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1.
B. N. S. Murthy N. N. Vettakkorumakankav S. KrishnaRaj J. Odumeru P. K. Saxena 《Plant cell reports》1999,18(7-8):607-613
Several cultivars of hybrid seed geranium (Pelargonium×hortorum Bailey), previously shown to be recalcitrant in culture, produced somatic embryos at high frequency when explants were co-cultivated
with a morphogenesis promoting bacterium. This bacterium was isolated as an in vitro contaminant from cultures of geranium
seedling explants and identified as belonging to the genus Bacillus and species circulans. Co-cultivation of hypocotyl explants with the bacterium promoted somatic embryo formation and improved
both the frequency and quality of somatic embryos. In the cultivar Ringo Rose, the least responsive among the cultivars screened,
the embryogenic response was more than four times that of axenic cultures. Nearly 70% of these embryos converted into plantlets,
while the somatic embryos induced under axenic conditions developed poorly and plantlet formation was inconsistent. Among
the different treatments of bacterial culture tested (autoclaved culture, culture filtrate, sonicated bacterial culture, sonication
of bacterial culture followed by filtration, HPLC fractionation of crude bacterial lysate), only two HPLC fractions promoted
embryogenesis to a marginal degree. Co-cultivation of the explants with bacterium during the first week of induction was crucial
for obtaining high-frequency embryogenesis, indicating the role of bacterial stimuli during the induction process.
Received: 23 June 1998 / Revision received: 20 August 1998 / Accepted: 27 October 1998 相似文献
2.
Somatic embryogenesis in geranium (Pelargonium xhortorum Bailey cv Scarlet Orbit Improved) can be achieved by incubating hypocotyl explants on MS medium supplemented with thidiazuron (TDZ; 10 M for 3 days followed by subculture on medium devoid of any plant growth regulators. The presence of gibberellins (GAs) during both the induction and expression phases of embryogenesis was significantly detrimental to somatic embryo formation on the hypocotyl explants. The addition of the GA-synthesis inhibitors paclobutrazol, uniconazole or ancymidol during the period of growth and differentiation of somatic embryos increased the number of somatic embryos formed on each explant. However, paclobutrazol added during the period of induction had no significant influence on somatic embryo formation. Results suggest that both exogenously supplied as well as endogenous GAs play a role, albeit a negative one, on somatic embryogenesis of geranium.Abbreviations
MS
Murashige and Skoog (1962) medium
-
MSO
basal medium devoid of any plant growth regulator
-
TDZ
N-phenyl-N1,2,3-thidiazol-5-ylurea (thidiazuron) 相似文献
3.
D. P. M. Wilson J. A. Sullivan A. A. Marsolais M. J. Tsujita T. Senaratna 《Plant Cell, Tissue and Organ Culture》1997,47(1):27-32
A number of media constituents including sucrose, ammonium nitrate and plant growth regulators were evaluated in an attempt
to improve somatic embryo production in zonal geranium (Pelargonium ×hortorum) cv. Scarlet Orbit Improved. Somatic embryo production was characterized by the quantity and type of somatic embryo induced
by the treatments. Sucrose at 4% supported the highest number of total somatic embryos while improving the proportion of the
morphologically normal cotyledon-stage somatic embryos. Addition of ammonium nitrate also improved embryo production. With
1.89 mM ammonium nitrate, normal cotyledon-stage embryo development was increased by 53%; the proportion of normal cotyledon-stage
embryos decreased and abnormal embryos with leaves or serrated margins in cotyledons (fringed-shoot type) increased with higher
ammonium nitrate concentrations. The effect of plant growth regulators on somatic embryogenesis indicated that exogenous supply
of indole-3-acetic acid (IAA) at a range of 0.25 to 4 μM failed to promote somatic embryogenesis. In contrast, benzyladenine
(BA) up to 2.0 μM increased the total embryo number and the proportion of desirable cotyledon-stage embryos. There was no
interaction between IAA and BA. Our research has demonstrated that improvement in both quantity and quality of somatic embryos
can be achieved in zonal geranium. 相似文献
4.
