Factors important for somatic embryogenesis in zygotic embryo explants ofCapsicum annuum L.

We used four cultivars ofCapsicum annuum L.—Sweet Banana, California Wonder, Yolo Wonder, and Ace—to reexamine the critical factors influencing somatic embryogenesis from zygotic embryo explants, as reported in the literature. When we followed the protocol of Buyukalaca and Mavituna (1996), which had induced somatic embryogenesis from mature zygotic embryos of cv. Ace, only callus was formed without embryogenesis from our mature zygotic embryo expiants. Using the procedures of Harini and Lakshmi Sita (1993) and Binzel et al. (1996), with some modifications, we were able to induce somatic embryogenesis in all four cultivars. Rates of conversion were significantly reduced, from 75% and 65% to 40% and 28% in ’Sweet Banana’ and ’California Wonder’, respectively, when the immature zygotic embryo expiants were held on the induction medium for longer than two weeks. Likewise, somatic embryogenesis of ’Yolo Wonder’ was not observed if the induction medium was supplemented with 10% glucose or fructose, or without 10% sucrose. For somatic embryo induction and eventual plantlet conversion in Yolo Wonder’, maltose could adequately replace sucrose. In all four cultivars, somatic embryos were initiated from immature zygotic explants on media with or without coconut water, under both light and dark conditions.     

Genotype effects on proliferative embryogenesis and plant regeneration of soybean

Summary Proliferative somatic embryogenesis is a regeneration system suitable for mass propagation and genetic transformation of soybean [Glycine max (L.) Merr.]. The objective of this study was to examine genotypic effects on induction and maintenance of proliferative embryogenic cultures, and on yield, germination, and conversion of mature somatic embryos. Somatic embryos were induced from eight genotypes by explanting 100 immature cotyledons per genotype on induction medium. Differences in frequency of induction were observed among genotypes. However, this step was not limiting for plant regeneration because induction frequency in the least responding genotype was sufficient to initiate and maintain proliferative embryogenic cultures. Six genotypes selected for further study were used to initiate embryogenic cultures in liquid medium. Cultures were evaluated for propagation of globular-stage tissue in liquid medium, yield of cotyledon-stage somatic embryos on differentiation medium, and plant recovery of cotyledon-stage embryos. Genotypes also differed for weight and volume increase of embryogenic tissue in liquid cultures, for yield of cotyledon-stage embryos on differentiation medium, and for plant recovery from cotyledon-stage embryos. Rigorous selection for a proliferative culture phenotype consisting of nodular, compact, green spheres increased embryo yield over that of unselected cultures, but did not affect the relative ranking of genotypes. In summary, the genotypes used in this study differed at each stage of plant regeneration from proliferative embryogenic cultures, but genotypic effects were partially overcome by protocol modifications.     

Genotype-specific normalization of soybean somatic embryogenesis through the use of an ethylene inhibitor

The effect of ethylene on somatic embryogenesis from cotyledons of soybean (Glycine max) cultivars `Bragg', `IAS-5', and `RS-7' was studied through the application of silver nitrate or aminoethoxyvinylglycine. The addition of these chemicals to the induction medium had no effect on embryo induction, in spite of aminoethoxyvinylglycine having decreased ethylene production and silver nitrate enhancing it. However, subsequent histodif-ferentiation and conversion capacity of somatic embryos was affected by treatments applied to the induction medium. The effects of ethylene on embryo histodifferentiation and conversion were genotype-specific. Cultivars `IAS-5' and `RS-7' produced high frequencies of dicotyledonous embryos and had high conversion rates. These were also the least affected by alterations in ethylene production. For `Bragg', which has a low regeneration capacity, the use of aminoethoxyvinylglycine led to a significant improvement in the frequency of normal embryo formation as well as in the frequency of conversion into plants. The results suggest that the use of ethylene inhibitors during the induction process may facilitate plant recovery from soybean genotypes, such as `Bragg', which have a low regeneration capacity. Received: 8 October 1996 / Revision received: 6 May 1997 / Accepted: 3 June 1997     

