高等植物中原生质细胞间运动研究的进展

20世纪初已在植物营养组织和生殖体中观察到细胞核或染色质在细胞间的穿透迁移。但多年来涉及这一研究的学大多倾向于将它看做是人为赝象而未予深究。50年代中期,自吴素萱在葱（Allium L.）,蒜（Allium sativum L.）等植物中重新发现了核穿壁运动现象以来,我国植物细胞与生理学家随之进行了系统与广泛的探讨,穿壁运动的研究及进展主要包括两个方面,一方面是营养组织中原生质的细胞间运动,由吴素萱、娄成后合作主持的有关研究项目着重与营养组织中有机物的运输,分配与再利用生理过程相联系。多年来积累的成果表明：1）核物质的穿壁运动是广泛存在于植物营养组织中的固有正常现象。是一定生理状态下有机物在细胞间运输与细胞内含物再分配的一种方式;2）通过对蒜穿鞘、小麦（Triticum aestivum L.）珠心、胚乳等组织的显微活体观察与亚显微结构分析,揭示与记录了原生质在细胞间运动的全过程与动态细节,发现参与穿壁过程的不限于核,核和胞质各级分可同时,亦可分别借自身的主动伸缩穿壁迁移;呈现穿壁运动的组织中,壁上部分胞间连丝结构剧烈变更,胞间通道明显扩大,可达100～300nm,核或胞质可经此开放通道迁移而不致有损通道外沿质膜的完整;3）原生质穿壁运动的动力来自细胞的能量代谢,与微丝活动密切有关,穿壁的原生质组分呈现活跃的ATP酶活性。近期的研究表明,小麦胚乳细胞中作活跃伸缩运动的胞质纤索是由F肌动蛋白集束组成,肌动蛋白纤丝可跨胞分布而存在于态胞间连丝中,从而使相邻细胞的胞质骨架得以实现胞间连续,另一方面是生殖体中染色质的穿壁运动研究,主要在郑国昌主持下开展,着重探讨花粉母细胞间染色质穿壁现象的普遍性及其与遗传、变异和进化的关系,对多种植物的系统观察证明,染色质穿壁出现在减数分裂前期I的凝线期,染色质通过胞质通道在一系列细胞间依次迁移;由电镜观察可见,参与穿壁运动的还包括胞质的多种成员;穿壁运动的动力被认为由原生质的收缩蛋白提供。郑国昌等的研究成果表明,染色质穿壁运动可导致染色体数目、结构的改变,由此产生的部分有活力的配子体经受精后有可能导致新一代个体出现多倍体或非整倍体,引进遗传性状的变异。     

百合花粉母细胞间细胞融合期间腺苷三磷酸酶活性的细胞化学定位及其与染色质胞间转移的关系

用标准的磷酸铅沉淀的细胞化学方法,对百合花粉母细胞间染色质穿壁运动期间及其前后三个时期中的腺苷三磷酸酶(ATP 酶)活性进行了超微结构的定位。结果表明:(1)在穿壁前,ATP 酶活性主要定位于质膜、胞间连丝及细胞间隙;在内质网、高尔基体、质体和某些局部的基质(groundplasm)中,也表现有 ATP 酶活性反应的产物;但在染色质和核仁中,一般都没有这种反应。(2)在穿壁时,染色质从一个细胞穿壁转移到另一个相邻细胞,同时看到染色质和核仁内出现密集的 ATP 酶活性反应产物;在内质网和高尔基体的腔内以及质体的片层上也产生明显的 ATP 酶活性反应;而在质膜、胞间连丝及细胞间隙内 ATP 酶活性明显降低,甚至看不到明显的活性反应。(3)在穿壁后,质膜及细胞间隙中又产生明显的 ATP 酶活性反应产物,但核内染色质上的 ATP 酶活性则显著降低,而核仁内则仍有较高的活性。同前二个时期一样,内质网、高尔基体和质体上的 ATP 酶仍表现明显的活性反应。最后讨论了三个不同发育时期 ATP 酶活性及其分布部位的改变与染色质胞间转移的关系。     

小麦颖黑中反足细胞衰退过程的结构变化及其对胚乳形态建成的作用

小麦颖果发育初期,胚囊合点端的反足器由外向内逐步衰退,反足细胞在原生质结构经历剧烈变化的过程中不断输出其内含物,哺育邻近游离核胚乳的增殖,生长,承担着转运与供应营养的双重职责。胚乳－反足细胞分界壁上缺乏胼胝质的淀积,有利于反足细胞内含物中的溶质向胚乳输出,但是,反足细胞原生质组分中的一部分,其结构解体的程度是有限的;以大分子结构物的形式经共质体途径而转移,是反足细胞以内含物哺育乳所采用的又一重要方式,胚乳－反足细胞分界壁局部位点上宽阔胞质通道的形成,是胞间关系上出现的一种特定的结构变动,核物质,内质网槽库片段,质体,线粒体等,经此而向发育中的胚乳迁移,推断,物质的这种运转方式,对于胚乳在形态建成初期的迅速增殖,生长有重要意义。     

