensitivity of soil microbial communities and ecosystem processes to variation in the vertical and horizontal structure of decomposer food web under nitrogen poor and N-enriched conditions. Microcosms with humus and litter layer of boreal forest floor, birch seedlings infected with mycorrhizal fungi, and decomposer food webs with differing trophic group and species composition of soil fauna were constructed. During the second growing period for the birch, we irrigated half of the microcosms with urea solution, and the other half with de-ionised water to create two levels of N concentration in the substrate. During the experiment night time respirations of the microcosms were measured, and the water leached through the microcosms was analysed for concentration of mineral N, and nematode numbers. The microcosms were destructively sampled after 37 weeks for plant biomass and N uptake, structure of soil animal and microbial community (indicated by PLFA profiles), and physical and chemical properties of the humus and litter materials. Predatory mites and nematodes had a negative influence on the biomass of their microbivorous and microbi-detritivorous prey, and microbi-detritivores affected the biomass and community structure of microbes (indicated by PLFA-analysis). Moreover, predatory mites and nematodes increased microbial biomass and changed the microbial community structure. The decomposer food web structure affected also N uptake and growth of plants. Microbi-detritivorous fauna had a positive effect, whereas predators of microbial and detritus feeding fauna exerted a negative influence on plant N uptake and biomass production. The impact of a trophic group on the microbes and plant was also strongly dependent on species composition within the group. Nitrogen addition magnified the influence of food web structure on microbial biomass and plant N uptake. We suggest that addition of urea-N to the soil modified the animal-microbe interaction by increasing microbial growth and altering community structure of microbes. The presence of microbi-detritivores and predators reduced loss of carbon from the microcosms, and the food web structure influenced also water holding capacity of the materials. The changes in plant growth, nutrient cycling, size of N and C pools, and in the physical properties of the soil emphasize the importance and diversity of indirect consequences of decomposer food web structure.
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    Effects of in vitro treatments on leaf area growth of potato transplants during acclimatisation (2000)
    Springer
    Plant cell, tissue and organ culture 61 (2000), S. 59-67 
    Details
    ISSN: 1573-5044
    Keywords: alar ; in vitro plantlet ; mannitol ; nitrogen ; rooting ; temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The importance of leaf area of in vitro propagated potato (Solanum tuberosum L.) plantlets for further growth during acclimatisation and the after-effects of in vitro treatments on growth were examined. The in vitro treatments included different levels of alar, nitrogen or mannitol or different temperatures during the last in vitro phase, the rooting phase. Leaf area or ground cover was recorded one day after planting to soil and at the end of the first phase of ex vitro growth, the acclimatisation phase. Regression analysis showed that leaf area of a transplant at the end of acclimatisation phase was positively influenced by leaf area of the same plantlet at the beginning of the phase. The relative increase in leaf area during acclimatisation (increase/early leaf area) was linearly related to the inverse of the early leaf area, indicating almost comparable relative increases for plantlets having larger early leaf areas, but more variable responses for plantlets having smaller early leaf areas. In vitro treatments mainly affected leaf area of transplants through their effects on early leaf area. Adding alar, reducing nitrogen and reducing temperature increased leaf area. Reducing mannitol increased ground cover. A lower nitrogen concentration and higher temperature in some cultivars had slight negative effects on the relative increase in leaf area after acclimatisation. For nitrogen these negative effects were less significant than the positive effects through early leaf area. Results stress the importance of manipulation of leaf area in vitro to enhance plant performance in later stages of growth.
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    URL: http://dx.doi.org/10.1023/A:1006442420153
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    Patterns of RFLP-based genetic diversity in germplasm pools of common wheat with different geographical or breeding program origins (2000)
    Springer
    Euphytica 115 (2000), S. 197-208 
    Details
    ISSN: 1573-5060
    Keywords: genetic diversity ; germplasm ; RFLP ; Triticum aestivum ; wheat breeding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A set of 292 accessions of common wheat (Triticum aestivum L.) representing 21 germplasm pools based on geographical or breeding program origins was assayed for RFLP diversity. Thirty cDNA and genomic DNA probes and the HindIII restriction enzyme were employed for RFLP analysis. About 61% of all 233 scored bands were present in 75% or more of the accessions. All but one of the 30 probes revealed polymorphism, and the average number of distinct patterns per probe over all accessions was 9.5.Polymorphic Information Content (PIC) values within a pool varied from 0 to 0.9 and depended on the identities of both the germplasm pool and the probe. Rare banding patterns with a relative frequency of ≤0.2 within a pool were detected. These rare patterns were more likely to occur in pools exhibiting high levels of heterogeneity. The highest level of polymorphism was observed in the Turkish landraces from Southwest Asia. The Eastern U.S. soft red winter wheat germplasm pool was more genetically diverse than the other advanced germplasm pools, and nearly as diverse as the Turkish landrace pool. RFLP-based genetic relationships between germplasm pools generally tracked expectations based on common geographical origin, breeding history and/or shared parentages. The Chinese wheat landraces from Sichuan, Tibet, and Yunnan provinces were distinct from other pools. Similarity matrices for among-pool genetic distance estimates based on either band frequencies or banding pattern frequencies showed good correlation with matrices derived from Nei and Li's mean genetic similarity estimates (r=−0.82** and r=−0.73**, respectively.
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    URL: http://dx.doi.org/10.1023/A:1004022601879
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    Acclimation response of spring wheat in a free-air CO2 enrichment (FACE) atmosphere with variable soil nitrogen regimes. 3. Canopy architecture and gas exchange (2000)
    Springer
    Photosynthesis research 66 (2000), S. 97-108 
    Details
    ISSN: 1573-5079
    Keywords: canopy architecture ; canopy photosynthesis ; CO2 enrichment ; global change ; leaf area index ; leaf tip angle ; nitrogen stress ; Triticum aestivum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The response of whole-canopy net CO2 exchange rate (CER) and canopy architecture to CO2 enrichment and N stress during 1996 and 1997 for open-field-grown wheat ecosystem (Triticum aestivum L. cv. Yecora Rojo) are described. Every Control (C) and FACE (F) CO2 treatment (defined as ambient and ambient +200 μmol mol−1, respectively) contained a Low- and High-N treatment. Low-N treatments constituted initial soil content amended with supplemental nitrogen applied at a rate of 70 kg N ha−1 (1996) and 15 kg N ha−1 (1997), whereas High-N treatments were supplemented with 350 kg N ha−1 (1996 and 1997). Elevated CO2 enhanced season-long carbon accumulation by 8% and 16% under Low-N and High-N, respectively. N-stress reduced season-long carbon accumulation 14% under ambient CO2, but by as much as 22% under CO2 enrichment. Averaging both years, green plant area index (GPAI) peaked approximately 76 days after planting at 7.13 for FH, 6.00 for CH, 3.89 for FL, and 3.89 for CL treatments. Leaf tip angle distribution (LTA) indicated that Low-N canopies were more erectophile than those of High-N canopies: 48° for FH, 52° for CH, and 58° for both FL and CL treatments. Temporal trends in canopy greenness indicated a decrease in leaf chlorophyll content from the flag to flag-2 leaves of 25% for FH, 28% for CH, 17% for CL, and 33% for FL during 1997. These results indicate that significant modifications of canopy architecture occurs in response to both CO2 and N-stress. Optimization of canopy architecture may serve as a mechanism to diminish CO2 and N-stress effects on CER.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010634521467
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    Effect of continuous nutrient enrichment on microalgae colonizing hard substrates (2000)
    Springer
    Hydrobiologia 426 (2000), S. 185-192 
    Details
    ISSN: 1573-5117
    Keywords: nutrient competition ; periphyton ; nitrogen ; silicate ; eutrophication ; benthic microalgae ; hard substrates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In order to understand the effect of changing nutrient conditions on benthic microalgae on hard substrates, in-situ experiments with artificial substrates were conducted in Kiel Fjord, Western Baltic Sea. As an extension of previous investigations, we used artificial substrates without silicate and thus were able to supply nutrient media with different Si:N ratios to porous substrates, from where they trickled out continuously. The biofilm developing on these substrates showed a significant increase in biovolume due to N + P enrichment, while Si alone had only minor effects. The stoichiometric composition of the biomass indicated nitrogen limitation during most of the year. The C:N ratios were lowered by the N + P addition. The algae were dominated by diatoms in most cases, but rhodophytes and chlorophytes also became important. The nutrient treatment affected the taxonomic composition mostly at the species level. The significance of the results with regard to coastal eutrophication is discussed.
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    URL: http://dx.doi.org/10.1023/A:1003943201178
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    Nutrient enrichment of northern rivers in response to pulp mill and municipal discharges (2000)
    Springer
    Journal of aquatic ecosystem stress and recovery 8 (2000), S. 53-66 
    Details
    ISSN: 1573-5141
    Keywords: Canada ; nitrogen ; periphyton ; phosphorus ; pulp mill effluent ; rivers ; sewage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract To evaluate the effects of pulp mill and municipal sewageeffluents on the nitrogen (N) and phosphorus (P) status of northernCanadian rivers, the Northern River Basins Study required an integratedresearch and assessment program consisting of field observation andexperimentation. Analysis of monitoring data collected over 3–13 yshowed that on an annual basis, pulp mills contributed 22% of theP and 20% of the N load discharged from the Wapiti to the Smokyriver, and 6 to 16% of the P load and 4 to 10% of the Nload in the Athabasca River. Despite these low contributions, N and Pconcentrations were elevated below pulp mill discharges on all threerivers during the low discharge period of September to April. Insitu experiments conducted with nutrient diffusing substrata showedthat periphyton biomass was maintained at low levels by insufficient Pin the upper reaches of the Athabasca River and insufficient N+P inthe Wapiti River upstream of point-source discharges. In contrast,effluent loading from pulp mill and sewage inputs alleviated nutrientlimitation downstream of major discharges on both rivers. Experimentsconducted in artificial streams located beside the Athabasca Riverupstream of the first pulp mill showed that P addition increasedperiphyton biomass (expressed as chlorophyll a content) suchthat biomass increased sharply at low P concentrations (2–5µg/L soluble reactive P) and approached saturation at 35µg/L soluble reactive P. As a result of recommendations fromthis integrated program of river monitoring and experimentation,nutrient loading has been reduced to the most affected river(Wapiti-Smoky) and federal and provincial departments of environment arereviewing loading limits for other river reaches.
