几种兰花种子无菌萌发及胚胎发育过程的几种途径

以虎头兰(黄色素花)×大雪兰、大雪兰×虎头兰(黄色素花)、虎头兰(黄色素花)×黄蝉兰、黄蝉兰×虎头兰(黄色素花)、冬凤兰、竹叶兰、窄唇蜘蛛兰、半柱毛兰、三褶虾脊兰和多花脆兰为材料,进行了杂交和自交种子无菌培养研究,并对胚胎发育进行了显微观察,结果表明:兰花种胚的发育途径有两条,一是种胚突破种皮后再转绿;二是种胚转绿后再突破种皮,且两条途径是同时进行的。种胚突破种皮的方式有3种:一是种子发育过程中,种皮慢慢消失,变成裸露的胚;二是种胚向种子的一端移动,最终突破种皮;三是种胚从种子的一侧突破种皮,形成裸胚。幼苗的发育途径有两条:一是小球体经圆球茎发育成小苗;二是小球体伸长成根茎后发育成小苗。     

罗布麻种子形态结构的初步观察

阿白7号种子棕红色,线状圆柱形,种脐着生在基部一端,种脐到珠孔一端有1条显著与种子纵轴平行的沟。红4号红麻成熟种子呈黄棕色,枣核状,种脐在整个种子长度约1／2处。阿白7号种子一般长2.62mm,直径为0.42-0.71mm,千粒重400－500mg。阿红4号种子一般长2.74mm,直径0.38-0.58mm,千粒重350mg左右。罗布麻种皮由内,外两种皮构成。外种皮为1层细胞,除种脐外,形成一个连续组织包裹在整个种子表面,细胞排列紧密,胞壁木质化。内种皮由2层到多层薄壁细胞构成,红,白麻种皮构造基本相似,但白麻厚。种子的胚由子叶,胚茎生长点,胚轴和胚根组成,胚乳不甚明显,似与种皮紧密联结在一起的1层薄壁细胞。     

4种野生兰花种子特征及离体培养初报

对4种野生兰花--虾脊兰、羊耳蒜、石仙桃及密花石斛的果荚、种子、种胚性状进行初步研究,并对其种子进行离体培养。结果显示,4种野生兰种子为白色、淡绿或黄褐,呈纺锤体或椭球体。羊耳蒜、石仙桃及密花石斛种子具种孔,种胚浓密且清晰可见;种子萌发较快且萌发率高,其中以石仙桃及密花石斛种子萌发最快,仅需36d,萌发率高达100%。虾脊兰种子未见种孔,种胚不甚明显,种子萌发缓慢且萌发率低。4种兰科植物种子均以原球茎方式萌发,通过继代培养,获得了一批无菌苗。     

云南红豆杉新采收种子的形态与离体胚的萌发特性

通过云南红豆杉新采收种子形态观察、透水性测定、种子大小以及所带胚乳多少对离体胚萌发率的影响等试验,探讨云南红豆杉种子的休眠与萌发机理。结果表明,云南红豆杉种子呈倒卵形和三棱形;胚酒瓶形,白色;胚乳淡黄色,油质。种子千粒重为72.934g;种皮、种仁和种胚分别占种子鲜重的50.56%、40.45%和8.99%;胚与种子的体积比(E∶S)为0.074。胚的体积为0.156—1.012mm~3,种子为51.658—109.649mm~3,两者呈显著正相关(P0.05,r=0.810)。完整种子的吸水率明显低于破裂种皮、酸蚀40min和酸蚀20min的种子,但差异随着浸泡时间延长而缩小;种子含水量饱和时,完整种子、破皮种子与酸蚀种子的吸水率无显著差异(前者为23.7%,后两者约28.0%)。不同大小种子离体胚的萌发率差异显著(P0.05),特大、大、中、小和特小种子的离体胚的萌发率为80%、77.8%、67.5%、62.0%和44.0%。胚乳抑制离体胚的萌发,不带胚乳离体胚的萌发率为41.3%,显著高于带胚乳的萌发率(P0.05),带部分胚乳的胚为9.7%—13.3%,带全胚乳的胚为0。同时离体胚培养过程中所用种胚的新鲜程度也严重影响胚的萌发率。云南红豆杉种子休眠属于中度生理休眠类型,种子中的抑制物质含量随时间的动态变化和胚乳中抑制物质含量的多少对胚萌发率的影响是以后云南红豆杉休眠研究的重点。     

