Effect Of Liquid Media Research Articles

Temporary immersion bioreactor as an efficient method for in vitro propagation of Agave marmorata

Agave marmorata is an important wild species in Mexico for mezcal and pulque production. Propagation by suckers and seeds is not sufficient to restore wild populations. The aim of this study was to develop a protocol for large-scale micropropagation of A. marmorata using a temporary immersion bioreactor (TIB). The effect of liquid medium using a TIB and semi-solid medium as the control treatment was compared. Different immersion frequencies and culture medium volumes per explant were evaluated in the TIB. In all treatments, the percentage of hyperhydricity, number of shoots per explant, shoot length, and total chlorophyll and carotenoid content were evaluated. In addition, the survival rate during acclimatization was evaluated. The results obtained show that the TIB with an immersion of 2 min every 8 h and with a culture medium volume of 50 mL had the best developmental parameters, with 19.60 shoots per explant, a shoot length of 1.74 cm and a percentage of hyperhydricity of 3.33 %. The highest chlorophyll content was observed in temporary immersion every 8 h, with 100, 75 and 50 mL of culture medium per explant. Regarding carotenoid content, the highest content was found at the 8 and 12 h immersion frequencies, with the culture medium volumes of 100, 75 and 50 mL per explant. For acclimatization, no differences were found in the survival rate between the culture systems evaluated. In conclusion, this study demonstrates that the use of a TIB is an alternative for large-scale micropropagation of A. marmorata.

The impact of nitrogen-containing compounds on the S-vacancies over the iron-based catalysts for direct coal liquefaction during the pre-sulfurization process

To advance the direct coal liquefaction (DCL) technology by a “Catalytic cycle of hydrogen donor solvents” pathway, it wasimportantfor the iron-based DCL catalyst to be pre-sulfurized under a suitable condition. In this report, the effect of liquid medium in the slurry bed pre-sulfurization process on iron-based catalyst was studied. Catalysts were pre-sulfurized under a variety of liquid mediums including alkanes, aromatics and heteroatom-containing compounds and the activity were evaluated according to their performance on hydrogenation of naphthalene. It was observed that, the nitrogen-containing medium give rise to the significant negative influence on the catalytic activity (with only 2.5 %-15.3 % of naphthalene conversions). Multiple spectroscopic and microscopic analyses of catalysts exhibited that the decrease of S vacancies was mainly responsible for the low activity. It was due to the promotion effect on Fe1-xS crystallization and troilite generation. S vacancies of the iron-based catalysts was considered as Lewis acid sites to catalyze the hydrogenation reaction. The new findings from this work is beneficial for the development and optimization of pre-sulfurization technology.

Passive Downward Heat Transfer in Reverse Thermosyphon Enabled Bubble Pump with Two Working Media for U-Tube Solar Thermal Collector

The study is aimed to evaluate the impact of multi-phase nanofluid flow to enhance heat transfer. The effect of liquid medium and pumping medium together with enabling a bubble pump to reverse thermosyphon arranged as an extension of the U-tube of solar thermal collector could affect a passive downward heat transfer numerically. The liquid and pumping medium selection were based on different nanofluid and phase change material accomplishment with respect to their optimal concentrations, optimal geometry of the reverse thermosyphon were compared. The occurrence of dry out limit and expansion boiling phenomena were identified by experimental work. The amount of optimal heat transfer in reverse thermosyphon was adjudged with respect to the thermal resistance, temperature between evaporator and condenser, fill ratio, tilt angle, heat transfer coefficient, thermal efficiency, etc. In this paper, the effects of major control parameters on thermal performance of passive heat transfer of solar energy are discussed.
 HIGHLIGHTS
 
