Showing papers on "Zeatin published in 1999"

Uniconazole-induced tolerance of rape plants to heat stress in relation to changes in hormonal levels, enzyme activities and lipid peroxidation

Abstract: Winter rape (Brassica napus L. cv. 601) seedlings were treated with 50 mg.l-1of foliar-applied uniconazole and then exposed to heat stress with a light/dark temperature regime of 43 °C/38 °C for 3 days at the stem elongation stage. Heat stressed plants contained lower endogenous GA3, IAA and zeatin contents than the controls, while ABA content and ethylene level were increased significantly. Uniconazole-treated plants had lower endogenous GA3 and IAA contents, and higher zeatin and ABA contents and ethylene levels. Leaf chlorophyll content and respiratory capacity of roots were reduced markedly after plants were subjected to heat stress, and foliar sprays of uniconazole retarded the degradation of chlorophyll and increased respiratory capacity of roots. Following exposure to heat, the activities of superoxide dismutase and peroxidase were significantly reduced. Uniconazole-induced heat tolerance was accompanied by increased activities of various antioxidant enzymes. Foliar applications of uniconazole reduced electrolyte leakage and malondialdehyde accumulation caused by heat stress, suggesting that uniconazole may have decreased heat-induced lipid peroxidation and membrane damage. Foliar sprays of uniconazole increased the tolerance of rape plants to heat stress.

Isolation of a cytokinin gene, ZOG1, encoding zeatin O-glucosyltransferase from Phaseolus lunatus

Abstract: Zeatin is the most active and ubiquitous of the naturally occurring cytokinins. The O-glucoside of zeatin, found in all plants examined, is considered to be important in cytokinin transport, storage, and protection against cytokinin oxidases. The enzyme UDPglucose:zeatin O-glucosyltransferase (EC 2.4.1.203) was previously isolated from Phaseolus lunatus seeds. Immunoscreening of an expression library with monospecific antibody resulted in the isolation of a cDNA encoding the enzyme. The recombinant protein efficiently converts labeled zeatin to O-glucosylzeatin and has properties similar to the native enzyme. The cDNA of 1.5 kb contains an ORF encoding a 51.4-kDa polypeptide of 459 amino acids. The sequence is unique based on a blast search of data bases. The genomic sequence, isolated with PCR using specific primers based on the cDNA sequence, does not contain introns. The cloning of this gene provides the tools for further study of the regulation of cytokinin metabolism and analysis of the precise role of O-glucosylzeatin in plant development.

Dynamics of Cytokinins in Apical Shoot Meristems of a Day-Neutral Tobacco during Floral Transition and Flower Formation

Abstract: This study considered cytokinin distribution in tobacco (Nicotiana tabacum L.) shoot apices in distinct phases of development using immunocytochemistry and quantitative tandem mass spectrometry. In contrast to vegetative apices and flower buds, we detected no free cytokinin bases (zeatin, dihydrozeatin, or isopentenyladenine) in prefloral transition apices. We also observed a 3-fold decrease in the content of cytokinin ribosides (zeatin riboside, dihydrozeatin riboside, and isopentenyladenosine) during this transition phase. The group concluded that organ formation (e.g. leaves and flowers) is characterized by enhanced cytokinin content, in contrast to the very low endogenous cytokinin levels found in prefloral transition apices, which showed no organogenesis. The immunocytochemical analyses revealed a differing intracellular localization of the cytokinin bases. Dihydrozeatin and isopentenyladenine were mainly cytoplasmic and perinuclear, whereas zeatin showed a clear-cut nuclear labeling. To our knowledge, this is the first time that this phenomenon has been reported. Cytokinins do not seem to act as positive effectors in the prefloral transition phase in tobacco shoot apices. Furthermore, the differences in distribution at the cellular level may be indicative of a specific physiological role of zeatin in nuclear processes.

A gene encoding the cytokinin enzyme zeatin O-xylosyltransferase of Phaseolus vulgaris.

