Showing papers on "Zeatin published in 1975"
TL;DR: An extract from 8-day-old cotton ovules was partitioned into three fractions and each fraction was derivatized and analyzed separately to separate, measure, and identify the naturally occurring plant hormones.
Abstract: An extract from 8-day-old cotton ovules (Gossypium hirsutum L.) was partitioned into three fractions and each fraction was derivatized and analyzed separately. Gas-liquid chromatography and computer-controlled gas-liquid chromatography-mass spectrometry were used to separate, measure, and identify the naturally occurring plant hormones. A single extract contained abscisic acid, indoleacetic acid, and gibberellins A(1), A(3), A(4), A(7), A(9), and A(13) in the first fraction; ethyl indole-3-acetate and indole-3-aldehyde in the second fraction; and the cytokinins 6-(3-methyl-4-hydroxybutylamino)purine (dihydrozeatin), 6-(4-hydroxy-3-methyl-2-trans-butenylamino) purine (zeatin), 6-(3-methyl-2-butenylamino)purine(2iP), 6-(3-methyl-2-butenylamino)-9-beta-d-ribofuranosylpurine(2iPA), and 6-(4-hydroxy-3-methyl-2-trans-butenylamino)-9-beta-d- ribofuranosylpurine (zeatin riboside) in the third fraction.
192 citations
TL;DR: Gibberellin A3 (GA3) or abscisic acid (ABA) did not affect the number of embryos formed in the globular and early heart stages but caused a decrease of those in the heart and torpedo stages.
157 citations
TL;DR: 2,4,5-Tri-chlorophenoxyacetic acid, Benazolin, and Banvel D (Dicamba) were found to be appropriate growth regulators for initiation and maintenance of wheat callus cultures.
Abstract: Callus cultures of wheat (Triticum aestivum L.) were established by incubation of segments from root tips, shoots of seedlings, and from rachis with B5 and T media. 2,4,5-Tri-chlorophenoxyacetic acid, Benazolin, and Banvel D (Dicamba) were found to be appropriate growth regulators for initiation and maintenance of wheat callus cultures. Cytokinins inhibited callus growth. This effect was less pronounced with zeatin than with kinetin and benzyladenine. Supplementation of media with cytokinins, however, increased the number of roots formed in the callus. Shoots and complete plants were regenerated from rachis and shoot callus.
89 citations
TL;DR: Zeatin and zeatinriboside were identified from the milk of mature Cocos nucifera fruits and it would appear as if the two compounds are present in roughly equal proportions.
Abstract: Zeatin and zeatinriboside were identified from the milk of mature Cocos nucifera fruits. It would appear as if the two compounds are present in roughly equal proportions. Ethyl acetate extraction in a liquid-liquid extractor at an alkaline pH (8.0) proved to be a very efficient method of extracting zeatinriboside. Partitioning with water-saturated n-butanol proved to be the best way of extracting zeatin.
57 citations
TL;DR: Alternative morphogenetic events probably reflect the bio chemical subtleties occurring within the callus as a result of differences of actual endogenous levels of growth substances in the tissues studied.
Abstract: Excised stem explants of Antirrhinum majus L. var. 'Kymosy blanc' were grown in a defined medium to investigate factors influencing bud and root development, callus induction, and somatic embryogenesis. Auxins such as indoleacetic acid (IAA) and naphthaleneacetic acid (NAA) caused limited callus development and abundant root formation, whereas 2,4-dichloro phenoxyacetic acid (2,4-D) promoted soft friable callus with embryos and occasional develop ment of thick abnormal roots. 2-Naphthoxy acetic acid (NOA) and coconut milk (CM) used together induced friable green callus growth and differentiation of small globular embryos which eventually developed into plantlets after transfer to auxin-free agar mineral medium containing sucrose. Cytokinins such as benzyladenine (BA), zeatin, and kinetin induced compact green callus but in the absence of auxin failed to promote organogenesis. The inter action of IAA and kinetin resulted in the regeneration of the whole plant from stem explants. When NAA was used with kinetin, shoot development was totally inhibited and abundant roots were formed. Thus, the alternative morphogenetic events probably reflect the bio chemical subtleties occurring within the callus as a result of differences of actual endogenous levels of growth substances in the tissues studied. These experiments have been performed and interpreted on a histological basis.
