Genetic analysis of in vitro wheat somatic embryogenesis     

J. De Buyser  J. L. Marcotte  Y. Henry 《Euphytica》1992,63(3):265-270

Summary A spring wheat genotype which produces somatic embryos in vitro, after short and long-term culture, was tested for its ability to sexually transmit this embryogenic trait. Reciprocal crosses were performed between a embryogenic line and a nonembryogenic variety.Immature embryos were cultured on Murashige and Skoog medium plus 2 mg/l 2,4-dichlorophenoxyacetic acid, gelled with 5.5 g/l agarose. Somatic embryogenesis was not expressed in the F₁'s. In contrast, from several hundred immature embryos of the F₂ generation of one cross, 10.7% and 1.6% expressed somatic embryogenesis in short and long-term cultures respectively. These percentages of embryogenic: non-embryogenic fits a model of a few complementary genes. The embryogenic capacity of the F₂ genotypes depends on the presence of recessive alleles at these gene loci. The long-term wheat somatic embryogenesis capacity requires a more complex mechanism than the short-term one.Abbreviations CS Chinese Spring - Aq Aquila - E Embryogenic - NE Nonembryogenic - SC Subculture  相似文献   

Somatic embryogenesis in pea (Pisum sativum L. and Pisum arvense L.): Diallel analysis and genetic control     

M. Bencheikh  A. Gallais 《Euphytica》1996,90(3):257-264

Summary Six lines of Pisum were tested in vitro for their ability to produce somatic embryos from apices. Significant quantitative variation was observed. Inheritance of the ability to form somatic embryos was studied using a diallel cross among six different lines. About 80% of the observed genotypic variation was due to additive effects. There is a tendency for the favourable genes to be recessive. It appears that there are two genetic systems involved. Analysis of the distribution of F₃ families means from a cross among two extreme lines seems to indicate the presence of a few major genes in the control of somatic embryogenesis of pea.  相似文献   

The effect of in planta TIBA and proline treatment on somatic embryogenesis of sugar beet (Beta vulgaris L.)     

Behrouz Ehsani Moghaddam  Mahmoud Mesbah  Nasrin Yavari 《Euphytica》2000,112(2):151-156

The effect of in planta TIBA and L-proline onin vitro seedlings and cell culture of sugar beet was investigated. Sterilized seeds were grownin vitro on 1/2 MS medium supplemented with 0 or3 mg/l TIBA. Calli obtained on young leaves cultured on MS medium containing 1 mg/l BAP, were used for the initiation of cell suspension cultures using MS basal composition supplemented with 0 or 50 mM proline. Aliquots of 1 ml from cell suspension culture were inoculated onto the first somatic embryo induction MS medium containing TIBA 0.5 mg/l, BAP 1.0 mg/l, and proline at 0 or 50 mM. After three weeks of culture, embryogenic calli were transferred to the second embryo induction medium supplemented with NAA and BAP at 0.2 and 0.5 mg/l, respectively. The frequency of somatic embryos of calli obtained from in plantaTIBA together with proline treatments on average was20 which was higher than that of the other treatments. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

The sulphur-rich Brazil nut 2S albumin is specifically formed in transgenic seeds of the grain legume Vicia narbonensis     

