Showing papers on "Zeatin published in 1983"
TL;DR: Thidiazuron appears to stimulate enzyme activity converting the ribon nucleotide to ribonucleoside as well as nucleotide formation, and the two types of effects do not seem to be related.
Abstract: The effects of a highly cytokinin-active urea derivative, N-phenyl-N′-1,2,3-thiadiazol-5-ylurea (Thidiazuron), and zeatin on cytokinin-autonomous growth and the metabolism of N6-(Δ2-isopentenyl)[8-14C]adenosine ([14C]i6 Ado) were examined in callus tissues of two Phaseolus lunatus genotypes, cv Jackson Wonder and P.I. 260415. Tissues of cv Jackson Wonder maintained on any concentration of Thidiazuron became cytokinin autonomous, whereas only tissues exposed to suboptimal concentrations of zeatin displayed cytokinin-autonomous growth. Tissues of P.I. 260415 remained cytokinin dependent under all these conditions. The metabolism of [14C]i6 Ado was similar for the two genotypes, but differed with the medium used. [14C]i6 Ado was rapidly converted to N6-(Δ2-isopentenyl)[8-14C]adenosine 5′-P ([14C]i6 AMP) by tissues grown on zeatin-containing medium, whereas only traces of the nucleotide were formed in tissues grown on medium with Thidiazuron. Incubation with [14C] i6 AMP of tissues grown in the presence of Thidiazuron resulted in rapid conversion to [14C]i6 Ado, while [14C]i6 AMP persisted in tissues maintained on zeatin. Thus, Thidiazuron appears to stimulate enzyme activity converting the ribonucleotide to ribonucleoside. Although the cytokininactive phenylureas and adenine derivatives differ in their effects on cytokinin autonomy as well as nucleotide formation, the two types of effects do not seem to be related.
184 citations
TL;DR: Regulation of maturation would facilitate future efforts to manipulate somatic embryos for large scale propagation in batch cultures, mechanized planting, artificial induction of dormancy, and incorporation into artificial seeds.
Abstract: The ability to control plant somatic embryogenesis is a necessary prelude to its development as an efficient biotechnological tool. The influence of different suspension culture techniques on the maturation of caraway (Carum carvi) somatic embryos and the effect of growth hormones in controlling development were studied. The three types of culture vessels (tumble tubes, test tubes, and Erlenmeyer flasks), each providing contrasting techniques of agitation, generated populations differing significantly in the frequencies of normal and abnormal embryos. Abscisic acid (ABA), at the appropriate concentrations, effectively normalized development in all systems, inhibiting abnormal proliferations and precocious germination and fostering normal maturation. For those cultures where embryos failed to develop on unsupplemented medium, zeatin in combination with ABA fostered growth and normal maturation. Carrot (Daucus carota) somatic embryo development could be similarly controlled. Such regulation of maturation would facilitate future efforts to manipulate somatic embryos for large scale propagation in batch cultures, mechanized planting, artificial induction of dormancy, and incorporation into artificial seeds.
133 citations
TL;DR: To serve as a guide in the selection of the most suitable bioassay for detection of the above-mentioned cytokinin conjugates, the lowest detectable amounts in selected bioassays have been compared.
Abstract: In a number of cytokinin bioassays, the activities of the following compounds were compared: 3-, 7-, and 9-glucosides of 6-benzylaminopurine (BAP); 7- and 9-glucosides of zeatin; O-glucosides of zeatin, dihydrozeatin, and their ribosides; 9-alanine conjugates of zeatin, and BAP The bioassays included the radish cotyledon, theAmaranthus betacyanin, the oat leaf senescence, and the tobacco pith callus Cytokinin activity was markedly reduced by 7- and 9-glucosylation in nearly all bioassays, but 3-glucosylation of BAP and O-glucosylation of the zeatin sidechain usually had little effect on activity However, there were two notable exceptions to this generalization: the activity of O-glucosylzeatin markedly exceeded that of zeatin in the oat leaf senescence assay; 9-glucosyl-BAP and free BAP were similarly active in retarding the senescence of radish leaf discs The 9-alanine conjugate of zeatin (lupinic acid) and of BAP were markedly less active than zeatin and BAP, respectively, in all bioassays, but the responses evoked by these conjugates at high concentrations in theAmaranthus bioassay approached those caused by the corresponding base The activities of several new compounds related to the alanine conjugate of BAP were also assessed To serve as a guide in the selection of the most suitable bioassay for detection of the above-mentioned cytokinin conjugates, the lowest detectable amounts in selected bioassays have been compared
88 citations
TL;DR: The data suggest that metabolism of auxins may be important for the persistence of a functional root nodule and the identity of these compounds was obtained by chromatography in other systems.