Abstract: Zeatin is the most active and ubiquitous form of the naturally occurring cytokinins. Glycosyl conjugates of zeatin are found in many plant tissues and are considered important for storage and protection against degradative enzymes. Two enzymes catalyzing the formation of O-glycosyl derivatives of zeatin have been characterized, O-glucosyltransferase and O-xylosyltransferase, occurring in seeds of lima bean (Phaseolus lunatus) and bean (Phaseolus vulgaris), respectively. Recently, the ZOG1 gene (zeatin O-glucosyltansferase) was isolated from P. lunatis (Martin et al., 1999). Based on the ZOG1 sequence, the ZOX1 gene (zeatin O-xylosyltransferase) was cloned from P. vulgaris. ZOX1 contains an open reading frame of 1362 bp that codes for a 454-amino acid peptide of 51 kD. The recombinant protein has properties identical to the native enzyme: it catalyzes O-xylosylzeatin formation with UDP-Xyl as a glycosyl donor but does not recognize UDP-Glucose as a substrate. The ZOX1 and ZOG1 genes exhibit 93% identity at the nucleotide level and 90% similarity at the amino acid level. Neither gene contains introns. These zeatin-specific genes and their promoters will be useful for studies of the regulation of active versus storage forms of cytokinins. Comparison of sequences encoding similar enzymes with distinct substrate specificity may lead to identification of epitopes specific to cytokinin and glycosyl donor molecules.

Plant regeneration from seedling explants of Eucalyptus grandis × E. urophylla

Abstract: Hypocotyls, cotyledons, cotyledonary nodes and primary leaves were used as explants to establish a regeneration protocol for Eucalyptus grandis × E. urophylla. These seedling-derived explants were incubated on a modified MS medium (SP medium), supplemented with 2.0 μM TDZ. After 1 month, the calluses obtained were transferred to SP medium containing different concentrations of BA and NAA or zeatin and NAA. Shoots were induced from these calluses at a high frequency. Shoot elongation was then stimulated on SP medium supplemented with BA, NAA and GA3 for 20 to 30 days. For rooting, 50 mm long shoots were cultivated on root induction medium containing IBA (2.5 μM) for different periods and then transferred to the same medium but without auxin, for 30 days. Plantlets were then successfully transplanted to greenhouse conditions.

Cytokinins in Tobacco and Wheat Chloroplasts. Occurrence and Changes Due to Light/Dark Treatment

Abstract: Although cytokinins (CKs) affect a number of processes connected with chloroplasts, it has never been rigorously proven that chloroplasts contain CKs. We isolated intact chloroplasts from tobacco ( Nicotiana tabacum L. cv SR1) and wheat ( Triticum aestivum L. cv Ritmo) leaves and determined their CKs by liquid chromatography/tandem mass spectroscopy. Chloroplasts from both species contained a whole spectrum of CKs, including free bases (zeatin and isopentenyladenine), ribosides (zeatin riboside, and isopentenyladenosine), ribotides (isopentenyladenosine-5′-monophosphate, zeatin riboside-5′-monophosphate, and dihydrozeatin riboside-5′-monophosphate), and N -glucosides (zeatin- N 9 -glucoside, dihydrozeatin- N 9 -glucoside, zeatin- N 7 -glucoside, and isopentenyladenine- N -glucosides). In chloroplasts there was a moderately higher relative amount of bases, ribosides, and ribotides than in leaves, and a significantly increased level of N 9 -glucosides of zeatin and dihydrozeatin. Tobacco and wheat chloroplasts were prepared from leaves at the end of either a dark or light period. After a dark period, chloroplasts accumulated more CKs than after a light period. The differences were moderate for free bases and ribosides, but highly significant for glucosides. Tobacco chloroplasts from dark-treated leaves contained zeatin riboside- O -glucoside and dihydrozeatin riboside- O -glucoside, as well as a relatively high CK oxidase activity. These data show that chloroplasts contain a whole spectrum of CKs and the enzymatic activity necessary for their metabolism.

