Showing papers on "Zeatin published in 1996"
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TL;DR: Higher regeneration from hypocotyl and petiole explants was obtained on BA with IBA than on zeatin- or kinetin-supplemented media, and direct adventitious shoot bud induction was recorded highest on MS medium.
Abstract: Techniques for the regeneration of Jatropha curcas L. from various explants have been developed. Regeneration from hypocotyl, petiole and leaf explants was evaluated on a range of concentrations of zeatin, kinetin and N6 benzyladenine (BA) either singly or in combination with indole-3-butyric acid (IBA). Higher regeneration from hypocotyl and petiole explants was obtained on BA with IBA than on zeatin- or kinetin-supplemented media. Leaf discs from the third expanding leaf exhibited higher regeneration potential than those from the fourth leaf. Independent of the explant type, direct adventitious shoot bud induction was recorded highest on MS medium with 2.22 μM BA and 4.9 μM IBA. Although the same BA concentration but with reduced IBA concentration (0.49 μM) proved effective in callus mediated regeneration from hypocotyl and leaf explants, the petioles required lower concentrations of the two growth regulators (0.44 μM BA and 0.49 μM IBA). Regenerated shoots could be rooted on growth regulator-free gelled full-strength MS medium. Following simple hardening procedures, the in vitro-raised plants could be transferred to soil and grown to maturity in the field.
182 citations
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TL;DR: It is suggested that zeatin‐ and dihydrozeatin‐type cytokinins might play a specific regulatory role in the progression of the plant cell cycle.
153 citations
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TL;DR: Phytagar tissue culture grade proved superior to other agars tested, increasing bud induction frequency from 0-33% to 80–93% and eliminating explant hyperhydricity.
Abstract: Chile pepper (Capsicum annuum L.) plants were regenerated from cotyledon explantsin vitro in four major stages: bud induction, bud enlargement, shoot elongation, and root development. Bud induction medium contained 0.5 mg/L (2.9μM) indole-3-acetic acid and 2 mg/L (8.9 μM) N6-benzyladenine. Bud enlargement occurred, and an occasional shoot appeared when medium with 2 mg/L (6μM) gibberellic acid, 2 mg/L (8.9 μM) N6-benzyladenine, and 5 mg/L (29.4 μM) silver nitrate was used. Most shoots elongated after placement on a third medium without plant growth regulators or on fresh plates of bud enlargement medium. Incubations were for 2, 2, and 4 weeks, respectively, at 28.5°C and continuous light. Treatment with silver nitrate was necessary for multiple shoot production and elongation to occur in the third culture stage and was most effective when present in the second-stage medium but not in the bud induction medium. Sixteen to 26% of the shoots rooted in medium with 1 mg/L (5.4 μM) 1-naphthaleneacetic acid after 1 month. Additional shoots transferred to a second rooting medium with 0.1 or 1.0 mg/L (0.54 or 5.4 μM) 1-naphthaleneacetic acid developed roots, increasing the overall rooting efficiency to 70–72%. Most rooted shoots grew well and produced viable seeds when grown in the greenhouse. Other cytokinins tested for plant regeneration were zeatin and thidiazuron. Zeatin induced few shoots and fewer well-developed plants. Thidiazuron induced multiple shoots 4 months after culture began, but many were small and did not elongate further. Phytagar tissue culture grade proved superior to other agars tested, increasing bud induction frequency from 0-33% to 80–93% and eliminating explant hyperhydricity.
118 citations
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TL;DR: Six commercially used seaweed extracts were tested for cytokinin- and auxin-like activity using the soybean callus bioassays and the mung bean rooting bioassay respectively and improved rooting of mung beans was found.
Abstract: Six commercially used seaweed extracts were tested for cytokinin- and auxin-like activity using the soybean callus bioassay and the mung bean rooting bioassay respectively. All the seaweed extracts tested showed cytokinin-like activity. Seamac caused the most callus growth with activity being concentrated at R
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0.9 which co-chromatographed withiso-pentenyladenine and its riboside. The other five seaweed extracts yielded activity at R
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0.7–0.8. This co-chromatographed with zeatin and zeatin riboside. All the seaweed extracts tested improved rooting of mung beans. Kelpak made fromEcklonia maxima (Osbeck) Papenf. gave the best rooting response.
115 citations
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TL;DR: Improved transformation efficiencies were obtained by combining the hormones thidiazuron and zeatin and by using leaf explants from in vitro grown shoots not older than 4 weeks after multiplication, and attempts to use phosphinothricin acetyl transferase as a selectable marker were not successful.
