Showing papers on "Zeatin published in 1977"

Hormonal control of somatic embryo development from cultured cells of caraway: interactions of abscisic Acid, zeatin, and gibberellic Acid.

Abstract: The effects of abscisic acid, zeatin, and gibberellic acid on the development of somatic embryos from cultured cells of caraway ( Carum carvi L.) were observed. Somatic embryos complete development on a basal medium without exogenous hormones, but some are subject to developmental abnormalities including malformed cotyledons and accessory embryos. Both zeatin and gibberellic acid, especially in combination, stimulate growth and increase the frequency of aberrant forms. Zeatin causes the formation of multiple shoots, leafy and abnormal cotyledons, and in the dark, enlarged hypocotyls; gibberellic acid effects root elongation, polycotyledony, and some callus formation. In contrast, abscisic acid, at concentrations which do not inhibit embryo maturation, selectively suppresses abnormal proliferations. With abscisic acid, and especially in the dark, a high percentage of embryos complete development with two fleshy cotyledons on unelongated axes free of accessory embryos. In the light, zeatin eliminates abscisic acid inhibition while gibberellic acid only partially counters its effect, promoting elongated radicles and green rather than white cotyledons. In the dark, zeatin in combination with abscisic acid stimulates extensive callusing. Gibberellic acid does not reverse the effects of abscisic acid but rather enhances them and can counter the disruptive effects of zeatin. The results demonstrate that the balance between abscisic acid on the one hand and zeatin and gibberellic acid on the other can effectively control somatic embryo development and either disrupt or ensure normal maturation.

Induced Senescence of Intact Wheat Seedlings and Its Reversibility

Abstract: Intact wheat seedlings (Triticum aestivum L.) were induced to senesce by placing them in the dark and at various stages of senescence were placed back in the light and their recoverability observed. Seedlings demonstrated complete recovery of chlorophyll, protein, and rate of photosynthesis after 2 days in the dark, but were unable to recover fully after 4 days. This suggests the onset of an irreversible stage in senescence by day 4. Foliar applied cytokinins delayed senescence, and zeatin at 0.1 mm delayed the onset of the irreversible stage for 6 days. In addition to delaying the loss of total soluble protein, zeatin maintained the net protein recovery capacity of the tissue. Control seedlings, however, lost their potential for net protein recovery at a rate similar to their loss of total soluble protein. Treatment with zeatin had no apparent effect on dark respiration during senescence, and although treatment did delay the loss of membrane permeability to substrate, the change in permeability occurred too late to have a causal role in senescence.

Mass Spectroscopic Identification of Cytokinins Glucosyl Zeatin and Glucosyl Ribosylzeatin from Vinca rosea Crown Gall

Abstract: Mass spectrographic and chemical studies of the permethyl and trimethylsilyl ethers of two new cytokinins isolated from Vinca rosea crown gall callus cultures by Peterson and Miller (Plant Physiol 59: 1026-1028) indicate that they are 6-(4-0-beta-d-glucopyranosyl-3-methyl-trans-but-2-enylamino) purine (glucosyl zeatin) and 9-beta-d-ribofuranosyl-6 (4-0-beta-d-glucopyranosyl-3-methyl-trans-but-2-enylamino) purine (glucosyl ribosylzeatin). The nature of the mass spectra of the permethylated cytokinins suggests that these derivatives may have considerable utility in the detection of low levels of cytokinins in plant material.

Cytokinin as a Possible Component of the Floral Stimulus in

Abstract: Results of previous investigations indicated that one of the early and essential events occurring in the apical meristem of Sinapis alba L. during the transition to flowering is the release to mitosis of the G2 nuclei; the trigger to mitosis is generated in the leaves and its movement out of the leaves begins around 16 hours after the start of the inductive treatment. The mitotic wave in the meristem culminates 10 hours later. In this paper, it is shown that a single application of a cytokinin (benzyladenine or zeatin) at concentrations ranging from 1 to 20 ,g/ml directly to the apical bud of vegetative plants, at a time corresponding to the time of movement of the mitotic trigger in induced plants, produces a mitotic wave which is very similar to that found in induced plants. It is thus proposed that the mitotic component of the floral stimulus in Sinapis is a cytokinin. As the cytokinins are completely unable to induce flowering, it appears that there is a multicomponent floral stimulus in this species.