50 citations
TL;DR: Among several growth substances tested, zeatin, a natural cytokinin, was found to be most effective for the differentiation of shoot buds in Actinidia chinensis PL.
Abstract: SummaryFormation of shoot buds, roots and globular embryoids were induced in in vitro culture of stem and root segments of Actinidia chinensis PL (Kiwi or Ichang). Among several growth substances tested, zeatin, a natural cytokinin, was found to be most effective for the differentiation of shoot buds. Complete plants were obtained by isolating developed shoot buds from expiants and inducing root formation on them using a medium containing a low concentration of auxin.
46 citations
TL;DR: In darkness zeatin promoted cotyledon growth but did not increase sugar levels nor amylase activity, suggesting that enhanced ion accumulation also contributes to the more rapid water uptake leading to growth.
Abstract: Effects of zeatin on amino acid and sugar contents of detached radish (Raphanus sativus L.) cotyledons were investigated to determine if accumulation of these solutes contributes to cytokinin-enhanced growth. Protein and amino acid levels were not significantly affected, but in cotyledons incubated in light the hormone caused greater accumulations of reducing sugars than occurred in light controls. Continuous fluorescent light or a few minutes of red light increased both the growth rate and the reducing sugar levels compared to dark controls. A far red treatment following red light overcame the promoting effect of the latter. Amounts of reducing sugars were closely associated with growth under the above conditions. Activity of an unidentified amylase was elevated by continuous light or a red light treatment (nullifiable by far red), suggesting that reducing sugars were derived from starch. Zeatin-treated cotyledons exhibited less amylase activity than did light controls, perhaps implicating cytokinin-stimulated conversion of fats to sugars in light. In darkness zeatin promoted cotyledon growth but did not increase sugar levels nor amylase activity, suggesting that enhanced ion accumulation also contributes to the more rapid water uptake leading to growth.
44 citations
TL;DR: Thin explants composed of the epidermis and underlying collenchyma excised from leaf veins of Begonia rex and cultured in vitro are capable of neoformation of unicellular hairs, roots and buds and this hypothesis was supported by short temperature treatments applied at different times during hair formation.
Abstract: Thin explants composed of the epidermis and underlying collenchyma excised from leaf veins of Begonia rex and cultured in vitro are capable of neoformation of unicellular hairs, roots and buds. Unicellular hairs were formed over the entire surface of the explant when 10−6M indole acetic acid or 10−7M naphthaleneacetic acid (NAA) was added to the basal medium; each epidermal cell was potentially involved. The epidermis was most sensitive to a NAA treatment during the first few days of culture but 30% of the explants could still react after 4 days of culture without NAA. When NAA (5 × 10−7M) and a cytokinin, zeatin (10−7M), were added together, roots were formed from epidermal tissue after numerous divisions in the original cells. Their initiation was not related to particular cells. Buds were formed when a cytokinin (10−6M) was added to the basal medium; bud meristems were formed from small groups of cells surrounding basal cells of glandular hairs. Hair formation was inhibited by either high (32–27°C) or low (12°C) temperatures applied continuously. 32–27°C seemed to inhibit elongation of the hairs specifically, whereas 12°C inhibited earlier phases in hair formation. This hypothesis was supported by short temperature treatments applied at different times during hair formation.
43 citations
TL;DR: The activities of isomers of zeatin, ribosyl-zeatin, and 6-(gamma,gamma-dimethylallylamino) purine on the moss Funaria hygrometrica are compared by measuring the ability of the cytokinins to induce callus or gametophores.
Abstract: The activities of isomers of zeatin, ribosyl-zeatin, and 6-(gamma,gamma-dimethylallylamino) purine (i(6)Ade) on the moss Funaria hygrometrica are compared by measuring the ability of the cytokinins to induce callus or gametophores. The cis- and trans-ribosyl-zeatins were inactive, and therefore this kind of bioassay cannot be used as evidence for the presence or absence of a cytokinin in tests on natural products.
