In vitro somatic embryogenesis in callus cultures of Azadirachta indica A. Juss.—a multipurpose tree

Plant regeneration via somatic embryogenesis was achieved in embryogenic callus cultures derived from immature zygotic embryos 40 days after anthesis of Azadirachta indica A. Juss. on semisolid basal Murashige and Skoog (MS) salts and vitamins supplemented with 1.11 µM 6-benzylaminopurine (BA) and 4.52–6.78 µM 2,4-dichlorophenoxyacetic acid (2,4-D). The globular-stage embryos were induced when the callus was transferred to medium with 1.11 µM BA and 0.45 µM 2,4-D. The highest average number of somatic embryos per 200 mg of callus was 152.8 after 8 weeks of culture on the medium. Maturation and germination of the somatic embryos were achieved on half-strength MS salts and vitamins supplemented 0.38–0.94 µM abscisic acid (ABA) and 2% (w/v) sucrose. The maximum percentage (64.2%) of germination was obtained with 0.94 µM ABA within 2 weeks of culture. Somatic embryo-derived plantlets were acclimatized in a greenhouse and subsequently showed normal growth. This efficient protocol will be helpful for propagating elite clones on a mass scale and will also be useful for genetic transformation study.     

Effects of plant growth regulators,carbon sources and pH values on callus induction in Aquilaria malaccensis leaf explants and characteristics of the resultant calli

The endangered tropical tree, Aquilaria malaccensis, produces agarwood for use in fragrance and medicines. Efforts are currently underway to produce valuable agarwood compoundsn tissue culture. The purpose of this study was to develop an optimal growth medium, specifically, the best hormone combination for callus suspension culture. Using nursery-grown A. malaccensis, sterilized leaf explants were first incubated on basic Murashige and Skoog(MS) gel medium containing 15g/L sucrose and at pH 5.7. Different auxin types including 1-naphthaleneacetic acid(NAA), 2,4-dichlorophenoxyacetic acid(2,4-D), and indole-3-butyric acid(IBA), were tested at various concentrations(0.55, 1.1 and 1.65 μM) using the basic medium. Leaf explants were incubated for 30 days in the dark. Callus induced by 1.1 μM NAA had the highest biomass dry weight(DW) of 17.3 mg; however the callus was of a compact type. This auxin concentration was then combined with either 6-benzylaminopurine(BAP) or kinetin at 0.55, 1.1, 2.2 or 3.3 μM to induce growth of friable callus. The 1.1μM NAA + 2.2μM BAP combination produced friable callus with the highest biomass(93.3mg DW). When testing the different carbon sources and pHs, sucrose at 15g/L and pH at 5.7 yielded highest biomasses at 87.7mg and 83 mg DW, respectively. Microscopic observations revealed the arrangement of the friable cells as loosely packed with relatively large cells, while for the compact callus, the cells were small and densely packed. We concluded that MS medium containing 15 g/L sucrose, 1.1 μM NAA + 2.2 μM BAP hormone combination, and a pH of 5.7 was highly effective for inducing friable callus from leaf explants of A. malaccensis for the purpose of establishing cell suspension culture.     

Establishment of an in vitro plant regeneration protocol for Casuarina cunninghamiana Miq. via indirect organogenesis

An in vitro plant regeneration protocol via indirect organogenesis from morphogenetic callus was established for Casuarina cunninghamiana Miq. Effects of plant growth regulator NAA (naphthaleneacetic acid) and BAP (6-benzylaminopurine), sucrose and AgNO₃ on callus induction, adventitious bud differentiation and shoot development were examined. Explants used were epicotyl fragments from 45-day-old seedlings. The largest callus (4.29 mm in diameter) was obtained after 1 month on a basic culture medium consisting of Murashige and Skoog ? macro- and full strength micro- elements, Nitsch and Nitsch vitamins, supplemented with 0.54 μM NAA, 3.30 μM BAP, and 30 g L⁻¹ sucrose. The calli were subcultured in the same medium above for 2 months. They were then cultured for another 2 months for adventitious bud differentiation and shoot development. The highest mean adventitious bud differentiation, number of shoots formed per callus and number of shoots ≥2 cm long per callus (47.50%, 27.38 and 4.75, respectively) were achieved on the above medium modified with NAA at 0.27 μM and supplemented with AgNO₃ 1 mg L⁻¹. Shoots were successfully rooted without plant growth regulator and the rooted plantlets survived and grew normally. This protocol for in vitro plant regeneration provides a tool not only for vegetative propagation but also for plant genetic transformation and gene function studies of C. cunninghamiana.     

