Showing papers on "Kinetin published in 1973"

Effects of plant growth substances on in vitro fiber development from unfertilized cotton ovules

Abstract: Fertilization of cotton ovules was prevented by removal of styles and stamens on the morning of anthesis. Forty-eight hr later ovaries were harvested and ovules were aseptically transferred to liquid culture medium supplemented with various plant growth substances. In the absence of phytohormones, ovules browned and failed to increase in size or produce fibers. Indoleacetic acid and gibberellic acid provided for ovule growth and fiber development. Kinetin provided for ovule growth only. The ovule's capacity for indoleacetic acidor gibberellic acid-stimulation of fiber development was reduced by high concentrations of kinetin or abscisic acid. Low concentrations of kinetin partially reversed the inhibitory effect of

Induction of pollen plants from anthers of triticum aestivum l. cultured in vitro

Abstract: Anthers of Triticum aestivum L. were cultured in vitro on the MS medium supplemented with auxins, with or without kinetin. Then the pollen grains were successfully, induced to develop into intact plants through a stage of callus formation. Experiments indicated that pollen grains at the mid-uninucleate stage were most favourable for induction to form calli, and that addition of lactalbumin hydrolysate and appropriate increase of the sucrose coneentration had some promoting effects on pollen callus formation. The pollen callus with relatively great differentiating capacity was generally compact in texture and possessed the histological characteristics of the primary meristem. It was noted that the results obtained with different materials (different varieties or hybrids of different crosses) varied considerably. The progeny of the plant induced from F 1, hybrid pollen showed no segregation of characters, suggesting that application of the anther culture method to plant breeding is very promising.

Hormone-induced endoreduplication prior to mitosis in cultured pea root cortex cells'

Abstract: A B S T R A C T One-mm-thick cortical explants excised aseptically from 10-11 mm behind the tip of 3-dayold roots of the garden pea, Pisum sativumn, cv. 'Little Marvel' were cultured on a synthetic nutrient medium supplemented with auxin or auxin and cytokinin. Nuclear DNA contents were measured in cells of the explants at the outset and at specified times during culture up to seven days. Fixed and sectioned preparations were stained with the Feulgen method using the DNA-specific dye auramin-O. Fluorescent microspectro-photometric measurements of individual nuclei were made from each cortical population. At day zero all cortical nuclei measured were either 2c or 4c with respect to their DNA content. In the presence of the auxins, indoleacetic acid and 2,4-dichlorophenoxyacetic acid, and the cytokinin, kinetin, DNA values increased to multiples of the 2c level with populations at the 8c and 16c level predominating after three days of culture as well as at seven days. In the presence of auxins alone no change in DNA values was observed during three days. Kinetin concentrations as low as 0.01 ppm were already effective. The data are interpreted to show that cytokinin, in the presence of auxin, induces two rounds of DNA synthesis prior to the first mitoses, the first round being connected with chromosome doubling by endoreduplication and the second one with normal mitosis. From this we inferred that tetraploid cells in leguminous root nodules might have arisen in the same way, i.e., by endoreduplication prior to the first mitoses induced by the rhizobial division stimulus, unless the chromosome number of root cortical cells had already been doubled by endoreduplication in the normally differentiating root systems.

Mechanism of a Synergistic Effect of Kinetin on Auxin-induced Ethylene Production: Suppression of Auxin Conjugation

Abstract: In hypocotyl segments of mung bean (Phaseolus mungo L.) seedlings, exogenously supplied indoleacetic acid was rapidly conjugated mainly into indoleacetylaspartic acid, which was inactive in inducing ethylene production. Kinetin is known to stimulate indoleacetic acid-induced ethylene production. The mechanism of kinetin action on indoleacetic acid-induced ethylene production by hypocotyl segments of mung bean seedlings was studied in relation to indoleacetic acid uptake and indoleacetic acid metabolism. Kinetin enhanced indoleacetic acid uptake during the initial 2-hour incubation and markedly suppressed the conversion of indoleacetic acid to indoleacetic acid conjugates throughout the whole 7-hour incubation. As a result, there was more free indoleacetic acid and less conjugated indoleacetic acid in the segments treated with kinetin than in those receiving no kinetin. A close relationship was demonstrated between the rate of ethylene production and the level of free indoleacetic acid, which was regulated by kinetin.

