Showing papers on "Zeatin published in 1979"

The biosynthesis of cytokinins in crown-gall tissue of Vinca rosea.

Abstract: The crown-gall tissue of Vinca rosea converts labelled adenine into cytokinins. The principal initial products appear to be ribosylzeatin phosphates; zeatin and ribosylzeatin are also produced in appreciable quantities. The efficiency of conversion of adenine into cytokinins suggests a pathway of synthesis independent of turnover of tRNA. Isopentenyl adenine or its derivatives do not appear to be intermediates in the conversion of adenine to zeatin compounds. Cytokinins in V. rosea turnover rapidly and further metabolism of zeatin derivatives seems to result in their conversion into glucosides which are the main cytokinin active compounds in the tissue.

Hormones in Plants Bearing Actinomycete Nodules

Abstract: Bioassay of chromatographic fractions of extracts of the perennial nodules of Alnus glutinosa indicates that the levels of cytokinins and gibberellin-like substances undergo seasonal fluctuations and that the highest levels occur prior to the recommencement of nitrogen fixation in the spring. A comparison of the cytokinin activity of nodulated alders and nonnodulated alders fertilized with nitrogen showed that the only consistent difference between the two sets of plants was the higher percentage of cytokinin activity in the leaves of nonnodulated plants, which was probably related to their consistently better root development. Most of the nodule cytokinin activity occurred as a glucoside of zeatin, suggesting that nodule cells normally store rather than export any excess of cytokinin.

Mass spectrometric analysis of cytokinins in plant tissues. II—Quantitation of cytokinins in Zea mays kernels using deuterium labelled standards

Abstract: Deuterium labelled analogues of the major zeatin derived cytokinins have been synthesized to serve as internal standards for mass spectrometric quantitation. A procedure for the isolation, high performance liquid chromatographic purification and direct probe mass spectrometric analysis of these cytokinins has been devised and applied to the analysis of Zea mays kernels where the levels of endogenous zeatin, zeatin-9β-riboside and zeatin-9β-glucoside were estimated by isotope dilution. Additionally, the deuterated compounds have been utilized to confirm the identity of the in vitro enzymic glucosylation products of zeatin.

Influence of Several Growth Regulators and Amino Acids on in vitro Organogenesis of Torenia fournieri Lind.

Abstract: The effects of several growth regulators and amino acids on in vitro organogenesis of Torenia fournieri Lind. were determined using internodal segments. Treatment with 2,4-D1 resulted in nodular callus formation, while NAA and IAA induced roots constantly but much less frequently shoot buds. Individually BA, zeatin, and 4-PU induced bud formation, but these shoot buds did not develop further. Formation of buds by cytokinin was influenced by a simultaneous application of NAA or 2,4-D, but not of IAA, its degree being reduced when BA was simultaneously applied with NAA or 2,4-D. When zeatin or kinetin was added with NAA, numerous roots were induced. The effects of various L-amino acids on in vitro organogenesis were also investigated using the defined medium in which KN03 was a principal source of nitrogen. The formation of buds was considerably stimulated by alanine and asparagine, and slightly by glutamic acid in the medium containing both NAA and BA, in which bud formation was easily induced. On the other hand, all amino acids except for glutamic acid and aspartic acid inhibited root formation in this medium. Root formation was greatly stimulated by proline, alanine, glutamine, glutamic acid, and aspartic acid, and slightly by arginine and tryptophan in the medium containing NAA but no BA. Glutamic acid and aspartic acid also enhanced bud formation in this medium.

Cytokinin biosynthesis in roots of corn.