Summary Thidiazuron (TDZ) effectively induced somatic embryogenesis in cultured hypocotyl explants of geranium (Pelargonium x hortorum Bailey) during only a 3-day period of induction. The presence of acetylsalicylic acid (ASA) during this period caused a two-fold increase in the number of somatic embryos and enhanced synchronization of embryo development compared to the TDZ treatment alone. Salicylic acid was ineffective in modulating similar embryogenic responses as ASA. The ASA-induced enhancement and synchronization of somatic embryogenesis could possibly be used as an experimental system to study the interplay of growth regulators in somatic embryogenesis.Abbreviations ASA
acetylsalicylic acid
- SA
salicylic acid 相似文献
5.
Jos Van Boxtel Albertus Eskes Marc Berthouly 《In vitro cellular & developmental biology. Plant》1997,33(1):6-12
Summary To improve selection of transgenic Coffea spp. tissue after transformation treatments, the effects of the selective agents chlorsulfuron, glufosinate, glyphosate,
hygromycin, and kanamycin were studied on callus development from leaf explants (from greenhouse-grown plants and somaplants)
and in embryogenic suspension cultures. Studied genotypes were from C. arabica, C. canephora, and the interspecific hybrids Arabusta and Congusta. A culture system based on “direct” somatic embryogenesis from C. canephora leaf explants proved to be more sensitive to selective agents than high frequency somatic embryogenesis from C. arabica or Arabusta leaf explants. With respect to the selective effect, chlorsulfuron and hygromycin provoked strong inhibition
and severe necrosis, whereas glyphosate and kanamycin showed variable inhibition. Glufosinate appeared to efficiently inhibit
growth of both leaf callus and callus suspensions of all genotypes tested without inducing necrosis. These properties may
make the use of glufosinate advantageous in a selective growth system for detection of transformed coffee tissues. 相似文献
6.
Summary The cv Ringo Rose of hybrid seed geranium (Pelargonium x hortorum Bailey), previously shown to be recalcitrant in culture, produced somatic embryos when cotyledonary explants were cultured on regeneration medium containing thidiazuron (TDZ), forchlorfenuron (CPPU), or a combination of indole-3-acetic acid and N6 benzylaminopurine (IAA+BAP). Amendment of the basal medium with TDZ (0.5 M) was the most effective treatment. Addition of amino acids to the medium promoted the growth of somatic embryos. Retention of the proximal region of the cotyledon was crucial for regeneration, but the removal of the distal 1/3 to 1/2 cotyledon had no significant effect on somatic embryogenesis. Cotyledonary explants formed somatic embryos in higher frequency and much earlier than hypocotyl explants cultured on the same medium. The somatic embryos induced on cotyledonary explants were germinated on basal medium. More than 70% of the somatic embryos were converted into plants and transferred to soilAbbreviations BAP
N6-benzylaminopurine
- CPPU
N-(2-chloro-4-pyridyl)-N'-phenylurea (forchlorfenuron)
- IAA
indole-3-acetic acid
- TDZ
N-phenyl-N'-1,2,3,-thiadiazol-5ylurea (thidiazuron) 相似文献
7.
Summary A characteristic phenotype of highly embryogenic explants along with the location of embryogenesis- and transformation-competent
cells/tissues on immature cotyledons of soybean [Glycine max (L.) Merrill.] under hygromycin selection was identified. This highly embryogenic immature cotyledon was characterized with
emergence of somatic embryos and incidence of browning/necrotic tissues along the margins and collapsed tissues in the mid-region
of an explant incubated upwards on the selection medium. The influences of various parameters on induction of somatic embryogenesis
on immature cotyledons following Agrobacterium tumefaciens-mediated transformation and selection were investigated. Using cotyledon explants derived from immature embryos of 5–8 mm
in length, a 1∶1 (v/v; bacterial cells to liquid D40 medium) concentration of bacterial suspension and 4-wk cocultivation
period significantly increased the frequency of transgenic somatic embryos. Whereas, increasing the infection period of explants
or subjecting explants to either wounding or acetosyringone treatments did not increase the frequency of transformation. An
optimal selection regime was identified when inoculated immature cotyledons were incubated on either 10 or 25 mgl−1 hygromycin for a 2-wk period, and then maintained on selection media containing 25 mgl−1 hygromycin in subsequent selection periods. However, somatic embryogenesis was completely inhibited when inoculated immature
cotyledons were incubated on a kanamycin selection medium. These findings clearly demonstrated that the tissue culture protocols
for transformation of soybean should be established under both Agrobacterium and selection conditions. 相似文献
8.
