Endogenous cytokinins in vegetative shoots of peas

In G2 peas senescence only takes place in long days. In order to determine the role of cytokinins in this process the endogenous cytokinins from vegetative shoots of G2 peas were characterized using gas chromatography-mass spectroscopy following purification by HPLC. Cytokinins were extracted and purified with and without the addition of ¹⁵N labelled internal standards of several cytokinins to estimate cytokin content by isotope dilution in the mass spectra. Samples without internal standards were bioassayed after HPLC. Bioassays showed the presence of zeatin, zeatin riboside and zeatin-0-glucoside. The presence of zeatin was confirmed by its mass spectrum of its permethylated derivative. Tentative identification of zeatin riboside, zeatin-0-glucoside, dihydrozeatin, and dihydrozeatin-0-glucoside was obtained by the coincidence of the major ion for the permethylated natural and ¹⁵N labelled internal standards on GC-MS, and the similar coincidence of ions for permethylated zeatin riboside-0-glucoside by direct probe MS. There was no indication of the presence of significant quantities of zeatin-7-glucoside or zeatin-9-glucoside. The amounts in the tissue ranged from 200–1000 ng/kg fresh weight for each cytokinin and about 2–4 g/kg fresh weight for total cytokinins. There was no apparent difference in the levels in mature but pre-senescent shoots grown in long days and short days indicating that apical senesecence in G2 peas does not appear to be induced by a decline in cytokinin level in the shoots.Cytokinin abbreviations CK Cytokinin - Z trans zeatin - [9R]Z t-zeatin riboside - [9R-5P] Z t-zeatin riboside-5-monophosphate - (OG)Z t-zeatin-0-glucoside - (OG)[9R]Z t-zeatin riboside-0-glucoside - [7Z]G t-zeatin-7-glucoside - [9G]Z t-zeatin-9-glucoside - (diH)Z dihydrozeatin - (diH)[9R]Z dihydrozeatin riboside - iP N6(²-isopentenyl) adenine - [9R]iP N6(²-isopentenyl) adenosine Work performed while PJD was on leave at the University College of Wales at Aberystwyth.     

The biological activity of cytokinin derivatives in the soybean callus bioassay

The effect of 28 natural and synthetic cytokinins, including cytokinin nucleotides, the growth of soybean cotyledonary callus was investigated. Generally the nucleosides and nucleotides gave a slightly better response than their respective free bases. The differences in response were, however, not significant and there is a distinct possibility that rapid interconversions between these three types of cytokinin occur within the tissue. The O-glucosides of Z and ZR were the most active. Glucosylation in the 3, 7 and 9 positions reduced activity. In the case of BA-derivatives the order of activity of the N-glucosides was 3G > 9G > 7G. Since iso-pentenyl derivatives had little activity they may be very difficult to detect using the soybean callus bioassay.Abbreviations Z zeatin - DHZ dihydrozeatin - IP iso-pentenyladenine - BA benzyladenine - K Kinetin - R riboside - MP monophosphate - OG 0-glucoside - 3G 3-glucoside - 7G 7-glucoside - 9G 9-glucoside - GC-MS gas chromatography—mass spectrometry     

Transport and metabolism of [3H]iso-pentenyladenine following application to the tips of intact and decapitated tap roots of Pinus pinea

[³H]iso-Pentenyladenine ([³H]iP) was fed for 24 h to the tips of intact and root tip-decapitated Pinus pinea seedlings. Twelve and 24 h after application to the roots of intact plants most of the applied radioactivity (±60%) was transported to the shoot. Root tip removal increased transport of the applied radioactivity to the shoot, but the overall pattern of distribution of radioactivity in the seedling did not change. Large amounts of radioactivity were recovered from the elongation zone of the root. Some radioactivity also accumulated in the older part of the root with well-developed lateral roots. When [³H]iP was applied one day after decapitation, no significant changes in the pattern of radioactivity distribution were found between the intact and decapitated root systems. However, when applied 7 days after decapitation there was a significant increase of radioactivity in the region of the root where lateral roots were emerging. HPLC separation of extracts from the different root sections showed that [³H]iP was extensively metabolized in the root. Six peaks of radioactivity, which co-chromatographed with authentic cytokinin standards, were detected.Abbreviations ABA abscisic acid - ADE adenine - IAA indole-acetic acid - iP iso-pentenyladenine - HPLC high performance liquid chromatography - [OG]DHZ O-glycosyldihydrozeatin - [9R-MP]DHZ ribosyldihydrozeatin monophosphate - [9G]iP iso-pentenyladenine-9-glucoside - [9R]Z ribosylzeatin - [9R]iP iso-pentenyladenosine - TLC thin layer chromatography     