大豆主栽品种体细胞胚胎发生的影响因素及再生植株

Factors on in vitro somatic embryogenesis of soybean (three elite cultivars) were studied using cotyledons of 3.0-6.0 mm immature seed as explants. Not only the kinds, concentrations and combinations of plant growth regulatory substances but also immature embryo length and inoculum density have main effects on the approaches of embryogenesis. The results of two-factors analysis of variance experiments showed that immature embryo length, plant growth substance concentration and basic medium type have very significant effects on the frequency of embryogenic response, furthermore, interactions exist between the former two factors and are just very significant(at 1% level). The best combinations between 2,4-D concentration and cotyledon length are 10 mg/L 2,4-D & 4.0 mm immature embryos, 20-40 mg/L 2,4-D & 5.0 mm immature embryo. Under these combinations, the salt composition of E1 are very significantly better than that of MS. In conclusion, in the regeneration system established by us the frequency of somatic embryogenesis from the soybean immature cotyledons is greater than 50% and the frequency of conversion of normal (not fused) somatic embryos is about 52.9%-62.6%.     

Somatic embryogenesis and plant regeneration from floral explants of cacao (Theobroma cacao L.) using thidiazuron

Summary A procedure for the regeneration of cacao (Theobroma cacao) plants from staminode explants via somatic embryogenesis was developed. Rapidly growing calli were induced by culturing staminode explants on a DKW salts-based primary callus growth (PCG) medium supplemented with 20 g glucose per L, 9 μM 2,4-D, and thidiazuron (TDZ) at various concentrations. Calli were subcultured onto a WPM salts-based secondary callus growth medium supplemented with 20 g glucose per L, 9 μM 2,4-D, and 1.4 nM kinetin. Somatic embryos were formed from embryogenic calli following transfer to a hormone-free DKW salts-based embryo development medium containing sucrose. The concentration of TDZ used in PCG medium significantly affected the rate of callus growth, the frequency of embryogenesis, and the number of somatic embryos produced from each responsive explant. A TDZ concentration of 22.7 nM was found to be the optimal concentration for effective induction of somatic embryos from various cacao genotypes. Using this procedure, we recovered somatic embryos from all 19 tested cacao genotypes, representing three major genetic group types. However, among these genotypes, a wide range of variation was observed in both the frequency of embryogenesis, which ranged from 1 to 100%, and the average number of somatic embryos produced from each responsive explant, which ranged from 2 to 46. Two types of somatic embryos were identified on the basis of their visual appearance and growth behavior. A large number of cacao plants have been regenerated from somatic embryos and established in soil in a greenhouse. Plants showed morphological and growth characteristics similar to those of seed-derived plants. The described procedure may allow for the practical use of somatic embryogenesis for clonal propagation of elite cacao clones and other applications that require the production of a large number of plants from limited source materials.     

Somatic embryogenesis from callus cultures of <Emphasis Type="Italic">Terminalia chebula</Emphasis> Retz.: an important medicinal tree

Somatic embryogenesis was obtained from cotyledon and mature zygotic embryo callus cultures of Terminalia chebula Retz. Callus cultures of cotyledon and mature zygotic embryo were initiated on induction medium containing Murashige and Skoog (MS) nutrients with 1.0 mg/l 2,4-dichlorophenoxyacetic acid (2,4-D) either 0.01 or 0.1 mg/l Kinetin and 30 g/l sucrose. Induction of somatic embryogenesis, proliferation and development was obtained through different culture passages. Embryogenic cotyledon callus with globular somatic embryos was obtained on MS basal medium supplemented with 50 g/l sucrose. Globular somatic embryos were observed from mature zygotic embryo callus on induction medium. Different stages of somatic embryo development from cotyledon and mature zygotic embryo calluses were observed on MS basal medium supplemented with 50 g/l sucrose after 4 weeks of culture. Histological studies have revealed the developmental stages of somatic embryos. A maximum of 40.3±1.45 cotyledonary somatic embryos/callus was obtained from mature zygotic embryo compared to 7.70±0.37 cotyledonary somatic embryos/callus initiated from cotyledons. Germination of somatic embryos and conversion to plants were achieved. Highest frequency of germination (46.66±0.88) of somatic embryos was obtained on MS basal medium containing benzyladenine (0.5 mg/l) with 30 g/l sucrose.     