小麦颖黑中反足细胞衰退过程的结构变化及其对胚乳形态建成的作用

小麦颖果发育初期,胚囊合点端的反足器由外向内逐步衰退,反足细胞在原生质结构经历剧烈变化的过程中不断输出其内含物,哺育邻近游离核胚乳的增殖,生长,承担着转运与供应营养的双重职责。胚乳－反足细胞分界壁上缺乏胼胝质的淀积,有利于反足细胞内含物中的溶质向胚乳输出,但是,反足细胞原生质组分中的一部分,其结构解体的程度是有限的;以大分子结构物的形式经共质体途径而转移,是反足细胞以内含物哺育乳所采用的又一重要方式,胚乳－反足细胞分界壁局部位点上宽阔胞质通道的形成,是胞间关系上出现的一种特定的结构变动,核物质,内质网槽库片段,质体,线粒体等,经此而向发育中的胚乳迁移,推断,物质的这种运转方式,对于胚乳在形态建成初期的迅速增殖,生长有重要意义。     

小麦胚乳细胞中肌动蛋白纤丝分布格局的荧光显微观察

以异硫氰四甲基罗丹明－鬼笔环肽为探针,结合电视显微镜术对呈现原生质胞间运动的小麦（Ｔｒｉｔｉｃｕｍ ａｅｓｔｉｖｕｍ Ｌ．）胚乳细胞胞质中肌动蛋白纤丝（ＡＦｓ）的存在与分布格局进行了观察与分析。结果表明,ＡＦｓ以多种形式在胚乳细胞内呈区域性分布：胞核为ＡＦｓ网络所包围,ＡＦｓ成束由核周向四处辐射直抵周质层,大量纤细ＡＦｓ在胞质皮层内呈无序的密集分布以及腹沟区细胞内ＡＦｓ梭状体的大量汇集。联系胞质组分在胞间运动中的动态与胞质纤索对ＣＢ处理的反应,讨论了ＡＦｓ的不同存在状态与胞质纤索的伸缩穿越和细胞基质的集流迁移这两种胞间运动方式的关系     

F肌动蛋白作为胞间连丝组分的结构与生理学证据

以蒜(Allium sativum L.)瓣鞘外表皮为材料,利用荧光特异探针与共焦镜检术,结合透射电镜与免疫金标记对表皮细胞间胞间联络的性质、结构进行了系统观察.结果表明,加厚壁上的通道是由狭长的管状胞质和初生纹孔场上成束的胞间连丝衔接组成,前者实为原生质体的一部分.单个胞间连丝的孔径为60～70 nm,属正常胞间连丝范围,它们乃相邻细胞间共质联系的所在.荧光探针TRITC-Phalloidin (TRITC-Ph)标记的结果显示,整个通道上呈现红色荧光的纤索在接近初生纹孔场处明显变窄,与超微结构观察中所见的结构特点相吻合,共焦镜下观察到的初生壁上的荧光亮斑乃初生纹孔场中成束胞间连丝被标记的反映,从而有效地证实了F肌动蛋白在常态胞间连丝上的存在.免疫金标记实验显示在管状胞质中和胞间连丝上有金颗粒分布,这一结果为证实荧光标记物具肌动蛋白性质提供了有说服力的补充.     

植物细胞的胞间连丝

柿属 (Diospyros L.)胚乳细胞横切制片 ,示胞间连丝。许多多边形的细胞是柿属种子内的胚乳细胞的切面观 ;黄色部分是增厚的细胞壁 ,白色部分是细胞腔 ,原生质体和原生质丝呈深棕色 ,这些原生质丝即胞间连丝贯穿在相邻细胞的初生壁里 ,使相邻细胞的原生质体相互连结 ,成为细胞之间物质交流与传递信息的通道。细胞壁是植物细胞所特有的结构。一般幼小细胞的初生壁较薄 ,随着细胞的生长能够延伸扩大或逐渐加厚 ,多数细胞的初生壁停留在薄壁状态 ,但也有这种以贮藏养料为主要功能的胚乳细胞 ,它将自身发育的营养物质半纤维素 (一种多糖 )用沉…     