Abstract: We have previously developed a protocol for efficient gene transfer and regeneration of transgenic calli following cocultivation of apple (cv. Jonagold) explants with Agrobacterium tumefaciens (De Bondt et al. 1994, Plant Cell Reports 13: 587–593). Now we report on the optimization of postcultivation conditions for efficient and reproducible regeneration of transgenic shoots from the apple cultivar Jonagold. Factors which were found to be essential for efficient shoot regeneration were the use of gelrite as a gelling agent and the use of the cytokinin-mimicing thidiazuron in the selective postcultivation medium. Improved transformation efficiencies were obtained by combining the hormones thidiazuron and zeatin and by using leaf explants from in vitro grown shoots not older than 4 weeks after multiplication. Attempts to use phosphinothricin acetyl transferase as a selectable marker were not successful. Using selection on kanamycin under optimal postcultivation conditions, about 2% of the leaf explants developed transgenic shoots or shoot clusters. The presence and expression of the transferred genes was verified by β-glucuronidase assays and Southern analysis. The transformation procedure has also been succesfully applied to several other apple cultivars.
91 citations
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TL;DR: The results suggest that, at least in oat and possibly in wheat, zeatin-type bases, ribosides and O-glucosides supplied to the leaf in xylem sap are likely to play a role in regulating transpiration in vivo.
Abstract: This study was conducted lo determine whether naturally occurring xylem cytokinins, when supplied to leaves via the xylem at approximately endogenous concentrations, increase transpiration and delay senescence in selected monocot species (oat and wheat). The concentrations of some of the major cytokinins (zeatin, dihydrozeatin, ciszeatin and their ribosides, the O-glucosides and nucleotides) were determined in the xylem exudate of oat and wheat seedlings by radioimmunoassay. Evidence is presented that the small volume of exudate (4–5 mm3) collected per plant was xylem sap in transit at the time of shoot excision. Using the data on cytokinin levels, the individual bases and ribosides (and a base/riboside mixture), at multiples of concentrations determined in xylem sap, were tested in transpiration and senescence bioassays. The individual O-glucosides (and mixtures of the O-glucosides) were similarly tested at (i) multiples of the molar concentrations of the corresponding bases and ribosides, and/or at (ii) multiples of the endogenous concentrations. Similarly, zeatin and dihydrozeatin nucleotides were tested at multiples of the molar concentration of zeatin riboside and, in some instances, at multiples of endogenous concentrations.
Our results suggest that, at least in oat and possibly in wheat, zeatin-type bases, ribosides and O-glucosides supplied to the leaf in xylem sap are likely to play a role in regulating transpiration in vivo. O-glucosides in oat xylem sap may be important regulators of leaf senescence in the intact plant. The nucleotides were present in xylem sap at lower concentrations than most of the bases, ribosides and O-glucosides. The nucleotides appear likely to play a lesser role than the bases, riboside and O-glucosidcs in controlling transpiration and senescence in the intact plant.
80 citations
01 Jan 1996
TL;DR: In this paper, the authors found that Phanerochaete chrysosporium ME446 synthesized the growth substances IAA, GA3, ABA and zeatin as primary and secondary metabolites.
Abstract: Besides higher plants, there is evidence that fungi synthesize IAA, GA3, ABA and zeatin as well. According to our findings, Phanerochaete chrysosporium ME446 synthesized the growth substances IAA, GA3, ABA and zeatin as primary and secondary metabolites. Recovery of IAA, GA3, ABA and zeatin were respectively 55.5±10%, 74.6±8%, 51.6±10% and 56.63±6%. We have demonstrated that one can use the same extraction method to determine the different growth substances at the same time, thus this method will be primary and the only method that is applied in this research area.
72 citations
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TL;DR: Several culture conditions were examined for promoting efficient plant regeneration from explants of Gentiana and WSP-3 was very superior on MS medium, compared to B5 medium, supplemented with four cytokinins (TDZ, 4PU-30, BA and zeatin).
Abstract: Several culture conditions were examined for promoting efficient plant regeneration from explants of Gentiana. Adventitious shoot regeneration from leaf explants of cv. WSP-3 was very superior on MS medium, compared to B5 medium, supplemented with four cytokinins (TDZ, 4PU-30, BA and zeatin). An auxin / cytokinin combination was required for regeneration. TDZ was the most effective cytokinin, while NAA was more effective than IAA or 2,4-D. Optimum conditions for regeneration from explants (leaf, stem and root) of cv. WSP-3, evaluated in terms of regeneration frequency and number of regenerated shoots per explant, were TDZ and NAA in combination, 5–10 mg/l and 0.1 mg/l for leaf and stem explants, and 10 mg/l and 1 mg/l for root explants, respectively. Application of these conditions to eight other commercial cultivars resulted in 30–100% regeneration from leaf explants. The number of chromosomes in each of ten regenerated plants of each cultivar was diploid, 2n=26. Shoots regenerated in vitro were rooted in phytohormone-free medium and transferred to soil.