Regeneration of <Emphasis Type="Italic">Melia volkensii</Emphasis> Gürke (Meliaceae) through direct somatic embryogenesis

Experiments were conducted to study plant regeneration through direct somatic embryogenesis using mature zygotic embryo and cotyledonary explants from seeds of Melia volkensii stored for <3 and >12 months. Explants were cultured on Murashige and Skoog (MS) medium supplemented with BAP, NAA and 2,4-D (0.5, 1.0 and 2.0 mg l⁻¹) alone, and BAP (0.5, 1.0, 2.0 and 4.0 mg l⁻¹) in combination with 2,4-D or NAA (0.2 and 0.5 mg l⁻¹). After 4 weeks in culture, up to 60% of cotyledonary explants from the seeds stored for <3 months produced direct somatic embryos on BAP (0.5–4.0 mg l⁻¹) in combination with 2,4-D (0.2 mg l⁻¹). The number of somatic embryos ranged from 5 to 14 per explant in BAP (0.5 mg l⁻¹) and 2,4-D (0.2 mg l⁻¹) combination. Only 20% of cotyledonary explants from seeds stored for >12 months produced somatic embryos. Mature zygotic embryos failed to produce any somatic embryos. Subcultures of somatic embryos from cotyledonary explants of seeds stored for <3 months formed clusters of shootlets on semi solid MS and 1/2 MS media. After 6 weeks of subculture on multiplication MS media augmented with BAP (0.5 mg l⁻¹) and IAA (0.2 mg l⁻¹), 70% of the shoot tips formed 4–7 shoots per explant. Up to 33% of the multiplied shoots were rooted in MS medium supplemented with 2.0 mg l⁻¹ IBA. Plantlets developed normally into seedlings in the greenhouse.     

几种作用因子对多年生黑麦草组织培养影响的研究

以多年生黑麦草成熟种子为外植体进行了愈伤组织诱导和分化的研究。结果表明:dicamba替代2,4 D,蔗糖替代麦芽糖可以显著提高愈伤组织诱导率和植株再生率;在一定的浓度范围内(3～9mg·L-12,4 D)2,4 D浓度的升高可明显提高愈伤组织的诱导率,但同时却降低了分化率;在愈伤诱导培养基中同时使用两种生长激素(2,4 D和NAA)的效果要好于单独使用一种生长激素(2,4 D)的效果;水解酪蛋白、脯氨酸和谷氨酰胺浓度的增加并没有促进植株再生率的升高。     

Micropropagation and callus culture of <Emphasis Type="Italic">Saussurea laniceps</Emphasis>, an alpine medicinal plant

Cottonhead windhairdaisy (Saussurea laniceps Hand.-Mazz.) is one of the most famous and important medicinal herbs in China. Illegal collection from wild populations is increasingly threatening the present environment of S. laniceps. Establishment of an efficient method for micropropagation is the best way to change its endangered situation. When mature seeds of S. laniceps were cultured on hormone-free MS medium, plantlets were formed from germinated seeds in 7–10 d. Then 0.5 cm × 0.5 cm leaf explants were transplanted to MS medium supplemented with 1-naphthalene-acetic acid (NAA)/2,4-D and benzyladenine (BA)/KT and callus was achieved 10 d after transfer. Shoot bud regeneration occurred from callus cultured on MS medium supplemented with different growth regulators 20 d after culturing. The regeneration percentages varied with the different components of plant growth regulators. The percent regeneration from callus pretreated at low temperature of 5°C increased significantly compared with those incubated at 23/20°C directly. Optimal regeneration was observed with explants on media supplemented with 1.5 mg&#8226;L^–1 BA plus 0.2 mg&#8226;L^-1 NAA. In the presence of 0.2 mg&#8226;L^–1 NAA in half-strength MS, 78% of the shoots formed roots. Plantlets from explants showed 63% survival after acclimatization.     

