Effects of abiotic and biotic elicitors on growth and isoflavonoid accumulation in Pueraria candollei var. candollei and P. candollei var. mirifica cell suspension cultures

This study demonstrates the effects of various concentrations of abiotic and biotic elicitors on the cell growth and isoflavonoid accumulation of P. candollei var. mirifica (PM) and P. candollei var. candollei (PC) cell suspension cultures. The two plant varieties exhibited different growth responses and varied isoflavonoid accumulation after the addition of elicitors. Copper sulfate, methyl jasmonate (MeJA), and yeast extract did not significantly affect the growth of either plant variety, whereas oligosaccharide and the biotic elicitors used in this study [i.e., 50 mg l⁻¹ chitosan and all concentrations of laminarin (LAM)] suppressed the growth of PM. The addition of MeJA to the medium principally induced an effect on the isoflavonoid content in both PM and PC, with 2.0 μM MeJA inducing the highest isoflavonoid content, as indicated by the induction index—4.41 in PM and 9.62 in PC cells on the 12th and ninth day of culture, respectively. A maximum total isoflavonoid content of 40.49 mg g⁻¹ dry weight was achieved in PM 21 days after elicitation with 2.0 μM MeJA. LAM elicited the PM cell suspension culture to produce puerarin, which was not found in the unelicited culture. The results of this study provide information that will be useful for enhancing the accumulation of isoflavonoids in P. candollei cell suspension cultures.     

Increased miroestrol, deoxymiroestrol and isoflavonoid accumulation in callus and cell suspension cultures of Pueraria candollei var. mirifica

Miroestrol and deoxymiroestrol are highly active phytoestrogens derived from the tuberous roots of Pueraria candollei var. mirifica. To date, there have been no reports regarding the production of miroestrol and deoxymiroestrol in in vitro cell culture. In this study, callus and cell suspension cultures were established for the purpose of investigating miroestrol and deoxymiroestrol content in P. candollei var. mirifica cells. Stem-derived callus cultured on Murashige and Skoog (MS) medium supplemented with 0.1 mg l⁻¹ thidiazuron (TDZ), 0.5 mg l⁻¹ naphthaleneacetic acid (NAA), and 1.0 mg l⁻¹ benzyladenine (BA) provided optimal conditions for the accumulation of deoxymiroestrol and total isoflavonoids. The calli produced 184.83 ± 20.09 μg g⁻¹ dry weight of total chromene and 20.72 ± 2.38 mg g⁻¹ dry weight of total isoflavonoid. This is the first report to suggest that callus culture is a suitable alternative method for producing miroestrol and deoxymiroestrol. Carbon sources were evaluated for the cell suspension cultures of P. candollei var. mirifica. Sucrose provided optimal conditions for biomass production, whereas fructose was the most suitable carbon source for deoxymiroestrol and isoflavonoid production. The information from our study can be employed for enhancing the production of miroestrol, deoxymiroestrol, and total isoflavonoids using in vitro cell culture of P. candollei var. mirifica.     

Improved isoflavonoid production in Pueraria candollei hairy root cultures using elicitation

The effect of abiotic and biotic elicitors (methyl jasmonate, chitosan, salicylic acid, Agrobacterium, and yeast extract) at various concentrations on total isoflavonoid accumulation was studied in the hairy root cultures of Pueraria candollei. All elicitors stimulated isoflavonoid production. Yeast extract (0.5 mg/ml) was the most efficient giving total isoflavonoids at 60 ± 1 mg/g dry wt, which was 4.5-fold higher than control hairy roots on day 3 of elicitation.     

Effects of Agrobacterium rhizogenes strains and other parameters on production of isoflavonoids in hairy roots of Pueraria candollei Grah. ex Benth. var. candollei

Using several explants of Pueraria candollei Grah. ex Benth. var. candollei and two strains of Agrobacterium rhizogenes (ATCC 15834 and 43057), hairy root cultures were established. Including 100???M acetosyringone in the culture medium enhanced frequency of hairy root induction by up to 58?%. Subsequently, effects of inoculum size (IS) and temperature on growth and production of isoflavonoids in hairy roots were determined. Conditions of 1?%?IS and 32?°C promoted the highest accumulation of total isoflavonoid content, up to 31.0?±?22.6?mg/g dry weight (DW), in hairy roots. Moreover, culture of hairy roots at 32?°C decreased browning of hairy roots. Furthermore, this temperature promoted accumulation of the secondary metabolite daidzein; whereas, hairy root cultures at the stationary phase accumulated higher amounts of the isoflavonoid puerarin rather than daidzein.     

