桃儿七种子休眠解除过程中细胞壁代谢及种皮超微结构的变化北大核心CSCD

为探究低温层积过程中桃儿七种子细胞壁代谢及种皮超微结构与休眠解除的内在联系,该研究通过低温层积解除桃儿七种子休眠,分析休眠解除过程中种子不同部位细胞壁组分及相关代谢酶的变化,同时利用扫描电镜对种皮的超微结构进行观察。结果表明,(1)桃儿七种皮主要由角质层、栅状石细胞层及海绵组织层3层构成,在层积过程中,种皮内部的海绵组织逐步疏松膨胀,种皮表面破损加剧;(2)种子不同部位的细胞壁组分具有明显差异,整个层积过程中,种胚、种皮和胚乳中的纤维素含量均在层积中期(45 d和60 d)降至最低,3个部位的纤维素酶活性在层积中期对应升高;种胚和种皮内的半纤维素含量均在层积中期显著下降,种皮中甘露聚糖酶活性和木糖苷酶活性在层积中期时相应达到最大;3个部位的果胶含量均在层积后期(75 d和90 d)时显著下降,而种皮和胚乳中多聚半乳糖醛缩酶活性也在层积后期相应升高;(3)种胚和胚乳内过氧化物酶活性在层积75 d和90 d时明显下降,而SOD活性在此时显著上升。(4)种子不同部位3种木质素单体的组成比例具有明显区别,同时3种木质素单体含量均随层积时间的延长而显著降低,且胚乳和种皮中的S-木质素含量对种子萌发存在显著的负向影响关系。研究认为,在低温层积过程中,桃儿七种子内细胞壁组分纤维素、半纤维素及木质素的逐步酶解,活性氧作用下的细胞壁松弛以及海绵组织层的疏松膨胀和种皮的破裂,破坏了细胞壁的刚性结构,促使种子机械束缚力降低,吸水性能提高、胚根生长能力增强,最终导致其休眠解除。     

赤霉素对紫斑牡丹种子下胚轴萌发及其种皮和胚乳结构的影响

以紫斑牡丹种子为试验材料,考察不同浓度赤霉素(GA_3)处理下种子生根情况,同时对其种皮纹饰进行了扫描电镜(SEM)观察,并对胚乳结构进行了荧光倒置显微镜、透射电镜(TEM)观察,以揭示GA_3对紫斑牡丹种子下胚轴解除休眠过程中种子种皮、胚乳结构变化和生根的影响。结果表明:(1)GA_3处理能够促进紫斑牡丹种子生根,以300 mg/L GA_3处理的种子生根效果最好,与对照相比可提前14.66 d生根,生根率可达62.33%。(2)扫描电镜观察发现,紫斑牡丹种皮表面含有蜡质,种子萌发进程中蜡质明显不断增加,种皮表面网眼逐渐消失,种皮皱缩明显。(3)光学显微镜观察发现,GA_3处理的紫斑牡丹种子胚乳细胞中含有较多淀粉体和蛋白体,并随着种子萌发进程逐渐积累,可为种子萌发提供足够的养分。(4)透射电镜观察发现,GA_3处理的紫斑牡丹种子胚乳细胞内大分子营养物质不断降解,线粒体、内质网、高尔基体等细胞器相继出现,种子下胚轴休眠解除,细胞壁较薄后期消融,利于营养物质传送。研究认为,适宜浓度GA_3处理可有效加快紫斑牡丹种皮结构的改变和胚乳细胞内物质代谢进程,促进种子萌发,且300 mg/L GA_3处理紫斑牡丹种子24 h可以获得最好的生根效果。     

A Seed Coat Bedding Assay to Genetically Explore In Vitro How the Endosperm Controls Seed Germination in Arabidopsis thaliana

The Arabidopsis endosperm consists of a single cell layer surrounding the mature embryo and playing an essential role to prevent the germination of dormant seeds or that of nondormant seeds irradiated by a far red (FR) light pulse. In order to further gain insight into the molecular genetic mechanisms underlying the germination repressive activity exerted by the endosperm, a "seed coat bedding" assay (SCBA) was devised. The SCBA is a dissection procedure physically separating seed coats and embryos from seeds, which allows monitoring the growth of embryos on an underlying layer of seed coats. Remarkably, the SCBA reconstitutes the germination repressive activities of the seed coat in the context of seed dormancy and FR-dependent control of seed germination. Since the SCBA allows the combinatorial use of dormant, nondormant and genetically modified seed coat and embryonic materials, the genetic pathways controlling germination and specifically operating in the endosperm and embryo can be dissected. Here we detail the procedure to assemble a SCBA.     