 Continuous operation of reverse thermosyphon with 2 working media, a bubble pump and using solar thermal collector as heat source and finned U-tube for a passive downward heat transfer is feasible
 CFD model with a 2-D geometry considering multi-phase flow has successfully reproduced both the characteristics of fluid flow and heat transfer
 Optimal heat transfer was adjudged with respect to the thermal resistance, temperature between evaporator and condenser, fill ratio, tilt angle, heat transfer coefficient, and thermal efficiency
 Reduced rate of heat loss, increased rate of energy storage by integrating PCM directly inside the U-tube, and enhanced heat transfer by incorporating nanofluid with high heat capacity were realized
 Suitable working media selection was vital and contributed in improved system efficiency and reduced operational cost
 
 GRAPHICAL ABSTRACT

Magnesium nanoparticle synthesis from powders via LASIS – Effects of liquid medium, laser pulse width and ageing on nanoparticle size, concentration, stability and electrical properties

Mg nanoparticles (NPs) in a range of sizes (20–213 nm) were fabricated via LASIS from powders within two different liquid mediums, namely DI water and isopropyl alcohol for the first time. The effect of laser pulse width (0.60, 0.92 and 1.24 ns) and liquid medium on the UV–Visible and Fourier-transform infra-red spectra, zeta potentials, concentration (particles/ml), colloidal density, mean NP size and electrical properties were investigated. Nanoparticle ageing experiments were conducted whereby the NP size was analysed soon after fabrication and then again after 9-months of shelf life at room temperature. The effect of the colloid storage temperature after fabrication (−17, 4 and 20 °C) on the NP concentration was investigated. DI water-synthesised Mg NPs tend to be larger (89 ± 4 nm) than IPA-synthesised Mg NPs (52 ± 6 nm). IPA-synthesised NPs provided better colloidal stability (zeta potential = +158.7 ± 13.5 mV) than DI water (zeta potential = +16.6 ± 3.1 mV). Mg NPs reduced the resistivity of glass from 102 to 92 Ω/square which gave them a potential application in electronics. Mg NPs have versatile applications including surface coating, printed electronics, battery technology and antibacterial agents.

In vitro multiplication of agave tobala (Agave potatorum Zucc.) using Ebb-and-Flow bioreactor

Agave tobala (Agave potatorum Zucc.) is one of the most important wild species to produce a Mexican alcoholic beverage called mezcal. Unfortunately, natural propagation is not sufficient to fulfill the demands. The objective of this study was to develop a protocol for the commercial micropropagation of A. potatorum using a temporary immersion system (TIS). The effect of liquid medium using an Ebb-and-Flow bioreactor and semi-solid medium as a control treatment was compared. In TIS different immersion frequencies, medium volume per explant, and additional air supply were evaluated. In all experiments, the hyperhydricity percentage, number of shoots per explant, as well as shoot length, and total chlorophyll content were recorded at 60 d of culture. In addition, the survival rate during acclimatization was evaluated at 60 d. The results show that the temporary immersion system with an immersion of 2 min every 12 h, with a culture medium volume of 50 mL and an air supply frequency of 2 min every 12 h obtained the best development parameters compared to semi-solid medium, with 29.60 shoots per explant, an average shoot length of 2.01 cm, and an hyperhydricity percentage of 3.33. The highest chlorophyll content was observed in semi-solid culture media and temporary immersion every 12 and 16 h. Regarding medium volume per explant, the highest chlorophyll contents were found in the volumes of 100, 75 and 50 mL per explant. For air supply, the frequencies of 8 and 4 h had a higher chlorophyll content. For acclimatization, no differences in percent survival were found between the culture systems evaluated. In conclusion, this study shows that the use of Ebb-and-Flow bioreactor is a suitable alternative for large-scale micropropagation of A. potatorum.