Embryogenic response of multiple soybean [Glycine max (L.) merr.] cultivars across three locations

Summary Nine soybean [Glycine max (L.) Merr.] cultivars representing midwestern, mid-south, and southern US growing regions were evaluated at each of three locations (Athens, GA; Lexington, KY; and Wooster, OH) using uniform embryogenic induction and proliferation protocols in order to evaluate the portability of soybean somatic embryogenic protocols to different locations. The experimental design minimized variation between locations by having all cultivars present at all locations on all days. A quantitative weighted score for primary embryo induction was developed on average embryo number per explant and was used to describe non-embryogenic, poorly embryogenic, moderately embryogenic, and highly embryogenic responses. Ranking of cultivars remained similar across all locations, indicating a uniform transportability of the protocol, at least as far as embryo induction is concerned. Continued proliferation of embryogenic cultures was also measured using a repetitive growth measure but few meaningful conclusions could be made due to the high level of variability including inconsistent growth of cultures between each subculture. Overall, several cultivars were identified as being uniformly embryogenic or non-embryogenic at the primary induction phase at all locations, and we predict that those embryogenic cultivars could be used by any laboratory for high-efficiency induction of embryogenesis. The best of these cultivars, ‘Jack’, was uniformly responsive across all locations and should be selected as the genotype most likely to yield positive results when attempting to culture and genetically engineer soybeans via embryogenic protocols.     

Genetic improvement of the somatic embryogenesis and regeneration in soybean and transformation of the improved breeding lines

Somatic embryos of soybean [Glycine max (L.) Merrill] have been used to generate transgenic plants by particle bombardment. The induction and proliferation of somatic embryos from immature cotyledons are dependent on the genotype of the cultivar. Whereas somatic embryogenesis and plant regeneration are inefficient in most cultivars, they are efficient in the cultivar Jack. We previously established a breeding line, QF2, by the integration of null mutations of each subunit of the major seed storage proteins glycinin and β-conglycinin, but the embryogenic response of this line is insufficient to allow efficient transformation. We have now backcrossed QF2 to cultivar Jack in order to combine the null traits with competence for somatic embryogenesis. The backcrossed breeding lines selected on the basis of the absence of the major storage proteins exhibited an improved capacity for the induction and proliferation of somatic embryos compared with that of QF2. The induced somatic embryogenic tissue of these breeding lines was successfully used for the production of transgenic plants by particle bombardment. These results also indicate that somatic embryogenesis in soybean is genetically controlled and inherited in a manner independent of the null traits of the major seed storage proteins.     

Enhancement of American chestnut somatic seedling production

Somatic embryogenesis holds promise for mass propagation of American chestnut trees bred or genetically engineered for resistance to chestnut blight. However, low germination frequency of chestnut somatic embryos has limited somatic seedling production for this forest tree. We tested the effects of culture regime (semi-solid versus liquid), cold treatment, AC and somatic embryo morphology (i.e., cotyledon number) on germination and conversion of the somatic embryos. Cold treatment for 12 weeks was critical for conversion of chestnut somatic embryos to somatic seedlings, raising conversion frequencies for one line to 47%, compared to 7% with no cold treatment. AC improved germination and conversion frequency for one line to 77% and 59%, respectively, and kept roots from darkening. For two lines that produced embryos with one, two or three-plus cotyledons, cotyledon number did not affect germination or conversion frequency. We also established embryogenic American chestnut suspension cultures and adapted a fractionation/plating system that allowed us to produce populations of relatively synchronous somatic embryos for multiple lines. Embryos derived from suspension cultures of two lines tested had higher conversion frequencies (46% and 48%) than those from cultures maintained on semi-solid medium (7% and 30%). The improvements in manipulation of American chestnut embryogenic cultures described in this study have allowed over a 100-fold increase in somatic seedling production efficiency over what we reported previously and thus constitute a substantial advance toward the application of somatic embryogenesis for mass clonal propagation of the tree.     

Somatic embryogenesis in tamarillo (<Emphasis Type="Italic">Cyphomandra betacea</Emphasis>): approaches to increase efficiency of embryo formation and plant development

