Absence Of Kinetin Research Articles

Salicylic acid in combination with kinetin or calcium ameliorates heavy metal stress in Phaseolus vulgaris plant

It has been well documented that phytohormones plays a pivotal role in combating ill effects of various abiotic stresses in crop plants. Out of various phytohormones, worldwide researcher has recognized salicylic acid as potent stress alleviator through modulation in plant metabolic processes. Therefore, present study was designed with an aim to dissect out the role of salicylic acid (through seed) mediated amelioration of heavy metal stress in the presence and absence of kinetin or calcium in Phaseolus vulgaris plants. Seeds were soaked in salicylic acid (0.1 mM) either alone or in combination with kinetin (30 ppm) or calcium chloride (40 mM) before sowing and then seedlings were exposed to toxic concentration of nickel (2.5 mM) and lead (0.5 mM). Salicylic acid alone and in combination with kinetin or calcium improved growth traits, photosynthetic pigment, carbohydrate contents, and nitrogenous constituents along with activities of carbonic anhydrase, nitrate reductase, catalase, peroxidase, and superoxide dismutase of Phaseolus vulgaris plants. However, nickel and/or lead showed oxidative damage through increased electrolyte leakage, malondialdehyde and reduced uptake of mineral ions. Moreover, plants raised from seeds soaked in salicylic acid in combination with kinetin or calcium showed enhanced activities of antioxidant enzymes and proline accumulation under nickel and/or lead stress in Phaseolus vulgaris plants. This study revealed the efficiency of pre-sowing seed soaked in salicylic acid either alone or in alternate combination with kinetin and calcium on neutralizing the toxic effect generated from nickel and/or lead in Phaseolus vulgaris plants and could be employed as sustainable agricultural technique in removal of nickel and lead stresses from plants.

Propagación y conservación in vitro de siete especies de cactáceas del noreste del estado de Guanajuato

Se desarrollaron protocolos para la propagación in vitro de siete especies de cactus presentes en municipios del noreste del estado de Guanajuato: Mammillaria geminispina, M. magnimamm, M. marcosii, M. mercadensi, M. petterssonii, Coryphanta radians y Ferocactus latispinus. Se observó que la presencia en el medio de cultivo de la citocinina cinetina es esencial para la multiplicación de seis de las especies, ya que las máximas respuestas se presentaron en las mayores concentraciones de citocinina, 6 mg/l y 10 mg/l de ese regulador de crecimiento, siendo notorio que tres especies de Mammillaria: M. geminispina, M. magnimamma y M. marcosii indujeron sus respuestas en las máximas concentraciones de los dos reguladores de crecimiento empleados, ácido indolacético (AIA) = 4 mg/l y cinetina 10 mg/l con promedios de 6.0, 6.0 y 9.2 brotes por explante. respectivamente. Sin embargo, se presentó una excepción, y ésta fue la respuesta de Ferocactus latispinus, la cual en presencia de AIA = 4 mg/l y en ausencia de cinetina indujo 4.8 brotes por explante, mostrando la variabilidad en respuestas a los reguladores de crecimiento en especies diferentes de la familia Cactaceae.

Development of new plants from leaves and roots of Atropa belladonna L. in the in vitro culture

Isolated leaves, leaf fragments and fragmented roots of <i>Atropa balladanna</i> were grown in vitro in order to study their morphogenetic potentials. In the presence of 'kinetin and IAA, a great number of shoot buds arose from the leaves and roots. In those cases when cut leaves were implanted a callus arose from the leaves which subsequently gave rise to many buds. In the absence of kinetin and IAA buds were not formed. In the presence of IAA only numerous roots arose from the cut ends of the leafe stalk and from .the fragmented root.

