Showing papers on "Kinetin published in 1974"

The Metabolism of Oat Leaves during Senescence: I. Respiration, Carbohydrate Metabolism, and the Action of Cytokinins

Abstract: When the detached first leaves of green or etiolated oat (Avena sativa cv. Victory) seedlings senesce in the dark, their oxygen consumption shows a large increase, beginning after 24 hours and reaching a peak of up to 2.5 times the initial rate by the 3rd day. This effect takes place while the chlorophyll of green leaves, or the carotenoid of etiolated leaves, is steadily decreasing. Kinetin, at a concentration which inhibits the decrease in pigment, completely prevents the respiratory rise; instead, the oxygen consumption drifts downwards. Lower kinetin concentrations have a proportional effect, 50% reduction of respiration being given by about 0.1 mg/l. About one-fifth of the respiratory rise may be attributed to the free amino acids which are liberated during senescence; several amino acids are shown to cause increases of almost 50% in the oxygen consumption when supplied at the concentrations of total amino acid present during senescence. A smaller part of the rise may also be due to soluble sugars liberated during senescence, largely coming from the hydrolysis of a presumptive fructosan. The remainder, and the largest part, of the increase is ascribed to a natural uncoupling of respiration from phosphorylation. This is deduced from the fact that dinitrophenol causes a similar large rise in the oxygen consumption of the fresh leaves or of leaf segments kept green with kinetin, but causes only a very small rise when the oxygen consumption is near its peak in senescent controls. The respiration of these leaves is resistant to cyanide, and 10 mm KCN even increases it by some 30%; in contrast, etiolated leaves of the same age, which undergo a similar rise in oxygen consumption over the same time period, show normal sensitivity to cyanide. The respiratory quotient during senescence goes down as low as 0.7, both with and without kinetin, though it is somewhat increased by supplying sugars or amino acids; glucose or alanine at 0.3 m bring it up to 1.0 and 0.87, respectively.N(6)-Benzylaminopurine and Delta-2-isopentenylaminopurine act similarly to kinetin in repressing the respiratory rise, the former being five times as active as kinetin, while the latter has only 1% of the activity of kinetin. Zeatin also powerfully prevents senescence. Because the repression of the respiratory rise is shown by each cytokinin at the concentration at which it inhibits senescence, the action is ascribed in both cases to the maintenance of a tight coupling between respiration and phosphorylation. It is pointed out that such an effect would explain many features of cytokinin action.A change in the methodology of the senescence experiments is described and compared with the method previously used, and the influence of temperature and age of the plants on the course of leaf senescence are presented in detail.

Regulation of organogenesis in small explants of superficial tissue of Nicotiana tabacum L.

Abstract: Small explants composed of 3-6 layers of epidermal and subepidermal cells excised from floral branches of Nicotiana tabacum are capable of de novo organogenesis. Continuous mitoses without organogenesis, or mitoses followed by the formation of floral buds, vegetative buds or roots can be obtained by varying the auxin-cytokinin-sucrose ratio in the medium. The physiological stage of the floral branches, and light and darkness had also an influence on the de novo organogenesis. Best floral-bud formation was obtained when explants were taken from plants in which the terminal bud was in the green-fruit stage, and were cultured on a medium with indole-3-acetic acid and kinetin both at 10(-6) M and with 3% sucrose, in the light. For differentiation of vegetative buds, the optimal auxin/cytokinin ratio was one tenth of that for floral-bud formation, while the sucrose concentration was the same. Optimal conditions for root formation were: explants from plants in which the terminal bud carried a mature fruit; 10(-7) M kinetin, 10(-5) M indole-3-butyric acid, and 1% sucrose in the medium; and culture in darkness. The optimal medium for callus formation contained 5×10(-6)M 2,4-dichlorophenoxyacetic acid, 10(-7) M kinetin and 3% sucrose.