Zeatin-9-glucoside,a major endogenous cytokinin of Vinca rosea L. crown gall tissue

Cultured crown gall tissue of Vinca rosea L. was found to contain, in addition to the previously reported cytokinins zeatin, zeatin riboside, and the 0-glucosides of these two compounds, relatively high levels of zeatin-9-D-glucopyranoside. This is the first conclusive identification of an endogenous cytokinin 9-glucoside.Abbreviations GC gas chromatography - HPLC high-performance liquid chromatography - I.D. internal diameter - RFE rotary film evaporation - TLC thin layer chromatography - TMS trimethylsilyl - UV ultraviolet - Z zeatin - Z7G zeatin-7-glucoside - Z9G zeatin-9-glucoside - Z0G zeatin-0-glucoside - ZR zeatin riboside - ZR0G zeatin riboside-0-glucoside     

Identification of the cytokinins in red pine seedlings

Zeatin-9-riboside was identified in shoots and roots of Pinus resinosa by GC-MS analysis of its permethyl derivative. Based on their chromatographic properties on Sephadex LH-20 and C₁₈ HPLC, and their susceptibility to enzymatic degradation, several other cytokinins have been tentatively identified. The basic fraction of both the roots and shoots contained zeatin, whereas the shoots contained dihydrozeatin-O-glucoside and the roots contained zeatin-O-glucoside. Zeatin-9-riboside monophosphate, isopentenyladenosine monophosphate ([9R-5P]iP) and glucosyl phosphate derivatives were detected in the acidic fractions from both roots and shoots. There were equivalent amounts of [9R-5P]iP in both roots and shoots. The presence of equivalent amounts of [9R-5P]iP in both the roots and shots suggests that cytokinin biosynthesis may be occurring in both locations.Abbreviations AMP adenosine-5-monophosphate - BAP benzylaminopurine - BSA bovine serum albumin - BuOH butan-1-ol - CK cytokinin - (diH)Z dihydrozeatin - (diH OG)Z dihydrozeatin-O-glucoside - (diH OG)[9R]Z dihydrozeatin-9-riboside-O-glucoside - DW dry weight - EtOH ethanol - FW fresh weight - GC-MS gas chromatography-mass spectrometry - HPLC high-performance liquid chromatography - [9R]iP isopentenyladenosine - [9R-5P]iP isopentenyladenosine monophosphate - MeOH methanol - PVP polyvinylpyrrolidone - RFE rotary film evaporation - TEAB triethyl ammonium bicarbonate - Z zeatin - [9R]Z zeatin-9-riboside - (OG)Z zeatin-O-glucoside - [7G]Z zeatin-7-glucoside - [9R-5P]Z zeatin-9-riboside monophosphate     

Mass-spectrometric quantitation of cytokinins in tobacco crown-gall tumours induced by mutated octopine Ti plasmids of Agrobacterium tumefaciens

The levels of the major cytokinins, zeatin, zeatin riboside, zeatin riboside-5-monophosphate and zeatin-7-glucoside were measured in tobacco (Nicotiana tabacum L.) crown-gall tissues carrying insertion and deletion mutations in the T-DNA. Measurements were made by combined gas chromatography-mass spectrometry using selected ion monitoring with ¹⁵N- and ²H-labelled internal standards. The results demonstrate that, relative to wild-type tumour tissue, cytokinin levels are considerably elevated in tissues lacking functional T-DNA auxin-biosynthetic genes. From a detailed analysis of the major cytokinin metabolites it is concluded that a reduction in the extent of cytokinin degradation via N⁶-side-chain cleavage is an important factor leading to increased cytokinin levels in these tissues.Abbreviations IAA indole-3-acetic acid - SIM selected ion monitoring - Z zeatin - [7G]Z zeatin-7-glucoside - [9R]Z zeatin-9-riboside - [9R-5P]Z zeatin riboside-5-monophosphate     

Isolation of two cytokinin metabolites from the rhizosphere of Norway spruce seedlings (Picea abies L. Karst.)