Production of chlorogenic acid and isoorientin hypoglycemic compounds in Cecropia obtusifolia calli and in cell suspension cultures with nitrate deficiency

The antidiabetic properties of Cecropia obtusifolia are attributed to chlorogenic acid (CGA) and isoorientin (ISO) phenolic compounds; both compounds possess hypoglycemic, hypolipidemic, and antioxidant properties. As a potential strategy for an adequate supply of authentic plant raw material, the aim of this study was to establish in vitro conditions for the development of cell suspension cultures that produce these bioactive compounds. Callus cultures of leaf explants from acclimatized tree and in vitro plantlets were set up using different auxin levels; treatments with 2,4-dichlorophenoxyacetic acid (2,4-D) and α-naphthalene acetic acid (NAA) to 8.92 μM with 6-benzylaminopurine (BAP) at 2.22 μM stimulate highest callus production. Seedling cotyledon, hypocotyl, leaf, and stem explants developed calli bearing roots with 2,4-D. With NAA, hypocotyl, cotyledon, and leaf explants developed morphogenic calli; 75% of stem explants formed calli, and the remaining calli developed shoots. Determined CGA concentrations in calli were similar to those detected in the leaves of wild trees, and ISO was not produced. Cell suspension cultures were established from leaf explants friable calli with 8.92 μM 2,4-D in combination with 2.22 μM BAP, employing 4 and 5% inocula in fresh weight; CGA levels were maintained and ISO was produced only at the end of logarithmic growth. On diminishing nitrate content in Murashige and Skoog (MS) medium to 8.0 mM, maximum cell biomasses diminished, CGA production is increased and twice with 16.0 and, instead of CGA production is tripled and quadrupled with 16.0 and 8.0 mM nitrates, respectively, and ISO synthesis was induced earlier and for a longer time period, increasing its levels at the end of culture. Two compounds with ultraviolet spectra similar to those of caffeic and ferulic acids were formed. Our results offer a protocol of cell suspension cultures for C. obtusifolia bioactive production and hypoglycemic property conservation.     

Zinc tolerance and accumulation in stable cell suspension cultures and in vitro regenerated plants of the emerging model plant Arabidopsis halleri (Brassicaceae)

Arabidopsis halleri is increasingly employed as a model plant for studying heavy metal hyperaccumulation. With the aim of providing valuable tools for studies on cellular physiology and molecular biology of metal tolerance and transport, this study reports the development of successful and highly efficient methods for the in vitro regeneration of A. halleri plants and production of stable cell suspension lines. Plants were regenerated from leaf explants of A. halleri via a three-step procedure: callus induction, somatic embryogenesis and shoot development. Efficiency of callus proliferation and regeneration depended on the initial callus induction media and was optimal in the presence of 1 mg L⁻¹ 2,4-dichlorophenoxyacetic acid, and 0.05 mg L⁻¹ benzylaminopurine. Subsequent shoot and root regeneration from callus initiated under these conditions reached levels of 100% efficiency. High friability of the callus supported the development of cell suspension cultures with minimal cellular aggregates. Characterization of regenerated plants and cell cultures determined that they maintained not only the zinc tolerance and requirement of the whole plant but also the ability to accumulate zinc; with plants accumulating up to 50.0 μmoles zinc g⁻¹ FW, and cell suspension cultures 30.9 μmoles zinc g⁻¹ DW. Together this work will provide the experimental basis for furthering our knowledge of A. halleri as a model heavy metal hyperaccumulating plant.     

Establishment of anthocyanin-producing cell suspension cultures of Cleome rosea Vahl ex DC. (Capparaceae)

The effects of different levels of Murashige and Skoog (MS) basal medium, 2,4-dichlorophenoxyacetic acid (2,4-D), and sucrose on anthocyanin production and biomass accumulation of cell suspension cultures of Cleome rosea were investigated. Cultures were established in liquid MS medium containing 30 g l⁻¹ sucrose and supplemented with 0.90 μM 2,4-D. Proliferating cell suspension cultures achieved the highest growth capacity, a fourfold increase in biomass accumulation, following subculture at the exponential growth phase, 14–18 days of culture. Moreover, the presence of 2,4-D was essential for anthocyanin production and biomass accumulation. On the other hand, increasing levels of sucrose above 30 g l⁻¹ resulted in a drastic reduction in biomass accumulation. Anthocyanin production was highest in cell suspension cultures grown on half-strength MS medium (1/2 MS), 30 g l⁻¹ sucrose, and 0.45 μM 2,4-D. These cell suspension cultures were mainly composed of small aggregates of spherical cells with similar morphology observed in anthocyanin-producing and non-producing cultures. Moreover, microscopic analysis of anthocyanin-producing cultures showed the presence of mixtures of non-pigmented, low-pigmented, and high-pigmented cells.     