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    URL: http://dx.doi.org/10.1023/A:1011447907574
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    Influence of light and nitrogen on the phlorotannin content of the brown seaweeds Ascophyllum nodosum and Fucus vesiculosus (2000)
    Springer
    Hydrobiologia 440 (2000), S. 299-305 
    Details
    ISSN: 1573-5117
    Keywords: Ascophyllum ; Fucus ; CNBM ; light ; nitrogen ; phlorotannins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Phlorotannins, C-based defence compounds in brown seaweeds, show a high degree of spatial and temporal variation within seaweed species. One important model explaining this variation is the Carbon Nutrient Balance Model (CNBM), which states that the relative supply of carbon and limiting nutrients will determine the level of defence compounds in plants. Nitrogen is often considered to be the limiting nutrient for marine macroalgal growth and the CNBM thus predicts that when the carbon:nitrogen ratio is high, photosynthetically fixed carbon will be allocated to production of phlorotannins. In the present study, we evaluated the effects of light (i.e. carbon) and nitrogen on the phlorotannin content of two intertidal brown seaweeds, Ascophyllum nodosum and Fucus vesiculosus. This was done in an observational field study, as well as in a manipulative experiment where plants from habitats with different light regimes were subjected to different nitrogen and light treatments, and their phlorotannin content was measured after 14 days. The results showed that there was a negative relationship between tissue nitrogen and phlorotannin content in natural populations of F. vesiculosus, but not in A. nodosum. In the short term, the phlorotannin content in both algal species was not affected by changes in nitrogen availability. Exposure to sunlight had a positive effect on the phlorotannin content in natural populations of both algal species but, in the manipulative experiment, only F. vesiculosus showed a rapid response to changes in light intensities. Plants subjected to sunlight contained higher phlorotannin content than shaded plants. In conclusion, the results imply that nitrogen availability explains some of the natural variation in the phlorotannin content of F. vesiculosus, but the light environment has greater importance than nitrogen availability in predicting the phlorotannin content of each species.
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    URL: http://dx.doi.org/10.1023/A:1004152001370
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    Light- and nutrient-limited periphyton in low order streams of Oahu, Hawaii (2000)
    Springer
    Hydrobiologia 432 (2000), S. 101-111 
    Details
    ISSN: 1573-5117
    Keywords: Hawaii ; light ; nitrogen ; nutrients ; periphyton ; phosphorus ; spate ; stream
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract To date, most studies of light- and nutrient-limited primary productivity in forested streams have been carried out in deciduous forests of temperate, continental regions. Conceptual models of light and nutrient limitation have been developed from these studies, but their restricted geographic range reduces the generality of such models. Unlike temperate continental streams, streams on tropical high islands are characterized by flashy, unpredictable discharge and riparian canopies that do not vary seasonally. These contrasting conditions suggest that patterns of light and nutrient limitation in tropical streams may differ from those in temperate streams. The effects of light, and nitrogen and phosphorus availability on periphyton accrual (measured as chlorophyll a per unit area) were investigated using field experiments in 4 low-order streams on the island of Oahu, Hawaii. Levels of chlorophyll a in partially-shaded stream pools were significantly greater than in heavily-shaded pools, and nutrient-enrichment increased the level of chlorophyll a in partially-shaded pools but not in heavily-shaded pools. In each stream, phosphate enrichment resulted in an increase in the level of chlorophyll a, but nitrate enrichment had no effect. Spates following rainstorms occur frequently in these streams, and may increase periphyton productivity by increasing the flux of nutrients to algal cells. However, differences in inorganic nitrogen and phosphorus concentrations measured during spates and baseflow were small, and during some spates, concentrations of these two nutrients declined relative to baseflow concentrations. These observations suggest that phosphorus limitation was not alleviated by spates.
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    URL: http://dx.doi.org/10.1023/A:1004074004416
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    Dissolved organic nitrogen budgets for upland, forested ecosystems in New England (2000)
    Springer
    Biogeochemistry 49 (2000), S. 123-142 
    Details
    ISSN: 1573-515X
    Keywords: C:N ratio ; dissolved organic carbon ; dissolved organic nitrogen ; nitrogen ; stream chemistry ; watershed
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Relatively high deposition ofnitrogen (N) in the northeastern United States hascaused concern because sites could become N saturated.In the past, mass-balance studies have been used tomonitor the N status of sites and to investigate theimpact of increased N deposition. Typically, theseefforts have focused on dissolved inorganic forms ofN (DIN = NH4-N + NO3-N) and have largelyignored dissolved organic nitrogen (DON) due todifficulties in its analysis. Recent advances in themeasurement of total dissolved nitrogen (TDN) havefacilitated measurement of DON as the residual of TDN− DIN. We calculated DON and DIN budgets using data onprecipitation and streamwater chemistry collected from9 forested watersheds at 4 sites in New England. TDNin precipitation was composed primarily of DIN. Netretention of TDN ranged from 62 to 89% (4.7 to 10 kghaminus 1 yrminus 1) of annual inputs. DON made up themajority of TDN in stream exports, suggesting thatinclusion of DON is critical to assessing N dynamicseven in areas with large anthropogenic inputs of DIN.Despite the dominance of DON in streamwater,precipitation inputs of DON were approximately equalto outputs. DON concentrations in streamwater did notappear significantly influenced by seasonal biologicalcontrols, but did increase with discharge on somewatersheds. Streamwater NO3-N was the onlyfraction of N that exhibited a seasonal pattern, withconcentrations increasing during the winter months andpeaking during snowmelt runoff. Concentrations ofNO3-N varied considerably among watersheds andare related to DOC:DON ratios in streamwater. AnnualDIN exports were negatively correlated withstreamwater DOC:DON ratios, indicating that theseratios might be a useful index of N status of uplandforests.
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    URL: http://dx.doi.org/10.1023/A:1006383731753
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    Atmospheric deposition and watershed nitrogen export along an elevational gradient in the Catskill Mountains, New York (2000)
    Springer
    Biogeochemistry 50 (2000), S. 21-43 
    Details
    ISSN: 1573-515X
    Keywords: acid deposition ; atmospheric deposition ; nitrate ; nitrification ; nitrogen ; soil carbon ; soil chemistry ; stream water acidification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Cumulative effects of atmospheric N deposition mayincrease N export from watersheds and contribute tothe acidification of surface waters, but naturalfactors (such as forest productivity and soildrainage) that affect forest N cycling can alsocontrol watershed N export. To identify factors thatare related to stream-water export of N, elevationalgradients in atmospheric deposition and naturalprocesses were evaluated in a steep, first-orderwatershed in the Catskill Mountains of New York, from1991 to 1994. Atmospheric deposition of SO 4 2− , andprobably N, increased with increasing elevation withinthis watershed. Stream-water concentrations ofSO 4 2− increased with increasing elevationthroughout the year, whereas stream-waterconcentrations of NO 3 − decreased withincreasing elevation during the winter and springsnowmelt period, and showed no relation with elevationduring the growing season or the fall. Annual exportof N in stream water for the overall watershed equaled12% to 17% of the total atmospheric input on thebasis of two methods of estimation. This percentagedecreased with increasing elevation, from about 25%in the lowest subwatershed to 7% in the highestsubwatershed; a probable result of an upslope increasein the thickness of the surface organic horizon,attributable to an elevational gradient in temperaturethat slows decomposition rates at upper elevations. Balsam fir stands, more prevalent at upper elevationsthan lower elevations, may also affect the gradient ofsubwatershed N export by altering nitrification ratesin the soil. Variations in climate and vegetationmust be considered to determine how future trends inatmospheric deposition will effect watershed export ofnitrogen.
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    URL: http://dx.doi.org/10.1023/A:1006332230890
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    Carbon, nitrogen and phosphorus cycling in rivermarginal wetlands; a model examination of landscapegeochemical flows (2000)
    Springer
    Biogeochemistry 50 (2000), S. 45-71 
    Details
    ISSN: 1573-515X
    Keywords: carbon ; landscape geochemical flows ; model ; nitrogen ; phosphorus ; wetland
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The importance of landscape geochemical flows wasinvestigated using a dynamic model simulating carbon,nitrogen and phosphorus cycling in riverine wetlands,which has been described in a previous paper. Thehydro-geomorphic unit (HGMU) concept was incorporatedin the model by defining a separate, completeunit-model for each unit (HGMU) within the wetland.These unit-models were connected by defining the flowsof nitrogen and phosphorus between them. These flows,also called landscape geochemical flows, usuallyconsist of flows of water containing N and P. The model was applied to a site at Kismeldon Meadows,in south-western England. This site consists of twounits, a slope and a floodplain, separated by a ditch,which catches most of the run off and shallowgroundwater flows from the slope. Only an estimated1% of the N and P that leaves the slope unit in thewater outflow reaches the floodplain unit; the rest iscaught in the system of ditches, which prevent thegeochemical flows taking their natural course. Toexamine the influence of this system of ditches, themodel was run for the same site, but without theditches. This is comparable to a situation of arestored site, where run off and shallow groundwaterflows containing nutrients, can freely get from theslope to the floodplain. The computer simulation experiment reconnecting theslope and floodplain showed that this (1) increasedthe nutrient input into the floodplain, causing ahigher biomass production, and (2) increased thewetness of the floodplain, causing slowerdecomposition, which together (3) led to a faster soilorganic matter accumulation in the floodplain.Nutrient inflows became relatively more importantcompared to atmospheric deposition, especially forphosphorus. By connecting the slope and the floodplainmore nitrogen and less phosphorus flowed into theriver.
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    URL: http://dx.doi.org/10.1023/A:1006360315792
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    Internal eutrophication in peat soils through competition between chloride and sulphate with phosphate for binding sites (2000)
    Springer
    Biogeochemistry 50 (2000), S. 183-194 
    Details
    ISSN: 1573-515X
    Keywords: chloride ; internal eutrophication ; nitrogen ; peat soil ; phosphorus ; phytometer ; sulphate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Inputs of surface waters high in chloride and sulphateincreased the availability of nutrients in fenpeatlands. This `internal eutrophication' wasdemonstrated with test plants (`phytometers') andthrough water and soil analysis. Three experiments arepresented in which the level of chloride and/orsulphate was increased to 3 mmolc l−1. Inexperiment 1 chloride levels were increased from 0.5to 3 mmolc l−1 as CaCl2 or NaCl. Inexperiment 2 and 3 similar increased levels forchloride and sulphate (3 mmolc l−1; as NaCland Na2SO4) were used. The following resultswere found: (i) No differences in soil total-N and total-P werefound before and after the treatments in any of thethree experiments. (ii) Experiment 1 showed a significant increase inBio-Available P (BAP) in pots planted with Anthoxanthum odoratum as well as in bare pots for theNaCl and CaCl2 treatments. The plants in thesetreatments had taken up much more P. (iii) Experiment 2 showed an increase in soil BAPafter treatment with chloride and sulphate in potsplanted with Anthoxanthum odoratum. The chloridetreatment had no effect on plant biomass, whereas thesulphate treatment resulted in a reduction in rootbiomass and root N and P content. The shoots showedan increase in P content in the sulphate and chloridetreatments, while N content remained the same. (iv) In experiment 3, treatments with chloride andsulphate led to significantly increased biomass and Puptake of Anthoxanthum odoratum. Again, noeffects on N uptake were found. These experiments provide evidence for distinctlyincreased availability of phosphate in peat soils whenthese come into contact with water with evenmoderately increased sulphate or chloride levels.Surface water originating from the Rhine river, whichis enriched in chloride and sulphate, is oftensupplied to fen reserves in The Netherlands, tocompensate for water losses due to agriculturaldrainage in the region. The results of this study showthat phosphate availability to the vegetation may risedrastically, with detrimental effects on the speciesdensity and the occurrence of rare species in thevegetation. Hence, supply of this water should beavoided.