Roots of young Norway spruce seedlings were incubated under hydroculture conditions in a synthetic nutrient medium containing either ³H-isopentenyladenosine, isopentenyladenosine or zeatin riboside. When feeding with ³H-isopentenyladenosine a new radiaolabelled metabolite was found in the feeding solution as well as in root extracts. Isopentenyladenosine and zeatin riboside were metabolised and for both compounds an unknown metabolite was detected in the feeding solution. The metabolites were purified by solid phase extraction, HPLC and partially characterised. A major characteristic of the metabolites is their reactivity in the presence of NH₄OH, which results in the formation of the cytokinin bases isopentenyladenine or zeatin, respectively. UV-spectra and the chemical characteristics indicate that the new metabolites are closely related. The GC-MS analysis revealed, that the metabolites are true derivatives of isopentenyladenine and zeatin. The biogenesis of the new metabolites is discussed with regard to plant microbial interactions.Abbreviations Ck(s) = cytokinin(s) - GC-MS = gas chromatography-mass spectrometry - iP = isopentenyladenine - [9R]iP = isopentenyladenosine - [9G]iP = isopentenyladenine-9-glucoside - [9R-MP]iP = isopentenyladenosine-5-monophosphate - Z = trans-zeatin - [9R]Z = trans-zeatin riboside     

An evaluation of the role of cytokinins in the development of abnormal inflorescences in oil palms (Elaeis guineensis Jacq.) regenerated from tissue culture

Tissue cultures and regenerant plants from cell lines producing palms with normal and abnormal flowers were analyzed for cytokinin content and compared with zygotic embryos and seedlings. Immature inflorescences at the critical stage of flower development dissected from normal and abnormal palms were also analyzed. High performance liquid chromatography (HPLC)/radioimmunoassay and HPLC/enzyme-linked immunosorbent assay methods were used over a period of several years to measure the isoprenoid cytokinins. The results of analyses of endogenous aromatic cytokinins, present at comparable levels, will be reported separately. Oil palm cultures and regenerant plants contained relatively high concentrations of the 9-glucosides of isopentenyladenine ([9G]iP) and zeatin ([9G]Z). The predominant biologically active isoprenoid cytokinin present was zeatin riboside ([9R]Z), with lesser amounts of isopentenyladenine (iP) and isopentenyladenosine ([9R]iP). There was evidence of small amounts of dihydrozeatin compounds, but high concentrations (mainly as dihydrozeatin-9-glucoside ([9G]DHZ)) were confined to the haustorium of the zygotic embryo. Callus tissue contained very low concentrations of cytokinin. Frequently only [9G]iP could be detected, at about 1 pmol · g^-1 fresh weight, with [9R]Z at less than 0.05 pmol · g^-1. In comparison, nodular embryogenic tissues in vitro contained between 30 and 1,500 pmol · g^-1 of [9G]iP, 5–50 pmol · g^-1 of [9G]Z, and up to 12 pmol · g^-1 of [9R]Z. Shoots of regenerant plantlets and seedlings contained lower concentrations of [9G]iP (3–30 pmol · g^-1), although this was still the predominant cytokinin. [9R]Z and [9G]Z were present at between 2 and 15 pmol · g^-1, with iP at 1–5 pmol · g^-1 and [9R]iP at between 1 and 12 pmol · g^-1. Seedlings contained similar amounts with the exception of a lower [9G]iP content (5–10 pmol · g^-1) and more [9R]iP (10–20 pmol · g^-1). Root tissues of ramets contained significantly higher concentrations of [9G]iP than shoots. Comparison of two isogenic lines of one clone giving rise to normal and abnormal palms showed significantly higher concentrations of [9R]Z and [9G]Z in the normal than in the abnormal line and, in embryoids only, higher [9G]iP in the normal line. In all other cases the between-done differences were greater than any normal/abnormal differences. There was a general tendency for increased concentrations of [9G]iP in abnormal lines and for this compound to be in a higher concentration in embryoids and plants derived from culture than in zygotic embryos and seedlings. Analysis of cytokinins in immature female inflorescences of normal and abnormal palms of a single clone showed the abnormal inflorescences to have higher concentrations of [9R]Z and [9R]DHZ and less [9G]Z than the normal inflorescences at comparable stages of development.Abbreviations HPLC high performance liquid chromatography - [9G]iP 9-glucoside of isopentenyladenine - [9G]Z 9-glucoside of zeatin - [9R]Z zeatin riboside - iP isopentenyladenine - [9R]iP isopentenyladenosine - [9G]DHZ dihydrozeation-9-glucoside - ELISA enzyme-linked radioimmunosorbentassay - ANOVAR analysis of variance     