Cytokinin as a Possible Component of the Floral Stimulus in Sinapis alba.

Abstract: Results of previous investigations indicated that one of the early and essential events occurring in the apical meristem of Sinapis alba L. during the transition to flowering is the release to mitosis of the G 2 nuclei; the trigger to mitosis is generated in the leaves and its movement out of the leaves begins around 16 hours after the start of the inductive treatment. The mitotic wave in the meristem culminates 10 hours later. In this paper, it is shown that a single application of a cytokinin (benzyladenine or zeatin) at concentrations ranging from 1 to 20 μg/ml directly to the apical bud of vegetative plants, at a time corresponding to the time of movement of the mitotic trigger in induced plants, produces a mitotic wave which is very similar to that found in induced plants. It is thus proposed that the mitotic component of the floral stimulus in Sinapis is a cytokinin. As the cytokinins are completely unable to induce flowering, it appears that there is a multicomponent floral stimulus in this species.

Glucosyl Zeatin and Glucosyl Ribosylzeatin from Vinca rosea L. Crown Gall Tumor Tissue

Abstract: Recently detected but unidentified cytokinin activity in crown gall tumor tissue from Vinca rosea L grown on media containing sources of reduced nitrogen has now been attributed to two adenine-type cytokinins These compounds are glucopyranosyl derivatives of zeatin and ribosylzeatin The substitution in each case is on the isopentenyl chain of the parent compound Neither of these compounds had activity in the soybean callus bioassay at concentrations lower than 1 nm whereas zeatin had activity at 01 nm

Polyribosome Formation in Relation to Cytokinin-induced Cell Division in Suspension Cultures of Glycine max [L.] Merr.

Abstract: We have investigated the relationship between cell proliferation and protein synthetic capacity in a cytokinin-requiring strain of cultured soybean cells (Glycine max [L.] Merr. cv. Sodifuri, of cotyledonary origin) in suspension culture. When transferred to a defined medium lacking cytokinin, very little cell division or cell enlargement took place over the course of a 6-day culture period. Cells transferred to medium of the same composition, but containing 0.5 μm zeatin, exhibited rapid initial growth, with maximum mitotic activity occurring after 24 hours in culture, and a doubling of the cell population within the first 36 hours of the culture period. The polyribosomal RNA content of the cells decreased over the course of the first 24 hours of the growth cycle while the polyribosome to monoribosome (P/M) ratio increased. The increase in the P/M ratio was greater in the cytokinin-treated cells. This apparent relationship between cytokinin-induced cell proliferation and polyribosome formation was examined further. Polyribosome formation was stimulated when zeatin was added directly to cell populations which had been cultured for 24 hours in medium lacking a cytokinin. Transfer to fresh medium alone also stimulated polyribosome formation, whether this medium contained a cytokinin or not. The magnitude of transfer-induced polyribosome formation depended upon the initial cell density (number of cells/ml of medium). Regardless of the initial cell density and independent of the P/M ratios attained, the cytokinin-treated cell populations divided while the cytokinin-deprived cell populations did not. In vivo labeling with [35S]methionine and slab gel electrophoretic separation of sodium dodecyl sulfate derivatives of the labeled polypeptides demonstrated qualitative changes in the spectrum of proteins synthesized by the cytokinin-treated cells. These qualitative changes were independent of the cell density (and hence, independent of the P/M ratio) but they preceded cytokinin-induced cell division.