M. J. Hutchinson D. Murr S. Krishnaraj T. Senaratna P. K. Saxena 《In vitro cellular & developmental biology. Plant》1997,33(2):136-141
Summary The accumulation of ethylene in headspace of hypocotyl cultures of geranium (Pelargonium × hortorum Bailey) and its possible role in thidiazuron-mediated somatic embryogenesis was investigated. The action of ethylene as determined
by various ethylene synthesis and action inhibitors was varied. Silver nitrate (AgNo3), aminoethoxyvinylglycine (AVG), and silver thiosulphate (STS) had no significant influence on the embryogenic response,
while 1-methylcyclopropene (1-MCP) applied during the initial 3 d of induction or the expression phase, significantly increased
the number of somatic embryos formed. Thidiazuron-treated tissues accumulated large quantities of ethylene within 6 h of culture,
but the levels decreased after 12 h and reached very low levels after 3 d in culture. In the presence of acetylsalicylic acid
(ASA), the levels of ethylene decreased by 20 to 50% during the first 48 h of culture. Analysis of endogenous auxin, cytokinins,
and abscisic acid (ABA) indicated possible interactions of ethylene with other phytohormones during the induction of somatic
embryos on geranium hypocotyl explants. Thidiazuron (10 μM) increased, while ASA decreased the levels of endogenous auxin, cytokinins, and abscisic acid during this period of induction. 相似文献
9.
Morphoregulatory role of thidiazuron : substitution of auxin and cytokinin requirement for the induction of somatic embryogenesis in geranium hypocotyl cultures 总被引:6,自引:0,他引:6 下载免费PDF全文
Somatic embryogenesis was induced in hypocotyl explants of geranium (Pelargonium × hortorum) cultured on media supplemented with various concentrations of N-phenyl-N′-1,2,3-thiadiazol-5-ylurea (thidiazuron). In less than 2 weeks, somatic embryos were observed in treatments containing levels of thidiazuron (TDZ) ranging from 0.2 to 1.0 micromolar. The use of N6-benzylaminopurine in combination with indole-3-acetic acid also evoked embryogenesis, but the efficiency of somatic embryo production was significantly lower than that obtained with TDZ. Hypocotyl culture for only 2 days on TDZ-supplemented medium before transfer to a basal medium was sufficient for inducing somatic embryogenesis. This distinction between the induction and expression of embryogenesis may provide an experimental system for studying the developmental biology of somatic embryogenesis. Substitution of the auxin-cytokinin requirement for the induction of somatic embryogenesis by TDZ suggests the possibility of a novel mode of its action by modulation of endogenous growth regulators. 相似文献
10.
Procedures have been developed that increase the rate of shoot regeneration of hybrid seed geranium from month-old primary callus cultures. Hybrid geranium callus tissue covered with green nodular structures was initiated by placing shoot tip explants on solidified Murashige & Skoog medium (MS) supplemented with 2.0 mgl-1 zeatin and 1.9 mgl-1 indoleacetic acid. Hybrids Red Orbit, White Orbit and Scarlet Orbit were shown to produce 5–50 shoot primordia per explant when callus was initiated on this medium. Regal geranium callus was initiated by placing leaf explants on MS medium supplemented with 2.0 mgl-1 6-benzylaminopurine and 2.0 mgl-1 naphthaleneacetic acid. Regal geranium cultivars Tiny Tot and Lavender Grand Slam were shown to produce between 2–50 shoot primordia per explant when initiated on the same medium. 相似文献
11.
Piedad Gallego Oscar Hita Nieves Villalobos Ana Dorado Luisa Martin Hilario Guerra 《In vitro cellular & developmental biology. Plant》2001,37(2):199-203
Summary An efficient plant regeneration system employing cotyledons, hypocotyls, petioles and leaves as explants and characterized
by continuous and prolific production of somatic embryos, has been developed with Medicago arborea ssp. arborea. The optimal somatic embryogenic response was obtained using a two-step protocol, where explants were incubated under a 16
h photoperiod for 2 mo. on Murashige and Skoog (MS) medium containing 2,4-dichlorophenoxyacetic acid (2,4-D; 9 μM) and kinetin (9 μM), and followed by transfer to kinetin-free MS medium with 2,4-D (2.25 μM). Removal of the cytokinin and a reduction in the concentration of auxin (2.25 μM) in the second step of culture were critical for enhanced production of somatic embryos. The best explants proved to be cotyledons
and petioles (i.e. a mean of 18.0±0.70 somatic embryos at 3 mo. for petiole culture). Somatic embryos were converted into
normal plantlets (8.0±0.89%) when cultured on basal MS medium with 5 μM indolebutyric acid. No somatic embryos were obtained when thidiazuron was used in the culture media. Using petioles as explants
and N6-benzyladenine (BA), embryogenesis was induced in the second step of culture when BA was removed from the medium and the concentration
of 2,4-D was decreased to 2.25 μM. 相似文献
12.
