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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Plant growth regulation 15 (1994), S. 193-206 
    ISSN: 1573-5087
    Keywords: elongated ; gibberellins ; mutants ; response ; synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Recent advances in the study of GA mutants are reviewed. Endogenous GAs in the vast majority of GA synthesis and response mutants have now been quantified by physicochemical means, and the implications of the results are discussed. In recent papers the effects of synthesis mutations on processes other than stem elongation have received increased attention, as has the advent of mutants with reportedly elevated GA levels. The ‘feedback theory’ has been formulated, explaining paradoxical observations on endogenous GA levels in certain response mutants. In a significant breakthrough, a GA biosynthesis gene has been cloned, paving the way for a combined approach to future GA research, involving GA mutants, physicochemical analyses, and molecular techniques.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-5087
    Keywords: elongation ; gibberellins ; A4, A9, A5 and A3 ; le mutant ; Pisum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Gibberellin A4 (GA4) was identified for the first time in the garden pea (Pisum sativum) L.), by gas chromatography-mass spectrometry. However, in wild-type shoots the level of GA4 was only about 6% of the level of GA1, and it is therefore unlikely that GA4 plays a major role per se in the control of pea stem elongation. In shoots of the le mutant, GA4 was not detected, while the level of GA9 was approximately twice that found in the wild-type. The le mutation also markedly reduced the elongation response to applied GA9. It appears, therefore, that in Pisum the le mutation blocks the 3β-hydroxylation of GA9 to GA4, in addition to the 3β-hydroxylation of GA20 to GA1. In contrast, the le mutation did not reduce the response to applied GA5, suggesting the step GA5 to GA3 is not catalysed by the enzyme controlled by the Le gene. The step GA5 to GA3 was confirmed in peas by metabolite analysis after treatment with deuterated GA5.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The fraction of cell capable of division was determined for (1) population of the human diploid cell strains, WI38 after different numbers of subcultivations in vitro and (2) a single population of WI38 cells at intervals throughout its entire in vitro lifespan. In both cases the percentage of cells capable of division decreased with increasing age in tissue culture. The rate and the magnitude of the decrease is sufficient to account for the limited in vitro lifespan reported by other investigators. Furthermore, the decrease in the fraction of cells capable of division in similar in some respects of senescence among human populations.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: By mapping the location of isolated single cells; and then counting the number of cells at each location as a function of time. it was possible to accumulate data on the growth history for each of a large group of clones. The clone size distribution, its mean and standard deviation were computed for each day in culture. Variations in schedule of medium change and time of exposure to trypsin, did not measurably affect variation in clone size. Neither could clone size variation be accounted for on the basis of (1) occurrence of nondividing cells nor (2) presence of heritable growth rate variants in the population. It is probable that clone size variation under our conditions is primarily a consequence of a highly variable interdivision time among the constituent cells.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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