Seed germination and dormancy: The classic story,new puzzles,and evolution

This review highlights recent progresses in seed germination and dormancy research.Research on the weakening of the endosperm during germination,which is almost a classic theme in seed biology,was resumed byα-xylosidase studies.Strong genetic evidence was presented to suggest that the quality control of xyloglucan biosynthesis in the endosperm(and the embryo)plays a critical role in germination.Further analyses on the endosperm and the adjace nt layers have suggested that the cutin coat in the endosperm-testa interphase negatively affects germination while the en dosperm-embryo in terphase produces a sheath that facilitates germination.These progresses significantly advanced our understanding of seed germination mechanisms.A breakthrough in dormancy research,on the other hand,revealed the unique abscisic acid signaling pathway that is regulated by DELAY OF GERMINATION1(DOG1).The detailed analysis of DOC1 expression uncovered the intriguing story of reciprocal regulation of the sensean tisense pair,which gen erated new questions.Recent studies also suggested that the DOG1 function is not limited to dormancy but extended through general seed maturation,which provokes questions about the evolution of DOG1 family proteins.Seed biology is becoming more exciting with the classic stories being revitalized and new puzzles emerging from the frontier.     

曼陀罗种子休眠机理与破眠方法研究

通过对曼陀罗种子生活力测定、发芽试验、吸水率测定及种子萌发抑制物研究,揭示曼陀罗种子休眠机理,并利用物理、化学法处理曼陀罗种子,以探寻打破曼陀罗种子休眠的最佳方法.结果表明:(1)新采收的曼陀罗种子为综合休眠,休眠原因包括:种皮障碍、缺少萌发所需激素以及种皮和种仁中存在萌发抑制物,其中种皮障碍是限制种子萌发的首要因素.(2)室温存储6个月可解除曼陀罗种子种仁的休眠,但种皮障碍始终是其种子萌发的限制因素.(3)机械摩擦、浓H2SO4处理和NaOH处理均可打破除曼陀罗种皮的休眠障碍,促进种子萌发,其中用10% NaOH处理90 min为破除曼陀罗种皮休眠障碍的最佳方法,且发芽率比对照提高了83%.     

红松种子休眠与种皮的关系

本文探讨红松(Pinus koraiensis)种子休眠与其种皮之间的关系。夹破中种皮后,种子萌发率很低。在离体胚培养基中外加 ABA 及经 ABA 溶液浸泡种子的萌发实验表明,ABA也不是导致休眠的关键因素。试验确认红松种子存在透气障碍,即中、内种皮对氧气的进入都有阻碍作用。经低温砂藏后,种皮的阻碍作用明显减小。种皮的透气性障碍可能是诱导休限的主导因素。     

Olive embryo in vitro germination potential: role of explant configuration and embryo structure among cultivars

The in vitro germination of excised embryos can break dormancy rapidly and shorten the time required to produce seedlings, speeding up olive breeding programmes as well as rootstock production. In this study, the in vitro germination potential of four Sicilian olive cultivars was evaluated during two years of experiments, using explants with three different morphological configurations that represent three different degrees of embryo exposure: (1) intact stoneless seeds containing the embryo, the endosperm and the seed coat (Emb+En+SC), (2) seeds without the seed coat (Emb+En) and (3) naked, isolated embryos (seed coat and endosperm both removed: Emb). Differences were found in the germination percentages and timing due to both genotype and explant type. The root and shoot meristems, the radicle-hypocotyl axis, the provascular tissues and embryo storage reserves were identified as embryo anatomical structures which could influence germination capacity. Observation of these structures, however, indicated similar germination potential among cultivars, suggesting possible differences in other dormancy factors. In spite of variation in cultivar performance, after 60 days of in vitro culture all cultivars demonstrated the highest germination of naked embryos (explant type 3) and lowest for stoneless seeds (explant type 1); stoneless seeds without the seedcoat (explant type 2) showed intermediate germination percentages.     