Effect of liquid medium and laser processing parameters on the fabrication of carbon nanoparticles via pulsed laser ablation in liquid towards paper electronics

Paper-based electronics with carbon nanomaterials incorporated have several advantages including recyclability, biodegradability, non-toxicity, low cost and ease of fabrication and disposal. Herein, carbon nanoparticles (CNPs) were fabricated by Pulsed Laser Ablation in Liquid (PLAL) using three different liquid mediums, i.e. deionised (DI) water, ethanol and a magnesium-based solution. The as-fabricated nanocolloids were used as conductive inks and deposited on paper substrates. The resulting nanoparticle (NP) coatings were subjected to electrical resistivity tests via 4-point probe. Ultraviolet–Visible spectroscopy (UV–Vis) studies were conducted to determine the presence of nanomaterials. All nanocolloids produced within DI water had three distinct UV–Vis absorbance peaks at 200, 216 and 225 nm while nanocolloids produced in ethanol exhibited more peaks and significantly higher absorbance values in the range from 210 nm to 300 nm. Dynamic Light Scattering and field emission scanning electron microscopy (FESEM) were used to analyse samples for particle size and morphology respectively. The liquid medium in which PLAL was conducted was found to significantly affect the NP mean size, conductivity and surface chemistry of the resulting NPs. DI water produced smaller nanoparticles (NPs) (10–82 nm) than ethanol (60–143 nm) and magnesium-based solution (263–1389 nm) within the process parameters studied herein. The laser scan speed and fluence have a combined effect on the NP mean diameter. The surface chemistry of the NPs produced in the magnesium-based solution was analysed via X-ray photoelectron spectroscopy and it was found that the Mg, Li and Si atoms are adsorbed by the carbon NPs leading to higher conductivity of the coated paper substrates.

Effect of liquid media and laser energy on the preparation of Ag nanoparticles and their nanocomposites with Au nanoparticles via laser ablation for optoelectronic applications

The nanostructured materials from Ag and Au@Ag core/shell bimetallic were synthesized by pulsed infrared laser ablation process in different liquid media technique in just one-pot step. By varying the surrounding media by metallic precursor solution and the laser energy, the monometallic nanoparticles were changed to bimetallic nanocomposites in a form of core/shell structure with tuning their shell thickness. The prepared nanostructured materials were examined by different spectroscopic techniques to inform their physicochemical properties. The characterization techniques proved that the crystallinity of prepared samples. Besides, the bimetallic nanocomposite structure has a core/shell form with Au in the core and Ag in shell. Also, as the laser intensity raises, the Ag-shell’s thickness grows, and the core/shell diameter increases, which was affected in their linear and nonlinear optical properties. Their linear properties were investigated depended on Mie theory. Besides, the nonlinear optical parameters were determined by Z-scan technique, which demonstrated that the nonlinear optical properties of a shell can be tuned depending on their thickness. The prepared core/shell nanocomposites with different particle sizes confirmed the capability for possible application in optoelectronic applications as good optical limiting materials.

The production of graphene by direct liquid phase exfoliation of graphite at moderate sonication power by using low boiling liquid media: The effect of liquid media on yield and optimization

There are many production methods for graphene production. One of the most successful production methods in terms of scale-up is liquid phase exfoliation (LPE) method. In this study, after optimizing the sonication time and sonication power that are effective in the production to increase the efficiency of the LPE method, the experiments were continued at moderate sonication powers and the effect of liquid media, another important parameter, was examined. In this study, hexagonal graphite powders were subjected to direct liquid phase exfoliation process by using different liquid media (N-Methyl-2-Pyrrolidone (NMP), N,N-Dimethylformamide (DMF), ethanol, 2-propanol, acetone, methanesulfonic acid, ethanol + Sodium dodecyl sulphate (SDS), 2-propanol + SDS) and the obtained samples were characterized. As a result of the characterization, the liquid media with the highest efficiency was determined to be NMP. Besides, it was observed that a new hybrid solvent obtained by adding a surfactant such as SDS into low-cost and environmentally friendly liquid media such as ethanol and 2-propanol showed a higher efficiency than NMP. It was observed that 3–5 layer graphene ranged between 15 and 19 wt% in either graphene produced by using hybrid solvents containing NMP or SDS. The amount of double or single-layer graphene was negligibly small. The production with the lowest efficiency was observed in the use of acetone. The produced graphenes were dispersed in the liquid and their sedimentation time was observed. The sedimentation time of graphenes, produced using NMP and SDS-doped hybrid solvents, in liquid was more than 120 days. The sedimentation time of graphene produced using acetone was less than 20 days. In the use of graphene as a reinforcing material or adsorbent, large amounts of graphene are needed. In such applications, mass production of graphene is important rather than the number or quality of sheets of graphene. Therefore, optimization of production parameters of LPE method, which is suitable for mass production, is significance.