Dedifferentiation of leaf explants and cytotoxic activity of an aqueous extract of cell cultures of Lantana camara L.

Several secondary metabolites are present in Lantana camara L. as its leaves serve as reservoirs for various bioactive compounds. Callus cultures of L. camara were induced from leaf discs incubated on Murashige and Skoog medium supplemented with 5 μM 6-benzyladenine, 1 μM 2,4-dichlorophenoxyacetic acid, and 1 μM α-naphthalene acetic acid (NAA). An aqueous extract (0.23%), obtained from these calli (50 g dry mass), had an apparent cytotoxic effect on HeLa cells with an IC₅₀ value of 1,500 μg/ml in 36 h. A dose-time dependent activity of the extract was established wherein higher dosage exhibited increased activity; however, over time cell necrosis was observed.     

In vitro morphogenetic responses and comparative analysis of phthalides in the highly valued medicinal plant Ligusticum porteri Coulter & Rose

The morphogenetic response of Ligusticum porteri, a medicinal and ceremonial plant, was investigated as part of the conservation strategy of this wild species and was compared to that of a cultivated species, Petroselinum crispum. Seeds were germinated in half strength Murashige and Skoog medium. Plantlets were excised into root, cotyledon, petiole, stem and leaf explants and cultured in an induction medium supplemented with the range of 0–18.09 μM 2,4-dichlorophenoxyacetic acid (2,4-D) or 0–21.48 μM α-naphthaleneacetic acid in combination with 0–13.31 μM 6-benzylaminopurine. Calli derived from leaf, seeds, petiole, stem and roots, mature aerial parts and roots extracts of L. porteri and P. crispum were analyzed by thin layer chromatography and gas chromatography coupled to mass spectrometry. 3-Butylidenephthalide (6.3%) was identified along with other 23 compounds from mature aerial parts extract of L. porteri and also in its roots (20.8%). 3-n-Butylphthalide (0.7%) and 3,6,7,-trimethoxy-isobenzofuran-13(H)-one (4.9%) were identified from the roots of P. crispum. 3-Butylidenephthalide was identified from two petiole (0.9%; 0.26%) and one stem (0.8%) callus extracts of L. porteri. This is the first report on phthalides production from in vitro cultures of L. porteri. The results indicated that in vitro cultures of this plant possess the biosynthetic machinery for the biosynthesis of these highly valuable compounds.     

Compact callus cluster suspension cultures of Catharanthus roseus with enhanced indole alkaloid biosynthesis

Summary Compact callus clusters showing a certain level of cellular or tissue differentiation were established from Catharanthus roseus stem and leaf explants in a modified MS liquid induction medium supplemented with 5.37 μM α-naphthaleneacetic acid and 4.65 μM kinetin. In the induction medium most leaf explants developed into friable half-closed hollow callus clusters, whereas in the same medium containing 2,4-dichlorophenoxyacetic acid instead of α-naphthaleneacetic acid, most leaf explants were induced to form dispersed cell suspension cultures. Characteristics of these different types of suspension cultures were compared, and the results showed that the compact callus clusters could synthesize indole alkaloids 1.9- and 2.4-fold higher than the half-closed hollow callus clusters and dispersed cell cultures, respectively. The degree of compaction expressed by the ratio of fresh weight to dry weight of these suspension cultures was correlated to indole alkaloid production. Our studies also postulated that the level of cellular/tissue differentiation might be responsible for these different alkaloid synthesis capabilities. Sucrose regime affected some properties (the size, degree of compaction, differentiation level) of the compact callus cluster cultures and therefore influenced alkaloid production.     