68 citations
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TL;DR: It is hypothesised that an increase in Z is the critical change in cytokinin metabolism required for the initiation of cell division and fruit growth, and there was a decrease in the endogenous cytokinIn concentration.
Abstract: The significance of changes in cytokinin content during early fruit growth was examined in the kiwifruit (Actinidia deliciosa var. deliciosa cv. Hayward). Fruit growth was modified by the reduction of seed number or by the application of the synthetic phenylurea cytokinin N-(2-chloro-4-pyridyl)-N'-phenylurea (CPPU). The influence of these treatments on cell division was monitored by flow cytometry and changes in the endogenous cytokinins were measured at days 10 and 20 after anthesis, using high-performance liquid chromatography and radioimmunoassay. Total cytokinin levels appeared not to be limiting growth since the highest total cytokinin concentration was detected in unpollinated fruit, which abscised by day 25 after anthesis. However, compared with control fruit which had the highest concentration of zeatin (Z) 10 days post anthesis, Z levels were low in unpollinated fruit. It is hypothesised that an increase in Z is the critical change in cytokinin metabolism required for the initiation of cell division and fruit growth. The synthetic cytokinin CPPU promoted fruit development, but there was a decrease in the endogenous cytokinin concentration. Zeatin was not detected in CPPU-treated fruit. Cell division was reduced in unpollinated fruitlets but there was no significant difference (P > 0.05) between the other treatments. Differences in final fruit size appeared to be due to cell expansion.
60 citations
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TL;DR: In vitro plant propagation was developed for seedling shoot tips, leaf axils, and cotyledonary nodes of cashew, Anacardium occidentale and the highest frequency of rooted shoots was obtained by treating shoots with the bacterium, Agrobacterium rhizogenes.
Abstract: In vitro plant propagation was developed for seedling shoot tips, leaf axils, and cotyledonary nodes of cashew, Anacardium occidentale. Factors affecting multiplication rate included age of explant source, explant type, medium composition, light requirements, and transfer frequency. Cotyledonary nodes produced more buds than other explant types. Nodes had a 90% viability when transferred daily to fresh medium containing activated charcoal for 7 d while exposed to continuous dark. Cultures were then exposed to low light illumination with weekly transfers. The phytohormone composition producing the most buds was 2.32 μM kinetin, 9.12 μM zeatin and 4.40 μM BA. The highest frequency of rooted shoots was obtained by treating shoots with the bacterium, Agrobacterium rhizogenes. Plants also were recovered by induction of roots using auxin treatment on propagated shoots.
58 citations
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TL;DR: The ploidy of 12 randomly selected regenerants was assessed by chromosome counts in root tips and showed no segregation for morphological traits in the progeny, suggesting that they were spontaneously doubled haploids.
Abstract: Morphogenic calli were obtained efficiently from ab initio cultures of isolated microspores in eggplant. Initial culture of freshly isolated microspores in sucrose-free medium at high temperature (35°C) for 3 d was a prerequisite for callus induction. The microspores were re-cultured in modified NLN medium containing 2% sucrose and phytohormones (NAA 0.5 mg l(-1), BA 0.5 mg l(-1)) in the dark. After 4 weeks of re-culture, small calli derived from microspores were transferred to MS medium containing 4 mg l(-1) zeatin and 0.2 mg l(-1) IAA for shoot regeneration. The ploidy of 12 randomly selected regenerants was assessed by chromosome counts in root tips. Only one of the regenerants was haploid, 7 were diploid, 3 were triploid and one was tetraploid. The diploids set seeds after self-pollination and showed no segregation for morphological traits in the progeny, suggesting that they were spontaneously doubled haploids.
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TL;DR: A possible critical role for purines in embryogenesis from geranium hypocotyl tissues is indicated as the conversion of cytokinin bases to their corresponding nucleotide forms was not evident as the levels of isopentenyl adenine and zeatin increased during the second day of culture.
Abstract: Somatic embryogenesis in geranium (Pelargonium x hortorum Bailey cv. Scarlet Orbit Improved) was achieved by culturing hypocotyl sections on Murashige and Skoog (1962) (MS) medium containing 10 μM thidiazuron (TDZ) (induction medium) for 3 days and subsequently transferring the sections onto a basal medium lacking any plant growth regulators (expression medium). Addition of the purine analogue 2,6-diaminopurine (DAP) to the somatic embryo induction medium completely inhibited the embryogenic response as well as chlorophyll accumulation without affecting enlargement of the treated tissues. Addition of 20 μM adenine sulphate to the expression medium, i.e during embryo growth and development phase, completely reversed the DAP-induced inhibition of the embryogenic response while addition during the induction phase caused only a 50% reversal of the inhibition. Analysis of endogenous levels of plant growth substances indicated that TDZ alone elevated the levels of auxins, cytokinins and abscisic acid while the presence of DAP during the induction phase caused a further increase in the levels of adenine and adenosine. These findings indicate a possible critical role for purines in embryogenesis from geranium hypocotyl tissues. However, the conversion of cytokinin bases to their corresponding nucleotide forms was not evident as the levels of isopentenyl adenine and zeatin increased during the second day of culture.