Abstract: [(3)H]Zeatin riboside was supplied to intact pea (Pisum sativum) plants either onto the leaves or onto the root nodules. When applied directly to nodules, approximately 70% of recovered radioactivity remained in the nodules, approximately 15% was detected in the root system, and 15% was in the shoot. However, when supplied to the leaves, little (3)H was transported, with approximately 0.05% of recovered radioactivity being found in the root system and nodules. On a fresh weight basis, nodules accumulated more (3)H than the parent root. In both types of studies, metabolites with an intact zeatin moiety were detected in root nodules.In all experiments, two-dimensional thin layer chromatography revealed that little (3)H remained as zeatin riboside in root or nodule tissue at the end of the labeling period. Nodules metabolized [(3)H]zeatin riboside to the following cytokinins/cytokinin metabolites: zeatin, adenosine, adenine, the O-glucosides of zeatin and zeatin riboside, lupinic acid, nucleotides of adenine and zeatin, and the dihydro derivatives of many of these compounds.Although a few small differences were observed, there were no major differences between root and nodule tissue in their metabolism of [(3)H] zeatin riboside. Furthermore, any differences between effective and ineffective nodules were generally minor.
80 citations
TL;DR: Equilibrium dialysis revealed high affinity binding sites for [14C]adenine on the lectins from Dolichos biflorus, Phaseolus vulgaris, and soybean, demonstrating that binding of ligands to the two classes of hydrophobic sites is thermodynamically linked.
78 citations
TL;DR: The cytokinin complex of Datura innoxia Mill crown gall tissue was purified by ion exchange, Sephadex LH-20 chromatography and reversed-phase high performance liquid chromatography, and dihydrozeatin riboside and isopentenyladenosine were identified in the nucleotide fraction following enymic degradation.
Abstract: The cytokinin complex of Datura innoxia Mill. crown gall tissue was purified by ion exchange, Sephadex LH-20 chromatography and reversed-phase high performance liquid chromatography. By gas chromatography-mass spectrometry using 2H-labeled compounds, the following cytokinins were identified in the basic fraction eluting from a cation exchange column: zeatin, zeatin riboside, dihydrozeatin, dihydrozeatin riboside, their corresponding O-glucosides, 7- and 9-glucosides of zeatin, 9-glucoside of dihydrozeatin, isopentenyladenine, and isopentenyladenosine. Zeatin riboside 5′-monophosphate was the major cytokinin nucleotide in the tissue. In addition, dihydrozeatin riboside and isopentenyladenosine were identified in the nucleotide fraction following enymic degradation.
74 citations
TL;DR: In carnation foliage leaves pretreated with 0.1 mm BA, a reduction rather than inhibition of the conversion of exogenous ACC to ethylene was observed, which indicates that foliage leaves respond to cytokinins in a different way than petals.
Abstract: Pretreatment of detached carnation petals (Dianthus caryophyllus cv White Sim) for 24 hours with 0.1 millimolar of the cytokinins n(6)-benzyl-adenine (BA), kinetin, and zeatin blocked the conversion of externally supplied 1-aminocyclopropane-1-carboxylic acid (ACC) to ethylene and delayed petal senescence by 8 days. The normal enhanced wilting and increase in endogenous levels of ACC and ethylene production following exposure of petals to ethylene (16 mul/l for 10 hours), were not observed in BA-pretreated petals. In carnation foliage leaves pretreated with 0.1 mm BA, a reduction rather than inhibition of the conversion of exogenous ACC to ethylene was observed. This indicates that foliage leaves respond to cytokinins in a different way than petals. A constant 24-hour treatment with BA (0.1 mm) was not able to reduce ethylene production of senescing carnation petals, while 2 mm aminoxyacetic acid, a known inhibitor of ACC synthesis, or 10 mm propyl gallate, a free radical scavenger, decreased ethylene production significantly.