36 citations
TL;DR: In this article, the authors determined the loss of one naturally occurring cytokinin (zeatin) and one synthetic cytokin (kinetin) during purification of turnips (Brassica compestris) infected by Plasmodiophora brassicae (clubroot).
Abstract: Losses of one naturally occurring cytokinin (zeatin) and one synthetic cytoknin (kinetin) were determined during purification of turnips (Brassica compestris) infected by Plasmodiophora brassicae (clubroot). A known amount of zeatin and 8‐14C‐kinetin was added after homogenization of plant material in ethanol or water. The commonly used practice to purify the aqueous residues of the homogenate by partitioning with petroleum ether was omitted because of emulsion formation. Losses due to emulsion formation and occlusion of 8‐14C‐kinetin into non‐water soluble plant material could be prevented by extractionof clubroot tissue with water instead of ethanol. To minimize enzyme activity the aqueous homogenate was kept at 100°C for 5 min. High molecular weight compounds were removed by dialysis against water and the diffusible fraction was partitioned with n‐butanol at pH 8.2. It was shown that a rapid evaporation of n‐butanol under reduced pressure at high temperature caused less breakdown of 8‐14C‐kinetin than prologned treatment at a low temperature. To minimize breakdown to zeatin riboside the butanol fraction was purified further on cation cellulose‐phosphate exchanger instead of on strong acid Dowex H+. 8‐14C‐kinetin was separated from zeatin by column chromatography on Sephadex LH20, and yielded 86% of the amount originally added to a plant homogenate. The zeatin containing fractions were further purified on thin layer chromatography (TLC) silicagel plates and injected into a high pressure liquid chromatograph. A yield of 60% could be estimated from the amount (15 μg) orignally added to 50 g clubroot tissue
27 citations
TL;DR: The present study reinvestigates the question of interaction using measurements of chlorophyll degradation kinetics as parameters of senescence rate and draws the conclusion that neither zeatin nor gibberellic acid interact with abscisic acid in this system.
Abstract: Hormones which inhibit senescence in Rumex leaf tissue in the dark include gibberellic acid and the cytokinin zeatin. Abscisic acid accelerates senescence in this tissue. Other workers have proposed that cytokinins, but not gibberellins, interact with abscisic acid in senescing Rumex leaf tissue. The present study reinvestigates the question of interaction using measurements of chlorophyll degradation kinetics as parameters of senescence rate and draws the conclusion that neither zeatin nor gibberellic acid interact with abscisic acid in this system. In support of this conclusion are these results. Zeatin clearly cannot overcome the effects of abscisic acid when hormone solutions are replaced every other day. The kinetics of chlorophyll breakdown for tissue treated with unreplaced saturating zeatin solutions is different from that of tissue exposed to saturating zeatin plus abscisic acid. The observed rates of chlorophyll breakdown for tissue treated with abscisic acid and zeatin agree closely with predicted rates using a multiplicative model for independent action of the two hormones.Zeatin solutions, when replaced every other day, show up to a 550-fold increase in effective concentration in the retardation of senescence. Less than a 10-fold increase could be accounted for by the addition of more zeatin molecules to the tissue. A nonbiological inactivation of zeatin or the production of an inhibitor of zeatin action by the tissue could not be demonstrated. It seems that zeatin is metabolically inactivated or sequestered in this tissue. The possible physiological significance of the inactivation of cytokinins in leaf tissue is discussed.
TL;DR: The structure β-[6-(4-hydroxy-3-methylbut-trans-2-enylamino)purin-9-yl]alanine has been assigned to lupinic acid, a novel zeatin metabolite isolated from Lupinus angustifolius seedlings as discussed by the authors.
Abstract: The structure β-[6-(4-hydroxy-3-methylbut-trans-2-enylamino)purin-9-yl]alanine has been assigned to lupinic acid, a novel zeatin metabolite isolated from Lupinus angustifolius seedlings.
TL;DR: Results suggest that substitution of the 8 position with a hydroxyl group causes less decrease of cytokinin activity than substitution of both the 2 and 8 positions with Hydroxyl groups.
