Chemical Factors Controlling Floral Bud Formation of Torenia Stem Segments Cultured in Vitro II. Effects of Growth Regulators

Correlative effects between growth regulators added to a mediumand different physiological states of explants on adventitiousbud formation and flowering were investigated using Toreniastem segments cultured in vitro. Indoleacetic acid stimulatedfloral bud formation and its development in explants taken fromreproductive plants. These stimulative effects were clearlyseen in explants taken from plants in which flower abscissionwas taking place, but insignificant when explants were preparedfrom younger materials. Abscisic acid acted in a reverse wayto auxin, greatly promoting floral bud initiation and floweringof originally vegetative explnts. Zeatin at a concentrationof 1 mg/liter inhibited floral bud formation, and at a low concentrationsit was generally ineffective. However, floral bud formationand flowering of explants taken either from basal parts of stemsor from 18- to 20-week-old plants were promoted by zeatin treatment.The action of gibberellic acid seemed rather indirect: at aconcentration of 0.01 mg/liter, it generally stimulated floralbud formation but at a concentration of 1 mg/liter, it was ofteninhibitory. (Received January 17, 1981; Accepted February 21, 1981)     

Effects of Wounding on Adventitious Bud Formation in Torenia Stem Segments Cultured In Vitro

In in vitro cultured stem segments of Torenia fournieri Lind.,the formation of adventitious buds can be induced when the culturemedium contains cytokinin. When long stem segments (2.0 cm ormore) were cultured with cytokinin, a large number of buds wereformed in the marginal regions, namely, within the limits of0.5 cm from the cut ends of explants, while only a few budswere initiated in the middle part of the explants. If a slightinjury was made transversely with a scalpel in the central partof an explant, a significant increase in the number of budswas noted within the limits of 0.5 cm from the wound site. Whena wounding treatment was given lengthwise to an explant, a largenumber of adventitious buds were formed over the entire surfaceof the explant compared to the control. Excision itself of explantsfrom mother plants and the additional wounding given to theexplants seemed to trigger the induction of adventitious buddifferentiation in Torenia stem segments. These wounding treatmentsdid not affect the uptake into explants and/or the distributionpattern of radioactive benzyladenine applied to the culturemedium. Key words: Torenia fournieri, Adventitious bud formation, Cytokinin, Wounding     

Clonal Fidelity and Variation in Plantain (Musa AAB) Regenerated from Vegetative Stem and Floral Axis Tips in vitro

Recognition of a phenotypically distinct 'French-type' plantain(Musa AAB) designated 'Superplatano' (Superplantain) promptedevaluation of in vitro micropropagation as a means of generatingsufficient numbers of plants for field evaluation in three locationsin Puerto Rico. A multi-faceted study designed to evaluate relationshipsbetween different aseptic culture procedures and morphologicalorigins of primary explants was carried out. Vegetative budsfrom various positions relative to the mother corm (definedby cardinal points on the compass) and explants from the floralaxis of 'Maricongo' (the 'False-Horn', or florally determinatetype 'progenitor' of 'Superplatano'), and 'Superplatano' (a'French-type') were used as starting materials. Responses underfield conditions were studied using a number of parameters includingyield of commercially marketable fruits. We compared four populationsof shoots, each of which derived from at least three differentshoots from within one mat, shoots derived from vegetative andfloral material from the same mat for both 'Maricongo' and 'Superplatano',and shoots derived from a number of floral buds of the sameclone ('Maricongo') all of which were in culture for the samelength of time. 'Superplatano' was stable whether from vegetativecorm or floral bud apex. This shows conclusively that if thestarting point in the micropropagation process is a stable Musaclone, our tissue culture procedure is reliable. Considerablevariation in bunch phenotype was observed, however, in plantsregenerated from ten of 12 shoot and floral meristems startedfrom the 'False-Horn'-type 'Maricongo'. Change from 'False-Horn'-type(determinate) to 'French'-phenotype (indeterminate) was evidentin each of the three locations. Frequency of bunch reversionvaried from 0·4 to 100%, but was confined to individualoriginating stem tips rather than clones. The most dramaticbunch phenotypic change occurred in plants regenerated fromclone 3. All plants regenerated from shoot 3-North bore 100%'French-type' bunches. However, reversion in plants regeneratedfrom shoot 3-West was only 1·8%, and no bunch phenotypicchange was observed in plants from shoot 3-East. Plants regeneratedfrom both shoot and male floral axis tips in 'Maricongo' clone4 also bore 'French-type' bunches. Frequency of bunch reversionfrom shoot 4-East was 0·4% as compared to 2·6%from 4-floral. Bunch reversion occurred at the frequency of2·0% when plants were regenerated from clone 6-floral.No bunch reversion was observed in plants regenerated from asingle shoot tip in clones 1-West and 5-floral. No dwarfismwas encountered in any of the tissue culture-derived plants.We conclude that tissue culture per se plays a very small role,if any, in the direct induction of off-types. Pre-existing characteristicsof the primary explant determines whether products of a multiplicationshow fidelity or not. Our data suggest that 'Maricongo' is achimera and that 'Superplatano' is revertant off-type that resultswhen breakdown of the chimera occurs. Large numbers of stable'Superplatano' were produced from unstable 'Maricongo' and thisaffirms the value of micropropagation for generation of cloneswith desirable bunch phenotype.Copyright 1993, 1999 AcademicPress Musa, plantains, bananas, tissue culture, clonal multiplication, somaclonal variation, phenotype     