洋葱花粉母细胞细胞内、细胞间微染骨架的超微结构观察

以洋葱（Allium cepa L.）花粉母细胞为材料,采用DGD包埋去包埋原位技术,对花粉母细胞不同发育时期的细胞内、细胞间微染骨架的超微结构进行了电镜观察。结果发现,花粉母细胞核内存在的粗细不等的微染骨架,与核仁和染色体紧密相连,随着发育的推移,其均一性发生改变。在核周有核纤层样的结构存在,与细胞核和胞质中的微染骨架紧密相连,到前期结束时解体。洋葱花粉母细胞内具有发达的胞质微染骨架,这种结构在减数分裂前期Ⅰ变化不明显。在胞间连接（胞间连丝和胞质通道）内,也有精细的微染骨架分布,并且与两端细胞中的骨架相连。在凝线期的花粉母细胞中观察到细胞融合现象,有胞质或核内微梁骨架与穿壁转移的胞质小球和核小球内骨架相连。此时细胞核偏向一边,但细胞的基余部位仍充满了胞质微染骨架,初步探讨了核微染骨架与核仁和染色体之间的关系,核纤层与细胞核之间的关系。以及细胞内、细胞间微染骨架与细胞融合之间的关系。     

花粉母细胞间染色质穿壁运动机理的探讨

花粉母细胞间染色质穿壁运动发生在减数分裂第一次分裂同源染色体的联会时期,从细胞遗传学的角度来说,它是一个非常重要的现象。为了进一步分析染色质穿壁转移现象问题的实质,我们曾从形态学的和细胞生理学的角度,在染色质穿壁时期的前后,进行了细胞和细胞核的状态和特点的研究。还进行了全氧和全氮无氧呼吸,以及应用呼吸抑制剂和改变外界条件等试验,来观察和分析呼吸作用和染色质穿壁运动之间的关系。根据我们以前和现在的一些试验的结果来看,对于染色质穿壁运动的机理,可提出如下的假说:即核液的川流运动对花粉母细胞间染色质穿壁运动起着直接的推动作用,而原生质中收缩蛋白的主动伸缩运动却是染色质穿壁运动主要动力。原生质川流运动和染色质穿壁运动所需要的能源是有氧呼吸所生成的能,通过 ATP 释放高能磷酸键(～P)的形式供给的。     

水稻淀粉胚乳细胞编程性死亡中细胞核变化特征

应用透射电子显微镜技术,观察了水稻(Oryza sativa L.)淀粉胚乳细胞编程性死亡过程中核的变化特征.伴随胚乳的发育进程,淀粉胚乳细胞核表现出衰退特征:核变形、染色质凝缩、核膜多处被降解破坏、核基质外泄等.DNA Ladder显示核内大片段DNA呈严重的弥散状拖尾现象,而核内和胞质中在140～180 bp处有明显的条带.在核衰退的同时,其胞质中的粗面内质网、淀粉质体和线粒体等细胞器具有正常的代谢功能,细胞仍在合成并积累营养物质,淀粉胚乳细胞一边衰退一边行使其功能,直至死亡.这些结果表明,水稻淀粉胚乳在核衰退的同时,细胞仍在积极合成与积累贮藏产物,表现为一种特殊形式的植物细胞编程性死亡现象.此外,对淀粉胚乳细胞特有的核质关系、植物细胞编程性死亡过程中细胞核的变化等问题进行了讨论.     

An ultrastructural study of cytomixis in tobacco pollen mother cells

Intercellular chromatin migration (cytomixis) in the pollen mother cells of two tobacco (Nicotiana tabacum L.) lines was analyzed by electron microscopy during the first meiotic prophase. The maximal manifestation of cytomixis was observed in the pachytene. As a rule, several cells connected with one another by cytomictic channels wherein the nuclei migrated were observable at this stage. In the majority of cases, nuclei passed from cell to cell concurrently through several closely located cytomictic channels. Chromatin migrated between cells within the nuclear envelope, and its disintegration was unobservable. The nucleus, after passing through cytomictic channels into another cell, can be divided into individual micronuclei or, in the case of a direct contact with another nucleus, can form a nuclear bridge. It has been demonstrated that the chromatin structure after intracellular migration visually matches the chromatin structure before it passed through the cytomictic channel. No signs of pyknosis were observable in the chromatin of the micronuclei formed after cytomixis, and the synaptonemal complex was distinctly seen. The dynamics of changes in the nucleoli during cytomixis was for the first time monitored on an ultrastructural level. Possible mechanisms determining cytomixis are discussed and the significance of this process in plant development is considered.     