The effect of zeatin and iso-pentenyladenine on IAA transport from the shoot to the root of Pinus pinea seedlings

The tips of the tap roots of Pinus pinea seedlings were dipped in zeatin or iso-pentenyladenine solutions. Immediately after cytokinin application to the root tip or after a 24 h lag phase, [2-¹⁴C]IAA was applied to the shoot apex. Treating with zeatin resulted in an increase in [2-¹⁴C]IAA transport from the shoot to the root. Iso-pentenyladenine also caused a slight increase in transport of radioactivity to the root but this was less pronounced compared to the results obtained with zeatin. With zeatin treatment increasing amounts of radioactivity accumulated in the lateral root emerging zone of the tap root (Section III). This was in sharp contrast to the treatment with iso-pentenyladenine where little radioactivity accumulated in this section of the root. Recovery of radioactivity 48 h after applying [2-¹⁴C]IAA showed that 33% of the recovered radioactivity co-chromatographed with authentic IAA. The implications of the effect of different cytokinins on the distribution of radioactivity along the tap root of Pinus pinea following [2-¹⁴C]IAA application to the shoot are discussed.Abbreviations Z zeatin - iP iso-pentenyladenine - TCL thin-layer chromatography     

Morphology of potato (Solanum tuberosum L. cv. Sante) stem node cultures in relation to the level of endogenous cytokinins

Stem node culture of the potato (Solanum tuberosum) cv. Sante was used to examine the phenotypical alterations due to different levels of endogenous cytokinins. The altered phenotype, which dramatically deviates from the control phenotype, was induced after treatment of plantlets with 1 m jasmonic acid. Plantlets grown on the medium supplemented with jasmonic acid were taller, with well developed root systems, expanded leaves, thickened stems, and they showed hyperhydric symptoms. Their cytokinin content was about half that of the control plantlets. Morphologic characteristics corresponding to transgenic plants that overproduce cytokinins, including release of axillary buds and inhibited rooting, correlated with the high cytokinin levels in control plants.Abbreviations JA jasmonic acid - Z trans-zeatin - ZR trans-zeatin riboside - ZRMP zeatin riboside 5-monophosphate - Z-9-G trans-zeatin N-9-glucoside - DHZ dihydrozeatin - DHZR dihydrozeatin riboside - DHZRMP dihydrozeatin riboside 5-monophosphate - DHZ-9-G dihydrozeatin 9-glucoside - iP iso-pentenyladenine - iPA iso-pentenyladenosine - iP-9-G iso-pentenyladenine 9-glucoside - HPLC high performance liquid chromatography     

Relationship between endogenous auxin and cytokinin levels and morphogenic responses inActinidia deliciosa tissue cultures

