红豆杉的胚珠发育,传粉滴形成和传粉过程

观察了红豆杉（Ｔａｘｕｓ ｃｈｉｎｅｎｓｉｓ （Ｐｉｌｇ．）Ｒｅｈｄ）的花粉形态和水合特性及胚珠发育、传粉滴形成与传粉过程。成熟花粉为单细胞,无气吓,形状不规则,外壁表面具大量乌氏体。花粉水合时,内壁膨胀,外壁开裂。通常情况下,外壁保留在水滴或传粉滴的表面,而花粉的其他部分进入水滴或传粉滴内。在８月下旬,可观察到下弯的雌性生殖芽。下弯这一特性是雌性生殖芽区别于营养芽的重要特征。这一时期的雌性生殖芽     

侧柏雌球果及其胚珠的发育

观察了侧柏（Ｐｌａｔｙｃｌａｄｕｓ ｏｒｉｅｎｔａｌｉｓ（Ｌ．）Ｆｒａｎｃｅ）胚珠的发育过程及后期球果苞片的结构变化。在北京,雌球果原基７月分化。通常一个球果有４对苞片,中部两对可育,靠球果顶端一对各产生一枚胚珠,其下一对各两枚。胚珠的发育顺序是向顶的,下部可育苞片腑部的两枚胚珠源于同一原基。胚珠原基分化成珠心和珠被,在发育过程中,珠被逐渐包围珠心,最后形成２烧瓶状的胚珠。１１月至次年１月,球果处     

被子植物胚珠发育机理研究的新进展

本文主要概述了矮牵牛胚珠特异基因的克隆及功能研究,并通过与拟南芥胚珠发有突变体的比较,以探讨被子植物胚珠发育的基因调控机理。     

北京地区油松胚珠发育时期的确定

采用显微观察法对北京地区不同发育时期的油松胚珠进行解剖结构观察,以确定北京地区油松胚珠的发育时期。结果表明,北京地区油松胚珠的发育历时13个月(从2003年4月~2004年5月),具体时期为:2003年4月12日为胚珠分化期,4月21日左右为大孢子母细胞时期,5月至8月为游离核时期,2003年8月至2004年2月为胚珠休眠期,2004年4月15日左右进入雌配子体细胞化时期,4月21日左右为颈卵器原始细胞活动期,5月8日左右为中央细胞分裂期,5月14日左右为成熟颈卵器时期。本研究结果中油松胚珠经历的发育阶段与前人的研究基本一致,但在时间上存在差异,而且北京地区比辽宁兴城地区油松胚珠发育时期平均提前了大约20~30 d。     

银杏胚珠发育进程的解剖学研究

以15 a生银杏(Ginkgo bilobaL.)品种‘佛指’(G.bilobacv.‘Fozhi’)为材料,观察了授粉后胚珠结构、雌配子体发育和种皮分化形成的过程。结果表明:(1)授粉后2 d胚珠已分化出珠心、珠被和珠托组织,珠被顶端形成直径为162.16μm的珠孔与540.54μm长的珠孔道,珠心组织顶端形成长约520.83μm、最大直径约125.06μm的瓶状贮粉室,花粉粒经珠孔道已到达贮粉室并在其中停留;(2)雌配子体的发育先后经历了游离核阶段(授粉后5~30 d)和细胞化阶段(授粉后30~45 d),之后在近珠孔端形成颈卵器,其余部分发育为胚乳薄壁细胞,其营养物质的积累高峰期为授粉后60~80 d;(3)种皮分化与形成分别经历珠被分化期(授粉期至授粉后30 d)、种皮分化期(授粉后30~50 d)、种皮形成初期(授粉后50~80 d)、种皮形成期(授粉后80~90 d)。     

烟草花发育基因Nfbp6在花粉和胚珠形成过程中的特异表达

Nfbp6是从烟草中克隆的一种调节花发育的基因 ,与已知的C类基因有很高的同源性 .应用RNA原位杂交技术 ,对其在烟草花发育的各个阶段的表达进行了研究 .结果表明Nfbp6在花器官原基的早期分化、形成过程中有一定表达 .在后期花芽发育过程中 ,Nfbp6的转录加强 ,尤其在花粉和胚珠发育过程中表达强烈 .同时 ,Nfbp6在花柱引导组织和花药裂缝细胞、早期环式细胞簇中也有一定表达     

大叶杨的受精作用和胚胎发育

用细胞化学方法研究了大叶杨(Populus lasiocarpa Oliv.)的受精作用和胚胎发育。结果表明:柱头在授粉期有蛋白质和多糖性质的分泌物。花粉在授粉后6小时大量萌发。授粉后6天开始出现双受精作用。次生核受精完成较卵核受精完成为早,精卵融合为有丝分裂前型。受精作用消耗大量淀粉粒。核型胚乳于授粉后开始细胞化。胚乳主要成分为蛋白质,游离核形成后不出现淀粉粒。胚乳在胚的发育中被吸收。休眠期的合子经历液泡消失、合子皱缩、液泡再出现、合子伸长等极性化过程。胚胎发生类型为茄型。授粉后44天,胚相继发育成熟。成熟胚直立,具2枚相互包裹的子叶。根冠原中具类根冠柱结构。     