D. P. M. Wilson J. A. Sullivan A. A. Marsolais M. J. Tsujita T. Senaratna 《Plant Cell, Tissue and Organ Culture》1996,47(1):27-32
A number of media constituents including sucrose, ammonium nitrate and plant growth regulators were evaluated in an attempt to improve somatic embryo production in zonal geranium (Pelargonium ×hortorum) cv. Scarlet Orbit Improved. Somatic embryo production was characterized by the quantity and type of somatic embryo induced by the treatments. Sucrose at 4% supported the highest number of total somatic embryos while improving the proportion of the morphologically normal cotyledon-stage somatic embryos. Addition of ammonium nitrate also improved embryo production. With 1.89 mM ammonium nitrate, normal cotyledon-stage embryo development was increased by 53%; the proportion of normal cotyledon-stage embryos decreased and abnormal embryos with leaves or serrated margins in cotyledons (fringed-shoot type) increased with higher ammonium nitrate concentrations. The effect of plant growth regulators on somatic embryogenesis indicated that exogenous supply of indole-3-acetic acid (IAA) at a range of 0.25 to 4 µM failed to promote somatic embryogenesis. In contrast, benzyladenine (BA) up to 2.0 µM increased the total embryo number and the proportion of desirable cotyledon-stage embryos. There was no interaction between IAA and BA. Our research has demonstrated that improvement in both quantity and quality of somatic embryos can be achieved in zonal geranium. 相似文献
13.
Charlene Chang Ben A. Moll Kathleen B. Evenson Mark J. Guiltinan 《Plant Cell, Tissue and Organ Culture》1996,45(1):61-66
In vitro plantlet regeneration systems for the seed geranium (Pelargonium x hortorum Bailey) using cotyledon, hypocotyl and root explants were optimized by studying the influence of seedling age, growth regulators and excision orientation on organogenesis. Indole-3-acetic acid combined with zeatin yielded the highest rate of shoot production on cotyledon explants (0.2–2 shoots per explant). More shoots were produced on explants cut from the most basal region of cotyledons from 2 to 4-day-old seedlings than from older seedlings or more distal cut sites. Hypocotyl explants produced the highest number of shoots, up to 40 shoots per explant, on indole-3-acetic acid (2.8–5.6 mM) + zeatin (4.6 mM) or thidiazuron (4.5 mM). Maximum shoot formation (0.3–1.4 shoots per explant) on root explants occurred when they were cultured on medium containing zeatin. Regenerated shoots rooted best on a basal medium containing no growth regulators. There were substantial differences among cultivars in shoot formation from each of the explant systems.Abbreviations BA
6-benzylaminopurine
- 2,4-d
2,4-dichlorophenoxyacetic acid
- IAA
indole-3-acetic acid
- NAA
naphthaleneacetic acid
- TDZ
thidiazuron 相似文献
14.
The effect of smoke saturated-water (SSW) on somatic embryogenesis was studied using geranium hypocotyl culture as a model system. Treatment of explants with 10% SSW or the inclusion of SSW with thidiazuron, a compound which induces somatic embryogenesis, enhanced the embryogenic potential of the geranium hypocotyl culture. Prolonged exposure to SSW was detrimental to embryogenesis. The SSW treatment also accelerated the rate of embryo development suggesting a growth regulatory role of SSW. 相似文献
15.