The effect of liquid medium on vibration and control of the AFM piezoelectric microcantilever.

This article investigates the vibration motion and control of the piezoelectric microcantilever (MC) of the atomic force microscope in the amplitude mode in a liquid environment for both free and forced vibrations. The modeled MC includes two electrode layers, a piezoelectric layer, and the geometric discontinuities as a result of these layers and the change in the MC cross section at the probe-MC contact point is modeled. The equations of motion are derived using Hamilton's principle and then discretized with the aid of the finite element method. The system frequency and time response in the free vibration mode when placed in a liquid medium are compared with experimental results. Also, the sample surface topography in the noncontact mode, when passing through the surface roughness, has been modeled as rectangular and wedge-shaped. Furthermore, the control of piezoelectric MC in two cases of near and far from the sample surface is examined. In the case of far from the surface, the system is controlled using the piezoelectric layer installed on the beam, whereas in the case of near the surface, the piezo is turned off due to the existence of nonlinear forces such as Van der Waals and Derjaguin, Muller, and Toporov contact forces and the control is achieved through the base excitation. For system control modeling, the robust fuzzy sliding mode control (FSMC) approach is utilized and the results are compared with those of the simple sliding mode control (SMC) as well as proportional, integral, and derivative control. The presented FSMC approach can remarkably reduce the chattering phenomenon at the SMC input in the liquid medium and accordingly improve the results compared to the other two methods.

The Effect of Liquid Media on the Efficiency of Graphene Production by Liquid-Phase Exfoliation from Micromechanically Pre-exfoliated Graphite

Graphene can be produced using several methods. One of the most successful production methods in terms of scale-up is liquid-phase exfoliation (LPE). With this method, the solvent employed during exfoliation is a critical parameter. In the present study, hexagonal graphite powders were micromechanically exfoliated using a low-energy ball mill, and the expanded graphite was then obtained from the micromechanically exfoliated graphite. Finally, the graphenes were synthesized using LPE. N-Methyl-2-pyrrolidone (NMP) and N,N-dimethylformamide (DMF) were the most successful solvents used for producing graphene by the LPE method. Naphthalene and sodium dodecyl sulfate (SDS) were added to these solvents to improve production efficiency. The chemicals yielding the best results were determined by analyzing the graphenes. While 3–5-layer graphenes were produced in all liquid media, the amount of high-quality graphenes differed among samples. The most efficient graphene was obtained in the samples produced using NMP + SDS liquid media. The production efficiency obtained in these samples as a result of the exfoliation process was 25%. The samples produced with NMP were more successful than those produced with DMF.

Effect of liquid medium on shoots amplification, in vitro flowering and ex vitro rooting of Oldenlandia umbellata L. - A dye yielding medicinal herb

