Showing papers on "Zeatin published in 1973"

Regulators of Cell Division in Plant Tissues

Abstract: [3H]Zeatin was supplied through the transpiration stream to radish (Raphanus sativus L.) seedlings with roots excised. Formation of dihydrozeatin was not detected but numerous other metabolites were formed, including adenine, adenosine, AMP, zeatin riboside and zeatin riboside-5′-monophosphate. However, in labelled seedlings which had been left in water for 15 h, an unknown compound (raphanatin) was the dominant metabolite and accounted for about 25% of the total radioactivity extracted. A procedure for the isolation of this metabolite was devised and yielded 70 μg from 1600 seedlings. Raphanatin was characterized by mass and ultraviolet spectra and has been identified as 7-glucosylzeatin. It is an active and very stable metabolite which was located mainly in the cotyledon laminae and may be a storage form of the hormone. In contrast, labelled nucleotides, the other major metabolites of zeatin, were largely confined to the hypocotyls and petioles. Zeatin riboside-5′-monophosphate was the dominant metabolite in hypocotyls of de-rooted seedlings supplied with zeatin for 0.5–2 h. The majority of the radioactivity in the xylem sap was due to zeatin, but about 10% was present as zeatin riboside; nucleotides accounted for less than 10% of the radioactivity and labelled raphanatin was not detected.

Cytokinins in Populus×robusta: Changes during Chilling and Bud Burst

Abstract: Cytokinin levels in sap and vegetative buds of Populus×robusta Schneid have been determined during chilling and bud burst. From non-detectable levels in December and January, parallel increases in cytokinin levels occur in sap and buds during February and March, both in material from the field and that held at 2°C in the dark. The maximum in the sap occurs two weeks prior to natural bud burst, and 3 weeks, prior to the maximum attained in the buds. Excised twigs, forced to bud burst, show a similar pattern. The role of roots as a possible source of cytokinins is discussed. Partition chromatography on Sephadex LH-20 indicates that at least 5 cytokinins are present in buds, two of which have similar elution volumes to zeatin and zeatin riboside-The main activity in the sap is confined to a zeatin riboside-like component.

Hormonal Control of Differentiation of Shoots, Roots and Embryos in Leaf and Stem Cultures of Petunia inflata and Petunia hybrida

Abstract: Factors influencing adventitious bud and root development, callus induction and embryogenesis were investigated in stem and leaf cultures of Petunia inflata R. E. Fries and Petunia hybrida cv. Cascade and cv. Rose du ciel grown on a synthetic nutrient medium. Indoleacetic acid caused limited callus development and root formation whereas naphthaleneacetic acid Induced abundant roots. 2,4-Dichlorophenoxyacetic acid promoted callus growth and differentiation of embryos which eventually developed into plantlets. Cytokinins such as benzyladenine, zeatin and kinetin induced bud development. A combination of auxins and cytokinins caused an interaction which was manifested in altered morphogenetic response. Thus 2,4-dichlorophenoxyacetic acid in conjunction with benzyladenine caused suppression of bud development and retarded differentiation of embryos. Likewise, when benzyladenine was used with indoleacetic acid root development was totally inhibited and abundant buds were produced.

Seed Dormancy in Acer CHANGES IN ENDOGENOUS CYTOKININS, GIBBERELLINS AND GERMINATION INHIBITORS DURING THE BREAKING OF DORMANCY IN ACER SACCHARUM MARSH

Abstract: The present studies on changes in the levels of cytokinins, gibberellins, and germination inhibitors during stratification of Acer saccharum seeds suggest that the breaking of dormancy is a phasic process Stratification at 5 °C led to a marked increase in the butanol-soluble cytokinins after 20 d Further chilling resulted in a loss of cytokinin The majority of the detectable cytokinin activity co-chromatographed with zeatin Similarly, at day 40, acidic gibberellin-like substances increased and declined with further chilling A loss of acidic germination inhibitors was also detected during stratification The acidic fraction was shown to contain abscisic acid (ABA) by its behaviour on GLC and isomerization with ultra-violet light Determinations of endogenous levels of ABA by combined GLC and isotope dilution methods indicated a loss of 97-9 per cent ABA during stratification The data suggest that the breaking of seed dormancy at low temperature involves the initiation of an ordered sequence of events that include the changes in growth hormones necessary to determine the course of development for the removal of dormancy