准噶尔山楂种壳、种皮、种胚特性与种子休眠的关系

以准噶尔山楂种子为试验材料,检测其种壳和种皮的透水性及超微结构、种胚休眠特性及种子浸提液的抑制作用。结果表明：（1）准噶尔山楂种子具有胚休眠特性,种壳存在一定的机械束缚和透水障碍,存在内源抑制物质是引起准噶尔山楂种子休眠的主要原因。（2）酸蚀处理能使种壳表面结构破损,角质层脱落,种壳变薄,栅栏组织结构和细胞排列未发生变化,种孔增大,种子表面出现裂缝,但并不影响种子生活力。（3）准噶尔山楂种子甲醇浸提液的生物测定结果说明,准噶尔山楂种子的种壳、种皮和种胚均含有内源抑制物质,不同部位浸提液对白菜种子的发芽率、根长和苗高的抑制作用不同。     

濒危植物巴东木莲种子休眠与萌发特性的研究

巴东木莲(Manglietia patungensis)为我国特有种, 属国家重点保护植物。为找出其生殖环节中的致危因素, 作者对巴东木莲种子休眠与后熟过程中的形态和萌发特性进行了研究。结果表明, 巴东木莲种胚发育不完全可能是种子休眠的主要原因, 在其后熟过程中胚不断分化、发育成熟; 种皮具有较好的透性, 与休眠的关系不大; 种子不同部位均存在萌发抑制物, 胚乳中高含量的萌发抑制物是影响胚萌发的重要因素。内源激素ABA和IAA在巴东木莲种子休眠与萌发过程中起着重要作用, ABA是引起休眠的关键因素, IAA有助于种子的萌发, IAA/ABA相对含量的变化对种子的休眠和萌发产生重要影响。巴东木莲种子的休眠是由种子本身的形态和生理特点引起的综合休眠, 在4℃低温保湿条件下才能完成其形态和生理后熟过程, 而自然条件下, 巴东木莲种子成熟时正值秋季少雨, 很容易失水而不能完成其后熟过程而失去生活力, 这可能是导致该物种自然更新困难的重要原因。     

濒危植物桃儿七种子休眠特性的研究

桃儿七种子在自然条件下具有休眠期长、萌发不良的生理特性,为了探讨和研究桃儿七种子的休眠特性,利用分离胚培养、生物鉴定法、GA₃浸种、以及综合利用GA₃和低温层积处理等方法。结果表明：种皮和胚乳的限制以及生理后熟是引起桃儿七种子休眠的主要原因,用400 mg·L^-1的GA₃溶液浸种24 h或低温层积后用GA₃处理均能在一定程度上解除休眠促进萌发,其中以低温层积90 d后用500 mg·L^-1的GA₃浸种36 h效果最好,发芽率和发芽势分别达到81.11%和50.00%。     

东北刺人参种子萌发影响因子的研究

东北刺人参(Oplopanax elatus Nakai)种子透水性良好,休眠后萌发不受其影响。种皮和胚乳的水提取物中存在萌发抑制物质,胚乳中提取物对白菜种子萌发的抑制效果比种皮更明显。种子自然脱落时胚尚未分化完全,处于心形胚阶段。种子需要先温暖层积以完成胚的分化与生长,然后转入低温层积完成生理后熟。同批种子胚的发育不完全同步,变温层积处理7个月有极少数种子萌发,连续变温层积处理17个月大部分种子萌发。不同年份受气候条件影响,种子产量和发芽率差异较大。种子耐贮性较强,贮藏2年的种子生活力变化不大,仍具有较高的萌发潜力。     

东北刺人参种子萌发影响因子的研究

东北刺人参(Oplopanax elatus Nakai)种子透水性良好,休眠后萌发不受其影响.种皮和胚乳的水提取物中存在萌发抑制物质,胚乳中提取物对白菜种子萌发的抑制效果比种皮更明显.种子自然脱落时胚尚未分化完全,处于心形胚阶段.种子需要先温暖层积以完成胚的分化与生长,然后转入低温层积完成生理后熟.同批种子胚的发育不完全同步,变温层积处理7个月有极少数种子萌发,连续变温层积处理17个月大部分种子萌发.不同年份受气候条件影响,种子产量和发芽率差异较大.种子耐贮性较强,贮藏2年的种子生活力变化不大,仍具有较高的萌发潜力.     

濒危植物中甸刺玫种子休眠及其生态学意义

对中甸刺玫Rosa praelucens种子结构及其透水性,赤霉素处理对胚的影响,果壳、种皮、胚乳的粗提物活性进行研究。结果表明：(1) 中甸刺玫外种皮是由多层排列紧密的厚壁细胞组成,内种皮为坚硬致密的栅栏组织;(2) 种皮对种子的吸胀阻碍较大, 未处理的种子吸水率较低,吸水13 d后增加量为18.82%;(3) 果实结籽率为0.69%,多数果实中没有饱满的种子;(4) 赤霉素100 mg·kg-1预处理种子可加快胚的萌发速率;(5) 胚乳、种皮、果壳中存在内源抑制物。中甸刺玫种子的休眠是由其形态和生理特点引起的综合休眠。     