Abstract: 8-Hydroxy and 2,8-dihydroxy derivatives of the cytokinins, 6-(4-hydroxy-3-methyl-trans-2-butenylamino)purine and N-6-(increment -2-isopentenyl)adenine, have been biosynthesized by xanthine oxidase oxidation. 8-Hydroxy derivatives have been shown to be the major intermdeiates. These compounds were tested for cytokinin activity in the tobacco bioassay. The results suggest that substitution of the 8 position with a hydroxyl group causes less decrease of cytokinin activity than substitution of both the 2 and 8 positions with hydroxyl groups.
TL;DR: Findings suggest that a cytokinin is produced by bacteria in leaf nodules of P. punctata and that it is involved in the symbiosis.
Abstract: Cytokinin activity based on two bioassays was at least 100-fold higher in Psychotria punctata leaf discs with bacterial nodules than in discs without them. Nodulated discs from young leaves yielded 0.4 to 6 mug of cytokinin (zeatin equivalents) per g fresh weight of leaf tissue, whereas non-nodulated discs from the same leaves yielded 0 to 0.003 mug per g fresh weight. These estimates probably include free-base cytokinins and, if present, any nucleoside cytokinins precipitable by acidic silver nitrate. Cytokinin concentrations in Psychotria leaf nodules appear to be higher than normally found in green leaves of other plants. In l-butanol-acetic acid-water (12:3:5, v/v), the one peak of activity chromatographed with an R(F) similar to zeatin's, but both number and identity of the active substance(s) remain unknown. These findings suggest that a cytokinin is produced by bacteria in leaf nodules of P. punctata and that it is involved in the symbiosis.
TL;DR: The complete structures of raphanatin, the stable zeatin metabolite isolated from de-rooted radish seedlings, and the analogous 6-benzylaminopurine metabolite from the same plant system, have been confirmed by synthesis to be the 7-β-D-glucopyranosides of Zeatin and 6-BAP respectively as discussed by the authors.
Abstract: The complete structures of raphanatin, the stable zeatin metabolite isolated from de-rooted radish seedlings, and the analogous 6-benzylaminopurine metabolite from the same plant system, have been confirmed by synthesis to be the 7-β-D-glucopyranosides of zeatin and 6-BAP respectively.
TL;DR: A number of cytokinin-active compounds were detected in cabbage extracts by the Amaranthus betacyanin bioassay using this separation technique.
Abstract: Separation of a mixture of the main cytokinins occurring naturally in plant tissues was achieved by high pressure liquid chromatography using insoluble polyvinylpyrrolidone as the solid support. The separation of each cytokinin was first assessed over a range of salt and l-butanol concentrations and pH using a mixture of borate buffer and l-butanol as the mobile phase to determine the conditions necessary for optimum resolution. A discrete separation of zeatin, N-6-(Δ-2-isopentenyl)adenine, their related ribonucleosides, and kinetin was achieved using a simple isocratic elution with 0.025 m borate buffer at pH 6.8 and 4% (v/v) l-butanol. A number of cytokinin-active compounds were detected in cabbage extracts by the Amaranthus betacyanin bioassay using this separation technique.
TL;DR: Three peaks of activity on Sephadex LH-20 were extracted from wasp larvae found in Erythrina latissima galls, and the active substances in the larvae showed a striking similarity to those found in coconut milk.
TL;DR: Chromatography of partially purified extracts of Danish cabbage (Brassica oteraeea var. capitata L.) heads on poly-vinyjpyrrolidone columns using a weak phosphate buffer indicated a cytokinin complex containing nine components active in the modified Amaranthus betacyanin bioassay as mentioned in this paper.
Abstract: Chromatography of partially purified extracts of Danish cabbage (Brassica oteraeea var. capitata L.) heads on poly- vinyjpyrrolidone columns using a weak phosphate buffer indicated a cytokinin complex containing nine components active in the modified Amaranthus betacyanin bioassay. Similar elution patterns were obtained with extracts of four different cabbage varieties but varietal differences occurred in the bio- logical activity from each component peak. Paper and thin-layer chromatography indicated the presence of both zeatin and zeatin riboside in the extracts but the other cytokinin-active eomponents were not identified. Separation of sweet-corn extracts by this technique indicated that most of the cytokinin activity occurred in the elution volume where zeatin and zeatin riboside would normally occur.
