Fine Structure of Nucellar Cells During Development of the Embryo Sac in Oenothera biennis L.

Developing nucellar cells in Oenothera biennis L. present distinctpatterns of differentiation at the chalaza and around the embryosac. The cytoplasm of nucellar cells surrounding the tetradof megaspores displays cytolysomes, lipid bodies and membranesof smooth ER enveloping different cytoplasmic components. Concomitantto the differentiation of the embryo sac the nucellar cellsconstituting these ‘parietal layers’ undergo cytoplasmicdegeneration with shrinkage and flattening. In addition to theregular nucellar cells the chalaza at this stage presents threeother types: One with pycnotic nuclei, paramural bodies andcytoplasm filled with polymorphic vacuoles containing membranes,granular or flocculent material and multivesicular bodies. Asecond cell type shows swollen perinuclear cisternae aroundtheir pycnotic nuclei and large cytoplasmic vacuoles accumulatingtannins. The third type of cells is characterized by large numbersof starch grains and advanced disorganization of cytoplasmicorganelles; these cells probably become reservoirs after death. Oenothera biennis L., evening primrose, embryo sac, nucellus, cytolysomes, ultrastructure     

小麦雌配子体发育过程中酸性磷酸酶活性定位

在小麦(Triticum aestivum L.)雌配子体发育过程中,胚囊周围邻近的珠心细胞退化降解,并出现很高的酸性磷酸酶反应,特别是合点部分最强。电镜细胞化学定位也表明退化珠心细胞质中有强烈的酸性磷酸酶活力,它们存在于多层环状的胞质结构中,而远离胚囊的非退化珠心细胞中无上述结构,酸性磷酸酶活性仅出现于液泡中。认为珠心细胞的退化是一种自溶现象。从功能大孢子至七细胞胚囊期,胚囊内部胞质酸性磷酸酶活性很低,合点与珠孔两端的反应强度无明显区別。后期成熟胚囊阶段,反足细胞中出现强烈酸性磷酸酶活性,中央细胞次之,而助细胞及卵细胞中很弱。     

小麦珠心细胞衰退过程中ATP酶的超微细胞化学定位

采用磷酸铅沉淀技术对小麦（Ｔｒｉｔｉｃｕｍ ａｅｓｔｉｖｕｍ ）珠心细胞衰退过程进行了ＡＴＰ酶的超微细胞化学定位。初始衰退的珠心细胞,ＡＴＰ酶只定位于细胞膜上,其它部位未见有ＡＴＰ酶活性。衰退中期的珠心细胞,细胞膜上ＡＴＰ酶活性减弱并逐渐消失;细胞核染色质和细胞质中一些细胞器上存在ＡＴＰ酶活性。在严重衰退的珠心细胞中,只在细胞核染色质上存在ＡＴＰ酶活性。珠心细胞的细胞核以两种方式衰退。衰退的细胞核染色质碎片仍存在ＡＴＰ酶活性,并向胚囊方向转移。推测小麦珠心细胞衰退过程中细胞膜上ＡＴＰ酶变化反映了珠心细胞生理状态转变;细胞核染色质上ＡＴＰ酶与其形态变化和运动等有关     

Ultracytochemical Localization of ATPase Activity in the Degenerating Nucellar Cells of Wheat During Degeneration

Ultracytochemical localization of ATPase activity was carried out using a lead phosphate precipitation technique in the nucellar cells of wheat during degeneration. ATPase was only localized on the plasma membranes of nueellar cells at the. early degenerative stage, then decreased and disappeared at the mid-degenerative stage. Meantime it was also observed in the nuclear chromatin and some cytoplasmic organelles. ATPase activity was only observed in the nuclear chromatin in the extremely degenerated nucellar cells. Two patterns of unclear degeneration was found in the degenerated nucellar cells. A lot of small fragments with ATPase from the degenerated nuclei moved toward the embryo sac. It is suggested that the change of ATPase activity on the plasma membranes is related to the physiological change of nucellar cells, and that in the nuclear chromatin is associated with the stages movement of chromatin during the process of nucellar cells degeneration.     