滇重楼种子水浸液对三种植物种子萌发和幼苗生长的影响

利用滇重楼(Paris polyphylla Smith var.yunnanensis(Franch.)Hand.-Mazz.)种子外种皮和胚乳的水浸液对白菜(Brassica pekinensis(Lour.)Rupr.)、绿豆(Vigna radiata(Linn.)Wilczak)、小麦(Triticum aestivum L.)种子进行处理,研究滇重楼种子水浸液对3种植物种子萌发、幼苗生长和保护酶活性的影响,并利用GC-MS方法对滇重楼种子内源抑制物的成分进行分析。结果显示,不同浓度滇重楼外种皮、胚乳水浸液对上述3种受体植物的发芽率、苗高、根长及鲜重均产生影响,其作用强度和水浸液的浓度有关,总体上表现出低促高抑的双重浓度效应。滇重楼种子水浸液对白菜的影响作用最强,对绿豆的影响作用最弱,且胚乳水浸液的影响较外种皮强。不同浓度滇重楼种子外种皮和胚乳水浸液均能影响3种植物幼苗体内保护酶的活性,随着水浸液浓度的升高,叶片中超氧化物歧化酶(SOD)、过氧化物酶(POD)活性总体增加,与对照相比差异显著。白菜、小麦过氧化氢酶(CAT)活性减少,与对照相比差异显著;绿豆过氧化氢酶(CAT)活性增加,但与对照相比无显著差异。利用GC-MS方法从胚乳和外种皮水浸液中分别检出8种和2种物质。研究结果表明滇重楼种子中存在内源抑制物质,可能是导致种子休眠的原因;种子水浸液可能通过影响植物幼苗保护酶的活性进而影响其正常生长;有机酸类物质可能是滇重楼种子内源抑制物之一。     

羊草种子休眠机制及破除方法研究

羊草种子休眠程度深、发芽率低是限制栽培利用的重要因子.采用不同破除羊草种子休眠的方法,测定各处理对种子萌发的影响,以探索破除羊草种子休眠的有效途径.结果显示:(1)刺破种皮的裸种子较完整种子的萌发率、吸水速率、生活力分别由对照的6%、63%、0%显著增加到60%、86%、94%.(2)完整羊草种子分别用清水浸种1 d、30% NaOH浸种80 min、清水浸种1 d后用30% NaOH浸种60min其萌发率由6%分别显著提高到36%、60%、84%,而各浓度赤霉素处理完整种子其萌发率较对照均无显著变化. (3)采用清水浸种1 d后用30% NaOH处理60 min,再施加200 μg/g GA3综合处理,可使羊草完整种子的发芽率由6%提高到91%,接近其种子生活力94%.研究表明,羊草种子的稃与种皮不影响种子水分的吸收,但影响种子对GA3的吸收、不同程度地阻碍大分子物质的渗入、限制羊草种子内部萌发抑制物的渗出,从而引起种子休眠;分析认为稃和种皮以及种子内部萌发抑制物质是引起羊草种子休眠的主要原因.     

血皮槭种子休眠机制研究

利用抑制物生物测定法和酸蚀技术研究了血皮槭种子休眠的原因。血皮槭种子吸水是一个非常缓慢的过程,在140 h以后种子含水量才能达到68%左右。酸蚀处理种子3 h,虽然没有加快种子的吸水速率,但能较好得使果皮变薄,也不影响种子的生活力。种子的各部位（果皮、种皮、子叶、胚根）均含有抑制物质,对小白菜种子的发芽率及胚根生长有很强的抑制作用,子叶各种处理水浸提液的抑制作用最强,果皮和种皮次之。血皮槭种子休眠主要由种壳机械障碍和种胚生理休眠两重因素导致,因此如何克服致密果壳而使激素能接触生理休眠的种胚是打破其种子休眠的关键技术。     

Antisense-transformation reveals novel roles for class I beta-1,3-glucanase in tobacco seed after-ripening and photodormancy

Little is known about the molecular basis for seed dormancy, after-ripening, and radicle emergence through the covering layers during germination. In tobacco, endosperm rupture occurs after testa rupture and is the limiting step in seed germination. Class I beta-1,3-glucanase (betaGLU I), which is induced in the micropylar endosperm just prior to its penetration by the radicle, is believed to help weaken the endosperm wall. Evidence is presented here for a second site of betaGLU I action during after-ripening. Tobacco plants were transformed with antisense betaGLU I constructs with promoters thought to direct endosperm-specific expression. Unexpectedly, these transformants were unaffected in endosperm rupture and did not exhibit reduced betaGLU I expression during germination. Nevertheless, antisense betaGLU I transformation delayed the onset of testa rupture in light-imbibed, after-ripened seeds and inhibited the after-ripening-mediated release of photodormancy. It is proposed that betaGLU I expression in the dry seed contributes to the after-ripening-mediated release of seed dormancy.     