Hormonal regulation of growth in unfertilized cotton ovules.

Abstract: Exogenous plant growth regulators can substitute for pollination, fertilization, and subsequent embryo development in cotton. Isolated, unfertilized, immature ovules enlarge in the presence of kinetin, and both enlarge and produce fibers in the presence of indoleacetic acid or gibberellic acid or both. An extract of germinating cotton pollen qualitatively mimics the effect of exogenous hormones.

Ultrastructural aspects of shoot initiation in tobacco callus cultures

Abstract: An ultrastructural investigation of shoot initiation in tobacco (Nicotiana tabacum L. var. W. 38) callus cultures was made. Zones of preferential division were observed in the basal portion of the tissue by eight days in culture and these led, sequentially, to meristemoids, primordia, and shoots. During the initial stages of meristemoid formation, protein inclusions and large accumulations of plastid starch were present in the cells, while vacuoles were filled with membranous and cytoplasmic protrusions. At later stages of meristemoid development, these features were not observed in the cells, which were also smaller in size and possessed numerous small, peripheral vacuoles. It appears that the membranous and cytoplasmic protrusions are involved in vacuolar reduction during meristemoid formation. It would also appear that the storage materials supply the energy and other reserves needed for the organogenetic process. By contrast, tissue cultured under nonshoot-forming conditions and nonmeristemoid regions of shoot-forming tissue remained parenchymatous over the same time period. ZONES OF preferential cell division occur in the parenchymatous tissue of callus cultures of tobacco by day 8 (Thorpe and Murashige, 1970). Meristemoids arise from these areas, although not all areas of preferential cell division give rise to these structures. Meristemoids (Torrey, 1966) are the meristem-like aggregations of small, nonpolar cells which appear to be nonvacuolate at the light microscope level and from which primordia and ultimately leafy vegetative shoots are formed (Murashige, 1964; Thorpe and Murashige, 1970). The mechanism of meristemoid formation in tissue cultured under organ-forming conditions is not yet known, although it has been suggested that these could arise from single cells (Torrey, 1966). Associated with meristemoid development is a rapid increase and decrease in the amount of stored starch in tobacco callus (Thorpe and Murashige, 1968, 1970). This starch may serve as a source of energy for shoot formation which, judging by the respiratory activity of the tissue (Thorpe and Meier, 1972; Ross and Thorpe, 1973), has a high energy requirement. In this study, ultrastructural changes during meristemoid formation and shoot initiation were investigated. MATERIALS AND METHODS-Tobacco (Nicotiana tabacum L. var. 'Wisconsin 38') callus was isolated from stem pith segments and maintained on three-quarter strength Murashige-Skoog (MS) 1 Received for publication 27 November 1972. Supported by NRC of Canada grant no. A-6467 to T.A.T. medium (Murashige and Skoog, 1962). For shoot production, the tissue was grown on the modified MS medium reported earlier (Thorpe and Murashige, 1970) except that the concentrations of Ltyrosine, adenine sulphate, and NaH2PO4 H20 were reduced by half. The medium contained indole-3-acetic acid and kinetin in final concentrations of 10-5M. Cultures were maintained in darkness in 125-ml Erlenmeyer culture vessels containing 50 ml of medium. Sections of tobacco callus, each measuring ca. 3 x 3 x 2 mm, were used as inoculum. Thin sections, cut by hand, parallel to the surface in contact with the medium were irrigated with fixative (2/2 % glutaraldehyde) and scanned under a binocular microscope. Areas of preferential division, with prominent nuclei, and areas of shoot initiation were excised and prepared for electron microscopy. Each piece of tissue was ca. 1 mm3. Tissue was sampled from 8-, 10-, 12-, and 14-day-old shoot-forming tissue and from 8-, and 14-day-old nonshoot-forming tissue. Freehand monitor sections were also stained with iodinepotassium iodide (Jensen, 1962). Heavy blueblack staining for starch occurred in the regions visually determined as areas of preferential cell division or meristemoids (Thorpe and Murashige, 1968). The tissue samples were prefixed in 21?% glutaraldehyde in 0.1 M phosphate buffer, pH 6.8 -+ 0.5 for 4 hr. Following buffer washes, the material was fixed in 1 % unbuffered Os04 for 50 min. The tissue was then dehydrated in an ethanolic series after a further buffer wash and embedded in ERL-4206 (Spurr, 1969). Staining was

