酶解压片分离沙田柚胚囊与胚胎发育的研究

用２．５％纤维素酶与２．５％果胶酶混合液在３０℃下对已固定的沙田柚胚珠酶解６－１０小时,分离了开花前,授粉至受精间隔期,合子休眠期,胚和胚乳发育各期的胚囊。用Ｏｌｙｍｐａｓ相差显微装置进行观察与摄影,在胚囊中显示了沙田柚胚胎发育各主要阶段的结构特征。分析了酶解压片技术在柑桔属植物胚胎发育研究的前景。     

小麦与赖草远缘杂交的受精和胚胎发育

对小麦（Ｔｒｉｔｉｃｕｍ ａｅｓｔｉｖｕｍ Ｌ．）和赖草（Ｌｅｙｍ ｕｓｓｅｃａｌｉｎｕｓＴｚｒｅｌ．）杂交的受精和胚胎发育进行了观察．赖草花粉在小麦柱头上萌发良好,花粉管可顺利长入花柱和胚囊,在检查过的３１９个小麦子房中,６２个（１９．４４％ ）发生了双受精,产生了胚和胚乳,但胚乳的发育往往落后于胚的发育;４９个（１５．３６％ ）发生了单卵受精,只产生胚而无胚乳;７个（２．１９％ ）发生了单极核受精,只产生胚乳而无胚．小麦×赖草虽然总受精率可高达３６．９９％ ,然而由于胚乳的缺乏或发育不完全,致使最后结实率很低．从１５０朵授过赖草花粉的小麦颖花中,只得到１粒种子．表明利用胚培养技术对杂种胚进行早期离体培养,可望提高杂种植株的获得率     

硬粒小麦与珍珠栗远缘杂交的受精作用和胚胎发育

对硬粒小麦（ＴｒｉｔｉｃｕｎｄｕｒｕｍＤｅｓｆ．）和珍珠栗（Ｐｅｎｎｉｓｅｔｕｍｇｌａｕｃｕｍｓｙｎ．Ｐ．ａｍｅｒｉｃａｎｕｍ）远缘杂交的受精作用和胚胎发育进行了研究。对授粉后的１９２个硬粒小麦子房进行制片观察,７．８１％发生双受精,具胚和胚乳,但胚乳发育往往落后于胚的发育;３．１３％只发生了单卵受精,只产生胚而无胚乳;１．０４％发生了单极核受精,只产生胚乳而无胚。总受精率为１１．９８％,成胚率为１０．９４％。由于胚乳的缺乏或发育异常及败育,最终难以获得有生活力的种子     

小麦与珍珠栗远缘杂交的受精作用和胚胎发育

对波斯小麦、“中国春”小麦与珍珠栗远缘杂交的受精作用和胚胎发育进行了研究。珍珠栗花粉管能在小麦柱头上萌发,并且有多个花粉管进入花柱及胚囊。波斯小麦已授粉的２０７个子房中,１１．１１％既形成胚又形成胚乳,７．２５％中形成胚,而１．９３％只形成胚乳,在这个杂交中受精率和成胚率分别为２０．２９％和１８．３６％。“中国春”小麦已授粉的１６７个子房中,相应数字是２．９９％、５．９９％、０、８．９８％和８．９     

通过和玉米杂交诱导硬粒小麦单倍体

硬粒小麦（Ｔｒｉｔｉｃｕｍ ｄｕｒｕｍ Ｄｅｓｆ．）ＤＲ１４７授以超甜玉米（Ｚｅａ ｍ ａｙｓ Ｌ．） ｓｓ ７７００的花粉后,在８３．４％ 的柱头上观察到花粉萌发及花粉管长入胚囊,有９．９％ 的子房发生了卵细胞的单受精,１．９％ 的子房发生了中央细胞的单受精,３２．７％ 的子房发生了双受精。尽管双受精后可同时形成胚和胚乳,但胚乳往往发育迟缓,甚至败育。硬粒小麦×玉米形成的杂合子核型高度不稳定,在最初的几次细胞分裂中,来自父本玉米的染色体逐步被排除,最后形成硬粒小麦单倍体胚。在授以玉米花粉４ ｈ 后用１００ ｐｐｍ ２,４－Ｄ溶液浸蘸硬粒小麦穗部,可以有效地促进幼胚在缺乏胚乳或胚乳败育情况下的生长和发育。授粉９—１３ ｄ 后由５３３个硬粒小麦子房解剖出２５个胚,得胚率为４．７％ 。通过幼胚拯救获得１１棵正常植株,植株获得率为２．１％ 。根尖细胞染色体计数表明,它们为单倍体（２ｎ＝ ２ｘ＝ １４）。     

