Lack of Cytokinin Activity of Quinolinol Sulfate

Kraft, Andrew S.; Ellis, Richard J.

doi:10.1104/pp.48.5.645

Cited by 2 publications

(3 citation statements)

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“…4. It has been suggested (2) that 8-OH-Q might act as a cytokinin; however, it was shown later (8,14) to be inactive in promoting cell division in tissue cultures. Dipyridyl has not been tested conclusively in soybean tissue culture, but preliminary results suggest no cell division activity.…”

Section: Resultsmentioning

confidence: 99%

“…The Chl retention effect of 8-quinolinol was thought to resemble that of a cytokinin (2), but the compound does not cause cell division in tissue culture bioassays (8,14 (7) showed that relatively high EDTA concentrations (50 mM) caused the bleaching of barley leaves in the light but improved the maintenance of Chl in the dark. These experiments were repeated with Avena leaf segments and a similar phenomenon was observed (Table I).…”

Section: Introductionmentioning

confidence: 99%

“…The Chl retention effect of 8-quinolinol was thought to resemble that of a cytokinin (2), but the compound does not cause cell division in tissue culture bioassays (8,14). In the case of EDTA, its effect in maintaining Chl in detached leaves is reported to depend upon whether or not the leaves are incubated in the light.…”

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confidence: 99%

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The Metabolism of Oat Leaves during Senescence

Tetley¹,

Thimann²

1975

Plant Physiol.

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The senescence of the first leaves of light-grown Avena seedlings when detached and placed in the dark is inhibited by a, a' -dipyridyl and a,a', a"-tripyridyl at concentrations between 10-and 104 M. Five other chelating agents exert similar inhibiting effects at concentrations 3 to 30 times higher. The senescence of etiolated leaves, as shown by loss of carotenoid and protein, is similarly inhibited. Ethylenediaminetetraacetate has a similar effect in the dark, though only at 10 mM and above, but in the light it causes bleaching of chlorophyll. It is deduced that an iron-containing system plays an essential part in the initiation of the senescence process.Occasional reports in the literature have indicated that the metal chelators 8-quinolinol and EDTA are capable of retarding senescence in darkened leaves (2,7,14). The Chl retention effect of 8-quinolinol was thought to resemble that of a cytokinin (2), but the compound does not cause cell division in tissue culture bioassays (8,14 (7) showed that relatively high EDTA concentrations (50 mM) caused the bleaching of barley leaves in the light but improved the maintenance of Chl in the dark. These experiments were repeated with Avena leaf segments and a similar phenomenon was observed (Table I). EDTA clearly promotes senescence in the light, but inhibits it in the dark. Control experiments with NaCl substituted for EDTA (Table I) show that the salt alone can cause an effect similar to that of EDTA in the light, but only at higher concentrations.Several other chelators are much more powerful. Those showing strong preservation of Chl in the dark at concentrations of 0.05 to 0.3 mm were: 8-hydroxyquinoline and its sulfonic acid derivative and o-phenanthroline (Fig. 1); those effective at well below 0.1 mm were: a, a'-dipyridyl and a, a , a'-tripyridyl (Fig. 2). The following chelators showed little or no activity at these relatively low concentrations: diethyldithiocarbamate, dimethyldithiocarbamate, salicylic acid, salicylhydroxamic acid, m-chlorobenzhydroxamic acid, 2-mercaptopyridine-N-oxide, EDTA, ethylenediamine, oxalate, citrate, and pyridine. The maximal activity of 8-OH-Q3 was not as great as that of the di-and tripyridyl compounds at their concentrations of maximum activity. Of the concentrations of di-and tripyridyl tested, small but clear effects were observed at 0.05 and 0.01 mM, respectively, while the maximal activity for Chl retention was at 1 and 0.1 mm respectively (Fig. 2). These values are approximately 100 times lower than the EDTA concentration that gave the best response (Table I). In the case of o-PH and 8-OH-Q, the concentrations giving maximal Chl retention also resulted in slight toxic effects such as moderate loss of turgor or localized areas of Chl retention. However, at the optimal dipyridyl concentration, the leaf segments remained turgid and the entire leaf 3 Abbreviations:

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%