I. Saalbach  T. Pickardt  D. R. Waddell  S. Hillmer  O. Schieder  K. Müntz 《Euphytica》1955,85(1-3):181-192

Summary Epicotyl explants were co-cultivated with Agrobacterium tumefaciens EHA101 to transfer a chimeric 2S albumin gene construct carried in the binary Ti plasmid vectors pGSGLUC1 or pGA472 into the grain legume Vicia narbonensis. This gene encoding the sulphur-rich Brazil nut albumin was under the control of either the CaMV 35S promoter which permits gene expression in all organs, or the Vicia faba legumin B4 promoter which elicits seed-specific gene expression. After callus formation and selection for kanamycin resistance, somatic embryos were induced which, in the case of transformation with the vector pGSGLUC1, were screened for GUS activity. Embryos that produced GUS were in addition analysed for 2S albumin formation. Selected transgenic embryos were cloned by multiple shoot regeneration. Rooted and fertile plants were obtained by grafting transgenic shoots on the appropriate seedlings. R₁ and R₂ generations were raised and analysed for GUS as well as 2S albumin gene expression.Expression of the 35S promoter/2S albumin gene fusion took place in all organs of the transgenic plants including the cotyledons of seeds, whereas seed-specific gene expression was found in transformants with the legumin promoter/2S albumin gene fusion. The 2S albumin accumulated in the 2S protein fraction of transgenic seeds and its primary translation product was processed into the 9 and 3 kDa polypeptide chains. The foreign protein was localised in the protein bodies of the grain legume. Analysis of the R₂ plants indicated Mendelian inheritance of the 2S albumin gene. In homozygous V. narbonensis plants the amounts of 2S albumin were twice that present in the corresponding heterozygous plants. Whereas only low level formation of the foreign protein was achieved if the gene was under the control of the 35S promoter, approximately 3.0% of the soluble seed protein was 2S albumin if seed-specific gene expression was directed by the legumin B4 promoter. Some of these transformants exhibited a three-fold increase in the methionine content of the salt-soluble protein fraction extracted from seeds.Abbreviations 35S cauliflower mosaic virus 35S protein gene - GUS -glucuronidase - NPTII neomycin phosphotransferase II - LeB4 Vicia faba legumin B4 gene - 2S albumin Brazil nut (Bertholletia excelsa) 2S albumin - ER endoplasmic reticulum - rER rough endoplasmic reticulum - HPLC high pressure liquid chromatography  相似文献   

High frequency somatic embryogenesis with a pampeana-derived genotype of alfalfa (Medicago sativa L.)     

María Valeria Romagnoli  Juan Pablo A. Ortiz  Gerardo D. Cervigni  Cintia Heisterborg  Rubén H. Vallejos 《Euphytica》1996,90(1):89-93

Summary Somatic embryos of genotype R11 of the alfalfa variety Pampeana were produced from embryogenic calli derived from leaf sections. They were induced by an auxin shock and its development was attempted on six different media. The best condition for somatic embryo production was inducing callus on MS medium plus 10 M 2,4-D and 4,6 M KIN and transferring them, after the auxin shock, to MS with 10–20 mM NH₄ ⁺ and 30 mM proline. More than 500 somatic embryos per plate were produced. Embryos were grown to plants on MS or half strength MS media and all regenerated plants resembled the original R11 genotype. This technique could be useful in alfalfa Pampeana improvement using genetic modification.  相似文献   

棉花高效体细胞胚发生及同步控制培养体系研究   总被引：1，自引：0，他引：1  

曹景林  张献龙  金双侠  杨细燕  朱华国  付莉莉 《作物学报》2008,34(2):224-231

棉花体细胞胚胎发生的频率低, 且体细胞胚的发育存在着不同步性, 给体细胞胚胎发生发育过程的生理学、生物化学和分子生物学的研究带来许多困难。本研究以陆地棉品种Coker201为材料, 建立了一种简单有效的棉花体细胞胚高频率发生和同步发育的培养体系。经过多次继代获得的胚性愈伤, 首先在液体培养基中振荡培养2 d使其分散, 然后过30目筛去除大的颗粒, 重新悬浮于同样的液体培养基中。悬浮培养14 d后, 过50目筛, 将筛上的胚性愈伤重悬浮于新鲜的培养基中, 并用吸管吸取悬浮液, 将其均匀地接种在表面垫有滤纸的同成分固体培养基(附加2.46 mmol L^-1 IBA和0.70 mmol L^-1 kinetin)上。培养21 d后, 用垫有滤纸的相同的固体培养基继代培养。利用这种培养体系, 获得的体细胞胚数量分别是单纯悬浮培养和固体培养(不垫滤纸)的16.5倍和4.0倍。其中, 球形胚、鱼雷形胚和子叶胚的同步发生率分别为70.2%、52.3%和73.0%。  相似文献   