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。     

三种兜兰属植物种子发育过程及其与无菌萌发的关系

某些兰科植物的种子成熟前,在无菌萌发过程中有较高的萌发率,而成熟后萌发率急剧下降。本研究针对这一现象,对三种兜兰属植物种子的发育过程进行了解剖学观察,并对授粉后不同时期的种子进行无菌播种,80d后统计其萌发率,以探究种子发育过程中的解剖学特征与萌发率之间的关系。研究结果表明种胚刚发育到椭球形胚的时候,胚柄尚存,种皮细胞尚未皱缩,此时三种兜兰的萌发率都能达到较高水平,表明这是适合兜兰属植物萌发的最佳时期;此后,种皮开始皱缩,木质素类物质积累导致种皮透水性下降,推测这可能是导致其后期萌发率下降的主要因素之一。     

不同成熟度花生胚萌发时子叶中贮藏蛋白质的降解

花生(Arachis hypogaea L.)汕油71果针入土20d(20 DAP)的种子剥去种皮后,10％的胚可以萌发,至40 DAP发芽率达98％。不同发育时期的花生胚萌发 10d后子叶盐溶蛋白质和花生球蛋白降解表明,20和32 DAP胚萌发后,子叶中这些蛋白质只有部分降解。随着胚成熟度增加,子叶中降解这些蛋白质的能力不断提高。20～40 DAP胚萌发4d时,子叶的BAPAase和GHE活性较低。50～80DAP胚萌发 4d,子叶中上述两种酶均显示较高的活性。     

蝴蝶兰红花系品种杂交种子形态及胚培养研究

对21个蝴蝶兰自交或杂交组合的种子形态进行观察和无菌培养,结果表明,蝴蝶兰不同组合的种子形态有一定差异,平均种子长、宽及种胚长、宽分别为0.292±0.025 mm、0.073±0.003 mm及0.151±0.009 mm、0.069±0.003 mm。种子萌发率及萌发所需时间因组合而异,平均萌发率为72.4%,原球茎及第一片叶出现所需时间分别为22±3 d、78±6 d,杂交组合启动萌发早、萌发率高。种子启动萌发所需时间、萌发率与果实、种子大小相关不显著,而种子启动萌发所需时间与种胚长、宽呈极显著负线性相关,表明种胚越大,萌发越快。     

珍稀濒危植物蒜头果种子萌发特征与幼苗类型的研究

以去除果皮后阴干的珍稀濒危植物蒜头果种子为材料,在温室大棚沙池内进行层积处理,从层积处理开始至子叶出土的不同萌发阶段,考察蒜头果种子发育形态、贮藏物质积累、酶活性以及幼苗类型等变化特征,初步探讨其种子休眠形成原因。结果显示：(1)蒜头果种子从解除休眠开始至萌发形成幼苗的过程约需195 d,其中幼胚的形态发育后熟约需75 d,随后30 d内是种子集中萌发的时期,其发芽率达到最高(53.33%);依据种胚发育形态的标志特征将此过程划分为7个阶段(S1～S7阶段):S1阶段种子未萌发,S2阶段种胚“露白”,S3阶段胚根突破种皮长超过1 cm, S4阶段下胚轴与胚根连接处形成弯钩结构,S5阶段“S”型胚形成及胚根前端膨大,S6阶段种子不仅具有膨大的胚根且已有侧根的分化,S7阶段子叶脱落,胚芽出土,真叶出现。(2)蒜头果种子在湿沙层积过程中,种胚胚长和胚率从S1阶段的(5.49±1.57)mm和(19.48±5.72)%分别增加至S6阶段的(67.92±2.94)mm和(240.75±15.29)%,胚率平均增加了12.4倍,显示蒜头果种子的胚需要经历后熟过程才能萌发,属于胚后熟型种子。(3)从...     

鹤顶兰种子萌发及原球茎增殖培养研究

以鹤顶兰成熟蒴果的种子为实验材料,研究影响种子非共生萌发的因素和种胚发育途径,并采用正交设计研究了原球茎增殖的影响因素。结果表明:冷藏影响种子的活力且其萌发率随冷藏时间延长而降低;0.5%NaClO溶液浸泡种子可提高萌发率,缩短初始萌发时间;种胚发育途径为种胚转绿后从种子侧面突破种皮而形成原球茎,随后分化出具根芽结构的完整植株;6-BA对原球茎增殖作用显著,原球茎增殖的最适培养基为1/2MS+3.0mg/L6-BA+1.0mg/L KT+1.0mg/L NAA,增殖倍数为6.67。     

Effects of ethylene and some other environmental factors on different stages of germination in red root pigweed (Amaranthus retroflexus L.) seeds*

Abstract. Ethylene was found to promote two distinct processes during germination of redroot pigweed (Amarantus retroflexus L.) seeds: embryo expansion that splits the seed coat (incomplete germination), and radicle penetration through the more elastic endosperm (complete germination). The two events can be separated in time by subjecting seeds to low water potential or low CO₂ levels, which arrest germination of some seeds at the incomplete stage. Ethylene applications to incompletely germinated seeds promote complete germination, with a response threshold near 0.02 cm³ m^?3 and saturation near 0.5 cm³ m^?3. Higher ethylene concentrations (0.5 to 50 cm³ m^?3) given during the first day of seed imbibition also increase the percentage of seeds which initiate embryo expansion and split the seed coat. Light and elevated CO₂ also promote radicle penetration of the endosperm in seeds incubated under water stress. The results support the view that the germination pause at the incomplete stage is an adaptation to environmental stresses that can be overcome with exogenous ethylene or certain other stimuli.     