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TL;DR: The results from these experiments revealed that the morphogenetic pathway (shoot versus root differentiation) can be manipulated on flax explants by raising the 2,4-D level from 0.05 to 3.2 mg l−1 in the induction medium.
Abstract: The effects of plant growth regulators (PGR) on calli induction, morphogenesis and somatic embryogenesis of flax were studied. The organogenic and callus formation capacity were assessed for different types of source explants. Root and shoot explants were equally good material for calli production but the former produced calli without shoot regeneration capacity. Under the experimental conditions tested, 2,4-dichlorophenoxyacetic acid (2,4-D) + zeatin was the most efficient PGR combination on calli induction and biomass production. The calli were green but with no rhizogenic capacity. In contrast, and at similar concentrations, indole-3-butyric acid (IBA) + kinetin induced white or pale green friable calli with a good root regeneration capacity (60%). A factorial experiment with different combinations of 2,4-D + zeatin + gibberellic acid (GA3) levels revealed that the direction of explant differentiation was determined by specific PGR interactions and concentrations. The results from these experiments revealed that the morphogenetic pathway (shoot versus root differentiation) can be manipulated on flax explants by raising the 2,4-D level from 0.05 to 3.2 mg l−1 in the induction medium. The induction and development of somatic embryos from flax explants was possible in a range of 2,4-D + zeatin concentrations surrounding 0.4 mg l−1 2,4-D and 1.6 mg l−1 zeatin, the most efficient growth regulator combination.
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TL;DR: Regenerants were successfully micropropagated, although callus formation caused by zeatin and high 2iP levels interfered with shoot proliferation, and cells from callus and suspension cultures did not exhibit regeneration in any of the media that supported organogenesis from leaves.
Abstract: Ohelo (V. pahalae Skottsb.) and bilberry (V. myrtillus L.) shoots were regenerated via direct organogenesis from whole leaves and leaf sections and also from hypocotyl explants of bilberry. Explants preincubated for 1 to 2 weeks in darkness yielded 75% regeneration frequencies and the highest number of regenerating shoots/explant on TDZ-supplemented media (0.9 to 2.7 μM). When 2iP or zeatin were substituted as the cytokinin source, frequencies of regeneration and shoot productivity were significantly lower. Explants held under constant illumination (no dark pretreatment) had significantly lower regeneration frequencies in all tested cytokinin-supplemented media. 2,4-D stimulated callus formation, but did not support regeneration from vegetative explants. Cells from callus and suspension cultures did not exhibit regeneration in any of the media that supported organogenesis from leaves. Regenerants were successfully micropropagated, although callus formation caused by zeatin and high 2iP levels interfered with shoot proliferation. Zeatin induced hyperhydricity in shoots from both species, but more severely in ohelo. Ex vitro rooting after treatment with 4.9 μM IBA or 5.4 μM NAA was 95 % and 60% successful for bilberry and ohelo, respectively, and plants were readily acclimatized after an interval in a fog chamber. Bilberry microshoots also rooted in vitro in the absence of growth regulator treatment. Chemical names used: 1H-indole-3-butanoic acid (IBA); N-(3-methyl-2-butenyl)-1-H-purine-6-amine (2iP); 6-furfurylaminopurine (kinetin); 1-naphthaleneacetic acid (NAA); thidiazuron=1-phenyl-3-(1,2,3-thiadiazio-5-yl)urea (TDZ); 2,4-dichlorophenoxyacetic acid (2,4-D); 6-(4-hydroxy-3-methylbut-2-enylamino) purine (zeatin).
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TL;DR: The aromatic cytokinins, and in particular, ortho-topolin riboside, were found in a variety of oil palm tissues at concentrations exceeding those of the isoprenoid cytokinin, zeatin, isopentenyladenine, dihydrozeatin, and their ribosides.