Polyribosome Formation in Relation to Cytokinin-induced Cell

Abstract: We have investigated the relationship between cell proliferatioon annd protein synthetic capacity in a cytokinin-requiring strain of cultured soybean cells (Glycine max [L.] Merr. cv. Sodifun, of cotyledonary origin) in suspension culture. When transferred to a defined medium lacking cytokinin, very Uttle cell division or cell enlargement took place over the course of a 6-day culture period. Cells transferred to medium of the same composition, but containing 0.5 FiM zeatin, exhibited rapid initid growth, with maximum mitotic activity occurring after 24 hours in culture, and a doubling of the cell population within the first 36 hours of the culture period. The polyribosomal RNA content of the cells decreased over the course of the firt 24 hours of the growth cycle whie the polyribosome to mononrbosome (P/M) ratio increased. The increase in the P/M ratio was greater in the cytokinin-treated cells. This apparent relationship between cytokinin-induced cell prolferation and polynbosome formation was examined further. Polyribosome formation was stimulated when zeatin was added directly to cel populations which had been cultured for 24 hours in medium lackcing a cytokinin. Transfer to fresh medium alone also stimulated polyn'bosome formation, whether this medium contained a cytokinin or not. The magnitude of transferinduced polyribosome formation depended upon the initial cel density (number of cells/ml of medium). Regardless of the initial cel density and independent of the P/M ratios attained, the cytokinin-treated cell populations divided while the cytokinin-deprived ceil populations did not. In vivo labeling with p35Smethionine and slab gel electrophoretic separation of sodium dodecyl sulfate derivatives of the labeled polypeptides demonstrated qualitative changes in the spectrum of proteins synthesized by the cytokinin-treated cells. These qualitative changes were independent of the cell density (and hence, independent of the P/

Biological Activity of O-β-d-Glucopyranosylzeatin

Abstract: Concentrations of 10−8 to 10−5m O-β-d-glucopyranosylzeatin are less active than zeatin and zeatin riboside in the soybean (Glycine max L.) callus bioassay. At a concentration of 10−4m the glucoside was, however, more active or alternatively less toxic than similar concentrations of zeatin and zeatin riboside. Applied zeatin-O-glucoside is readily metabolized by soybean callus and both zeatin and zeatin riboside could be extracted from callus grown on basal medium containing the O-glucoside.

Seasonal Changes in the Cytokinin Content of the Leaves of Salix babylonica

Abstract: The young and old leaves of Salix babylonica contain at least four cell division-inducing compounds which coeluted with zeatin, zeatin riboside and their glucosylated derivatives. During the course of the growing season quantitative changes in the cytokinin content of the leaves were observed. The cytokinin glucosides increased as the leaves aged. The compounds which co-chromatographed with zeatin and zeatin riboside initially increased until early autumn and then decreased as the leaves senesced. It appears as though the cytokinins transported from the roots are metabolized in the leaves and are converted to their glucosides. Although it has been reported in the literature that Salix root exudate contains very small amounts of cytokinin in late summer and autumn, these compounds increase in the leaves for most of the growing season, suggesting that the leaves may not only obtain cytokinins from the roots but may well be an active site of cytokinin synthesis. It is, however, possible that cytokinins are also transported to the leaves via the phloem, thus accounting for their accumulation in these organs.

The development of isolated roots of comptonia peregrina (myricaceae) in culture

Abstract: Seedling roots of the sweet fern Comptonia peregrina (L.) Coult. were excised aseptically and cultured in a modified Bonner-Devirian liquid nutrient medium. Root elongation was very slow in the basic medium which contained inorganic salts, B-vitamins, trace elements and 4%o sucrose. The addition of plant hormones including gibberellic acid, indoleacetic acid, and zeatin, alone or in combinations, had little effect on growth. Myoinositol at 10 or 100 ppm doubled the rate of elongation. The effect of this sugar alcohol could not be replaced by scyllitol, D-sorbitol, D-mannitol or by increasing the sucrose concentration. Subcultured root tips showed progressively less elongation in successive transfers. Secondary thickening of the roots, especially in the basal half, occurred in initial passages and in subcultured roots without added hormones. Root buds also occurred spontaneously especially in the basal portions of cultured roots, both in first and in successive passages. An anatomical analysis showed that these buds were endogenous, arising from a secondary cortex of pericyclic origin. ISOLATED ROOTS of herbaceous species growing in sterile nutrient culture solutions have provided experimental systems for the study of various problems including root nutrition, lateral root and bud formation, secondary thickening and nodule development (Torrey, 1965). Although establishing roots of woody plants in culture has been a difficult process, limited success has been achieved with the following plants: Acacia melanoxylon R. Br. (Bonner, 1942), Robinia pseudoacacia L. (Seeliger, 1956), Pinus spp. (Slankis, 1947; Barnes and Naylor 1959; Ulrich, 1962), Acer rubrum L. (Bachelard and Stowe, 1963)