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    Meiotic metaphase I pairing behavior of a 5BL recombinant isochromosome in wheat (2000)
    Springer
    Chromosome research 8 (2000), S. 671-676 
    Details
    ISSN: 1573-6849
    Keywords: meiotic metaphase I pairing ; recombinant isochromosome ; Triticum aestivum ; Triticum dicoccoides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A recombinant isochromosome i5BLrec of wheat was developed with one arm and the proximal 36% of the other arm of Chinese Spring (CS) origin and the distal 64% of the recombined arm of Triticum turgidum subsp. dicoccoides origin. The i5BLrec} provides an unusual opportunity to analyze the role of the centromere or arm heterozygosity in chromosome prealignment and synapsis during meiosis. In monosomic condition, the i5BLrec formed a ring univalent in 86.8% of the pollen mother cells (PMCs) at meiotic metaphase I. In the disomic condition, the two i5BLrec preferentially paired as a normal bivalent in 74.8% of the PMCs, which differed significantly (p〈0.01) from the normal bivalent pairing of 51% observed in diisosomic 5BL chromosomes of the CS (Di5BLCS) control plants. In plants with one i5BLrec and a normal 5BCS, the long arm of 5BCS paired with the homologous arm of i5BLrec in 54.4% of the PMCs, and 40.4% of the PMCs had a 5BCS univalent and a i5BLrec ring univalent. The implications of the i5BLrec pairing data on the mechanism of Ph1 gene action are discussed.
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    Gametocidal factor-induced structural rearrangements in rye chromosomes added to common wheat (2000)
    Springer
    Chromosome research 8 (2000), S. 501-511 
    Details
    ISSN: 1573-6849
    Keywords: BFB cycle ; chromosome healing ; gametocidal factor ; rye deficiencies ; Secale cereale ; Triticum aestivum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The gametocidal factor on the Aegilops cylindrical chromosome 2Cc was used to induce and analyze the nature of chromosomal rearrangements in rye chromosomes added to wheat. For this purpose we isolated plants disomic for a given rye chromosome and monosomic for 2Cc and analyzed their progenies cytologically. Rearranged rye chromosomes were identified in 7% of the progenies and consisted of rye deficiencies (4.6%), wheat–rye dicentric and rye ring chromosomes (1.8%), and terminal translocations (0.6%). The dicentric and ring chromosomes initiated breakage–fusion–bridge cycles (BFB) that ceased within a few weeks after germination as the result of chromosome healing. Of 56 rye deficiencies identified, after backcrossing and selfing, only 33 were recovered in either homozygous or heterozygous condition covering all rye chromosomes except 7R. The low recovery rate is probably caused by the presence of multiple rearrangements induced in the wheat genome that resulted in poor plant vigor and seed set, low transmission, and an underestimation of the frequency of wheat–rye dicentric chromosomes. Genomic in-situ hybridization (GISH) analysis of the 33 recovered rye deficiencies revealed that 30 resulted from a single break in one chromosome arm followed by the loss of the segment distal to the breakpoint. Only three had a wheat segment attached distal to the breakpoint. Although some of the Gc-induced rye rearrangements were derived from BFB cycles, all of the recovered rye rearrangements were simple in structure. The healing of the broken chromosome ends was achieved either by the de-novo addition of telomeric repeats leading to deficiencies and telocentric chromosomes or by the fusion with other broken ends in the form of stable monocentric terminal translocation chromosomes.
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    Using Bacterial Growth on Insects to Assess Nutrient Impacts in Streams (2000)
    Springer
    Environmental monitoring and assessment 63 (2000), S. 431-446 
    Details
    ISSN: 1573-2959
    Keywords: aquatic bacteria ; benthic macroinvertebrates ; bioindicator ; eutrophication ; nitrogen ; phosphorus ; stream pollution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract A combination field and laboratorystudy was conducted to evaluate the ability of arecently developed bioindicator to detect detrimentalnutrient conditions in streams. The method utilizesbacterial growth on aquatic insects to determinenutrient impacts. Field investigations indicated thatelevated concentrations of nitrate and phosphate wereassociated with growth of filamentous bacteria oninsect body surfaces, and that there was a significantreduction in the density of major insect taxa in thenutrient-enriched stream reaches. Laboratoryinvestigations confirmed a strong linkage betweenbacterial growth and reduced survival of insects. Survival was examined for insects with bacterialinfestation ranging from 0% to greater than 50%coverage of the body surface. A threshold forcatastrophic mortality occurred at about 25% bodycoverage; there were few survivors above that amount. Based on these findings, the diagnostic endpoint forthe bioindicator is 25% body coverage by bacterialgrowth, a level that signifies major impacts and isalso easy to detect visually. This study providesadditional evidence that the insect-bacteriabioindicator is a reliable tool for assessing nutrientimpacts on stream macroinvertebrate communities. Thebioindicator should prove useful for identifyingnutrient-impacted sites as well as monitoring thesuccess of management actions to improve water quality.
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    URL: http://dx.doi.org/10.1023/A:1006211929599
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    Input–Output Budgets of Major Ions for a Forested Watershed in Western Maryland (2000)
    Springer
    Water, air & soil pollution 119 (2000), S. 121-137 
    Details
    ISSN: 1573-2932
    Keywords: nitrogen ; wet deposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract We measured concentrations and fluxesof major ions in wet deposition, throughfall andstream water in a forested watershed on the AlleghenyPlateau of western Maryland to investigatecanopy-atmosphere interactions and to calculate input–output budgets. Wet deposition was dominated byH+, SO 4 2− , NO 3 − andNH 4 + ions. Hydrogen and SO 4 2− accounted for 70 and 58% of the total cation andanion equivalents, respectively. Annual wet depositionrates of SO 4 2− (0.56 keq ha−1 yr−1), NO 3 − (0.31 keq ha−1 yr −1)and NH 4 + (0.17 keq ha−1 yr −1)were at the high end of the range in wet depositionrates reported for other sites in the eastern UnitedStates. On an annual basis, the forest canopy consumed20% of the free acidity in incident precipitation,had no net effect on Na+ and NH 4 + deposition, and was a net source of K+,Ca2+, Mg2+, SO 4 2− andNO 3 − ; 1.5 to 22 times greater than the wetdeposition rates. On an annual basis, the watershed ofthe unnamed tributary to Herrington Creek (HCWS)retained essentially all of the throughfall H+ andNH 4 + inputs, 35% of the throughfall K+input and 62% of the throughfall NO 3 − input. In contrast, HCWS was a net source ofSO 4 2− , Cl−, Ca2+, Mg2+ andNa+; export rates were 2 to 5 times greater thanthroughfall inputs. Sulfate was the dominant anionassociated with cation leaching, accounting for 78%of the total anion export of 1.8 keq ha−1 yr −1 in 1996–1997.
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    URL: http://dx.doi.org/10.1023/A:1005113426448
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    Efficiency of the muon catalyzed fusion in triple H/D/T mixtures (2000)
    Springer
    Hyperfine interactions 128 (2000), S. 481-493 
    Details
    ISSN: 1572-9540
    Keywords: muon catalyzed fusion ; triple mixture ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In this paper, we solve numerically kinetic equations for the chain reactions of μCF in triple H/D/T mixture. Regarding the computational results, we show that μCF efficiency decreases by adding hydrogen H to D/T mixture. This is in contradiction to the usual belief which expects the increase of μCF efficiency in H/D/T mixture. Our results are confirmed by the first and recent experiment on μdt cycling rate in the triple mixture.
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    Kinetics of Acetic Acid Esterification with 2-Methoxyethanol Over a Pillared Clay Catalyst (2000)
    Springer
    Reaction kinetics and catalysis letters 69 (2000), S. 169-176 
    Details
    ISSN: 1588-2837
    Keywords: Al3+-exchanged pillared clay catalyst ; 2-methoxyethanol ; esterification ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The pillared clay catalyst, which was obtained by exposing activated clay powder to sulfuric acid and aluminium salts and calcining in air at 373 – 673 K, was found to be highly active for the title reaction. The activity is mainly attributed to the Lewis acid sites and also to a small number of Brönsted acid sites, whose number and strength increases with the extent of pillaring. The kinetic equation of surface esterification is y = 2.57x - 1.47.
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    The Kinetics of Tenoxicam Photodegradation in Solution (2000)
    Springer
    Reaction kinetics and catalysis letters 70 (2000), S. 119-124 
    Details
    ISSN: 1588-2837
    Keywords: Tenoxicam ; photodegradation ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Photodegradation of tenoxicam was investigated under different reaction conditions. After 60 min of exposure to UV light, the photodegradation was extensive, and the maximum and minimum in the UV-visible spectrum were shifted to shorter and longer wavelengths, respectively. Ethanol exerted a photostabilizing effect on tenoxicam. Tenoxicam is more stable in acidic and basic media than in neutral solution. Increasing light intensity or temperature causes an increase in the rate of photodegradation. The photodegradation of tenoxicam was found to follow first-order kinetics under all these conditions.
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    URL: http://dx.doi.org/10.1023/A:1010370901272
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    Kinetics of the N-Monoalkylation of Aniline with Methanol Over Zn1−XCoXFe2O4 (X = 0, 0.2, 0.5, 0.8 and 1.0)-Type Systems (2000)
    Springer
    Reaction kinetics and catalysis letters 70 (2000), S. 161-167 
    Details
    ISSN: 1588-2837
    Keywords: Ferrites ; aniline alkylation ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Kinetic parameters such as the activation energy (Ea) and Arrhenius frequency factor (A) for the N-methylation of aniline using methanol over Zn-Co ferrites have been calculated. The Ea value is found to be lower than the existing best alkylating systems such as γ-alumina and magnesium oxide.
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    Kinetics and Mechanism of the Oxidative Regeneration of Carbonyl Compounds from Oximes by Pyridinium Fluorochromate (2000)
    Springer
    Reaction kinetics and catalysis letters 71 (2000), S. 343-347 
    Details
    ISSN: 1588-2837
    Keywords: Deoximination ; chromium (VI) ; kinetics ; mechanism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Oxidative deoximination of aldoximes and ketoximes by pyridium fluorochromate proceeds by nucleophilic attack of the chromate oxygen on the oxime carbon to give a cyclic intermediate in the rate-determining step.
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    Homogeneous Catalysis of C-H Bond Activation by a Novel Ruthenium(III)-Complex (2000)
    Springer
    Reaction kinetics and catalysis letters 70 (2000), S. 147-151 
    Details
    ISSN: 1588-2837
    Keywords: Oxo-functionalization ; [RuIII(amp)(pic)(H2O)] ; t-BuOOH ; kinetics ; cyclohexane cyclohexene ; toluene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A novel mixed-ligand [RuIII(amp)(pic)(H2O)] complex (1) (H2amp = N-(hydroxyphenyl)salicyldimine; pic = picolinate) has been synthesized and characterized by physico-chemical methods. Complex 1has been found to be an effective catalyst in oxo-functionalization of C-H bond of organic substrates by using tert-butyl hydroperoxide (t-BuOOH) as a terminal oxidant. Formation of a high valent Ru(V)-oxo species as catalytic intermediate is proposed to be the source of oxygen atom in the oxidised product.