An improved bio‐assay for abscisic acid and other antitranspirants

Abstract: SUMMARY A greatly improved method is described for the bio-assay of abscisic acid (ABA) and other compounds that possess ‘antitranspirant’ activity. As in the previous method, the stomatal responses are observed on pieces of isolated epidermis of Commelina communis immersed in small volumes of solution containing the compounds to be assayed. In new media, it is now possible to obtain linear responses to ABA concentrations over the range 10-4-10-8 M in PIPES buffer at pH 6.8, and over the range 10-7-10-10 M in citrate buffer at pH 5.5. In citrate buffer, it is possible to detect as little as 26 pg of ABA. In both media, the assay is unaffected by the presence of six other growth regulators (auxin, gibberellic acid, kinetin, coumarin, xanthinin and scopoletin) but the stomata closed partially in response to 10-3 M chlorogenic acid.

Hormonal Control of Differentiation of Shoots, Roots and Embryos in Leaf and Stem Cultures of Petunia inflata and Petunia hybrida

Abstract: Factors influencing adventitious bud and root development, callus induction and embryogenesis were investigated in stem and leaf cultures of Petunia inflata R. E. Fries and Petunia hybrida cv. Cascade and cv. Rose du ciel grown on a synthetic nutrient medium. Indoleacetic acid caused limited callus development and root formation whereas naphthaleneacetic acid Induced abundant roots. 2,4-Dichlorophenoxyacetic acid promoted callus growth and differentiation of embryos which eventually developed into plantlets. Cytokinins such as benzyladenine, zeatin and kinetin induced bud development. A combination of auxins and cytokinins caused an interaction which was manifested in altered morphogenetic response. Thus 2,4-dichlorophenoxyacetic acid in conjunction with benzyladenine caused suppression of bud development and retarded differentiation of embryos. Likewise, when benzyladenine was used with indoleacetic acid root development was totally inhibited and abundant buds were produced.

Identification of a Cytokinin, 6‐(3 Methyl‐2‐butenylamino) purine, in Sea Water and the Effect of Cytokinins on Brown Algae

Abstract: Using combined gas chromatography and mass spectrometry a growth-promoting, organic component of sea water has been quantitatively estimated and identified as the cytokinin 6-(3 methyl-2-butenylamino) purine. Additions of this cytokinin, kinetin or sea water from the Fucus-Ascophyllum zone increased the growth of Ectocarpus confervoides and Pylaiella litoralis in artificial sea water. Additions of kinetin to bacteria-free cultures of Ectocarpus fasciculatus also initiated the production of upright ectocarpoid filaments.

Callus formation from mesophyll protoplasts of Pisum sativum

Abstract: Protoplasts isolated from mesophyll of Pisum sativum L. cv. Century, and cultured in 0.2-ml droplets of B5 medium with 1.0 mg/liter (2,4-dichlorophenoxy)acetic acid (2,4-D) or 1-naphthaleneacetic acid (NAA) and 2.0 mg/liter kinetin regenerated cell walls within 2–3 days. The resulting cells began to divide and form calli after 19 days of culture. Protoplast survival depended on keeping the leaf material in the dark for at least 30 h before use.

