Showing papers on "Zeatin published in 1991"
TL;DR: Transient accumulations of endogenous cytokinins following thermal induction did not appear to alter the plant's preprogrammed pattern of differentiation, and plants exhibited a darker green pigment and continued growth of lateral buds.
Abstract: The cytokinin gene, isopentenyl transferase (ipt), was placed under the control of a heat-inducible promoter from the Drosophila melanogaster hsp70 gene and introduced into Nicotiana plumbaginifolia by cocultivation with Agrobacterium tumefaciens. Transformants were analyzed for organ-specific expression, cytokinin levels and effects on plant development before and after heat induction. The ipt gene transcripts were detected in leaves and stems but not roots of transgenic plants following a 2 hour, 45 °C treatment. Maximum mRNA levels observed occurred 2 hours after heat treatment and 46 hours later were detected only in leaves. Zeatin and zeatinriboside concentrations 2 hours after heat shock ranged from over 900 to 2000 pmol/g, representing a greater than 140- to 200-fold increase over uninduced levels. After 46 hours, approximately 50% of the cytokinins are still present in the leaves as opposed to much reduced levels in the stems. Transgenic plants were greener, shorter, had an underdeveloped root system, reduced leaf width, and increased growth of axillary buds. After a single heat treatment, plants exhibited a darker green pigment and continued growth of lateral buds. Transient accumulations of endogenous cytokinins following thermal induction did not appear to alter the plant's preprogrammed pattern of differentiation.
132 citations
TL;DR: Clonal micropropagation studies with silver maple included experiments with var- ious shoot types, cytokinins, and stock plant maturation levels, which led to successful explant estab- lishment, axillary shoot proliferation, rooting of microshoots, and establishment of plantlets in the greenhouse.
Abstract: Clonal micropropagation studies with silver maple (Acer saccharinum L.) included experiments with var- ious shoot. explant types, cytokinins, and stock plant maturation levels. These trials led to successful explant estab- lishment, axillary shoot proliferation, rooting of microshoots, and establishment of plantlets in the greenhouse. Overall, the best cytokinin tested was the phenylurea derivative TDZ. Shoot proliferation on juvenile explants was poor with kinetin, 2iP, and BA. Only zeatin at 10 µ M was comparable to TDZ. TDZ at 10 nM was optimal for both juvenile and adult nodal explants. Juvenile explants that were held in vitro for 4 months commonly had at least 60 axillary shoots that could be subculture or excised for rooting. Microshoots rooted within 2 weeks. Following rooting, silver maple plantlets could be transplanted into a growing medium and placed directly onto a greenhouse bench. Studies were also conducted on rooting stem cuttings (macropropagation). Single nodes from juvenile plants rooted under intermittent mist, regardless of auxin application; however, shoot-tip cuttings from adult trees rooted best when auxin in ethanol solution was applied. Chemical names used: N- phenyl- N' -1,2,3 -thiadiazol-5-ylurea (thidiazuron, TDZ), N- (2-furanylmethyl)-1H-purin-6-amine (kinetin), isopentenyladenine (2iP), benzyladenine (BA), (E)-2-methyl-4-(1H-purin- 6-ylamino)-2-buten-1-ol (zeatin). Silver maples are valued in the landscape because of their at- tractive foliage with its typical "maple" shape and silvery under- side, the graceful inverted vase shape of the mature trees, rapid growth that provides summer shade in a reasonably short time, and adaptability to a wide variety of soil types. The rapid juvenile growth rate is an attribute where fast shade is required (Dirr, 1977) and is also desirable in species grown under short-rotation culture conditions for the production of energy (Ranney et al., 1986). -Appropriate selection and documentation of performance for woody biomass species that grow well on secondary farmland are important to the energy future of the United States. As fossil fuels become depleted, renewable resources can be used to con- vert the sun's energy into biomass. Silver maple has been se- lected as a model species for research under the Short Rotation Woody Crops (SRWC) program, sponsored by the U.S. Dept. of Energy's Biofuels and Municipal Waste Technology Divi- sion, because of its rapid juvenile growth and other attributes as a potential woody biomass species (Ranney et al., 1986). Research that uses clonal planting stock offers advantages for the study of tree genotypes, as compared to using seedlings from open-pollinated seed orchards. Individual tree seedlings can present problems because the components of genotype and en- vironment are very difficult to separate when one is attempting to interpret the performance of a particular phenotype. Members of clones are genetically identical and, as such, can allow for
116 citations
TL;DR: To determine the utility of zeatin for initiation of diverse genotypes, 96 Vaccinium accessions from the National Clonal Germplasm Repository, representing 22 species and 44 cultivars, were screened using 25C and low light intensity.
