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  • 1
    Electronic Resource
    Electronic Resource
    The rhizosphere effect of tea on soil microbes in a Himalayan monsoonal location (1996)
    Springer
    Biology and fertility of soils 21 (1996), S. 131-137 
    Details
    ISSN: 1432-0789
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Monthly investigations of the microbial population associated with tea soils, in terms of colony-forming units assessed by the plate-count method, were carried out at three different soil depths for a period of 12 months. Three groups of microbes, bacteria, actinomycetes, and fungi, were examined. Contrary to general observations, the rhizosphere: soil ratios were found to be consistently below 1 in samples taken from established tea bushes, indicating an overall negative rhizosphere effect. Interactions among certain microorganisms may also have contributed to this effect. Nevertheless, the rhizosphere of young tea plants and that of a number of other perennial plants, of different ages, growing in established tea fields, appeared to stimulate microbial growth. The negative effect of the rhizosphere of older tea bushes does not appear to be a common phenomenon that is related to the aging of plants in general, but seems to be unique and specific to tea plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00335924
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  • 2
    Electronic Resource
    Electronic Resource
    The Biosynthesis and Metabolism of Cytokinins (1983)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Plant Physiology 34 (1983), S. 163-197 
    Details
    ISSN: 0066-4294
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.pp.34.060183.001115
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  • 3
    Electronic Resource
    Electronic Resource
    Cytokinin biochemistry in relation to leaf senescence. VII. Endogenous cytokinin levels and exogenous applications of cytokinins in relation to sequential leaf senescence of tobacco (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 86 (1992), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The cytokinin complex in tobacco leaves of various maturities was characterized by radioimmunoassay and mass spectrometry. Zeatin was the major base, whereas zeatin riboside was identified as the main riboside. in leaves of all maturities studied. Relative to upper younger leaves, the basal yellow leaves had reduced levels of both cytokinin bases and ribosides. Exogenous applications of dihydrozeatin and zeatin to detached tobacco leaves in amounts sufficient to delay senescence, elevated cytokinin base and riboside levels 2–5 fold. Presenescent and senescent leaves of intact plants showed quantitatively similar changes in cytokinin content. which therefore appear to be of significance in control of senescence. When supplied exogenously, the principal cytokinin bases found to occur in tobacco leaves (zeatin and dihydrozeatin) were markedly more effective than auxins and gibberellic acid in retarding senescence. Localised application of cytokinins to leaf blades of detopped plants was much less effective than application to intact plants. The cytokinin induced senescence retardation in tobacco leaves was independent of effects on directed metabolite transport. Evidence that endogenous levels of active cytokinins in intact tobacco leaves are involved in control of sequential leaf senescence is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1992.tb01334.x
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  • 4
    Electronic Resource
    Electronic Resource
    Cytokinin biochemistry in relation to leaf senescence. VIII. Translocation, metabolism and biosynthesis of cytokinins in relation to sequential leaf senescence of tobacco (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 86 (1992), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Cytokinin bases (zeatin and dihydrozeatin) and ribosides (zeatin riboside and dihydrozeatin riboside) were identified as major cytokinins in tobacco xylem sap by radioimmunoassay. When 3H-labelled zeatin riboside or dihydrozeatin riboside were supplied to tobacco plants via the xylem, leaves of differing maturity did not differ appreciably in level of radioactivity or in metabolism of the cytokinin. The major metabolites of zeatin riboside in leaves were adenine, adenosine and adenine nucleotides, whereas that of dihydrozeatin riboside was dihydrozeatin 7-glucoside. Incorporation of [14C]adenine into zeatin was evident in upper green leaves. indicating that young leaves have the capacity to synthesize cytokinins in situ. In contrast, fully expanded green leaves and senescing tobacco leaves exhibited little or no incorporation of [14C]adenine into cytokinins. This difference in cytokinin biosynthetic capacity may contribute to the differing cytokinin levels in leaves of different matirity, and may participate in control of sequential leaf senescence in tobacco.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1992.tb01335.x
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  • 5
    Electronic Resource
    Electronic Resource
    Cytokinin biochemistry in relation to leaf senescence. VI. Effect of nitrogenous nutrients on cytokinin levels and senescence of tobacco leaves (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 84 (1992), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The effect of nitrogenous nutrients on endogeneous cytokinins and senescence of tobacco leaves was investigated. Ammonium nitrate was the most effective in retarding senescence and its activity was attributed principally to NH4+ ions. Repeated applications or a continuous supply of ammonium nitrate was required for maximal retardation of tobacco leaf senescence. Ammonium nitrate solution supplied via the petioles reduced the senescence retarding effect of dihydrozeatin applied directly to the laminae of detached tobacco leaves. Ammonium nitrate also elevated the endogenous levels of cytokinins (especially zeatin and dihydrozeatin) particularly in growing tobacco leaves excised from near the apex of the plant. Ammonium nitrate induced retardation of leaf senescence may be mediated at least partly by its effect on foliar cytokinin content.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1992.tb04663.x
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  • 6
    Electronic Resource
    Electronic Resource