小麦×长穗偃麦草的受精和早期胚胎发育

用石蜡切片法,对小麦（Ｔｒｉｔｉｃｕｍａｅｓｔｉｖｕｍ）和长穗偃麦草（Ｅｌｙｔｒｉｇｉａｅｌｏｎｇａｔａ）杂交的受精和早期胚胎发育进行了观察。结果表明,长穗偃麦草花粉在小麦柱头上萌发良好,花粉管可顺利长入花柱和胚囊。观察的１７０个小麦子房中,１７６５％发生了双受精,产生了胚和胚乳;９４１％发生了单卵受精,只产生胚而无胚乳;４７１％发生了单极核受精,只产生胚乳而无胚;总受精率为３１７７％;成胚率为２７０６％。由于胚乳的缺乏或发育异常及败育,最终难以获得有生活力的种子。为小麦与长穗偃麦草远缘杂交提供了细胞胚胎学证据。     

小麦与珍珠粟远缘杂交的受精作用和胚胎发育

对波斯小麦、“中国春”小麦与珍珠粟远缘杂交的受精作用和胚胎发育进行了研究。珍珠粟花粉管能在小麦柱头上萌发,并且有多个花粉管进入花往及胚囊。波斯小麦已授粉的207个子房中,11．11％既形成胚又形成胚乳,7．25％只形成胚,而1．93％只形成胚乳,在这个杂交中受精率和成胚率分别为20．29％和18．36％。“中国春”小麦已授粉的167个子房中,相应的数字是299％、5．99％、0、8．98％和8．98％。杂交后形成的胚和胚乳核型极不稳定,来自珍珠粟的染色体很快被排除,最后产生的是单倍体的小麦胚。但因无胚乳或胚乳败育,幼胚缺乏营养供应而停止发育或夭亡。探讨了影响小麦×珍珠粟受精率的可能因素以及通过远缘杂交染色体排除法进行单倍体诱导和珍珠粟基因向小麦转移的可能性。     

双苗春小麦胚和胚乳发育异常

用石蜡切片法观察了双苗春小麦胚和胚乳的发育;发现有许多异常现象。主要表现如下：１．双胚,发生频率约６％;２．未受精形成孤雌胚;３．胚乳中具无核细胞质泡;４．原胚时期胚囊不同程度变形、缩小。     

罗汉果胚、胚乳及胚乳吸器的发育

本文采用石蜡切片与酶解分离法对罗汉果Ｓｉｒａｉｔｉａｇｒｏｓｖｅｎｏｒｉ胚、胚乳及胚乳吸器的发育过程进行观察．ａ）罗汉果胚的发育是按Ｇｅｕｍｕｒｂａｎｕｍ的分裂程序进行的．属紫菀型．但在合子分裂成球胚过程中,胚芽原细胞分化明显．故属紫菀型的变异型。ｂ）胚乳发育属核型．在球形胚阶段,在合点端和珠孔端有发育的胚乳吸器形成并进行旺盛生长,最大长度达１４２０μｍ,心形胚期．吸器活动开始减退,合点端核型胚乳吸器转变成细胞型．由胚乳本体基部膨大细胞．充当补助吸器．ｃ）酶解分离法研究胚乳吸器的发生发育有较好的应用前景。     

多胚水稻品系SB—1的细胞胚胎学研究：助细胞无配子生殖

对多胚水稻（Ｏｒｙｚａ ｓａｔｉｖａ Ｌ．）品系ＳＢ－１ 自然群体中单倍体来源进行的细胞胚胎学研究表明,卵器中的一个或两个助细胞能在受精之前发育成胚,其发生率分别为观察子房数的２．２４％ 和１．７５％ 。在１ 个助细胞提前发育成胚的胚囊中观察到双受精作用。在开花后３—８ ｄ的颖果中观察到１．６２％ 的与合子胚迥异的异位瘦长单胚和０．８１％ 的有胚无胚乳子房,根据胚所处的位置认为其来源于助细胞无配子生殖。此外,还观察到极少数的中央细胞未经受精自发产生胚乳的现象。讨论了ＳＢ－１中发生的无配子生殖的意义     

Secretion of embryonic envelopes and embryonic molting cycles in Hemioniscus balani Buchholz,Isopoda Epicaridea

The fertilized egg of Hemioniscus balani, a viviparous isopod, is encased in two envelopes, I and II, the structure of which is described. In the course of its development, the embryo secretes five successive sacs called embryonic envelopes. Both their structure and the means of secretion by the embryo are analyzed through thin sections. The presence of these successive secretion cycles together with exuviations involving these embryonic envelopes lead us to believe that during embryonic development in Hemioniscus balani, embryonic molting cycles exist. The appearance and shedding of the envelopes of the fertilized egg and embryo allow determination of ten embryonic stages which are briefly described.     