Abstract: Removal of the quiescent center (QC) from the root apex of maize (Zea mays L, cv Kelvedon 33) initiates a set of events which culiminate in the regeneration of an intact apex with a newly formed QC Concomitant with the formation of a new QC is a marked reduction in extractable cytokinins in the tissue of the proximal meristem Replacing the excised QC with a Dowex (acidic cation-exchange resin) bead affects both root growth and QC regeneration Root growth is inhibited by "plain" Dowex beads and Dowex beads treated with zeatin; this inhibition is reversed if the beads have been treated with CaCl2 (±zeatin) Dowex beads treated with zeatin delay the formation of a new QC; this effect is the same whether or not the beads also contain CaCl2 The results of this investigation support the notions that cytokinin biosynthesis in roots is a result of activities of both the QC and the proximal meristem, and that cytokinins, at least if supplied exogenously, can play a role in root morphogenesis by delaying the regeneration of the QC

Origin of Cytokinins Transported in the Phloem

Abstract: The origin of cytokinins in the exudate of Yucca inflorescences has been studied. A decrease in nucleotides of both isopenlenyladenine and zeatin was observed after removal of leaves as measured over a three day period. Removal of roots and the greater part of the rhizome resulted in a transient decline of isopenlenyladenincand zeatin nucleotides during 24 h. after which an increase took place. The results strongly indicate that the latter increase is due to cytokinins originating from the leaves.

The effect of stratification on the endogenous levels of gibberellins and cytokinins in seeds of douglas‐fir (Pseudotsuga menziesii (Mirb.) Franco) and sugar pine (Pinus lambertiana Dougl.)

Abstract: Seeds of Douglas-fir and sugar pine which had been exposed to various periods of moist chilling (stratification) were extracted and bioassayed for gibberellin and cytokinin activity. In Douglas-fir a peak of gibberellin activity increased progressively during stratification and was seven times higher after 7 weeks, but declined subsequently. No change in the level of cytokinin activity was observed during stratification. However, a slight increase (1.7-fold) occurred in stratified seeds placed at 22°C for 3 days. In sugar pine a high level of gibberellin activity, approximately 20-fold higher than in unstratified controls, was present in extracts of seeds which had been stratified for 8 weeks. After 10 weeks of stratification cytokinin levels had increased approximately 200-fold. Four cytokinin-like substances were detected in seeds. Three of the substances are similar in their chromatographic properties to zeatin glucoside, zeatin riboside and zeatin, respectively. Both gibberellin and cytokinin activity declined rapidly after reaching maximum levels. In seeds with the coats removed, germination was rapid and complete in the absence of stratification. Prior to radicle emergence in coatless seeds cytokinin activity increased to a maximum (approximately a 1-7-fold increase) within 24 h. Significant levels of gibberellin-like substances were present after 8 h. Gibberellin activity could not be detected in coatless seeds which were imbibed in AMO-1618, and germination was inhibited significantly.

Cytokinins and in vitro development of Phaseolus coccineus embryos

Abstract: Phaseolus coccineus embryos at the heartshaped and the middle cotyledonary stages were cultured in vitro on media added with different concentrations of zeatin (Z) or zeatin riboside (Zr). Growth of early embryos was clearly favored by concentrations of Z from 10-8 M to 10-5 M, lower concentrations having no effect. Zr also promoted in vitro growth of early embryos, but in concentrations from 10-12 M to 10-10 M, higher concentrations being inhibitory. More developed embryos were scarcely sensitive to the presence in the culture medium of either Z or Zr at any concentration.

Cytokinin Activity in Lupinus albus L: IV. Distribution in Seeds

Abstract: Endogenous levels of cytokinin activity were examined in Lupinus albus L. seed at intervals of 2 weeks after anthesis using the soybean callus bioassay. High levels of cytokinin activity per gram seed material were present in the seeds at 2, 4, and 6 weeks after anthesis. The cytokinin activity per gram seed material was low at 8 and 10 weeks after anthesis. Cytokinin activity associated with each seed was greatest at 6 weeks after anthesis. The majority of the activity in the seeds at 4, 6, and 8 weeks after anthesis was in the endosperm. Cytokinin activity was also detected in the testas and embryos at 4, 6, 8, and 10 weeks, and the suspensors at 4 weeks. Column chromatography of extracts of the different seed fractions on Sephadex LH-20 indicated that the cytokinins present coeluted with zeatin, zeatin riboside, and the glucoside cytokinins. It is suggested that cytokinins are accumulated in the seeds and are stored in the endosperm mainly in the form of ribosides and glucosides of zeatin. The reduction in cytokinin activity in the seed coincides with the reduction in endosperm volume and embryo growth and suggests that these compounds are utilized during the course of seed maturation.