Medium optimization for efficient somatic embryogenesis and plant regeneration from immature inflorescences and immature scutella of elite cultivars of wheat, barley and tritordeum

Abstract: Media have been developed for somatic embryogenesis and plant regeneration from immature inflorescences and immature scutella of elite cultivars of wheat, barley and tritordeum. For wheat and tritordeum inflorescences, regeneration from embryogenic calluses induced on medium with picloram was almost twice as efficient as regeneration from cultures induced on 2,4-dichlorophenoxyacetic acid (2,4-D). The addition of zeatin at 5 or 10 mg l−1 to regeneration media had a positive effect on regeneration. For scutella, the highest frequencies of embryogenesis (85%) and regeneration (50%) was obtained using an induction medium containing 2 mg l−1 of 2,4-D and half concentration of aminoacids. The morphogenetic capacities of 19 different cultivars of wheat, barley and tritordeum were compared, and clear differences were found both between explants and genotypes. In wheat, embryogenic capacity from inflorescences (average of 92%) was higher than from immature scutella (average of 62%). However, shoot regeneration from scutella was clearly higher than from inflorescences (averages of 63%, and 18% respectively). Frequencies of regeneration in wheat and barley varied widely among the cultivars tested and in both species no difference was found between spring and winter varieties.

Identification and quantitation by GC-MS of zeatin and zeatin riboside in xylem sap from rootstock and scion of grafted apple trees

Abstract: Zeatin and zeatin riboside were identified by full-scan gas chromatography-mass spectrometry (GC-MS) in xylem sap of clonal apple rootstocks (M27, M9 and MM106) These rootstocks exhibit a wide range of control over tree size when grafted to a common scion The concentrations of zeatin and zeatin riboside were measured by GC-MS selected ion monitoring (SIM) in shoot xylem sap and root pressure exudate obtained from these rootstocks and from trees of ‘Fiesta’ scion grafted onto the rootstocks Zeatin was the predominant cytokinin in xylem sap from the dwarfing rootstocks, M27 and M9, while zeatin riboside was the predominant cytokinin in xylem sap from the more invigorating rootstock MM106 Cytokinin concentrations (ng ml−1) in root pressure exudate and shoot xylem sap, (ie from above the graft union in composite trees), increased with increasing vigour of the rootstock, irrespective of whether the plants were non-grafted rootstocks, or were composite plants of ‘Fiesta’ scion grafted onto the rootstocks Cytokinin content (ng shoot−1) of shoot sap differed with rootstock; the more invigorating (MM106) had greater amounts of cytokinins than the more dwarfing (M9 and M27) rootstocks These results are discussed in relation to possible influences of roots on the growth of shoots via cytokinin supplies in the xylem sap

Endogenous cytokinin accumulation and cytokinin oxidase activity during shoot organogenesis of Petunia hybrida

Abstract: Changes in endogenous cytokinin content and cytokinin oxidase activity were characterized in leaf explants from two Petunia hybrida Vilm. genetic lines which differed in their shoot organogenic response to exogenous N 6 -benzyladenine (BA). Endogenous cytokinin content in leaf explants of the highly shoot organogenic line, St40, increased 1.7-fold during the shoot induction phase (days 6-10) and had an additional 2.6-fold cytokinin increase correlated with the shift from induction to the shoot development phase. The cytokinins isopentenyl adenine (iP) and isopentenyl adenosine (iPAR) increased, while the cytokinins zeatin, zeatin riboside and dihydrozeatin remained at consistently low levels. In contrast, isoprenoid cytokinins did not accumulate in petunia TLV1 leaf explants which were incapable of shoot induction during 12 days of culture with BA. Cytokinin oxidase activity continuously increased in leaf explants of both petunia genotypes in response to BA, with a larger increase in St40. These results suggest that the differences in organogenic response in the two petunia genotypes may be the result of differences in BA uptake and metabolism which subsequently affects the accumulation of isoprenoid cytokinins and the activity of cytokinin oxidase in the early stages of shoot development.

Role of endogenous purine metabolism in thidiazuron-induced somatic embryogenesis of peanut (Arachis hypogaea L.)

