Plantlet Formation Research Articles

Histological studies of cellular differentiation during somatic embryogenesis of coconut plumule-derived calli

<div><table cellspacing="0" cellpadding="0" align="center"><tbody><tr><td align="left" valign="top"><p>Since coconut is one of the most recalcitrant species to generate <em>in vitro</em>, it is necessary to study in detail about the cellular changes that occur during somatic embryogenesis to enhance our knowledge about this phenomenon. In the present study, coconut plumular tissues, the shoot meristem including leaf primordia, were used as explants for <em>in vitro </em>regeneration studies. Histological studies were carried out in different stages of plumule culture. No noticeable growth was observed in 15 days old cultures. After 30 days, meristematic cells could be identified. Abundance of meristematic cells, foremost to the development of callus structures, was observed after 45 days. After 75 days, globular friable calli were formed and histological studies revealed the presence of meristematic centers which eventually formed somatic embryos. The histological study of matured somatic embryos formed after 120 days of callus initiation showed a clear meristematic zone of parenchyma cells, surrounded by vascular bundles. Histological studies, carried out for certain abnormalities like compact calli, abnormal somatic embryoids with rudimentary shoots and multiplied roots, revealed the presence of intact cotyledonary leaves which seemed to inhibit the apical meristem development of somatic embryoids. The presence of vascular bundles in the early stages of callus formation might lead to the direct formation of meristemoids. These results could aid future studies leading to enhanced control of the somatic embryogenic process and greater efficiency of somatic embryo and plantlet formation in coconut.</p></td></tr></tbody></table></div>

Reproduction at the extremes: pseudovivipary, hybridization and genetic mosaicism inPosidonia australis(Posidoniaceae)

Organisms occupying the edges of natural geographical ranges usually survive at the extreme limits of their innate physiological tolerances. Extreme and prolonged fluctuations in environmental conditions, often associated with climate change and exacerbated at species' geographical range edges, are known to trigger alternative responses in reproduction. This study reports the first observations of adventitious inflorescence-derived plantlet formation in the marine angiosperm Posidonia australis, growing at the northern range edge (upper thermal and salinity tolerance) in Shark Bay, Western Australia. These novel plantlets are described and a combination of microsatellite DNA markers and flow cytometry is used to determine their origin. Polymorphic microsatellite DNA markers were used to generate multilocus genotypes to determine the origin of the adventitious inflorescence-derived plantlets. Ploidy and genome size were estimated using flow cytometry. All adventitious plantlets were genetically identical to the maternal plant and were therefore the product of a novel pseudoviviparous reproductive event. It was found that 87 % of the multilocus genotypes contained three alleles in at least one locus. Ploidy was identical in all sampled plants. The genome size (2 C value) for samples from Shark Bay and from a separate site much further south was not significantly different, implying they are the same ploidy level and ruling out a complete genome duplication (polyploidy). Survival at range edges often sees the development of novel responses in the struggle for survival and reproduction. This study documents a physiological response at the trailing edge, whereby reproductive strategy can adapt to fluctuating conditions and suggests that the lower-than-usual water temperature triggered unfertilized inflorescences to 'switch' to growing plantlets that were adventitious clones of their maternal parent. This may have important long-term implications as both genetic and ecological constraints may limit the ability to adapt or range-shift; this seagrass meadow in Shark Bay already has low genetic diversity, no sexual reproduction and no seedling recruitment.

Influence of Plant Growth Regulators on In Vitro Shoot Multiplication and Plantlet Formation in Cassia angustifolia Vahl

An effective and improved plant regeneration system was successfully developed using shoot tip explants taken from a two years old mature plant of Cassia angustifolia. The effect of different cytokinins, [6-benzyladenine (BA), Kinetin (Kin) and thidiazuron (TDZ)] at different concentrations (0.5-10 µM) were evaluated as augmented with Murashige and Skoog (MS 1962) medium. Among all the cytokinins tested, TDZ (5.0 µM) was optimum in inducing multiple shoots as compared to BA and Kin. The rate of shoot multiplication was increased when optimal concentration (5.0 µM) of BA and Kin was tested with different concentration (0.1-1.0 µM) of Indole-3- acetic acid (IAA). Among all the combinations tested, the maximum rate of shoot multiplication was obtained on MS medium supplemented with 5.0 µM BA and 0.5 µM IAA. The number of the shoots and shoot length developed in TDZ was increased when transferred to MS medium devoid of TDZ. After every subculture, rate of the shoot multiplication and shoot length showed increment and continued even after fifth subculture without any decline rate. In vitro rooting in regenerated shoots were best obtained in half-strength MS medium supplemented with 2.0 µM indole-3- butyric acid (IBA). Plantlets with well-developed shoot and roots were successfully hardened off in earthen pots containing garden soil and grown in greenhouse with 80% survival rate.