Somatic embryogenesis induction and somatic embryo development of the solanaceous tamarillo tree were previously established and successfully used for plant regeneration from different explants and varieties. Somatic embryogenesis was induced in Murashige and Skoog medium containing 2,4-dichlorophenoxyacetic acid (2,4-D) or picloram and high sucrose concentrations (0.25 M). The embryogenic tissues were transferred to an auxin-free medium, with reduced sucrose levels, to permit embryo development and conversion into plantlets. This two-step protocol is often impaired by an ineffective transition from the proembryogenic masses to embryo development. In this work, attempts to optimize the somatic embryogenesis system of tamarillo by improving the quality of somatic embryo and embryo conversion were carried out. The results showed that the presence of a high number of abnormal somatic embryos did not significantly inhibit plant conversion, hence indicating that shoot apical meristem development was not affected in abnormal somatic embryos. It was also shown that the manipulation of sucrose concentration in the development medium (0.11 M) and dark conditions before conversion increased the number of morphologically normal somatic embryos. The comparison between mature cotyledonary zygotic and somatic embryos showed an inefficient accumulation of storage compounds, mainly lipids, in somatic embryos. These reduced levels of lipid storage could be responsible for the abnormal patterns of embryo development found in tamarillo somatic embryos.     

Improved somatic embryogenesis from Cocos nucifera (L.) plumule explants

Summary Coconut is one of the most recalcitrant species to regenerate in vitro. Although previous research efforts using plumule explants have resulted in reproducible somatic embryogenesis, efficiency is only 4 or 10 somatic embryos per plumule without or with a brassinolide treatment, respectively. In order to increase the efficiency of somatic embryogenesis in coconut, two different approaches were evaluated and reported here: secondary somatic embryogenesis and multiplication of embryogenic callus. Primary somatic embryos obtained from plumule explants were used as explants and formed both embryogenic callus and secondary somatic embryos. The embrogenic calluses obtained after three multiplication cycles were capable of producing somatic embryos. The efficiency of the system was evaluated in a stepwise process beginning with an initial step for inducing primary somatic embryogenesis followed by three steps for inducing secondary somatic embryogenesis followed by three steps for embryogenenis callus multiplication, and finally production of somatic embryos from callus. The total calculated yield from one plumule was 98 000 somatic embryos. Comparing this to the yield obtained from primary somatic embryogenesis results in about a 50 000-fold increase. When compared to the yield previously reported in the literature with the use of a brassinolide treatment, it is about a 10 000-fold increase in yield. The present protocol represents important progress in improvement in the efficiency of coconut somatic embryo production.     

Regeneration Capacity of Calli Derived from Immature Embryos in Spring Barley Cultivars

Callogenesis, somatic embryogenesis and regeneration capacity in twenty-three agronomically important spring barley (Hordeum vulgare L.) cultivars on induction media with 2,4-dichlorophenoxyacetic acid (2,4-D) or 3,6-dichloro-o-anisic acid (dicamba) and on modified regeneration media were studied. The frequency of zygotic embryos exhibiting callogenesis varied from 88 to 100 % according to genotype. Dicamba was more suitable for somatic embryogenesis induction and exhibited a higher frequency of regenerants than did 2,4-D. Green regenerants were obtained in all cultivars, and there were no albino plants. Except for cv. Victor all cultivars used in the experiment showed lower regeneration capacity as compared to the model cv. Golden Promise. This revised version was published online in July 2006 with corrections to the Cover Date.     

Factors Affecting Somatic Embryogenesis Induction and Conversion in “Paradise Tree” (<Emphasis Type="Italic">Melia azedarach</Emphasis> L.)

Factors affecting somatic embryogenesis induction and conversion in paradise tree (Melia azedarach) were evaluated. Somatic embryogenesis was influenced by plant growth regulators, explant stage, carbohydrate source and concentration, gelling agents, light, and induction times. MS medium with 4.54 μM thidiazuron (TDZ) was optimal for the induction of embryogenic tissue. Zygotic embryos that were 1-1.5 mm long (torpedo and early cotyledonal stage) had a greater embryogenic response than smaller or larger embryos and better conversion of somatic embryos into plants. In general, embryos that formed in medium containing 1% or 5% carbohydrate were hyperhydrics or fused, respectively, whereas those that formed in medium with a carbohydrate concentration of 3% had better morphology. Raffinose at 3% yielded satisfactory somatic embryo induction with good morphology and the best values of conversion into plants. Induction and conversion of somatic embryos were superior on medium solidified with agar A-1296. The explants maintained under 160 μmol m⁻² s⁻¹ or 1 week in darkness and later 160 μmol m⁻² s⁻¹ produced a significantly higher embryogenic index. Only 4 days of treatment on induction medium, with either raffinose or sucrose at 3% as a carbohydrate source, were required to induce somatic embryogenesis, but longer exposure, until 18 days, increased the yield and improved the morphology of somatic embryos.     