Abstract: Somatic embryogenesis was induced at the hypocotyledonary notch region of intact peanut (Arachis hypogaea L) seedings cultured on a medium containing 10 μmol·L−1 thidiazuron (TDZ) Inclusion of the purine analogs 2,6-diaminopurine (DAP), azaadenine or azaguanine to the thidiazuron amended medium inhibited the embryogenic response of the seedlings DAP-mediated inhibition was not overcome by the addition of adenine sulphate Inhibition of the embryogenic response by DAP provides evidence that the TDZ-induced accumulation of purine cytokinins is an essential component of TDZ-induced somatic embryogenesis process Analyses of the endogenous level of purine metabolites indicated that supplementation of the media with TDZ resulted in an overall increase in the endogenous cytokinins while DAP inhibited the purine recycling resulting in decreased levels of endogenous adenine and zeatin

Bending Shoots Stimulates Flowering and Influences Hormone Levels in Lateral Buds of Japanese Pear

Abstract: Flower development of the lateral buds was accelerated in Japanese pear ( Pyrus pyrifolia (Burm.) Nak.) when vertical shoots were bent at a 45 ° angle in late June. The indole-3-acetic acid (IAA) concentration in lateral buds on vertical (control) shoots increased in mid-July, while remaining nearly constant in bent shoots. The abscisic acid (ABA) concentration of buds in bent shoots rose between 4 July and 15 Aug., whereas control shoots exhibited an increase in concentration followed by a decline. Gibberellin 4+7 (GA4+7) concentration was high on 16 June, and then declined by 4 July, with the decline being greatest in bent shoots. Gibberellin 4+7 concentration was higher in the buds on vertical shoots than in those on bent shoots for much of July. The concentrations of zeatin- type cytokinins (CKs) in lateral buds were higher in bent shoots than in vertical shoots. Bending of pear shoots may weaken competition between buds and other organs through altering hormone levels in lateral buds, resulting in acceleration of flower development.

Influence of White Clover Mosaic Potexvirus Infection on the Endogenous Cytokinin Content of Bean

Abstract: The cytokinin content in the primary leaves of bean ( Phaseolus vulgaris ) was monitored for 10 d after inoculation with white clover mosaic potexvirus. The cytokinins were isolated, purified, separated by high-performance liquid chromatography, and quantified by radioimmunoassay. The cytokinins detected at the time of inoculation (d 0) were: (a) the free bases, zeatin (Z), dihydrozeatin (DZ), and isopentenyladenine; (b) the riboside, DZ riboside (DZR); (c) the O- glucosides of DZ, DZR, and Z riboside; (d) the nucleotides, Z riboside-5′-monophosphate and isopentenyladenosine-5′-monophosphate; and (e) trace amounts of Z-9-glucoside and DZ-9-glucoside. During the 10 d after inoculation with white clover mosaic potexvirus, marked quantitative changes in this cytokinin profile were observed. The concentration of the free bases and DZR decreased, accompanied by an increase in the 9-glucosides and the nucleotides. Virus titer increased rapidly 3 d after inoculation, attaining a maximum level at d 5. This increase coincided with the increases in the 9-glucosides and the nucleotides. We propose that the decline in the cytokinin free bases and riboside may allow the increase of virus titer in bean and lead to the senescence of infected leaves.

Adventitious shoot regeneration in cultures of Humulus lupulus L. (hop) cvs. Brewers Gold and Nugget

Abstract: A very efficient protocol for plant regeneration from two commercial Humulus lupulus L. (hop) cultivars, Brewers Gold and Nugget has been established, and the morphogenetic potential of explants cultured on Adams modified medium supplemented with several concentrations of cytokinins and auxins studied. Zeatin at 4.56 μm produced direct caulogenesis and caulogenic calli in both cultivars. Subculture of these calli on Adams modified medium supplemented with benzylaminopurine (4.4 μm) and indolebutyric acid (0.49 μm) promoted shoot regeneration which gradually increased up to the third subculture. Regeneration rates of 60 and 29% were achieved for Nugget and Brewers Gold, respectively. By selection of callus lines, it has been possible to maintain caulogenic potential for 14 months. Regenerated plants were successfully transferred to field conditions.