Embryo Sacs of Hevea brasiliensis and Carica papaya Isolated with Enzyme-Squash Technique

The enzyme-squash technique had been employed to study the development of megaspores and embryo sacs from tropical plants of Hevea brasiliensis Muel-Arg. and Carica papaya L. Ovules fixed with FAA or FPA were enzymatieally macerated in 3% pectinase cellulase solution or in 3–4% snailase solution for 4–6 h, at 28–30℃ to isolate the embryo sacs after being squashed. The whole structural images of megaspores and embryo sacs at different developmental stages were observed and identified without staining under Olympus BH-2 phase contrast microscope or light microscope after ron-aceto-carmine staining.     

The follicular placenta of the viviparous fish,Heterandria formosa. I. Ultrastructure and development of the embryonic absorptive surface

Embryos of the poeciliid Heterandria formosa develop to term in the ovarian follicle in which they establish a placental association with the follicle wall (follicular placenta) and undergo a 3,900% increase in embryonic dry weight. This study does not confirm the belief that the embryonic component of the follicular placenta is formed only by the surfaces of the pericardial and yolk sacs; early in development the entire embryonic surface functions in absorption. The pericardial sac expands to form a hood-like structure that covers the head of the embryo and together with the yolk sac is extensively vascularized by a portal plexus derived from the vitelline circulation. The hood-like pericardial sac is considered to be a pericardial amnion-serosa. Scanning and transmission electron microscopy reveal that during the early and middle phases of development (Tavolga's stages 10–18 for Xiphophorus maculatus) the entire embryo is covered by a bilaminar epithelium whose apical surface is characterized by numerous, elongate microvilli and coated pits and vesicles. Electron-lucent vesicles in the apical cytoplasm appear to be endosomes while a heterogeneous group of dense-staining vesicles display many features characteristic of lysosomes. As in the larvae of other teleosts, cells resembling chloride cells are also present in the surface epithelium. Endothelial cells of the portal plexus lie directly beneath the surface epithelium of the pericardial and yolk sacs and possess numerous transcytotic vesicles. The microvillous surface epithelium becomes restricted to the pericardial and yolk sacs late in development when elsewhere on the embryo the non-absorptive epidermis differentiates. We postulate that before the definitive epidermis differentiates, the entire embryonic surface constitutes the embryonic component of the follicular placenta. The absorptive surface epithelium appears to be the principle embryonic adaptation for maternal-embryonic nutrient uptake in H. formosa, suggesting that a change in the normal differentiation of the surface epithelium was of primary importance to the acquisition of matrotrophy in this species. In other species of viviparous poeciliid fishes in which there is little or no transfer of maternal nutrients, the embryonic surface epithelium is of the non-absorptive type.     

水稻亚种间杂种小穗败育的细胞学基础

本文对普通栽培稻不同品种类型间杂种小穗败育的细胞学基础及雌性败育的过程进行了研究,结果表明:(1)引起杂种小穗败育的原因有胚囊败育、花粉败育、开花时花药不开裂和雌雄异熟。其中胚囊败育而丧失受精能力是引起低结实率的最重要的因素,开花时花药不开裂和雌雄异熟在一定程度上形成了雌雄性细胞时间和空间的隔离屏障。(2)杂种植株的所有大孢子母细胞都能进行正常的减数分裂,形成四个大孢子,败育主要发生在靠近合点端的功能大孢子分化形成胚囊的早期,有的功能大孢子在进行第一次有丝分裂前便萎缩解体,多数走向败育的功能大孢子能完成一次或二次有丝分裂,形成二核或四核败育胚囊。败育的共同特征是无液泡的分化,细胞质少或退化,在败育胚囊残迹部位,解体的珠心细胞和萎缩的胚囊残渍混杂垛叠。已受精的杂种子房没有观察到胚及胚乳发育的异常。籼粳杂种胚囊败育频率较高。     

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     

Isolation of Fertilized Embryo Sacs and Zygotes and Triggering of Zygote Division in Vitro in Nicotiana tabacum