Synergistic effect of morphactin on cytokinin-induced production of isoflavonoids in cell cultures of Pueraria tuberosa (Roxb. ex. Willd.) DC

Isoflavonoids, the functional molecules of Fabaceae, are under clinical trials against cancer, osteoporosis and cardiovascular diseases. In this study, the efficacy of different plant growth regulators was evaluated for optimizing the production of isoflavonoids in Pueraria tuberosa. The cultures were maintained in Murashige and Skoog’s medium containing 0.1 mg l−1 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) and 0.1 mg l−1 kinetin. The addition of 5.0 mg l−1 N6-(2-Isopentenyl) adenine (2iP) resulted in about ∼32-folds increase in production of isoflavonoids, while about ∼23-folds increase was recorded in the absence of kinetin in the maintenance medium. A maximum yield of isoflavonoids (∼80 mg l−1; 82-folds increase) was obtained in cultures grown at 0.1 mg l−1 morphactin and 5.0 mg l−1 of 2iP. However, 2,4,5-T in combination with 2iP was ineffective for their production. Among different plant growth regulators tested, maximum yields of puerarin, genistin, daidzein and genistein were 17.4, 15.9, 69.0 and 0.04 mg l−1, respectively. The study suggested that the presence of two cytokinins or 2iP with morphactin in the culture medium markedly enhanced the production of isoflavonoids in P. tuberosa.

Influence of Arbuscular Mycorrhizal Fungus and Kinetin on the Response of Mungbean Plants to Irrigation by Seawater

An experiment was carried out to investigate the effects of pre-inoculation with the mycorrhizal fungus Glomus clarum and foliar application of kinetin on the growth of mungbean plant irrigated wht different dilutions of seawater. Arbuscular-mycorrhizal (AM) infection significantly increased dry weight, height, chlorophyll, sugar and protein content, nitrogen and phosphorus-use efficiencies, leaf conductivity, transpiration rate, nitrogenase, acid and alkaline phosphates activities of all salinized mungbean plants in comparison with control and non-mycorrhizal plants irrespective of the presence or absence of kinetin. Mycorrrhizal plants showed higher concentrations of N, P, K, Ca and Mg and lower Na/N, Na/P, Na/K, Na/Ca and Na/ Mg ratios than non-mycorrhizal plants when irrigated with certain dilutions of seawater Mungbean plants showed 597% and 770% dependency on AM fungus G. clarum in absence and presence of kinetin, respectively, for biomass production under a level of 30% of seawater. The average value of tolerance index for mycorrhizal plants accounted 267% and 364% in absence and presence kinetin respectively. This study provides evidence for the benefits of kinetin which are actually known for mycorrhizal than non-mycorrhzal plants. AM fungus and kinetin protected the host plants against the detrimental effects of salt. However, mycorrhizal infection was much more effective than kinetin applications. Thus management applications of this arbuscular mycorrhizal endophyte (G. clarum) with kinetin could be of importance in using seawater in certain dilutions for irrigation in agriculture.

Callus and cell suspension cultures of Rudgea jasminoides, a tropical woody Rubiaceae

Rudgea jasminoides is a woody Rubiaceae that produces phytoalexins in response to fungal inoculation, the response being dependent of the seasonal conditions. With the aim of studying phytoalexin induction under controlled conditions, callus cultures were established from petiole explants of R. jasminoides on a modified basal MS medium supplemented with picloram alone or in combination with kinetin. The highest frequency of callus formation was observed in solid medium containing 2.22 μM kinetin and 2.07 μM picloram. Development of fast-growing friable white callus was achieved in the absence of kinetin, in cultures supplemented only with 8.28 μM picloram. Cell suspension cultures were established from this friable callus by transferring pieces directly to the same medium without agar. Preliminary experiments revealed that cell suspension cultures of R. jasminoides represent a useful system to analyse induced defensive metabolites produced by this Rubiaceae species.

Leaf senescence under various gravity conditions: relevance to the dynamics of plant hormones.

Effects of simulated microgravity and hypergravity on the senescence of oat leaf segments excised from the primary leaves of 8-d-old green seedlings were studied using a 3-dimensional (D) clinostat as a simulator of weightlessness and a centrifuge, respectively. During the incubation with water under 1-g conditions at 25 degrees C in the dark, the loss of chlorophyll of the segments was found dramatically immediately after leaf excision, and leaf color completely turned to yellow after 3-d to 4-d incubation. In this case kinetin (10 micromolar) was effective in retarding senescence. The application of simulated microgravity conditions on a 3-D clinostat enhanced chlorophyll loss in the presence or absence of kinetin. The loss of chlorophyll was also enhanced by hypergravity conditions (ca. 8 to 16 g), but the effect was smaller than that of simulated microgravity conditions on the clinostat. Jasmonates (JAs) and abscisic acid (ABA) promoted senescence under simulated microgravity conditions on the clinostat as well as under 1-g conditions. After 2-d incubation with water or 5-d incubation with kinetin, the endogenous levels of JAs and ABA of the segments kept under simulated microgravity conditions on the clinostat remained higher than those kept under 1-g conditions. These findings suggest that physiological processes of leaf senescence and the dynamics of endogenous plant hormone levels are substantially affected by gravity.