低温对蝴蝶兰胚珠发育的影响

低温(12-18℃)处理的蝴蝶兰,授粉50 d开始分化胚珠原基、60 d胚囊处于大孢子母细胞时期,比常温(20-25℃)下的推迟10-15 d;授粉70 d,常温下的蝴蝶兰植株已完成雌配子体发育和双受精,而低温处理的蝴蝶兰仍未完成大孢子的发生过程.低温处理的蝴蝶兰,胚囊发育过程中珠心细胞提前退化,在大孢子母细胞外围形成较厚的胚囊壁.胚囊只发育到单核胚囊阶段,没有形成成熟胚囊.     

High temperatures applied at fall forcing disturb ovule development in Syringa vulgaris L. “Mme Florent Stepman”

Under natural conditions, Syringa vulgaris blooms in May but it may be forced to produce blooming panicles in autumn, winter and early spring. To break winter dormancy, plants require high temperatures, the range of which depends on the forcing date. Forcing in November requires exposure to temperatures of ∼37°C. Such an exposure may affect the development of both male and female flower organs. In this work we have followed the anatomical changes in the ovule development in buds collected from plants forced in autumn, and compared them to those in plants blooming under natural conditions in May. From the earliest identifiable stages, in flowers forced in November the ovule development was delayed relative to the normal development pattern. Ultimately, most of the ovules (83%) degenerated before the differentiation of the embryo sacs was completed. We believe that it is the high temperatures required during autumn forcing that affect the development of female gametophytes, leading to the formation of defective structures which often degenerate. This in turn may reduce the esthetic appeal of the inflorescences and reduce their commercial value.     

Ovary signals for directional pollen tube growth

In angiosperms, the female gametophyte has a secluded life; it is protected by several concentric layers that envelop each other. The embryo sac is surrounded by the nucellus, which in turn is wrapped by the integuments forming the ovule, which is nested in the ovary. These wrappings are not hermetic, but contain little ”gates” the pollen tube must traverse on its way towards the embryo sac. Information is emerging that shows that the ovary and ovule provide signals orienting and directimng the pollen tube on the right course. There are three main bodies of evidence supporting this hypothesis. One relates to developmental changes in the female tissues and how they affect pollen tube growth. The second refers to defective ovule mutants, which induce defective pollen tube guidance. And the third relates to the possible molecules involved in this signalling. Here, information gathered along these three main lines of evidence is reviewed. All converge to the conclusion that different checkpoints exist all along the pollen tube pathway. These checkpoints provide active signalling that guides the pollen tube to its destination, the embryo sac. Received: 15 December 2000 / Accepted: 13 June 2001     

Embryo sac development is affected in Petunia inflata plants transformed with an antisense gene encoding the extracellular domain of receptor kinase PRK1

 In a previous study of the function of a pollen-expressed receptor kinase of Petunia inflata, PRK1, it was found that transgenic plants carrying an antisense-PRK1 gene were unable to transmit the transgene through either the male or, unexpectedly, the female. In this report, the nature of this female phenotype was studied using one of the transgenic plants, ASRK-13. Electron and light microscopic examination of the embryo sac and seed development of ASRK-13 and a wild-type plant revealed that embryo sac development of approximately half of the ovules of ASRK-13 was abnormal. The development of the affected embryo sacs was arrested at the late stages of megagametogenesis. The majority of the affected embryo sacs completed three rounds of mitosis normally, but failed to progress through the maturation stages when cell expansion, nuclear migration, and differentiation take place. The remaining small number of abnormal embryo sacs were arrested at either the four- or eight-nucleate stages. The ovules containing the defective embryo sacs apparently failed to be fertilized, resulting in degeneration of half of the seeds produced by ASRK-13. RNA gel blot analysis suggests that the PRK1 gene is expressed in the ovary, albeit at a much lower level than in the anther. The possibility that the antisense PRK1 gene is responsible for the abnormal embryo sac development is discussed. Received: 25 April 1997 / Revision accepted: 25 June 1997     

Long term plant regeneratin from callus cultures of haploid wheat

A one-step method to rescue immature embryos of eastern cottonwood (Populus deltoides Bartr.) is described. Plantlets developed from 83% of 25-day-old embryos grown in shaken culture on Murashige and Skoog (MS) liquid medium with 2.2 m indole-3-acetic acid (IAA) and from 86% of embryos not supplemented with IAA. In contrast, when the MS medium was solidified with 0.8% agar, plantlets developed from 25% of 25-day-old embryos cultured on medium supplemented with IAA and from 28% of embryos in medium not supplemented with IAA. Eighty eight percent of all plantlets survived a gradual acclimitization to peat plugs in a greenhouse. The one-step liquid-culture method is an effective means of rescuing immature embryos by ovule culture from excised artificially-pollinated female branches in our cottonwood breeding program.