小麦珠心细胞衰退过程酸性磷酸酶的超微细胞化学定位(英文)

采用磷酸铅盐沉淀技术对小麦（ Ｔｒｉｔｉｃｕｍ ａｅｓｔｉｖｕｍ Ｌ．） 珠心细胞衰退过程进行了酸性磷酸酶的超微细胞化学定位研究。结果显示,在未有明显衰退迹象的一些珠心细胞中,酸性磷酸酶只出现在细胞核轻微凝聚的染色质上。随珠心细胞衰退程度的逐渐增大,其衰退特征越来越明显,酸性磷酸酶依次在细胞质中较小液泡、细胞壁、线粒体、质体以及内质网等结构上出现活性反应。紧连胚囊的珠心细胞衰退程度最大,细胞严重变形,酸性磷酸酶定位于细胞绝大部分结构中,但此时变形的细胞核则无酸性磷酸酶活性反应。研究结果表明,小麦珠心细胞的衰退过程中,酸性磷酸酶存在一个有规律的变化,支持珠心细胞的衰退是属于细胞程序性死亡类型的观点     

Ultracytochemical Localization of Acid Phosphatase in Nucellar Cells of Wheat During Degeneration

The distribution of acid phosphatase activity in nucellar ceils of wheat ( Triticum aestivum L. ) during degeneration has been studied using the lead precipitation method at the electron microscopic level. Acid phosphatase was localized in the slightly condensed nuclear chromatin in nucellar cells without any sign of ultrastructural degeneration. As the nuceilar cells started degenerating, the enzyme activity in the cell was observed, in the order from small vacuoles to cell walls, mitochondria, plastids and endoplasmic reticulum. Enzyme activity was the highest in most components of the nuceilar ceils adjacent to the embryo sac where the degeneration of nucellar cells was the strongest, but it was not observed in the nuclei of the degenerated nucel]ar cells. The results indicated that the degeneration of nucellar cells was a progressive and orderly process and supported that the degeneration of nuceilar cells was a programmed cell death.     

小麦受精过程中酸性磷酸酶的超微细胞化学定位

小麦（Ｔｒｉｔｉｃｕｍ ａｅｓｔｉｖｕｍ ）受精前成熟胚囊,除胚囊中央细胞的合点端细胞质中有酸性磷酸酶外,其余部位均未发现酸性磷酸酶。受精时期,以下部位存在酸性磷酸酶活性：卵细胞的细胞核内一部分染色质和细胞质中大部分线粒体;精、卵核融合时两核的核周腔内;退化助细胞合点端细胞质和一些液泡内;进入雌性细胞中的两个精核;胚囊各成员细胞的细胞壁及胚囊周围珠心细胞的细胞壁。二细胞原胚中未见有酸性磷酸酶。早期胚乳游离核染色质上有酸性磷酸酶。小麦受精过程酸性磷酸酶的分布特点可能与卵细胞生理状态的变化和细胞质中线粒体的改组、助细胞的退化、精核的生理状态以及精核与卵核的核膜融合等有关。     

The Ultracytochemical Localzation of Acid Phosphatase Activity in Wheat During Fertilization

No acid phosphatase activity was observed in the mature embryo sac of wheat (Triticum aestivum) except the chalazal cytoplasm Of the central cell before fertilization. During fertilization, acid phosphataseactivity was observed in the following loci: part of chromatin of the egg nucleus and most of the mitochondria in the egg cytoplasm; the perinuclear spaces of the egg and sperm nuclei at the fusion of the egg and sperm nuclei; the chalazal cytoplasm and some vacuoles of the degenerated synergid; two sperm nuclei within the cytoplasm of female cells; the cell wall of each cell of the embryo sac and that of the nucellar cells surrounding the embryo sac. No acid phosphatase was observed in the two-celled proembryo. Dense enzyme reaction product was localized in the chromatin of the free nuclei at early stage of the endosperm. The characteristic of acid phosphatase distribution during fertilization may be associated with the physiological change of the egg Cell, the reorganization of mitochondria in the egg cell cytoplasm, the degeneration of one of the two synergids, the physiological state of the sperm nuclei and the nuclear membrane fusion of the egg and sperm nuclei.     