Organogenesis and Plantlet Formation In vitro in Almond

Abstract: The present report deals with the dedifferentiation and formation of callus from excised plant parts of seedlings of Prunus amygdalus and the regeneration of complete plants from the callus thus obtained in vitro. The basal medium employed was that of Murashige and Skoog, supplemented with various adjuvants. The different plant parts, i.e., stem, leaf, root, hypocotyl, cotyledon, and shoot tip could be stimulated to form callus. These calluses showed optimal growth on the basal medium + naphthaleneacetic acid ( 5 ppm) + coconut water ( 109 ) . Isolated roots, leaves, or shoots differentiated on the calluses cultured on basal medium + naphthaleneacetic acid (5 ppm) + casein hydrolysate (1 g/liter) and in a few cases also whole plants developed when this medium was supplemented with kinetin or other cytokinins. However, typical embryoids have not been observed so far. Callus cells were diploid, triploid, tetraploid, or aneuploid. Regenerated plants were diploid. Isolated roots that differentiated were also invariably diploid.

The effect of kinetin and abscisic acid on water and ion transport in isolated maize roots

Abstract: Summary Exudation from the xylem of excised maize roots was studied in roots bathed in solutions containing kinetin or abscisic acid (ABA). Kinetin reduced the water permeability of the roots whilst ABA increased it. The action of both hormones was reversible and both were effective at concentrations of 10-6M and below. The possible in vivo role of these two hormones is discussed.

The Action of Kinetin in Improving the Water Balance and Delaying Senescence Processes of Cut Rose Flowers

Abstract: Kinetin delays the fading of cut rose (Rosa hyb. cv. Golden Wave) flower shoots exposed to water stress conditions. Using leafless flower shoots (i.e., a plant system devoid of stomates), we demonstrated that the main initial effect of kinetin was on increasing water uptake and petal growth. Later, kinetin slowed down processes associated with both senescence and stress (RNase activity and dry weight reduction), and maintained petal turgidity for an extended period.

Embryogenesis and Organogenesis in Pumpkin Explants

Abstract: Embryogenic callus was induced by culturing explants of pumpkin hypocotyls on Murashige-Skoog-medium with the addition of 3% glucose and one of the following growth substances (or combinations of them): β-indolylbutyric acid, 2,4-dichlorophenoxyacetic acid, β-indolylacetic acid, α-naphthyl-acetic acid, adenine (natural), kinetin, autoclaved water-melon sap and yeast extract (Difco). A large number of embryoids and adventive buds were produced. These were able to develop to normal plants. The 17 strains of embryogenic tissue obtained have maintained their embryogenic characteristics for more than 3 years. The induction of embryogenic callus in pumpkin seems to be strongly dependent on the genetic constitution of each individual plant.

Plantlet formation from Lycopersicon esculentum leaf callus

Abstract: Explants were obtained from leaves of three strains of tomato and grown on a modified Murashige and Skoog's medium with various combinations of indole-3-acetic acid (IAA) and kinetin. Callus proliferation began by 8–10 days. Root initiation was very common, particularly at 2 mg/liter IAA and 2 mg/liter kinetin. Shoot formation occurred within 30 days but only at a specific combination of concentrations of the two growth hormones (4 mg/liter IAA + 4 mg/liter kinetin). Most shoots became plantlets by 10 days after transfer to basal Murashige and Skoog's medium. Shoot-forming potential was neither correlated with callus-forming potential nor with vigor of strain.

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.

La formation des nodules fixateurs d'azote chez alnus glutinosa (l.) vill.