Summary Thein vitro culture ofActinidia deliciosa petioles results in a decline of cytokinin content and an increase of auxin levels. The addition of plant growth regulators (PGRs) to the medium lead to recovery of the initial auxin content, and callus induction occurs at the basal end of the explants. Endogenous auxin/cytokinin ratio was higher at this side than in the apical one, due to unequal distribution of endogenous PGRs in the cultured petioles. Some of the induced calluses showed shoot formation when they were transferred to proliferation medium. Most important differences found in hormonal content between organogenic and non-organogenic callus concerned benzyladenine levels. In this paper the relationships between explant behaviour and their hormonal content is discussed.Abbreviations BM basal medium - BA 6-benzyladenine - CIM callus induction medium - CPM callus proliferation medium - (diH)Z dihydrozeatin - DW dry weight - ELISA enzyme linked immunoassay - FW fresh weight - HPLC high performance liquid chromatography - IAA indole-3-acetic acid - iP N⁶-(²-isopentenyl)adenine - NAA 1-naphthaleneacetic acid - PBS phosphate buffer - PGR plant growth regulator - (diH)[9R]Z 9--D-ribofuranosyl-(diH) - [9R]iP 9--Dribofuranosyl-iP - [9R]Z 9--D-ribofuranosylzeatin - TBS trishydroxymethyl-aminomethane buffer - Z zeatin     

Cultivars of Hexaploid Wheat of Contrasting Stature and Chlorophyll Retention Differ in Cytokinin Content and Responsiveness

The work reported here compared cytokinin content and sensitivityin a selection of hexaploid wheat (Triticum aestivum L.) cultivarsusing the following measurements: leaf cytokinins at three timepoints during light-growth and at four 24 h intervals afterlight-grown plants were transferred to darkness; sensitivityof root growth to direct applications of isopentenyl adenosine([9R]iP); and, sensitivity of germination and subsequent rootand shoot growth to 18 h imbibition of seeds in benzyladenine(BA). Accumulation of zeatin riboside-type cultivars was greatestduring light-growth in Tibet Dwarf, a wheat with an extremedwarf phenotype, intermediate in Omar standard and dwarf cultivars,and lowest in the standard and dwarf versions of Itana. Cytokininlevels were otherwise not directly correlated to plant staturein these wheats. There were no cultivar-associated qualitativedifferences in the types of cytokinins detected in this study.During the 16 h light period, the content of zeatin riboside-typecytokinins increased up to tenfold and then declined to basallevels during dark growth. Chlorophyll retention during dark-growthwas correlated with leaf cytokinin content. Data collected ata restricted number of sampling points during dark-growth suggesteda cyclic accumulation of [9R]iP-type cytokinins and the apparentcycle in Tibet Dwarf was offset by 24 h. Tibet Dwarf showedthe greatest root growth inhibition after exposure of seedlingroots to [9R]iP or imbibition of seeds in BA. Neither of thesetreatments affected shoot growth in any of the cultivars. Wheat; Triticum aestivum ; cytokinin; zeatin riboside; benzyladenine; root inhibition     

Plant growth regulators as putative physiological markers of developmental stage in Prunus persica

Prunus persica plants of different ages and statesof maturation were analysed to compare their phytohormonal status. Endogenouslevels of indole-3-acetic acid (IAA), abscisic acid (ABA), and severalcytokinins (Cks): zeatin (Z), zeatin riboside ([9R]Z), dihydrozeatin ((diH)Z),dihydrozeatin riboside ((diH)Z[9R]), isopentenyl adenine (iP) and isopentenyladenosine ([9R]iP), were measured in order to determine their possible use asphysiological indices of phase change and maturation. A decrease in Ck levels(Z, [9R]Z, (diH)Z, (diH)[9R]Z, and iP, [9RiP) was found from the embryonic tojuvenile stage as well as a decrease in the ratio of iP-type (iP and[9R]iP)/Z-type Cks paralleling the increase in tree age. ABA levels increasedduring maturation in Prunus persica and the ratio ofCks/IAA decreased with tree age. From our results, we propose that the balancesof Cks/IAA and iP-type/Z-type Cks are good indices of different developmentalstates in Prunus persica.     

