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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of plant growth regulation 5 (1986), S. 29-35 
    ISSN: 1435-8107
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Tomato fruit ripening and ethylene production were inhibited following treatment with methyl bromide (MB). Methyl bromide significantly delayed ripening initiation in mature-green (MG) fruit and retarded the rate of ripening of turning (T) fruit as measured by color development and flesh softening. Treatment with MB caused an initial transient burst of ethylene production, but the subsequent ripening-associated increase in ethylene was delayed. Ethylene treatment partially overcame MB inhibition in MG fruit but had no affect on T fruit. The inhibition of ethylene production by MB appears to be due to lack of formation of 1-aminocycloprone-1-carboxylic acid (ACC) in MG fruit, whereas in T fruit lack of conversion of ACC to ethylene is indicated. A key feature of MB inhibition of ripening in tomato appears to be reduced sensitivity to ethylene.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Optical and quantum electronics 8 (1976), S. 465-467 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0789
    Keywords: Pseudomonas ; Disease predisposition ; Take-all ; Gaeumannomyces ; Seed treatment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Field plots were established in Indiana, Oregon, and Montana to evaluate the potential for biological control of various strains of bacteria as seed treatments to reduce the severity of take-all root, crown, and foot rot of wheat. The bacteria were grown in liquid broth Cas-amino acid broth media, mixed with finely ground peat, and applied to seed with methyl cellulose as a glue just before planting in field soils conducive for severe take-all. Autoclave-sterilized peat (minus bacteria) seed treatments increased take-all, immobilized Mn, and reduced plant vigor and grain yields. These effects were intensified when the pH of the natural peat was adjusted from 5.2 to 7.0 with CaCO3. The ability of the bacterial strains to counteract this peat-induced predisposition to take-all varied, and was influenced by planting site, genetic tolerance of the cultivar, and N treatment. Although the strains differed in their ability to suppress the peat-induced take-all, none of the isolates fully nullified the deleterious effects of the peat carrier. It is clear from this study that the carrier used with potential biological-contol agents may have a greater influence on disease than the biological agent.
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  • 4
    ISSN: 1432-2048
    Keywords: Cellulose ; Cx cellulase ; Fruit (ripening, softening) ; Persea (fruit ripening)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Avocado (Persea americana Mill.) fruit produce copious quantities of the enzyme Cx-cellulase (EC 3.2.1.4) during ripening. The possibility that Cx-cellulase is able to disrupt cellulose microfibril oranization was investigated using molecular weight (Mr), x-ray diffraction, and ultrastructural analyses of cell walls from unripe avocado fruit incubated with the purified enzyme. Results indicate that Cx-cellulase causes a downshift in the Mr of unbranched cell-wall polymers in the Mr range of 106–107 Da. There is an increase in the proportion of crystalline cellulose, and cellulose fibrils appear to lose cohesiveness in response to enzyme activity. We propose that Cx-cellulase attacks avocado cellulose at accessible sites in the peripheral and integral noncrystalline regions of the microfibril, resulting in a loss of cohesiveness within the fibril structure and an alteration in the binding of associated cell-wall matrix polysaccharides. The initial loss of avocado mesocarp firmness during fruit ripening may be linked to the onset of Cx-cellulase activity.
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  • 5
    ISSN: 1432-2242
    Keywords: Minimum ; Norm ; Restricted ; Likelihood ; Half-diallel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Computer simulation was used to compare minimum variance quadratic estimation (MIVQUE), minimum norm quadratic unbiased estimation (MINQUE), restricted maximum likelihood (REML), maximum likelihood (ML), and Henderson's Method 3 (HM3) on the basis of variance among estimates, mean square error (MSE), bias and probability of nearness for estimation of both individual variance components and three ratios of variance components. The investigation also compared three procedures for dealing with negative estimates and included the use of both individual observations and plot means as the experimental unit of the analysis. The structure of data simulated (field design, mating designs, genetic architecture and imbalance) represented typical analysis problems in quantitative forest genetics. Results of comparing the estimation techniques demonstrated that: estimates of probability of nearness did not discriminate among techniques; bias was discriminatory among procedures for dealing with negative estimates but not among estimation techniques (except ML); sampling variance among estimates was discriminatory among procedures for dealing with negative estimates, estimation techniques and unit of observation; and MSE provided no additional information to variance of the estimates. HM3 and REML were the closest competitors under these criteria; however, REML demonstrated greater robustness to imbalance. Of the three negative estimate procedures, two are of practical significance and guidelines for their application are presented. Estimates from individual observations were always preferable to those from plot means over the experimental levels of this study.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of low temperature physics 26 (1977), S. 525-532 