71 citations
TL;DR: Single applications of either 6-benzyladenine or zeatin to inhibited axillary buds of intact, light-grown seedlings of Pisum sativum L. cv Black-eyed Susan resulted in the formation of rapidly elongating, leafy shoots.
Abstract: Single applications of either 6-benzyladenine or zeatin to inhibited axillary buds of intact, light-grown seedlings of Pisum sativum L. cv Black-eyed Susan, resulted in the formation of rapidly elongating, leafy shoots. Similar treatment with kinetin or isopentenyladenine caused only limited but outgrowth which stopped 6 days after application.
62 citations
TL;DR: The differing activities of zeatin and BAP in the oat-leaf senescence bioassay appear to be, at least partially, a consequence of their differing metabolism and are not attributable to differences in uptake.
Abstract: The metabolism of zeatin and that of 6-benzylaminopurine (BAP) have been compared in oat leaf segments in relation to the markedly differing ability of these cytokinins to retard senescence of such segments. Free BAP and a highly active senescence-retarding metabolite of BAP were detected in oat leaf segments supplied with BAP. The metabolite was identified by mass spectrometry and chromatography as 3-β-D-glucopyranosyl-BAP. The major metabolite of BAP was the 9-glucoside, but this lacked significant senescence-retarding activity. In contrast, in leaf segments supplied with zeatin, no free zeatin and no senescence-retarding metabolite of zeatin were detectable. The major metabolites of zeatin were adenosine, adenine nucleotides, the 9-glucoside, and unidentified polar metabolites. The differing activities of zeatin and BAP in the oat-leaf senescence bioassay appear to be, at least partially, a consequence of their differing metabolism and are not attributable to differences in uptake.
43 citations
TL;DR: For the past ten years plant tissue culture has truly exploded and now more than ten thousand people are engaged in this field: International Congress held in July 1982 at Lake Yamanaka, Japan is evidence for this effusive development.
Abstract: The author has lived in the plant tissue culture history since its beginning and had the opportunity to discuss with all the pioneers
43 citations
TL;DR: The data suggest that the flux of minerals and cytokinin from the roots could influence foliarsenescence in soybeans, but increased stomatal resistance does not seem to cause foliar senescence.
Abstract: Excised soybean (Glycine max [L] Merrill) cv Anoka leaf discs tend to remain green even after the corresponding intact leaves have turned yello on fruiting plants We have found that explants which include a leaf along with a stem segment (below the node) and one or more pods (maintained on distilled H(2)O) show similar but accelerated leaf yellowing and abscission compared with intact plants In podded explants excised at pre-podfill, the leaves begin to yellow after 16 days, whereas those excised at late podfill begin to yellow after only 6 days Although stomatal resistances remain low during the first light period after excision, they subsequently increase to levels above those in leaves of intact plants Explants taken at mid to late podfill with one or more pods per node behave like intact plants in that pod load does not affect the time lag to leaf yellowing Explant leaf yellowing and abscission are delayed by removal of the pods or seeds or by incubation in complete mineral nutrient solution or in 46 micromolar zeatin Like chorophyll breakdown, protein loss is accelerated in the explants, but minerals or especially zeatin can retard the loss Pods on explants show rates and patterns of color change (green to yellow to brown) similar to those of pods on intact plants These changes start earlier in explants on water than in intact plants, but they can be delayed by adding zeatin Seed dry weight increased in explants, almost as much as in intact plants Explants appear to be good analogs of the corresponding parts of the intact plant, and they should prove useful for analyzing pod development and mechanisms of foliar senescence Moreover, our data suggest that the flux of minerals and cytokinin from the roots could influence foliar senescence in soybeans, but increased stomatal resistance does not seem to cause foliar senescence
TL;DR: When isopentenyl[8- 14 C]adenine was incubated with crown gall tumour tissue of Vinca rosea, it was stereospecifically hydroxylated to trans -zeatin and its derivatives, which are the endogenous free cytokinins in this tissue.
