Direct somatic embryogenesis, plant regeneration and in vitro flowering in rapid-cycling Brassica napus

 A simple method to induce somatic embryogenesis from seeds of rapid-cycling Brassica napus is described. Seedlings cultured on Murashige and Skoog (MS) basal medium produced somatic embryos directly on hypocotyls and cotyledons after 2 to 3 subcultures onto the same medium. A low pH of the medium (3.5–5) was more conducive to somatic embryogenesis than a higher pH (6 and 7). Embryogenic potential of the seeds was inversely correlated to seed age: about 41–68% of immature seeds between the ages of 14 and 28 days after pollination (DAP) formed somatic embryos compared to 0–11% of the seeds obtained 29–37 DAP. About 54% of the somatic embryos produced secondary embryos after subculturing onto the same medium. The embryogenic potential of the cultures has been maintained on MS basal medium for 2 years (12 generations) without diminution. Up to 75% of the secondary embryos developed into plantlets on MS medium enriched with 10^–6  M zeatin, and 40% of these produced flowers when transferred to an optimised flower-induction medium. Viable seeds were produced in self-pollinated in vitro flowers. Received: 15 February 2000 / Revision received: 18 July 2000 / Accepted: 19 July 2000     

Isolation of two genes that were induced upon the initiation of somatic embryogenesis on carrot hypocotyls by high concentrations of 2,4-D

 This study describes the formation of somatic embryos directly on the surface of hypocotyl sections of Daucus carota L. after exposure to 450 μM of 2,4-D for 2 h, followed by culturing without 2,4-D for 2 weeks. A search for differentially expressed genes immediately after the 2,4-D treatment resulted in the identification of two genes, Dchsp-1 and Dcarg-1. Dchsp-1 has homology to low-molecular-weight heat-shock proteins, while Dcarg-1 has homology to auxin-regulated genes. Dchsp-1 was expressed upon the exposure to 2,4-D treatment but also responded to general stress responses. Dcarg-1 responded primarily to auxin; however, a parallel relationship between the expression of Dcarg-1 and the formation of somatic embryos on the hypocotyl sections was observed. It seems the exposure to auxin shock could serve as a trigger in inducing cell division in the epidermal cells and promoting their further differentiation to somatic embryos. These results are discussed in relationship to our current understanding of the molecular basis of somatic embryogenesis. Received: 3 May 1999 / Accepted: 9 August 1999     

Induction of somatic embryogenesis in Pinus roxburghii Sarg.

Embryogenic calli were initiated from embryonic explants of Pinus roxburghii using female gametophytes containing immature pre-cotyledonary embryos. Zygotic embryos were collected at different developmental stages and cultured on various media. Initiation of embryogenic calli was achieved in pre-cotyledonary zygotic embryos of a 0.1-mm to 1.2-mm embryonal head on Douglus fir cotyledon revised medium (DCR) medium supplemented with 2,4-D or NAA and BA. Embryogenic callus development was initiated from the suspensor region of immature embryos. The method of immature embryo culture was significant as rapid embryogenic callus development occurred in megagametophytes where the suspensor was stretched onto the medium from the cut micropylar end. Sixty embryogenic lines were established from 2500 explants cultured during one season. A pro-embryo with six to eight meristematic cells and suspensor of six to ten long, vacuolated cells dominated the early phase of the callus development. Cleavage polyembryony occurred in proliferating callus, constituting a method of multiplication of these somatic embryos. Somatic embryos developed to stage-I and stage-II embryos on DCR medium supplemented with 5 μM 2,4-D or 10 μM NAA. Received: 30 June 1999 / Revision received: 15 November 1999 / Accepted: 3 December 1999     

柑桔原生质体融合再生叶肉亲本型植株的遗传分析

叶肉亲本（粗柠檬）型植株叶形指数、气孔特征与亲本粗柠檬无异,与同组合体细胞杂种差异显著。染色体计数为二倍体（２ｎ＝２ｘ＝１８）。过氧化物酶（ＰＯＸ）、多酚氧化酶（ＰＰＯ）、谷草转氨酶（ＧＯＴ）同工酶图谱与粗柠檬一致。ＲＡＰＤ分析表明,在具多态性的５４个随机引物中,大多数引物（５２个）上的图谱与粗柠檬相同。但ＯＰＷ－１２上,叶肉亲本型植株含有哈姆林甜检的特征谱带。ＯＰＶ－０４扩增产物显示,叶肉亲本型     

黔中喀斯特9种木质藤本叶功能性状研究

为揭示喀斯特生境中藤本植物的生态策略,对中国科学院普定喀斯特生态系统观测研究站的陈旗流域中9种木质藤本的叶片功能性状及其相关性进行了研究.结果表明,叶面积、叶厚度、叶绿素含量、比叶面积、叶组织密度和叶干物质含量6个叶功能性状均存在不同程度的变异,性状的种间变异为9.24％～98.18％,种内变异为0.64％～39.71...     

