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.

Growth-promoting Sphingomonas paucimobilis ZJSH1 associated with Dendrobium officinale through phytohormone production and nitrogen fixation.

Abstract: Summary Growth-promoting Sphingomonas paucimobilis ZJSH1, associated with Dendrobium officinale, a traditional Chinese medicinal plant, was characterized. At 90 days post-inoculation, strain ZJSH1 significantly promoted the growth of D. officinale seedlings, with increases of stems by 8.6% and fresh weight by 7.5%. Interestingly, the polysaccharide content extracted from the inoculated seedlings was 0.6% higher than that of the control. Similar growth promotion was observed with the transplants inoculated with strain ZJSH1. The mechanism of growth promotion was attributed to a combination of phytohormones and nitrogen fixation. Strain ZJSH1 was found using the Kjeldahl method to have a nitrogen fixation activity of 1.15 mg l−1, which was confirmed by sequencing of the nifH gene. Using high-performance liquid chromatography-mass spectrometry, strain ZJSH1 was found to produce various phytohormones, including salicylic acid (SA), indole-3-acetic acid (IAA), Zeatin and abscisic acid (ABA). The growth curve showed that strain ZJSH1 grew well in the seedlings, especially in the roots. Accordingly, much higher contents of SA, ABA, IAA and c-ZR were detected in the inoculated seedlings, which may play roles as both phytohormones and ‘Systemic Acquired Resistance’ drivers. Nitrogen fixation and secretion of plant growth regulators (SA, IAA, Zeatin and ABA) endow S. paucimobilis ZJSH1 with growth-promoting properties, which provides a potential for application in the commercial growth of D. officinale.

Cytokinins: synthesis and biological activity of geometric and position isomers of zeatin.

Abstract: Geometric and position isomers of zeatin and of ribosylzeatin and other compounds closely related to zeatin have been tested in the tobacco (Nicotiana tabacum var. Wisconsin No. 38) bioassay. None was more active than zeatin itself. There was a much greater difference in activity (> 50-fold) between trans- and cis-zeatin than between trans-isozeatin [6-(4-hydroxy-2-methyl-trans-2-butenylamino) purine] and cis-isozeatin [6-(4-hydroxy-2-methyl-cis-2-butenylamino) purine], the latter being less active than cis-zeatin and trans-isozeatin. Higher concentrations were required for equivalent callus growth stimulated by the 9-ribosyl derivatives, which followed an order of decreasing activity: ribosyl-trans-zeatin > ribosyl-cis-zeatin > ribosyl-trans-isozeatin > ribosyl-cis-isozeatin, corresponding roughly to that of the bases. The effect of side chain, double bond saturation was to diminish the activity, and in the dihydro series the shift of the methyl group from the 3- to the 2-position in going from dihydrozeatin to dihydroisozeatin [6-(4-hydroxy-2-methylbutylamino) purine] resulted in a 70-fold decrease in activity. cis-Norzeatin [6-(4-hydroxy-cis-2-butenylamino) purine], which was less than one-fifth as active as cis-zeatin, showed the effect of complete removal of the side chain methyl group, and cyclic-norzeatin [6-(3,6-dihydro-1,2-oxazin-2-yl) purine] was about 1/100 as active as cis-norzeatin. These findings delineate completely the effect on the cytokinin activity of zeatin of variation in side chain geometry, presence and position of the methyl substituent, presence and geometry of hydroxyl substitution, presence of the double bond, and of side chain cyclization.

Arrest of somatic embryo development in grapevine: histological characterization and the effect of ABA, BAP and zeatin in stimulating plantlet development

Abstract: In an effort to understand the causes of arrest of somatic embryo development, generally observed in grapevine (Vitis sp.), histological studies were undertaken, using two cultivars (CH76 and 41B) which differ in their ability to develop into plants. Embryos with a high conversion rate (70%; CH76) formed a well-structured and functional shoot apex between two thread-like cotyledons. In contrast, embryos with a low conversion rate (10%; 41B) formed a normal root apex but lacked a well-structured shoot apex and developed a wide range of aberrant forms in the intercotyledonary area: uncontrolled cellular proliferation, formation of adventitious buds, over-growth of cotyledonary or leaf meristems. ABA increased the conversion rate of 41B embryos from 10% to 20%, but failed to improve embryo morphology. Zeatin and BAP promoted growth of 41B somatic embryos, but generated a high level of abnormalities and failed to improve conversion rate. Applied in combination with ABA, these PGRs increased the frequency of cotyledonary embryos, but decreased the conversion rate.

Efficient in vitro regeneration systems for Vaccinium species

Abstract: Efficient protocols for shoot regeneration from leaf explants suitable for micropropagation as well as for the development of transgenic plants were developed for blueberry (Vaccinium corymbosum) and lingonberry (Vaccinium vitis-idaea) cultivars. Nodal segments were used to initiate in vitro shoot cultures of lingonberry cultivar ‘Red Pearl’ and southern highbush blueberry cultivar ‘Ozarkblue’. In order to develop an optimized regeneration procedure, different types and concentrations of plant growth regulators were tested to induce adventitious shoot regeneration on excised leaves from micropropagated shoots of both cultivars. The effect on percentage regeneration and number of shoots per explant was investigated. Results indicated that zeatin was superior to TDZ and meta-topolin in promoting adventitious shoot formation. A concentration of 20 μM zeatin was most effective in promoting shoot regeneration in both cultivars, in case of ‘Red Pearl’ along with 1 μM NAA. Shoots were either allowed to root in vitro on medium containing IBA or NAA or ex vitro in a fog tunnel. IBA was superior to NAA for induction of root development in vitro in both Vaccinium cultivars. Ex vitro rooting under high humidity was tested with cuttings from mature field-grown plants, from acclimatized tissue culture derived plants and with unrooted in vitro proliferated shoots planted directly. It was found that in vitro shoots rooted better under fog than cuttings from the other plant sources and rooting was equivalent to that achieved in vitro.

Cytokinin biochemistry in relation to leaf senescence. VII. Endogenous cytokinin levels and exogenous applications of cytokinins in relation to sequential leaf senescence of tobacco

Abstract: The cytokinin complex in tobacco leaves of various maturities was characterized by radioimmunoassay and mass spectrometry. Zeatin was the major base, whereas zeatin riboside was identified as the main riboside. in leaves of all maturities studied. Relative to upper younger leaves, the basal yellow leaves had reduced levels of both cytokinin bases and ribosides. Exogenous applications of dihydrozeatin and zeatin to detached tobacco leaves in amounts sufficient to delay senescence, elevated cytokinin base and riboside levels 2–5 fold. Presenescent and senescent leaves of intact plants showed quantitatively similar changes in cytokinin content. which therefore appear to be of significance in control of senescence. When supplied exogenously, the principal cytokinin bases found to occur in tobacco leaves (zeatin and dihydrozeatin) were markedly more effective than auxins and gibberellic acid in retarding senescence. Localised application of cytokinins to leaf blades of detopped plants was much less effective than application to intact plants. The cytokinin induced senescence retardation in tobacco leaves was independent of effects on directed metabolite transport. Evidence that endogenous levels of active cytokinins in intact tobacco leaves are involved in control of sequential leaf senescence is discussed.