Abstract: SUMMARY In the present study a verification is undertaken of the research published so far on the formation of root nodules in alder plants (Alnus glutinosa (L.) Vill.) as a result of a symbiosis between the host plant and an endophyte, probably an actinomycete. After a brief discussion of the growth of the endophyte within the cortex of the host root and of the morphogenesis of root nodules, the hypothesis to the effect that a root nodule is a modified lateral root was tested. This possibility had to be rejected and the conclusion was drawn that root nodules appear adventitiously in-between the normal points of lateral root production. As, from an anatomical point of view, a nodule shows a great deal of resemblance to a lateral root, the hypothesis was formulated that root nodules are adventitious lateral roots – induced by an endophyte – which develop into nodules following the penetration of their cortex by the endophyte. In order to imitate and study the reactions in the host plant set in motion by the endophyte, phytohormones were administered to whole plants as well as to explants of roots. Use was made of kinetin and the following auxins: indole-3-acetic acid (IAA), indole-butyric acid (IBA), naphtalene-acetic acid (NAA), and 2,4-dichlorophenoxy-acetic acid (2,4-D). The auxins and the mixture of 2,4-D and kinetin produced an induction of primordia; by means of IBA, moreover, a slight increase in the number of nodules in the inoculation experiments was obtained. Finally, some experiments with tetrazolium salts were undertaken in order to ascertain whether the reducing conditions which are essential for the reduction of atmospheric nitrogen are already present in young nodules. Seventeen days after the inoculation a reduction of tetrazolium could be observed on the vesicles.

Effects of Chemical and Physical Conditions on Growth of Camptotheca acuminata Cell Cultures

Abstract: Callus was induced from Camptotheca acuminata, which produces an antitumor alkaloid, carnptothecin. Using the Murashige and Skoogs’ medium as the basal, cultural conditions were examined for C. acuminata suspension cultures. As a result, a medium, containing 0.1 mg/liter 2,4-D, 3 mg/liter kinetin and 0.05 mg/liter GA3, was established as a medium that gave the best cell growth in suspension cultures. In addition, conditioning of medium and addition of 0.115 mm l-Trp and l-Phe to medium promoted remarkably growth of cell suspensions.

Internal Water Status of Kinetin-treated, Salt-stressed Plants

Abstract: Stomatal resistances and turgor pressures were measured during a 12-day period on leaves of bean (Phaseolus vulgaris L cv Contender) which were treated with kinetin, were salinized or were treated with kinetin and salinized Stomatal resistances were highest in salt-stressed plants, and progressively lower in salt-stressed and kinetin-treated plants, control plants, and kinetin-treated plants Turgor pressures were highest in salt-stressed plants, and progressively lower in control plants, kinetin-treated plants, and salt-stressed and kinetin-treated plants Stomata appeared to be kept open more widely under kinetin treatment than under control conditions, even when turgor pressures were lower in kinetin-treated plants than in control plants

Response to boron deficiency: a comparison with responses produced by chemical methods of retarding root elongation

Abstract: Summary Seedlings of Vicia faba L. were subjected to treatments with IAA, 2,4-D, tri-iodobenzoic acid, kinetin, 2-chloroethanephosphonic acid as well as those designed to prevent normal division in the primary meristem. Where division was inhibited with colchicine, trifluralin, dinitramine or surgical excision, a radial expansion of the root tip occurred. However, the anatomical aspects of the responses and their effects on phosphate absorption and incorporation were quite distinct from the effects produced in both boron deficiency and excess auxin treatments. Kinetin gave similar effects to mitotic inhibitors. The possibility that boron deficiency is associated with an excess level of endogenous auxin was examined. The effects of boron deficiency were compared with those associated with the presence of excess auxin.

Tissue Culture of Eucalyptus

Abstract: SUMMARY Five species of Eucalyptus (E bancroftii, E nicholii, E laevopinea, E melliodora and E grandis) have been brought into tissue culture on media devoid of coconut milk One of these species (E bancroftii) grows vigorously on a completely defined medium; the other four require casein hydrolysate for rapid growth Roots have been induced to regenerate from undifferentiated callus on media containing either 2,4-D or various combinations of IAA and kinetin

Nutritional and morphogenetic investigations on callus cultures of neomammillaria profilera miller (cactaceae)