油茶优良无性系子叶体细胞胚植株再生

以油茶优良无性系‘湘林4号’子叶为外植体,采用附加不同种类激素的MS培养基对其进行组织培养实验。研究结果表明:子叶形成胚性愈伤组织的最适合培养基为MS+2.0mg.L-12,4-D+1.0mg.L-1KT;经胚状体诱导产生不定芽分化的最适合培养基为MS+2.5mg.L-16-BA+1.5mg.L-1IAA;油茶优良无性系的生根培养基以MS+7.0mg.L-1NAA最适;通过对植株再生过程中各阶段的组培材料进行RAPD鉴定分析表明,DNA水平上未发现变异,说明通过组织培养建立的油茶优良无性系再生植株同原无性系无明显差别,最终获得的组培苗木能够保持原无性系的优良特性,其遗传是稳定的。     

体细胞胚胎发生的分子机制及生理生化研究进展

本文较详细地综述了近年来体细胞胚胎发生的分子机制及生理生化研究进展,这些研究色括:DNA、RNA和蛋白质的合成;特异性胚性蛋白的研究;内源多胺代谢的改变;内源游离氨基酸及还原性小分子物质含量的改变;内源激素的改变以及几种酶的同工酶酶谱的改变;并指出了当前体细胞胚眙发生机理及生理生化研究巾存在的一些问题。     

枇杷叶片胚性愈伤组织诱导与内源激素含量的关系

为揭示胚性愈伤组织发生过程中内源激素的变化规律,本研究以枇杷叶片为实验材料,通过诱导胚性愈伤组织获得体细胞胚,采用高效液相色谱法测定枇杷叶片及愈伤组织的赤霉素（GA₃）、生长素（IAA）、脱落酸（ABA）和玉米素（ZT）4种内源激素的含量,探讨胚性愈伤组织发育过程中4种内源激素的动态变化。结果显示,不同成熟度叶片内IAA/ZT比值对胚性愈伤组织的发生有正效应,而GA₃/IAA的比值具有负效应。胚性愈伤组织的发生需要较低含量的GA₃及高含量的IAA和ABA,IAA/ZT比值高有利于胚性愈伤组织形成,培养后期及时添加一定量的外源激素有利于胚性保持。本研究可为离体培养时选择外植体、添加外源激素及控制继代时间提供理论指导,并为快速获得枇杷胚性材料、开展基因转化研究奠定基础。     

脱落酸与植物体细胞胚胎发生关系的研究进展

简要综述了植物体细胞胚胎发生过程中内源ABA水平及外源ABA对体细胞胚胎发生和发育的调节作用及其作用机制,并提出了未来的研究方向。     

泡沙参复合体（桔梗科）的物种生物学研究：Ⅰ表型的可塑性

表型可塑性是生物变异中由环境引起的一种变异,是植物适应的一种重要方式。对沙参属这样一个形态上复杂多变、分类上很难处理的类群,研究其表型可塑性不仅为探讨性状变异、判断其系统学意义及选择可靠的分类性状提供了有益的资料,而且有助于揭示沙参属植物变异、适应和进化的机制。本文从泡沙参复合体中选择了6个居群,利用播种和移栽试验,通过对不同个体和居群在一致条件下的表现及野外和移栽后的对比,对根、茎、叶、花和果等形态性状的表型可塑性进行了初步的观测分析。结果表明,一些叶片、花部和果实性状具有较大的发育可塑性,尤其是叶形、花萼裂片不仅发育变化大,而且随发育过程定向变化。环境可塑性较大的性状主要是根、茎、花序分枝等性状,而叶片、花部、果实和种子性状的环境饰变能力都较小。最后,对泡沙参复合体形态性状的变异从发育可塑性和环境可塑性的角度进行了讨论。