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We report the results of electron paramagnetic resonance studies of GdX (X=As, Sb, Bi, S, Se). The temperature dependence of the linewidth ΔH and effective g-factorg eff are discussed. Values for the Néel temperatureT N are inferred from coincident anomalies in ΔH andg eff. In the cases of X=S and Se, our estimates ofT N are significantly lower than theT N inferred from static susceptibility measurements. A possible source of the discrepancy is discussed.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Nutrient cycling in agroecosystems 21 (1989), S. 1-6 
    ISSN: 1573-0867
    Keywords: Corn ; tomato ; rice ; nitrate ; glutamine synthetase ; ammonium assimilation ; glutamate dehydrogenase ; asparagine synthetase ; pH
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Plant growth, ammonium assimilating enzyme activity, and free ammonium in tissue of different plant species were compared in the presence of either NO3 or NH4 forms of N at two pH levels in solution culture. Tomato and corn growth, but not rice growth, was reduced when NH4 was the sole form of N in the solution culture. Ammonium toxicity was more severe at low than higher pH. Glutamate dehydrogenase activity in roots of the three plant species was higher in the presence of NH4 than NO3 nitrogen. Asparagine synthetase activity was very low in roots of the three species regardless of the N form supplied. Glutamine synthetase activity in roots and shoots of rice was much higher than in tissue of tomato and corn. Glutamine synthetase activity in rice increased sharply in the presence of NH4, and much less free NH4 was detected in green tissues compared to tomato plants. Glutamine synthetase appears to be a key factor to detoxify NH4 in the leaves of rice.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Mycopathologia 132 (1995), S. 147-154 
    ISSN: 1573-0832
    Keywords: Mycobiota ; Seeds ; Sweet Corn
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Sixteen species of fungi were isolated from the pericarp, endosperm, scutellum, and embryo of low (〈75% germination), moderate (75–89%), and high vigor (〉89%) seedlots of supersweet sweet corn (sh2) hybrids over two years. Most frequently isolated species werePenicillium oxalicum, Rhizopus arrhizus (14.5%), andRhizopus spp (17.4%).Fusarium moniliforme, a common inhabitant in field or dent corn, was isolated from only 2.4% of the samples. The low mean isolation values may be the result of poor conditions for infection or the data may reflect the methods used including sterilization techniques or random tissue selection.Aspergillus niger, F. moniliforme, andP. oxalicum, were isolated at a significantly greater level than other fungi from the high vigor hybrids at 0.89, 0.46 m and 4.46 respectively compared to 0.04, 0, and 1.82 for the low vigor hybrids. When Total Fungi were compared mean isolations were significantly greater from the high vigor hybrids at 11.96, the moderate 8.79, or low 4.86 vigor groups. When data from seed sources for all vigor groups were compared, significantly greater mean isolations were obtained from Illinois Foundation Seed hybrids forCladosporium sp,R. arrhizus, andRhizopus spp., but greater rates were obtained forFusarium oxysporum from the Asgrow hybrids. Isolation frequencies for the 16 species were not significantly different between the seed tissue types from any of the hybrids evaluated during this investigation. Results from this study showed that there is a diverse group of fungi present within thesh2 seed and seed treatments must be developed which will minimize seed rot and seedling blight from both internal seedborne and external pathogens.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Journal of statistical physics 65 (1991), S. 1155-1159 
    ISSN: 1572-9613
    Keywords: Frenkel excitons ; three-dimensional systems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A numerical study is made of the effect of disorder on the trapping of Frenkel excitons in three-dimensional systems atT=0 K. A Gaussian distribution of optical transition frequencies is assumed. The disorder enhances the decay of ak = 0 exciton created by pulsed optical excitation, but reduces the overall exciton trapping rate. An interpretation of the results in terms of increased exciton scattering and reduced exciton mobility is outlined.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of statistical physics 90 (1998), S. 873-888 
    ISSN: 1572-9613
    Keywords: Spin glasses ; long-range interactions ; freezing temperature ; localized and extended states
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The onset of spin-glass freezing in dilute Ising systems with long-range interactions is investigated with the use of numerical simulations. We show that taking pair correlations explicitly into account results in the renormalization of the interaction matrix and suppression of the density of localized states compared with conventional mean field theory. Application of the theory to the RKKY interaction in the dilute limit raises the question of the appropriate boundary eigenvalue of the effective interaction matrix that separates localized and extended states. We identify the onset of spin-glass freezing with the temperature T g at which this boundary eigenvalue is equal to one. Numerical simulations reproduces the linear concentration dependence of T g in the very dilute limit, in agreement with scaling relations, and show a significant improvement over the conventional mean-field theory in the value obtained for the freezing temperature.
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