TL;DR: High yields of mesophyll protoplasts were obtained after treatment of leaves of Trigonella foenumgraecum, a forage legume, with purified cellulase and addition of glutamine and asparagine to the medium was found essential for rapid cell division, callus growth and differentiation.
Abstract: High yields of mesophyll protoplasts were obtained after treatment of leaves of Trigonella foenumgraecum, a forage legume, with purified cellulase. Under appropriate conditions of culture up to 70% plating efficiency could be obtained. The protoplast-derived colonies developed into rapidly growing green calli and produced leafy shoots on a medium containing 0.1 mg/l each of benzylaminopurine (BAP) and zeatin. Addition of glutamine and asparagine to the medium was found essential for rapid cell division, callus growth and differentiation.
TL;DR: Organ expiants of Solarium khasianum C. Clarke var.
TL;DR: The cytokinin activity has been isolated and identified from extracts of immature mango (Mangifera indica L.) seeds and the structures of zeatin,Zeatin riboside, and N(6)-(Delta(2)-isopentenyl)adenine Riboside were confirmed on the basis of their chromatographic behavior and mass spectra of trimethylsilyl derivatives.
Abstract: The cytokinin activity has been isolated and identified from extracts of immature mango ( Mangifera indica L.) seeds. The structures of zeatin, zeatin riboside, and N 6 -(Δ 2 -isopentenyl)adenine riboside were confirmed on the basis of their chromatographic behavior and mass spectra of trimethylsilyl derivatives. Both trans and cis isomers of zeatin and zeatin riboside were also identified by the retention times of high performance liquid chromatography. In addition, an unidentified compound appeared to be a cytokinin glucoside. The concentration of cytokinins in the panicle and pulp of mango reached a maximum 5 to 10 days after full bloom and decreased rapidly thereafter. The cytokinin level in the seed remained high until the 28th day after full bloom. The quantity of cytokinins in pulp per fruit increased from the 10th day after full bloom, the maximum being attained around the 50th day after full bloom. Similarly, the amount of cytokinins per seed increased from the 10th day after full bloom, reaching a peak on the 40th day and decreasing gradually thereafter. A high percentage of fruit set in mango was persistently maintained by supplying 6-benzylaminopurine (1.5 × 10 3 micromolar) onto the panicle at the anthesis stage and by supplying gibberellic acid (7.2 × 10 2 micromolar) and naphthalene acetamide (3.1 × 10 micromolar) at the young fruit stage.
TL;DR: Soybean explants consisting of a leaf, one or more young pods, and a subtending piece of stem were given a 1-h pulse of3H (ring-labeled)-zeatin riboside (ZR) or -zeatin (Z), via the base of the stem, followed by a 24-h incubation, and cytokinin was rapidly converted to diverse metabolites including adenosine and adenine.
Abstract: Soybean explants consisting of a leaf, one or more young pods, and a subtending piece of stem were given a 1-h pulse of3H (ring-labeled)-zeatin riboside (ZR) or -zeatin (Z), via the base of the stem, followed by a 24-h incubation. At the end of the pulse, about 55% of the soluble3H was in the leaf blades, 11% in the petiole, 30% in the stem, 2% in the carpels, 0.1% in the seed coats, and 0.08% in the embryos. After 24 h, the percentages were 58, 7, 26, 6, 2, and 0.3, respectively. During this period, the total soluble3H decreased by 84%, the remainder being bound to “insoluble” material. The3H-cytokinin was rapidly converted to diverse metabolites including adenosine and adenine. At the end of the 1-h pulse, appreciable percentages (1–16%) of the total soluble3H in the seed coats chromatographed with ZR (or dihydro ZR) and with the 5′-phosphate of ZR, but these percentages declined markedly at 24 h. No distinct peaks of3H corresponded to known metabolites in the soluble extracts of embryos, and at 24 h, the3H equivalent to ZR must have been less than 0.0006% of the3H-ZR supplied. The bound3H corresponded to adenine and guanine in DNA and RNA. In contrast to cytokinin,3H-adenosine given as a pulse was readily translocated into the seed coats and embryos. Thus, cytokinin (ZR and Z) flowing up through the xylem from the root system does not readily enter the embryo (though metabolites such as adenosine could), and the seeds clearly do not compete with the leaves for this supply of cytokinin.