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    Study of the Ligand Substitution Reaction [Fe(CN)5(4-tbupy)]3- + Pyrazine in Concentrated Aqueous Electrolyte Solutions: Estimation of the Activation Volume (2000)
    Springer
    Reaction kinetics and catalysis letters 70 (2000), S. 389-394 
    Details
    ISSN: 1588-2837
    Keywords: Fe(CN)5(4-tbupy)3- ; kinetics ; electrolytes ; substitution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The ligand substitution reaction [Fe(CN)5(4-tbupy)]3- + pyrazine (4-tbupy=4-tertbutylpyridine) was studied in aqueous concentrated electrolyte solutions at 298 K. Plots of ln(k/kw) against (γ-γw), where the subscript w refers to pure water and γ is the surface tension of the appropriate salt solution, gave a common straight line for all the electrolytes studied and permits to estimate the activation volume.
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    Kinetics of Coke Formation for the Reactions of Light Olefins Ethene, Propene and 1-Butene Over Ushy Zeolite (2000)
    Springer
    Reaction kinetics and catalysis letters 69 (2000), S. 39-46 
    Details
    ISSN: 1588-2837
    Keywords: Coke formation ; kinetics ; USHY zeolites ; ethene ; propene ; 1-butene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A simplified three-parameter model for the interpretation of the kinetic data of coke formation during transformation of light olefins is presented. This model has been applied to the transformation of ethene, propene and 1-butene over fresh and regenerated zeolite USHY at 623 K. The proposed model covers both the coverage of the acid sites and the autocatalytic growth of coke.
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    Regioselective Dichlorocyclopropanation of 4-Vinyl-1-Cyclohexene Using the New Diquat, DQ-Br, under Controlled Phase Transfer Catalysis Conditions (2000)
    Springer
    Reaction kinetics and catalysis letters 69 (2000), S. 161-167 
    Details
    ISSN: 1588-2837
    Keywords: Dichlorocyclopropanation ; 4-vinyl-1-cyclohexene ; phase transfer catalysis ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics of regioselective dichlorocyclopropanation of 4-vinyl-1-cyclohexene has been studied under controlled phase transfer catalysis conditions, using aqueous sodium hydroxide as the base and 2-benzylidine-N,N,N,N′,N′,N′-hexaethylpropane-1,3-diammonium dibromide (Dq-Br) as a new phase transfer reagent. The reaction was carried out at 40 °C under pseudo-first order conditions by employing aqueous sodium hydroxide and chloroform in excess and was monitored by gas chromatography. The effect of various experimental parameters on the rate of the reaction has been studied and based on the experimental results, a suitable mechanism is proposed.
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    Kinetics of Oxidation of Phosphinic, Phenylphosphinic and Phosphorous Acid by Benzyltrimethylammonium Chlorobromate (2000)
    Springer
    Reaction kinetics and catalysis letters 69 (2000), S. 247-252 
    Details
    ISSN: 1588-2837
    Keywords: Phosphorous acid ; oxidation ; kinetics ; mechanism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The oxidation of lower phosphorus oxyacids by benzyltrimethylammonium chlorobromate (BTMACB) proceeds by a mechanism involving a hydride-ion transfer from oxyacids to the oxidant in the rate-determining step.
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    Low-Temperature Catalytic Oxidation of Sulfide Ions in Aqueous Solutions on a Ni-Oxide System (2000)
    Springer
    Reaction kinetics and catalysis letters 70 (2000), S. 139-145 
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    ISSN: 1588-2837
    Keywords: Oxidation of sulfides ; kinetics ; Ni-oxide system ; reaction mechanism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Catalytic oxidation of sulfide ions in aqueous solutions by air oxygen has been investigated using a Ni-oxide system as a catalyst. The kinetics and the selectivity of the oxidation process were studied by varying the pH, catalyst amount and reaction temperature. A reduction/oxidation mechanism of the reaction has been supposed comprising interaction between the surface active oxygen of the catalyst and HS− and reoxidizing of the reduced catalyst by the dissolved oxygen. The results obtained show that the Ni-oxide system is a promising catalyst for practical application.
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    Coupling of Methanol and Isobutanol to Ethers over γ-Alumina Catalyst. Kinetic Studies (2000)
    Springer
    Reaction kinetics and catalysis letters 70 (2000), S. 235-241 
    Details
    ISSN: 1588-2837
    Keywords: Methanol ; isobutanol ; ethers ; γ-Al2O3 ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetic of methanol (MeOH) and isobutanol (iBuOH) coupling to ethers has been studied. Catalytic tests were carried out in the gas phase in a fixed-bed flow microreactor, in the temperature range of 463-533 K, under atmospheric pressure, using γ-Al2O3 as the catalyst. The quasi-homogeneous model for the process was assumed. The reaction rates were described by simple kinetics.
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    Rate Constant for the Reaction of the OH-Radical with CH2F2 (2000)
    Springer
    Reaction kinetics and catalysis letters 70 (2000), S. 319-324 
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    ISSN: 1588-2837
    Keywords: Atmospheric chemistry ; kinetics ; OH-radical ; CH2F2
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The rate constant value of k 1 = (6.05 ± 0.20)×109 cm3 mol−1 s−1 (with ± 1σ error) has been determined for the reaction OH + CH2F2 (1) by applying the discharge-flow/resonance-fluorescence method at 298 K.
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    Kinetics and Stereoselectivity in Gas-Phase Hydrogenation of Alkylbenzenes Over Ni/Al2O3 (2000)
    Springer
    Reaction kinetics and catalysis letters 71 (2000), S. 47-54 
    Details
    ISSN: 1588-2837
    Keywords: Alkylbenzenes ; hydrogenation ; nickel ; kinetics ; stereochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Experimental data on gas-phase hydrogenation of several alkylbenzenes (toluene, ethlylbenzene, o-, m-, p-xylenes, mesitylene) over nickel catalyst are summarized. Rate dependence as a function of the chemical nature of substituent and position in the aromatic ring is discussed. The stereochemical distribution for dialkylbenzene and trialkylbenzene is addressed.
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    Determination of Equilibrium Dispersion of Pt on Al2O3 Support in Sintering Process (2000)
    Springer
    Reaction kinetics and catalysis letters 71 (2000), S. 295-300 
    Details
    ISSN: 1588-2837
    Keywords: Sintering ; kinetics ; Pt/Al2O3
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The variation of dispersion of Pt on Al2O3 support with sintering time is measured and the value of equilibrium dispersion of Pt is obtained directly. It is found that a General Power Law Expression can fit the experimental data well.
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    Photosystem 2 Efficiency and Thylakoid Protein Pattern in DCMU-Treated Wheat Seedlings during Senescence (2000)
    Springer
    Photosynthetica 38 (2000), S. 607-614 
    Details
    ISSN: 1573-9058
    Keywords: chlorophyll fluorescence ; diphenyl carbazide ; donor side ; electron transport ; MnCl2 ; NH2OH ; photosystem ; senescence ; thylakoid protein ; Triticum aestivum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Changes in various components of photosynthetic apparatus during the 6-d dark incubation at 25 °C of detached control and DCMU-treated Triticum aestivum L. leaves were examined. The rate of photosystem 2 (PS2) activity was decreased with increase of the time of dark incubation in control leaves. In contrast to this, DCMU-treated leaves demonstrated high stability by slowing down the inactivation processes. Diphenyl carbazide and NH2OH restored the PS2 activity more in control leaves than in DCMU-treated leaves. Mn2+ failed to restore the PS2 activity in both control and DCMU-treated samples. Similar results were obtained when Fv/Fm was evaluated by chlorophyll fluorescence measurements. The marked loss of PS2 activity in dark incubated control leaves was primarily due to the loss of D1, 33, and 23 kDa extrinsic polypeptides and 28-25 kDa LHCP2 polypeptides.
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    Relationship between Carbon and Nitrogen Metabolisms in Photosynthesis. The Role of Photooxidation Processes (2000)
    Springer
    Photosynthetica 37 (2000), S. 519-527 
    Details
    ISSN: 1573-9058
    Keywords: alanine ; aspartate ; glycine ; glycollate ; malate ; nitrate ; serine ; sugars ; Triticum aestivum ; urea ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 14CO2 uptake in leaves of wheat plants (Triticum aestivum L.) fertilized by urea or Ca(NO3)2 (25 mol m-3) was investigated. The Warburg effect (inhibition of 14CO2 uptake by oxygen) under 0.03 vol. % CO2 concentration was observed only in non-fertilized plants. Under 0.03 vol. % CO2, the Warburg antieffect (stimulation of 14CO2 uptake by oxygen) was detected only in plants fertilized by Ca(NO3)2. Under saturating CO2 concentration (0.30 vol. %), the Warburg antieffect was observed in all variants. Under limitation of ribulose-1,5-bisphosphate carboxylase/oxygenase activity (0.30 vol. % CO2 + 1 vol. % O2), the rate of synthesis of glycollate metabolism products decreased in control and urea-fertilized plants but was enhanced in nitrate-fed plants. Hence, there was an activation of glycollate formation via transketolase reaction in fertilized plants, and the products of nitrate reduction function were oxidants in nitrate-fertilized plants whereas the superoxide radical played this role in urea-fertilized plants.
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    Diurnal Oscillation in the Intercellular CO2 Concentration of Spring Wheat Under the Semiarid Conditions (2000)
    Springer
    Photosynthetica 38 (2000), S. 187-192 
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    ISSN: 1573-9058
    Keywords: net photosynthetic rate ; soil and atmospheric drought ; stomatal conductance ; Triticum aestivum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Yields of wheat in semiarid and arid zones are limited by drought, and water condition is very important at each stage of development. Studies carried out at Loess Plateau in the northwestern part of China indicated that yield of spring wheat (Triticum aestivum L.) cv. Dingxi 81-392 was reduced by 41% when subjected to water stress. The effects of two water regimens on net photosynthetic rate (P N), stomatal conductance (g s), and intercellular CO2 concentration (C i) were investigated at the jointing, booting, anthesis, and grain filling stages. Low soil moisture in comparison to adequate one had invariably reduced P N during the diurnal variations at the four growth stages. P N and g s in both soil moisture regimes was maximally reduced at midday. C i and the stomatal limitation fluctuated remarkably during photosynthesis midday depression processes, especially at the grain filling stage. Hence atmospheric drought at midday was one of the direct causes inducing stomata closure and the g s depression, but it was beneficial for maintaining stable intrinsic water use efficiency. Fluctuation in C i implicated that non-stomatal limitation also plays an important role during the period of photosynthesis midday depression. Consequently stomatal and/or non-stomatal limitation are the possible cause of the midday photosynthesis decline.
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    Flavonoid Responses in Wheat Grown at Elevated CO2: Green Versus Senescent Leaves (2000)
    Springer
    Photosynthetica 37 (2000), S. 615-619 
    Details
    ISSN: 1573-9058
    Keywords: carbon based secondary compounds (CBSC) ; isoorientin ; leaf age ; litter ; phenolics ; tricin ; Triticum aestivum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We compared flavonoids in green, mature, and senescing flag leaves of wheat grown under ambient (AC - 370 μmol mol-1) and elevated (EC - 550 μmol mol-1) concentrations of CO2 in a FACE (Free Air CO2 Enrichment) system. The concentrations of flag leaf flavonoids (e.g., isoorientin and tricin) decreased to one third in mature leaves, and the majoritary isoorientin almost disappeared in senescing leaves. Flavonoid concentrations increased in green well-developed flag leaves under EC (46 % isoorientin and 55 % tricin), whereas the differences disappeared in mature and senescing flag leaves. Predictions of changes in litter phenolic concentrations and their effects on decomposition rates under EC based on changes in green leaves need to be revised.