The Effects of Different Concentrations of Gibberellic Acid (GA3) and Kinetin on in Vitro Tuberization of Potato (Solanum tuberosum L.)

To determine the influence of gibberellic acid (GA3) and 6-furfuryl aminopurine (kinetin) concentrations alone and in combinations on in vitro tuberization of potato, nine treatments consisting of combinations of gibberellic acid and kinetin at three levels of concentration (0, 2, and 5 mg·liter–1) were included in Murashige and Skoog medium supplemented with 6% sucrose. Four single nodes of in vitro plantlets from Solanum tuberosum L. cultivar Atlantic were placed into each magenta box. All magenta boxes were arranged in a randomized complete box design with five replications and cultured under a short photoperiod condition (8 h light/16 h dark). Gibberellic acid strongly inhibited tuberization when used alone or with kinetin, whereas kinetin induced tuberization at both 2 and 5 mg·liter–1. Although tuberization was initiated in the absence of kinetin because of the high concentration of sucrose and short photoperiod, the presence of kinetin accelerated the in vitro tuberization process of potato.

Rapid changes in amplification and methylation pattern of genomic DNA in cultured carrot root explants (Daucus carota L.)

Rapid genomic DNA variation due to methylation and copy number alteration was observed in carrot root explants 6 h after inoculation and during a 36-h period of exponential callus growth. De novo methylation and amplification of restricted BspNI fragments of low molecular weight occurred before cell cycle activation and should, therefore, be independent of progression through the S-phase of the cell cycle. Growth regulators seemed to influence the amplification pattern indirectly by regulating cell division activity. In exponentially growing callus tissue the copy number of most of the repetitive fragments was dramatically reduced. It is presumed that this reduction in the copy number of repetitive fragments is characteristic of 'rejuvenilization'. 3-Indole-acetic-acid (IAA) and inositol in the medium increased the degree of unspecific genomic DNA methylation in growing rhizogenic carrot callus tissue in the absence of kinetin, which inhibits root induction at that stage. A possible relation to the induction of rhizogenesis is considered. The observed reduction in number of repetitive restriction fragments and the increase in DNA methylation are gross changes covering the total genome. The results are discussed in relation to the controversy concerning the general biological significance of the methylation and amplification of DNA sequences.

Stimulation of soybean callus growth by S-Lathyrine

S-Lathyrine stimulated growth of soybean callus tissue by cell division in the presence or absence of kinetin. It was also active in the radish leaf senescence test, but was inactive in the tobacco callus assay and in five other tests for cytokinins.

Role of Cytokinins in Development and Metabolism of Barley Leaves. VII. Effect of Light and Kinetin on the Transcriptional Activity of Nuclei from Etiolated Leaves

Summary Leaves excised from etiolated seedlings of Hordeum vulgare L. cv. Triumph were exposed to light for 6 h in the presence or absence of kinetin at 5 µM. Nuclei were isolated and their activity in [ 14 C]-UTP incorporation into an acid insoluble product was determined. This activity increased after exposition of leaves to light (in comparison with the zero-time dark control) due to transcription catalyzed by both RNA polymerases I and II. The response to kinetin depended on the physiological age of leaves. In younger (usually 8-day-old) leaves, kinetin promoted the rate of transcription mainly connected with RNA polymerase I. In somewhat older (about 10-d-old) leaves, kinetin inhibited the transcription, mainly at the expense of activity connected with RNA polymerase II.

Role of Cytokinin in Differentiation of Secondary Xylem Fibers

The differentiation of secondary xylem fibers was studied in cultured hypocotyl segments of Helianthus annuus L. It is shown that cytokinin is both a limiting and controlling factor in the early stages of fiber differentiation. In the absence of kinetin or zeatin, there was no fiber differentiation. However, cytokinin could induce fiber differentiation only in the presence of indoleacetic and gibberellic acids. First fibers were observed in the tissue after 12 days in culture, and their number increased linearly during the following 2 weeks. At low cytokinin levels, there was a positive correlation between cytokinin concentration in the medium and the number of fibers formed in the explants. A similar correlation was also found at low gibberellic acid concentrations. At high concentration, zeatin was more effective than kinetin. It seems that later stages of fiber differentiation can occur in the absence of cytokinin. It is proposed that the mechanism which controls and determines the early stages of fiber differentiation is based on an interaction of three major hormonal signals: indoleacetic acid plus gibberellic acid from the leaves with zeatin from the root apices.