TL;DR: A new enzyme, which catalyses the conversion of the cytokinin zeatin to the alanine conjugate l upinic acid, has been partly purified from developing lupin seed and the possible role of the enzyme, tentatively called β-(9-cytokinin)alanine synthase or lupinic acid synthase, in the regulation of hormone activity is discussed.
TL;DR: Maize (Zea mays L.) A188 calluses derived from leaf tissues of in vitro grown seedlings produced green leafy structures and subsequently plantlets upon transfer to N6 medium containing 2mg/1 2,4-D and 0.1 mg/1 zeatin.
Abstract: Maize (Zea mays L.) A188 calluses derived from leaf tissues of in vitro grown seedlings were initiated and maintained on Murashige and Skoog medium supplemented with 2 mg/1 2,4-dichlorophenoxyacetic acid (2,4-D). The calluses produced green leafy structures and subsequently plantlets upon transfer to N6 medium containing 2 mg/1 2,4-D and 0.1 mg/1 zeatin. An embryo-like structure with a green prominent coleoptile and a scutellum-like body was also obtained.
TL;DR: The inhibition of ABA biosynthesis was concentration dependent and, in studies using farnesyl-[1-14C]pyrophosphate, appeared to be specific rather than resulting from a general blocking of terpenoid biosynthesis.
TL;DR: It is concluded that cytokinins can stimulate citrus abscission in vitro and that this stimulation is not accompanied by marked effects on either measurable ethylene or ACC concentrations, which suggests that a minimum level of ethylene production is required for the cytokinin effect.
Abstract: The stylar abscission bioassay was used to identify five stimulators of lemon (Citrus limon cv. Lisbon) abscission in pistil explants. The stimulators (N-phenyl-N′-1,2,3-thiadiazol-5-ylurea, N6-benzyladenine, kinetin, zeatin, and N6-isopentenyladenine), which are all cytokinins, accelerated the timing of expiant abscission when they were added as supplements (100 μM) to the test medium. To study possible relationships between cytokinins, ethylene, and abscission, we measured accumulating ethylene concentrations in sealed cultures and endogenous 1 -aminocyclopropane-1-carboxylic aicd (ACC) in explants incubated on test medium plus or minus 100 μM N-phenyl-N′-1,2,3-thiadiazol-5-ylurea (thidiazuron), 100 μM N6-benzyladenine (bzl6Ade), or 2 μM picloram, an inhibitor of stylar abscission. Although ethylene accumulated to similar levels in all treatments, the concentrations obtained with picloram and thidiazuron were, respectively, higher and lower than those obtained in control cultures. The accumulation of ethylene in cultures with bzl6Ade, on the other hand, was not significantly different from controls. ACC concentrations in explants remained fairly constant in all treatments during the incubations, except in explants on thidiazuron, in which case the ACC concentration declined slightly. We conclude that cytokinins can stimulateCitrus abscissionin vitro and that this stimulation is not accompanied by marked effects on either measurable ethylene or ACC concentrations. Our finding that 100 μM aminoethoxyvinylglycine, an ethylene biosynthesis inhibitor, counteracts the stimulation of abscission by bzl6Ade suggests that a minimum level of ethylene production is required for the cytokinin effect. The possibility that cytokinins affect other aspects related to ethylene, such as biosynthetic rates, metabolism, or tissue retention, is not excluded by our results.
TL;DR: Deficiency of cytokinin in the fruit appears to favour fruit drop and cessation of fruit growth, and these fractions were termed Mf1 to Mf11, on the basis of their RF values and spectral properties.