花椒珠心胚的超微结构及珠心细胞ATP酶的细胞化学定位

应用透射电镜对花椒（Xanthoxylum bungeanum Maxim)珠心胚原始细胞,多细胞原胚和此时期的珠心细胞及其ATP酶的分布进行了详细的观察,珠心胚原努细胞具厚的细胞壁,明显分为电子致密的外层和电子透明的内层,无胞间连丝,大的核中未见核仁,细胞质富含细胞器,多细胞原胚的壁比原始细胞的薄,电子透明,均质,具胞间连丝,核体积增大,核仁1至2个,细胞质中细胞数的数量明显增加,珠孔端的珠心细胞比胚性细胞体积大,细胞液泡化程度高,细胞质稀薄而呈现衰退趋势,ATP酶分布于液泡膜及液泡液中,与胚性细胞相接触的最内层珠心细胞胞质降解,核严重变形,最终细胞解体,此时无ATP酶活性反应。     

Embryological Studies on Apomixis in Pennisetum squamulatum

Studies on the formation and development of the embryo sac of the apomictic material of Pennisetum squamulatum Fresen indicated that normal archesporial cell did form with consequent development of a megaspore mother cell and later meiotic division to give rise to a triad. But invariably the megaspore mother cell and the triad underwent degeneration after formation. During the period of formation or degeneration of the megaspore or the triad a number of nucellar cells around the degenerated sexual cell became much enlarged. Frequently, one of the enlarging nucellar cells near the micropylar end became vacuolated and then developed into an aposporous uninucleate embryo sac, which underwent two further mitotic divisions to form an aposporous four-nucleate embryo sac, where the four nuclei remained in the micropylar end. Thus in the mature aposporous embryo sac there were one egg cell, one synergid and one central cell (containing two polar nuclei). Antipodal cells were completely lacking. The pattern of development of the aposporous embryo sac resembles the panicum type. There were two types of embryo formed during apomictic development namely ( 1 ) The pre-genesis embryo--embryo formed without fertilization, 1 to 2 days before anthesis, and (2) The late-genesis embryo--derived from the unfertilized egg cells, 3 to 4 days after anthesis. In the late-genesis embryo type, the egg cell divided after the secondary nucleus has undergone division to form the endosperm nuclei. All egg cells developed vacuoles before they differentiated into embryos. The development of the aposporous embryo followed the sequence of the formation of globular, pearshaped embryo and full stages of differentiation. The unfertilized secondary nucleus divides to form free endosperm nuclei after being stimulated by pollination. The development of the endosperm belongs to the nuclear-type.     

花椒球心胚及胚乳的发生和发育

对花椒珠心胚及胚乳的发生和发育过程进行了详细的细胞学及细胞学研究。主要研究结果如下;珠心胚发生前,有性胚囊发育过程中从大孢子发生到胚囊形成的各个阶段均可发生退化,退化频率５０％,未退化的胚囊发育成熟,成熟胚囊仅含卵器和两个极核。卵器最终退化,极核不经受精自发形成胚肥。当胚乳游离核达到１５或３２个时,最早的珠心胚原始细胞由靠近胚囊球孔端的珠心细胞分化形成。随着子房生长,多个原始细胞持续不断地从珠孔端     