Parental effects on seed mass: seed coat but not embryo/endosperm effects

Many biologists studying environmentally induced parental effects have indirectly suggested that the parental environment alters seed mass by altering the amount of endosperm or embryo tissue in the seed. We tested this hypothesis by measuring the effects of parental temperature on total seed mass, seed coat mass, and embryo/endosperm mass in offspring of Plantago lanceolata. Parental temperature significantly affected total seed and coat mass but not endosperm/embryo mass. Thus, larger seeds do not contain more resources in the embryo or endosperm than do small seeds. Rather they have more coat mass, which probably strongly influences germination. These results suggest caution when making assumptions about the pathways by which environmentally induced parental effects are transmitted in plant species. We also observed that controlled crosses differed significantly in their response to parental temperature, which provides evidence for genetic variation in environmentally induced parental effects, i.e., intergenerational phenotypic plasticity, in natural populations of P. lanceolata.     

桃儿七种子解剖结构及其萌发生长期形态特征

为探明种皮和胚乳是否是限制桃儿七种子萌发的主要因素,利用组织切片和显微技术,对桃儿七种子及其不同萌发期（1、7、14、21、28 d）解剖结构和播种后一定时期内（7~210 d）的植株生长形态进行观察。桃儿七种子由种皮、胚乳和胚构成。种皮包括外种皮和内种皮,外种皮致密规整,由外至内分别为栅状石细胞和表皮层细胞,内种皮由5~6层海绵细胞组成。胚乳占种子体积的绝大部分,包括珠孔胚乳和外胚乳。胚由胚根、胚轴和子叶组成,被致密种皮、多层珠孔胚乳和外胚乳包围。萌发期1~7 d胚根和胚轴开始伸长,7~14 d两片子叶分离,14~21 d胚根突破珠孔胚乳和种皮,21~28 d胚根、胚轴和子叶继续扩张伸长。种子播种210 d后可平均形成3片功能真叶和5条不定根。致密种皮（物理休眠）和多层胚乳（机械休眠）是限制桃儿七种子萌发的两个主要因素。     

Structure and Histochemistry of Embryo Envelope Tissues in the Mature Dry Seed and Early Germination of Phacelia tanacetifolia

The embryo envelope tissues in both mature dry seed and duringearly germination of Phacelia tanacetifolia were investigatedby bright-field and fluorescence light microscopy and scanningelectron microscopy. The ruminate seed had an irregularly reticulatesurface owing to the presence of polygonal areas, correspondingto the cells of the seed coat. The raised margins of these cellsjoined at the lobe tips, where radially arranged thickeningsoccurred. The unitegmic seed coat was made up of three distinctlayers: the frayed outer layer, the middle layer with portionsrising outwards to form the radial thickenings, and the innerlayer, the thickness of which was greatest in the micropylarzone. The endosperm tissue had two regions, the micropylar andthe lateral endosperm, which differed in polysaccharide composition,thickness and metachromasy intensity, and presence (in the lateralendosperm) or absence (in the micropylar endosperm) of birefringenceof the cell walls. Moreover, in the micropylar region, wherethe embryo suspensor remnant was found, Ca-oxalate crystalswere scarce or absent. The presence of a partially permeablecuticle covering the seed endosperm was observed. Incubationof seeds in Lucifer Yellow CH indicated that water was ableto penetrate quickly into the seed coat along the pathway formedby the radial thickenings, the raised margins of the polygonalcells and the middle layer. Afterwards, LY-CH readily infiltratedthe apical portions of the seed lobes and then the whole endosperm.Following imbibition, morphological changes were found in themicropylar endosperm, such as the initial digestion of proteinbodies. In addition, both in the seed coat and in the endosperm,a weaker fluorescence, probably due to leaching of polyphenolicsubstances, was observed. Once the seed coat was broken at themicropylar end of the seed, the endosperm cap surrounding theradicle tip had to be punctured by it so that complete germinationcould occur. Weakening and rupture of the micropylar endospermare briefly discussed. Copyright 2000 Annals of Botany Company Phacelia tanacetifolia, seed coat, micropylar endosperm, endosperm cap, early germination, structure, histochemistry