Abstract: The fruit of mango (Mangifera indica L.) contained cytokinins in both pericarp and seed. During the single period of rapid growth in fruit and seed (7-42 days after pollination), cytokinin concentration increased rapidly at two times. The first preceded the period of rapid cell division and cell enlargement and the second coincided with the period of rapid cell enlargement only. Deficiency of cytokinin in the fruit appears to favour fruit drop and cessation of fruit growth. Eleven cytokinin fractions were isolated by ion-exchange column and paper chromatography from immature mango fruits. These fractions were termed Mf1 to Mf11, on the basis of their RF values and spectral properties. Two of these, Mf9 and Mf10, could be tentatively identified as zeatin riboside and zeatin, respectively.
TL;DR: The results show that the responsiveness of the plant to exogenously applied zeatin is not affected — except in anthocyanin synthesis — by a preceding or simultaneous light treatment, and the action of phytochrome on the developmental processes is not related to cytokinin levels.
Abstract: Intact mustard seedlings were treated with zeatin and photomorphogenetically active light in different ways: (1) hormone treatment preceding light treatment, (2) light treatment preceding hormone treatment, (3) hormone and light applied simultaneously. Under all experimental conditions the effect of the hormone treatment is multiplicative to the light effect with regard to the increase of cotyledon area. However, the hormone effect is additive to the light effect with regard to increases of the level of NADPH-dependent glyceraldehyde-3-phosphate dehydrogenase (EC 1.2.1.13) and carotenoid contents. Anthocyanin synthesis is inhibited by exogenous zeatin whereby the concentration response curves are similar, irrespective of the extent of anthocyanin formation mediated by light. However, an interaction was found in the sense that the responsiveness toward zeatin is decreased somewhat by the action of phytochrome. Our results show that the responsiveness to light (via the far-red-absorbing form of phytochrome; P
fr) is not changed by a preceding or simultaneous hormone treatment. Moreover, the responsiveness of the plant to exogenously applied zeatin is not affected — except in anthocyanin synthesis — by a preceding or simultaneous light treatment. We conclude from our results that the action of phytochrome on the developmental processes is not related to cytokinin levels.
TL;DR: It appears that the level of cytokinin detected in the tuber tissue depends on the degree of cell division occurring, and Cytokinins thus appear to be produced as a result of this process during wound healing in potato tubers.
TL;DR: Cocoa shoot tip and nodal bud expiants were cultured on modified Murashige and Skoog (1962) media and shoots produced were rooted on a medium with IBA, NAA and phloroglucinol.
Abstract: SummaryCocoa shoot tip and nodal bud expiants were cultured on modified Murashige and Skoog (1962) media. Shoot proliferation occurred during the first six weeks on media containing BAP, zeatin or zeatin riboside. The shoots so produced were rooted on a medium with IBA, NAA and phloroglucinol.
TL;DR: Sequential analysis of tissue extracts by thin-layer and high-performance-liquid chromatography identified zeatin nucleotide(s) (ZN), O-glucosyl zeat in riboside (OGZR), adenosine, and adenine nucleotide (AN) as the principal metabolites in both tissues.
Abstract: Aqueous solutions of auxin (indole-3-acetic acid,α-naphthalene acetic acid, or 2,4-dichlorophenoxyacetic acid) were active in inducing DNA synthesis and mitosis in prewashed tissue explants of mature Jerusalem artichoke tubers. Explants did not respond in this way to aqueous solutions of cytokinin (zeatin, zeatin riboside, 6-benzylaminopurine, or kinetin). The metabolism of [8-3H]zeatin riboside (ZR) was studied in non-dividing and auxin-induced synchronously dividing explants over the first 36 h of culture. ZR was taken up rapidly and to the same extent by both tissues. Sequential analysis of tissue extracts by thin-layer and high-performance-liquid chromatography identified zeatin nucleotide(s) (ZN), O-glucosyl zeatin riboside (OGZR), adenosine, and adenine nucleotide(s) (AN) as the principal metabolites in both tissues. The proportion of radio-activity due to ZR declined steadily and OGZR accumulated steadily at similar rates in both tissues. ZN was the major metabolite in both tissues at 12 h; thereafter ZN continued to accumulate in nondividing tissue, but its level declined in dividing tissue, and a corresponding increase in the levels of AN and adenosine was observed. These treatment differences in cytokinin metabolism were apparent at least 6 h before the onset of mitosis.