北五味子种子萌发中形态学观察及生理生化指标分析

利用体视显微镜和组织细胞分析系统软件对北五味子种子萌发过程中形态学进行动态观察,并对其部分生理生化指标进行分析。实验结果表明,层积处理（4℃,沙培）初期,种子胚部较小,富含油脂;处理后期,胚部变得细长,逐渐伸向种子尖端一侧。处理60d时,种子开始萌动;至150d时,种胚突破种皮限制,开始发芽。随着种胚的发育,种子的含水量和可溶性蛋白的含量增加,α-淀粉酶活性逐渐提高,而可溶性总糖的含量则呈现先降低而后增高的趋势。     

Lucerne Saponins as Inhibitors of Cotton Seed Germination: THEIR EFFECT ON DIFFUSION OF OXYGEN THROUGH THE SEED COATS

The site of inhibition of cotton-seed germination by lucernesaponins seems to be associated with tissues other than theembryo. The rate of water uptake during imbibition was similarfor intact seeds immersed in water and for those in 0.5 percent saponin solution. Seeds previously immersed in saponinsolution showed a lower rate of respiration, absorbing about60 per cent less oxygen than those pre-immersed in water. Yetthe respiration rate of excised embryos from both treatmentswas the same. The extent of the inhibition of germination wasnot affected when oxygen was either bubbled through the saponin-containingimmersion-solution or passed through the flasks in which theseeds were germinated after 24 h of pre-immersion. The rates of oxygen diffusion through the seed coats and membranesof seeds pre-immersed in water or in saponin solution were measured.They were distinctly lower for seed coats and membranes whichhad been exposed to the saponin treatment. It has been concludedthat the seed coat and/or the membrane of intact cotton seedspre-immersed in saponin solution serve as a barrier for oxygendiffusion to the embryo, resulting in inhibition of germination.     

Deep and intermediate complex morphophysiological dormancy in seeds of Ferula gummosa (Apiaceae)

We tested the hypothesis that seeds of the monocarpic perennial Ferula gummosa from the Mediterranean area and central Asia have deep complex morphophysiological dormancy. We determined the water permeability of seeds, embryo morphology, temperature requirements for embryo growth and seed germination and responses of seeds to warm and cold stratification and to different concentrations of GA₃. The embryo has differentiated organs, but it is small (underdeveloped) and must grow inside the seed, reaching a critical embryo length, seed length ratio of 0.65–0.7, before the seed can germinate. Seeds required 9 weeks of cold stratification at <10°C for embryo growth, dormancy break and germination to occur. Thus, seeds have morphophysiological dormancy (MPD). Furthermore, GA₃ improved the germination percentage and rate at 5°C and promoted 20 and 5% germination of seeds incubated at 15 and 20°C, respectively. Thus, about 20% of the seeds had intermediate complex MPD. For the other seeds in the seed lot, cold stratification (5°C) was the only requirement for dormancy break and germination and GA₃ could not substitute for cold stratification. Thus, about 80% of the seeds had deep complex MPD.     

Investigating seed dormancy in cotton (Gossypium hirsutum L.): understanding the physiological changes in embryo during after‐ripening and germination

• The dormancy of seeds of upland cotton can be broken during dry after‐ripening, but the mechanism of its dormancy release remains unclear.
• Freshly harvested cotton seeds were subjected to after‐ripening for 180 days. Cotton seeds from different days of after‐ripening (DAR) were sampled for dynamic physiological determination and germination tests. The intact seeds and isolated embryos were germinated to assess effects of the seed coat on embryo germination. Content of H₂O₂ and phytohormones and activities of antioxidant enzymes and glucose‐6‐phosphate dehydrogenase were measured during after‐ripening and germination.
• Germination of intact seeds increased from 7% upon harvest to 96% at 30 DAR, while embryo germination improved from an initial rate of 82% to 100% after 14 DAR. Based on T₅₀ (time when 50% of seeds germinate) and germination index, the intact seed and isolated embryo needed 30 and 21 DAR, respectively, to acquire relatively stable germination. The content of H₂O₂ increased during after‐ripening and continued to increase within the first few hours of imbibition, along with a decrease in abscisic acid (ABA) content. A noticeable increase was observed in gibberellic acid content during germination when ABA content decreased to a lower level. Coat removal treatment accelerated embryo absorption of water, which further improved the accumulation of H₂O₂ and changed peroxidase content during germination.
• For cotton seed, the alleviation of coat‐imposed dormancy required 30 days of after‐ripening, accompanied by rapid dormancy release (within 21 DAR) in naked embryos. H₂O₂ acted as a core link between the response to environmental changes and induction of other physiological changes for breaking seed dormancy.