Cytokinins in pathogenesis and disease resistance of Pyrenophora teres-barley and Dreschslera maydis-maize interactions during early stages of infection.

Abstract: Infection of Hordeum vulgare L. by Pyrenophora teresand of Zea mays by Dreschslera maydis were characterized by ‘green island’ formation, higher cytokinin levels and accumulation of metabolites in the infected areas. Higher cytokinin concentrations of the order 6-Y,Y-dimethylallylaminopurine > zeatinriboside > zeatin >dihydrozeatinriboside were detected at infection sites of susceptible hosts. By virtue of these cytokinins, infection sites may be acting as metabolic sinks helping proliferation of the pathogen. Existence of translocatory sinks at infection zones was confirmed from autoradiographic studies,where, accumulation of labeled metabolites was prominent at infection sites of susceptible hosts. Upon infection the lower cytokinin levels of resistant hosts decreased further with progress of infection. In the infected resistant hosts the concentrations of zeatin/zeatinriboside were the maximum among the four identified cytokinins. The pathogen is also capable of secreting cytokinins as evident from quantification of cytokinins in culture filtrate extracts using HPLC. Since detached leaves were used in the experiments the increase/decrease of various cytokinin levels may be attributed to pathogen influence. The increase in cytokinin levels in the susceptible host may be aiding the growth of the pathogen on one hand, while the decrease in the infected resistant host may signal the host to activate defenses against a potential pathogen at the early stage of infection.

Plant Regeneration from Hypocotyl and Cotyledon Explant of Tomato (Lycopersicon esculentum Mill.)

Abstract: Three tomato cultivars were used to examine the influence of the genetic background on the regeneration efficiency. White embryonic calli were formed within two weeks of culture. Shoots emerged either directly from the explant or indirectly from the embryonic callus. Multiple adventitious shoots were formed by clonal propagation of somatic embryos in the presence of 2 mg zeatin L-1. The meristematic end of the hypocotyl of the cultivar Pontaroza showed a high regeneration frequency (70.2%) compared with the cotyledonary leaf explant (35.3%). The plants grown in the green house and the regenerants obtained showed a similar peroxidase banding pattern. The combined analysis of variance indicated that the difference in shoot induction between cultivars was highly significant. Shoot induction frequency was 57.2%, 43.5%, and 35.5% for the cultivars UC-97, Pontaroza, and Zuishi, respectively. The regeneration frequency was 50%, 28%, and 20% for the cultivars UC-97, Pontaroza, and Zuishi, respectively. T...

Cytokinin Content and Location in the Leaves of the Wild-type and Transgenic Tobacco Plants

Abstract: Cytokinin content was assayed in the leaves of tobacco ( Nicotiana tabacum L.) plants, nontrans- formed (wild type) and transformed with a genetic construct containing the light-inducible ipt gene, using liquid chromatography followed by mass spectrophotometry and by thin-layer chromatography combined with immu- noenzyme assay. Immunocytological location of phytohormones was investigated after successively treating plant tissue sections with polyclonal antibodies against zeatin riboside, species-specific immunoglobulins labeled with colloid gold, and silver preparation. Cytokinin content in leaves of the transformed plants was higher than in those of wild-type plants. The bottom leaves of the former accumulated zeatin nucleotide. The contents of zeatin and zeatin riboside in the upper leaves exceeded that in the lower leaves both in transformed and wild-type plants. Staining agrees the contents of zeatin and zeatin riboside in the leaves were shown to cor- relate with the intensity of immunostaining of leaf sections. High zeatin content in the bottom leaves of trans- genic plants did not affect the level of immunostaining.