An in vitro assay for drought-tolerant coconut germplasm     

Seetha Karunaratne  Sunil Santha  A. Kovoor 《Euphytica》1991,53(1):25-30

Summary The feasibility of developing an in vitro technique for screening drought-tolerant coconut germplasm has been investigated. Embryos excised from mature nuts of Sri Lanka-tall coconut were cultured as described previously. Water-stress in the culture system was progressively increased with each passage, by incorporating polyethylene glycol (PEG-6000), mannitol and sodium chloride into the culture medium. PEG and mannitol were observed to be growth inhibitory in action event at low concentrations and these two compounds were abandoned. In NaCl-stressed media, about 21% of randomly selected Sri Lanka-tall embryos died before reaching the 170 mM NaCl. About 78% survived 170 mM NaCl and only 12.6% were able to resist 320 mM NaCl. When zygotic embryos derived from two known drought-susceptible cultivars of coconut, CRIC-65 and Dwarf (from pumila) were tested using the same technique, 29% and 73% of embryos respectively died due to stress damage caused by 170 mM NaCl and none of either cultivar survived a salt concentration above 230 mM.However, embryos originated from two putative drought-tolerant cultivars showed a higher survival rate when subjected to salt stress. At 170 mM NaCl, all the embryos had developed into seedlings. In fact, percent germination of embryos was somewhat higher in 170 mM NaCl than in the control, that was devoid of NaCl. However, percent survivors gradually dropped with increase in salt concentration and about 18% survived the 330 mM NaCl. The technique seems to have great potential in screening drought-tolerant coconut germplasm.  相似文献   

Callus formation and plantlet regeneration from immature Triticum durum Desf. embryos     

A. Bennici  L. Caffaro  R. M. Dameri  P. Gastaldo  P. Profumo 《Euphytica》1988,39(3):255-263

Summary Experiments upon in vitro culture of immature durum wheat embryos, harvested at different growth stages, were made in two consecutive years. Callus formation and plantlet regeneration were obtained. The ability to form callus and the degree of morphogenetic processes varied with the different hormonal treatments used and with the age of the embryos. In the first year the best response for callus growth was observed with 2,4-D 2 mg l^-1 plus adenine 50 mg l^-1 or 2,4-D 5 mg l^-1 alone in the more mature embryos (15 and 20 days after anthesis). On the contrary, NAA 5 mg l^-1 had a greater shoot regeneration effect. In the next year, at all 2,4-D concentrations and for the two different ages of the embryos tested, all embryos formed callus. Regeneration of plantlets was obtained in higher percentage in calli originated from the more developed embryos. The effect of changed media upon plantlet regeneration was studied after callus transplant.Investigation by cytophotometry and chromosome counts on different calli showed, practically in all cells, a diploid condition. A histological analysis demonstrated embryogenic somatic characteristics in many samples of callus. The pattern of organogenesis seemed to be via adventitious bud formation but structures resembling embryoids were also observed in the callus.  相似文献   

Direct as well as indirect somatic embryogenesis from immature (unemerged) inflorescence of a minor millet Paspalum scrobiculatum L.     

Vikrant  A. Rashid 《Euphytica》2001,120(2):167-172

Somatic embryos differentiated directly on the rachis of immature inflorescences of Paspalum scrobiculatum L. cv. PSC 1 on culture to MS or N₆ medium supplemented with different concentrations (4.5–22.5 μM) of 2,4-dichlorophenoxyacetic acid (2,4-D). Direct embryogenesis on the rachis of inflorescence explants forms the first instance in graminaceous plants. Highest frequency of direct embryogenesis (34%and 30% cultures, respectively) was possible on N₆ medium supplemented with 4.5 μM of 2,4-D and MS medium fortified with9.0 μM of 2,4-D. Other tissues of the explant, floral-primordia, only after an initial phase of callusing differentiated into somatic embryos; indirect embryogenesis. Somatic embryogenesis, direct as well as indirect, was resolved by scanning electron microscopy. The somatic embryos germinated and developed into plantlets on regeneration medium. Interestingly, one week incubation of somatic embryos on activated charcoal (0.5%) fortified basal medium, supported high potential for ‘germination’ on transfer to charcoal-free basal medium. This beneficial effect of activated charcoal on regeneration of somatic embryos into plantlets is the first record in the Gramineae. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