Biosynthesis of Cytokinins in Cytokinin-Autotrophic Tobacco Callus

Abstract: A cytokinin-autotrophic strain of tobacco callus contained cytokinin-active compounds with chromatographic mobilities on Sephadex LH-20 corresponding to ribosylzeatin, zeatin, and 6-Δ2-isopentenylaminopurine. Zeatin, the apparent major cytokinin, was estimated to be present at a concentration of 10-4 μmol/kg of tissue. Cytokinin-autotrophic callus supplied with [14C]adenine produced radioactive components with the same chromatographic properties as zeatin and 6-Δ2-isopentenylaminopurine. These components were not obtained from cytokinin-dependent tissue supplied with [14C]adenine in the same manner.

Isolation of cis-Zeatin from Corynebacterium fascians Cultures

Abstract: Three cytokinin-active constituents have been isolated from the culture medium of Corynebacterium fascians, a plant pathogen causing fasciation. One constituent is now identified as cis-zeatin [6-(4-hydroxy-3-methyl-cis-2-butenylamino)purine]. It represents the first unequivocal demonstration of the production of a zeatin isomer by a bacterial species. Another constituent was identified earlier as 6-(3-methyl-2-butenyl-amino)purine. The third constituent, distinct, on Sephadex LH-20 column chromatography, from the above two and their ribosides, has not yet been identified.

Cytokinins in Populus x robusta Schneid: A complex in leaves.

Abstract: At least seven cytokinins have been detected in mature leaves of Populus x robusta Schneid after chromatography on Sephadex LH-20. Two of these have similar elution volumes to zeatin and zeatin riboside. A third appears to be a cytokinin glucoside. A fourth is a new, unidentified cytokinin, susceptible to mild oxidation, and yielding two cytokinin active products after acid hydrolysis. This cytokinin complex has been found in fully expanded leaves, a tissue in which cell division is completed.

Effects of different cytokinins on the senescence of detached oat leaves.

Abstract: Senescence is delayed (chlorophyll retained) in oat leaf sections by kinetin and benzyladenine, but not by the natural cytokinins, zeatin and isopentenyladenine.

The formation of adventitious organs. i. cytokinin-induced formation of leaves and shoots in callus cultures of populus nigra l. ‘italica‘*

Abstract: SUMMARY One- to four-year-old callus cultures of the Lombardy poplar (Populus nigra L. ‘Italica‘) are able to form roots and leaves or shoots. There may be single leaves, small buds, elongating shoots, or a combination of these organs. Of the four cytokinins used to stimulate organ formation, zeatin was the most active, stimulating shoot formation at a concentration as low as 10–8 M. The highest zeatin and BA concentrations (10–5 M) stimulated leaf formation, but fewer elongated shoots were formed than at a lower cytokinin concentration. 2,4-D was inhibitory to organ formation, even in low concentrations that stimulated callus growth (0.05–0.1 mg/1). This 2,4-D-inhibition is discussed in relation to the suppression of tissue differentiation.

The Metabolism of Hormones during Seed Germination and Release from Dormancy: III. The Effects and Metabolism of Zeatin in Dormant and Nondormant Ash Embryos.