Regeneration of leaf explants of Anthurium andraeanum Lind. in vitro.

Abstract: Leaf explants were cultured on a basic nutrient agar medium to which were added growth substances (adenine, benzyladenine, kinetin, 2-iP [isopentenyladenine], zeatin or 2,4-D) and NH4NO3, (NH4)2SO4 or NaNO3 in various concentrations. The effects of using the surfactant Tween 20 during leaf sterilization and of growing explants in light and/or darkness for 20 weeks were also investigated. There was a strong positive correlation between callus formation and shoot regeneration. Regeneration was optimal under the following conditions: addition of 0.25-1.00 ml/litre Tween 20 during leaf sterilization, adding a growth substance (adenine 0.1 mg/litre, zeatin 1 mg/litre, or 2,4-D 0.08 mg/litre), culture during 16 weeks in darkness followed by 4 weeks of light, and including 206 mg/litre NH4NO3 in the medium. The promoting effect of low levels of NH4NO3 on shoot regeneration in callus was caused by the NH4+ ion and not by the NO3- ion. (Abstract retrieved from CAB Abstracts by CABI’s permission)

Secondary metabolism in tissue cultures of theobroma cacao

Abstract: SUMMARY A synthetic medium was developed for the routine subculture of callus and cell suspensions of cocoa. All growth hormones and the coconut milk (CM) supplement of previous media were replaced by indole butyric acid (IBA) and zeatin, at concentrations of 1 mg 1-1 IBA and 005 mg 1-1 zeatin for callus and 10 mg 1-1 IBA and 0-5 mg 1-1 zeatin for cell suspension cultures. During the exponential phase of the growth cycle on this medium, the total phenolics in the callus and cell suspensions declined but then increased at onset of the stationary phase and finally declined again with cell senescence. The flavonoid compositions of the callus and cell suspension were similar and much less varied than that of the original intact cotyledon. Both tissue cultures contained epicatechin, leucocyanidins, caffeic and coumaric acids, all of which are thought to act as flavour precursors when in the intact fermented cotyledon. The methylated purines, theobromine and caffeine, could not be detected in the tissue cultures even in the presence of high nitrate levels in the medium. When precursors of theobromine synthesis such as xanthine, hypoxanthine and 7-methyl-xanthosine, were fed to the cells, theobromine was formed only when the cells were incubated with 7-methyl-xanthosine and a methyl donor, methionine, suggesting that part of the biosynthetic route to theobromine synthesis is still functional in the tissue culture.

Investigations into the Possibility that Potato Buds Synthesize Cytokinins

Abstract: In an attempt to determine whether potato buds synthesize cytokinins, tubers and potato pieces were subjected to conditions which both retard and accelerate bud development. Cytokinin activity was recorded in the tubers and sprouts under different experimental conditions. Most of the com pounds detected had chromatographic properties resembling those of zeatin, zeatin riboside, and zeatin glucoside. It would appear as if the buds and sprouts do not synthesize cytokinins. Initial bud growth may be dependent on the supply of cytokinins within the mother tubers, while the increase in the sprouts could be the result of root development at their basal ends.

Influence of Cytokinins and Temperature on Development of Asparagus plumosus Shoot Tips in vitro

Abstract: Lateral shoot tips from young shoots of Asparagus setaceus (Kunth) Jessop (syn. A. plumosus Baker) were grown on a modified Murashige and Skoog medium. PBA was the most effective cytokinin for growth and development of Asparagus plumosus shoot tips. The optimal range of PBA was between 0.02 and 2 mg/1. Zeatin was less effective, and kinetin, BA and 2iP were poor as cytokinins for A. plumosus. The optimal temperature for growth and development was 21°C. There was interaction between the temperature and the PBA concentration. With increasing temperature from 17 to 24°C the need for PBA increased from 0.2 to 2 mg/1.