Micropropagation of <Emphasis Type="Italic">Eucalyptus grandis</Emphasis> × <Emphasis Type="Italic">E. urophylla</Emphasis> AEC 224 clone

Genetic transformation systems require protocols that allow regenerating transgenic plants from transformed tissues. This study aimed to establish a protocol for indirect organogenesis in leaf explants of a Eucalyptus grandis  ×  E. urophylla AEC 224 clone. During callogenesis stage, several concentrations of NAA and then NAA or 2,4-D combined with TDZ were tested in JADS culture medium for 30 days, followed by subculture of the explants in the regeneration medium, containing 5.0 µM BA and 0.5 µM NAA for another 30 days. In these media, the explant oxidation rate was high (95 %). Thus, in order to reduce oxidation, different culture media were compared: WPM, MS, JADS and modified QL, followed by explant transfer onto regeneration medium. The highest percentage of regeneration and the lowest oxidation rate were achieved on WPM medium. Then, NAA and 2,4-D were tested in combination with TDZ and also TDZ and BA combined with NAA in WPM medium. The most efficient culture media in terms of shoot regeneration were WPM supplemented with 0.25 µM TDZ and 0.1 µM NAA during 30 days for callus induction and then with 5.0 µM BA and 0.5 µM NAA for another 30 days. This protocol yielded a regeneration rate of 43 %, with a low oxidation of tissues. A rooting experiment was conducted using half strength MS medium and comparing three concentrations of IBA (2.46, 4.90 and 7.35 µM). The highest rooting percentage (35 %) was obtained on medium containing 2.46 µM IBA. Once the shoots were rooted, acclimatization in a greenhouse was not challenging and plant survival reached 100 %.     

Using synergistic exogenous phytohormones to enhance somatic embryogenesis from leaf explants of a Eucalyptus grandis clone

Somatic embryogenesis (SE) in Eucalyptus spp. has been limited to germinated seeds, flowers, lignotubers or zygotic embryos. The low yield of somatic embryos from leaf explants has hampered progress, even though leaves offer a more viable source of clonal explants from superior selected genotypes. It was hypothesised that SE from leaf explants could be enhanced through pairing of synergistic exogenous plant growth regulators, such as natural auxins with natural cytokinins. Callus and embryo induction using 2,4-dichlorophenoxyacetic acid (2,4-D), α-naphthalene acetic acid (NAA), indole acetic acid (IAA), and indole butyric acid (IBA), each at either 1.0 or 3.0?mg L^?1, indicated that IAA and IBA favoured significantly higher numbers of embryos compared with 2,4-D or NAA. Hence, IAA and IBA were used for subsequent experiments, combining them (at 1.0?mg L^?1) with either the synthetic cytokinin, kinetin, or the natural cytokinin, trans-zeatin, both at 0.1?mg L?1. The combination of trans-zeatin and either IAA or IBA resulted in a significant increase in SE (e.g. 86 ± 17.2% and 23 ± 3.2% for IAA with trans-zeatin and kinetin, respectively), compared with kinetin, or with these auxins alone. Embryo maturation and plantlet regeneration was highest in those calli that were induced with IAA and trans-zeatin, indicating that maturation was dependent on auxin depletion, based on the stability of the analogue used for induction. For the E. grandis clone under study, the use of synergistic plant growth regulators significantly enhanced SE from leaf explants, thus presenting the opportunity to benefit from the advantages that SE offers over conventional organogenesis.     