Protocols for efficient repetitive and secondary somatic embryogenesis in Helianthus maximiliani (Schrader)

 Indirect somatic embryogenesis was induced on leaf explants of greenhouse-grown Helianthus maximiliani plants. Leaves of the regenerated plants were used as starting explants for the induction of direct somatic embryogenesis. Another cycle of somatic embryogenesis was induced on the leaves of regenerated plants. In both cases, leaf explants were cultured on media containing different auxin/cytokinin ratios. The auxin/cytokinin ratio had an influence on the intensity of embryo formation, germination and the capability to regenerate plants. Somatic embryogenesis was generally more intensive on the medium with lower concentrations of 6-benzylamino-purine. Further, the percentage of regenerated plants was higher when embryos were induced on high-cytokinin, low-auxin medium. Secondary somatic embryogenesis was induced on embryos by culture in liquid hormone-free medium. Similar to direct embryogenesis the efficiency of secondary embryogenesis depended on the medium used for the induction of the primary embryos. In contrast to the mostly low frequencies of conversion of secondary embryos into plants that has been observed in other species, the percentage of regenerated plants from secondary embryos of H. maximiliani was quite high, although slightly lower than that obtained in primary embryos. Received: 28 March 2000 / Revision received: 1 September 2000 / Accepted: 2 October 2000     

松柏类植物体细胞胚胎发生的研究进展

松柏类植物的体细胞胚胎发生既是繁育的一种手段,又是研究胚胎发育过程中结构、生理和分子事件的一种重要的模式系统。整个体细胞胚胎发生过程主要包括3个步骤：胚性组织的诱导和增殖、体细胞胚的成熟以及体细胞胚的萌发和转换。过去为了提高胚胎发育过程所做的努力主要都集中在胚的成熟阶段,这是因为一直认为能否成功再生的关键在于胚发育成熟阶段的处理。然而,在过去几年里,结合生理生化以及分子生物学的研究发现,胚胎发生的早期阶段对于完成整个发育过程也是至关重要的,早期阶段培养条件的优化可以显著提高培养过程中体细胞胚的数量和质量。此外,萌发过程培养条件的调节对于提高成熟体细胞胚的萌发率和转换率也很重要。因此,这些新的研究成果对于改善松柏类植物体细胞胚胎发生中的胚的诱导率和转换率低的现象具有重要的意义。     

影响大豆体细胞胚诱导因素的研究

体细胞胚的诱导是大豆体外再生的关键。基因型,诱导光周期,外植体的英位,蔗糖浓度等因素,可导致诱导频率及正常胚比例不同,影响植株再生。本研究选用黑龙江省主栽大豆基因型的未成熟子叶,在含高浓度生长素的MSB培养基上诱导体细胞胚产生。合丰25和东农7819为优选基因型,生育前期下部英位大小为2－4mm未成熟子叶体细胞胚发生效果最好;四种光周期下体细胞胚诱导频率相近,但连续弱光了正常胚比例高;NAA诱导优于2－4,D;10mg/1NAA与1．5％蔗糖配比组合最佳。     

Cloning adult trees of Arbutus unedo L. through somatic embryogenesis

Arbutus unedo L. is a perennial tree, native in the Mediterranean area, and tolerant to stress conditions. Due to its economic potential, there is an increasing demanding for plants by producers and farmers. In order to offer cloned material with assured quality, several micropropagation protocols have been developed, including somatic embryogenesis induction. However, little is known about this process on strawberry tree and a great deal of work is still necessary to successfully clone in A. unedo through somatic embryogenesis. Thus, the main goals of this work were: (i) to test the effect of the genotype on somatic embryogenesis induction, (ii) to analyse the role of adult and young materials on induction, and (iii) to perform a comparative histological analysis between somatic embryos and their zygotic counterparts. Somatic embryogenesis was induced on apical expanded leaves from in vitro shoots of several genotypes in Andersson medium with 3% sucrose and different concentrations of BAP (2.0 mg L^?1) and NAA (0.5, 1.0, 2.0, 5.0, 10.0, 15.0 and 20.0 mg L^?1). Embryogenesis induction rates ranged from 0 to 94.5%. Higher induction rates were achieved on the medium with 2 mg L^?1 BAP and 2 mg L^?1 NAA, and are genotype dependent. After a 3-month induction period, the highest somatic embryogenesis induction rate was 94.5% on genotype AU4. Embryos at different developmental stages were found, as well as abnormal somatic embryos. SEM images showed different anomalies being the most common embryos displaying more than two cotyledons or fused embryos. Embryo germination was not genotype dependent and the maximum embryo conversion rate achieved was 73.5%. However, only 39.21% of the embryos were able to grow into plantlets which displayed a normal chromosome number (2n?=?26). Histological analysis showed differences in the cell organization between somatic and zygotic embryos, as well as several morphological anomalies. Overall, the developed somatic induction protocol proved to be very efficient, with high induction rates achieved, both from seedling and adult material, but its genotype dependent. However, embryo conversion still needs to be improved, in order to fully seize the potential of this micropropagation technique.