Abstract: A B S T R A C T Neomammillaria prolifera (Cactaceae), when grown on Murashige and Skoog's medium supplemented with fresh coconut milk, showed very little growth. Various concentrations and combinations of growth regulators which did not cause callusing had no apparent effect on the normal growth rates of intact plants. Healthy green calli obtained on a 2,4-D and kinetin-containing medium exhibited extremely fast growth and very specific growth requirements. Relatively high amounts of 2,4-D (10-20 mg/liter), kinetin (1-2 mg/liter), and coconut milk (20-60 %) were required at all times for continued proliferation of callus on subculturing. Moreover, the callus was very tolerant to extremely high concentrations of other growth regulators (IAA, NAA, IBA, and GA up to 100 mg/liter) in the presence of 2,4-D and coconut milk. These substances could not replace 2,4-D for callusing or continued growth of callus. It was not possible to establish root cultures or to induce callusing of roots. Attempts to induce differentiation in callus were unsuccessful, except for sporadic root initiation in some cultures. A comparison of these results with similar studies on other succulents demonstrates some basic physiological similarities among this group of plants.

The Effect of Hadacidin on Bud Development and its Implications for Apical Dominance

Abstract: Hadacidin, which is known to inhibit the enzyme adenylo-succinate synthetase, was applied locally to lateral buds on decapitated Pisum sativum L. plants. In controls the buds grew out normally, but the treated buds were almost completely inhibited. After a delay, the buds overcame the inhibition, and their subsequent outgrowth could be further hastened by the local application of a cytokinin. The inhibition, unlike that due to IAA, was not transported to a second bud, and it could be largely reversed by kinetin or dimethylallylaminopurine. Adenine itself produces little or no reversal, however. There was some reversal by aspartic acid, which is known to reverse, at least partially, the hadacidin inhibition of the isolated enzyme. It is deduced that lateral bud development is dependent on the synthesis of a cytokinin, which may take place by a biochemical route similar, but probably not identical, to that for adenine. It follows that this synthesis takes place locally in the bud itself.

[Influence of light and medium on the plating efficiency of isolated cells from callus cultures of Nicotiana tabacum var. "Samsun"].

Abstract: Light increases the plating efficiency of single cells isolated from green callus cultures of Nicotiana tabacum var. "Samsun" and plated in densities of less than 100 cells ml(-1) by more than 100%. At optimal light intensities plating efficiences between 80 and 90% were achieved with green cells, whereas the growth of isolated cells from chlorophyll free callus cultures was inhibited by light.Plated at low densities the isolated tobacco cells require the addition of kinetin and glutamine to a modified Murashige-Skoog-Medium for growth. The addition of these two substances is not necessary in the case of callus cultures or at higher plating densities (i.e. 500 or more cells ml(-1)). The requirement of kinetin for the growth of isolated cells can be met by the addition of small amounts of conditioned media from suspension cultures to the modified M+S-medium supplemented with glutamine, which demonstrates the production and release of a highly active cytokinine by the cells.

Synergistic effect of calcium and kinetin on ethylene production by the mungbean hypocotyl

Abstract: A slight increase in ethylene production resulted from the application of either kinetin or Ca2+ to mungbean (Phaseolus mungo L.) hypocotyl segments, but a remarkable synergistic increase in C2H4 production was observed when they were applied together. The induction time was about 6 h as compared to 1 h for auxin-induced C2H4 production. A slight stimulation of C2H4 production was also observed when Ca2+ was applied with abscisic acid, but no synergistic effect of Ca2+ was observed with indole-3-acetic acid or GA3.

The role of exogenous plant regulators in the dormancy of onion bulbs

Abstract: Experiments were conducted to study the effect of plant injection with growth regulators on the dormancy of onion bulbs cv. Elba Globe. Application of abscisic acid induced early senescence of the leaves and prolonged the rest period of the bulbs. This effect was partially overcome by subsequent applications of gibberellin, auxin or cytokinin and totally overcome with the application of a mixture of the three hormones. Maleic hydrazide application prolonged the rest period by inhibiting both sprouting and rooting of the bulbs throughout the storage period. This inhibitory effect was not overcome by the subsequent application of auxin, gibberellin, kinetin, or their combinations. Ethephon application increased rooting of bulbs and partially overcame the effect of abscisic acid on dormancy.