Plant Growth-Promoting Rhizobacteria Stimulate Vegetative Growth and Asexual Reproduction of Kalanchoe daigremontiana.

Certain bacterial species associate with plant roots in soil. The plant growth-promoting rhizobacteria (PGPR) stimulate plant growth and yield in greenhouse and field. Here, we examined whether application of known bacilli PGPR strains stimulated growth and asexual reproduction in the succulent plant Kalanchoe daigremontiana. Four PGPR strains B. amyloliquefaciens IN937a, B. cereus BS107, B. pumilus INR7, and B. subtilis GB03 were applied to young plantlets by soil-drenching, and plant growth and development was monitored for three months. Aerial growth was significantly stimulated in PGPR-inoculated plants, which was observed as increases in plant height, shoot weight, and stem width. The stimulated growth influenced plant development by increasing the total number of leaves per plant. Treatment with bacilli also increased the total root biomass compared with that of control plants, and led to a 2-fold increase in asexual reproduction and plantlet formation on the leaf. Collectively, our results firstly demonstrate that Bacillus spp. promote vegetative development of K. daigremontiana, and the enhanced growth stimulates asexual reproduction and plantlet formation.

Propagación in vitro y aclimatización de Euchile mariae (Ames) Withner (Orchidaceae)

Orchid micropropagation of species Euchile mariae was achieved from the in vitro culture of protocorms sections, obtained from the germination of seeds. The top and bottom protocorms sections, used as explants, were cultivated in modified MS culture medium, added with different concentrations of α-naph- thaleneacetic acid (NAA) and 6-benzylaminopurine (BA). The morphogenetic response obtained of both types of explants, was the formation of protocorm like bodies (PLB’s), that gave place to the formation of new plantlets. Of two tested explants the biggest formation of PLB’s was obtained from the bottom proto- corms sections. The acclimatization of the plantlets was successful, with a 100% percent survival. Plant cell tissue culture represents a useful alternative for the study, conservation and massive propagation of this and other endangered species.

Adquisición de competencia para la micropagación de Stanhopea tigrina, Laelia anceps, Epidendrum veroscriptum y Cattleya x Esbetts (Orchidaceae)

Regeneration protocols were established from the in vitro culture of protocormos of Stanhopea tigrina, Epidendrum veroscriptum, Laelia anceps and Cattleya x esbetts using the Murashige and Skoog culture medium added with different concentrations of N6-benzyladenine (BA) (0, 1, 3, y 5 mg/l) y 2,4 dichlorofenoxiacetic acid (2,4-D). The regeneration and formation of new plantlets was achieved by multiple shoot and also through protocorm like bodies (PLBs). For each species the best concentration of growth regulator, as well as the time of acquisition of competence for the highest shoot formation and/or PLBs were deter- mined. As far as we know there are no reports with reference to the acquisition of competence within the Orchidaceae family that allow the production of many individuals within the shortest time and reducing the financial cost. This could form the base that covers their commercial demand and also contribute to the con- servation and sustainable use of mainly wild species.

Production of chrysanthemum synthetic seeds under non-aseptic conditions for direct transfer to commercial greenhouses

A novel protocol for both production and sowing of chrysanthemum synthetic seeds in non-aseptic conditions for large-scale commercialization was successfully established. Effects of the availability of organic compounds, namely MS vitamins and sucrose, inside and outside gelling matrix on the microbial contaminations, plantlet formation and subsequent growth were investigated. Results showed that the presence of organic compounds, either in gelling matrix alone or in both gelling matrix and commercial substrate, caused microbial contaminations in all synthetic seeds and complete inhibition in regrowth. In contrast, the absence of organic compounds in both non-sterile gelling matrix and substrate resulted in 70 % plantlet formation after 6 weeks of sowing. However, organic compounds absent in gelling matrix but present in substrate induced lower plantlet formation frequency (34 %) after 6-week sowing. The removal of organic compounds from both gelling matrix and substrate, in comparison with the removal from only gelling matrix, also stimulated the formation of plantlets having more leaves, longer shoots and roots, and greater fresh and dry biomass accumulation, but equal leaf area, chlorophyll content, and number of nodes and roots. These findings suggest that the eradication of all organic compositions is a prerequisite for practical application of encapsulation technology to the mass production of chrysanthemum plants.