Preservation of Juniperus thurifera L.:a rare endangered species in Algeria through in vitro regeneration

Juniperus thurifera L.is an endemic Cupres saceae from the Aure`s Mountains of north eastern Algeria and endangered,in part,due to the scarcity of viable seeds It is threatened by other abiotic factors and the lack of an effective management strategy will increase its risk o extinction.The dearth of information on its in vitro regeneration impedes its application in forest managemen programs.We therefore developed a micropropagation protocol using microcuttings with auxiliary buds.Cuttings were grown on different combinations of media supplemented with plant growth regulators at different concentrations.The highest number of shoots and branches regenerated from original shoots was obtained on Woody Plant Medium(WPM)supplemented with 6-benzylaminopurine(BAP)(0.5 mg L^-1)and 2,4-dichlorophe noxyacetic acid(2,4-D)(0.25 mg L^-1).The best elongation of shoots was achieved with WPM supplemented with0.5 mg L^-1of BAP and 0.25 or 1 mg L^-1 of 2,4-D.On the second subculture,shoots had a higher number of branches than those of the first.The highest rooting rate,38.8%,was obtained with shoots cultured in 1/2 Murashige and Skoog(MS)medium supplemented with 5.0 mg L^-1each of indol-3-butyric(IBA)and naphthalene acetic acid(NAA).Similarly,the highest root numbers and lengths were produced on 1/2 MS medium supplemented with IBA and NAA(5.0 mg L^-1each).During transfer to acclimatization,rates of plant losses of 50% occurred.The second part of the experiment showed that the best shoot callusing was on WPM supplemented with BAP and 2,4-D,with either the combination 0.5+0.25 or 0.25+0.25 mg L^-1.The results of this research provide a starting point for further studies on in vitro regeneration of J.thurifera for the sustainable management of its unique ecosystem in the Mediterranean basin.     

In vitro plant regeneration from cotyledon-derived callus cultures of leguminous tree Gleditsia caspica Desf.

An in vitro regeneration system was developed using organogenic callus derived from in vitro grown cotyledonary explants of Gleditsia caspica Desf., an important leguminous tree. Murashige and Skoog (MS) basal medium augmented with 0.2 g L^?1 myo-inositol and various concentrations of either 2,4-dichlorophenoxyacetic acid (2,4-D), naphthaleneacetic acid, or indole-3-butyric acid (IBA) alone as well as combined with cytokinins was used for callus induction. The highest frequency of organogenic yellowish-white and nodular callus (93 %) was obtained from explants grown on medium supplemented with 13.5 μM 2,4-D and 4.4 μM benzyladenine (BA). The yellowish-white and nodular callus when transferred to MS medium supplemented with BA (2.2–17.7 μM) or kinetin (KT; 2.3–18.8 μM) solely or in combination with 2.3 μM 2,4-D produced several microshoots after 5 weeks culture. The calli cultured on MS medium with 4.4 μM BA singly showed superior growth response and produced both maximum shoot regeneration (94 %) and the highest mean number (4.3) of microshoots per callus. Transfer of regenerated microshoots onto modified MS basal medium fortified with 5.8 μM gibberellic acid and 4.4 μM BA resulted in the maximum number of internodes per shoot and the highest shoot elongation after a period of 6 weeks. Optimum rooting of 90 %, an average 6.1 roots per shoot, and a mean root length of 3.6 cm was observed when half-strength MS medium was supplemented with 9.8 μM IBA and 0.92 μM KT. The regenerated healthy plants with well-developed shoots and roots showed a survival rate of 77 % after acclimatization and transplanting to garden soil for a 10-week hardening period under ex vitro conditions.     