High frequency plant regeneration from immature ovule-derived embryogenic cell suspension cultures of Chelidonium majus var. asiaticum

Culture conditions for high frequency plant regeneration via somatic embryogenesis in cell suspension cultures of Chelidonium majus var. asiaticum are described. Immature ovules formed embryogenic calluses at a frequency of 40% when cultured on Murashige and Skoog (MS) medium supplemented with 4.52 μM 2,4-dichlorophenoxyacetic acid (2,4-D). The optimum ovule size for embryogenic callus formation ranged from 1 to 1.5 mm in length. Cell suspension cultures were established from embryogenic calluses using MS liquid medium containing 4.52 μM 2,4-D. Upon plating onto MS basal medium, cell aggregates from cell suspension cultures produced somatic embryos which then developed into plantlets. Regenerated plantlets were transplanted to potting soil and grown to maturity in a growth chamber. This revised version was published online in June 2006 with corrections to the Cover Date.     

Bupleurum candollei var. paucefulcrans comb. nov. (Apiaceae) from Guizhou,China: comparison of allied species based on morphology,anatomy and molecular data

The new combination, Bupleurum candollei Wallich ex de Candolle var. paucefulcrans (C. Y. Wu) X. J. He & C. B. Wang, is proposed. The status of this taxon, endemic to Guizhou, China, has been confused since it was first described in 1963. Morphological and anatomical evidence, based primarily on bractlet number and length, umbel number and length, fruit size and shape, and stem structure indicated that B. hamiltonii N. P. Balakrishnan var. paucefulcrans C. Y. Wu is more closely related to B. candollei than to B. hamiltonii. To evaluate the credibility of the morphological similarity, the phylogenetic relationship of B. candollei var. candollei, B. hamiltonii var. hamiltonii and B. candollei var. paucefulcrans were inferred by Bayesian analysis of nrDNA ITS sequences. The molecular analysis is fully congruent with the morphological data and supports the transfer of the variety to B. candollei.     

Phenylpropanoid production in callus and cell suspension cultures of <Emphasis Type="Italic">Buddleja cordata</Emphasis> Kunth

Plant tissue cultures represent a potential source for producing secondary metabolites. In this work, Buddleja cordata tissue cultures were established in order to produce phenylpropanoids (verbascoside, linarin and hydroxycinnamic acids), as these metabolites are credited with therapeutic properties. Highest callus induction (76.4–84.3%) was obtained in five treatments containing 2,4-Dichlorophenoxyacetic acid (2,4-d: 0.45–9.05 μM) with Kinetin (KIN: 2.32, 4.65 μM), whereas highest root induction (79.6%) corresponded to the α-Naphthaleneacetic acid (9.05 μM) with KIN (2.32 μM) treatment. Verbascoside was the major phenylpropanoid produced in in vitro cultures (root, white and green callus) [66.24–86.26 mg g⁻¹ dry weight (DW)], while linarin and hydroxycinnamic acid production was low (0.95–3.01 mg g⁻¹ DW). Verbascoside and linarin production were improved in cell suspension culture (116 mg g⁻¹ DW and 8.12 mg g⁻¹ DW, respectively).     

Oxytocin influences the production of glycyrrhizin from cell cultures of Abrus precatorius Linn.

Oxytocin, a peptide animal hormone, was used as a growth regulator to test its effect on biomass accumulation and production of secondary plant constituent glycyrrhizin in the cell cultures of Abrus precatorius. Glycyrrhizin is an important phytoconstituent of liquorice which is widely used in the pharmaceutical and food industries. Cell suspension cultures of A. precatorius were developed from leaf explant of in vitro germinated plant in Murashige and Skoog medium supplemented with 30 g/l sucrose, 1 mg/l naphthalene acetic acid and 1 mg/l kinetin. The influence of oxytocin on biomass accumulation as well as on the production of glycyrrhizin was observed in the cell cultures of A. precatorius. Treatment of A. precatorius cell cultures with 100 μg/l oxytocin, improved glycyrrhizin production up to 34.27 mg/l on the dry cell weight basis third day after oxytocin treatment, which is over four times that of the control cultures, simultaneously nearly two fold increase in the biomass 2 days after the oxytocin treatment was recorded over the control cultures.     

High frequency plant regeneration via somatic embryogenesis in cell suspension cultures of cowpea, Vigna unguiculata (L.) Walp.