    Identification of cytokinins in primary crown gall tumours of tomato (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 12 (1989), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract. Identification of the cytokinin complex of primary crown gall tumours of tomato (Lycopersicon esculentum L.) by combined gas chromatography-mass spectrometry has been described. Several cytokinins have been identified which included zeatin, dihydrozeatin, isopentenyladenine, and their respective riboside and nucleotide derivatives. In addition, 6-benzylaminopurine, its riboside and the corresponding nucleotide have also been identified as major endogenous compounds in this tissue. This would appear to be the first report on the identification of cytokinins from a primary crown gall tumour tissue using unequivocal methods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1989.tb01941.x
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  • 7
    Electronic Resource
    Electronic Resource
    Cytokinin biochemistry in relation to leaf senescence I. The metabolism of 6-benzylaminopurine and zeatin in oat leaf segments (1983)
    Springer
    Journal of plant growth regulation 2 (1983), S. 89-102 
    Details
    ISSN: 1435-8107
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The metabolism of zeatin and that of 6-benzylaminopurine (BAP) have been compared in oat leaf segments in relation to the markedly differing ability of these cytokinins to retard senescence of such segments. Free BAP and a highly active senescence-retarding metabolite of BAP were detected in oat leaf segments supplied with BAP. The metabolite was identified by mass spectrometry and chromatography as 3-β-D-glucopyranosyl-BAP. The major metabolite of BAP was the 9-glucoside, but this lacked significant senescence-retarding activity. In contrast, in leaf segments supplied with zeatin, no free zeatin and no senescence-retarding metabolite of zeatin were detectable. The major metabolites of zeatin were adenosine, adenine nucleotides, the 9-glucoside, and unidentified polar metabolites. The differing activities of zeatin and BAP in the oat-leaf senescence bioassay appear to be, at least partially, a consequence of their differing metabolism and are not attributable to differences in uptake.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02042237
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  • 8
    Electronic Resource
    Electronic Resource
    Regulators of cell division in plant tissues XXIX. The activities of cytokinin glucosides and alanine conjugates in cytokinin bioassays (1983)
    Springer
    Journal of plant growth regulation 2 (1983), S. 103-115 
    Details
    ISSN: 1435-8107
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In a number of cytokinin bioassays, the activities of the following compounds were compared: 3-, 7-, and 9-glucosides of 6-benzylaminopurine (BAP); 7- and 9-glucosides of zeatin; O-glucosides of zeatin, dihydrozeatin, and their ribosides; 9-alanine conjugates of zeatin, and BAP. The bioassays included the radish cotyledon, theAmaranthus betacyanin, the oat leaf senescence, and the tobacco pith callus. Cytokinin activity was markedly reduced by 7- and 9-glucosylation in nearly all bioassays, but 3-glucosylation of BAP and O-glucosylation of the zeatin sidechain usually had little effect on activity. However, there were two notable exceptions to this generalization: the activity of O-glucosylzeatin markedly exceeded that of zeatin in the oat leaf senescence assay; 9-glucosyl-BAP and free BAP were similarly active in retarding the senescence of radish leaf discs. The 9-alanine conjugate of zeatin (lupinic acid) and of BAP were markedly less active than zeatin and BAP, respectively, in all bioassays, but the responses evoked by these conjugates at high concentrations in theAmaranthus bioassay approached those caused by the corresponding base. The activities of several new compounds related to the alanine conjugate of BAP were also assessed. To serve as a guide in the selection of the most suitable bioassay for detection of the above-mentioned cytokinin conjugates, the lowest detectable amounts in selected bioassays have been compared.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02042238
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  • 9
    Electronic Resource
    Electronic Resource
    Cytokinin biosynthesis in crown-gall tissue ofVinca rosea (1983)
    Springer
    Planta 159 (1983), S. 50-59 
    Details
    ISSN: 1432-2048
    Keywords: Crown gall ; Cytokinin biosynthesis ; Nucleotide ; Vinca
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract When care was taken to minimise the effects of phosphatase activity during extraction ofVinca rosea crown-gall tumour tissue, a large proportion of extractable cytolinin activity was present in the nucleotide fraction. Analysis using ion-exchange chromatography followed by enzymic or chemical degradation and subsequent identification of the biologically active material indicated that this activity was due to zeatin riboside 5′-monophosphate. This was also the major radiolabelled cytokinin formed when this tissue was supplied with [14C]adenine. The incorporation of radioactivity from [14C]adenosine into free cytokinins was also shown, but no incorporation of radioactivity was found when [3H]mevalonic acid lactone was supplied to this tissue under the same conditions. In parallel experiments using normal stem callus tissue ofV. rosea, no incorporation of [14C]adenine into free cytokinins was observed. The significance of these results is discussed in relation to a possible transfer-RNA-independent pathway of cytokinin biosynthesis, operating primarily at the mononucleotide level.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00998814
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  • 10
    Electronic Resource
    Electronic Resource
    Cytokinins in transfer RNA of normal and crown-gall tissue of Vinca rosea (1983)
    Springer
    Planta 159 (1983), S. 178-181 
    Details
    ISSN: 1432-2048
    Keywords: Crown gall ; Cytokinin biosynthesis ; Transfer RNA ; Vinca
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract cis-Zeatin riboside was identified in transfer-RNA hydrolysates from both normal and crown-gall tissue of Vinca rosea L. The trans-isomer was associated exclusively with the crowngall transfer-RNA. The importance of these observations is discussed in relation to biosynthesis of free cytokinins.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392990
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