Inhibition of cytokinin‐induced plant growth by jasmonic acid and its methyl ester

Effects of jasmonic acid, methyl jasmonate and ABA on cytokinin‐induced soybean (Glycine max Merrill cv. Kingen No. 1) callus growth and radish (Raphanus sativus L. cv. Comet) cotyledon growth were studied. Jasmonic acid and methyl jasmonate were powerful inhibitors of kinetin‐ or N‐phenyl‐N′‐(2‐chloro‐4‐pyridyl)urea‐induced soybean callus growth, the former being more effective than the latter, especially at low concentrations (0.45 to 4.5 μM). These compounds could completely eliminate kinetin‐ or N‐phenyl‐N′‐(2‐chloro‐4‐pyridyl)urea‐induced soybean callus growth at 45 μM. At low concentrations ABA had no effect but at 450 μM it completely eliminated callus growth induced by kinetin. Of the compounds tested ABA was the most powerful inhibitor of radish cotyledon growth in the presence or absence of kinetin. Jasmonic acid and methyl jasmonate were much less effective than ABA in this assay system.

ACTION OF GROWTH REGULATORS ON LUCERNE GERMINATION AND GROWTH UNDER WATER STRESS

SummaryLucerne seeds (Medicago sativa L.) were germinated in a range of polyethylene glycol (PEG) and sodium chloride (NaCl) solutions in the presence and absence of kinetin with ethrel. In addition, seeds were germinated in water and transferred to PEG and NaCl solutions, and root growth was measured. The water potentials at which there was 50% germination inhibition and at which 50 % of the germinated seeds failed to grow after transfer were determined. Kinetin and ethrel together completely removed the block to germination through osmotic stress, allowing germination to proceed at the same water potential as growth. The action of kinetin and ethrel was studied by following the processes of cell expansion and division during germination and early growth. The control of germination by water stress was through cell expansion, and the initiation of this process was shown to be stimulated in the presence of the growth regulators. Cell division although initially permitted in their presence, was later inhibited causing a decline and finally cessation of seedling growth.

Biochemical and Cytological Analyses of RNA Synthesis in Kinetin-treated Pea Root Parenchyma

Excised cortical parenchyma from the pea root (cv. Little Marvel) responds to kinetin/auxin treatment with an increased rate of RNA synthesis well before reinitiating DNA synthesis. Few cells synthesize RNA in the 1st hour of culture. In the presence of kinetin/auxin, the nuclear labeling index increases 2.5-fold as compared to control cultures. The RNA synthesis response has an apparent lag period of 2-4 hours as shown by double label ([(3)H]adenosine/[(14)C]adenosine) experiments. Qualitatively, the RNA synthesized at 4-6 hours sediments between 18S and 5S. The RNA synthesized at 14-16 hours and 24-26 hours is primarily ribosomal RNA when kinetin is present. In the absence of kinetin, no clear pattern of RNA synthesis emerges.The data are interpreted to mean that kinetin treatment elicits RNA synthesis in a small proportion of the population initially and this may involve messenger-like RNA. Later, more cells synthesize RNA and this is primarily rRNA.

Kinetin counteracts the myomycin-inhibitory effect on plastid differentiation in excised cucumber cotyledons

Summary The possibility of a specific action of kinetin(KN) on plastidial biosynthetic events was considered by verifying the ability of this phytohormone to contrast the inhibitory effect exerted on plastid differentiation by the antibiotic myomycin (MM), a specific plastid protein synthesis inhibitor. The experiments were carried out on etiolated cotyledons of cucumber (Cucumis sativus L.) incubated for 20 h in the dark followed by 24 h in the light in the presence or absence of KN (100μM), or MM (200,μg/ml) or the two combined substances. In the presence of MM, chlorophyll synthesis and etioplast to chloroplast transformation were strongly inhibited while in the presence of KN they both were markedly enhanced. Importantly, when KN was applied simultaneously with MM, the inhibitory influence of the antibiotic was distinctly counteracted or completely nullified by the hormone. The fact that KN dominates the MM-inhibitory effect indicates that the action of the two molecules may be localized at similar cellular levels. Since MM exerts its activity by stably interacting with 70 S ribosomes of the chloroplast, it is suggested that KN could also act specifically at the same level.