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    Short- versus Long-Term Effects of Elevated CO2 on Night-Time Respiration of Needles of Scots Pine (Pinus sylvestris L.) (2000)
    Springer
    Photosynthetica 38 (2000), S. 57-67 
    Details
    ISSN: 1573-9058
    Keywords: carbon ; C/N ; direct and indirect effects ; nitrogen ; soluble sugars ; starch ; specific leaf area
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Dark respiration rate in the night (R D) was measured in five-year-old Scots pine (Pinus sylvestris L.) trees grown for two years under ambient (AC) and elevated (AC + 400 µmol mol−1 = EC) CO2 concentrations in open top chambers. Two needle age classes (i.e., current-year and one-year-old) were measured at AC and EC in both AC- and EC-grown pines. Additionally different chemical characteristics were determined on the needles, such as nitrogen (N), carbon (C), starch, and soluble sugar concentrations as well as specific leaf area. The direct, short-term and indirect, long-term effects of EC on R D for the two needle age classes were examined. R D was expressed on a per needle area, needle mass, N, C, and C/N bases. Direct effects were only pronounced in the AC treatment where inhibition of R D was found at EC in both current- and one-year-old needles. Indirect effects were only significant in one-year-old needles where a decrease was found in the EC grown trees as compared with AC ones when R D was expressed per unit needle mass, C, or C/N. R D per unit needle area and needle N were not sensitive to long-term EC, in any needle age class. Long-term EC treatment also influenced the response of the two needle age classes. One-year-old needles from the EC treatment had significantly lower R D than current-year needles, but no such response was observed in the AC treatment. Our experiment re-emphasised the importance of expressing R D on different bases for a correct interpretation of the responses to EC. Moreover, we showed that different needle age classes can respond differently to a CO2 enrichment.
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    Nitrogen and Phosphorus Levels in Sediments from Tropical Catatumbo River (Venezuela) (2000)
    Springer
    Water, air & soil pollution 117 (2000), S. 27-37 
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    ISSN: 1573-2932
    Keywords: eutrophication ; nitrogen ; phosphorus ; river ; sediment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Nitrogen (N) and phosphorus (P) concentrations were determined in sediment samples along the bed of Catatumbo river in both Colombian and Venezuelan territories until the river outlet in Maracaibo lake. Total phosphorus was determined by digestion with HCl followed by analysis using the ascorbic acid method and total nitrogen was done using the standard microkjeldahl method plus nitrate-nitrite. Ammonium, orthophosphate and nitrate were determined using standard methods after extraction steps. The mean concentrations along the river bed were found in an interval of 0.035 and 1.492 mg g-1 dry sed. for nitrogen and 0.027 and 1.039 mg g-1 dry sed. for phosphorus at 95% confidence level. The mean molar ratio N/P in the river bed was 4.42 and 3.46 for river outlet zones in the lake, which indicates that nitrogen is the limiting nutrient. For comparison with previous results of lake sediments from sites near the river outlet it was concluded that Catatumbo river is a significant source of nutrients to the Maracaibo Lake system because sediment nutrients concentrations from Catatumbo river were higher than the ones in Maracaibo Lake. Statistic studies showed significant differences between countries, zones and similar behaviour in the river bed as related to the affluent rivers.
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    Analysis of Nitrogen Dynamics in the Lye Brook Wilderness Area, Vermont, USA (2000)
    Springer
    Water, air & soil pollution 122 (2000), S. 63-75 
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    ISSN: 1573-2932
    Keywords: nitrification ; nitrogen ; nitrogen mineralization ; soil water ; stream chemistry ; wilderness area
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Nitrogen (N) deposition and its impact on terrestrial and aquatic ecosystems is a concern facing federal land managers at the Lye Brook Wilderness in Vermont and other protected aras throughout the northeastern United States. In this study, we compared N production in soils with N concentrations and outputs in leachates to determine how forest cover types differ in regulating N losses. Also, precipitation inputs and modeled estimates of streamwater outputs were used to calculate a watershed N budget. Most ammonium and nitrate were produced in organic soils with deciduous cover. Softwood stands had low net nitrification rates and minimal N leaching. A comparison of watershed inputs and outputs showed a net gain in total dissolved N (5.5 kg ha-1 yr-1) due to an accumulation of dissolved inorganic N. The Lye Brook Wilderness ecosystem has N budgets similar to other forested ecosystems in the region, and appears to be assimilating the accumulating N. However seasonal losses of nitrate observed in mineral soils and streamwater may be early warnings of the initial stages of N saturation.
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    Treatment of Septic Effluent for Fecal Coliform and Nitrogen in Coarse-textured Soils: Use of Soil-only and Sand Filter Systems (2000)
    Springer
    Water, air & soil pollution 124 (2000), S. 205-215 
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    ISSN: 1573-2932
    Keywords: on-site treatment ; fecal coliform bacteria ; nitrate leaching ; nitrogen ; on-site treatment ; septic effluent
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Groundwater effluent sample collectors(zero-tension lysimeters) were installed directlybelow the drainfields of three residential onsitetreatment systems in the Clover/Chambers Creek aquiferregion of Pierce County near Tacoma, WA. The use of asplit effluent delivery system from the septic tank,where half the effluent was delivered under pressureto a normal native soil-only filter system and halfwas delivered to a sand filter system, allowed thedirect comparison of the two commonly-utilized septicsystems for treatment levels. Septic tank effluent(from the septic tank) and percolating water (between0.3 and 0.9 m beneath the effluent distributionlines) was collected between May 1991 and April 1994on 30 occasions. Samples were analyzed for fecalcoliform bacteria, nitrate, nitrite, ammonium andtotal reduced (Kjeldahl) nitrogen. Results of thisstudy indicate that the use of sand filters greatlyincreased removal of fecal coliform bacteria and totalnitrogen. Soil-only filter systems had an average of91% removal of fecal coliforms and 47%of total N; whereas sand filter systems had an averageof 99.8% removal of fecal coliforms and 80% of total N.
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    The Replacement Value of Wetlands in Sweden (2000)
    Springer
    Environmental and resource economics 16 (2000), S. 347-362 
    Details
    ISSN: 1573-1502
    Keywords: cost-effectiveness ; nitrogen ; nonpoint ; policy ; value ; wetlands
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Economics
    Notes: Abstract Wetlands, in Sweden and elsewhere, have been suggestedas effective and low-cost sinks for agriculturalpollution. This paper estimates the value of usingwetlands for abatement of agricultural nitrogen loadon the Baltic Sea. A replacement value of wetlands isestimated for Sweden. The replacement value is definedand estimated as the difference between twocost-effective reductions of agricultural nitrogenpollution: one that uses wetlands for nitrogenabatement, and one that does not. It is shown that theuse of wetlands as nitrogen sinks can reduce the totalabatement costs of nitrogen emissions by 30% forSwedish agricultural sources of nitrogen pollution.
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    URL: http://dx.doi.org/10.1023/A:1008316619355
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    A weighing method to identify the microbial growth phases in solid-state fermentation tests (2000)
    Springer
    World journal of microbiology and biotechnology 16 (2000), S. 601-605 
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    ISSN: 1573-0972
    Keywords: Growth phases identification ; kinetics ; Rhizopus oryzae ; solid-state fermentation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A general equation correlating the variation rate of the fermenting medium weight (dry matter) and the cell biomass growth rate in solid-state fermentation tests is proposed with the main purpose of identifying the microbial growth phases.
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    URL: http://dx.doi.org/10.1023/A:1008970720794
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    Electrochemical and Adsorption Studies on the Formation of Poly-8-Hydroxyquinaldine Thin Films at Glassy Carbon/Electrolyte Interface (2000)
    Springer
    Interface science 8 (2000), S. 111-121 
    Details
    ISSN: 1573-2746
    Keywords: 8-hydroxyquinaldine ; electropolymerization ; adsorption ; glassy carbon ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The kinetics and thermodynamics of the electropolymerization of the chelating agent 8-hydroxyquinaldine on GCE's (Glassy Carbon Electrodes') surface from aqueous phosphate buffers are reported. Thermodynamic functions related to the adsorption of the monomer on the GCE's surfaces were determinated. No contribution from GCE surface's functional group to the electropolymerization reactions was reported. The effects of monomer concentration, pH, and temperature on the electrochemical growth of poly 8-hydroxyquinaldine were investigated. The results suggest that the propagation of the electropolymerization process takes place via a free radical chain reactions. Furthermore, the results indicate that the electrochemical growth of the polymeric films is dictated by pre-polymerization adsorption on the electrode surface.
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    URL: http://dx.doi.org/10.1023/A:1008799724511
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    Temperature Dependent Seed Transmission of Stagonospora nodorum in Wheat (2000)
    Springer
    European journal of plant pathology 106 (2000), S. 837-842 
    Details
    ISSN: 1573-8469
    Keywords: Triticum aestivum ; Septoria nodorum ; Phaeosphaeria nodorum ; epidemiology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The transmission of Stagonospora nodorum from four naturally infected winter wheat seedlots was quantified in controlled environment germination chambers at 9, 13, 17, 21, and 25 °C. Seedlings were harvested when the second leaf began to emerge. Coleoptiles and first seedling leaves were examined for the presence of lesions caused by S. nodorum. First leaves were incubated on Bannon's medium for 2 weeks, after which they were examined for pycnidia of S. nodorum. Transmission to the coleoptile occurred at all temperatures, but decreased from 100% to 72% as temperature increased from 9 to 25 °C. Transmission to the first leaf was less, dropping from 37% to 2% as temperature increased from 9 to 25 °C. At least 44% of infected first leaves were symptomless at all temperatures, with 96% of infected leaves showing no symptoms at 25 °C. Transmission to seedling leaves occurred over a broad temperature range. Under the high densities at which wheat is sown, a significant number of infected seedlings per unit area may originate from relatively low initial seed infection levels and transmission efficiencies.
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    URL: http://dx.doi.org/10.1023/A:1008723823196
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    Kinetic investigation of the alkylation of salts of 2,5-dimercapto-1,3,4-thiadiazole (2000)
    Springer
    Chemistry of heterocyclic compounds 36 (2000), S. 857-861 
    Details
    ISSN: 1573-8353
    Keywords: salts of 2,5-dimercapto-1,3,4-thiadiazole ; alkylation ; kinetics ; electronic absorption spectra
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A kinetic investigation has been carried out, using electronic absorption spectra, of the alkylation with benzyl chloride of the dihydrazine, monohydrazine, and the disodium salts of 2,5-dimercapto-1,3,4-thiadiazole, and also of the hydrazine and sodium salts of 5-benzylthio-2-mercapto-1,3,4-thiadiazole. The rates orders and constants were established for the benzylation reaction and it was noted that the reaction rate depends on the cation of these salts and the degree of substitution of the 2,5-dimercapto-1,3,4-thiadiazole.