     

Development of seed coat-imposed dormancy during seed maturation in Cynoglossum officinale

The relationship between seed phenolics and appearance of seed coat–imposed dormancy during seed development in Cynoglossum officinale L. was studied. Up to 24 days after anthesis, seeds failed to germinate upon imbibition in Petri dishes at 25°C. At 44 days after anthesis, seeds were fully germinable; removal of seed coats did not improve their germination or O₂ uptake. At 72 days after anthesis, mature seeds at the base of the cyme did not germinate unless their coats were removed. Removal of seed coat also stimulated O₂ uptake at this harvest date. The methanol-soluble phenolic content of the seeds increased during the early stages of seed development, in both the seed coat and the embryo. As seed development continued, the methanol-soluble phenolic content of the embryo stabilized, but that of the seed coat declined. This decline was associated with an increase in the thioglycolic acid–soluble phenolics, presumably lignins, in the seed coat. These results suggest that polymerization of methanol–soluble phenolics into lignins in the seed coat during later stages of seed development renders the seed coat of C. officinale impermeable to 03, and thus keeps the seed dormant.     

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。     

扇脉杓兰果实生长动态及胚胎发育过程观察

对授粉后不同发育阶段扇脉杓兰(Cypripedium japonicum Thunb.)果实的生长动态进行了观察和分析,并分别采用TrC法和常规石蜡切片法研究了种子生活力及其胚胎发育过程.观察结果湿示:扇脉杓兰果实形态成熟时间约为110 d,其中,授粉后0～20 d为第1次迅速生长期,授粉后20～30 d为第1次缓慢生长期,授粉后30～50 d为第2次迅速生长期,授粉后50～110 d为第2次缓慢生长期;果实纵径和横径的生长动态变化过程相似,但横径的生长动态曲线较纵径平缓,形态成熟时果实的纵径和横径分别为48.87和13.59 mm.成熟种子由内外2层种皮和球形胚构成,不具胚乳,内外种皮间具空气腔;败育种子只具有内种皮和外种皮而无种胚.胚胎发育类型为石竹型,种胚自受精形成合子到发育为成熟球形胚约需95 d.种胚发育时合子第1次不均衡横裂形成基细胞和顶细胞;基细胞发育为胚柄细胞,胚柄细胞高度液泡化,在胚胎发育的过程中不进行分裂并逐渐退化消失;顶细胞不参与胚柄形成,并且经过有丝分裂最终形成球形胚;内珠被在种子成熟时发育成为1层致密的紧贴胚体的内种皮.种胚纵径和横径的生长动态变化相似,成熟球形胚的纵径和横径分别为208.71和106.19 μm.扇脉杓兰种子生活力较高,有生活力的种子占56％.根据研究结果推测:自然状态下扇脉杓兰种子萌发率较低,可能与致密的种皮、种子中较小的胚体以及无胚乳导致的营养成分不足有关.     

Structures contributing to the completion of conifer seed germination

The variety of interpretations of the origin and role of the tissues surrounding the emerging radicle of conifer seeds prompted us to study changes during germination. The structures contributing to the opening of the seed coat and protrusion of the radicle in pine and spruce seeds were examined using light microscopy and field emission scanning electron microscopy. The opening of the seed coat was mainly mechanical and primarily affected by the enlargement of the imbibed endotesta cells lining the micropylar canal. The hypertrophied nucellar apex, swelling remnants and mucous substances in the micropyle further enhanced the testa splitting which was reinforced by the straightening of the folded nucellar cap. The expansion of the imbibed megagametophyte and the embryo were conducive to the seed coat opening only at a later stage. This was followed almost immediately by the appearance of the root cap showing an early geotropic response typical for taproots and assuring an immediate anchoring of the emerged embryo to the ground. The translucent tissue composed of elongating cell rows preceded and surrounded the protruding radicle and derived mainly from two origins: the micropylar end of the megagametophyte and the root cap. Observations about the origin of the sheath clarify the reasons for previous interpretations about the putative role of the massive embryo root cap in testa splitting and germination. The protective and adhesive function of the sheath is concluded to be essential to the conifer embryos, which present the epigeal type of germination. Received: 7 July 1999 / Accepted: 11 August 1999