Intercellular movement of protoplasm in vivo in developing endosperm of wheat caryopses

Summary Earlier work in our laboratory indicated that protoplasmic constituents can migrate from one cell to another in certain tissues of higher plants. Further investigations have been conducted using garlic bulbs and wheat nucellus for microscopic observation of intercellular protoplasmic movement in vivo. These gave preliminary indications of the dynamic characteristics of migrating nuclei and cytoplasm. The present paper gives recent results providing new evidence for intercellular protoplasmic movement that is neither hindered by the presence of cell wall nor the narrowness of channels of intercellular connection. By careful manipulation, intact endosperm sacs could be taken from developing caryopses (6–8 days after fertilization) without apparent injury to constituent cells. Shortly after the living specimen is mounted on the microscopic stage, asynchronous intercellular protoplasmic movement can be observed here and there. It can be seen that protoplasm extrudes in rapid but intermittent movements from one cell to the next by vigorous contraction. Although various cell constituents may move together, they can also be quite independent of each other. The moving units, though undergoing violent deformation, resume their normal shape and structure following intercellular migration. Evidently this kind of movement is a naturally occurring and active phenomenon closely related to the physiological state of the tissue. Electron microscopic studies reveal that a limited number of plasmodesmatal channels undergo modification and enlarge to 100–400 nm, through which the protoplasmic constituents pass.     

Cytochemical Localization of Adenosine Triphosphataes Activity During Cytomixis in Pollen Mother Cells of David Lily and Its Relation to the Intercellular Migrating Chromatin Substance

Standard lead precipitation procedures have been used to examine the localization of ATPase activity during cytomixis in pollen mother cells of Lilium davidii var. willmottiae (Wilson) Roffill. Before cytomixis, cells at this stage of development show ATPase activity on plasma membrane, in the endoplasmic reticulum, dictyosomes, plastids, plasmodesmata, and in part of the groundplasm; however, there is no ATPase activity on the chromatin and nucleolus. During cytomixis, the chromatin substance begin to transfer from one cell to an adjacent cell, reaction product indicating ATPase activity is observed associated with the chromatin and nucleolus. ATPase activity is also found with the cistenae of both endoplasmic reticulum and dictyosomes, and some plastids. There is no deposition of ATPase reaction product associated with the plasm membrane and intercellular spaces. After cytomixis, the chromatin is little or no deposition of enzyme reaction product. ATPase activity, however, is consistenlly found within the intercellular space and on the plasm membrane, and also occur in the endoplasmic reticulum, dictyosome and plastid. The presence or absence of ATPase activity in the cell structure of pollen mother cells before, during or after eytomixis is discussed in relation to the active uptake or export of water for short-distance transport. It is also suggested that the intensive ATPase activity in the nucleus during cytomixis of pollen mother cells is evidence for a transport system involved in the active movement of the intercellular migrating ebromatin substance.     

Iatercellular Migration of Protoplasm and Its Relation to the Development of Embryo Sac in Nucellus of Wheat

During the development of the ovule before pollination, deterioration of successive layers of nucellar tissue, beginning from the nnermost, constantly takes place and consistently forms a zone of disorganization surrounding the periphery of the enlarging embryo sac. Nucellar tissue deteriorates much more profusely near the antipodal end of the sac. "Nuclear extrusion" taken as an indication of intercellular movement of the protoplasm which has undergone partial disassembly, can be seen among the nucellar tissues and between the nucellus and the embryo sac. The intruding nuclear fragments, some of which assume the form of nucleolus, can be found in the antipodal cells. The results interpreted according to our previous hypothesis, are as follows. The nucellar cell by means of intercellular movement of its own protoplasm in the state of partial disassembly, furnishes the embryo sac with composite units of various polymers and organelles. Consequently, the antipodal cells proliferate and flourish The interrelationship between nucellus and embryo sac has been discussed from the viewpoint of supply and utilization of nourishment, which is necessary for the rapid development of the embryo sac.     

The Relation between the Patterns of Cytomixis and Variation of Chromosome Numbers in Pollen Mother Cells of Jimsonweed ( Datura stramonium L.)

The phenomenon of cytomixis is a general occurenee in the pollen mother cells (PMCs) of certain angiosperms. Recently, we found this phenomenon also occurred in jimsonweed. According to our observations and a test of chi-square, it has been shown that the discrepancies between the patterns of intercellular chromatin migration and the variation of chromosome numbers in the PMCs of jimsonweed, as well as rye, are not significant. It means that the patterns of intercellulr chromatin migration and the variation chromosome numbers are related to each other.     