Involvement of Calcium in Adventitious Bud Initiation in Torenia Stem Segments

In Torenia stem segments cultured in vitro, active meristematicdivisions are induced in the epidermis by treatment with cytokinin,resulting in the formation of adventitious buds. Applicationof the calcium ionophore A23187 [GenBank] was found to induce meristematicdivisions in the absence of cytokinin. The induction by A23187 [GenBank] was inhibited by simultaneous addition of auxin, but not byanti-cytokinin. A two hour pre-treatment with A23187 [GenBank] was alsoeffective, but only when it was applied to the explants justafter their excision from mother plants. The A23187 [GenBank] -inducedmeristematic zones developed into dome-shaped structures, butnot into complete adventitious buds. Complete elimination ofcalcium from the culture medium caused 50% inhibition of A23187 [GenBank] -and/or cytokinin-induced initiation of meristematic divisions.When the explants were preincubated with EGTA and then culturedon a Ca-free medium containing EGTA, cytokinin failed to inducebud initiation. Similar inhibition was also obtained by lanthanum,a calcium antagonist, by verapamil, a calcium channel inhibitor,and by trifluoperazine and chlorpromazine, calmodulin inhibitors.These results support the idea that adventitious bud initiationinduced by cytokinin in Torenia stem segments may be mediated,at least partially, by an increase in the level of intracellularCa²⁺. ¹Bioscience Research Center, Mitsui Petrochemical IndustriesLtd., Waki-cho, Kuga-gun, Yamaguchi 740, Japan. (Received May 9, 1985; Accepted October 5, 1985)     

Regulation by Abscisic Acid of In Vitro Flower Formation in Torenia Stem Segments

In Torenia stem segments cultured on a defined medium withoutphytohormones, in vitro flower formation was influenced by thephysiological states of the explants. Endogenous contents ofABA, but not those of IAA, were closely correlated with thephysiological states of the explants. Application of ABA (100ng/ml) to the culture medium stimulated flower formation inthe originally vegetative explants which otherwise had littleflower-forming capacity. Thus, endogenous ABA seems to be oneof the factors controlling the flower-forming capacity of Toreniastem segments. The highest rate of flower formation in the stemsegments was obtained when endogenous contents of ABA (whichresulted from both endogenously present and externally appliedABA) in the stem tissues was between 16 and 20 ng/g fresh weight. ¹ Present address: Bioscience Research Center, Mitsui PetrochemicalIndustries Ltd., Waki-cho, Kuga-gun, Yamaguchi 740, Japan. (Received November 22, 1984; Accepted March 1, 1985)     

Transformation and Characterization of Transgenic Plants of Solanum dulcamara L.--Incidence of Transgene Silencing

A transformation system is described for Solanum dulcamara usingthe supervirulentAgrobacterium tumefaciens strain 1065, carryingboth the ß-glucuronidase (gus) and neomycin phosphotransferaseII (npt II) genes adjacent to the right and left T-DNA borders,respectively. Leaf explants were more efficient for the productionof transformed plants compared to stem explants on medium containing50 mg l^-1of kanamycin sulphate. A 1:10 (v:v) dilution of anovernight culture ofAgrobacterium gave optimal transformationin terms of transgenic plant regeneration. From a total of 174kanamycin-resistant plants selected by their antibiotic resistance,16 failed to exhibit GUS activity. Southern analysis revealedthat these GUS-negative transformants originated from threeindependently transformed cell lines. Restriction enzyme analysesshowed that the GUS-negative plants had both the gus and nptII genes integrated into their genome (one plant had a singlecopy of each gene; the other two plants had multiple copies),with major rearrangement of the gus gene occurring in plantswith several copies of the transgene. GUS-negative plants showedleaf malformations, delayed flowering and a reduction in flower,fruit and seed production compared to GUS-positive and non-transformed(control) plants. Although gene silencing of the gus gene occurred,albeit at a low frequency (9.2%), the transformation systemdescribed generates large numbers of phenotypically normal,stably transformed plants. Copyright 2000 Annals of Botany Company Agrobacterium -mediated transformation, gene silencing, Solanum dulcamara L. (Bittersweet, Woody Nightshade), T-DNA truncation, transgene expression     

