Showing papers on "Zeatin published in 1974"

Regulators of cell division in plant tissues : XXI. Distribution coefficients for cytokinins.

Abstract: The distribution of six cytokinins [zeatin, zeatin riboside, 6-(4-hydroxy-3-methylbutylamino)purine, 6-(3-methylbut-2-enylamino)purine and its riboside, and kinetin] between aqueous buffers (pH 3.0 and 7.0) and several organic solvents was assessed and partition coefficients calculated. Purification of cytokinins from plant extracts by solvent partition methods is discussed.

Apical dominance in roots of Pisum sativum L

Abstract: The influence of several natural and synthetic hormones on apical dominance of pea roots was investigated. Extracts of roots decapitated just before extraction or 12 h earlier were compared in a lateral root formation assay, in the Amaranthus assay for cytokinins and the Avena coleoptile assay. Indole-3-acetic acid shows a strong promotive effect on the initiation of lateral roots. Gibberellic acid has no significant effect. Abscisic acid and its presumable precursor xanthoxin show a strong inhibitory effect, and so do all cytokinins investigated (kinetin, benzyladenine, and zeatin). Decapitation of roots caused a significant increase in the number of lateral root primordia within 12 h. Paper chromatograms of root extracts indicate the presence of at least two inhibitors of lateral root formation in the alkaline fraction, and of two promoters in the acid fraction. The amount of both inhibitors seems to decrease if the tip of the main root is removed 12 h before extraction whereas the promoters of lateral root formation do not change in their concentration. The Amaranthus test shows cytokinin activity in the region of one of the two inhibitors, and this activity decreases after decapitation. The second inhibitor has the Rf of xanthoxin; it inhibits the growth of Avena coleoptiles and its activity also decreases after decapitation.

Regulators of cell division in plant tissues : XVIII. Metabolism of zeatin in Zea mays seedlings.

Abstract: [(3)H] Zeatin was supplied to Zea mays L. seedlings with roots excised; the metabolites identified were adenosine-5'-phosphate, adenosine, adenine, and 7-glucosylzeatin (a minor metabolite). The principal metabolites formed from zeatin by the roots of intact Z. mays seedlings were adenosine-5'-phosphate, zeatin riboside-5'-phosphate, zeatin riboside, adenine, adenosine and an unknown compound termed Y. This was isolated and identified as 9-glucosylzeatin. This glucoside also appeared to form from zeatin in cultured embryonic tissue of Z. mays.

Cytokinin production by the fungi Taphrina cerasi and T. deformans

Abstract: Cytokinins were released into chemically defined liquid media by cultures of Taphrina cerasi and T. deformans. The presence of the cell-division factors was demonstrated with the soybean callus tissue assay, which is specific for the detection of cytokinins. Paper chromatography in four solvent systems, in conjunction with bioassays, revealed that T. cerasi produced compounds that have migration patterns similar to those of zeatin, zeatin riboside, N6-(Δ2-isopentenyl) adenine, and N6-(Δ2-isopentenyl)adenosine. T. deformans produced compounds with chromatographic properties similar to those of zeatin, zeatin riboside, and a substance(s) the migration of which is correlated with the Rf interval that included the positions of N6-(Δ2-isopentenyl) adenine and its riboside. A third type of cytokinin, the mobility of which differs from those of the cytokinin standards used, was also produced by T. deformans. The total cytokinin activity in cultures of T. cerasi was calculated to be about 2 μg kinetin-equivalents...

Effect of light and growth substances on flowering of iris × hollandica cv. wedgwood

Abstract: SUMMARY In the winter period with prevailing low light intensities and short days, the forcing of Iris “Wedgwood” can easily result in flower bud abortion (bud blast). Consequently a high proportion of plants fail to produce flowers. To elucidate the cause of bud blast, plants were subjected to various treatments —12CO2, 14CO2, growth substances — in the period of rapid stem elongation about two weeks before flowering. Plants grown under weak illumination and normal CO2 concentration (leading to 57% flowering) were compared with plants grown under strong illumination at low CO2 concentration (leading to 100% flowering). As the dry weight of whole plants of both these groups was almost the same at flowering, bud blast under low illumination cannot simply be attributed to a lack of recent photosynthetic products. The distribution pattern of photosynthates appears to be changed. It is suggested that a hormone imbalance plays a role in the distribution pattern and consequently in bud blast, since injections of cytokinins, such as N6-benzylaminopurine, zeatin, and kinetin, during dark treatment can increase the flowering proportion.

Bud formation in Funaria hygrometrica: A comparison of the activities of three cytokinins with their ribosides.