TL;DR: Using soybean expiants to study interactive effects of nutrient and hormone supply on leaf senescence symptoms and seed yield, a combination of mineral nutrients with zeatin acted synergistically to maintain green coloration throughout pod maturation and reduced declines in levels of leafsoluble protein and chlorophyll.
Abstract: The leaves of intact soybean plants (Glycine max. L. Merrill) characteristically turn yellow and abscise during pod maturation, and this may limit seed growth. We have used soybean expiants (excised 10 cm stem sections with a leaf and midfill pod attached) to study interactive effects of nutrient and hormone supply on leaf senescence symptoms and seed yield. Whereas mineral nutrients or cytokinin (zeatin) alone delayed development of visible leaf senescence symptoms in explants, a combination of mineral nutrients with zeatin acted synergistically to maintain green coloration throughout pod maturation and reduced declines in levels of leafsoluble protein and chlorophyll. The combination of complete mineral nutrients with zeatin gave seed yields equivalent to those in intact plants. Withdrawal of zeatin or individual mineral nutrients (particularly N and S) from the nutrient solution enhanced leaf senescence symptoms and reduced seed yields.
TL;DR: Nine-/3-D-Ribofuranosylzeatin 5 ’ -monophosphate (ZMP) has so far been isolated in crystalline form and identified unambiguously from Zea mays kernels only, but little effort has been made to identify and quantify cytokinin nucleotides present in the anionic fraction not re- tained by such columns.
TL;DR: From the available evidence, it is concluded that cytokinin conjugates are probably the major metabolites formed in the leaves of this deciduous gymnosperm.
Abstract: Cytokinin conjugates of zeatin, ribosylzeatin, and their respective dihydro derivatives tentatively have been identified as the major cytokinins present in mature Ginkgo biloba L. leaves. Ribosylzeatin was present in higher levels than zeatin and dihydrozeatin. No evidence could be found that 6-(2,3,4-trihydroxy-3-methylbutylamino)purine occurs as a metabolite in the mature leaves. From the available evidence, it is concluded that cytokinin conjugates are probably the major metabolites formed in the leaves of this deciduous gymnosperm.
TL;DR: Root cultures from several species of the Solanaceae were initiated and subcultured on Murashige and Skoog medium without growth regulators and the effect of several concentrations of auxin and cytokinins on the number of shoots generated by two highly responsive species is described.
Abstract: Root cultures from several species of the Solanaceae were initiated and subcultured on Murashige and Skoog medium without growth regulators. Direct shoot regeneration was observed in four different species. The effect of several concentrations of auxin (IAA) and cytokinins (BAP, zeatin) on the number of shoots generated by two highly responsive species (Nicotiana exigua, N. debneyi) is described.
TL;DR: It is found that the auxin-cytokinin ratio in oat stem segments is shifted during tiller, and the glucoside conjugate of Z-r may act as a storage form of cytokinin in quiescent tiller buds.
Abstract: Oat stem segments containing quiescent lateral (tiller) buds during times of strong apical dominance, and growing buds released from this inhibition, were collected for analysis of native auxin and cytokinins. Free IAA and IAA conjugates were determined by a14C-IAA and14C-IBA double isotope dilution assay. Free zeatin (Z), zeatin riboside (Z-r), and their glucoside conjugates were purified from butanol-soluble fractions by means of a cellulose phosphate exchanger and thin-layer chromatography. Hormones were analyzed by gas chromatography and mass spectrometry (GC-MS). Results of these analyses indicate that changes in free and bound IAA within the stem do not correlate well with the release of tiller buds (as brought about by decapitation, gravistimulation, or the emergence of the inflorescence). However, increases in Z-r levels are well correlated with tiller release. The glucoside conjugate of Z-r may act as a storage form of cytokinin in quiescent tiller buds. In light of these results, we find that the auxin-cytokinin ratio in oat stem segments is shifted during tiller