Abstract: Explants of mature pot-grown Vaccinium corybosum L. cultivars were tested for initiation of new shoots using two growing conditions and four cytokinin treatments. Initiation tests with 12 genotypes showed significantly higher rates of new shoot growth on modified woody plant (MWPM) medium with 4 mg zeatin/liter at 25C under low light intensity than on any other treatment. Explants at 25C in light with 10 or 15 mg 2iP/liter initiated at a moderate rate, but significantly lower rates were found for all controls and at 4C in darkness. To determine the utility of zeatin for initiation of diverse genotypes, 96 Vaccinium accessions from the National Clonal Germplasm Repository, representing 22 species and 44 cultivars, were screened using 25C and low light intensity. Initiation rates higher than 60% were achieved for 89 of 96 accessions tested. Chemical name used: N6-(2-isopenteny1) adenine (2iP), 6-(4-hy- droxy-3-methylbut-2-eny1amino)purine (zeatin).
80 citations
TL;DR: These embryos are an excellent source of friable embryogenic tissue, in the presence of α–napthaleneacetic acid (NAA) and zeatin, that maintains its regeneration capacity for more than 18 months through periodic subculture in a high 2,4–D/zeatin medium.
Abstract: We report the regeneration of flowering plants in rose (Rosa hybrida L) via somatic embryos continuously produced from long–term cultures of friable embryogenic tissue Filament explants from young flower buds were cultured on a medium based on B5 modified salts giving rise to a semi–hard type callus Globular embryos differentiated from this primary callus in the presence of 2,4–D and zeatin after subculture These embryos are an excellent source of friable embryogenic tissue, in the presence of α–napthaleneacetic acid (NAA) and zeatin, that maintains its regeneration capacity for more than 18 months through periodic subculture in a high 2,4–D/zeatin medium Somatic embryos were periodically isolated from embryogenic tissue and have undergone differentiation, maturation, germination and plantlet development Plantlets obtained through this method developed normally in the greenhouse, similar to the micropropagated controls Upon flowering, these plants proved to be morphologically true to type and displayed the flower color of the donor genotype
77 citations
TL;DR: In vitro plant regeneration has been obtained from Capsicum annuum cvs.
Abstract: In vitro plant regeneration has been obtained from Capsicum annuum cvs. Pico and Piquillo. Shootbuds were induced from hypocotyl and cotyledon segments after 15–20 days of culture on MS basal medium supplemented with IAA and BAP or Zeatin. Shoot-buds grew into rosettes that rooted in MS plus NAA (0.1 mg/l) and IBA (0.05 mg/l) after 15 days. The small plantlets were successfully transferred to pots with a mixture of peat and perlite and maintained under greenhouse conditions. Elongation took place when the plantlets were growing in the greenhouse.
73 citations
TL;DR: A high frequency somatic embryogenesis protocol was developed for biotechnological manipulations of hybrid poplar in which embryogenic callus was derived from non-embryonic explants, and globular-shaped embryo initiation from cell suspension callus occurred after removal of 2,4-D from the culture medium.
62 citations
TL;DR: Combined with HPLC, these two assays together provide a sensitive means for quantifying, and evidence contributing to the identification of, zeatin riboside- and iso-pentenyladenosine-type cytokinins in plant and fungal extracts.
