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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 50 (1980), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Tracheal sap was extracted from sections of stems (0.5 to 1.5 cm in diameter and 7.5 to 15.0 cm in length) of orange trees (Citrus sinensis (L.) Osbeck cv. Washington Navel) by using a combination of the vacuum and liquid displacement methods. The volume of sap obtained and its concentration of nitrogenous compounds were dependent on the volume of displacing liquid used for the extraction. Four ml of water-saturated 1-butanol extracted essentially all of the xylem fluid present in the stem sections without apparent production of artifacts.The time of sampling affected the nitrogen concentration of the tracheal sap, but not the content of xylem nitrogen per volume of stem material. The orientation of the stems in the tree and the diameter of the stems had an effect on their contents of xylem nitrogen, with southeastern orientation and thinner stems showing higher concentrations.We could not detect the presence of ammonium, nitrites or proteins in the tracheal sap of orange trees. Most of the nitrogen was present as amino acids and about 2% of the total in the form of nitrates. The qualitative composition of amino acids, as determined by TLC, was the same both in winter and spring tracheal sap. The main components of the sap were proline and arginine in winter, and these amino acids together with asparagine and aspartic acid in spring.
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 59 (1983), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Samples of tracheal sap of Citrus sinensis (L.) Osbeck cv. Washington Navel were taken from field trees throughout the year and the nitrogen composition of the sap was determined. The nitrogenous fraction of the sap was composed mainly of free amino acids (92–97% of total nitrogen) and nitrates throughout the year. Proline was the most abundant amino acid during almost the entire cycle, and its concentration was especially high during the autumn and winter period. Nevertheless, a significant part (40–60%) of the total organic nitrogen was transported as arginine. Total nitrogen as well as amino acids and nitrates were maximal at spring flush. At spring flush and summer flush there was also a diversification of α-amino nitrogen among different amino acids. During the spring flush, nitrates, asparagine and γ-aminobutyric acid in the xylem sap seemed to have a radicular origin, whereas glutamic acid and arginine were released from the surrounding parenchyma. The results suggest a metabolic transformation in the wood parenchyma of nitrogenous compounds coming from the roots (including reduction of nitrates) and a turnover of different nitrogen metabolites between the xylem and surrounding cells.
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 61 (1984), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The changes of protein and amino acid contents of young and old leaves from field citrus trees [Citrus sinensis (L.) Osbeck cv. Washington Navel] were studied throughout the year. the total protein content of old leaves decreased during the spring and summer growths, whereas in young developing leaves it increased rapidly. The end of the spring and summer flushes was followed by a quick recovery of the initial protein content due to a process of reversible senescence. The evolution of SDS-PAGE proteinograms indicated that most of the foliar proteins contributed to the nitrogen mobilization during the spring and summer growth periods. A protein band of molecular weight ca 55,000, probably containing the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase, decreased relatively more than the others. The amino acid content of the leaves increased during winter time due to the accumulation of proline, which was mobilized during the spring flush. The possible nitrogen storage function of proline is discussed.