Chicken egg yolk antibodies for cytokinin analysis

The production, isolation, and purification of specific chicken immunoglobulins (Igs) against three main groups of naturally occurring cytokinins are reported. The specific Igs directed against, respectively, zeatin riboside, dihydrozeatin riboside, and isopentenyladenosine are extracted from the egg yolk and used in radioimmunoassays that allow the quantification in parallel of pmol of the cytokinins in plant extracts. As little as 50 fmol of zeatin riboside, 20 fmol of isopentenyladenosine, and 40 fmol of dihydrozeatin riboside can be detected. The levels of cytokinins measured in the radio-immunoassay correlate well with physicochemical analysis methods such as high performance liquid chromatography (HPLC) with UV spectrum detection and HPLC-coupled mass spectrometric detection. Cross-reactivity studies indicate that the assay is not affected by most of the structurally related compounds. The respective antibody preparations recognized zeatin riboside, dihydrozeatin riboside, and isopentenyladenosine and the corresponding free bases. The results obtained when analyzing crude plant extracts are expressed as zeatin riboside equivalents, dihydrozeatin riboside equivalents, and isopentenyladenosine equivalents.Abbreviations B binding activity - B ₀ maximal binding - B ₁ unspecific binding - GC gas chromatography - HPLC high performance liquid chromatography - LC-MS HPLC-coupled mass spectrometry - MOPS 4-morpholinepropanesulfonic acid - RIA radioimmunoassay - TBS Tris-buffered saline - (diH)Z dihydrozeatin - (diH) [9R]Z dihydrozeatin riboside - iP isopentenyladenine - [9R]iP isopentenyladenosine - Z zeatin - [9R]Z zeatin riboside - [9G]iP isopentenyladenine-9-glucoside - [9R-5P]iP isopentenyladenosine-5-monophosphate     

A high affinity binding site for cytokinin to a particulate fraction in carrot suspension cells

Summary Carrot suspension cells contain one class of high affinity binding sites for cytokinin in an 80,000 × g particulate fraction. Binding of [8-¹⁴C]-benzylaminopurine (BA) to this fraction assayed by a sedimentation method was found to be optimal at pH 6.0 and thermolabile. Specific binding was proved in competition experiments in which labelled BA was displaced by increasing concentrations of unlabelled BA. Scatchard plots of these results displayed a dissociation constant (K_d) of 33 ± 6 nM. The number of binding sites found was 1,100 ± 120 fmol g^–1 fresh weight which is equivalent to a frequency of 23,000 binding sites per cell. The specificity of the binding sites to cytokinins and their analogues followed the sequence BA with highest affinity, kinetin, zeatin, iP and adenine. The cytokinin ribosides generally had a lower affinity than their cytokinin bases, and the affinity decreased in the order [9 R] BA, [9 R] iP, [9 R] Z, [9 R] A.     

Mass-spectrometric quantification of cytokinin nucleotides and glycosides in tobacco crown-gall tissue

the cytokinins of tobacco crown-gall tissue have been analysed by quantitative mass spectrometry using ²H₂-labelled cytokinin riboside 5-monophosphates and ¹⁵N₄-labelled cytokinin glycosides as internal standards. The principal endogenous cytokinin of this tissue is zeatin riboside 5-monophosphate. The biologically inactive 7-glucoside of zeatin is the most abundant basic cytokinin in the tissue. These findings expose the limitations of previously reported analyses of similar tissues, which were restricted to biologically active basic cytokinins. The present study demonstrates that the endogenous cytokinins of tobacco crowngall tissue show a clear correspondence to the range of metabolites formed when exogenous cytokinins are supplied to nontumorous tobacco cells.Abbreviations DHZ dihydrozeatin - DHZ7G dihydrozeatin 7-glucoside - DHZMP dihydrozeatin 9-riboside 5-monophosphate - DHZR dihydrozeatin 9-riboside - GC-MS coupled gas chromatography-mass spectrometry - HPLC high-performance liquid chromatography - Z7G zeatin 7-glucoside - Z9G zeatin 9-glucoside - ZOG zeatin O-glucoside - ZMP zeatin 9-riboside 5-monophosphate - ZR zeatin 9-riboside - ZROG zeatin 9-riboside O-glucoside     