鹤顶兰胚囊发育过程中Ca~（2＋）分布的超微细胞化学定位（英文）

用焦锑酸盐沉淀法对鹤顶兰（Phaius tankervilliae）胚囊发育过程中的Ca2＋状态进行超微细胞化学定位。观察结果发现：功能大孢子时期,珠孔端的胚囊壁上开始出现小颗粒的Ca2＋沉淀,但功能大孢子细胞内未见明显的Ca2＋标记;四核胚囊时期胚囊壁上的Ca2＋沉淀明显增多,液泡膜上有Ca2＋沉淀出现,珠孔处的Ca2＋沉淀颗粒较大;成熟胚囊时期,胚囊壁上的Ca2＋沉淀进一步增多,且胚囊内Ca2＋分布明显增多,且极性明显,珠孔端助细胞、卵细胞比合点端反足细胞有更多的Ca2＋沉淀。鹤顶兰成熟胚囊内Ca2＋积累的来源有：（1）在胚囊成熟前主要由珠被细胞、珠细胞通过胞间连丝向胚囊运输;（2）以沉淀有大量Ca2＋的小泡形式跨过胚囊壁进入胚囊。     

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 Embryology of Nyssa sinensis Oliv. (Nyssaceae)

The flower develops in March and blossoms in early May in Nanjing. The cytokinesis of microsporocytes is simultaneous and most tetrads are tetrahedral. The tapetum is secretory and the nuclei become polyploid at last. The style is solid and most ovaries are unilocular, rarely bilocular. The ovule is pendulous, anatropous and unitegmic. The nucellus is pseudocrassinucellate. An obturator formed by transmitting tissue covers the micropyle. The raphe vascular strand extends into the integument when it reaches the chalaza and on a whole keeps a “U” shape. The endothelium cell is uninucleate. In most cases no nucellar cap is formed. No hypostase is found below the embryo sac. The archesporium is one-celled. The embryo sac development conforms to the Polygonum or Allium types. The degeneration of the megaspores in the linear tetrad usually occurs from the chalazal toward the micropylar end. Two synergids persist during fertilization. Three antipodal cells are uninucleate and ephemeral. Two polar nuclei fuse at the time of fertilization. The fertilization type accords with porogamy. The syngamy is premitotic. The development of endosperm is cellular. The initial four successive divisions of the primary endosperm cell are transverse-verticaltransverse-transverse subsequently, giving rise to sixteen cells of the early endosperm. The mature embryo is straight and nearly as long as the endospermous seed. The cotyledons are more or less cordate at base. The seedoat is thin and composed of 5-11 layers of compressed cells. Neither embryo nor endosperm contain the alkaloid camptothecine. The major similarities of Nyssa sinensis to the American nyssas in embryology, which may be a counted as the generic features, are the polyploid tapetum cells, the unitegmic ovule with U-shaped vascular strand, the direct enlargement of the archesporial cell to produce the megasporocyte, the pseudocrassinucellus, the usual absence of the nucellar cap, the Polygonum or Allium type of the embryo sac development, the first degeneration of the metachalazal megaspore, the ephemeral antipodal cells, a single nucleolus in the nucleus ofthe primary endosperm cell, the more or less cordate base of the cotyledons.     

Development of the Female Gametophyte in Hydrobryum griffithii (Podostemaceae)

The development of the female gametophyte in Hydrobryum griffithiiis of the Apinagia type. The chalazal megaspore nucleus of thetwo-nucleate embryo sac completely degenerates, and only themicropylar megaspore nucleus contributes to the four nucleipresent in the organized embryo sac. The female gametophyteconsists of two synergids, an egg and a haploid central cell.The latter degenerates before the entry of the pollen tube andthere is only syngamy. The nucellar cells below the embryo sacorganize into a nucellar plasmodium.     