61 citations
TL;DR: Adventitious shoots were regenerated from axillary bud explants of 15 carnation cultivars but the use of leaf and stem explants was not succesful, largely due to explant senescence in the presence of benzyladenine, kinetin and, to a lesser extent zeatin.
53 citations
TL;DR: Cytological examinations of incubated anthers and root tips of regenerated plants indicated that the anther calli were derived from microspores, and factors affecting the regeneration capacity of linseed anther culture were investigated.
Abstract: The objective of this study was to investigate factors affecting the regeneration capacity of linseed anther culture. Four different environmental conditions in a phytotron were tested with regard to their effects on anther donor plants of cv. ‘Hella’. Anther response and shoot regeneration from anther callus was maximal when donor plants were grown in a 16 hrs-day at 14°C day/8°C night temperature. Anthers of four linseed genotypes were cultured on different media. Maximum shoot regeneration was achieved when the induced calli were transferred onto a modified N6 medium containing zeatin (1 mg l-1). Most of the calli regenerated shoots in the second subculture on regeneration media. Shoots were rooted on modified B5 or MS media containing NAA (0.1 mg l-1). Cytological examinations of incubated anthers and root tips of regenerated plants indicated that the anther calli were derived from microspores.
50 citations
TL;DR: Lychee (Litchi chinensis) has been analyzed for cytokinins in buds before and after flower bud differentiation, and the increase in endogenous cytokinin levels during Flower bud differentiation may be correlative rather than the cause of flower bud initiation.
Abstract: Lychee (Litchi chinensis) has been analyzed for cytokinins in buds before and after flower bud differentiation, using reversephase high performance liquid chromatography in combination with Amaranthus bioassay and gas chromatography-mass spectrometry-selected ion monitoring. Four cytokinins, zeatin, zeatin riboside, N6-(δ2-isopentenyl)adenine, and N6-(δ6-isopentenyl) adenine riboside, were detected in buds. There was an increase of cytokinin activity in the buds during flower bud differentiation. In dormant buds, the endogenous cytokinin content was low, and the buds did not respond to exogenous cytokinin application. Application of kinetin promotes flower bud differentiation significantly after bud dormancy. These results are interpreted as an indication that the increase in endogenous cytokinin levels during flower bud differentiation may be correlative rather than the cause of flower bud initiation.
46 citations
TL;DR: Histological studies revealed that active cell divisions occurred in subepidermal and cambial tisue during the first week of culture, and well-developed shoot apices and leaf structures were observed on 50% of the explants 28 days after culture initiation.
Abstract: Regeneration of de novo shoots, roots and flowers has been obtained on inflorescence explants of tomato (Lycopersicon esculentum Mill.). Indole-3-acetic acid (IAA), indole-3-butyric acid (IBA) and α-naphthaleneacetic acid (NAA) were added in a 3×3×3 factorial combination with kinetin, each at 0.001, 0.1 and 10 μM concentrations. Direct shoot formation occurred on media with 10 μM kinetin and 0.001 μM IAA or NAA. Root formation was observed on media with 0.1–10 μM IAA, IBA or NAA. Flower formation occurred on elongated shoots with several leaves on media with 10 μM IAA and 0.1 μM kinetin. Shoot organogenesis was increased by substituting 10 μM zeatin or N6-benzyladenine (BA) for kinetin. Eleven tomato cultivars were tested for their ability to undergo de novo shoot regeneration on the improved medium. All tomato cultivars were capable of shoot morphogenesis with a mean number of shoots per explant that ranged from 1.3 (‘Red Alert’) to 5.3 (‘Large Red Cherry’). Histological studies revealed that active cell divisions occurred in subepidermal and cambial tisue during the first week of culture. Meristematic centers of dividing cells were evident by day 14, and well-developed shoot apices and leaf structures were observed on 50% of the explants 28 days after culture initiation.
TL;DR: The apparent capacity of the alternative pathway, as measured after blocking of the cytochrome pathway by cyanide, was inversely proportional to the content of endogenous cytokinins, which were dependent on the kind of synthetic cytokinin present in the culture medium.