The Role of Basipetal Auxin Transport in the Positional Control of Abscission Sites Induced in Impatiens sultani Stem Explants

If segments of Impatiens sultani stem are explanted and incubated,separation layers often form across them and lead to abscission.To test the suggested role of auxin concentration in controllingthe position of abscission sites, explants were labelled byapplying [¹⁴C]IAA to the shoot tip 4 h prior to explanting;transport of auxin applied in this way seems to resemble thatof endogenous auxin. During subsequent incubation of explantsfor 20 h, basipetal transport resulted in ¹⁴C accumulating justabove the base of the explants (nearly 80 % in the bottom 4mm of 24 mm explants). In internodal explants that had beenwounded at explanting by incising one side so as to sever avascular bundle, and in nodal explants with the leaf removed,the ¹⁴C also accumulated just above the wound or node to abouttwice the concentration otherwise expected; this accumulationwas probably due to basipetal transport being impeded by vasculardiscontinuity at the wound or node. Accumulation just abovethe base, or above a wound or node, resulted in gradients of¹⁴C concentration (presumably reflecting endogenous auxin concentration)decreasing in the morphologically upward direction at each ofthese three positions where abscission sites tend to occur. Impatiens sultani, abscission, auxin, IAA, node, polarized transport, positional control, separation layer, wounding     

Stem Lesions, Canker and Dieback of Skimmia japonica

Stem lesions, cankers and dieback of shoots were common on bothyoung and mature plants of Skimmia japonica following the exceptionallyhot and dry summer of 1976. Phoma macrostoma var. macrostoma, Phomopsis skimmiae, Fusariumlateritium and a species of Diplodia were regularly isolatedfrom necrotic tissue. P. macrostoma var. macrostoma was isolatedmost frequently and produced more necrosis and larger cankersthan other species in inoculated plants. All four species, however,were regarded as weak parasites only causing substantial damagein drought-stressed plants or when large inocular were implanteddirectly into host tissue. Skimmia japonica, Rutaceae, stem lesions, canker, dieback, fungal parasites     

An Improved Method Involving Hydroponic Culture for the Production of Sexual Hybrids between Dihaploid Solanum tuberosum and Diploid S. microdontum

Dihaploid Solanum tuberosum and diploid S. microdontum plantswere grown in soil and hydroponics under glasshouse and growthroom conditions. A high light intensity was necessary for flowerinduction in both species and the dihaploid flowered only whengrown in hydroponics. Premature berry abscission was retardedby tuber removal and prevented by the addition of indole aceticacid to the nutrient solution. Seeds from prematurely abscisedberries germinated poorly in soil, but germinated almost aswell as those seeds from indole acetic acid-treated plants whenplaced on Murashige and Skoog (1962) based culture medium. Thehybrid plants were intermediate in morphology, compared to theparents, possessed heterotic vigour and were male fertile. Germinatinghybrid seeds on a colchicine-containing medium led to poorlygrowing plants with ploidy chimeras. Hybrid plant ploidy levelswere doubled by regenerating plants from stem/leaf explantson the tuber disc regeneration medium of Jarret et al. (1980). Key words: Solanum tuberosum, S. microdontum, sexual hybridization, hydroponic culture, tissue culture     

Regulation of Stem Abscission and Callus Growth in Shoot Explants of Sweet Orange [Citrus sinensis (L.) Osbeck]