Growth requirements and development of Cypripedium reginae in axenic culture

Abstract: In preliminary studies of terrestrial orchids of the Thunder Bay region Cypripedium reginae showed greatest promise as a species for the investigation of the effects of temperature, light, and nutrients. The orchid was grown from seed in sterile cultures on agar slopes of media consisting of various combinations of minerals, sugars, casein hydrolysate, yeast extract, potato extract, the vitamins thiamine, pantothenic acid, and pyridoxine, and the aminopurines kinetin, kinetin riboside, 6(γ,γ-dimethylallylamino)purine, and zeatin.Better germination and growth occurred at 25 °C vs. 15 °C. Germination was better in the dark than in the light. The young protocorms are adversely affected by light until a crucial stage of development is reached. Premature exposure to light, even at the low intensity of 70 lm/ft2, caused mortality.There was no germination on sterile-distilled-water agar or on mineral media alone. Mineral–sugar media produced fairly healthy plantlets; better results were obtained with sucrose, de...

Effects of Kinetin, Gibberellins and (±) Abscisic acid on the Germination of Lettuce (Lactuca sativa)

Abstract: Germination responses of achenes of lettuce (Lactuca sativa L, cv. Arctic King) to treatment with kinetin, gibbe-rellins and abscisic acid were examined over a range of temperatures: in both light and dark. Kinetin (0.1–10 mg/l) strongly promoted germination at temperatures above 27±C in continuous light or after short periods of illumination during the early stages of imbibition. It also relieved the inhibitory affects of abscisic acid in these conditions. In total darkness however kinetin treatment resulted in only a minor promotive effect. Treatment with gibberellic acid (A3) or a mixture of gibberellins A4 and A7 were much less effective in promoting germination at higher temperatures of lettuce achenes exposed to light but were strongly promotive in the dark.

Cytokinin‐induced Pseudonodules on Alnus glutinosa

Abstract: Alder root nodules are capable of atmospheric nitrogen fixation. A differential treatment with kinetin and 2IP (2-isopentenyl adenine) was applied to the rooting medium of alder plants growing in test tubes containing Crone solution. The experiment led to the formation of a fair number of pseudonodules scattered on the root system of the plants treated with cytokinin levels higher than 0.6 μg/ml. Kinetin had a lowering effect on the overall growth of the plant, whereas the plants treated with 2IP showed no differences in growth as compared to the non-treated control plants. Histological sections of the pseudonodules show an unorganized tissue originating from the parental root cortex, and the presence of groups of tracheids giving the aspect of unorganized vascular bundles.

Further studies on the photosynthesis of carrot tissue cultures.

Abstract: The influence of kinetin and sucrose on the photosynthetic activity of carrot (Daucus carota) tissue cultures in relation to growth was investigated. The results showed that light contributes heavily to the growth of tissue cultures measured in terms of fresh and dry weight and cell division activity. In light, the fresh weight, dry weight, and number of cells per explant were about or more than doubled. This indicated that after the development of chloroplasts, carrot tissue cultures can grow autotrophically at least as far as energy and carbon are concerned. Kinetin was shown to have an important role in developing the photosynthetic apparatus and photosynthetic activity of tissue cultures as manifested by the increase of chlorophyll content (60%), Hill activity (about 3-fold), and 14C-fixation from NaH14CO3 (about 20%). On the other hand, the presence of sucrose in the medium reduced the chlorophyll content by about 30% and 14C-fixation from NaH14CO3 in the soluble fraction by about 60%. A possible correlation between the influence of kinetin on sugar uptake and the effect of kinetin on 14C-fixation from NaH14CO3 was discussed.

The development of haploid embryoids from anther cultures of Atropa belladonna L

Abstract: Development of haploid embryoids from the microspores of Atropa belladonna occurs with relatively high frequency when anthers are excised from buds in which the petals are shorter than the sepals (at this stage microspores are predominantly uninucleate) and cultured on a medium containing iron as the ferric salt of ethylenediamine-di-O-hydroxyphenylacetic acid (FeEDDHA). Additions of combinations of kinetin, auxin and casamino-acids to the culture medium induce callusing in both haploid and diploid tissues, lead to the origin of embryoids from somatic tissues of the anther and should be avoided. Simple techniques for the maintenance of haploid clones are described.

Effects of different cytokinins on the senescence of detached oat leaves.

Abstract: Senescence is delayed (chlorophyll retained) in oat leaf sections by kinetin and benzyladenine, but not by the natural cytokinins, zeatin and isopentenyladenine.