Abstract: Respiration patterns and growth of cytokinin-dependent cell suspensions ofBeta vulgaris L., precultured in media with or without three different synthetic cytokinins [benzyladenine (BA), kinetin (KIN), and thidiazuron (TDA)], were compared. The content of endogenous cytokinins, especially zeatin and isopentenyladenine, as well as the dry mass yield, were dependent on the kind of synthetic cytokinin present in the culture medium and decreased in the following order: thidiazuron, kinetin, benzyladenine, no cytokinin. The apparent capacity of the alternative pathway, as measured after blocking of the cytochrome pathway by cyanide, was inversely proportional to the content of endogenous cytokinins. Some synthetic cytokinins (e.g., benzyladenine), when exogenously applied, are known to inhibit selectively the alternative pathway. However, this does not necessarily imply that the mechanism of action of endogenous cytokinins on the respiration pattern is limited to a single effect on the alternative pathway. Multiple effects on oxidative processes cannot be excluded.
TL;DR: Node-derived shoot cultures of Eucalyptus regnans were established from in vitro grown seedlings on Murashige and Skoog basal medium supplemented with 0.5 mg L-1 (2 μm) zeatin and 0.3 μm napthaleneacetic acid to develop an efficient method for in vitro rooting.
Abstract: Node-derived shoot cultures of Eucalyptus regnans were established from in vitro grown seedlings on Murashige and Skoog basal medium supplemented with 0.5 mg L-1 (2 μm) zeatin and 0.05 mg L-1 (0.3 μm) napthaleneacetic acid. A double sterilisation method was essential to obtain clean material from seed. Microcuttings from established cultures were used to develop an efficient method for in vitro rooting. Rooting was best after a 7 day pulse on 20 mg L-1 (98 μm) indolebutyric acid. Hoagland's or Woody Plant Medium supported better rooting than MS basal medium and rooting was significantly enhanced by subculture to activated charcoal after the auxin pulse. Carbohydrate (sucrose or glucose) was essential for rooting while high light intensity was inhibitory. Optimal light conditions were a 12 h day (17 W m-2). In all, 90% of plantlets established in the nursery survived the winter.
TL;DR: Cultures responded in a dose-dependent manner to 2iP but exhibited broad dose-response curves to kinetin, BAP, zeatin, and thidiazuron, and NAA addition resulted in increased leaf and internodal lengths, but reduced the number of leaves per node and the rhizome biomass.
Abstract: Axenic tissue cultures ofRuppia maritima L. were established and propagated clonally in vitro from terminal rhizome segments collected from Tampa Bay, Florida, USA. Cultures were maintained in a base medium consisting of synthetic seawater supplemented with half-strength Murashige and Skoog salts and 1% sucrose at pH 5.6. The effects of five cytokins [6-furfurylaminopurine (kinetin), 6-benzylaminopurine (BAP), 2-isopentyladenine (2iP), 6-(4-hydroxy-3-methyl-but-2-enylamino) purine (zeatin), andn-phenyl-n′-1,2,3-thidiazol-5′yl urea (thidiazuron)] and one auxin [napthalene acetic acid (NAA)] on explant growth and development were investigated. Cytokinin additions resulted in a 3- to 4-fold increase in nodal production, branching, and biomass ofR. maritima after 12 wk in culture. Cultures responded in a dose-dependent manner to 2iP but exhibited broad dose-response curves to kinetin, BAP, zeatin, and thidiazuron. NAA addition resulted in increased leaf and internodal lengths, but reduced the number of leaves per node and the rhizome biomass. The addition of NAA almost completely suppressed root growth in media without cytokinins and had an antagonistic effect on nodal production and branching in cytokinin-supplemented media.
TL;DR: Somatic embryos were induced on the roots of Camellia japonica L. plantlets raised in vitro, the maintenance of embryogenic capacity through secondary embryogenesis, and germination of somatic embryos into plants.