Summary Embryogenic callus was induced from primary leaves of Vigna unguiculata (L.) Walp. in MS medium (Murashige and Skoog, 1962) containing 2,4-dichlorophenoxyacetic acid (2,4-D). Greenish-white, friable embryogenic calluses were used to establish suspension cultures. A shaking speed of 90 rpm and 0.4 ml packed cell volume per 25 ml medium were found to be optimal for maintaining suspension cultures. Globular, heart-shaped and torpedo-shaped embryos were developed in suspension culture containing 4.52 μM 2,4-D. Maturation of cotyledonary-stage somatic embryos was achieved on 0.05 μM 2,4-D, 5 μM abscisic acid and 3% mannitol. Twenty-two percent of the embryos were converted into plants and survived; survival in the field was 8–10%.     

Multiplication and germination of somatic embryos of American ginseng derived from suspension cultures and biochemical and molecular analyses of plantlets

Summary Seedlings from 11 seed sources (lines) of American ginseng from different geographic regions were evaluated on Murashige and Skoog medium (MS) containing 10 μM α-naphthaleneacetic acid (NAA) and 9 μM 2,4-dichlorophenoxyacetic acid (2,4-D) for callus development and somatic embryo formation. Leaf and stem explants callused at a frequency of 18.2–100%, while somatic embryos were produced from these calluses at a frequency of 25–87.5% after 5 mo. Suspension cultures of nine lines were established by transferring embryogenic callus to MS liquid medium with NAA and 2,4-D at 2.5 and 2.25 μM, respectively, and maintained by subcultures every 8 wk. Globular somatic embryos from these cultures were germinated on half-strength MS containing 1% activated charcoal, and roots >5 mm in length developed within 3 wk. A 7-d exposure to 3 μM gibberellic acid and 5 μM 6-benzylaminopurine significantly enhanced shoot development and promoted further root development. The chromosome number, profiles of the common triterpenoid saponins (ginsenosides), and random amplified polymorphic DNA (RAPD) banding patterns in plantlets derived from suspension culture were compared to those of zygotic seedlings. The chromosome number in root tip cells and suspension cultured cells was 48. Patterns of the six major ginsenosides, determined by thin-layer chromatography, in leaves of tissue culture-derived plantlets were identical to those in seedlings. RAPD patterns among plantlets originating from the same tissue-cultured line were mostly identical; however, altered patterns were observed in some lines that had been maintained in suspension culture for almost 4 yr. The results from this study indicate that propagation of desired ginseng genotypes in suspension culture can be achieved, and that biochemical and molecular markers can be used for authentication of resulting plantlets.     

Plant regeneration through somatic embryogenesis in medicinally important <Emphasis Type="Italic">Centella asiatica</Emphasis> L.

Summary High-frequency somatic embryogenesis and plant regeneration was achieved on callus derived from leaf (petiole and lamina) and internode explants of Centella asiatica L. Growth regulators significantly influenced the frequency of somatic embryogenesis and plant regeneration. Calluses developed on Murashige and Skoog (MS) medium fortified with 4.52 μM 2,4-dichlorophenoxyacetic acid (2,4-D) or 5.37 μM α-naphthaleneacetic acid (NAA), both with 2.32 μM kinetin (Kn), were superior for somatic embryogenesis. Callus developed on NAA and Kn-supplemented medium favored induction and maturation of embryos earlier compared to that on 2,4-D and Kn. Embryogenic callus transferred from NAA and Kn-supplemented medium to suspension cultures of half-strength MS medium with NAA (2.69 μM) and Kn (1.16 μM) developed a mean of 204.3 somatic embryos per 100 mg of callus. Embryogenic callus transferred from 2,4-D and Kn subsequently to suspension cultures of half-strength MS medium with 2,4-D (0.45 μM) and Kn (1.16 μM) developed a mean of 303.1 embryos per 100 mg of callus. Eighty-eight percent of the embryos underwent maturation and conversion to plantlets upon transfer to half-strength MS semisolid medium having 0.054 μM NAA with either 0.044 μM BA or 0.046 μM Kn. Embryo-derived plantlets established in field conditions displayed morphological characters identical to those of the parent plant.     