棉花多胺HPLC的测定方法优化及其在体细胞胚胎发生过程中的变化规律     

程文翰  朱华国  李鹏飞  王凡龙  朱守鸿  赵兰杰  郭丽雪  孙杰 《棉花学报》2014,26(2):138-144

利用HPLC法测定棉花组织培养物中的多胺含量,以棉花品种新陆早33号愈伤组织为材料进行多胺含量的测定,结果表明:冰浴浸提时间及衍生反应时间优化后,可将内源腐胺(Putrescine,Put)、亚精胺(Spermidine,Spd)、精胺(Spermine,Spm)在15 min完全分离并定量测定,线性关系良好(r0.99),回收率高(96.8%~103.1%);建立了棉花多胺HPLC测定方法。利用该方法对棉花体细胞胚胎发生各时期培养物进行多胺含量测定,结果显示胚性愈伤组织形成后多胺含量显著上升,且腐胺与亚精胺和精胺的比例随着体细胞胚胎发生持续下降,表明非胚性细胞向胚性细胞转化过程中,二胺(腐胺)不断向三胺(亚精胺)和四胺(精胺)转化,特别是在胚状体形成期,亚精胺和精胺的积累显著增加,初步揭示了棉花体细胞胚胎发生过程中多胺的变化规律。  相似文献   

Influence of genotype and culture medium on callus formation and plant regeneration from immature embryos of Triticum turgidum Desf. cultivars   总被引：2，自引：0，他引：2  

J. M. González    E. Friero  N. Jouve   《Plant Breeding》2001,120(6):513-517

Twelve durum wheat cultivars were evaluated for their response to in vitro tissue culture. Zygotic immature embryos were used to induce callus formation using four different Murashige and Skoog‐based media. Each contained 9.05 μM 2,4‐dichlorophenoxy acetic acid but differed in their carbon source (sucrose or maltose) and the presence of NaCl (0 mM or 40 mM). The influence of both genotype and medium on the type and percentage of callus produced was observed. Calli were either compact and frequently embryogenic, or soft and watery. Percentages ranged from 54 to 100%, depending upon genotype and induction medium. All calli were then plated on a regeneration medium containing 20 g/l sucrose, 2.68 μM 1‐naphthaleneacetic acid and 2.22 μ 6‐benzylaminopurine. The regeneration of plantlets was higher from compact than from soft calli, with a strong dependence on genotype and type of induction medium used. MSm induction medium (30 g/l maltose) and MS40s (30 g/l sucrose plus 40 mM NaCl) were best for inducing compact calli, and gave the highest proportion of regenerated plants. The in vitro response (number of total shoots from a compact callus/number of embryos plated) was higher for immature embryos of ‘Baztan’, ‘Bradano’ and ‘Don Pedro’. These cultivars are a good starting material for experiments involving transformation of calli from zygotic immature embryos.  相似文献   

Interspecific hybrids of Cucumis metuliferus × C. anguria obtained through embryo culture and somatic embryogenesis     

George Fassuliotis  B. V. Nelson 《Euphytica》1988,37(1):53-60

Summary Interspecific crosses between Cucumis metuliferus Naud. and C. anguria L. were obtained through embryo culture. Embryos in the rabbit-ear to advanced fluke-shaped stages were rescued 34–99 days after pollination. Plants were obtained through direct embryo culture, and through somatic embryogenesis from immature embryos. For direct embryo culture, fluke-shaped embryos were stored in sterile water in darkness for three days at 25C prior to transfer on Murashige and Skoog (MS) culture medium plus 1.0 M 6-benzylamino-purine. Multiple plants were obtained from single embryos through somatic embryogenesis of rabbit-ear stages on MS plus 10 M indole-3-acetic acid and 5 M 6-benzylamino-purine. Evidence of hybridization included leaf shape intermediate between the two parents, penduncle shape prior to fertilization which resembled the male parent, low pollen viability and isoelectric focussing of protein bands for acid phosphatase of leaf extracts.  相似文献   

Study of the variation in the somatic embryogenesis ability of some pea lines (Pisum sativum L. and Pisum arvense L.)     

M. Bencheikh  A. Gallais 《Euphytica》1996,90(3):251-256

Summary Thirty lines of pea were tested in vitro to evaluate their ability to produce somatic embryos. Three distinct genotypic classes were detected (strong, medium and weak). The best responses were obtained in Pisum sativum. Abnormal somatic embryos and secondary embryogenesis seem to constitute the principal obstacle to the development of these structures.  相似文献   

Monitoring genetic fidelity vs somaclonal variation in Norway spruce (Picea abies) somatic embryogenesis by RAPD analysis     