Abstract: Somatic embryos were induced on the roots of Camellia japonica L. plantlets regenerated from an in vitro clone of juvenile origin. The embryos appeared to differentiate from epidermic cells and to be connected with the root via a few parenchymatous cells. Somatic embryogenesis occurred on basal medium and with or without various combinations of zeatin, BA, and IBA. Secondary embryos were induced on cotyledons and/or hypocotyl regions of somatic embryos. Two morphological types of somatic embryos were developed, seed-like and bud-like types, and their formation was influenced by the presence of BA in the medium. Embryogenic capacity has been maintained for more than 24 months by subculturing secondary embryos at 7- to 8-week intervals. The best gibberellin/auxin com- bination for inducing the germination of isolated somatic embryos was GA 3 at 5 mg·liter -1 GA3 and IAA at 1 mg·liter -1 . P1antlets were successfully established in planting medium and have continued to grow in a greenhouse. 8-methylenegibb-3-ene-1,10-dicarboxylic acid l,4a-lactone (GA 3); 1 H -indole-3-acetic acid (IAA); 1 H- indole-3-butyric acid (IBA); 2-methyl-4-(1 H- purine-6-ylamino)-2-buten-l-ol (zeatin). Shoot cultures based on axillary branching remains the preeminent in vitro method of camellia clonal multiplication from seedling-derived (Samartin et al., 1986) and from mature explants (San-Jose and Vieitez, 1990; Vieitez et al., 1989a, 1989b). Somatic embryogenesis might be an alternative mass propagation system. Somatic embryogenesis has been achieved from zygotic embryos of some Camellia spp. (Kate, 1989), but its extension to a wider range of older explants would be desir- able. We found no reports of the regeneration of camellias by somatic embryogenesis from plantlets cultured in vitro. Regeneration of plants from root tissue is not common. How- ever, somatic embryos have been obtained on callus derived from intact roots of Prunus incisa × P. serrula and horse-chest- nut (Aesculus hippocastanum L.) (Druart, 1981). Also, em- bryoid structures were induced on callus nodules developed on the roots of micropropagated cherry rootstock Colt (Prunus av- ium × P. pseudocerasus) plantlets (Jones et al., 1984). McCown (1986) developed highly competent embryogenic and organo- genic systems based on the formation of nodules on the roots of Populus shoots rooted in vitro. We report the induction of somatic embryos from roots of Camellia japonica L. plantlets raised in vitro, the maintenance of embryogenic capacity through secondary embryogenesis, and germination of somatic embryos into plants.
TL;DR: The effects of nitrogen source on development, endogenous cytokinin levels and chlorophyll content in protocorms of Epidendrum fulgens, as well as cytokinIn content of matura seeds, were studied.
TL;DR: Regenerated plants were cytologically and phenotypically stable and rapid multiplication of embryos was secured on transfer to a medium containing a different source of nitrogen and a low level of gibberellic acid.
Abstract: Somatic embryogenesis and plantlet formation were obtained from callus derived from the subapical region of spears of Asparagus cooperi Baker. Callus was obtained in Murashige and Skoog's medium supplemented with 1-naphthaleneacetic acid and kinetin. Increase in the concentration of potassium nitrate in subsequent subcultures resulted in the formation of embryos. Rapid multiplication of embryos was secured on transfer to a medium containing a different source of nitrogen and a low level (0.01 mg/1) of gibberellic acid. Media containing zeatin or gibberellic acid led to the formation of complete plantlets from embryos. Regenerated plants were cytologically and phenotypically stable.
TL;DR: Gene-specific hybridization and sequence comparisons failed to detect any homology of IC3342 DNA to Agrobacterium tumefaciens or Pseudomonas savastanoi genetic loci encoding enzymes involved in cytokinin biosynthesis.