Plant regeneration of creeping bluestem (Schizachyrium scoparium (Michx.) Nash var. Stoloniferum (Nash) J. Wipff) via somatic embryogenesis

Summary Creeping bluestem (Schizachyrium scoparium (Michx.) Nash var. stoloniferum (Nash) J. Wipff) embryogenic callus growing on solid medium was used to establish a cell suspension culture in Murashige and Skoog (MS) basal medium supplemented with 1.5 mg l⁻¹ (6.8 μM) 2,4-dichlorophenoxyacetic acid (2,4-D), 0.2 mg l⁻¹ (0.88 μM) 6-benzylaminopurine (BA), 0.5 mg l⁻¹ (1.4 μM) zeatin, 0.2 mg l⁻¹ (0.58 μM) gibberellic acid (GA₃), and 10% (v/v) of coconut water (CW). Pro-embryos from suspension culture matured on semi-solid MS medium in about 18 wk, and were then cultured on semi-solid MS medium without growth regulators for 2–3 wk. Shoots were regenerated on MS basal medium supplemented with 3.0 mg L⁻¹ (13.6 μM) 2,4-D, 1.0 mg l⁻¹ (4.4 μM) BA, 1.0 mg l⁻¹ (2.9 μM) GA₃, 0.5 mg l⁻¹ (2.7 μM) 1-naphthaleneacetic acid (NAA), 500 mg l⁻¹ easein hydrolysate, and 10% (v/v) CW. Rooted plantlets were successfully accelimatized to greenhouse and outdoor conditions. Using this protocol, it would be possible to produce at least 1300 fully acclimatized plantlets annually.     

Regeneration of <Emphasis Type="Italic">Aeschynanthus radicans</Emphasis> via direct somatic embryogenesis and analysis of regenerants with flow cytometry

Plant regeneration through direct somatic embryogenesis in Aeschynanthus radicans ‘Mona Lisa’ was achieved in this study. Globular somatic embryos were formed directly from cut edges of leaf explants and cut ends or on the surface of stem explants 4 wk after culture on Murashige and Skoog (MS) medium supplemented with N-phenyl-N′-1, 2, 3-thiadiazol-5-ylurea (TDZ) with α-naphthalene acetic acid (NAA), TDZ with 2,4-dichlorophenoxyacetic acid (2,4-D), or 6-benzylaminopurine (BA) or kintin (KN) with 2,4-D. MS medium containing 9.08 μM TDZ and 2.68 μM 2,4-D resulted in 71% of stem explants producing somatic embryos. In contrast, 40% of leaf explants produced somatic embryos when induced in medium containing 6.81 μM TDZ and 2.68 μM 2,4-D. Somatic embryos matured, and some germinated into small plants on the initial induction medium. Up to 64% of stem explants cultured on medium supplemented with 9.08 μM TDZ + 2.68 μM 2,4-D, 36% of leaf explants cultured on medium containing 6.81 μM TDZ and 2.68 μM 2,4-D had somatic embryo germination before or after transferring onto MS medium containing 8.88 μM BA and 1.07 μM NAA. Shoots elongated better and roots developed well on MS medium without growth regulators. Approximately 30–50 plantlets were regenerated from each stem or leaf explant. The regenerated plants grew vigorously after transplanting to a soil-less substrate in a shaded greenhouse with more than a 98% survival rate. Three months after their establishment in the shaded greenhouse, 500 plants regenerated from stem explants were morphologically evaluated, from which five types of variants that had large, orbicular, elliptic, small, and lanceolate leaves were identified. Flow cytometry analysis of the variants along with the parent showed that they all had one identical peak, indicating that the variant lines, like the parent, were diploid. The mean nuclear DNA contents of the variant lines and their parent ranged from 4.90 to 4.99 pg 2C⁻¹, which were not significantly different statistically. The results suggest that the regenerated plants have a stable ploidy level, and the regeneration method established in this study can be used for rapid propagation of ploidy-stable Aeschynanthus radicans.     

Somatic embryogenesis in cell suspension cultures of olive <Emphasis Type="Italic">Olea europaea</Emphasis> (L.) ‘Chetoui’

Somatic embryogenesis of olive Olea europaea (L.) ‘Chetoui’ was studied using cell suspension cultures initiated from mature leaf-derived calli. Calli were developed on half-strength MS medium supplemented with 10 μM NAA and 2.25 μM 2i-P in the dark. Different combinations of three plant growth regulators (2,4-D, NAA and zeatin) were tested to determine cell proliferation and somatic embryogenesis induction and differentiation. Embryogenic suspension cultures were established in olive-modified medium for embryogenesis (OMe) containing 2.5 μM 2,4-D and 2.5 μM zeatin. Pre-globular and globular embryos were induced from mature olive tissue in liquid medium. In addition, the nitrogen form as inorganic (reduced; (NH₄)₂SO₄ or oxidized; KNO₃) and organic (CH) was used separately or in combination to improve the cell growth and proliferation. The most effective growth rate and cell proliferation were obtained with the medium containing inorganic and organic nitrogen forms.