Abstract: The natural occurrence of 6-benzylaminopurine, 6-(2-hydroxybenzylamino)purine (ortho-topolin), 6-(3-hydroxybenzylamino)purine (meta-topolin), their ribosides and 9-glucosides is reported using specific antibodies to these groups of compounds in high performance liquid chromatography/enzyme-linked immunosorbent assay (HPLC/ELISA). Compounds were identified by their retention times and differential cross-reactivities with six antisera in analyses carried out in two laboratories using different HPLC gradient systems. Identities were confirmed by immunoaffinity purification followed by HPLC with on-line UV spectrum analysis. Further confirmation of the occurrence of ortho-topolin riboside and isopentenyladenine-9-glucoside was obtained from gas chromatography-mass spectrometry analysis of permethylated HPLC fractions of an extract of oil palm tissues. The aromatic cytokinins, and in particular, ortho-topolin riboside, were found in a variety of oil palm tissues at concentrations exceeding those of the isoprenoid cytokinins, zeatin, isopentenyladenine, dihydrozeatin, and their ribosides. The 9-glucosides of isopentenyladenine and zeatin were more abundant than those of the aromatic types. The cross-reactivity of benzyladenine compounds with antibodies to isopentenyladosine is discussed in relation to the interpretation of ELISA data.
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TL;DR: The accumulation of cytokinin (mostly zeatin riboside orZeatin nucleotide) in mature fruit may be of significance for the postharvest storage of kiwifruit fruit.
Abstract: The cytokinin content in fruit tissue of the kiwifruit (Actinidia deliciosa [A. Chev.] C. E Liang et A. R. Ferguson var. deliciosa cv. Hayward) was monitored during fruit development to identify which cytokinins were present and if they were linked with specific stages of fruit growth. Cytokinins were isolated and purified by column chromatography and high-performance liquid chromatography and quantified by radioimmunoassay. A novel HPLC step utilising an amine column was successfully introduced as a preparative step in the separation of the O- and 9-glucosides from the free bases and ribosides. The radioimmunoassay results were validated, and the different cytokinins identified, by gas chromatography-mass spectrometry. Cytokinins detected in fruit included the cytokinin free bases, zeatin and isopentenyladenine, their ribosides, nucleotides and both O- and 9-glucosides. Both qualitative and quantitative changes of the cytokinins occurred during fruit development. A decrease in cytokinin concentration occurred after anthesis (from 342 pmol g -1 fresh weight at anthesis to 41 pmol g -1 fresh weight 27 days after anthesis). A large increase in cytokinin concentration and content per fruit occurred as the fruit reached commercial maturity (to 1 900 pmol g -1 fresh weight). Individual cytokinins showed quite different patterns. Zeatin, in particular, showed a peak in concentration (13 pmol g -1 fresh weight) 11 days after anthesis that correlated with the beginning of the cell division phase of fruit growth. The accumulation of cytokinin (mostly zeatin riboside or zeatin nucleotide) in mature fruit may be of significance for the postharvest storage of kiwifruit fruit.
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TL;DR: Rhododendron simsii ‘Hellmut Vogel’ was regenerated using different types of explants, auxins and cytokinins and the duration of the callus induction phase was negatively correlated with the regeneration capacity.
Abstract: Rhododendron simsii ‘Hellmut Vogel’ was regenerated using different types of explants, auxins and cytokinins. After a callus induction phase, with 2,4-dichlorophenoxyacetic acid or α-naphthaleneacetic acid, adventitious shoot regeneration was obtained on a medium supplemented with thidiazuron or zeatin. With thidiazuron shoots were small and a subsequent elongation step was required before rooting. An elongation step was not required when zeatin was used. The duration of the callus induction phase was negatively correlated with the regeneration capacity.
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TL;DR: Leaf segments of Prunus persica (L.) Batsch ‘Elberta Queen’ were collected from in vitro-grown proliferating shoots and cultured onto a basal medium supplemented with a wide range of TDZ concentrations (3 to 23 µM), and caulogenesis was observed along cut margins of leaf explants.
Abstract: SummaryLeaf segments of Prunus persica (L.) Batsch ‘Elberta Queen’ were collected from in vitro-grown proliferating shoots and cultured onto a basal medium containing half-strength Murashige and Skoog (MS) salts, Staba vitamins, 30 g l−1 sucrose and 6.5 g l−1 Difco-bacto agar. The influences of six growth regulators supplemented at three levels (5, 10 and 15 µM) on callus induction were investigated under light conditions (16 h photoperiods). For all growth regulator treatments, caulogenesis was observed along cut margins of leaf explants. Among cytokinins tested, thidiazuron (TDZ) induced compact green calli, 6-benzyladenine (BA) and zeatin induced small calli, and kinetin failed to induce callus. For auxin treatments, both dicamba and 2,4-D induced friable white to yellowish calli. In another experiment, leaf explants collected from greenhouse-grown ‘Bellaire’ and in vitro-grown ‘Elberta Queen’ were cultured onto the basal medium supplemented with a wide range of TDZ concentrations (3 to 23 µM). Cauloge...