Abstract: A uniquely abnormal shoot development (shoot tip-bending, leaf curling, release from apical dominance, and stunted growth) in pigeonpea (Cajanus cajan Millsp) induced by a nodulating Rhizobium strain, IC3342, is thought to be due to a hormonal imbalance. Amaranthus betacyanin bioassay indicated that xylem exudate and leaf extracts from pigeonpea plants with Rhizobium-induced leaf curl symptoms contained high concentrations of cytokinin relative to those in normal plants. Radioimmunoassay (RIA) of samples purified with high performance liquid chromatography revealed that zeatin riboside (ZR) and dihydrozeatin riboside (DZR) concentrations in xylem sap from plants with leaf curl symptoms were 7 to 9 times higher than those in the sap from symptomless, nodulated plants. The sap from symptomless plants nodulated by a Curl− mutant had ZR and DZR concentrations comparable to those in the normal plant sap. RIA indicated that the respective concentrations of zeatin and N6-isopenteny-ladenine in culture filtrates of the curl-inducing strain IC3342 were 26 and 8 times higher than those in filtrates of a related normal nodulating strain (ANU240). Gas chromatographic-mass spectrometric analyses revealed similar differences. Gene-specific hybridization and sequence comparisons failed to detect any homology of IC3342 DNA to Agrobacterium tumefaciens or Pseudomonas savastanoi genetic loci encoding enzymes involved in cytokinin biosynthesis.
TL;DR: In addition to differences in the number of buds induced at three months on the two media, buds induced on WPM were visually more uniform, less vitrified and elongated faster, and had a higher percentage of genotypes surviving at six-months when compared with epicotyl explants.
Abstract: Picea glauca (white spruce) zygotic embryos and one-week-old-seedling epicotyl explants were placed on either Woody Plant Medium (WPM) or half-strength Schenk & Hildebrandt (1/2S&H) medium supplemented with varying levels of benzyladenine (BA) (0.1, 1.0, 10, 50, 100 μM), zeatin (10, 50, 100 μM) or thidiazuron (TDZ) (0.01, 0.1 μM). In addition to differences in the number of buds induced at three months on the two media, buds induced on WPM were visually more uniform, less vitrified and elongated faster. On 1/2S&H supplemented with BA, maximum bud induction from embryos occurred on 1.0 μM BA with 0.01 μM TDZ with higher BA concentrations inhibitory to bud induction. In contrast, on WPM there was little difference in the number of buds induced from embryos placed on 10, 50 and 100 μM BA with or without TDZ. One-week-old-seedling epicotyl explants required higher BA levels on 1/2S&H, as bud induction at three months was greatest at 10 μM BA. On WPM, as with the embryos, there were only minor differences in the number of buds induced from epicotyl explants on the various BA levels. Zeatin was more effective at inducing buds than BA with both media. From embryos, bud induction was greatest on 50 or 100 μM zeatin without TDZ and 50 or 100 μM zeatin with or without TDZ on 1/2S&H and WPM respectively. From epicotyl explants on 1/2S&H, there was little difference in the number of buds induced with the zeatin concentrations used, while with WPM, 50 and 100 μM zeatin induced the greatest number of buds. Interestingly, with BA, the epicotyl explants needed a higher level than the embryos for maximal response, while with zeatin, the level was the same for both embryos and epicotyl explants. Long-term (six month) survival was higher on WPM than with 1/2S&H. Additionally, embryos had a higher percentage of genotypes surviving at six-months when compared with epicotyl explants. For overall survival and development of the buds, 50 μM zeatin with 0.01 μM TDZ was the best treatment tested.
TL;DR: Transformation and plant regeneration of broccoli cv.
Abstract: Transformation and plant regeneration of broccoli cv. Early De Cico were studied using Agrobacterium rhizogenes-vector system. Hairy roots were induced from inoculated leaf tissue within 3 weeks whereas only callus was induced from uninoculated tissue. Four root clones out of 18 grew well on the hormone-free Murashige-Skoog (MS) medium. Each root clone was sectioned and cultured on the medium supplemented with 0.1 mg•liter-1 or 1 mg•liter-1 α-naphthaleneacetic acid (NAA) in combination with 1 mg•liter-1 or 5 mg•liter-1 zeatin. Two root clones out of 4 produced adventitious buds on the 5 mg•liter-1 zeatin-containing medium.The other two clones produced only callus. Mannopine, which is indicative that genetic transformation had occurred, was detected in the regenerated shoots and in one callus from a root clone. The compound was not detected from another callus and in other shoots of the control mother plants.