Effect of Different Cytokinins on Ethylene Production by Mung Bean Hypocotyls in the Presence of Indole-3-Acetic Acid or Calcium Ion

Abstract: Kinetin has been shown to act synergistically with indole-3-acetic acid (IAA) or calcium ion (Ca2+) to stimulate ethylene production. Several commercially available cytokinins (kinetin, kinetin-riboside, benzyladenine, benzyladenine-riboside, isopentenyladenine, isopentenyladenine-riboside, and zeatin) as well as noncytokinin bases (adenine and xanthine) were administered to mung bean (Phaseolus aureus Roxb.) hypocotyls to study their effects, alone or in combination with IAA or Ca2+, on ethylene production. In the presence of IAA or Ca2+, all cytokinins tested synergistically stimulated ethylene production and were as effective or nearly as effective as kinetin. Noncytokinin bases (adenine and xanthine) were, however, inactive in this system.

Cytokinins in xanthium strumarium l.: the metabolism of cytokinins in detached leaves and buds in relation to photoperiod

Abstract: SUMMARY Endogenous cytokinin activity in leaves and buds of Xanthium strumarium L. (as estimated by the soybean callus bioassay) declined by about 80% during the 24 h following detachment from the plant. The decline in activity was little influenced by the photoperiod to which the detached organs were exposed. When zeatin was supplied to detached leaves it underwent rapid metabolism. The main cytokinin-active metabolite, which was readily detectable an hour after the start of zeatin uptake, eluted from a Sephadex LH20 column with the same elution volume as zeatin riboside. Substantial differences due to photoperiod, in either the rate or the pattern of zeatin metabolism, were not detected.

A Comparison of the Endogenous Cytokinins in the Roots and Xylem Exudate of Nematode-resistant and Susceptible Tomato Cultivars

Abstract: Non-infested roots of a tomato cultivar (Roodeplaat Premier) susceptible to root-knot nema todes contained higher levels of endogenous cytokinins than non-infested roots of a nematode resistant cultivar (Master Fl). In both cultivars nematode infestation increased the cytokinin level in the roots. Sephadex LH-20 fractionation indicated that the xylem exudate of infested susceptible plants contained zeatin and zeatin riboside. In the roots of both cultivars a third compound, which co-eluted with zeatin glucoside, was present. The activity of all three cell division-inducing compounds was higher in the roots of susceptible plants than in roots of nematode-resistant plants. The present results support the hypothesis that cytokinins may be a controlling factor in the development of giant cells.

A Cytokinin Complex in the Developing Fruits of Lupinus albus

Abstract: The apices of Lupinus albus L. were analysed for cytokinin activity at three stages of development. Little cytokinin activity could be detected in the apices at the time of flowering. However, a considerable amount of activity was detected as the fruits developed. Separate analyses of seed and pod material indicated that there was a high level of cytokinin in both these parts of the fruit. After fractionation of the peaks of activity obtained from paper chromatograms on Sephadex LH-20, four peaks of cytokinin activity were recorded. Two of these co-eluted with zeatin and zeatin riboside. A third peak at an elution volume of 360–440 ml could be hydrolysed with β-glucosidase to give activity at elution volumes corresponding to those of zeatin and zeatin riboside. This strongly suggested that both glucosylated zeatin and glucosylated zeatin riboside were present in the developing fruits of L. albus. The fourth peak at an elution volume of 160–280 ml did not disappear upon hydrolysis with β-glucosidase, and it is possible that it represented a nucleotide cytokinin.