Two-node explants from Sweet Orange cv. St Ives Valencia orangeshoots produced prolific callus and formed secondary abscissionzones within internodes when cultured in vitro with abscisicacid (ABA, 5 µM) or -naphthaleneacetic acid (NAA, 5 µM).Benzyladenine (BA, 1 µm) induced callus but had littleeffect on abscission. Secondary abscission zone formation wasassociated with ABA-induced and auxin-induced ethylene formation.Treatment of explants with inhibitors of ethylene synthesis[aminoethoxyvinyl glycine (AVG), Co²⁺, PO₄^3–] preventedformation of secondary abscission zones but had variable effectson callus formation. Newly made explants contained high concentrationsof endogenous ABA (up to 6000 ng g^–1 f.wt), as measuredby GC/MS/SIM. Long-term subculture of explants (two years) inmedia containing BA (1 µm) led to a reduction in endogenousABA level (40 ng g^–1 f. wt) and to loss of capacity toform extensive callus and secondary abscission zones. Citrus sinensis (L.) Osbeck cv. St Ives Valencia, sweet orange, secondary abscission zones, in vitro, ethylene, endogenous ABA, endogenous IAA     

The Uptake and Utilization of Phosphorus and Nitrogen by Diploid, Tetraploid and Hexaploid Wheats (Triticum spp.)

Twenty genotypes of Triticum and Aegilops wheats including diploid,tetraploid and hexaploid types, were grown under contrastingphosphorus (P) regimes (control and low P) at 15 °C by dayand 10 °C at night. Dry-matter production and phosphorusand nitrogen uptake and distribution were measured on matureplants. Phosphorus efficiency (PE) was considered in terms of yieldper unit of P in the main shoot and concentration of phosphorusin grain (per cent P). In the low-P set, PE, which ranged from110 to 715 mg grain mg^–1 P, increased as the yield perculm and dry-matter partitioning (harvest index) increased,with hexaploid > tetraploid > diploid. In both the controland low-P plants percentage P in grain decreased in the orderdiploids > tetraploids > hexaploid wheats. Grain phosphoruswas highly negatively correlated with the log of grain yield(r = –0.74; –0.88) and the log of harvest index(r = –0.80 and –0.88) for control and low-P plants,respectively. This suggests that future gains in plant harvestindex will cause smaller reductions in grain phosphorus concentrations.But, within either a high or low phosphorus supply, wheats witha given grain harvest index have significantly different grainphosphorus concentrations, and conscious selection for thischaracter is feasible. Low-P plants had similar grain nitrogen concentrations but lowernitrogen harvest indexes than control plants. Aegilops spp., Triticum spp., wheat, yield components, harvest index, polyploidy, evolution, phosphorus efficiency     

Molecular Cytogenetic Analysis of Polyploidization in the Anther Tapetum of Diploid and Autotetraploid Arabidopsis thaliana Plants

Like those of most angiosperms, vegetative tissues of Arabidopsisthaliana undergo high levels of endopolyploidization. One suchtissue is the anther tapetum which plays a role in male sporo-and gametogenesis. The degree of polyploidization of the tapetumvaries from species to species. Although the role of this processis not yet fully understood, it may be linked to functioningof the tapetum, increasing the copy number of genes needed forthe synthesis of specific factors required by developing pollenmother cells (PMCs) and pollen grains. The present study focusedon polyploidization during the development of the tapetum ofArabidopsis thaliana. The aim was to outline the mode of tapetumpolyploidization in this model plant species and to establishan efficient method for analysing ploidy levels in differentiatedcells. The course and degree of tapetum polyploidization inArabidopsis was analysed in interphase nuclei using fluorescencein situ hybridization (FISH) with repetitive DNA (45S rDNA).The stages of development of the tapetum were analysed alongsidemeiosis in PMCs. The majority of tapetal cells undergo two,maximally three, rounds of divisions. Tapetal nuclei have usuallydivided by metaphase I of meiosis of PMCs. The pattern of tapetumpolyploidization was similar in diploid and autotetraploid plantsand is thus not affected by increasing amounts of maternal plantDNA. The tapetum of autotetraploid plants exhibits a higherfrequency of additional division than seen in diploid plants.Copyright 2001 Annals of Botany Company Arabidopsis thaliana, autotetraploid, FISH, rDNA polyploidization, tapetum     

In Vitro Selection for Salt Tolerance in Brassica juncea L. Using Cotyledon Explants, Callus and Cell Suspension Cultures