TL;DR: In this article, a search for inhibitors of this metabolism, the following compounds were found to be effective: (a) 6-benzylamino-2-(2-hydroxyethylamino)-9-methylpurine, (b) 3-isobutyl-1-methylxanthine; (c) papaverine;(d) theophylline, caffeine; and (f) theobromine.
Abstract: Cytokinins are deactivated in radish cotyledons by conversion to 7- and 9-glucosides. In a search for inhibitors of this metabolism, the following compounds were found to be effective: (a) 6-benzylamino-2-(2-hydroxyethylamino)-9-methylpurine; (b) 3-isobutyl-1-methylxanthine; (c) papaverine; (d) theophylline; (e) caffeine; and (f) theobromine. The order of effectiveness was: (a)>(b)=(c)>(d)=(e)=(f). While the methylxanthines (b) and (d) inhibited formation of both 7- and 9-glucosides of 6-benzylaminopurine (BAP) approximately equally, compounds (a) and (c) preferentially inhibited formation of BAP 9-glucoside. Inhibition of BAP glucoside formation by (a) at 1.3 mM elevated the level of free BAP and BAP nucleotide 23- and 94-fold, respectively. While abscisic acid (ABA) suppressed conversion of zeatin riboside to zeatin 7-glucoside in radish cotyledons, it did not inhibit conversion of BAP to glucosides. Hence, ABA probably does not inhibit the glucosylating enzymes directly but rather reduces the availability of free zeatin when zeatin riboside is supplied. Auxins and nutrient supply did not affect conversion of zeatin riboside to zeatin 7-glucoside. Relative to cotyledons developed in light, those developed in darkness had a reduced capacity to convert zeatin riboside to zeatin 7-glucoside. The results presented have identified types of chemical structures which could be developed to provide more effective inhbitors of cytokininN-glucosylation.
Journal Article•
TL;DR: The cytokinin level in xylem sap of pigeonpea plants inoculated with strain IC3342 was markedly greater than that in plants inoculation with a normal nodulating strain, which appears to provide the first unambiguous identifications of cytokinins in Rhizobium culture media.
Abstract: Two Rhizobium strains were cultured on a defined medium; one was a normal strain of the cowpea group (ANU240) while the other (IC3342) was an unusual but related strain of the same group which induced abnormal shoot development, including proliferation of lateral buds, in nodulated plants. Culture supernatants were examined for the presence of cytokinins by mass spectrometry using deuterium-labelled internal standards and by radioimmunoassay. In culture supernatants of both strains a range of cytokinins was detected and quantified, but N6-(2-isopentenyl)adenine (iP) and zeatin (Z) were the dominant cytokinins. The levels of Z and iP in supernatants of strain IC3342 were 26 and 8 times, respectively, those in supernatants of the strain ANU240. These results appear to provide the first unambiguous identifications of cytokinins in Rhizobium culture media. The cytokinin level in xylem sap of pigeonpea plants inoculated with strain IC3342 was markedly greater than that in plants inoculated with a normal nodulating strain. The abnormal proliferation of lateral buds in the former plants is probably linked to the elevation of cytokinin level in xylem sap caused by strain IC3342.
TL;DR: Similar to thidiazuron, isopentenyladenine-induced defoliation was inhibited by aminoethoxyvinylglycine, and the effect was restored by 1-aminocyclopropane-1-carboxylic acid.
Abstract: Cytokinins of the urea and adenine type induced leaf abscission in young cotton (Gossypium hirsutum) plants in the following order of activity: N-phenyl-N′-1,2,3-thiadiazol-5-ylurea (thidiazuron) » N-phenyl-N′-(2-chloro-4-pyridyl)urea > isopentenyladenine ≥ 6-benzyladenine > zeatin = dihydrozeatin > kinetin. It is suggested that ethylene production is implicated in this response because it was stimulated by the compounds in cotton leaf discs with nearly the same effectiveness. Moreover, similar to thidiazuron (JC Suttle [1985] Plant Physiol 78: 272-276), isopentenyladenine-induced defoliation was inhibited by aminoethoxyvinylglycine, and the effect was restored by 1-aminocyclopropane-1-carboxylic acid.