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TL;DR: Green callus was obtained from the surface of embryogenic yellow callus which was induced from Allium fistulosum floret tissue on MS agar medium with significantly promoted initiation of green callus by 0.5–1.0 mg/l BA supplement in culture medium.
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TL;DR: The imidazole fungicides imazalil, prochloraz, and triflumizole and the triazole growth retardant paclobutrazol strongly enhanced the shoot-inducing effect of 6-benzyladenine in Spathiphyllum floribundum ‘Petite’ Schott, which suggests that Araceae are especially sensitive to this interaction.
Abstract: The imidazole fungicides imazalil, prochloraz, and triflumizole and the triazole growth retardant paclobutrazol strongly enhanced the shoot-inducing effect of 6-benzyladenine in Spathiphyllum floribundum ‘Petite’ Schott. Numerous small shoots and shoot meristems appeared at the basal part of the plant. This effect was confirmed when such widely different cytokinins as zeatin, meta-topolin, and thidiazuron were combined with imazalil. Neither these fungicides nor paclobutrazol showed cytokinin effects on cytokinin-free medium. The number of roots per explant could be augmented using particular concentrations, depending on the fungicide used. The combination prochloraz and 6-benzyladenine had a similar effect on Anthurium andreanum, which suggests that Araceae are especially sensitive to this interaction.
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TL;DR: Higher concentrations of benzyladenine and Zeatin were required to enhance shoot formation in silktree, compared to TDZ, and thidiazuron was highly effective in stimulating shoot formation at low concentrations (<1 μM.
Abstract: Root segments (1 cm long) were excised from 15–20 day old seedlings of silktree (Albizzia julibrissin) grown on B5 medium. About 50% of the control (no growth regulators added) root explants formed shoot buds within 15 days after placement on the culture medium. After 30 days, there were about 4 shoots per control explant. Addition of low levels of various auxins (0.5 μM) did not influence the formation of shoot buds from the explants. Higher concentrations (5μM), however, decreased shoot regeneration. Kinetin and 2iP did not influence shoot regeneration at the concentrations tested (1 & 10 μM). Addition of benzyladenine, Zeatin, or thidiazuron to the culture medium increased both the percentage of explants that formed shoots and the number of shoots per explant. Thidiazuron was highly effective in stimulating shoot formation at low concentrations (<1 μM). At 0.05 μM thidiazuron, 95% of the explants produced shoots and about 10 shoots were formed per explant. Compared to TDZ, higher concentrations (10 μM) of benzyladenine and Zeatin were required to enhance shoot formation. Upon excision and transfer to B5 medium, regenerated shoots developed into normal rooted plantlets.
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TL;DR: The growth regulator dicamba was significantly better than 2,4-dichlorophenoxyacetic acid in promoting somatic embryogenesis and subsequent plant regeneration, and somatic embryos developed well.
Abstract: Basal media and plant growth regulators were tested for the promotion of somatic embryogenesis from immature wheat-rye hybrid embryos. Influence of growth regulators and chilling on plant regeneration were tested on two media. A medium containing four amino acids-glutamine, arginine, glycine and aspartic acid-as the nitrogen source, promoted the production of, on average, twice as much embryogenic callus as the other media, and somatic embryos developed well. The growth regulator dicamba was significantly better than 2,4-dichlorophenoxyacetic acid in promoting somatic embryogenesis and subsequent plant regeneration. Germination of somatic embryos on both regeneration media was enhanced by cold treatment. Supplementing 190-2 plant regeneration medium with a combination of α-naphthaleneacetic acid + benzyladenine, indole-3-acetic acid + kinetin or indole-3-acetic acid + zeatin resulted in equally high germination rates.
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TL;DR: Axillary buds from 3-year-old Carica pubescens Lenné et Koch (highland papaya) fruit-bearing plants grown in the greenhouse were cultivated in NN-medium supplemented with different growth regulators naphthaleneacetic Acid and indoleacetic acid in combination with Zeatin, benzyladenine, Kinetin and thidiazuron.