Berthold Heinze  Josef Schmidt 《Euphytica》1955,85(1-3):341-345

Summary Somaclonal variation, which is a welcome source of genetic variation for crop breeding, is unwanted when direct regenerants have to be used in tissue culture mass propagation (eg. in many forest trees), or in the regeneration of genetically transformed plants. Random amplified polymorphic DNA (RAPD) was used to analyse somatic embryos and plants regenerated from embryogenic cell lines in Norway spruce, Picea abies (L.) Karst. RAPD facilitated the identification of clones, as material from the same cell lines shared identical patterns of amplified fragments, whereas regenerants from different cell lines were easily distinguishable by their respective patterns. For comparisons with explant donor genotypes, cell lines were initiated from cotyledons. Some of the seedlings that had parts of their cotyledons removed were grown on as control plants. Somatic embryos regenerated from cotyledon cell lines showed no aberrations in RAPD banding patterns with respect to donor plants. We conclude that gross somaclonal variation is absent in our plant regeneration system.Abbreviations ESM embryogenic suspensor mass - RAPD random amplified polymorphic DNA - RFLP restriction fragment length polymorphism - (2,4-dichlorophenoxy)acetic acid 2,4-D - 1-naphthaleneacetic acid NAA  相似文献   

Combining abilities of in vitro traits in wheat (Triticum aestivum L.) immature embryo cultures     

M. N. Barakat 《Euphytica》1994,76(3):169-175

Summary Combining ability for six in vitro culture traits in wheat were studied in a 8×8 diallel cross (excluding reciprocals). Specific combining ability effects (sca) were significant for all six traits derived from immature embryos on two media protocols, whereas general combining ability (gca) variances were significant only for five of them. Furthermore, based on ratios obtained by comparing the ratio of K² gca to K² sca, sca was more important than gca for all six traits. Genetic correlations between shoot formation and other in vitro traits, except callus weight and root formation, were higher in magnitude than the corresponding phenotypic correlations estimates, indicating the importance of genetic effects.  相似文献   

In vitro tetraploid induction via colchicine treatment from diploid somatic embryos in grapevine (Vitis vinifera L.)     

X. M. Yang  Z. Y. Cao  L. Z. An  Y. M. Wang  X. W. Fang 《Euphytica》2006,152(2):217-224

A protocol for in vitro induction of tetraploids via colchicine-treated somatic embryos from immature zygotic embryos of diploid grapevine (Vitis vinifera L.) is reported. Embryogenic callus was initiated from immature zygotic embryos cultured on Nitsch and Nitsch (NN) medium supplemented with 1.0 mg/l 2,4-dichlorophenoxyacetic acid (2,4-D). The callus was transferred to NN medium containing 1.0 mg/l α-naphthalene acetic acid (NAA) and 0.5 mg/l benzyladenine (BA) to establish somatic embryogenesis. The vigorously growing globular embryos were selected and treated by 0, 10 or 20 mg/l colchicine for 1, 2 or 3 days, and then immediately transferred to NN medium supplemented with 0.03 mg/l NAA and 0.5 mg/l BA, for somatic embryo conversion and plant regeneration. The number of surviving embryos and regenerated plantlets following colchicine treatment decreased with increasing colchicine concentration and treatment time. Among 29 randomly investigated plantlets regenerated from colchicine-treated somatic embryos, five solid tetraploids (2n = 4× = 76) were identified by chromosome counting analysis; all others were diploid (2n = 2× = 38). Ploidy level of plant regenerated was also determined from leaves using flow cytometry. No chimeras with both 2C and 4C nuclei was produced from colchicine-treated somatic embryos. Significant differences in leaf stomata parameters were observed between diploid and induced tetraploid plantlets.  相似文献   

Fertile maize lines obtained from isolated microspores     

B. Szarka  M. Dévényi  S. Mórocz 《Euphytica》2001,122(1):53-60

Microspore response of three- way cross maize hybrid genotype 3AL/95 (Zea mays L.) was studied under simplified isolation and culture conditions. Fertile plant production was achieved through abundant plant regeneration. As a total, microspores of 160 tassels were inoculated and five sustainable microspore derived callus cultures (SMC) were obtained. Hybrid seeds (ML SC), which were produced by crossing of regenerates from two SMCs, gave rise to subsequent vigorous and fertile progeny. The response of the 3AL/95 and ML SC microspores was studied in three liquid culture media in order to improve the early viability of microspores. Them N6M medium provided better survival of cultured microspores (p = 5%) than the ppN6M/89 and the YPM-G media. The pH 5.8 in mN6M medium revealed significant increase (p = 1%) in microspore viability as compared to pH 3.0. The ML SC microspores showed higher viability(30%) on the first day of culture in the mN₆M than those of the3AL/95 (19%) but without improved rate of callus formation and plant regeneration. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