01 Jan 1991
TL;DR: Preliminary genetic data do not support nod gene involvement in cytokinin synthesis under noninducing conditions, and growth pouch experiments showed increased nodulation of soybean plants treated with trans-zeatin.
Abstract: Culture media from a number of rhizobial strains, including the type-strains of 8 major cross-inoculation groups, were analyzed for cytokinin content. Cytokinins were partially purified by chromatography on Amberlite XAD-2, then on Sephadex LH-20. The tobacco callus assay, HPLC and/or immunoassay were used for cytokinin analysis. All strains of rhizobia examined produced at least 2 cytokinin-active compounds, with total cytokinin activity ranging from 1 to several µg kinetin equivalents per liter of culture filtrate. There were both qualitative and quantitative differences between rhizobial species. The cytokinin profiles of most strains included zeatin or its derivatives. Addition of adenine, seed extract or flavonoid inducers to the culture medium altered cytokinin synthesis. Preliminary genetic data do not support nod gene involvement in cytokinin synthesis under noninducing conditions. Growth pouch experiments showed increased nodulation of soybean plants treated with trans-zeatin.
TL;DR: Increases in the amounts of cytokinin-like substances, particularly zeatin and zeat in riboside, attributed to pathogen influence are suggested to be involved in infection and pathogenicity of H. teres.
Abstract: Infection sites/green islands were formed in host leaf tissue infected with drops of H. teres. They exhibited higher cytokinin-like activity, sugar and starch than their surrounding tissue and tissue under water drops. The cytokinin-like activity at the infection sites increased from 24 to 72 h of incubation. However, the cytokinin-like activity of the tissue surrounding the infection drops and the tissue under water drops fell from 24 to 72 h incubation. The culture filtrate extracts of the fungus also produced cytokinin-like activity which increased from 1 to 10 days incubation. Application of this culture filtrate extract evoked green island formation. Application of kinetin to host leaves duplicated the green island effect. Thin-layer chromatographic fractions of the tissue extracts and the culture filtrate extracts revealed that a major portion of cytokinin-like activity corresponded to zeatin and zeatin riboside. The presence of zeatin and zeatin riboside (both in tissue and culture filtrate extracts) was confirmed by high performance liquid chromatography. Increases in the amounts of cytokinin-like substances, particularly zeatin and zeatin riboside, attributed to pathogen influence are suggested to be involved in infection and pathogenicity of H. teres.
TL;DR: The data suggest that bud culture can be used to monitor and detect physiological and hormonal processes that control forest tree growth, and that direct supply of growth regulators can induce growth in otherwise quiescent buds.
TL;DR: A high frequency of adventitious bud formation occurred on Murashige and Skoog's agar medium containing 10 μM zeatin and 0.1 μM 3-indoleacetic acid (IAA).
TL;DR: Two varieties of Euphorbia pulcherrima Willd.
TL;DR: Cultured leaf explants obtained from 36 accessions of the wild tomato species, Lycopersicon hirsutum Humb.
Abstract: Cultured leaf explants obtained from 36 accessions of the wild tomato species, Lycopersicon hirsutum Humb. and Bonpl., were evaluated for morphogenic capacity in response to three cytokinins (zeatin, BA, and kinetin) in combination with IAA. Media containing 0.1 μM IAA plus 4.6 or 9.2 μm zeatin were optimal for shoot induction. Cotyledon explants were superior to true leaf explants for obtaining shoot formation
TL;DR: In contrast to 2′ deOZR, which showed a very low cytokinin activity, 1′MeZ and 1″MeZR displayed a higher stimulating potency of chlorophyll synthesis when compared to zeatin andZeatin riboside, respectively.