Abstract: Axillary buds (2 mm) from 3-year-old Carica pubescens Lenne et Koch (highland papaya) fruit-bearing plants grown in the greenhouse were cultivated in NN-medium supplemented with different growth regulators naphthaleneacetic acid and indoleacetic acid in combination with Zeatin, benzyladenine, Kinetin and thidiazuron. Several responses were observed within 2–3 months; namely, sprouting of the preformed axillary buds, bud branching into multiple shoots, callus formation at the basal end of the explant and somatic embryogenesis in the preformed callus. Somatic embryogenesis was frequent in most of the tested growth regulator combinations, with the exception of thidiazuron which showed no effect. A much higher yield of somatic embryos could be obtained in suspensions. Somatic embryogenesis was enhanced by the occurence of adventive embryogenesis on single embryos as globular embryo clusters. This was observed in cell suspensions initially grown in a WPM-medium with 2,4-dichlorophenoxyacetic acid, or in combination with benzyladenine or zeatin, for 6 days, then maintained in a growth regulator-free medium under continuous agitation (50 RPM) on an orbital shaker for 3 months. Single cells grown in the absence of 2,4-dichlorophenoxyacetic acid did not initiate embryogenesis and de-differentiated into callus. Plantlets were recovered after transfer of mature embryos from cell suspensions into Magenta flasks. In a second subculture, adventitious embryogenesis occurred spontaneously in clusters at the globular embryo stage under the same growth conditions, yielding a high number of embryos. The culture conditions described above allowed initiation of a large number of somatic embryos directly from cell suspensions through adventive somatic embryogenesis and indirectly from callus on axillary buds.
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TL;DR: Although the balance between isopentenyladenine, zeatin, dihydrozeatin, and their derivatives was shifted to distinguished directions by administration of BA and/or imazalil and or GA3, no correlation between these changes in metabolic pathways and the number of shoots could be found.
Abstract: Imidazole fungicides such as imazalil, prochloraz, and triflurnizole and the triazole growth retardant paclobutrazol promote the shoot-inducing effect of exogenous cytokinins in Araceae, such as Spathiphyllum floribundum Schott and Anthurium andreanum Schott. The mechanism of their action could partially be based on the inhibition of gibberellic acid (GA) biosynthesis, because administration of GA3 inhibits the phenomenon completely in S. floribundum. Not only is the suppression of GA biosynthesis involved, but also the metabolism of endogenous cytokinins is significantly altered. Although the balance between isopentenyladenine, zeatin, dihydrozeatin, and their derivatives was shifted to distinguished directions by administration of BA and/or imazalil and/or GA3, no correlation between these changes in metabolic pathways and the number of shoots could be found. The metabolism of BA was not significantly altered by adding imazalil to the micropropagation medium of S. floribundum.
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TL;DR: Zeatin nucleotide and isopentenyladenine nucleotide were the most abundant cytokinins in all organs, and were greater in the stems than in the other organs on a per plant basis.
Abstract: The determination of the various endogenous cytokinins and their distribution among organs is important in understanding their role in growth and development in the intact plant Cytokinins in young plants of Phaseolus vulgaris were purified by immunoaffinity chromatography and HPLC, and characterised by UV spectra Zeatin nucleotide (zeatin riboside-5'-monophosphate) and isopentenyladenine nucleotide (isopentenyladenosine-5'-monophosphate) were the most abundant cytokinins in all organs Their identities were confirmed by GC-MS The levels of zeatin, zeatin riboside, isopentenyladenine and isopentenyladenosine never exceeded 5% of the nucleotides, as assessed by a methodology that preserves cytokinin nucleotides Three extraction methods were compared with qualitatively similar results, though differing in their suppression of nucleotidase activity Cytokinin nucleotide levels were greater in the stems and petioles than in the roots and leaves on a per gram fresh weight basis, and were greater in the stems than in the other organs on a per plant basis Levels of the zeatin and isopentenyladenine nucleotides were about equal in the stems and leaves, but in the petioles the zeatin nucleotide levels were about twice the level of isopentenyladenine nucleotide, while in the roots they were about half the isopentenyladenine nucleotide level The importance of considering the cytokinin form is emphasised
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TL;DR: In this article, the role of endogenous cytokinins as the hormonal signal, by which the roots regulate leaf metabolism and prevent leaf senescence in particular, is discussed, and a protein of 28-30 kD was isolated from barley leaf cytosol by its affinity to synthetic cytokinin benzyladenine (BA).
Abstract: A role of endogenous cytokinins as the hormonal signal, by which the roots regulate leaf metabolism and prevent leaf senescence in particular, is discussed. Cytokinin signal perception and transduction in leaf cells were studied on fully expanded first leaves of 10–13-day-old barley plants (Hordeum vulgare L. cv. Viner). Their high sensitivity to exogenous cytokinins depends on dramatic decrease in endogenous cytokinin content during leaf growth. Cytokinin-binding protein of 28–30 kD was isolated from barley leaf cytosol by its affinity to synthetic cytokinin benzyladenine (BA) The 30-kD protein was involved in cytokinin-dependent activation of RNA synthesis in vitro in the system containing chromatin-bound RNA polymerase I from barley leaves. Multistage purification of the protein included affinity chromatography on trans-zeatin-Sepharose or zeatin riboside-Sepharose resulted in isolation of barley leaf cytosol 67-kD protein up to electrophoretic homogeneity. The protein was revealed as a single band in Western blot analysis developed with anti-idiotype antibodies from antiserum to zeatin. In concert with trans-zeatin the 67-kD protein activated transcription elongation directed by RNA polymerase I (in the system containing chromatin-bound RNA polymerase I from barley leaves) and by RNA polymerase II (in nuclei isolated from barley leaves). The protein effect strongly depended on cytokinin concentration. The maximum activation was observed at trans-zeatin concentration of 10-8 M. cis-Zeatin had no effect. These results together with data on reversible [3H]zeatin-binding moiety of the 67-kD protein [8] provide a definitive proof to consider this protein as one of the cytokinin receptors in barley leaf cells which is responsible for cytokinin activation of transcription elongation directed by both RNA polymerase I and RNA polymerase II.