Nuclear DNA content and in vitro induced somatic polyploidization cassava (Manihot esculenta Crantz) breeding     

F. Awoleye  M. van Duren  J. Dolezel  F. J. Novak 《Euphytica》1994,76(3):195-202

Summary The diploid (2C) amount of DNA in cassava (Manihot esculenta Crantz) is 1.67 picograms (pg) per cell nucleus. This value corresponds to 772 mega-base pairs in the haploid genome. The size of the nuclear genome in cassava is very small in comparison with other Angiosperms. Flow cytometry techniques were used to screen ploidy levels in a large population of in vitro plantlets treated with colchicine and oryzalin (3,5-dinitro-N⁴,N-dipropylsulphate). Culture of axillary node cuttings for 48 hours in liquid medium supplemented with 2.5 to 5.0 mM colchicine in combination with 2% dimethyl sulfoxide (DMSO) resulted in a high frequency (23 to 42%) of non-chimeric tetraploids in the V₃ generation. Although mixoploidy may persist in as many as four cycles of vegetative propagation of node cuttings, solid (non-chimeric) tetraploids can be identified by flow cytometry among in vitro plantlets and then rapidly propagated for field testing. A somatic polyploidization system is proposed for implementation in cassava breeding programmes.Dedicated to the memory of the late Dr. Novak. Correspondence to M. van Duren  相似文献   

Analysis of tissue culture-derived variation in pea (Pisum sativum L.)-preliminary results     

Miroslav Griga  Jaromír Stejskal  Karel Beber 《Euphytica》1955,85(1-3):335-339

Summary The possibility of producing agronomically-useful somaclones via organogenesis and somatic embryogenesis from callus cultures of pea (Pisum sativum L.) was studied. Organogenic calli were induced from immature leaflets on MSB medium with NAA and BAP. Embryogenic calli were derived either from immature zygotic embryos (using 2,4-D) or from shoot apices (using picloram) of aseptically-germinated seedlings.The seed progenies (T₁ to T₃-generation) of primary regenerants were grown in field conditions and their phenotypic variation was evaluated and compared with control, non-tissue culture-derived plant material. In addition, electrophoretic analyses of selected isoenzyme systems and total proteins have been done. The results do not show dramatic changes in qualitative and quantitative traits. The evaluation of at least two future generations (T₄, T₅) is planned.Abbreviations BAP 6-benzylaminopurine - IBA indole-3-butyric acid - MSB medium (mineral salts after Murashige & Skoog, 1962, vitamins after Gamborg et al., 1968) - NAA -naphthalene-acetic acid, picloram-4-amino-3,5,6-trichloro picolinic acid - 2,4-D 2,4-dichlorophenoxyacetic acid - ORG organogenesis - SE somatic embryogenesis  相似文献   

Embryo rescue in Rosa hybrida L.     

Serge Gudin 《Euphytica》1993,72(3):205-212

Summary Two crosses between Rosa hybrida L. cultivars, that fail to produce progenies by conventional means, were carried out. In one of them, total hip abscision occured seven weeks after pollination; in the other one, only 2% of the fertilized hips remained on the plants after eleven weeks. Four- and five-week-old fertilized ovules were isolated in the first cross and six-week-old embryos in the second. The ovules were cultured on six media which differed in their mineral salt and sucrose concentrations while the embryos were cultured on only one of these media and eventually cold treated for one month at 4° C before being placed in a culture room set at 23° C. The embryos that had been isolated in ovulo when they were still not visible under a binocular lens developed atypically. The embryos isolated in ovulo when they were heart-shaped and on average 0.27 mm long performed in ovulo germination on some media and/or enlargement on all of them after two weeks; after another two week culture, once isolated from the ovule, all of them germinated. The cultured isolated embryos, that were exposed to cold, enlarged and germinated more rapidly when placed at 23° C than those not exposed to cold. Furthermore, the plantlets resulting from untreated embryo germination were characterized by large cotyledons which were only partially green. These results are discussed in regard to embryogenesis, precocious germination and dormancy.  相似文献