Somatic embryogenesis and plant regeneration inAcanthopanax sciadophylloides

Somatic embryos ofAcanthopanax sciadophylloides Franch. et Sav. were differentiated from both zygotic and somatic embryos and calli, and plants were regenerated from these somatic embryos. A zygotic embryo, enclosed within a small portion of the endosperm, was incubated on Murashige and Skoog (MS) media supplemented with various combinations (range 0–10.0 mg/l) of 6-benzylaminopurine (BAP) and 2,4-dichlorophenoxyacetic acid (2,4-D). After 4 months, swelling of the zygotic embryos and callus formation was observed. When the swollen embryos were transferred to MS medium supplemented with 0.5 mg/l of 2,4-D, somatic embryos were formed in one to two months. After subculture on the same medium, new embryos were differentiated from various parts of the older somatic embryos. The calli were cultured on medium supplemented with 2.0 mg/l of 2,4-D and BAP for three weeks. Proliferated calli were transferred to medium supplemented with 1.0 mg/l of 2,4-D and BAP. Somatic embryos were differentiated from the calli within one to two months. Somatic embryos were germinated on half-strength MS medium without plant growth regulators and the plantlets were grown in soil. A part of this paper was presented at the 106th Annual Meeting of the Japanese Forestry Society (1995) & First Asia-Pacific Symposium on Forest Tree Genetic Improvement (Beijing).     

优系欧李茎叶愈伤组织诱导与植株再生

以欧李春季萌发的幼茎、叶片为外植体诱导愈伤组织的产生,结果表明:叶片愈伤组织培养以改良MS为基本培养基,附加NAA 1.0 mg/L IBA 0.5 mg/L BA 0.2 mg/L效果较好;茎段愈伤组织培养以改良MS附加2,4-D0.5 mg/L NAA 0.3 mg/L BA 0.15 mg/L诱导愈伤组织效果好;愈伤组织再诱导不定芽以1/3 MS附加BA2.0 mg/L IBA 0.01 mg/L培养基效果佳。     

Induction of somatic embryogenesis and analysis of genetic fidelity of in vitro<Emphasis Type="Italic">-</Emphasis>derived plantlets of <Emphasis Type="Italic">Bambusa nutans</Emphasis> Wall., using AFLP markers

Bambusa nutans Wall., is an evergreen, perennial, and multipurpose bamboo having strong culms, which are largely used for construction, scaffolding, craft purposes, pulp, and paper industry. Multiple shoots from nodal segments (3–4 cm) of young branches of mature culms were established in Murashige and Skoog (1962) (MS) medium supplemented with various concentrations of 6-benzylaminopurine (BAP) (1.0–6.0 mg l⁻¹) or in combination with α-naphthaleneacetic acid (NAA) (0.5–1.0 mg l⁻¹) or kinetin (Kn) (1.0–2.0 mg l⁻¹). February–March and December were found to be the best seasons for culture establishments. Maximum shoots were achieved on MS medium fortified with BAP (2.0 mg l⁻¹). Embryogenic callus (slightly greenish compact, globular, and slow growing) was initiated from the base of severed sprouted buds in 2–3 subsequent subcultures on MS medium supplemented with 2,4-dichlorophenoxy acetic acid (2,4-D) (5.0 mg l⁻¹) under dark incubations. Maturation and germination of well-organized somatic embryos was achieved on MS medium containing BAP and 2,4-D (1.0 mg l⁻¹ each) with 20.0 mg l⁻¹ ascorbic acid. Full-strength MS medium supplemented with 2% glucose favored further development of proliferated somatic embryos into plantlets. Genetic variations of field-established B. nutans plants regenerated through tissue cultures were assessed by amplified fragment length polymorphism (AFLP) analysis using 6 primer combinations. Four hundred and seven scorable fragments were amplified, of which 402 (98.8%) have recorded conservation at various morphogenetic stages leading to plantlets regeneration, therefore, revealed a high level of genetic stability.     