P. Giridhar Vinod Kumar G. A. Ravishankar 《In vitro cellular & developmental biology. Plant》2004,40(6):567-571
Summary A novel protocol has been developed for inducing somatic embryogenesis from leaf cultures of Decalepis hamiltonii. Callus was obtained from leaf sections in Murashige and Skoog (MS) medium supplemented with α-naphthaleneacetic acid (NAA)+N6-benzyladenine (BA) or 2,4-dichlorophenoxyacetic acid (2,4-D)+BA. Nodular embryogenic callus developed from the cut end of
explants on media containing 2,4-D and BA, whereas compact callus developed on media containing NAA and BA. Upon subsequent
transfer of explants with primary callus onto MS media containing zeatin and/or gibberellic acid (GA3) and BA, treatment with zeatin (13.68μM) and BA (10.65 μM) resulted in the induction of the highest number of somatic embryos directly from nodular tissue. The maturation of embryos
took place along with the induction on the same medium. Embryogenic calluses with somatic embryos were subcultured onto MS
basal medium supplemented with 4.56μM zeatin+10.65 μM BA. After 4wk, more extensive differentiation of somatic embryos was observed. The mature embryos developed into complete
plantlets on growth regulator-free MS medium. A distinct feature of this study is the induction of somatic embryogenesis from
leaf explants of Decalepis hamiltonii, which has not been reported previously. By using this protocol, complete plantlets could be regenerated through indirect
somatic embryogenesis or organogenesis from leaf explants in 12–16 wk. 相似文献
16.
Kui Shin Voo Clayton L. Rugh Joe C. Kamalay 《In vitro cellular & developmental biology. Plant》1991,27(3):117-124
Summary We describe a tissue culture procedure for somatic embryogenesis and plantlet regeneration in cotton (Gossypium hirsutum L. cv. Coker 312). Callused explants or individual globular embryos were transferred to basal media to induce somatic embryogenesis.
To determine characteristic early indicators of successful germination and conversion, we identified six types of embryos
that developed on basal media. Two of the six embryo types, designated as tulip-shaped and trumpet-shaped, could undergo conversion
in preliminary tests, whereas the others had little or no developmental potential. Several media treatments designed to enhance
the maturation of globular somatic embryos failed to increase the fraction of embryos which matured to form recoverable types.
In efforts to improve plantlet recovery, tulip-shaped embryos were used in limited trials to contrast the effects of chemical
and physical desiccation treatments on germination and conversion. The selective use of tulip-shaped somatic embryos, coupled
with partial desiccation, seems to have augmented plant recovery. Growth habit, flowering, seed set, and lint production of
most of the regenerated plants were comparable to seed-derived plants grown under the same conditions.
Partial research support was provided by state and federal funds appropriated to the Ohio Agricultural Research and Development
Center, The Ohio State University. 相似文献
17.
The capacity for somatic embryogenesis was studied in lec1, lec2 and fus3 mutants of Arabidopsis thaliana (L.) Heynh. It was found that contrary to the response of wild-type cultures, which produced somatic embryos via an efficient,
direct process (65–94% of responding explants), lec mutants were strongly impaired in their embryogenic response. Cultures of the mutants formed somatic embryos at a low frequency,
ranging from 0.0 to 3.9%. Moreover, somatic embryos were formed from callus tissue through an indirect route in the lec mutants. Total repression of embryogenic potential was observed in double (lec1 lec2, lec1 fus3, lec2 fus3) and triple (fus3 lec1 lec2) mutants. Additionally, mutants were found to exhibit efficient shoot regenerability via organogenesis from root explants.
These results provide evidence that, besides their key role in controlling many different aspects of Arabidopsis zygotic embryogenesis, LEC/FUS genes are also essential for in vitro somatic embryogenesis induction. Furthermore, temporal and spatial patterns of auxin
distribution during somatic embryogenesis induction were analyzed using transgenic Arabidopsis plants expressing GUS driven by the DR5 promoter. Analysis of data indicated auxin accumulation was rapid in all tissues
of the explants of both wild type and the lec2-1 mutant, cultured on somatic embryogenesis induction medium containing 2,4-D. This observation suggests that loss of embryogenic
potential in the lec2 mutant in vitro is not related to the distribution of exogenously applied auxin and LEC genes likely function downstream in auxin-induced somatic embryogenesis. 相似文献
18.