Oldenlandia umbellata L. gains importance due to its medicinal properties and the presence of anthraquinones based natural dyes in the roots. Present study describes the effect of Murashige and Skoog’s (MS) liquid medium (full strength) on in vitro regeneration, flower bud induction and ex vitro rooting in O. umbellata. Shoot segments with 2-3 nodes (each node with 2 axillary buds) served as explants for establishment of cultures. The liquid medium augmented with 2.0 mg L-1 6-benzylaminopurine (BAP) with additives (50 mg L-1 of ascorbic acid and 25 mg L-1 each of arginine, adenine sulphate and citric acid) was effective for shoot bud induction (6.4±0.19 shoots per explant within 2-3 weeks). The shoots were further multiplied (89.3±1.07 shoots, 2-3 weeks) when the shoot clusters obtained from the culture initiation directly transferred to the full-strength MS liquid medium incorporated with 1.0 mg L-1 BAP and 0.5 mg L-1 indole-3 acetic acid (IAA) with additives. Flower buds were induced (12.0±0.15 buds per shoot) when the shoots were cultured on 1.0 mg L-1 BAP and kinetin (Kin, 6-furfurylaminopurine) and 0.5 mg L-1 of IAA at 45 µmol m−2 s−1 SFPD (Spectral Flux Photon Density) light intensity for 14/10h (light/dark) photoperiod. The adventitious roots were induced on 1/4 strength MS medium supplemented with 1.5 mg L-1 indole-3 butyric acid (IBA). Ex vitro rooting was achieved (16.0±0.53 roots per shoot) by pulse treatment of the shoots with 300 mg L-1 IBA for 2 min. The in vitro produced plantlets were acclimatized in the greenhouse and finally translocated to the in vivo conditions with 93 % success rate. This is the foremost (use of liquid MS medium) and cost-effective method for large scale multiplication of O. umbellata.

Effect of liquid medium on shoots amplification, in vitro flowering and ex vitro rooting of Oldenlandia umbellata L. - A dye yielding medicinal herb

Oldenlandia umbellata L. gains importance due to its medicinal properties and the presence of anthraquinones based natural dyes in the roots. Present study describes the effect of Murashige and Skoog’s (MS) liquid medium (full strength) on in vitro regeneration, flower bud induction and ex vitro rooting in O. umbellata. Shoot segments with 2-3 nodes (each node with 2 axillary buds) served as explants for establishment of cultures. The liquid medium augmented with 2.0 mg L-1 6-benzylaminopurine (BAP) with additives (50 mg L-1 of ascorbic acid and 25 mg L-1 each of arginine, adenine sulphate and citric acid) was effective for shoot bud induction (6.4±0.19 shoots per explant within 2-3 weeks). The shoots were further multiplied (89.3±1.07 shoots, 2-3 weeks) when the shoot clusters obtained from the culture initiation directly transferred to the full-strength MS liquid medium incorporated with 1.0 mg L-1 BAP and 0.5 mg L-1 indole-3 acetic acid (IAA) with additives. Flower buds were induced (12.0±0.15 buds per shoot) when the shoots were cultured on 1.0 mg L-1 BAP and kinetin (Kin, 6-furfurylaminopurine) and 0.5 mg L-1 of IAA at 45 µmol m−2 s−1 SFPD (Spectral Flux Photon Density) light intensity for 14/10h (light/dark) photoperiod. The adventitious roots were induced on 1/4 strength MS medium supplemented with 1.5 mg L-1 indole-3 butyric acid (IBA). Ex vitro rooting was achieved (16.0±0.53 roots per shoot) by pulse treatment of the shoots with 300 mg L-1 IBA for 2 min. The in vitro produced plantlets were acclimatized in the greenhouse and finally translocated to the in vivo conditions with 93 % success rate. This is the foremost (use of liquid MS medium) and cost-effective method for large scale multiplication of O. umbellata.

Discretized Modeling of Motionless Printing Based on Retarded Bending Motion and Deposition Control of Electrically Driven Jet

This study is on developing a simple motionless printing in which polyacrylonitrile and N,N-dimethylformamide solution is electrically driven from a fixed nozzle head in a coagulation medium of chloroform and mineral oil. The effect of liquid medium on the bending instability of the jet is studied using the discretized model and experiments. Furthermore, for motionless printing, the inhibited bending motion of the jet is used to control the deposition of the jet to form a square pattern on the collector. The resulting fiber collection pattern obtained from the experiments is favorably compared with the simulation results. In addition, the effects of the switching time and distance between the collector plates on the accuracy of the square and circle three-dimensional patterns are studied from the simulation.