Salt-tolerant Brassica juncea L. cell lines or plants have beenselected by screening callus pieces, cell suspension culturesand cotyledon explants in vitro on high concentrations of NaCl.Callus-based selection was unsatisfactory, as only two out ofseven isolated clones retained tolerance after 3 months of subcultureon NaCl-free medium. Selections made via plated cell suspensionswere found to be more stable for salt-tolerance. AH selectedtolerant cell lines, however, failed to regenerate plantlets.A third selection method, employing cotyledon explants was basedon their high potential for regenerating multiple shoots. Outof a total of 2620 explants cultured on high salt media, threesurvived, showed sustained callus proliferation and each regeneratedone shoot. The salt-selected shoots withstood the stabilitytest after 3 months of growth and axillary bud multiplicationon NaCl-free medium. While one of these somaclones was morphologicallyabnormal and sterile, the other two could be reared to maturitywith normal seed set. Brassica juncea, tissue culture, in vitro selection, salt-tolerance, plant regeneration     

In Vitro Induction of Haploid, Diploid, and Triploid Androgenic Embryoids and Plantlets in Datura metal L.

Pollen plantlets of Datura metel L. have been successfully rearedin vitro through anther culture on a nutrient medium supplementedwith coconut milk (15 per cent v/v) The early segmentation patternof the proembryos and their subsequent differentiation intoheart, torpedo, and cotyledonary stages were traced. More than100 plantlets were grown to maturity on soil. They grew normallyand produced flowers. Root-tip and leaf-squash preparationsshowed variable numbers of chromosomes in their cells, and thisindicated the occurrence of ploidy plants among the population.Frequency determinations showed the predominant types to bediploid (70 per cent), triploid (24 per cent), and haploid (6per cent). Differences in the morphology of mature plants inregard to floral size, meiotic irregularities in PMCs, formationof giant pollen grains, differential fruitset, somatic mosaicismin respect of chromosome number, and aneuploidy of cells, wererecorded. The origin of diploid and triploid plants is discussed.     

Agrobacterium rhizogenes Mediated Transformation of the Forage Legumes Medicago sativa and Onobrychis viciifolia

Three cultivars of M. sativa and one cultivar of O. viciifoliawere evaluated for their response to inoculation with A. rhizogenesstrain A4T (containing pRiA4b). A cultivar-dependent responsewas observed in M. sativa with 94%, 25%, and 4% of infectedstem explants producing transformed roots in the cultivars Vertus,Regen-S, and Rangelander, respectively. In O. viciifolia cv.Hampshire Giant, an explant-dependent response was observedwith 78% and 50% of seedling cotyledon and hypocotyl explantsresponding, respectively. Leaf explants failed to produce transformedroots. Transformed roots showed plagiotropic and negativelygeotropic growth on hormone-free agar MS medium. Productionof transgenic shoots from O. viciifolia root cultures occurredspontaneously. Recovery of transgenic plants from M. salivacv. Rangelander was achieved by transfer of callus (inducedon UM medium containing 2·0mg dm^–3 2,4-D and 0·25mg dm^–3 kinetin) to MS medium containing 0·5 ingdm^–3 BAP and 0·05 mg dm^–3 NAA. Cultured rootsof both species synthesized opines (agropine and mannopine).Extensive morphological variation was observed in plants ofM. sativa (clone Al) and O. viciifolia (clone A4Tl) establishedin the glasshouse. DNA sequences homologous to TL-DNA and TR-DNAwere present in root clones and regenerated plants. Key words: Agrobacterium rhizogenes, Medicago sativa, Onobrychis viciifolia, transformed roots, transgenic plants     

In Vitro Plantlet Formation in Mangosteen (Garcinia mangostana L.)

Optimum conditions were determined for in vivo growth and multiplicationof Garcinia mangostana L. using explants from aseptically germinatedseedlings and field-grown plants. Proliferating shoots wereobtained from cotyledon segments cultured on modified Murashigeand Skoog's (1962) medium with 6-benzylaminopurine. Juvenileleaf segments produced adventitious buds on Woody Plant Medium(Lloyd and McCown, 1981). Root segments gave few buds. Shoottip, nodal, and internodal explants gave multiple axillary andadventitious buds. Shoots were multiplied by enhanced axillaryand adventitious bud formation. The shoots were rooted withindolebutyric acid treatment. Rooted shoots were readily establishedin vermiculite: sand (1:1) mixture. Garcinia mangostana L., Mangosteen, tissue culture, shoot regeneration, bud development     

Stem Elongation Response to Neighbour Shade in Sprawling and Upright Polygonum Species

