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  • 1
    Electronic Resource
    Electronic Resource
    Effect of cytokinins supplied via the xylem at multiples of endogenous concentrations on transpiration and senescence in derooted seedlings of oat and wheat (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 19 (1996), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: This study was conducted lo determine whether naturally occurring xylem cytokinins, when supplied to leaves via the xylem at approximately endogenous concentrations, increase transpiration and delay senescence in selected monocot species (oat and wheat). The concentrations of some of the major cytokinins (zeatin, dihydrozeatin, ciszeatin and their ribosides, the O-glucosides and nucleotides) were determined in the xylem exudate of oat and wheat seedlings by radioimmunoassay. Evidence is presented that the small volume of exudate (4–5 mm3) collected per plant was xylem sap in transit at the time of shoot excision. Using the data on cytokinin levels, the individual bases and ribosides (and a base/riboside mixture), at multiples of concentrations determined in xylem sap, were tested in transpiration and senescence bioassays. The individual O-glucosides (and mixtures of the O-glucosides) were similarly tested at (i) multiples of the molar concentrations of the corresponding bases and ribosides, and/or at (ii) multiples of the endogenous concentrations. Similarly, zeatin and dihydrozeatin nucleotides were tested at multiples of the molar concentration of zeatin riboside and, in some instances, at multiples of endogenous concentrations.Our results suggest that, at least in oat and possibly in wheat, zeatin-type bases, ribosides and O-glucosides supplied to the leaf in xylem sap are likely to play a role in regulating transpiration in vivo. O-glucosides in oat xylem sap may be important regulators of leaf senescence in the intact plant. The nucleotides were present in xylem sap at lower concentrations than most of the bases, ribosides and O-glucosides. The nucleotides appear likely to play a lesser role than the bases, riboside and O-glucosidcs in controlling transpiration and senescence in the intact plant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1996.tb00384.x
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  • 2
    Electronic Resource
    Electronic Resource
    A procedure for quantification of cytokinins as free bases involving scintillation proximity immunoassay (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 95 (1995), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Cytokinins occur in a diversity of forms and determination of their individual levels requires extensive purification. However, determination of the total level of each major base in free, riboside and nucleotide forms would often be adequate. Hence, a methanolysis procedure which releases cytokinin bases from 9-ribosyl derivatives was developed and applied to plant extracts. A simple procedure, involving low pressure column chromatography, for purification of the cytokinin bases in treated extracts, and a scintillation proximity immunoassay for their quantification, were developed. The total level of each cytokinin base [N6-(2-isopentenyl)adenine, zeatin and dihydrozeatin] in free and ribosylated forms determined by these methods is reported for several plant tissues and the results are compared with those obtained after additional purification by HPLC. Values for zeatin were not changed by HPLC but isopentenyl-adenine and dihydrozeatin levels were usually reduced indicating the presence of unknown compounds which cross-react in the immunoassay. Modifications to the above purification method to quantify O-glucosyl cytokinins are also described.The methods described facilitate the quantification of the total amount of each cytokinin base in forms closely associated with cytokinin action, and the detection of cytokinin biosynthesis by labelled precursor incorporation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1995.tb00813.x
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  • 3
    Electronic Resource
    Electronic Resource
    Structural and functional analysis of nitrogenase genes from the broad-host-range Rhizobium strain ANU240
    Amsterdam : Elsevier
    Gene 77 (1989), S. 141-153 
    Details
    ISSN: 0378-1119
    Keywords: Recombinant DNA ; gene duplication ; nitrogen fixation ; transcriptional fusions
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0378-1119(89)90368-5
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  • 4
    Electronic Resource
    Electronic Resource
    Use of isopentenyladenosine and dihydrozeatin riboside antibodies for the quantification of cytokinins (1987)
    Springer
    Journal of plant growth regulation 6 (1987), S. 159-182 
    Details
    ISSN: 1435-8107