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TL;DR: The levels of two phytohormones, indole-3-acetate and zeatin plusZeatin riboside were found to be several-fold higher in roots of blue light-grown plants compared with red light- grown ones, which obviously create a higher sink demand from roots to leaves in blue light -grown plants, which facilitate the development of under-ground storage tissues.
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TL;DR: Investigating diurnal changes in cytokinin levels in the short-day plant found that those arriving at the apical part are derived mostly from leaves with varying contributions by the xylem, and it is as yet not clear if photoperiod controls the phosphorylation or dephosphorylation reaction.
Abstract: Cytokinin (CK) levels in the short-day plant Chenopodium rubrum L. are known to fluctuate diurnally. The aim of this work was to investigate if the diurnal changes are brought about by changes in transport and/or metabolism of CKs. The effect of photo-period on cytokinin transport was studied by analysing CK concentrations in root, leaf and apical exudates, respectively, under constant light (CL), a 12-h photoperiod (DL) inductive for flowering, DL in which darkness was interrupted at the end of hour 6 by 15 min red light (R), or by 15 min R followed by 30 min far-red irradiation (R/FR). The concentrations of cytokinins (zeatin, zeatin riboside, isopentenyladenine, isopen-tenyladenosine) in all three types of exudates were significantly higher in the first 12-h period after the end of 12 h darkness than in CL. The R break almost fully negated the effect of darkness and its effect was reversed by FR, showing the involvement of phytochrome in the regulation of CK transport. In the next 12-h interval, i.e. 12–24 h after the end of darkness, the CK level remained high in the leaf exudate only, but to a much lower extent than in the previous 12 h. The highest CK concentration (increase by 108%) was observed in apical exudates during inductive darkness. A comparison of the CKs present in the individual exudates indicates that those arriving at the apical part are derived mostly from leaves with varying contributions by the xylem. The metabolism of applied [3H]-zeatin riboside (ZR) was studied using HPLC separation of the metabolites. Metabolism was found to be very rapid and different glucosides, adenine and adenosine were the main metabolites after 12 h incubation with labelled ZR in all regimes tested. The only metabolite that seems to be under photoperiodic control is ZR-5′-monophosphate. It is as yet not clear if photoperiod controls the phosphorylation or dephosphorylation reaction. The activity of the main cytokinin degradative enzyme, cytokinin oxidase, did not change during the photoperiodic regimes tested.
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TL;DR: The data show that hormone-independent calluses and cell suspensions can retain some sensitivity to growth hormones, however, differences of responses were observed between the auxin-dependent lines and the habituated lines.
Abstract: Fully habituated organogenic and nonorganogenic sugarbeet calluses reacted to application of the synthetic auxin [3-benzo(b) selenienyl] acetic acid by changes in growth and ethylene production. Treatment of fully habituated cells of periwinkle with 2,4-dichlorophenoxyacetic acid led to the decrease of free cytokinin contents (isopentenyl adenine, zeatin riboside, and zeatin) during the late exponential phase of growth. The polyamine contents were also modified and the capacity to biotransform secologanin into ajmalicine was decreased. Treatment of the habituated periwinkle cells with zeatin greatly increased the amount of a polypeptide of 16 kDa; this response was more marked than that displayed by the auxin-dependent line. These data show that hormone-independent calluses and cell suspensions can retain some sensitivity to growth hormones. However, differences of responses were observed between the auxin-dependent lines and the habituated lines.
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TL;DR: Two derivatives of N6-isopentenyladenine, 3 and 4, bearing either a vinylic fluorine atom or a trifluoromethyl group, were easily synthesized from known fluorinated precursors.
Abstract: Two derivatives of N6-isopentenyladenine, 3 and 4, bearing either a vinylic fluorine atom or a trifluoromethyl group, were easily synthesized from known fluorinated precursors. Both derivatives 3 and 4 were found to be more active, as cytokinins, than the parent compounds zeatin (1) and N6-isopentenyladenine (2). Keywords: Cytokinins; fluoro compounds; biological activity