Embryogenic potential of immature zygotic embryos of Passiflora: a new advance for in vitro propagation without plant growth regulators

In vitro strategies for Passiflora have been developed owing to its economic and ecological importance. However, plantlet regeneration through somatic embryogenesis has presented some problems, such as the reproducibility of the protocol and formation of abnormal embryos and plantlets. Thus, this study aimed to establish a protocol exploring the embryogenic potential of immature zygotic embryos (IZE) of the wild species Passiflora miniata Vanderpl. and Passiflora speciosa Gardn. Friable calli, which formed on the abaxial surface of the cotyledons, yielded globular, heart-shaped, torpedo and cotyledonary somatic embryos, characterising the embryogenic response as asynchronous. A high percentage of normal regenerants (90 %) was obtained from IZE in media lacking 2,4-dichlorophenoxyacetic acid (2,4-D) in comparison to the value of normal plantlets (60 %) regenerated from mature zygotic embryos inoculated in media with 2,4-D. This result demonstrates that IZE of P. miniata and P. speciosa possess sufficient levels of endogenous phytohormones to trigger a high rate of indirect somatic embryogenesis. All regenerated plantlets had the same genome size and chromosome number as the explant donor plants. Therefore, the indirect embryogenic pathway, employing IZE inoculated into media free of growth regulators, did not cause changes in the karyotype and morphology. Based on these results, IZE should be considered as explant for the establishment of somatic embryogenesis in other species. Besides, a new, reliable and relatively rapid protocol to recover plantlets of P. miniata and P. speciosa yielded several plants, which were acclimatised and used for ornamental purposes and breeding programs, and for reintroduction into biological reserves.

In vitro propagation and reintroduction of the endangered Renanthera imschootiana Rolfe.

Renanthera imschootiana Rolfe is an endangered tropical epiphytic orchid that is threatened with extinction due to over-collection and the loss of suitable habitats. In vitro propagation is a useful way to mass produce plants for re-establishment in the wild and for commercial propagation. Seeds collected 150 days after pollination (DAP) were the optimum stage for in vitro culture. Seed germination reached 93.1% on quarter-strength MS (i.e., MS containing a quarter of macro- and micronutrients) medium containing 0.5 mg l−1 α-naphthaleneacetic acid (NAA), 20% coconut water (CW), 1.0 g l−1 peptone, 10 g l−1 sucrose and 1.0 g l−1 activated charcoal (AC). Quarter-strength MS medium supplemented with 1.0 mg l−1 BA, 0.5 mg l−1 NAA, 1.0 g l−1 peptone, 10 g l−1 sucrose and 20% CW was suitable for the sub-culture of protocorm-like bodies (PLBs) in which the PLB proliferation ratio was 2.88. Quarter-strength MS medium containing 1.0 mg l−1 NAA, 1.0 g l−1 peptone, 100 g l−1 banana homogenate (BH), and 1.0 g l−1 AC was suitable for plantlet formation and 95.67% of plantlets developed from PLBs within 60 days of culture. Hyponex N016 medium supplemented with 0.5 mg l−1 NAA, 1.0 g l−1 peptone, 20 g l−1 sucrose, 150 g l−1 BH, and 1.0 g l−1 AC was suitable for the in vitro growth of plantlets about 2-cm in height. Plantlets 3-cm in height or taller were transplanted to Chilean sphagnum moss, and 95% of plantlets survived after 60 days in a greenhouse. Three hundred transplanted of seedlings 360-days old were reintroduced into three natural habitats. Highest percentage survival (79.67%) was observed in Yuanjiang Nature Reserve two years after reintroduction, followed by Huolu Mountain forest park (71.33%). This protocol is an efficient means for the large-scale propagation and in vitro and in vivo germplasm conservation of R. imschootiana.