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  • 4
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 408 (1983), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Planta 147 (1980), S. 451-456 
    ISSN: 1432-2048
    Keywords: Abscisic acid ; Auxin ; Fruit-set ; Gibberellin ; Parthenocarpy ; Pisum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The development of parthenocarpic fruits of Pisum sativum L. cv. Alaska was induced by the application of different plant-growth regulators in aqueous solution to the emasculated ovaries in untopped plants. At least one compound in each of the groups of auxins (2,4-dichlorophenoxyacetic acid), cytokinins (benzyladenine), and gibberellins (gibberellic acid) was found active. Gibberellic acid (GA3), however, was the only substance which produced pods similar to those of fruits with seeds. The length of the pods obtained by GA3 was a linear function of the logarithm of the concentration of GA3 in the solution. The effect of GA3 (at a concentration which produced 50% of the maximum pod length) was enhanced by a simultaneous application of 2,4-dichlorophenoxyacetic acid. Abscisic acid (ABA) counteracted the effect of GA3 and of topping. The results suggest that gibberellins and ABA may exert a major regulatory control in natural fruit-set. Peas can be used for the assay of fructigenic activity and is an advantageous material for the study of the mode of action of gibberellins on fruit-set.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Planta 147 (1980), S. 444-450 
    ISSN: 1432-2048
    Keywords: Abscisic acid ; Auxin ; Cytokinin ; Decapitation ; Fruit-set ; Gibberellin ; Parthenocarpy ; Pisum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The influence of removing the apical shoot and different leaves above and below the flower on the fruit-set of unpollinated pea ovaries (Pisum sativum L. cv. Alaska) has been studied. Unpollinated ovaries were induced to set and develop either by topping or by removing certain developing leaves of the shoot. Topping had a maximum effect when carried out before or on the day of anthesis, and up to four consecutive ovaries were induced to set in the same plant. The inhibition of fruit-set was due to the developing leaves and not to the apex. The third leaf above the first flower, which had a simultaneous development to the ovary, had the stronger inhibitory effect on parthenocarpic fruit-set. The application of different plant-growth regulators (indoleacetic acid, naphthylacetic acid, 2,4-dichlorophenoxyacetic acid, gibberellic acid, benzyladenine and abscisic acid) did not mimic the negative effect of the shoot.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Plant growth regulation 2 (1984), S. 197-208 
    ISSN: 1573-5087
    Keywords: Cowpea ; elongation ; epicotyl ; gibberellins ; Vigna sinensis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The physiological characteristics of the response of excised cowpea (Vigna sinensis cv Blackeye pea No. 5) epicotyls to gibberellins (GAs) were studied. Epicotyl explants, retaining the petioles and a 2-cm portion of hypocotyl, were placed upright in small vials containing water. Plant growth substances were injected into the subapical tissues as ethanol solutions. Epicotyl elongation resulting from treatment with 0.5 μg of GA ranged between 5 and 13 times that of the control, depending on the GA applied. With GA1, no differences were obtained with explants prepared from 5 to 9-day-old seedlings. The increase in elongation could be detected within 6 h of treatment, and the stimulus of a single application lasted at least 4 days. Final elongation was proportional to the logarithm of the amount of GA, applied, 0.01 to lug. The response to GA treatment was limited to the upper part, the most sensitive zone being located between 2 to 4 mm below the apex of the epicotyl; this effect was entirely due to cell elongation. The induction of epicotyl elongation by GAs seems to be specific and independent of the effect of auxin. IAA had no effect on elongation and 4-chloro-phenoxyisobutyric acid (PCIB) did not affect the response to GA1
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Plant growth regulation 2 (1984), S. 209-216 
    ISSN: 1573-5087
    Keywords: Auxin ; cowpea ; elongation ; ethylene ; gibberellin ; Vigna sinensis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effect of gibberellin A1 (GA1) on production of ethylene by cowpea (Vigna sinensis cv Blackeye pea no. 5) epicotyl explants and its relationship to epicotyl elongation was investigated. The explants were placed upright in water and incubated in sealed culture tubes or in large jars. GA, and IAA in ethanol solution were injected into the subapical tissues of the decapitated epicotyls. Cowpea epicotyl explants elongated after GA but not after IAA treatment, and they were very sensitive to exogenous ethylene. As little as 0.14 μ1/1 ethylene reduced significantly GA1-induced epicotyl elongation. Treatment with GA1 induced the production of ethylene which began 10 h after GA application, showed a peak at about 22 h and then declined. The yield of ethylene was proportional to the amount of GA, injected. The inhibition of epicotyl elongation in closed tubes was avoided by absorbing ethylene released with Hg(Cl04)2 , or by adding AVG to the incubation solution to inhibit ethylene production. Treatment with IAA elicited a rapid production of ethylene which ceased about 10 h after application. The effects of IAA and GA1 on ethylene production were additive.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    BIT 20 (1980), S. 501-510 
    ISSN: 1572-9125
    Keywords: Nonlinear equations ; numerical solution ; Brent's method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract We describe an implementation of a generalization of Brent's method for solving systems of nonlinear equations. Some important features of the algorithm, like step control, discretization of derivatives and stopping criteria, are discussed. In particular we give numerical experiences which show that a stopping criterion proposed by D. Gay is efficient.
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