Shading by neighbouring plants, which reduces energy for photosynthesisand lowers the ratio of red:far red light, can trigger a stemelongation or ‘overtopping’ response in herbaceousplants. We compared the stem elongation response of two Polygonumspecies in a greenhouse experiment. P. sagittatum, a sprawling,vine-like annual, and P. hydropiperoides, an upright perennial,were grown from seeds at three levels of neighbour shade producedby crowding a cohort of real neighbour plants or adult-sizedfake neighbour plants that provided shade and reduced the red:far-redratio. We hypothesized that the annual would show a more pronouncedelongation response to developing or adult neighbour shade becausevine-like plants are less mechanically constrained to remainupright and self-supporting. Internodes on stems of bothP. sagittatumand P. hydropiperoides increased in length as the amount ofshading by real or fake neighbours increased. P. sagittatumclimbed on adjacent plants, and had longer stems with more nodesthan those of P. hydropiperoides. Although both P. sagittatumand P. hydropiperoides tended to elongate with crowding, thegreater elongation response to both real and fake neighboursshown by the sprawling annual reflects its ability to extendupward into a canopy beyond self-supporting height. Self-supportingP. hydropiperoides can extend upward with, or overtop, cohortneighbours, but might less readily elongate into an extant canopy.In dense stands, P. sagittatum can become structurally dependenton close P. hydropiperoides neighbours. Our results suggestthat the elongation response of P. sagittatum to neighbourscan contribute to structural dependence and could facilitatecoexistence of these species.Copyright 2000 Annals of BotanyCompany Neighbour effects, light variation, red:far-red, plant growth strategy, Polygonum sagittatum, Polygonum hydropiperoides, smartweeds     

Foliage Profile, Size Structure and Stem Diameter-Plant Height Relationship in Crowded Plant Populations

The relationships between vertical foliage profile of an individualplant, competition between individuals, size structure and allocationpattern between stem diameter (D) and plant height (H) wereinvestigated using canopy photosynthesis and two-dimensionalcontinuity equation models including D and H as two independentvariables. Broad-leaved type plants (more foliage mass in theupper layer than in the lower layer of the canopy of an individualwhen grown in isolation) showed curvilinear D-H relationshipand bimodal H distribution, and underwent more asymmetric competitionthan coniferous type plants (more foliage mass in the lowerlayer than in the upper layer of the canopy of an individualwhen grown in isolation) under crowded conditions. Coniferoustype plants showed almost linear D-H relationship (i.e. simpleallometry) and unimodal H distribution, and underwent more symmetriccompetition than broad-leaved type plants under crowded conditions.However, in both the cases D distributions were unimodal. Allocationpatterns between D and H affected these features only a little.These simulation results can explain many actual data alreadypublished. The value of     

Inhibition of Cytokinin-Induced Adventitious Bud Initiation in Torenia Stem Segments by Inhibitors of Serine Proteases

Application of di-isopropyl fluorophosphate (DFP), a highlysensitive inhibitor for serine enzymes, strongly inhibited cytokinin-inducedadventitious bud initiation in Torenia stem segments culturedin vitro. The inhibitory effect was not evident when DFP wasapplied after 3 days of culture. Amount of DFP-binding proteinsremarkably increased in superficial tissues of explants culturedfor 3 and 4 days on a medium containing benzyladenine. At least14 kinds of DFP-binding polypeptides were detected by SDS-polyacrylamidegel electrophoresis and fluorography. DFP-binding to some ofthese polypeptides was inhibited by a prior treatment with phenylmethylsulfonylfluoride and N-p-tosyl-L-lysine chloromethyl ketone. From theseresults, it was suggested that some serine proteases might berelated with biochemical events occurring during the initialstage of adventitious bud differentiation in Torenia stem segments. (Received May 8, 1984; Accepted July 5, 1984)     

Parameters Influencing Stable Transformation of Rice Immature Embryos and Recovery of Transgenic Plants using Electric Discharge Particle Acceleration

Recovery of transgenic rice plants from elite varieties wasreported from the author's laboratory. By using electric dischargeparticle acceleration, recombinant technology was extended tocommercially important japonica and indica rice cultivars notamenable to conventional transformation methodologies. Criticalparameters influencing the recovery of transformed embryogeniccallus from which transgenic plants were recovered have beendefined. Such parameters included the physiological conditionof explants prior to bombardment, DNA and gold particle loadingrates, accelerating voltage, and depth of particle penetration.Selection for recovery of stable transformants was not criticalin this transformation/regeneration system; both selected andnon-selected tissues yielded transformed embryogenic callusand plants at approximately similar frequencies.Copyright 1995,1999 Academic Press Oryza sativa L., transformation parameters, transgenic indica and japonica plants, particle bombardment, ß-glucuronidase