Showing papers on "Zeatin published in 1971"

The role of cytokinins in clubroot formation

Abstract: The occurrence of cytokinins in healthy turnips (Brassica campestris L var rapa “Gelria”) and in turnips infected with Plasmodiophora brassicae has been studied Extracts of clubroots were about three times as active in cytokinin bioassays as extracts of healthy turnips Infected and healthy turnips contain compounds with the same RF values Extracts from clubroots have been partially purified and cochromatographed on paper and on thin layer silica gel with zeatin and zeatin riboside One of the active fractions upon silylation showed a gas chromatographic retention time which coincided with the retention time of silylated zeatin Total cytokinin activity was estimated to be 0·1 to 1·0 mg zeatin equivalent/100 kg fresh weight clubroots Healthy turnips contain 10 to 100 times lower amounts of cytokinins These findings are consistent with the fact that explants infected with P brassicae are independent of cytokinins and auxins for their growth, whereas callus of healthy turnip tissue requires these hormones for continued growth However, infected callus did not grow very well on media deficient in both growth hormones A considerable difference was found between the ratios of cytokinins and auxins which must be supplied to obtain maximum yield of infected and healthy callus tissue

The Metabolism of Hormones during Seed Germination and Dormancy: II. The Metabolism of 8-C-Zeatin in Bean Axes.

Abstract: 8-(14)C-Zeatin is taken up rapidly and is extensively metabolized by excised bean axes during a 12-hour incubation at 26 C. Most of the radioactivity is found in the 80% ethanol soluble fraction and consists of zeatin, zeatin riboside, zeatin-5'-ribotide, as well as corresponding dihydrozeatin derivatives. The characterization of (14)C-dihydrozeatin included crystallization to constant specific radioactivity. No cleavage of the zeatin side chain to adenine, hypoxanthine, their ribosides, or glycylpurine was detected. Dihydrozeatin has been previously isolated from yellow lupin seeds, and our experiments indicate that it can be derived through reduction of the side chain from preexisting cytokinin. While the total amount of zeatin metabolized is not affected by growth-inhibiting concentrations of abscisic acid or cycloheximide, the conversion to dihydrozeatin derivatives is curtailed. Although somewhat less effective than zeatin and zeatin riboside, dihydrozeatin and dihydrozeatin riboside also counteract the abscisic acid-induced growth inhibition.

Changes in the Cytokinins of Radish Roots during Maturation

Abstract: The cytokinins of developing radish roots were extracted, partially purified, and separated by thin-layer chromatography into three distinct bands of activity. One band was identified chromatographically as zeatin ribonucleotide and another was indistinguishable from a mixture of zeatin and zeatin ribonucleoside. The third band was not identified, but it was not a derivative of zeatin or of isopentenyladenine. The unidentified cytokinin had physiological properties quite different from those of the zeatin derivatives. The zeatin-based cytokinins increased in radish roots with the onset of cambial activity, and reapplication of these cytokinins to cultured primary roots stimulated cambial activity. The unidentified cytokinin became abundant only after extensive secondary thickening had occurred, and it was localized almost entirely in the xylem. It did not stimulate cambial activity in cultured roots. The evidence indicates that zeatin and its derivatives regulate cambial activity in radish, and that the unidentified cytokinin may be synthesized in the roots and transported to the shoot.

Cytokinins extracted from pinto bean fruit.

Abstract: Extracts from various parts of Phaseolus vulgaris L. var. Pinto plants were found to exhibit cytokinin activity with the highest levels present in extracts of the fruit tissue. To separate the cytokinins present in the fruit, extracts were chromatographed in several solvent systems. Bioassays of chromatograms indicated the presence of active factors in those regions of migration associated with several known N-6-substituted aminopurines.Ultraviolet and mass spectral studies confirm the presence of a mixture of N-6-substituted aminopurines in the active material isolated by cation exchange resin chromatography. The evidence strongly supports the conclusions that dihydrozeatin is naturally occurring as the free base and possibly as a ribonucleoside. Further, zeatin appears to occur mainly as a glycosidic compound which is altered by KMnO(4) treatment and is hydrolyzed under acid conditions.

Auxins and cytokinins exuded during formation of roots by detached primary leaves and stems of dwarf French bean (Phaseolus vulgaris L.)

Abstract: Hypocotyls of detached stems standing in culture solution produced adventitious roots sooner than did petioles of detached primary leaves. An auxin, probably indol-3-ylacetic acid, appeared in the solutions before the hypocotyls or petioles produced roots. After attaining a maximum, the amounts of auxin in the solutions decreased as fewer roots were formed. Two cytokinins were found in the culture solutions; one had a similar Rf to zeatin, the other ran more slowly on chromatograms. The amounts of cytokinin in the solutions were associated with root formation. Stems soon died unless their hypocotyls formed roots, but the primary leaves survived without roots forming provided a callus formed on the petiole. Hence adventitious roots, or callus tissues, may have produced cytokinins that replaced those produced by the original roots, found in sap exuded from the stem stumps, and were essential for survival of the stems and leaves.

Influence des racines sur le développement végétatif ou floral des bourgeons cotylédonaires chez le Scrofularia arguta: role possible des cytokinines

Abstract: Influence of roots on the vegetative or floral development of cotyledonary buds of Scrofularia arguta Sol.: A possible cytokinin role. This study shows that the presence of “nonabsorbing roots” insures a vegetative development of cotyledonary buds cultured in vitro whereas buds growing without roots produce flowers early. In the same way, roots suppress floral expression of axillary meristems of the same cotyledonary buds and induce these buds to vegetative functioning. Various trophic modifications in the culture medium are ineffective on non-rooted buds as also are gibberellin As and adenine. On the contrary, several cytokinins (kinetin, benzyladenine and zeatin) exert the same influence as roots. These results suggest that roots regulate meristematic functioning through cytokinins.

Auxins and Cytokinins Exuded during Formation of Roots by Detached Primary Leaves and Stems of Dwarf French Bean (Phaseolus vulgaris L.)

Abstract: Summary. Hypocotyls of detached stems standing in culture solution produced adventitious roots sooner than did petioles of detached primary leaves. An auxin, probably indol-3-ylacetic acid, appeared in the solutions before the hypocotyls or petioles produced roots. After attaining a maximum, the amounts of auxin in the solutions decreased as fewer roots were formed. Two cytokinins were found in the culture solutions; one had a similar Rf to zeatin, the other ran more slowly on chromatograms. The amounts of cytokinin in the solutions were associated with root formation. Stems soon died unless their hypocotyls formed roots, but the primary leaves survived without roots forming provided a callus formed on the petiole. Hence adventitious roots, or callus tissues, may have produced cytokinins that replaced those produced by the original roots, found in sap exuded from the stem stumps, and were essential for survival of the stems and leaves.