01 Jan 1975
TL;DR: A simple procedure for the separation of the cis and trans isomers of zeatin and ribosylzeatin by column chromatography on a neutral polystyrene resin, Porapak Q, in aqueous ethanol solutions is reported in this article.
Abstract: A simple procedure for the separation of the cis and trans isomers of zeatin and ribosylzeatin by column chromatography on a neutral polystyrene resin, Porapak Q, in aqueous ethanol solutions is reported. The method has been used to examine the stereoisomer composition of ribosylzeatin isolated from wheat germ transfer RNA. Chromatographic data for several other cytokinins are also presented. The identification of both the cis and trans isomers of zeatin [N6-(4-hydroxy-3-methyl-2-butenyl)adenine] and ribosylzeatin [N6-(4-hydroxy-3-methyl-2-butenyl)adenosine] as naturally occurring cytokinins (11, 13, 18) and constituents of tRNA molecules (5, 7, 20) has created a need for simple chromatographic methods of distinguishing between the stereoisomers of these compounds. Sephadex LH-20 chromatography (1) separates zeatin from ribosylzeatin, but it does not resolve the isomers of these compounds. The trimethylsilyl derivatives of the isomers can be separated by GLC (3). Playtis and Leonard (16) separated the cis and trans isomers of both zeatin and ribosylzeatin by TLC and used a modification of this procedure for the separation of the cis and trans isomers of isozeatin [N6-(4-hydroxy-2-methyl-2-butenyl)adenine] by column chromatography (9). Partial resolution of cis- and trans-ribosylzeatin by partition chromatography on Celite column has been reported (3). A simple procedure for the separation of the cis and trans isomers of zeatin and ribosylzeatin by column chromatography on a neutral polystyrene resin, Porapak Q, is reported here. This resin has found previous applications in both gas and liquid chromatography (8). In the latter case, it has been used for the separation and desalting of amino acids and peptides (14) and for the fractionation of steroids (4) and indole derivatives (15).
TL;DR: A simple procedure for the separation of the cis and trans isomers of zeatin and ribosylzeatin by column chromatography on a neutral polystyrene resin, Porapak Q, in aqueous ethanol solutions is reported.
Abstract: A simple procedure for the separation of the cis and trans isomers of zeatin and ribosylzeatin by column chromatography on a neutral polystyrene resin, Porapak Q, in aqueous ethanol solutions is reported. The method has been used to examine the stereoisomer composition of ribosylzeatin isolated from wheat germ transfer RNA. Chromatographic data for several other cytokinins are also presented.
TL;DR: Using solvent partitioning, partition chromatography on Sephadex LH-20 and mass spectrometry the major cytokinin present in malt extract was identified as zeatin this paper.
TL;DR: The content of adenosine-3',5'-cydic monophosphate in leaves of Impatiens sultani Hook was measured by a protein-binding assay and there is no indication that cAMP is acting as a secondary messenger of either phytohormone.
Abstract: The content of adenosine-3',5'-cydic monophosphate (cAMP) in leaves of Impatiens sultani Hook was measured by a protein-binding assay. A preceding administration of the natural cytokinin zeatin causes a diminution of the cAMP level. Administration of gibberellin (GA 3) does not bring about any variations. There is no indication that cAMP is acting as a secondary messenger of either phytohormone. Theophylline does not increase the content of cAMP found in the leaves.
TL;DR: During winter, excised leaf tissue from Rumex obtusifolius degrades chlorophyll at twice the summer rate but the plant hormones, gibberellic acid and zeatin inhibit the senescence rate by a constant percentage, regardless of season.
Abstract: During winter, excised leaf tissue from Rumex obtusifolius degrades chlorophyll at twice the summer rate but the plant hormones, gibberellic acid and zeatin, inhibit the senescence rate by a constant percentage, regardless of season.
TL;DR: Root exudate from young apple trees was found to contain adenine and another fluorescent compound chromatographically resembling zeatin, but differing from the latter in the UV spectra and GLC chromatograms.