Biochemical Requirements for Seed Germination and Shoot Development of Witchweed(Striga asiatica)

Germination of witchweed [Striga asiatica(L.) Kuntze] seeds was induced by treating air-dry seeds with kinetin (6-furfuryl-aminopurine) at 1.16 × 10−4M and 2.32 × 10−4M without subjecting the seeds to the conventional preconditioning procedures. Rudimentary shoot development of the seedlings also was promoted. Tissue culture techniques were used also to study growth regulator and nutritional requirements for witchweed seedling development. Seedlings with normal leaves and stems were obtained under aseptic conditions in synthetic media at pH 5.4 in the absence of a host plant when cultured in the presence of kinetin, indole-3-acetic acid (IAA), sucrose, casein hydrolysate and mineral salts. No shoot development occurred in the absence of kinetin or zeatin [6-(trans-4-hydroxy-3-methylbut-2-enylamino)purine]. Shoot development was more advanced if IAA or gibberellic acid (GA3) was used in combination with the cytokinins. Witchweed seedlings are dependent on a host plant not only for their nutrition, but also for plant hormones such as a cytokinin required for the promotion of shoot development.

Thiourea, a Growth Promoter of Callus Tissues1

Thiourea (TU) promoted growth in cytokinin-requiring soybean, tobacco, and apple callus tissues, in the absence of kinetin. The increase in fresh and dry weight obtained was a result of cell multiplication. Callus tissues grew well when repeatedly subcultured in kinetin-free medium containing TU. The best growth was obtained with 10−4-10−3 M TU. At these concentrations synergism was demonstrated between TU and the cytokinins, kinetin, benzyladenine, and zeatin. TU caused greater growth than diphenylurea and phenylthiourea. The possibility that a breakdown product of TU is responsible for the enhanced growth was not excluded. The dormancy-breaking effect of TU was suggested to be related to its growth-enhancing effect.

Biochemical Responses of Pea Root Tissue to Cytokinin

Rates of RNA synthesis were studied in cultured pea (Pisum sativum) root segments and cortical explants which require the hormone cytokinin for DNA replication and cell proliferation. Rate calculations were based on the specific radioactivity of the extracted RNA and the specific radioactivity of the extracted ATP pool after a pulse with (3)H-adenosine. The kinetics of RNA synthesis was studied after 24 hours of culture with or without kinetin. We found that kinetin stimulated a 2- to 4-fold enhancement in the rate of RNA synthesis after 24 hours of culture as compared to controls. A similar order of magnitude of stimulation of RNA synthesis was found when RNA was isolated by cesium chloride centrifugation. Pulses during the first 24 hours indicate that kinetin stimulates the rate of RNA synthesis as early as 9 hours after treatment has begun. During the first 24 hours of culture, kinetin did not affect the specific radioactivity of the ATP pool. The ATP pool equilibrated slowly with the exogenous label ((3)H-adenosine) in the presence or absence of kinetin. After 3 days in culture, we found kinetin to cause an expansion of the extractable ATP pool and a corresponding reduction in the ATP pool specific radioactivity. We interpret these results to indicate a stimulation in the rate of RNA synthesis due to kinetin treatment prior to any other known response.

18 ?m replication units of chromosomal DNA fibers of differentiated cells of Pea (Pisum sativum)

Explants of stelar and cortical mature pea root tissues were cultured on solid agar synthetic medium for up to 6 d. On the 3rd and 6th day the tissue was pulsed with 3H-thymidine from 15 up to 180 min to label the DNA. Subsequently the nuclei were isolated, lysed, and the DNA spread on microscope slides. The autoradiograms of labeled DNA fibers showed that the average replication fork traveled at 9 μm/h, and that an average of 18 μm of DNA separated activated origins. Nearly identical parameters were obtained from DNA of all callus independent of tissue source and independent of the presence or absence of kinetin in the medium.