     

Role of exogenous reduced nitrogen and sucrose in rapid high frequency somatic embryogenesis in Medicago sativa

The effect of exogenously supplied reduced nitrogen and sucrose on high-frequency somatic embryogenesis in petiole-derived tissue cultures of a diploid and a tetraploid regenerable clone of Medicago sativa ssp. falcata was investigated. There was an absolute requirement for ammonium during embryo induction and differentiation, with 5mM being the optimum for induction and 10–20 mM the optimum for differentiation of somatic embryos. Exogenous amino acids were not essential for differentiation and often even inhibitory, except 1 or 2 g/l casein hydrolysate or 4.4 mM glutamine with 3.1 mM proline which, under certain conditions, resulted in increases of 20–30% in the number of embryos obtained. High and low sucrose concentrations inhibited somatic embryogenesis and there was no reason to deviate from the 3% (0.088 M) sucrose level commonly used in plant tissue culture media. Selected clones from three M. sativa cultivars showed a response similar to the highly regenerable ssp. falcata clone F1.1.     

盐肤木体细胞胚胎发生及植株再生

以盐肤木(Rhus chinensis Mill.)幼胚为外植体,研究不同植物生长调节剂组合对其愈伤组织诱导及体细胞胚胎发生的影响,以建立盐肤木体细胞胚胎发生及植株再生体系。结果表明,最适愈伤组织诱导培养基为MS+6-BA 0.2 mg/L+2,4-D 1.0 mg/L,诱导率为84.57%,诱导出的初代愈伤组织白色或淡黄色,质地疏松,表面光滑,为非胚性愈伤。初代愈伤组织转移到1/2 MS+6-BA 2 mg/L+NAA 0.5 mg/L培养基上培养1个月后,长出淡黄色质地紧密的胚性愈伤组织,诱导率高达100%,在此培养基上胚性愈伤组织增殖倍数为854.73%。所获得的胚性愈伤组织转接到1/2 MS+6-BA 2 mg/L+NAA 0.5 mg/L+蔗糖4%的培养基上培养1个月后可诱导体细胞胚胎发生,诱导率可达32.67%。诱导得到的体细胞胚胎经历球形胚、心形胚、鱼雷胚、子叶胚进一步分化发育成苗。无菌苗炼苗后栽种到泥炭土∶蛭石∶珍珠岩为2∶1∶1的生长基质上,能100%稳定成活。经过细胞学观察分析,体细胞胚的发育与合子胚相似。     

松柏类植物体细胞胚胎发生的研究进展

松柏类植物的体细胞胚胎发生既是繁育的一种手段,又是研究胚胎发育过程中结构、生理和分子事件的一种重要的模式系统.整个体细胞胚胎发生过程主要包括3个步骤:胚性组织的诱导和增殖、体细胞胚的成熟以及体细胞胚的萌发和转换.过去为了提高胚胎发育过程所做的努力主要都集中在胚的成熟阶段,这是因为一直认为能否成功再生的关键在于胚发育成熟阶段的处理.然而,在过去几年里,结合生理生化以及分子生物学的研究发现,胚胎发生的早期阶段对于完成整个发育过程也是至关重要的,早期阶段培养条件的优化可以显著提高培养过程中体细胞胚的数量和质量.此外,萌发过程培养条件的调节对于提高成熟体细胞胚的萌发率和转换率也很重要.因此,这些新的研究成果对于改善松柏类植物体细胞胚胎发生中的胚的诱导率和转换率低的现象具有重要的意义.