TL;DR: These optimum curves indicate the inhibitory effect of high concentrations of zeatin on respiration and photosynthesis, and a typical optimum curve similar to that for respiration.
Abstract: Application of 1 ppm zeatin raises the respiration rate (measured by the Warburg method) of leaf mesophyll protoplasts ofPetunia hybrida by about 50% after 4 h; afterwards there is a rapid decrease. While the rate of respiration in the controls rises after 5 to 6 h, 1 ppm zeatin has a strong inhibitory effect. When the protoplasts are incubated with 0.1 ppm zeatin the rise in the rate is much slower, and after 7 h the rate is 30% higher than in the controls. Abscisic acid (10 ppm) decreases the respiration rate so that after 5 h it is less than half that of the controls. Later on there is a rise as in the controls, perhaps caused by senescence promoting effects of abscisic acid. The photosynthetic rate of the mesophyll protoplasts measured by14CO2 fixation decreases with increasing age of the preparation. The protoplasts previously incubated with zeatin for 1 to 3 h show an increase in photosynthesis: with 0.1 ppm zeatin the14C-fixation rate is higher the longer the hormone could operate. With 1 ppm zeatin we get a typical optimum curve similar to that for respiration. These optimum curves indicate the inhibitory effect of high concentrations of zeatin on respiration and photosynthesis. Aplikaci 1 ppm zeatinu se zvýsi rychlost dýchani (měřeno Warburgovou metodou) protoplastů z mesofylu listůPetunia hybrida po 4 h asi o 50%; pak nasleduje prudký pokles. Zatimeo rychlost dýchani u kontrolnich rostlin stoupa po 5 až 6 h, 1 ppm zeatinu ma silný inhibicni ucinek. Při dýchani u kontrolnich rostlin stoupa po 5 až 6 h, 1 ppm zeatinu ma silný inhibicni ucinek. Při použiti 0.1 ppm zeatinu je vzestup rychlosti, dýchani mnohem pomalejsi a po 7 h je o 30% vyssi než u kontrolnich rostlin. Kyselina abscisova (10 ppm) snižuje rychlost dýchani tak, že po 5 h je rychlost dýchani o polovinu nižsi než v kontrolni variantě. Později nasleduje vzestup, způsobený patrně vlivem kyseliny abscisove podporujici starnuti. Rychlost fotosynthesy protoplastů mesofylu měřena pomoci fixace14CO2 klesa se starnutim preparatu. Protoplasty vystavene působeni zeatinu během 1 až 3 h ukazovaly zvýseni rychlosti fotosynthesy. Při aplikaci 0.1 ppm zeatinu rychlost fixace14CO2 je tim větsi, cim dele mohl hormon působit. Při aplikaci 1 ppm zeatinu byla ziskana typicka optimalni křivka podobna křivce pro dýchani. Tyto optimalni křivky prokazuji inhibicni ucinek zeatinu na dýchani a fotosynthesu.
01 Jan 1975
TL;DR: Findings suggest that a cytokinin is produced by bacteria inleafnodules of P.punctata and thatitis involved inthesymbiosis and may be higherthannormally foundingreenleaves ofotherplants.
Abstract: MATERIALSAND METHODS Cytokinin activity basedon two bioassays was at least 100-fold higher inPsychotria punctataleafdiscswithbacterial nodules thanindiscs withoutthem.Nodulated discs fromyoungleavesyielded 0.4to6pgofcytokinin (zeatin equivalents) pergfreshweight ofleaftissue, whereasnonnodulated discsfromthesame leavesyielded 0 to 0.003 pgperg freshweight. Theseestimates probably include free-base cytokinins and,ifpresent, anynucleoside cytokininsprecipitable by acidicsilvernitrate. Cytokinin concentrations in Psychotria leafnodulesappearto be higherthannormally foundingreenleaves ofotherplants. In1-butanol-acetic acid-water (12:3:5, v/v), theone peak ofactivity chromatographed withan RFsimilar tozeatin's, butbothnumberandidentity oftheactivesubstance(s) remainunknown.Thesefindings suggest thata cytokinin isproduced bybacteria inleafnodules ofP.punctata and thatitisinvolved inthesymbiosis.