Optimized In Vitro Plant Regeneration of the Biodiesel Plant Jatropha curcas L.: The Effects of Using Seeds at Different Stages of Maturity As Starting Materials

Jatropha curcas L. is an important biofuel plant that can be regenerated in vitro using seeds. The fruits of J. curcas do not reach maturity at the same time although they are on the same bunch. This study was undertaken to evaluate the effect of seeds, from fruits at different stages of maturity, on in vitro plantlet formation. Callus was induced on Murashige and Skoog medium using different concentrations of 2,4 dichlorophenoxyacetic acid (2,4-D) and 6 benzylaminopurine (BAP). 2,4D at a concentration of 3.0 mg/L and BAP at 1.0 mg/L were found to be optimum for callus formation. In vitro plantlets obtained on BAP were smaller with thicker hypocotyl and thicker roots. On the other hand, seeds from mature fruits gave better results for in vitro plantlet regeneration on 1.0 mg/L BAP without any rooting medium. A combination of sand and soil were used for acclimatization. Best results were obtained when sand and soil were used in equal amounts. Results also showed that seed maturity is an important factor for in vitro plant regeneration of J. curcas and that root formation in vitro does not require additional plant growth regulator substance.

Origination of asexual plantlets in three species of Crassulaceae.

During asexual plant reproduction, cells from different organs can be reprogrammed to produce new individuals, a process that requires the coordination of cell cycle reactivation with the acquisition of other cellular morphological characteristics. However, the factors that influence the variety of asexual reproduction have not yet been determined. Here, we report on plantlet formation in Kalanchoe daigremontiana, Graptopetalum paraguayense, and Crassula portulacea (Crassulaceae) and analyse the effect of initiating cells on asexual reproduction in these three species. Additionally, the roles of WUSCHEL (WUS) and CUP-SHAPED COTYLEDON 1 (CUC1) in the asexual reproduction of these species were analysed through qRT-PCR. Our results indicated that pre-existing stem cell-like cells at the sites of asexual reproduction were responsible for the formation of plantlets. These cells were arrested in different phases of the cell cycle and showed different cell morphological characteristics and cell counts. The accumulation of auxin and cytokinin at the sites of asexual plantlet formation indicated their important functions, particularly for cell cycle reactivation. These differences may influence the pattern and complexity of asexual reproduction in these Crassulaceae species. Additionally, the dynamic expression levels of CUC1 and WUS may indicate that CUC1 functions in the formation of callus and shoot meristems; whereas, WUS was only associated with shoot induction.

Influence of osmotic stress, physicochemical factors and nitrogen supplements on embryogenesis and plantlet formation in Guizotia abyssinica Cass. (Niger)

An efficient protocol for somatic embryogenesis was developed for the edible oilseed crop Guizotia abyssinica Cass. (cv. IGP 76). Induction and proliferation of callus was achieved from cotyledonary explants on MS medium amended with 1.5 mg l−1 6-benzyladenine (BA) and 0.5 mg l−1 naphthalene acetic acid (NAA). Several auxin/cytokinin combinations, physical conditions, osmotic stresses and supplementary components, viz., amino acids and casein hydrolysate were tested for induction of embryogenic callus. Higher frequency of embryogenic calli (73.7 %) and somatic embryos per culture (22) were observed on MS + 1.5 mg l−1 BA + 0.5 mg l−1 NAA + 0.5 % NaCl. Histological analyses showed typical globular and other stages of embryo development. The MS medium lacking growth regulators was best for the maximum germination of embryos (53.4 %) and formation of plantlets (65.4 %). Regenerated plantlets were acclimatized and transferred to the field with 62 % survival rate.

EFFECTIVENESS OF CULTURE MEDIA ON THE SUCCESS OF EMBRYO RESCUE AMONG DIFFERENT CROSSES OF SEEDLESS GRAPES

Effects of culture media on the success of embryo rescue were tested among three different cross combinations of seedless grapes. ER, N&N, WP and ½ MS media were used. The best medium for ovule development was ER + 6-BA 0.5 mg/L among all 3 cross combinations. For embryo germination and plantlet formation, the success rate varied among different cross combinations. The best media for seedling establishment in ?Flame Seedless? × ?Centennial?, for example, were 1/2 MS for embryo germination and 1/2 MS + IBA 0.1 mg/L for seedling growth. The best media for ?Otilia? × ?Venus? were 1/2 MS + IAA 0.1 mg/L for embryo germination, 1/2 MS + IAA 0.1 mg/L for seedling growth, and half strength B5 + IAA 0.125 mg/L for subculture, respectively. The best media for ?Venus? × ?Himrod? were 1/2 MS for embryo germination, WP + 6-BA 0.1 mg/L for seedling growth, half strength of B5 + IAA 0.125 mg/L for subculture, respectively.

