Zeatin

About: Zeatin is a research topic. Over the lifetime, 2467 publications have been published within this topic receiving 64092 citations. The topic is also known as: Zeatin & (E/Z)-zeatin.

Regulators of cell division in plant tissues. XXX. Cytokinin metabolism in relation to radish cotyledon expansion and senescence

Abstract: Kinetic studies of formation of glucosides of 6-benzylaminopurine (BAP) in excised radish cotyledons indicated that the 3-, 7-, and 9-glucosides (N-glucosides) were each formed directly from BAP. The 7- and 9-glucosides of BAP and the 7-glucoside of zeatin exhibited great stability in the cotyledons, but the 3-glucoside was converted to free BAP and to the 7- and 9-glucosides of BAP. When3H-labeled zeatin was supplied to developed cotyledons, at high concentrations (100 μM), 7-glucosylzeatin was the principal metabolite, but an appreciable proportion of the extracted3H was due to O-glucosylzeatin. In immature cotyledons, as used in the radish cotyledon cytokinin bioassay, this O-glucoside was shown to be converted into zeatin 7-glucoside probably via free zeatin. Metabolism of BAP and zeatin in radish cotyledons was studied in relation to cytokinin-induced cotyledon expansion. Cytokinin N-glucosides were not metabolites responsible for the observed cytokinin-induced expansion, and were not detoxification products, or deactivation products formation of which was coupled with cytokinin action. However, the free base, its riboside, and nucleotide were possible active forms of BAP associated with cotyledon expansion. The possible significance of cytokinin N-glucosides is discussed. Senescent and nonsenescent cotyledons differed in their metabolism of BAP, zeatin, and zeatin riboside. Senescence was associated principally with a reduction in ability to form 7-glucosylzeatin, enhanced metabolism to adenine derivatives, and an inability to form appreciable amounts of 3-glucosyl-BAP. A two-dimensional thin layer chromatography (TLC) system, based on adjoining layers of cellulose and silica gel, for separating zeatin metabolites is described. This does not completely separate zeatin and zeatin riboside from the corresponding dihydro-compounds. A reversed phase TLC method for achieving these separations is also reported.

Cytokinins and Differentiation Processes in Mercurialis annua: Genetic Regulation, Relations with Auxins, Indoleacetic Acid Oxidases, and Sexual Expression Patterns

Abstract: Cytokinins in apices of eight isogenic lines of Mercurialis annua were compared (high performance liquid chromatography-gas chromatography mass spectroscopy-computer system). These apices develop normal staminate or pistillate differentiation processes (sex series lines) or empty (sterile), semiempty (semisterile), and full anthers (restored fertile male) in the sterility series in which a pistillate line was constructed. Both series developed two different cytokinin pathways: trans-cytokinins characterized the sex series, whereas the cis pathway characterized the sterility series. Drastic changes in the trans pathway (0/250 nanograms trans-zeatin and 166/0 nanograms zeatin nucleotide) induced staminate/pistillate differentiations. Less drastic quantitative changes in the cis pathway induced sterility or restored fertility compared to normal fertile anthers (192 or 669 nanograms/traces). The action of the complete cis-pathway was morphologically effective in the sterility series when the ratio of cis to trans pathways was 1:2 or 1:1 instead of 1:3. A final diagram shows the action of each sex or sterility allele on the enzymes controlling specific metabolites in both pathways. The discussion provides insights on the regulation of cytokinin-auxin balances specific for each kind of reproductive differentiation.

Optimized shoot regeneration for Indian soybean: the influence of exogenous polyamines

Abstract: A simple and efficient regeneration protocol was established for soybean [Glycine max (L.) Merrill]. Cotyledonary node explants from 7-day-old in vitro seedlings were used as explants. The effect of different plant growth regulators [N 6 –benzyladenine (BA), kinetin (KT), thidiazuron (TDZ), gibberellic acid (GA3), zeatin riboside (ZTR), indole-3-acetic acid (IAA), and indole-3-butyric acid (IBA)] along with polyamines (Spermidine, spermine, and putrescine) were investigated at different stages of regeneration using direct organogenesis system. Exogenous spermidine (137.69 μM) in shoot induction medium containing optimal BA concentration (2.22 μM) induced maximum number of shoots (39.02 shoots/explant) compared to BA (2.22 μM) alone. Regenerated shoots elongated well in shoot elongation medium containing GA3 (1.45 μM) and spermine (74.13 μM), and developed profuse roots in root induction medium containing putrescine (62.08 μM). Rooted plantlets were successfully hardened and acclimatized with a survival rate of 92 %. The amenability of the standardized protocol using cultivar PK 416 was tested on four more Indian soybean cultivars JS 90–41, Hara soy, Co1, and Co2 of which PK 416 was found to be the best responding cultivar, with a maximum of 96.94 % shoot induction.