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    URL: http://dx.doi.org/10.1007/BF02256923
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    Photosynthetic Traits in Wheat Grown under Decreased and Increased CO2 Concentration, and after Transfer to Natural CO2 concentration (2000)
    Springer
    Biologia plantarum 43 (2000), S. 227-237 
    Details
    ISSN: 1573-8264
    Keywords: carboxylation efficiecy ; carotenoids ; chlorophyll ; growth analysis ; net photosynthetic rate ; photochemical efficiency ; ribulose 1,5-bisphosphate carboxylase/oxygenase ; stomatal conductance ; Triticum aestivum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Wheat plants were grown from sowing to day 18 in 26-dm3 chambers at three different CO2 concentrations: 150 (-CO2), 350 (C, control), 800 (+CO2) μmol mol-1. Afterwards, plants of the three variants were grown at the same natural CO2 concentration. Plant characteristics were measured just before the transfer (0 days after CO2 treatment, DAT), and at 5 – 8 DAT on the 1st leaf, and at 12 – 22 DAT on the 4th leaf. Decreased or increased CO2 concentrations caused acclimations which persisted after transplantation to natural CO2 concentration. At 5 – 8 DAT, stomatal density, stomatal conductance (gs), CO2 saturated net photosynthetic rate (PNsat0), radiation saturated net photosynthetic rate (PNsat1), and carboxylation efficiency (τ) were higher in -CO2 plants and lower in +CO2 plants than in C plants. As compared with C plants, the photochemical efficiency (α) was lower in -CO2 and higher in -CO2 plants, however, chlorophyll (Chl) a, Chl b, Chl a–b and carotenoid contents were lower in both -CO2 and +CO2 plants. On the 4th leaf, which emerged on plant after finishing CO2 treatments, at 12 – 22 DAT, no differences in stomatal density and g, between treatments were observed. In -CO2 plants, pigment content and PNsat0 were higher, α was lower, and PNsat1 and τ were not different from C plants. In contrast, in +CO2 plants, pigment content, PNsat1 and τ were lower, and PNsat0 and α were unchanged. Leaf area, dry mass, and tiller development increased in +CO2 plants and decreased in -CO2 plants. In the interval between 8 and 22 DAT, lower net assimilation rate in +CO2 than in -CO2 plants was observed.
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    URL: http://dx.doi.org/10.1023/A:1002752210237
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    Long-Distance Transport of Alkali Metals in Maturing Wheat (2000)
    Springer
    Biologia plantarum 43 (2000), S. 523-528 
    Details
    ISSN: 1573-8264
    Keywords: accumulation ; grains ; lithium ; mobility ; phloem ; potassium ; rubidium ; sodium ; strontium ; Triticum aestivum ; xylem
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The alkali metals cesium, rubidium, lithium and sodium were introduced together with strontium via flaps into leaf laminas or into the stem of maturing, intact winter wheat (Triticum aestivum L. cv. Arina) grown in a field. Long-distance transport of these elements and the influence of the application date and of different application positions were investigated. The phloem-immobile Sr served as a marker for the distribution of the xylem sap in the plants. Dry matter accumulation in the grains and the transpiration per shoot were not markedly affected by the treatments as compared to control plants. The phloem mobility was rather high for Cs and Rb. Li was almost immobile in the phloem (similarly to Sr). An application into the cut stem xylem below the second leaf node contributed more to the contents in the grains than an application into the flag leaf. An earlier feeding date led to a higher accumulation in the grains. The marked losses of the elements applied during maturation (most pronounced for Li) can be explained by leakage in the rain.
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    URL: http://dx.doi.org/10.1023/A:1002806522138
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    Respiration Rate and Chemical Composition of Karwinskia Roots as Affected by Temperature (2000)
    Springer
    Biologia plantarum 43 (2000), S. 611-613 
    Details
    ISSN: 1573-8264
    Keywords: carbon ; hydrogen ; nitrogen ; reducing sugars ; starch ; summer and winter temperature regime
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Two-year-old plants of Karwinskia humboldtiana Zucc. and Karwinskia parvifolia Rose grown from the seeds in greenhouse were transferred to the growth cabinet and cultivated for two months under different temperature regimes (35/20 °C - the summer temperature regime, SR, and 20/5 °C - the winter temperature regime, WR). These temperatures were similar to the temperature conditions in the natural areas of the species studied (Nuevo León, Mexico). The root respiration rate was higher in the plants cultivated under SR than in those under WR. Roots of K. parvifolia res faster in both temperature regimes than roots of K. humboldtiana. Starch content in roots was higher in the plan cultivated under SR, however, concentrations of the other investigated organic and inorganic compounds were higher in the plants cultivated under WR. In K. humboldtiana roots, higher concentration of reducing sugars, carbon and hydrogen were found than in K. parvifolia.
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    URL: http://dx.doi.org/10.1023/A:1002808201124
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    NaCl Effects on Root Plasma Membrane ATPase of Salt Tolerant Wheat (2000)
    Springer
    Biologia plantarum 43 (2000), S. 61-66 
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    ISSN: 1573-8264
    Keywords: lipids ; polypeptide pattern ; salt stress ; Triticum aestivum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Wheat seedlings of a salt tolerant cultivar were grown hydroponically in presence and absence of 100 mM NaCl. Roots were harvested, and the plasma membrane (PM) fraction was purified. PM ATPase required a divalent cations for activity (Mg 〉 Mn 〉 Ca 〉 Co 〉 Zn 〉 Ni 〉 Cu), and it was further stimulated by monovalent cations (K 〉 Rb 〉 NH4 〉 Li 〉 choline 〉 Cs). The pH optima were 6.0 and 5.6 in absence and presence of 25 mM KCl, respectively. The enzyme was sensitive to vanadate and DCCD but insensitive to azide, oligomycine and nitrate. The enzyme displayed a high preference for ATP but was also able to hydrolyze other nucleotide tri- and diphosphates. The enzyme activity showed a simple Michaelis-Menten kinetics for the substrate Mg2+-ATP in both control and salt exposed roots. The polypeptide patterns of control and salt stressed PM fractions, detected by SDS-PAGE, were very similar. NaCl substantially reduced the PM ATPase specific activity, whereas it had little effect on the apparent Km for Mg2+-ATP. Since the root PM ATPase of salt sensitive and resistant genotypes responded similarly to salinity stress, it seems unlikely that the mechanism of salt tolerance in wheat is primarily based on differences in PM ATPase characteristics.
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    Transfer of Cesium from the Xylem to the Phloem in the Stem of Wheat (2000)
    Springer
    Biologia plantarum 43 (2000), S. 309-311 
    Details
    ISSN: 1573-8264
    Keywords: grains ; maturation ; radioisotopes ; transport ; Triticum aestivum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Steam-girdling experiments with detached wheat shoots showed that cesium was eliminated from the xylem sap and loaded into the phloem during acropetal transport. This transfer is important for the accumulation of cesium (especially also of the radiopollutants 134Cs and 137Cs) in maturing wheat grains.
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    URL: http://dx.doi.org/10.1023/A:1002737201577
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    The Role of Peroxidase and Polyphenol Oxidase Isozymes in Wheat Resistance to Alternaria triticina (2000)
    Springer
    Biologia plantarum 43 (2000), S. 559-562 
    Details
    ISSN: 1573-8264
    Keywords: phenolics ; susceptibility ; Triticum aestivum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Polyphenol oxidase activity was higher in resistant wheat cultivar ACC-8226 than in susceptible cultivar MP-845 in control sets and after inoculation of Alternaria triticina. However, similar polyphenol oxidase isozyme pattern was found in control and inoculated sets of both the cultivars, but the band intensity was higher after inoculation. Three and four peroxidase isozymes were found in ACC-8226 and MP-845, respectively. An extra peroxidase isozyme band was observed in both the cultivars after inoculation. The results suggest an active role of peroxidase and polyphenol oxidase in defence mechanism of wheat plants.
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    URL: http://dx.doi.org/10.1023/A:1002821715719
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    Increased Antioxidant Activity under Elevated Temperatures: A Mechanism of Heat Stress Tolerance in Wheat Genotypes (2000)
    Springer
    Biologia plantarum 43 (2000), S. 245-251 
    Details
    ISSN: 1573-8264
    Keywords: ascorbic acid ; ascorbate peroxidase ; active oxygen species ; catalase ; hydroger ; peroxide ; oxidative stress ; superoxide dismutase ; temperature stress ; Triticum aestivum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract An experiment was conducted with three wheat (Triticum aestivum L.) genotypes C 306, HD 2285 and HD 2329 (differently susceptible to water and temperature stress) to study the extent of oxidative injury and activities of antioxidant enzymes in relation to heat stress induced by manipulating dates of sowing. Increase in temperature by late sowing significantly decreased leaf relative water content (RWC), ascorbic acid content, and increased H2O2 content and lipid peroxidation in all the genotypes at 8 and 23 d after anthesis. Temperature tolerant genotypes C 306, closely followed by HD 2285 were superior to HD 2329 in maintaining high RWC, ascorbic acid content, and lower H2O2 content and lipid peroxidation (malondialdehyde content) under high temperature (late sowing) at the two stages. Activities of superoxide dismutase and catalase were highest in HD 2285 followed by C 306 and minimum in HD 2329 while ascorbate peroxidase activity was highest in C 306.
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    Induction of Oxidative Stress and Antioxidant Activity by Hydrogen Peroxide Treatment in Tolerant and Susceptible Wheat Genotypes (2000)
    Springer
    Biologia plantarum 43 (2000), S. 381-386 
    Details
    ISSN: 1573-8264
    Keywords: active oxygen species ; catalase ; chloroplast ; glutathione reductase ; lipid peroxidation ; nitrate reductase ; proline ; superoxide dismutase ; Triticum aestivum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We induced an oxidative stress by means of exogenous hydrogen peroxide in two wheat genotypes, C 306 (tolerant to water stress) and Hira (susceptible to water stress), and investigated oxidative injury and changes in antioxidant enzymes activity. H2O2 treatment caused chlorophyll degradation, lipid peroxidation, decreased membrane stability and activity of nitrate reductase. Hydrogen peroxide increased the activity of antioxidant enzymes, glutathione reductase and catalase. These effects increased with increasing H2O2 concentrations. However, no change was observed in the activity of superoxide dismutase and proline accumulation.
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    URL: http://dx.doi.org/10.1023/A:1026730008917
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    The Role of Plant Size and Nutrient Concentrations in Associations between Medicago, and Rhizobium and/or Glomus (2000)
    Springer
    Biologia plantarum 43 (2000), S. 221-226 
    Details
    ISSN: 1573-8264
    Keywords: alfalfa ; arbuscular mycorrhizal fungi ; nitrogen ; nitrogen-fixing bacteria ; phosphorus ; plant growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The aim of this research was to carry out a critical study of the method of obtaining size equivalence between non-symbiotic alfalfa and alfalfa associated with Glomus and/or Rhizobium by applying fixed addition rates of nutrients to the non-symbiotic controls. The experimental design included three nutrient response curves in which the levels of added phosphorus and/or nitrogen were constant during the whole plant growth process: 1) a phosphorus response curve, in order to compare the growth of double symbiotic plants with that of only-Rhizobium inoculated ones; 2) a nitrogen response curve, that consisted of a comparison between the growth of double symbiotic alfalfa and four treatments associated only with Glomus; 3) a phosphorus and nitrogen response curve, to compare the growth of non-inoculated alfalfa with that of double symbiotic plants. Although similar size was achieved among some treatments at harvest, shoot growth over time and nutrient concentrations in tissues differed, indicating that growth equivalence did not mean functional equivalence. A second experimental design was performed taking into account the establishment of microsymbionts for determining the adequate moment to add supplemental phosphorus and/or nitrogen. It included four treatments: a) double symbiotic plants (MR); b) plants inoculated with Rhizobium only (R); c) plants inoculated with Glomus only (M), and d) non-inoculated plants (N). Great similarity in terms of plant growth and nutrient contents in tissues were obtained. Moreover, symbiotic plants were able to produce similar dry matter than non-symbiotic ones under P and N limitations.