Rapid in vitro propagation of Inula royleana DC. through embryo culture

During present study a rapid in vitro propagation method was developed for Inula royleana, a medicinal perennial herb, through embryo culture. Embryo germination and complete plantlet formation was obtained on basal MS medium in a time period of 6 and 11 days respectively with 100% culture response. Indirect shoot regeneration with 25±0.6 mean number of shoots was also obtained in 70% cultures when leaf explants obtained from germinated embryos were inoculated on MS medium containing BAP (5 mg/l) +IAA (2 mg/l).

Truncation of LEAFY COTYLEDON1 Protein Is Required for Asexual Reproduction in Kalanchoë daigremontiana

Kalanchoë daigremontiana reproduces asexually by generating numerous plantlets on its leaf margins. The formation of plantlets requires the somatic initiation of organogenic and embryogenic developmental programs in the leaves. However, unlike normal embryogenesis in seeds, leaf somatic embryogenesis bypasses seed dormancy to form viable plantlets. In Arabidopsis (Arabidopsis thaliana), seed dormancy and embryogenesis are initiated by the transcription factor LEAFY COTYLEDON1 (LEC1). The K. daigremontiana ortholog of LEC1 is expressed during leaf somatic embryo development. However, KdLEC1 encodes for a LEC1-type protein that has a unique B domain, with 11 unique amino acids and a premature stop codon. Moreover, the truncated KdLEC1 protein is not functional in Arabidopsis. Here, we show that K. daigremontiana transgenic plants expressing a functional, chimeric KdLEC1 gene under the control of Arabidopsis LEC1 promoter caused several developmental defects to leaf somatic embryos, including seed dormancy characteristics. The dormant plantlets also behaved as typical dormant seeds. Transgenic plantlets accumulated oil bodies and responded to the abscisic acid biosynthesis inhibitor fluridone, which broke somatic-embryo dormancy and promoted their normal development. Our results indicate that having a mutated form of LEC1 gene in K. daigremontiana is essential to bypass dormancy in the leaf embryos and generate viable plantlets, suggesting that the loss of a functional LEC1 promotes viviparous leaf somatic embryos and thus enhances vegetative propagation in K. daigremontiana. Mutations resulting in truncated LEC1 proteins may have been of a selective advantage in creating somatic propagules, because such mutations occurred independently in several Kalanchoë species, which form plantlets constitutively.

Immature embryo is the potential source for in vitro plant regeneration in Jatropha curcas

Context: Jatropha belongs the spurge family Euphorbiaceae. Special interest mounting for its biodiesel which has created enthusiasm in cultivation of the species for oil extraction. Objectives: The study was conducted to develop the protocol for tissue and callus culture in Bangladeshi Jatropha curcus plant particularly to identify the most suitable explants for its wide scale micropropagation. Materials and Methods: Immature embryos taken from four developmental stages of fruits were cultured on growth regulator free MS liquid medium. After fifteen days of germination, elongated hypocotyls and two cotyledonary leaves were used as explants. Results: Embryo derived seedlings acted as the potential source of explants both for callus and plantlets. The immature embryo of size 0.87cm produced highest callus formation (83.33%) on MS medium supplemented with lower concentration of 2, 4-D (0.5 mg/l) and coconut water 2% (v/v). Immature embryos grown on MS basal medium supplemented with 2,4-D (0.2 mg/l, 0.5 mg/l and 1.0 mg/l) alone or in combination with coconut water 2% (v/v) exhibited a wide range of callus induction percentage (26-100%) for hypocotyls and (20 - 40%) for cotyledonary leaves. Conclusion: The age of immature embryo and addition of growth adjuvants and growth additive to the culture medium played the role in promoting better callus and plantlet formation. DOI: http://dx.doi.org/10.3329/jbs.v20i0.17726 J. bio-sci. 20: 125-134, 2012

Improvement Germination and Conversion of Somatic Embryos and Production of Normal Plantlets in Ferula Assa-foetida L. (A Rare Medicinal Plant)