The changes of surface properties and enhancement of B2O3 leaching ratio of boron concentrate via wet ball milling

With the ascharite used up in China, boron concentrate was used as raw material for extracting B2O3. In this study, an environmental wet ball milling (WBM) method was proposed to enhance the B2O3 leaching ratio, and the effect of liquid medium, rotational speed and milling time on the properties of boron concentrate in WBM process was discussed. This surface properties of milled samples was characterized by BET, PSD, SEM, XRD, FTIR, TG-DSC and XPS analyses, and their surface free energy was calculated by the measurement of contact angle. The role of liquid medium and the relationship between the surface properties was also explored. Our research shows liquid medium helps avoid the agglomeration and plays a dispersing role in the process of milling, thereby promoting the increasing of the specific surface area from 16.65m2/g to 35.84m2/g after milling for 60min. Besides, the B2O3 leaching ratio can be enhanced from 67.52% to 86.24% under the same conditions. The increased amorphous extent of crystal structure and the weakening of chemical bonds caused by the milling process helps produce an increasing in the number of reactivity points, making chemical reactions easier. With the increasing of surface free energy from 26.88mJ/m2 to 39.55mJ/m2 after milling, the hydrophilicity of the sample is enhanced, as well as the absorption of solvent and OH– in the leaching solution, thus promoting the leaching reaction and the enhancement of B2O3 leaching ratio.

Effects of laser fluence and liquid media on preparation of small Ag nanoparticles by laser ablation in liquid

This study aims to assess a method for preparation of small and highly stable Ag nanoparticles by nanosecond laser ablation in liquid. Effect of liquid medium and laser fluence on the size, morphology and structure of produced nanoparticles has been studied experimentally. Pulses of a Nd:YAG laser of 1064nm wavelength at 35ns pulse width at different fluences were employed to irradiate the silver target in different environments (water, ethanol and acetone). The UV-Visible absorption spectra of nanoparticles exhibit surface plasmon resonance absorption peak in the UV region. STEM and TEM micrographs were used to evaluate the size and shape of nanoparticles. The stability of silver colloids in terms of oxidation at different liquid media was analyzed by SAED patterns. The results showed that characteristics of Ag nanoparticles and their production rate were strongly influenced by varying laser fluence and liquid medium. Particles from 2 to 80nm of diameter were produced using different conditions and no oxidation was found in ethanol and acetone media. This work puts in evidence a promising approach to produce small nanoparticles by using high laser fluence energy.

Effect of Liquid Media on the Formation of Multi-Layer Graphene-Synthesized Metal Particles.

We report a simple approach for the production of copper nanoparticles by a wire explosion process that creates different structures in deionized (DI) water versus isopropyl alcohol (IPA) liquid media. In DI water, copper nanoparticles (CNs) are formed, while multi-layer graphene-synthesized copper nanoparticles (MGCNs) with a high degree of graphitization are formed in the IPA liquid media. The nanoparticles have an average diameter ranging from 10 nm to 300 nm and a quasi-spherical morphology. The morphologies and sizes of nanoparticles formed via this method were characterized by high-resolution transmission electron microscopy (HRTEM), field-emission scattering electron microscopy (FESEM), and analysis of dynamic light scattering (DLS). The microstructures and chemical bonding of the nanoparticles were studied by X-ray diffraction (XRD), Raman spectra measurement, and X-ray photoelectron spectroscopy (XPS). This results show an easily reproducible way to synthesize metal-core nanoparticles with multi-layer graphene shells based onto the liquid media used during synthesis. These materials can be used in the field of energy storage and as additives in the near future.

Defects in ZnO nanoparticles laser-ablated in water–ethanol mixtures at different pressures

The effect of liquid medium and its pressure on the photoluminescence of ZnO nanoparticles prepared via laser ablation of Zn targets in various water–ethanol mixtures is studied. As the ethanol content increases, the photoluminescence of the product changes, while metallic zinc is observed to emerge in nanomaterials prepared in ethanol-rich environments. The applied pressure had a less profound effect, mainly affecting materials produced in water or water–ethanol, and much less those generated in pressurized ethanol. Tuning the reactivity of the liquid and pressurizing it during laser ablation is demonstrated to be promising for tailoring the emission properties of the product.