Changes in hormonal balance and meristematic activity in primary root tips on the slowly rotating clinostat and their effect on the development of the rapeseed root system

Abstract: The morphometry of the root system, the meristematic activity and the level of indole-3-acetic acid (IAA), abscisic acid (ABA) and zeatin in the primary root tips of rapeseed seedlings were analyzed as functions of time on a slowly rotating clinostat (1 rpm) or in the vertical controls (1 rpm). The fresh weight of the root system was 30% higher throughout the growth period (25 days) in clinorotated seedlings. Morphometric analysis showed that the increase in biomass on the clinostat was due to greater primary root growth, earlier initiation and greater elongation of the secondary roots, which could be observed even in 5-day-old seedlings. However, after 15 days, the growth of the primary root slowed on the clinostat, whereas secondary roots still grew faster in clinorotated plants than in the controls. At this time, the secondary roots began to be initiated closer to the root tip on the clinostat than in the control. Analysis of the meristematic activity and determination of the levels in IAA, ABA and zeatin in the primary root tips demonstrated that after 5 days on the clinostat, the increased length of the primary root could be the consequence of higher meristematic activity and coincided with an increase in both IAA and ABA concentrations. After 15 days on the clinostat, a marked increase in IAA, ABA and zeatin, which probably reached supraoptimal levels, seems to cause a progressive disturbance of the meristematic cells, inducing a decrease of primary root growth between 15 and 25 days. These modifications in the hormonal balance and the perturbation of the meristematic activity on the clinostat were followed by a loss of apical dominance, which was responsible for the early initiation of secondary roots, the greater elongation of the root system and the emergence of the lateral roots near the tip of the primary root.

Alteration of Hormonal Levels in a Rootless Epiphytic Bromeliad in Different Phenological Phases.

Abstract: Major changes in indole-3-acetic acid (IAA) and cytokinin (CK) levels occur at different phenological phases of Tillandsia recurvata shoots. This epiphytic rootless bromeliad was chosen as suitable material for hormonal analysis because CK synthesis is restricted to the shoots, thus avoiding problems in the interpretation of results caused by translocation and interconversion of CK forms between roots and leaves encountered in plants with both organs. Young plants of T. recurvata have weak apical dominance because side shoots appeared early in development, and branch growth was correlated with a strong increase in the level of zeatin. The flowering phase was characterized by a significant increase in free base CKs, zeatin, and isopentenyladenine compared with the levels found in adult vegetative shoots. In contrast, both free-base CKs declined in the fruiting phenological phase, and the IAA level increased dramatically. It was concluded that in phases characterized by intense organ formation, such as in the juvenile and flowering stages, there was an enhancement of CK content, mainly caused by zeatin, leading to a lower IAA/CK ratio. Higher ratios were correlated with phases that showed no organogenesis, such as adult and fruiting phenologies.

Studies on the plant hormones produced by 5 species of endophytic fungi isolated from medicinal plants (Orchidacea)

Abstract: OBJECTIVE To study the plant hormones produced by 5 species of endophytic fungi isolated from medicinal plants and to illustrate the mechanism on endophytic fungi stimulating the growth of plants. METHODS Extracting plant hormones from mycelia and its culture solution with organic solvent, and detecting them by HPLC. RESULTS One or more plant hormones [GA3 (Gibberellin), IAA (Indoleacetic acid), ABA (Abscisic acid), Z (Zeatin), ZR (Zeatin riboside)] were detected from the mycelia and its culture solution. CONCLUSIONS The plant hormones produced by the endophytic fungi are important materials that may be used to reveal the mechanism of endophytic fungi stimulating the growth of medicinal plants (Orchidacea).

In vitro shoot regeneration of Solanum tuberosum cultivars: interactions of medium composition and leaf, leaflet, and explant position.

Abstract: Shoot regeneration was investigated on explants from different leaves and leaflets of three potato cultivars Posmo, Folva and Oleva. Explants were excised from glasshouse grown plants and grown for 6 days on callus induction medium with indole-3-acetic acid or 2,4-dichlorophenoxyacetic acid. Explants were then transferred to auxin free shoot regeneration medium with gibberellic acid and 6-benzyladenine or zeatin. By using the optimum combinations and concentrations of plant growth regulators and by excision of explants from particular regions of proximal leaflets from newly unfolded leaves, shoot regeneration frequencies of 97.0% were obtained for cv. Posmo and 32.1% for cv. Folva. Shoot regeneration frequency of cv. Oleva was very low and could not be improved by the different treatments.