Ultrastructural Aspects and Possible Origin of Cytoplasmic Channels Providing Intercellular Connection in Vegetative Tissues of Anthers1

Cytoplasmic channel represents a huge intercellular connection other than plasmodesma. They are proposed to play an essential role in controlling cell-to-cell trafficking of macromolecules. The present study ultrastructurally examined the occurrence, structure, and formation of this intercellular path in somatic tissues of wheat, tobacco, and onion anthers as well as their differences from those present in anther generative tissue. It was shown that cytoplasmic channels existed not only in the pollen mother cells, but also in both epidermis and vascular parenchyma of the anthers. In somatic tissues, they appeared as plasmallema-lined tubes 400–750 nm wide filled with nuclear or cytoplasmic material, the latter including cytoplasmic matrix, ribosomes, and filamentous structures. Their biogenesis seems to result from the thinning of the local portions of cell wall containing multiple plasmodesmata and the fusion of plasmodesmata in such regions induced by the wall-digesting enzymes released by nearby located vesicles. In contrast to the channels existing in the pollen mother cells of tobacco, the cytoplasmic channels in the epidermal or vascular parenchyma cells of wheat, onion, and tobacco anthers usually do not appear in groups, but are single. Perhaps this is the way for nuclear material to migrate from cell to cell via a single channel and then form a single chromatin spherical body in the adjoining cell. An individual cell could not accept the nuclear material from another cell while extruding its own to the third cell. Cell-to-cell migration of organelles through the cytoplasmic channels was not shown in the somatic tissues.     

Ultrastructural Observation on the Intra- and Intercellular Microtrabecular Network of the Pollen Mother Cells in Onion (Allium cepa)

Using DGD embedment-free electron microscopy, ultrastructural observation on the intra- and intercellular microtrabecular network (MN) of the pollen mother cells (PMC) of the whole meiotic prophase Ⅰ in onion ( Allium cepa L.) was performed. Complex nuclear MN was observed in the nucleus of PMCs, spreading throughout the nuclear region. The nucleolus and chromosomes were connected with the MN filament network. The uniformity of nuclear MN changed with the development of the PMCs. A lamina-like structure surrounded the nucleus and joined the MN in nucleus and in cytoplasm, but it disassembled at the end of prophase Ⅰ. There was also a complex cytoplasmic MN in PMCs, without obvious variation during the prophase Ⅰ. Furthermore, MN in cytoplasmic connections (plasmodesmata and cytoplasmic channels) was noticed to link the frameworks in two neighboring PMCs into one entity. Cytomixis was observed at synizesis of prophase Ⅰ in this experiment, and MN in cytoplasm and in nucleus was noticed to distribute in these granules which migrated from one PMC into its neighboring cell. At this time the nucleus moved aside from center of the PMC, but the rest of the cell was still fulfilled with MN filaments. The relationships of nuclear MN with nucleolus and chromosomes, lamina with nucleus, as well as intra- and intercellular MN with cytomixis are discussed in this paper.     

The Relationship Between the Intercellular Chromatin Migration of Pollen Mother Cells and the Changes of Chromosome Numbers During the Genesis of Male Gametes in Allium Cepa

During the genesis of microspores and male gametes, the percentages of cells with an increas- ed and decreased chromosome number at metaphase Ⅱ, mitotic metaphase of microspores and generative cells approximated to the one at previous stage (metaphase Ⅰ, metaphase Il, and microspores) respectively, and the one at metaphase 1 again approximated to the percentages of chromatin intercellular migration of type 2.3→1 and 1→2.3 respectively, which had no significant diversity statistically. According to this fact, it was considered that the changes of chromosome numbers were related to the chromatin intercellular migration at synizesis stage and that pollen mother cells with an abnormal chromosome number at metaphase Ⅰ basically were able to continue developing untill the formation of male gametes.     

葱的无丝分裂和核物质穿壁运动的细胞胚胎学研究

1.核穿壁运动一般系经胞间联丝的孔道,但是,有时核仁突破细胞壁,核物质经由该破裂的小孔转移,间或细胞壁先行溶解或破裂,于是核物质胞间转移自无障碍。所以胞间联丝的孔道是核穿壁一般的,而非唯一的,必然的通道。2.乾置的葱叶及成熟花粉,核物质穿壁频繁,而花粉发芽时,花粉管内的核物质穿出侧壁例甚罕见。由此,吸水,有氧呼吸,并非核物质穿壁的先决条件。细胞质川流对温度很敏感,而核物质(包括核液与染色质)穿壁,对 温度不敏感。细胞质川流有一定方向,而核物质穿壁无一定方向。细胞质川流只限于胞间内,而核物质穿壁有穿出有机体外。所以细胞质川流或核液川流作为核物质穿壁运动的推动力,难于成立。