Abstract: Zeatin and zeatin-9, beta-ribonucleoside enhance the germination of dormant ash embryos. While the first macroscopic signs of germination appear only after about 72 hours, 12 hours of exposure to 50 mum zeatin is as effective as continuous incubation. There must be barriers against transport out of the embryos since 8-(14)C-zeatin and its metabolites, zeatin-9, beta-ribonucleoside, the 5'-mono and the suspected di- and triphosphates, accumulate against a concentration gradient. Zeatin ribonucleoside is about as effective as zeatin in enhancing embryo germination, yet the internal 8-(14)C-zeatin level is lower by a factor of about 50 when the ribonucleoside is fed. The physiological effects of zeatin and abscisic acid on the germination of ash embryos are antagonistic. There is, however, no evidence that abscisic acid has a significant effect on 8-(14)C-zeatin uptake or conversions.

The Effect of Cytokinins and Auxins on Anthocyanin Accumulation in Green Manzanillo Olives

Abstract: A comparison was made of the composition and some metabolic changes in Manzanillo olives at different stages of maturation. The effects of cytokinins and auxins on maturation and anthocyanin accumulation in green-picked fruit were determined. Kinetin, benzyl adenine, and zeatin at concentrations not exceeding 50 parts/106 caused a marked enhancement in anthocyanin accumulation without affecting fruit maturation. NAA and 2,4,5-TP at con centrations up to 200 and 300 parts/106 respectively, also caused anthocyanin accumulation but apparently as part of a general ripening induction.

Effects of Cytokinins on the Nucleic Acids of Tobacco Pith

Abstract: Cylinders of pith of Nicotiana tabacum var Wis 38 were aseptically isolated and grown on a mineral-sucrose medium in the presence and absence of either kinetin or zeatin On medium containing kinetin (5 x 10-6 M) the increase in the residual dry weight of cylinders was greater than that on control medium after 2 d culture and this was maintained at 5 d At 2, 5, and 7 d there were increments in the DNA and RNA levels of cylinders due to kinetin treatment and these increased progressively A double-labelling method coupled with acrylamide gel electrophoresis was used to study the effects of kinetin at 5 X 10 " M and zeatin at 10~6 M on the incorporation of radioactive pre cursors into the RNA of cylinders given a 4-h label pulse No effects of zeatin were observed after 1 d nor of kinetin at 2 d but after 4 d zeatin stimulated incorporation into ribosomal, transfer and poly-disperse RNA and kinetin did likewise after 5 d Incorporation measured at 7 d was reduced in cylinders from which kinetin had been removed at 5 d compared to those to which it had been supplied continuously Scans at 260 nm of the electrophoretic fractionations of RNA after 2,5,7, and 9 d of culture showed that both in the absence and in the presence of kinetin the proportion of 4S RNA increased from about 20 per cent to over 50 per cent of the total between 2 and 5 d of culture and after 5 d the ribosomal RNA gave aberrant scans apparently indicative of degradation These aberrant scans persisted in RNA extracted after 27 d culture in both the presence and absence of kinetin

Studies on Growth of Japanese Pear Fruits

Abstract: Immature fruits of Japanese pear, Pyrus serotina, were picked and homogenized with 70% ethanol. The homogenate was extracted with 70% ethanol three times and filtrated. The filtrate was concentrated, the residue adjusted to pH 8.4 with 1N NaOH and then extracted with n-butanol. The butanol phase was evaporated and aqueous extract of the residue was added to a Dowex-50(H+ form) column and eluted with water, 1N NH4OH and 5N NH4OH successively. Cytokinin activities in the three fractions were tested by tobacco(Wisconsin No. 38) pith callus assay. Cytokinin activities were detected in both 1N and 5N NH4OH fractions, but not in the water. Based on these results, the NH4OH fractions (Am-fraction) were combined and analysed by microcrystalline cellulose thin layer and gas liquid chromatographies. The fraction separated by TLC for the bioassay of cytokinin revealed activities at Rf values 0.5 and 0.7. Analyses of TMS derivative of Am-fraction by GLC gave four peaks. Mixture of the TMS derivative with that of authentic zeatin analyzed on GLC revealed that peak 2 coincides with zeatin, and peak 1 was considered to be dihydrozeatin.