水蔗草胚珠附器的研究

本文对水蔗草的胚珠附器进行研究,结果表明：在功能大孢子时期,珠孔端的1～3个珠心细胞开始特化,发育成胚珠附器;胚珠附器发生时,有些胚珠同时出现无孢子生殖原始细 胞;有性生殖和无孢子生殖的胚囊中均有胚珠附器存在;但在无孢子生殖的胚囊中,胚珠附器一般很大,长约是宽的1～３倍;而有性生殖胚囊的胚珠附器的长约是宽的1～２倍;和有性生殖胚囊相比,无孢子生殖胚囊的胚珠附器更加发达;存在发达的胚珠附器是水蔗草无孢子生殖胚囊的特点之一。     

水蔗草胚珠附器的研究

本文对水蔗草的胚珠附器进行研究,结果表明：在功能大孢子时期,珠孔端的1—3个珠心细胞开始特化,发育成胚珠附器;胚珠附器发生时,有些胚珠同时出现无孢子生殖原始细胞;有性生殖和无孢子生殖的胚囊中均有胚珠附器存在;但在无孢子生殖的胚囊中,胚珠附器一般很大,长约是宽的1—3倍;而有性生殖胚囊的胚珠附器的长约是宽的1—2倍;和有性生殖胚囊相比,无孢子生殖胚囊的胚珠附器更加发达;存在发达的胚珠附器是水蔗草无孢子生殖胚囊的特点之一。     

水稻中央细胞发育期间超微结构变化的观察

本文通过透射电镜对水稻受精前胚囊中央细胞发育过程中超微结构的变化进行观察。结果表明,八核胚囊形成后很快就进行细胞化形成7个细胞,其中刚形成的中央细胞由1个大液泡、2个极核（珠孔端和合点端各1个）和一些含有丰富细胞器的胞质组成。中央细胞以后的发育主要是极核的发育和极核周围胞质的变化。极核发育经历以下过程：a．2个核都膨大呈“椭圆”形。核周围胞质呈不对称分布。b．2个核分别向胚囊中央移动并相互靠近。之后2个极核调整排列方式,由纵排（即与胚囊纵轴平行）变成横排。此时期有细胞质“桥”联结珠孔端卵器、2个极核和合点端反足细胞器。c．横排的极核移向卵器,并排列于卵细胞之上。此时胚囊未明显膨大,但极核相靠近的两边核膜有许多处已形成“融合桥”,核周围的胞质也起较大的变化,如质体内淀粉消失和光面内质网增加等。极核进一步发育直至胚囊成熟期间,极核排列方式及其周围胞质组成未观察到明显的变化,但胚囊体积明显增大。     

The embryo sac of Cynara cardunculus: ultrastructure of the development and localisation of the aspartic proteinase cardosin B

Cynara cardunculus is a native plant with flowers that are used traditionally in the manufacture of ewe’s cheese in the Iberian Peninsula. Milk clotting ability of the plant is attributed to the high concentrations of aspartic proteinases (APs), named cardosins, found in the flowers. Although these enzymes are well characterised on a molecular and biochemical basis, the biological role of the majority of plant APs is yet unassigned. We suspected APs play an important role in ovule function, and we characterised the maturation of the ovules of C. cardunculus and its Polygonum-type embryo sacs. The internal layer of the integument differentiates into an endothelium as described for other Asteraceae, with differentiation of two nucellar layers, a podium and a hypostase coinciding with the onset of pollen receptivity. In flowering plants, programmed cell death (PCD) events are essential for the success of nucellar maturation and consequent differentiation of a fully functional embryo sac. In C. cardunculus, nucellar PCD is integral to the maturation of the embryo sac, which in turn is closely correlated with the accumulation of the AP cardosin B specifically in the hypostase. The onset of cardosin B expression temporally coincides with the degeneration of nucellar cells. In fully mature embryo sacs, cardosin B is localised in both the hypostase and epistase, two regions that differentiate through PCD. Thus, cardosin B localisations closely correlate with events of PCD in the nucellus of C. cardunculus suggesting involvement in ovule and embryo sac development and further suggest the biological significance of APs like cardosin B, in this particular process. This work contributes new data to the plant AP research field and indicates an involvement of cardosin B in the PCD-dependent degeneration of the nucellus.