Summary Modes of regeneration from hypocotyl explants were studied in Pelargonium × hortorum ‘Scarlet Orbit,’ and three wild relatives, P. zonale, P. alchemilloides, and P. inquinans, on different cytokinin treatments [1 μM thidiazuron (TDZ), 4 μM TDZ, or 8 μM N6-benzylaminopurine (BA) and 1 μM indole-3-acetic acid (IAA)]. P. × hortorum ‘Scarlet Orbit’ and P. zonale showed similar high numbers of easily detached, embryo-like structures in response to 1 μM TDZ; P. alchemilloides and P. inquinans showed weak embryogenic responses to all treatments. To revisit whether P. × hortorum produces somatic embryos, and to examine modes of regeneration in the wild species, the histology of regenerating structures
on hypocotyl explants in 1 μM TDZ was examined. Both P. × hortorum and P. zonale produced embryo-like structures from single cell derivatives of epidermal cells. Globular-shaped structures transitioned
into heart-shaped structures that had loose attachments to explant surfaces and no vascular connection to the explant. Roots
with direct vascular connections to the rest of the embryo-like structures were never observed; root organogenesis appeared
to be secondary. We propose that P. × hortorum and P. zonale exhibit partial somatic embryogenesis, in which all of the criteria for somatic embryos are met except formation of a root
pole. In both species, explants forming embryo-like structures could also undergo shoot organogenesis, where shoots exhibited
a broad base of attachment to the explant and a vascular connection to vascular nodules within the explant. Epidermally derived
embryo-like structures were not observed in P. alchemilloides or P. inquinans in response to 1 μM TDZ. Shoot organogenesis occurred in P. alchemilloides but not in P. inquinans. 相似文献
19.
This study was initiated to determine whether antibiotic pulse treatments (APT) could effectively eliminate internal infections of ginseng (Panax ginseng) root explants containing vascular tissue, and subsequently have post-treatment effects on changing explant behaviors in callus induction and organogenesis or somatic embryogenesis. For contamination control, a treatment of 40 min with an antibiotic solution consisting of 1000 mg/1 of penicillin-G and 1000 mg/1 of streptomycin immediately following Na-hypochlorite sterilisation significantly decreased contamination rate. Extending treatment time to 2–3 h further lowered the contamination rate to 30–40%. On the other hand, explants treated with antibiotics for 20 min or less were all contaminated. APT also had post-treatment effects; it delayed callus induction for 1–12 months depending on pulse duration and stimulated the generation of more hardand darker looking than fragile- and lighter looking callus. The induced callus proliferated at a depressed rate, increasing subculture intervals from 1 to several weeks, and not until after five subcultures did it fully recover. The regeneration ability of the recovered callus was also affected by APT: the regeneration of adventitious roots was promoted, whereas somatic embryos were not observed.Abbreviations
APT
Antibiotic pulse treatments
-
2,4-D
2,4-dichlorophenoxyacetic acid 相似文献
20.
Summary
In vitro propagation of Quassia amara L. (Simaroubaceae) was attempted using mature and juvenile explants. Attempts to establish in vitro culture using leaf and internode explants from a plant more than 15yr old were unsuccessful due to severe phenolic exudation.
Plant regeneration through direct and indirect somatic embryogenesis was established from cotyledon explants. Murashige and
Skoog (MS) medium with 8.9 μM N6-benzyladenine (BA) and 11.7 μM silver nitrate induced the highest number (mean of 32.4 embryos per cotyledon) of somatic embryos. Direct somatic embryogenesis
as well as callus formation was observed on medium with BA (8.9–13.3 μM). Semi-mature pale green cotyledons were superior for the induction of somatic embryos. Embryos developed from the adaxial
side as well as from the point of excision of the embryonic axis. More embryos were developed on the proximal end compared
to mid and distal regions of the cotyledons. Subculture of callus (developed along with the somatic embryos on medium with
BA alone) onto medium containing 8.9 μM BA and 11.7 μM silver nitrate produced a mean of 17.1 somatic embryos. Primary somatic embryos cultured on MS medium with 8.9 μM BA and 11.7μM silver nitrate produced a mean of 9.4 secondary somatic embryos. Most of the embryos developed up to early cotyledonary stage.
Reduced concentration of BA (2.2 or 4.4 μM) improved maturation and conversion of embryos to plantlets. Ninety percent of the embryos converted to plantlets. The optimized
protocol facilitated recovery of 30 plantlets per cotyledon explant within 80d. Plantlets transferred to small cups were subsequently
transferred to field conditions with a survival rate of 90%. 相似文献