Secondary somatic embryogenesis leads to the formation of abnormal somatic embryos and produces abnormal seedlings. Normal plants are difficult to obtain from these embryos, due to the asynchronous maturationof the embryogenic tissues and low germination and conversion rates. The effects of some media additives and different strengths of MS medium on germination and plantlet formation of in vitro derived somatic embryos of FerulaAssa-foetidawere studied.The highest number of normal embryos was observed in MS medium containing 30g/l sucrose with 0.5% or 1% AC and in MS medium supplemented with PEG and 0.5% or 1% AC. The treatments of MS medium with 30g/l sucrose and 0.5% AC ◊ MS medium containing sorbitol and MS medium containing PEG and 1% AC ◊ Ω MS had maximum number of normal germinated embryos without secondary somatic embryogenesis (SSE). In some of the treatments the embryos were converted better than the others, such as; the interact ion effect of MS medium with 30g/l sucrose and0.5% AC◊ MS, MS medium with 30g/l sucrose ◊ MS medium with glutamine. Using different strength of MS medium and presence of some media additives is effective on germination and conversion of somatic embryos into normal plantlet. Presence of Activated Charcoal in the culture medium can reduce secondary somatic embryogenesis.

Study of Genetic Fidelity of Somatic Embryos - Derived Plants of Gentiana kurroo Royle from Western Himalayas - Plant of Great Medicinal Value

Aim: To study the effect of plant growth regulators on direct and indirect somatic embryogenesis on Gentiana kurroo Royle – an endangered medicinal plant. Place and Duration of Study: Department of Biotechnology, Dr Y. S. Parmar University of Horticulture and Forestry, Nauni, Solan-173230, Himachal Pradesh, India, 2010-2013. Methodology: For induction of direct and indirect somatic embryogenesis petiole, leaf and petiole derived callus (after incubation in activated charcoal) were cultured on MS medium supplemented with a range of combinations of auxins (2,4-D, picloram, dicamba) and cytokinins (zeatin, kinetin). Results: Somatic embryos were observed from both direct and indirect method. The best performance was observed on MS basal medium supplemented 1.0mg/l dicamba. Development of somatic embryos was observed on MS basal+0.50mg/l GA3+1.0 mg/lKn and the maximum plantlets formation was achieved when somatic embryos (directly and indirectly induced) were shifted to half strength MS basal medium. Original Research Article British Biotechnology Journal, 4(5): 589-611, 2014 590 Conclusion: In direct pathway somatic embryos were in contact with maternal tissue in a suspensor like structure. In indirect pathway, the explants first proliferated to give rise to callus before embryoids were induced. Somatic embryos have their own vascular tissues, and can develop new plantlets independently.

Induction of shoot buds, multiplication and plantlet formation in seedling explants of bell pepper (Capsicum annuum L.) cv. Bryza in vitro

In vitro shoot bud induction and multiplication as well as plantlets formation from different parts of 21-d old seedlings (shoot tip, cotyledonary node, distal part of cotyledon, acropetal section of hypocotyl) of <em>Capsicum annuum</em> L., cv. Bryza were compared. During 4 weeks of primary explant culture on initiation media, first shoot bud primordia appeared; they reminded leaf primordia and subsequently some of them underwent enlargement, some developed into leaves and leaf-like structures (mainly on cotyledon explants). The highest number of shoot bud primordia was noted on cotyledonary node explants, but they were smaller than those on the remaining types of the explants. The best response of shoot regeneration showed cotyledon explants on which most of shoot buds were formed in each from four treated passages. From shoot buds on elongation media after 4 weeks of culture rooted rosettes of leaves were achieved, and the extension of the culture time to eight weeks without subculture caused that the rosettes developed into plantlets. Throughout four successive passages plantlets were obtained from cotyledon and shoot tip explants.

Micropropagation of six Paulownia genotypes through tissue culture

We investigated the effect of genotype and culture medium on the in vitro germination and development of plantlets from seeds of 6 different Paulownia genotypes (P. tomentosa, hybrid lines P. tomentosa × P. fortunei (Mega, Ganter and Caroline), P. elongata and hybrid line P. elongata × P. fortunei). Nodal and shoot tip explants were used for micropropagation of Paulownia genotypes by manipulating plant growth regulators. The highest germination percentage for all genotypes was obtained for seeds inoculated on medium supplemented with 50 mg*L GA3 (MSG2). On Thidiazuron containing media, the explants of hybrid line P. elongata × P. fortunei exhibited the highest frequency of axillary shoot proliferation following by P. tomentosa × P. fortunei. The results are discussed with the perspective of applying an improved protocol for in vitro seed germination and plantlet formation in several economically valuable Paulownia genotypes.