Hormonal control of isoperoxidases in lentil embryonic axis.

Abstract: Detachment of the cotyledons from the lentil (Lens culinaris Med.) embryonic axis causes in the latter an increase in total peroxidase activity which is shown to be due to enhancement of specific cathodic isoperoxidases. Kinetin treatment of attached or detached axes promotes activity of essentially the same cathodic isoperoxidases. In addition kinetin enhances the activity of two anodic peroxidases and represses specifically that of a cathodic one. Abscisic acid inhibits the production of all isoenzymes in the presence or absence of kinetin. Cytokinin and abscisic acid actions are discussed in relation to the nature of a wounding hormone and the role of natural inhibitors in cotyledons during germination. Indoleacetic acid stimulates the activity of certain isoenzymes which are also stimulated by kinetin, whereas in others the effects of the two hormones are different. Specific inverse effects of indoleacetic acid and kinetin are demonstrated on the two most cathodic isoperoxidases. Indoleacetic acid-kinetin interactions on the cathodic isoperoxidases have been found in the literature and are discussed as a possible mechanism for explaining interactions of the two regulators on growth and other physiological processes.

Effects of Kinetin on the Permeability of Allium cepa Cells

Abstract: Permeability changes of Allium cepa cells were studied by a plasmometric method. Onion epidermis was floated in phosphate buffer solution with kinetin (2.5 milligrams/liter), or buffer without kinetin as a control, for 10 hours. The treated and control tissues were then transferred to one of the following four permeants: thiourea, urea, maloamide, dimethylurea. Kinetin treatment increased the permeability of onion epidermal cells to thiourea and urea. The kinetin effect on permeability to malonamide and dimethylurea was not significant. It is suggested that kinetin might affect the protein component of the cell membrane.

The Inhibition by Cytokinin of Auxin‐Promoted Elongation in Excised Soybean Hypocotyl

Abstract: The experiments characterize the inhibition by kinetin of auxin-promoted elongation in excised hypocotyl sections of 3-day soybean seedlings (Glycine max cv. Hawkeye 63). It was found that concentrations of kinetin above 4.2 μM did not further inhibit auxin-promoted elongation. Kinetin is as potent an inhibitor of elongation as actinomycin D or cycloheximide. Tissue incubated for 3 or 5 h in the absence of auxin or cytokinin would, upon addition of auxin, exhibit a new growth rate similar to that of tissue grown in auxin for the entire incubation period. Similarly, tissue grown for 3 and 5 h in the presence of auxin would revert to the control rate of elongation upon addition of kinetin. A 10 to 30 min preincubation in kinetin yielded the tissue incapable, for the ensuing 6 h, of increasing its rate of elongation in response to auxin. Zeatin and isopentenyladenine were more potent than kinetin and benzyladenine in the inhibition of elongation. Levels of ethylene produced in the presence of auxin plus cytokinin indicated that it was not involved in this auxin-cytokinin interaction. Kinetin by itself did not promote elongation; nor did it enhance auxin-promoted elongation at low auxin concentrations.

Leaf water content and hormone effects on ribonuclease activity.

Abstract: In barley (Hordeum vulgare) leaves in which the water balance was not hampered, kinetin and abscisic acid effected the well documented decrease and increase, respectively, in RNase activity. When the plants were exposed to water shortage, leaf-water saturation deficit increased steadily, with kinetin enhancing and abscisic acid retarding the rise. Under drought, the pattern of hormonal effects was inverted, with kinetin enhancing RNase activity over and above the activity assayed in abscisic acid-treated leaves. A very close relationship between RNase activity and water saturation deficit was found and significantly, it was maintained irrespective of the hormonal treatment, which in itself markedly modified leaf-water saturation deficit. The inverted effects of kinetin and of abscisic acid on RNase activity under conditions of water shortage were interpreted as resulting primarily from the effects of these hormones on leaf-water. It is suggested that under conditions of increased water deficiency in the plant, cell-water supersedes hormonal regulation in effecting RNase activity.