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    URL: http://dx.doi.org/10.1023/A:1002700226167
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    Inhibition of Wheat Nitrate Reductase Activity by Zinc (2000)
    Springer
    Biologia plantarum 43 (2000), S. 257-262 
    Details
    ISSN: 1573-8264
    Keywords: nitrate assimilation ; Triticum aestivum ; Zn toxicity ; Cu toxicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effect of Zn2- on nitrate reductase (NR, EC 1.6.6.1) activity was studied in botá wheat (Triticum aestivum cv. Oasis) leaves and in the NR enzyme partially purified from wheat leaves. Leaf segments were floated on 0 to 5 mM ZnSO4 solutions (pH 6.0) for 24 h under continuous light. Zn2- at 250 μM decreased NR activity and increased membrane permeability. However, parameters of cellular oxidative damage were scarcely affected by Zn2- treatments. Accordingly, the decrease of NR activity induced by Zn2- was not prevented by benzoate (a scavenger of oxygen radicals). The effect of Zn2- was dependent on leaf age: it decreased NR activity in mature but not in young leaves. Zn2 inhibited the partially purified NR. This inhibition was not reversed by either co- or post-incubation with cysteine, and the amount of -SH groups of the purified NR was not affected by Zn2+ indicating that Zn2- inhibition does not involve key -SH groups of the enzyme. However, o-phenantroline both prevented and reversed Zn2+-induced NR inhibition. We concluded that the effect of Zn2+ on NR activity in vivo is not associated with an increase in active oxygen generation and involves a direct and reversible inhibition of the enzyme.
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    Feeding damage by Diuraphis noxia results in a nutritionally enhanced phloem diet (1999)
    Springer
    Entomologia experimentalis et applicata 91 (1999), S. 403-412 
    Details
    ISSN: 1570-7458
    Keywords: aphid ; Diuraphis noxia ; Triticum aestivum ; endosymbiont ; insect-plant interactions ; phloem ; amino acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The feeding behavior of Diuraphis noxia Mordvilko (Homoptera: Aphididae) on susceptible hosts causes both ultrastructural and tissue level damage which may affect phloem composition. Genetic evidence suggests that endosymbiotic bacteria in most aphids overproduce limiting amino acids to benefit hosts but that D. noxia depends less on endosymbionts for these nutrients, possibly due to an enriched diet. To determine whether D. noxia feeding damage results in higher concentrations of essential amino acids, stylet exudates were analyzed from wheat (Triticum aestivum) damaged to different degrees. Comparison of samples from undamaged and damaged susceptible wheat revealed changes in amino acid composition and an increase in levels of essential amino acids, indicating a nutritionally enhanced ingesta. The changes in stylet exudates paralleled changes in leaf exudates, indicating that the effects are systemic. Feeding damage is not observed on a resistant wheat host, var. Halt, and leaf exudates from infested Halt did not show changes in amino acid composition. Mean relative growth of nymphs was significantly lower on Halt than on susceptible Arapahoe, indicating that Halt is a less suitable host. Both varieties show similar amino acid levels in non-infested samples, suggesting that D. noxia infestation does not enhance the phloem environment in Halt. This study provides evidence that aphid feeding can generate a nutritionally enhanced phloem diet.
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    Compensatory responses of Samea multiplicalis larvae when fed leaves of different fertilization levels of the aquatic weed Pistia stratiotes (1999)
    Springer
    Entomologia experimentalis et applicata 92 (1999), S. 205-216 
    Details
    ISSN: 1570-7458
    Keywords: Samea multiplicalis ; Spodoptera pectinicornis ; Pistia stratiotes ; waterlettuce ; nitrogen utilization efficiency ; compensatory feeding ; nitrogen ; biological control of weeds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Compensatory responses of caterpillars fed low quality food include increased consumption and utilization of essential nutrients. Information about an insect's responses to nutritional challenges from their host plants could benefit weed biological control efforts in the selection and establishment of new agents. The target weed, Pistia stratiotes L. (Araceae) is a floating aquatic plant that has relatively low nitrogen levels which are further diluted with high water content. Efforts to establish the insect Spodoptera pectinicornis (Hampson) (Lepidoptera: Noctuidae) for biological control of P. stratiotes could benefit by examining the nutritional responses of a similar widely established lepidopteran species, Samea multiplicalis (Guenèe) (Lepidoptera: Pyralidae). Larvae of this species were fed leaves of P. stratiotes plants that had been fertilized (NPK) at high and low rates. The leaves of the fertilized plants had a 4.3-fold increase in nitrogen (dry weight) and a 1.6-fold increase in water content. The results suggest that no compensatory increases occurred in larvae fed leaves from the low fertilized plants as no changes were found in fresh mass consumption or nitrogen utilization efficiency. Consequently, development time from second-third instars to pupation was delayed about 3 days compared with larvae fed the high nitrogen leaves. Furthermore, consumption of nitrogen was only 30% and its accumulation into larval tissues was only 60% compared with the larvae fed the high fertilized leaves. The resulting larvae had both a final biomass and a growth rate that were reduced by 40%. Regardless of plant fertilizer level, the larvae fed at a rate 5–10 times greater than that of similar lepidopteran species consuming either low or high quality diets, suggesting that the S. multiplicalis larvae may be functioning at their biological limit for ingesting food.
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    Plant quality or quantity? Host exploitation strategies in three Chrysomelidae species associated with Asteraceae host plants (1999)
    Springer
    Entomologia experimentalis et applicata 92 (1999), S. 165-177 
    Details
    ISSN: 1570-7458
    Keywords: Chrysomelidae ; herbivory ; Asteraceae ; life history ; nitrogen ; plant quality ; season
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Phytophagous insects which feed on the leaves of herbaceous host plants have to adapt their life histories to the fact that protein nitrogen is usually highest in growing tissues in spring. We monitored field populations of larvae and adults of three chrysomelid species (Galeruca tanaceti (L.) (main host Achillea millefolium (L.) Yarrow), Cassida rubiginosa (Mueller) (main host Cirsium arvense (L.) Scop.) and Oreina luctuosa (Suffrian) (host Centaurea scabiosa (L.)) together with the amount of protein nitrogen of their food resources and host plant biomass. As expected, the development of host quality, measured as concentration of protein nitrogen, and host plant biomass showed inverse trends during the season. The euryphagous G. tanaceti attacks Achillea early and profits from high nitrogen concentrations in the leaves. Occasional overexploitations of local populations of Achillea are compensated by the capacity to move to other host species. In C. rubiginosa, a species with a host range restricted to the Cardueae, the main larval feeding activity is postponed to a period when the nitrogen content of the host leaves had dropped to 50% of its initial value, but when host plant biomass had increased by 30%. In the monophagous O. luctuosa the larval development is synchronized with a still later phase of host phenology, at which the nitrogen content is below 50% but plant biomass has reached its maximum. There seem to be selection factors, which oppose the use of high quality food in spring and which force the latter two species to postpone their larval development to a later time in the year. This could be caused by numerous factors like, for example, mean daytime temperature. Later in the season the larvae have to cope with the low quality of their host plants. They have, however, the advantage of large quantities of food available. A laboratory study with adults and mature larvae of O. luctuosa shows that this species can overcome low levels of protein nitrogen either by selecting younger leaves with higher nitrogen concentrations or by increasing the daily food consumption rate (RCR) on leaves with a low level of nitrogen and by a prolongation of the feeding period. In this way the larvae compensate the effect of lower daily growth rates (RGR) and a lower food conversion index (ECI) on poor food quality: Regardless of the level of protein nitrogen there was no statistically significant difference in total gain of weight during the third-instar feeding period and in the weight at the end of the third larval stage. The three investigated chrysomelids show that there exists a broad spectrum of adaptations to overcome the dilemma of variable food quality.