Effect of liquid medium on size and shape of nanoparticles prepared by pulsed laser ablation of tin

The effect of the surrounding liquid medium on the size, shape and optical absorption of synthesized nanoparticles prepared by laser ablation of pure tin in different liquids is investigated. The liquid not only confines the ablated species at the liquid–solid interface, but also it acts as a mediator for chemical reaction at the liquid–solid interface. The liquid media surrounding the target is thus an important factor affecting the shape, mean size, size distribution and composition of the particles. The ablation of tin target was carried out in deionized water, ethanol and acetone medium, leading to formation of tin and tin oxide nanoparticles of various sizes and shapes. Electron microscopy and optical absorption were employed for characterization of the particle size, shape and optical properties, respectively. The effect of surfactant was also studied by carrying out ablation in aqueous sodium dodecyl sulfate (SDS) or cetyl trimethyl ammonium bromide (CTAB) solution. It was observed that the average particle size and size distribution are considerably reduced by using surfactant.

Somatic embryogenesis and plant regeneration in Catharanthus roseus

Embryogenic callus in Catharanthus roseus was initiated from hypocotyl on Murashige and Skoog’s (MS) medium supplemented with 1.0–2.0 mg dm−3 of 2,4-dichlorophenoxyacetic acid (2,4-D) or chlorophenoxyacetic acid (CPA). Calli from other sources were non-embryogenic. Numerous somatic embryos were induced from primary callus on MS medium suplemented with naphthalene acetic acid (NAA) within two weeks of culture. Embryo proliferation was much faster on medium supplemented with 6-benzylaminopurine (BAP). After transfer to medium with gibberellic acid (GA3, 1.0 mg dm− 3) mature green embryos were developed and germinated well into plantlets on MS liquid medium supplemented with 0.5 mg dm−3 BAP. Later, embryos with cotyledonary leaves were subjected to different auxins treatments for the development of roots. Before transfer ex vitro, plantlets were cultivated on half strength MS medium containing 3 % sucrose and 0.5 mg dm−3 BAP for additional 2 weeks. Additionally, the effect of liquid medium has been evaluated at different morphogenetic stages.

IMPROVEMENT OF BULB FORMATION IN MICROPROPAGATED TULIPS BY TREATMENT WITH NAA AND PACLOBUTRAZOL OR ANCYMIDOL

Bulb formation is an essential stage in tulip micropropagation via cyclic shoot multiplication because only bulbs show high rooting ability and good field performance. The stage of bulb formation in vitro consists of three phases: 1) development of bulb primordia in shoots at the end of the last subculture prior to cooling; 2) induction of bulbing process by cooling of shoots; 3) bulb formation at 23°C. Shoots of tulips 'Prominence', 'Blenda' and 'Blue Parrot' multiplied on the medium with thidiazuron (TDZ), were used for the experiments. The effects of liquid media (with or without growth regulators) added into the shoot cultures prior to cooling were examined in relation to the efficiency of bulb formation. The liquid media were added at the end of the last eight-week-multiplication subculture. 1-naphthylacetic acid (NAA) at 2 mg L -1 and inhibitors of gibberellin biosynthesis, ancymidol or paclobutrazol (1-2 mg L -1 ) were used. The shoots were grown on doublephase media for six weeks. The control subculture prior to cooling was prolonged to 14 weeks, but the liquid medium was not added. The shoots were then transferred onto the sucrose-rich medium without growth regulators and cooled at 5°C for three months. Subsequently, they were cultured for bulb formation at 23°C for 2-5 months. The application of the liquid medium containing NAA and/or ancymidol or paclobutrazol significantly enhanced the efficiency of bulb formation expressed by the ratio of the properly formed bulb to shoot numbers x 100%. For 'Prominence', it varied from 42.9% noted in control to 60.1-104.2%, for 'Blenda' - from 68.8% in control to 121.7-125.0% and in 'Blue Parrot' bulbing was sporadic in control but on double-phase ranged from 14.5% to 41.6%.