Abstract: The activities of the cytokinins benzyladenine (BA), 6-(3-methylbut-2-enylamino)purine (IPA) and zeatin in promoting bud formation in protonemata of Funaria hygrometrica (L.) Sibth. were compared to the biological activities of the corresponding ribosides. Cytokinins were found to have considerably higher hormonal activity as free bases than as ribosides. This observation will be discussed in relation to the chemical identity of the celldivision factor (CDF) isolated from crown gall tumors of Vinca rosea L.

Energy Metabolism of Rumex Leaf Tissue in the Presence of Senescence-regulating Hormones and Sucrose

Abstract: Hormones which inhibit senescence of Rumex leaf tissue in the dark include gibberellin A(3), and the cytokinins 6-benzylamino purine and zeatin. These hormones inhibit respiratory metabolism in this tissue, but do not change the pattern or total amount of oxygen consumption during senescence. Abscisic acid, a senescence accelerator, correspondingly stimulates oxygen consumption. This correlation of senescence rate and respiration rate holds with regard to the hormone concentrations effective and the continued activity of the hormones when added after the lag phase of chlorophyll breakdown. Transfer experiments show that the respiratory inhibition due to gibberellin A(3) and the promotion due to abscisic acid become established within 3 hours of hormone addition. When gibberellin A(3) and zeatin were rapidly added to narrow strips of tissue, no inhibitions of oxygen uptake were observed in the first 12 minutes. Senescence-inhibiting concentrations of sucrose strongly stimulate respiratory meabolism, raise the respiratory quotient, and cause inhibition of chlorophyll and protein breakdown which is distinct from the effect of gibberellins or cytokinins.It is proposed that the gibberellins and cytokinins may act by inhibiting a rate-limiting process in the metabolism of starving leaf tissue. This rate-limitation hypothesis envisions a possibly subtle action of the hormone which retards but does not alter the pattern of macromolecular changes during cell autolysis.

Studies on phloem exudation from yucca flaccida haw. xiii. evidence for the occurrence of a cytokinin nucleotide in the exudate

Abstract: SUMMARY Phloem exudate of Yucca was analysed for cytokinin activity. After partition in a water- and butanol-1 fraction, almost no cytokinin activity was found in the butanol phase (cytokinin base and nucleosides). Application of alkaline phosphatase to the water layer gave rise to a strong positive cytokinin response with the soy-bean callus test, an amount of approximately 520 μg zeatin equivalent per litre being found in the exudate after treatment with alkaline phosphatase. The results indicate that a cytokinin, presumably zeatin, is translocated as a nucleotide.

Changes in leucyl, seryl, and tyrosyl tRNAs in aging soybean cotyledons

Abstract: Application of different concentrations of the naturally occurring cytokinin zeatin 6(4-hydroxy-3-methyl trans-2-butenylamino)purine caused changes in one or more species of tRNAs. With the depletion of storage products from senescing cotyledons quantitative changes in tRNAleu1, 5, 6, tRNAser1–3, and tRNAtyr1–4 were observed. Higher concentrations of zeatin applied as a single spray did not produce significant changes either in the cotyledon or the hypocotyl. The relationship of cytokinin activity to senescing soybean cotyledons is discussed.

Partitioning of Cytokinins between Ethyl Acetate and Acid Water Phases

Abstract: Model-experiments to determine the quantitative yield in purification of cytokinin extracts have been performed with kinetin, isopentenyladenine and zeatin and with their ribosides. When these substances in water solution of pH 3 are shaken three times with equal volumes of ethyl acetate, most of the kinetin and isopentenyladenine and their ribosides go over to the ethyl acetate phases. Zeatin and its riboside stay in the water phase. The unsuitability of using ethyl acetate to purify cytokinin extracts is pointed out.

Identification of Cell Division Inducing Compounds from Coconut Milk

Abstract: The use of chromatographic techniques coupled with mass spectrometry, infra-red analysis and nuclear magnetic resonance revealed that the amino acid phenylalanine might be responsible for a large proportion of the cell division activity of coconut milk as determined by the soybean bioassay. The observation that zeatin can be removed very readily by partitioning against ethyl acetate at alkaline pH values, cautions against inclusion of this method as a purification step for extracting cytokinins from plant extracts. Mass spectrometry revealed the presence of an unidentified cell division substance with a molecular ion of 279 and which co-chromatographed with zeatinriboside on Sephadex LH-20.