Three methods were established to isolate fertilized embryo sacs in Nicotiana tabacum, i. e. enzymatic maceration combined either with shaking, microdissection or grinding respectively. Living fertilized embryo sacs of various developmental stages after fertilization could be isolated successfully by these methods. Each method had its own adoptation to the materials of different developmental stages. Among them the method of enzymatic maceration combined with grinding was the best:Ovules were first treated in enzymatic mixture (1% cellulase R-10, 0.5% macerozyme R-10, 12% mannitol, pH 5.7) for about 30 min. Then droplets of the ovule suspension were gentlely grinded by a flat-headed glass rod. After grinding several droplets of mannitol solution (8%～ 10%) were added for releasing and washing embryo sacs. Compared with the other two methods this method was more convenent and had higher isolation efficiency. Isolation of fertilized embryo sacs offered a good means for microscopic observation on the postfertilization development including synergid degeneration, endosperm formation and zygotic changes without interference by the surrounding sporophytic tissue. Living zygotes and endosperm cells could be further isolated by a second enzymatic maceration procedure followed by brief micromanipulation. Several characters had been found to distinguish the protoplas'ts of free zygotes from those of other cell sources. Isolated zygotes were cultured in microchambers (Millicell-CM) feeded with macrocultured mesophyll protoplasts. The first division of zygotes was induced, resulting in proembryos consisting of two cells.     

西瓜不同发育时期的助细胞超微结构的变化

被子植物胚囊的“雌性生殖单位”,已在多种植物上进行了超微结构的观察,但大多都以卵细胞受精前后的结构变化为主要研究内容。对于“雌性生殖单位”中的另一重要成员——助细胞,在不同发育状态下其结构变化的详细资料不多,尤其是助细胞退化后的物质去向,少见报道。本研究主要观察了西瓜不同发育时期(受精前后)、不同发育状态(柱头授粉和未授粉)的助细胞超微结构,以期为研究助细胞在双受精中所起作用提供新的资     

An embryological study ofPlatanthera bifolia (Orchidaceae)

Flowers ofPlatanthera bifolia were hand-pollinated and fixed in FPA₅₀ after 2, 5, 7, 14, and 21 days. Ovules, made transparent in Herr's clearing fluid, were investigated using confocal scanning laser microscopy. Pollination initiates the megasporogenesis. Two days after pollination dyads are frequent. Three days later most embryo sacs contain two nuclei. Seven days after pollination the embryo sacs are 4–8-nucleate and some are organized, and a week later all embryo sacs are organized and fertilization takes place. The embryo sac development follows thePolygonum type. Twenty-one days after pollination the egg nuclei have been fertilized and the embryo sacs contain 2- to many-celled embryos. A suspensor is formed during early stages of embryo development but degenerates later. Fertilization of the central nucleus does not lead to endosperm development.     

Deleterious effect of minimal enzymatic treatments on the development of isolated maize embryo sacs in culture

The long-term viability of isolated embryo sacs was studied in maize. Fertilised embryo sacs were digested in order to remove most of the nucellus cells present on their surfaces and then transferred to culture. Experiments on 161 embryo sacs showed that isolation treatments using even minimal enzymatic digestion affected the further development of the embryo sacs. Few embryo sacs survived in culture and those produced only abnormal embryos; they produced no plants. We concluded that embryo sacs isolated through enzymatic digestion may offer limited prospects for long-term studies where normal embryogenic development is required. Alternative strategies are discussed for maize.     

龙须草无融合生殖的胚胎学证据

采用石蜡切片技术对龙须草(Eulaliopsis binata(Rotz)C.E.Hubb)进行了系统的胚胎学研究,证明龙须草为禾本科植物中一种新的无融合生殖材料.龙须草无融合生殖方式为无孢子生殖,在胚珠发育早期,多个珠心细胞特化为无孢子生殖原始细胞,由原始细胞发育为单核胚囊,经两次有丝分裂形成4核胚囊,进一步分化形成两种类型的成熟胚囊:(1)具1个卵细胞,1个助细胞和2个极核,占观察总数的67.6%;(2)具1个卵细胞,2个助细胞和1个极核,占观察总数的32.4%.胚囊发育属大黍型.多个无孢子生殖原始细胞可以同时发育,最后形成2个或多个胚囊,其比例为17.7%.胚珠内没有有性胚囊的发育.胚的发生有两种类型:(1)早发生胚(74%),开花前1～2 d,极核未分裂前卵细胞分裂形成胚;(2)迟发生胚(26%),开花后2～3 d,极核分裂形成多个胚乳游离核后,卵细胞启动分裂形成胚.存在多胚现象,多胚来自不同胚囊内卵细胞的孤雌生殖,多胚发生率为13%.胚乳由极核不经受精自发分裂产生.