Plantlet regeneration from leaf protoplasts ofPopulus euphratica

Protoplasts were isolated from the leaves of sterile plants ofPopulus euphratica Oliv. by using 1% Cellulase “Onozuka” RS and 0.25% Pectolyase Y-23 in 0.6m of mannitol solution. Protoplasts were cultured in modified Murashige and Skoog's (MS) medium which contained no ammonium ions but was supplemented with BAP (6-benzylaminopurine), 2,4-D (2,4- dichlorophenoxy-acetic acid), and 1% sucrose at the cell density of 9×10⁴/ml. Cell divisions occurred in every culture medium, especially in the medium containing 0.5 mg/l of BAP and 0.1 mg/l of 2,4-D, in which callus was successfully induced by successive culture through cell cluster formation. Shoots were regenerated from the callus, and their growth was enhanced on 1/2 MS medium containing 0.8 mg/l of BAP. Finally, shoots were rooted and plantlets were regenerated on 1/2 MS medium without a hormone. A part of this paper was presented at the 106th Annual Meeting of the Jpn. For. Soc. (1995).     

Shoot proliferation and callus regeneration from nodular buds of Drepanostachyum luodianense

This research reports on an efficient shoot proliferation and callus regeneration system for bamboo.Young, semi-lignified branches with one lateral bud from Drepanostachyum luodianense(Yi et R. S. Wang) Keng f.were used as explants. Disinfection with 0.1% HgCl_2 for 8 min was the optimum treatment and the best medium for bud initiation was Murashige and Skoog(MS) medium containing 3.0 mg L~(-1)6-benzyladenine(BA). Multiple shoots were induced from nodal shoot segments on MS medium containing 5.0 mg L~(-1) BA, 0.5 mg L~(-1) kinetin(Kin), and 1.0 mg L~(-1) naphthaleneacetic acid(NAA). The highest frequency of callus formation(65.6%) was on MS medium containing 4.0 mg L~(-1)2,4-dichlorophenoxyacetic acid(2, 4-D), 0.5 mg L~(-1) NAA, and 0.1 mg L~(-1) thidiazuron(TDZ). The optimum medium for callus proliferation was MS medium with 4 mg L~(-1)2,4-D, 0.5 mg L~(-1) TDZ and 0.5 mg L~(-1) NAA, and the optimum hormone combination was 4 mg L~(-1) BA ? 0.5 mg L~(-1) NAA for callus redifferentiation(up to 85.6%). A 100% rooting was achieved on MS medium supplemented with 2.0 mg L~(-1) NAA and 0.5 mg L~(-1)3-indole butyric acid(IBA). Rooted plantlets were acclimatized in a greenhouse in humus soil ? perlite(1:1) substrate. These micropropagated callus induction and regeneration systems for bamboo will be useful for genetic engineering and multiplication.     

In vitro propagation of Acacia sinuata (Lour.) Merr. via cotyledonary nodes

Acacia sinuata is a valuable multipurpose tree in Southern India. The tree is over exploited, but its regeneration rate in natural habitat is low. Therefore, it is important to study if it can be regenerated through in vitro micro-propagation. Cotyledonary node and shoot-tip explants excised from 15 day-old in vitro grown seedlings were used to initiate cultures. Maximum number of shoots was induced from cotyledonary node explants on Murashige and Skoog's (MS) medium containing6.66 µM 6-benzylamino purine (BAP) and 4.65µM kinetin (Kn). Subculturing was done in the fresh medium of same composition. The number of shoots formed was comparatively greater in the first subculture. Maximum shoot elongation was achieved (5.5 cm)when subcultured on MS medium supplemented with 1.75 µMgibberellic acid (GA₃). In vitro regenerated shoots produced roots when transferred to half strength MS medium supplemented with 7.36 µM indolebutyric acid (IBA). From each cotyledonarynode 30 shoots were obtained within 90 days after two subcultures. The success rate of establishing the rooted plantlets in the field was 55%.This revised version was published online in November 2005 with corrections to the Cover Date.     