Enzymatic synthesis of lupinic acid, a novel metabolite of zeatin in higher plants.

Abstract: Lupinic acid (III), a metabolite of the phytohormone zeatin (I), was synthesized from O-acetyl-L-serine (II) and zeatin by an enzyme in higher plants. Some properties of the enzyme are described.

Changes in Auxin and Cytokinin Activity in Roots of Red Oak, Quercus rubra, Seedlings during Lateral Root Formation

Abstract: Quercus rubra L. seedlings were partially root pruned to induce formation of new laterals. Auxins in root extract fractions that cochromatographed with IAA, and cytokinins in root xylem sap fractions that cochromatographed with zeatin and zeatin riboside, were quantified by bioassays at 24 h intervals after pruning. Auxin activity sharply increased in the first 24 h and then decreased to prepruning levels. Cytokinin activity also increased during the first 24 h. New laterals appeared 4 to 5 days after pruning. The possible sources and role of these two hormones in root initiation are discussed.

Primary phloem regeneration without concomitant xylem regeneration: its hormone control in coleus

Abstract: A B S T R A C T Phloem regeneration in the absence of xylem regeneration was evoked in number 5 internodes of Coleus blumei Benth. by severing xylemless phloem bundles. Its quantitative extent was estimated. To determine whether phloem regeneration is directly affected by auxin, or whether it is a secondary consequence of the auxin-dependent xylem regeneration which usually accompanies it, phloem regeneration was measured in decapitated plants from which auxinproducing leaves and buds had been removed (i.e., in "plant stumps"). In these stumps, 1% IAA in lanolin completely restored phloem regeneration to the intact plant level. In such stumps from which roots had been excised, and in excised internodes, IAA failed to restore it to this level. However, zeatin or zeatin riboside in aqueous solution applied to the bases of excised internodes receiving IAA at their apical ends restored phloem regeneration to the level of that in whole plants. When similarly tested, other cytokinins (kinetin, kinetin riboside, 2iP, and 2iPA), gibberellic acid (GA3), glutamine, proline, sucrose, and a mixture of mineral salts failed to promote phloem regeneration. Glutamic acid, tested only once, was slightly promotive of it.

Hormones in Plants Bearing Nitrogen-fixing Root Nodules: Distribution and Seasonal Changes in Levels of Cytokinins in Alnus glutinosa (L.) Gaertn

Abstract: The root nodules of both dormant and non-dormant plants of Alnus glutinosa (L.) Gaertn. were found (by the soybean callus bioassay) to contain levels of cytokinin activity greatly exceeding those of other parts of young vegetative plants. A large, transient increase in cytokinin activity occurred in the nodules at the time of bud break. Similar, although much smaller, increases were detected also in roots and buds. The increase in the level of nodule cytokinin activity was observed both in mature trees and in young pot-grown plants in two successive years. A second peak of cytokinin activity, considered to be derived from cytokinin nucleotides, was found in the nodules of mature trees in mid summer. Analysis of cytokinin extracts of different plant parts by means of a Sephadex LH20 column revealed the presence of three main peaks of activity, with elution volumes corresponding to those of zeatin-9-glucoside, zeatin riboside, and zeatin. While the glucoside-like peak was predominant in the nodules and leaves it was not detected in root pressure sap. A zeatin ribo side-like peak was the major cytokinin in the roots and root pressure sap. These findings are discussed in relation to current hypotheses concerning the production, distribution, and possible physiological roles of the cytokinins.

The Effect of Ringing on Cytokinin Distribution in Salix baylonica

Abstract: Although quantitative differences were observed in the cytokinin content of mature leaves and bark of Salix babylonica it would appear as if these tissues contained the same cytokinin complement. Ringing resulted in a decrease in the level of cytokinins in the leaves and an increase in the bark, both above and below the girdle. In the leaves the decrease was due mainly to a drop in the level of those compounds that co-chromatographed with the cytokinin glucosides. These compounds were also almost undetectable in the bark above the girdle, where callus was formed. The observed increase in the cytokinin content of the bark above the girdle was due to higher activity in those parts of the chromatograms where zeatin and zeatin riboside occurred. Ringing stimulated the growth of lateral buds below the girdle. These developing buds as well as the bark below the girdle contained very high levels of cytokinins that cochromatographed with zeatin and zeatin riboside.