Hormones and Pod Development in Oilseed Rape (Brassica napus)

The endogenous levels of several plant growth substances (indole acetic acid, IAA; abscisic acid, ABA; zeatin, Z; zeatin riboside, [9R]Z; isopentenyladenine, iP; and isopentenyladenosine, [9R]iP were measured during pod development of field grown oilseed Rape (Brassica napus L. var oleifera cv Bienvenu) with high performance liquid chromatography and immunoenzymic (enzyme-linked immunosorbent assay, ELISA) techniques. Results show that pod development is characterized by high levels of Z and [9R]Z in 3 day old fruits and of IAA on the fourth day. During pod maturation, initially a significant increase of IAA and cytokinins was observed, followed by a progressive rise of ABA levels and a concomitant decline of IAA and cytokinin (except iP) levels. The relationship between hormone levels and development, especially pod number, seed number per pod, and seed weight determination, will be discussed.     

Involvement of cytokinins in the germination of chick-pea seeds

Eight cytokinins detected in germinated chick-pea (Cicer arietinum L. var. Castellana) seeds were first present in the embryonic axes but appeared in the cotyledons after 12h of germination. The cytokinins detected in the cotyledons originate in the embryonic axes, but no passage of these substances from the cotyledons to the axes was detected, except when the seeds were treated with red light.It is concluded that the role played by the embryonic axis in mobilizating the main reserves of the cotyledons is mainly effected through these cytokinins. Both natural and synthetic cytokinins exert an important regulatory role in the hydrolysis of reserve proteins and calcium could be involved as an intermediate.Abbreviations BA benzyladenine - cot. cotyledon - (diH)Z dihydrozeatin - (diH)ZR dihydrozeatin riboside - GZR glycosyl zeatin riboside - 2iP 277-1 - iPA 277-2 riboside - Kin kinetin - Z zeatin - ZG zeatin glucoside - ZR zeatin riboside     

Metabolism and Translocation of Exogenous Zeatin Riboside in Germinating Seeds and Seedlings of Zea mays

High specific activity [³H]-zeatin riboside (ZR) was suppliedto germinating seed and developing seedlings of Zea mays tostudy its metabolism and translocation The major metabolitesof ZR in endosperm, embryo, and first leaves were adenosine,adenine, and adenine nucleotide When ZR was supplied to theradicle tip a significant proportion of the radioactivity extractedfrom the radicle was identified as zeatin-9-glucoside (Z9G).However, some ZR was also transported to the shoot and vestigialembryo During the initial stage of germination, movement ofzeatin riboside from the embryo to the endosperm was pronouncedbut little movement occurred in the reverse direction Key words: Zea mays cytokinin, zeatin riboside, metabolism, translocation     

The effect of aluminum on cytokinins in the mycelia of Amanita muscaria

High performance liquid chromatography analysis of immunoaffinity-purified extracts of mycelia of Amanita muscaria, and the Amaranthus bioassay of the eluted fractions, revealed the following seven cytokinins: zeatin, zeatin riboside, zeatin N-9-glucoside, dihydrozeatin, dihydrozeatin riboside, isopentenyl adenine, and isopentenyl adenosine. The decreased growth of aluminum-treated mycelia correlated with a 35% decrease in the total amount of the cytokinins. Among individual cytokinins, zeatin was the most affected, exhibiting a reduction of about 90%. The results are compared with previous investigations of aluminum effects on cytokinins in the mycelia of Lactarius piperatus, whose growth is stimulated by aluminum.Abbreviations ZR zeatin riboside - iPA isopentenyl adenosine - Z zeatin - DHZ dihydrozeatin - iP isopentenyl adenine - DHZR dihydrozeatin riboside - Z-9G zeatin N-9-glucoside - iP-9G isopentenyl N-9-glucoside - HPLC high performance liquid chromatography - DHZRMP dihydrozeatin riboside monophosphate - ZRMP zeatin riboside monophosphate