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    Salivation into sieve elements in relation to plant chemistry: the case of the aphid Sitobion fragariae and the wheat, Triticum aestivum (1999)
    Springer
    Entomologia experimentalis et applicata 91 (1999), S. 111-114 
    Details
    ISSN: 1570-7458
    Keywords: sieve element ; salivation ; aphid ; plant resistance ; wheat ; Sitobion fragariae ; Triticum aestivum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Extended sieve element salivation (E1 waveform in the electrical penetration graph) is a characteristic activity during early sieve element punctures, particularly in resistant plants. In order to explore a chemically-mediated mechanism of resistance associated with sieve element salivation, we compared the pattern of feeding behaviour of the aphid, Sitobion fragariae (Walker), on two cultivars of the wheat Triticum aestivum L., with different concentrations of hydroxamic acids (Hx). During 24 h of electronic monitoring, aphids dedicated over 50% of the total time to phloem ingestion from the sieve elements. Total time allocated to E1 in the experiment, time to first E1 within the experiment, time allocated to E1 before a sustained phloem ingestion (E2) and the contribution of sieve element salivation to the phloem phase (E1/[E1+E2]) were significantly higher in the high-Hx cultivar. The increased salivation in plants with higher contents of Hx suggests the existence, at least in this system, of a chemically-mediated sieve element constraint.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003628703035
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  • 190
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    Kinetics and mechanism of MnO2 dissolution in H2SO4 in the presence of pyrite (1999)
    Springer
    Journal of applied electrochemistry 29 (1999), S. 191-200 
    Details
    ISSN: 1572-8838
    Keywords: cyclic redox reaction ; dissolution ; kinetics ; manganese dioxide ; mechanism ; pyrite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract This paper describes a study of the kinetics and mechanism of MnO2 dissolution in H2SO4 in the presence of pyrite through leaching and electrochemical parameters. Manganese(iv) was found to dissolve mainly through reduction by the ferrous ion generated during oxidation of pyrite by the ferric ion. The oxidation which is slower and rate controlling may proceed through two different reactions, one producing S0 and the other SO42−. Manganese dissolution runs at the same rate as that of pyrite oxidation by maintaining ferrous ion concentration at a much lower level than that of ferric. Kinetic equations based on corrosion coupling principles are developed to explain the observed leaching behaviour.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003490810114
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  • 191
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    Factors affecting bioleaching kinetics of sulfide ores using acidophilic micro-organisms (1999)
    Springer
    BioMetals 12 (1999), S. 1-10 
    Details
    ISSN: 1572-8773
    Keywords: acidophilic ; strain ; oxidation ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Recovery of metal values from sulfide ores by use of acidophilic microorganisms is gaining importance. A number of commercial/pilot plants are setup to find out the techno-economic feasibility of the overall process. The main drawback in the process is the slow kinetics of dissolution of metal values from the sulfide ores. To make the technology e attractive the kinetics should be improved considerably. There are various factors which determine the overall kinetics such as bacterial activity and concentration, iron and sulfur oxidation, oxygen consumption, reactor design and nature of ore. A brief review has been made dealing with the above parameters
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009228210654
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  • 192
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    Degradation of Cellulosic Materials Under the Alkaline Conditions of a Cementitious Repository for Low- and Intermediate-Level Radioactive Waste. II. Degradation Kinetics (1999)
    Springer
    Journal of polymers and the environment 7 (1999), S. 41-51 
    Details
    ISSN: 1572-8900
    Keywords: Cellulose ; alkaline degradation ; peeling off ; degree of polymerization ; kinetics ; (gluco)isosaccharinic acid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The degradation of cellulosic materials, differing mainly in the degree of polymerization and the number of reducing end groups, was studied under the alkaline conditions similar to those existing in a cementitious repository for low- and intermediate-level radioactive waste (pH 13.3, T = 25°C). The kinetics of alkaline degradation (peeling-off reaction) were studied and the data analyzed by the model of Haas et al. [13]. The observed kinetic parameters for the propagation reaction and overall stopping reaction were compared with literature data. Although measured under different experimental conditions, literature data and data from this study show a consistent picture. Differences in the extent of degradation observed for the different cellulosic materials could be satisfactorily explained by differences in reducing end group content and, consequently, by differences in the degrees of polymerization. Besides the number of reducing end groups, the degree of amorphousness also plays an important role. The main degradation products formed under the experimental conditions used are α- and β-(gluco)isosaccharinic acid. This is in agreement with many other studies on alkaline degradation of cellulose. The two isomers are formed in roughly equal amounts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021894102937
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  • 193
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    Sorption Equilibria and Kinetics of Hydrocarbons onto Activated Carbon Samples Having Different Micropore Size Distributions (1999)
    Springer
    Adsorption 5 (1999), S. 25-37 
    Details
    ISSN: 1572-8757
    Keywords: micropore size distribution ; activated carbon ; adsorption ; desorption ; equilibrium ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract This paper deals with the prediction of adsorption equilibrium and kinetics of hydrocarbons onto activated carbon samples having different micropore size distribution (MPSD). The microporous structure of activated carbon is characterised by the distribution of slit-shaped micropores, which is assumed to be the sole source of surface heterogeneity. The interaction between adsorbate molecule and pore walls is described by the Lennard-Jones potential theory. Different adsorbates have access to different pore size range of activated carbon due to the size exclusion, a phenomenon could have a significant influence on both multicomponent equilibria and kinetics. Activated carbons with three different MPSDs are studied with ethane and propane as the two model adsorbates. The Heterogeneous Macropore Surface Diffusion model (HMSD) is employed to simulate adsorption kinetics. The simulation results show that the MPSD is an important factor affecting both the multicomponent equilibria and kinetics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026481704926
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  • 194
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    FTIR spectroscopic evidence of formation of geminal dinitrogen species during the low-temperature N2 adsorption on NaY zeolites (1999)
    Springer
    Catalysis letters 58 (1999), S. 21-26 
    Details
    ISSN: 1572-879X
    Keywords: adsorption ; adsorption isotherms ; dinitrogen ; FTIR spectroscopy ; geminal species ; NaY ; nitrogen ; zeolites
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Adsorption of N2 on NaY zeolites at 85 K and equilibrium pressures higher than 1 kPa results in the formation of geminal dinitrogen complexes characterized by an IR band at 2333.5 cm−1 (2255.4 cm−1 after adsorption of 15N2). With decreasing equilibrium pressure the complexes tend to loose one N2 ligand, thus forming linear species characterized by an IR band at 2336.8 cm−1 (2258.7 cm−1 after adsorption of 15N2). All species disappear completely after evacuation. Co-adsorption of N2 and CO revealed that the dinitrogen complexes are formed on Na+ cations. The changes in the concentrations of the linear and geminal N2 species with the changes in the equilibrium pressure are excellently described by equations of adsorption isotherms proposed earlier for mono- and di-carbonyls.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019040825491
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  • 195
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    Furfural hydrogenation over carbon‐supported copper (1999)
    Springer
    Catalysis letters 60 (1999), S. 51-57 
    Details
    ISSN: 1572-879X
    Keywords: furfural hydrogenation ; Cu/carbon catalysts ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Furfural hydrogenation over copper dispersed on three forms of carbon – activated carbon, diamond and graphitized fibers – were studied. Only hydrogenation of the C=O bond to form either furfuryl alcohol or 2‐methyl furan occurred at temperatures from 473 to 573 K. Reduction at 573 K gave the most active catalysts, all three catalysts had activation energies of 16 kcal/mol, and turnover frequencies were 0.018–0.032 s-1 based on the number of Cu0 + Cu+ sites, which were counted by N2O adsorption at 363 K and CO adsorption at 300 K, respectively. The Cu/activated carbon catalyst showed no deactivation during 10 h on stream, in contrast to the other two catalysts. A simple Langmuir–Hinshelwood model invoking two types of sites was able to fit all kinetic data quite satisfactorily, thus it was consistent with the presence of both Cu0 and Cu+ sites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019090520407
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  • 196
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    Study of the ammonia decomposition over iron catalysts (1999)
    Springer
    Catalysis letters 60 (1999), S. 167-171 
    Details
    ISSN: 1572-879X
    Keywords: ammonia decomposition ; iron catalyst ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The decomposition of ammonia is a reaction associated with the process of the nitriding of metals. The kinetics of the ammonia decomposition on iron catalysts has been studied using a differential reactor with internal mixing. The balance between the inlet and outlet ammonia quantity has been used to determine the degree of conversion. The rate of ammonia decomposition could be described by the following expression: r = k0 exp (Ea/RT)pNH3. The activation energy of the ammonia decomposition process has been found for samples with potassium as E a= 96 kJ/mol, for samples without potassium as E a= 87 kJ/mol.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019007024041
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  • 197
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    Pure and Binary Gas Adsorption Equilibria and Kinetics of Methane and Nitrogen on 4A Zeolite by Isotope Exchange Technique (1999)
    Springer
    Adsorption 5 (1999), S. 145-158 
    Details
    ISSN: 1572-8757
    Keywords: kinetics ; isotope-exchange ; nitrogen ; adsorption ; methane ; zeolite ; equilibria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The Isotope Exchange Technique (IET) was used to simultaneously measure pure and binary gas adsorption equilibria and kinetics (self-diffusivities) of CH4 and N2 on pelletized 4A zeolite. The experiment was carried out isothermally without disturbing the adsorbed phase. CH4 was selectively adsorbed over N2 by the zeolite because of its higher polarizability. The multi-site Langmuir model described the pure gas and binary adsorption equilibria fairly well at three different temperatures. The selectivity of adsorption of CH4 over N2 increased with increasing pressure at constant gas phase composition and temperature. This curious behavior was caused by the differences in the sizes of the adsorbates. The diffusion of CH4 and N2 into the zeolite was an activated process and the Fickian diffusion model described the uptake of both pure gases and their mixtures. The self-diffusivity of N2 was an order of magnitude larger than that for CH4. The pure gas self-diffusivities for both components were constants over a large range of surface coverages (0 〈 θ 〈 0.5). The self-diffusivities of CH4 and N2 from their binary mixtures were not affected by the presence of each other, compared to their pure gas self-diffusivities at identical surface coverages.
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    URL: http://dx.doi.org/10.1023/A:1008917308002
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  • 198
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    The detailed kinetics of the desorption of hydrogen from polycrystalline copper catalysts (1999)
    Springer
    Catalysis letters 59 (1999), S. 143-149 
    Details
    ISSN: 1572-879X
    Keywords: hydrogen ; desorption ; copper ; activation energy ; kinetics ; order of desorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics of desorption of hydrogen from the copper component of an alumina-supported polycrystalline copper catalyst has been studied in detail by temperature-programmed desorption (TPD). Line-shape analysis of the hydrogen TPD spectra shows: (i) that the desorption is second order, (ii) that the desorption activation energy is in the range 64–68 kJ mol−1 in the coverage range 7–44% of a monolayer, and (iii) that the desorption pre-exponential term has a value ∼10−5 cm2 s−1 atom−1 consistent with the desorption being second order, involving mobile adsorbates and a mobile desorption transition state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019080823616
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  • 199
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    Root respiratory quotient and nitrate uptake in hydroponically grown non-mycorrhizal and mycorrhizal wheat (1999)
    Springer
    Mycorrhiza 9 (1999), S. 57-60 
    Details
    ISSN: 1432-1890
    Keywords: Key words Glomus mosseae ; Hydroponics ; Nitrate uptake ; Root respiration ; Triticum aestivum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Oxygen and CO2 fluxes were measured in hydroponically grown mycorrhizal and non-mycorrhizal Triticum aestivum L. cv. Hano roots. The NO3 – uptake of the plants was used to estimate the amount of root respiration attributable to ion uptake. Plants were grown at 4 mM N and 10 μM P, where a total and viable mycorrhizal root colonisation of 48% and 18%, respectively, by Glomus mosseae (Nicol. and Gerd.) Gerd. and Trappe (BEG 107) was observed. The O2 consumption and NO3 – uptake rates were similar and the CO2 release was higher in mycorrhizal than in non-mycorrhizal wheat. This resulted in a significantly higher respiratory quotient (RQ, mol CO2 mol–1 O2) in mycorrhizal (1.27±0.13) than in non-mycorrhizal (0.79±0.05) wheat. As the biomass and N and P concentrations in mycorrhizal and non-mycorrhizal wheat were the same, the higher RQ resulted from the mycorrhizal colonisation and not differences in nutrition per se.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s005720050263
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  • 200
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    Inoculation with phosphate-solubilizing microorganisms and a vesicular-arbuscular mycorrhizal fungus improves dry matter yield and nutrient uptake by wheat grown in a sandy soil (1999)
    Springer
    Biology and fertility of soils 28 (1999), S. 139-144 
    Details
    ISSN: 1432-0789
    Keywords: Key words Phosphate-solubilizing microorganisms ; Mussoorie rock phosphate ; Vesicular-arbuscular mycorrhizae ; Triticum aestivum ; Nutrient-deficient soils
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  The effect of inoculating wheat (Triticum aestivum L.) with the PO4 3–-solubilizing microorganisms (PSM) Bacillus circulans and Cladosporium herbarum and the vesicular-arbuscular mycorrhizal (VAM) fungus Glomus sp. 88 with or without Mussoorie rock phosphate (MRP) amendment in a nutrient-deficient natural sandy soil was studied. In the sandy soil of low fertility root colonization by VAM fungi was low. Inoculation with Glomus sp. 88 improved root colonization. At maturity, grain and straw yields as well as N and P uptake improved significantly following inoculation with PSM or the VAM fungus. These increases were higher on combined inoculation of PSM and the VAM fungus with MRP amendment. In general, a larger population of PSM was maintained in the rhizosphere of wheat in treatments with VAM fungal inoculation and MRP amendment. The results suggest that combined inoculation with PSM and a VAM fungus along with MRP amendment can improve crop yields in nutrient-deficient soils.
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    URL: http://dx.doi.org/10.1007/s003740050475
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