Hormones in Plants Bearing Nitrogen-fixing Root Nodules: Metabolism of [8-14C]Zeatin in Root Nodules of Alnus glutinosa (L.) Gaertn

Abstract: The metabolism of [8-14C]zeatin, supplied via micropipettes over a 24 h period to root nodules of Alnus glutinosa (L.) Gaertn., was investigated. The major metabolites were tentatively identified by means of chromatographic, chemical, and enzymic treatments as adenine, adeno sine, trans-zeatin riboside, dihydrozeatin, irans-zeatin-0-j3-D-glucoside, and the O-fi-D glucoside of dihydrozeatin. In addition, a prominent water-soluble peak of radioactivity was present. This did not appear to be a riboside but was biologically active in the soybean callus test. The number and nature of the metabolites formed in the nodules was similar in both dormant

Effects of photoperiod and temperature on the growth and cytokinin content of two populations of dactylis glomerata (cocksfoot)

Abstract: SUMMARY The effects of photoperiod (8 or 16 hr, SD or LD) and temperature (low or high, 8° or 20°C) on the growth and cytokinin content of Norwegian and Portuguese populations of Dactylis glomerata (Cocksfoot) were investigated. In general, conditions which promote active leaf growth (LD or high temperature) of plants of the Norwegian population tend to result in lower levels of cytokinin bases and/or nucleosides and in higher levels of ‘nucleotide’ cytokinins than conditions which lead to reduced growth rate (SD or low temperature). In some ‘transfer’ experiments the changes in hormone levels preceded detectable changes in growth rate. Cytokinins which behaved similarly to zeatin and zeatin riboside on Sephadex LH 20 columns were detected. The lack of response to application of exogenous zeatin or 6-benzylaminopurine, together with the data on endogenous cytokinins, suggests that the level of cytokinin bases and nucleosides was not limiting the growth rate of the Norwegian population in SD at 8°C. However, if ‘nucleotide’ cytokinins are significant for growth rate under unfavourable conditions then this class of hormone may be involved in the responses to day length and temperature.

Hormonal Control ofSomatic EmbryoDevelopment from Cultured Cells ofCaraway

Abstract: Theeffects ofabscisic acid, zeatin, andgibberellic acid onthedevelopmentofsomatic embryos fromcultured cells ofcaraway (Carumcarvi L.)wereobserved. Somatic embryos complete development onabasal mediumwithout exogenous hormones, butsomearesubject todevelopmental abnormalities induding malformed cotyledons andaccessory embryos. Bothzeatin andgibberellic acid, especialy incombination, stimulate growthand increase thefrequency ofaberrant forms. Zeatin causes theformation of multiple shoots, leafy andabnormal cotyledons, andinthedark,enlarged hypocotybls; gibberelic acideffects rootelongation, polycotyledony, andsomecaflus formation. Incontrast, abscisic acid, atconcentrations whichdonotinhibit embryo maturation, selectively suppresses abnormal proliferations. Withabscisic acid, andespecially inthedark, a highpercentage ofembryos complete development withtwofleshy cotyledons onunelongated axesfree ofaccessory embryos. Inthelight, zeatin eliminates abscisic acid inhibition while gibberellic acid onlypartially counters itseffect, promoting elongated radicles and greenrather thanwhitecotyledons. Inthedark, zeatin incombination withabscisic acidstimulates extensive callusing. Gibberellic aciddoes notreverse theeffects ofabscisic acid butrather enhances themandcan counter thedisruptive effects ofzeatin. Theresults demonstrate that thebalance between abscisic acid onthe onehandandzeatin andgibberellic acid ontheother caneffectively control somatic embryo development andeither disrupt orensure normalmaturation.