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Antisera have been raised in rabbits against dihydrozeatin riboside and isopentenyladenosine, and their cross-reactivity characteristics have been examined in detail. These antisera, together with an antiserum previously raised against zeatin riboside, have been employed in radioimmunoassays. Separative procedures that enable a wide range of naturally occurring cytokinins to be separated prior to analysis by radioimmunoassay have been developed. The accuracy with which the following cytokinins can be quantified by our methods, which employ tritiated cytokinin recovery markers, has been estimated: zeatin riboside, zeatin, dihydrozeatin riboside, dihydrozeatin, O-glucosyl zeatin riboside, O-glucosyl zeatin, O-glucosyl dihydrozeatin riboside, O-glucosyl dihydrozeatin, zeatin-9-glucoside, zeatin-7-glucoside, lupinic acid, isopentenyladenosine, and isopentenyladenine.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02303051
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  • 5
    Electronic Resource
    Electronic Resource
    Cytokinins of dryZea mays seed: Quantification by radioimmunoassay and gas chromatography-mass spectrometry (1988)
    Springer
    Journal of plant growth regulation 7 (1988), S. 179-196 
    Details
    ISSN: 1435-8107
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The endogenous cytokinins present in dryZea mays seed were determined using both radioimmunoassay and gas chromatography—mass spectrometry. Similar values for bases and ribosides were obtained by the two methods. The cytokinins present in embryo and endosperm were estimated separately using radioimmunoassay; similar levels of cytokinins were found in these two tissues. The major cytokinins detected on a whole-seed basis were dihydrozeatin riboside, O-glucosyldihydrozeatin riboside, zeatin 9-glucoside, zeatin, and the nucleotides of zeatin, dihydrozeatin, and isopentenyladenine. Cytokinin levels in the mature dry seed were considerably lower than cytokinin levels published in the literature for immature seed. Unexpected activity in the radioimmunoassays was detected in the wash from the DEAE cellulose column chromatography step. The compound(s) responsible for this activity did not have the solvent partitioning characteristics of a cytokinin base or riboside. They eluted as a single fraction following high-performance liquid chromatography on a Zorbax C8 column; this fraction showed no activity in theAmaranthus bioassay for cytokinins, but inhibited the activity of authentic zeatin riboside present at an optimal concentration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02024681
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Radioimmunoassay for quantifying the cytokininscis-zeatin andcis-zeatin riboside and its application to xylem sap samples (1989)
    Springer
    Journal of plant growth regulation 8 (1989), S. 93-105 
    Details
    ISSN: 1435-8107
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract An antiserum against the cytokinincis-zeatin riboside was raised in rabbits and characterized for use in radioimmunoassays. Cross-reactivity studies demonstrated the specificity of the selected antiserum forcis-zeatin riboside andcis-zeatin in preference to a range of cytokinins and other purines. HPLC systems were developed that separatedcis-zeatin andcis-zeatin riboside from zeatin/dihydrozeatin and zeatin riboside/dihydrozeatin riboside, respectively. These systems enabled the separation of these compounds in xylem sap samples of wheat and oats and their quantification using radioimmunoassay. A TLC system for the separation ofcis-zeatin andcis-zeatin riboside from zeatin/dihydrozeatin and zeatin riboside/dihydrozeatin riboside, respectively, is also described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02025277
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  • 7
    Electronic Resource
    Electronic Resource
    Mass spectrometric identification of indole compounds produced by Rhizobium strains (1982)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 9 (1982), S. 429-437 
    Details
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The following indole compounds have been unequivocally identified and semi-quantitated in culture supernatants of Rhizobium strains by gas chromatography mass spectrometry: indole-3-aldehyde, trytophol, indole-3-carboxylic acid, indole-3-glycollc acid, indole-3-actic acid, indole-3-glyoxylic acid, N-acethyl-L-tryptophan and indole-3-pyruvic acid, as well as indole-3-acetic acid. The strains included a number of chosen Rhizobium mutants defective in various stages of nodule formation, and the biological implications of the findings are discussed. Two alternative approaches to sample purification were taken, one based primarily on solvent partitioning and the other on high-performance liquid chromatography. The advantages of each method are discussed. Gas chromatographic retention times and mass spectra are given for the TMS derivatives of 17 authentic indole standards.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200091005
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