Induced differentiation of buckwheat plants from subcultured calluses in vitro

Abstract: For callus induction and restoration of plants from callus tissue of buckwheat, kinetin showed no effect, but supplements of 2, 4-D (10mg/l) to White's basal medium induced calluses from germinating seeds. Callus tissues subcultured for 48 months grew vigorously on the modified White's basal medium.Nearly 40.5% of cells of callus tissues which were subcultured 6-36 months had the diploid chromosome number 16. The cell population became much more uniform in chromosome number after a longer period of subculture.Shoot and root formation were not found on the proliferating calluses in White's basal medium and modified white's basal medium. However, transfer to modified RM-1964 medium after one or two months resulted in a tendency towards organ-forming capacity.The five restored plants obtained showed normal chromosome constitution.

Organ formation from the excised bulb scales of Hippeastrum hybridum in vitro

Abstract: SummaryThe excised bulb scales of amaryllis (Hippeastrum hybridum), cultured on Murashige and Skoog’s medium supplemented with combinations of NAA and kinetin, developed buds or roots or both together. The patterns of organogenesis were governed by the concentration of NAA in the medium. On the other hand, kinetin was not only less effective but was also toxic at high concentrations.

Embryo Dormancy in Seeds of Acer platanoides

Abstract: On dispersal the seed of Acer platanoides contained a dormant embryo, from which dormancy could be removed by chilling but not by hormone application. Dormany was deep in the embryonic axis, particularly in the radicle, but less so in the cotyledons. Under the storage conditions employed the dormancy pattern was modified so that during the subsequent incubation at 20°C, cotyledon expansion of isolated embryos from stored fruits was more rapid than that of isolated embryos from newly dispersed fruits. In addition, the dormancy of isolated embryos from fruits stored for several weeks could be broken by incubation in kinetin. It was concluded that embryo dormany in this seed can be divided into two phases, an initial phase when the embryo responds to chilling but not to cytokinins, and a later phase when cytokinins also become effective. The relationship between this transition and the apparent gradual reduction in the depth of embryo dormancy during storage is also discussed. The chilling period necessary for dormancy breaking was reduced by kinetin and to a lesser extent by gibberellin, indicating a close relationship between the concentrations of these hormones and the chilling requirement.

Vegetative propagation of freesia through callus cultures.

Abstract: Isolated segments of corm, stem, leaf, flower bud and anther from flowering freesia plants, cv Ballerina, were induced to form callus on a modified Murashige and Skoog medium supplemented with NAA and 6-(benzylamino)-9-(2-tetrahydropyranyl)-9H-purine (PBA) Callus induction was best with young flower buds kept at 25 deg C in darkness Callus could be sub-cultured in darkness on a medium containing auxin and cytokinin Complete plantlets were obtained either by transferring the callus to light on an auxin-free medium containing kinetin or PBA, or from young anthers Adventitious organ formation in explants and callus was closely related to the auxin/cytokinin ratio in the medium, rooting being promoted by auxins and bud formation by cytokinins Root and bud formation were greater in light than in darkness (Abstract retrieved from CAB Abstracts by CABI’s permission)

High Energy Charge as a Requirement for Axis Elongation in Response to Gibberellic Acid and Kinetin during Stratification of Acer saccharum Seeds.

Abstract: The growth potential of embryonic axes of Acer saccharum Marsh. increased during moist storage at 5 C but not at 20 C. During the period of increasing growth potential, the oxygen consumption of the axes remained constant. It was possible to distinguish three phases of the stratification-germination process at 5 C with respect to response of the axis to gibberellic acid and kinetin. From 0 to 10 days the growth regulators had no effect on elongation; from 10 to 60 days axis elongation was stimulated; and between day 60 and day 75, when germination had begun, the growth substances were inhibitory. The adenylate energy charge remained low (0.15) in axes of dry dormant seeds but increased to 0.78 following imbibition of water and 10 days of moist storage at 5 C. This phenomenon was not specifically related to low temperature stratification, since a rapid increase in the energy charge of the axes also occurred following imbibition and moist storage at 20 C. The excised axes would elongate in response to the growth substances only when a high energy charge (approximately 0.8) was maintained.