Hybrid weakness in Phaseolus vulgaris L. I. Disruption of development and hormonal allocation

Abstract: A reduced concentration of cytokinins may cause the abnormal growth and development found in F1 hybrids between Andean and Mesoamerican races of Phaseolus vulgaris L. In this study, concentrations of the transportable cytokinin zeatin riboside (ZR) were measured by ELISA for ZR (cross reactivities dihydrozeatin, 14%, zeatin 7.6%) in roots, stems, and leaves of a Phaseolus Mesoamerican landrace (P. vulgaris L. cv. Redkloud), an Andean landrace (P. vulgaris L. cv. Batt), and their F1 hybrids. Concentrations of ZR in roots and leaves of F1 hybrids were significantly less than that found in roots and leaves of parental cultivars. Approximately 90% of the ZR found in F1 hybrids was found sequestered in the stems, whereas cytokinins of the parental cultivars were distributed throughout the plant (roots: Batt 37%, Redkloud, 44%; stems: Batt 35%, Redkloud 42%; leaves: Batt 28%, Redkloud 14%). These results suggest that abnormal growth and development of F1 hybrids may involve interruption of the regulation of cytokinin allocation, thereby disrupting the root-shoot feedback loop between root-sourced cytokinins and putative shoot-produced factors.

Clonal Propagation of Gmelina arborea Roxb. by In Vitro Culture

Abstract: In vitro propagation technique ofGmelina arborea multipurpose and a fast growing tree species was studied. Nodal segment including axillary bud was used as a explant. They were cultured on MS media containing various concentrations (0–10 mg/l) of BAP alone or in combination with 0.002 mg/l of IBA. Nodal segments showed axillary bud proliferation in almost all media tested. MS media containing 0.22 mg/l of BAP alone and 2 mg/l of BAP in combination with 0.002 mg/l of IBA were effective for inducing multiple shoots and shoot elongation. MS medium supplemented with 0.02 mg/l of NAA and 1 mg/l of IBA gave the best result for rooting. The regenerated plantlets were potted and acclimatized successfully in a growth chamber and then moved to the green house. Adventitious shoots production from stem explants that were taken from regenerated plantletin vitro was also discussed. Stem segments were tested for their morphogenetic potential on MS media with various combinations and concentrations of BAP, zeatin and TDZ. Successfull result was obtained on MS media supplemented with 2 mg/l of BAP and 1 mg/l of zeatin or supplemented with 0.5 mg/l of BAP and 0.5 mg/l of TDZ. The shoots obtained on MS media containing 2 mg/l of BAP and 1 mg/l of zeatin rooted on MS media containing 0.02 mg/l of NAA and 1 mg/l of IBA, and plantlets were successfully obtained.

Efficient callus induction and shoot regeneration by anther culture in male sterile mutants of tomato (Lycopersicon esculentum Mill. cv. First)

Abstract: Anthers of three male sterile mutants of tomato plants and their original cv. First were subjected to several factors which affected callus induction and shoot regeneration. Callus induction capacity was significantly improved by the presence of ms genes which disrupt microsporogenesis at meiosis in the anthers of Fms-2 line. Fms-1 and Fms-3, which block microsporogenesis at microspore and tetrad formation respectively, were inferior to Fms-2 in callus induction. Experiments carried out with the Fms-2 line demonstrated that the developmental stage of the explant was a crucial factor in callus formation and that optimum stage was between pre-meiosis and metaphase I, which corresponds to the stage just after the blockage of microsporogenesis. Callus was efficiently induced from anthers, pretreated at 4°C for 3 days, on MS medium, supplemented with 5.0 mg·liter-1 IAA and 2.5 mg·liter-1 zeatin, under a 16-hr photoperiod. The highest frequency of shoot differentiation was achieved on MS medium, supplemented with 0.2 mg·liter-1 kinetin.