Micropropagation of Vitex negundo L. and Random Amplified Polymorphic DNA Analysis of Micropropagated Plants

A micropropagation protocol was established for a medicinal plant Vitex negundo. Genetic stability of micropropagated plants was investigated. Multiple shoots were induced from nodal explants cultured on Murashige and Skoog (MS) medium with 0.53 μM naphthalene acetic acid (NAA) and 11.0 μM benzyl aminopurine (BAP) along with additives (ascorbic acid, 283.9 μM; citric acid, 130.1 μM; and arginine, 143.6 μM). Shoots were further multiplied by repeated transfer of the mother explant. The shoots were further multiplied on MS medium + 0.57 μM indole-3-acetic acid (IAA) and 6.6 μM BAP. The micropropagated shoots were pulse treated with 122.5 μM indole-3-butyric acid (IBA), in liquid MS medium and then transferred to autoclaved soilrite. These rooted ex vitro. Shoots were also rooted in vitro on a half-strength MS medium + 2.45 μM IBA. The survival rate of in vitro rooted plantlets was poor during hardening compared to ex vitro rooted plantlets. About 95% of the ex vitro rooted, hardened plantlets survived in the field. Genetic stability of micropropagated plants was tested by using 25 random amplified polymorphic DNA primers. The cloned plants exhibited no variation in banding pattern in comparison with the mother plant.     

粗皮桉再生系统的研究(英文)

该研究在国内外首次报导了粗皮桉的再生系统 .利用粗皮桉的外植体通过两种不同的再生途径建立了高效的再生系统 .首先探讨了粗皮桉的下胚轴和子叶的体细胞胚胎发生 .研究发现 ,下胚轴和子叶在含有 2 ,4 D(添加有BA或激动素 )的培养基上可诱导三种典型不同的愈伤类型 .其中 ,来源于下胚轴的颗粒状的、松脆的胚性愈伤在分化培养基上可获得高频率的再生小植株 .讨论了不同类型的愈伤组织和其对应的分化再生率之间的关系 .此外 ,本研究探讨了来源于粗皮桉的下胚轴、子叶及成熟叶片在添加有一系列BA和NAA的不同浓度组合的B5培养基上的器官发生途径 ,三种不同的外植体在不同的再生培养基上的最高再生频率不同 ,其中成熟叶片、子叶和下胚轴的最高再生率逐渐提高 ,分别为 4 1 6 7%、6 6 6 7%和 83 33% .该文还讨论了两种不同再生系统的意义     

Efficient in vitro regeneration of <Emphasis Type="Italic">Leucaena leucocephala</Emphasis> using immature zygotic embryos as explants

A method for efficient in vitro regeneration of Leucaena leucocephala cv. K636 was developed using immature zygotic embryos as the explant. Multiple shoot induction was achieved by culturing the explants on half-strength Murashige and Skoog (MS) medium supplemented with thidiazuron (TDZ) (0.03 to 1.5 μM). The maximum number of shoots per explants was achieved in 0.26 μM TDZ-supplemented media. TDZ concentration significantly influenced the induction of multiple shoots as well as the shoot-length. TDZ at 0.35 μM or higher concentrations resulted in abnormal stunted shoots. Full-strength MS media devoid of any plant growth regulator were used for shoot elongation. In vitro root induction was achieved in half-strength MS media supplemented either with 0.54 μM 1-naphthaleneacetic acid (NAA) or with 14.76 μM indole-3-butyric acid (IBA) in combination with 0.23 μM kinetin (Kn). Media supplemented with 14.76 μM IBA in combination with 0.23 μM Kn induced twofold–threefold more roots than media supplemented with 0.54 μM NAA. However, the average root length was lower in 14.76 μM IBA in combination with 0.23 μM Kn than in 0.54 μM NAA. Regenerated plants were maintained under normal condition after hardening. Plants, which were rooted on media supplemented with 14.76 μM IBA in combination with 0.23 μM Kn showed higher survival rate during hardening than those rooted on 0.54 μM NAA supplemented media.     

火炬松胚性愈伤组织诱导和植株再生的研究

火炬松胚性愈伤组织诱导和植株再生的研究唐巍欧阳藩（中国科学院化工冶金研究所生化工程国家重点实验室北京１０００８０）郭仲琛（中国科学院植物研究所北京１０００９３关键词火炬松,体细胞胚胎发生,植株再生本文于１９９６年１０月２８日收到。国家“８６３”资...