Evidence for the Presence of Cytokinins in Malt and Yeast Extracts

Abstract: Compounds that bring about growth in soybean callus were extracted from yeast and malt extracts. In the former most of the activity is due to a compound that co-chromatographed with zeatinriboside. This substance is also present in malt extract and coconut milk, together with a component which has the same elution volume as zeatin. Partition chromatography on Sephadex LH-20 revealed the presence of an extremely active unidentified substance in both malt extract and coconut milk. Indications are that this compound is not diphenylurea.

Identification d'une cytokinine par chromatographic en phase gazeuse à partir de cultures pures de Taphrina cerasi

Abstract: The ascomycete Taphrina cerasi (Fuck.) Sad., which induces malformations known as "witches’ brooms," when cultured in liquid media releases cytokinins. One of these, isolated from culture filtrates by ethyl acetate extraction, was identified as zeatin by paper chromatography, a biological test, and gas-liquid chromatography.

Callus growth and rooting of cassava (manihot esculenta crantz) stem segments cultured in vitro

Abstract: SUMMARY With the in vitro culture of cassava tissue the optimum sucrose level for callus growth is lower than that for the initiation and growth of roots. Auxin and cytokinin both promote callus growth, the latter by inducing cell division, the former also by stimulating cell elongation. In subcultures cytokinins are obligatory for callus growth, the natural cytokinins, zeatin and 2iP, yielding green tissues. Organ development never occurred in these subcultures. Auxin (NAA) is required for the initiation and growth of roots on the callus. Different cytokinins reduce this rooting effect in various degrees without, however, inducing the initiation of shoot primordia.

Effects of hormones on the polysaccharide-synthesizing membrane systems of lettuce pith.

Abstract: Changes have been induced in the polysaccharides laid down in the cell walls of lettuce pith by administration of the hormones auxin and zeatin. This polysaccharide derives from the membrane systems of the cells and radioactive precursor has been used to follow the accompanying changes which occurred in the polysaccharide contained within isolated Golgi and endoplasmic reticulum fractions. Zeatin-induced division and differentiation was accompanied by up to 12-fold increases in the amount of radioactivity in polysaccharide of isolated membrane fractions, and the pattern of distribution of label between the sugars of this polysaccharide was qualitatively different in the presence of zeatin. The change in this pattern was evident in the Golgi fraction at an earlier stage in the induction of the response than that in the endoplasmic reticulum.

Synthesis of trans-4-Amino-1-hydroxy-2-methyl-2-butene from Isoprene

Abstract: A novel synthetic pathway to trans-4-amino-1-hydroxy-2-methyl-2-butene (7), a useful synthetic intermediate of zeatin, is presented here. On selective monophthalimide formation, the trans-1, 4-dibromo-2-methyl-2-butene (10) prepared from isoprene (1) predominantly gives trans-1-bromo-2-methyl-4-phthalimido-2-butene (11). The compound (11) is converted to 7 via trans-1-acetoxy-2-methyl-4-phthalimido-2-butene (6). The overall yield of 7 from 1 is 33.6%. Base-catalyzed hydrolysis of 11 also gives 7 directly. Zeatin can be prepared by the condensation of 7 with 6-chloropurine.

Compounds Association with Cytokinin Activity in Fruitlets and Tracheal Fluid of Gossypium hirsutum

Abstract: Compounds that account for cytokinin activity in fruitlets and tracheal fluids of cotton (Gossypium hirsutum L.) were determined using preparations purified by thin-layer chromatography and gas–liquid chromatography and bioassayed with cultures of soybean stem callus tissue. At least five substances were found that stimulated growth of callus tissue. Among these, adenine and adenosine accounted for most of the growth stimulation of callus tissue. A compound with cytokinin activity was isolated with TLC properties similar to other known cytokinins, but its identity as zeatin, dihydrozeatin or N6-(Δ2-isopentenyl)-adenine was not confirmed using GLC and GLC combined with mass spectrometry. It was estimated that less than 1% of the cytokinin activity of this unknown substance could have been due to N6-substituted adenine derivatives.

SIMILAR EFFECTS OF CYTOKININS AND CARBONYL CYANIDE m-CHLOROPHENYLHYDRAZONE (CCCP) ON AMINO ACID TRANSLOCATION IN LEAVES OF SAGITTARIA GRAMINEA MICHX

Abstract: SUMMARY Kinetin, zeatin or zeatin riboside applied to parts of excised leaves of Sagittaria graminea change the distance profile of 14C-α-amino-iso-butyric acid translocation in these leaves. They probably enhance the rate of accumulation of the basipetally translocated amino acid. The metabolic inhibitor carbonyl cyanide m-chlorophenylhydrazone (CCCP) appeared to act in a very similar way on amino acid translocation; it also caused chlorophyll retention. Some possible cytokinin-CCCP relations are briefly discussed.