Differential localization of enzymes in the stigmatic exudates ofPrimula obconica

Summary The stigmatic dimorphisms in the distylous speciesPrimula obconica, which has been dealt with in an earlier paper, has been described further. An ultrastructural localization of various enzymes in the exudates is hereby revealed, and evidence is given for intermorph differences. Esterases are confined to the lipid phase of the exudates, including the lipid globuli in the papillae walls of both morphs, but they are not found in the pellicle of the dry thrum stigma. However, this pellicle exhibits acid phosphatase activity, as does the lumen of the blisters in the viscous exudate on pin stigmas. The blisters are presumed to hold the watery phase of the pin secretion. From the present findings and from previous results with LM cytochemical methods it is suggested that the sites of peroxidase activity resemble those of acid phophatases.     

An unusual heteromorphic incompatibility system

Summary By means of intra- and intermorph crosses it has been shown that the distyly in Anchusa officinalis L. is governed by a single diallelic locus with dominance. Presence of the dominant allele is reflected in the short-styled morph, while homozygous recessives become long-styled. Most of the short-styled plants are heterozygous, but homozygotes have been found among the raised progeny resulting from crossings. Diallel crosses have revealed that at least two incompatibility loci must exist. These and the morphological locus segregate independently. The type of incompatibility system is as yet unknown, though the great frequency of non-reciprocal incompatibility points to a sporophytic system.     

Dry stigmas,water and self-incompatibility in Brassica

The evolution of dry stigmas has been accompanied by the development — in the pollen — of mechanisms for accessing water from the stigmatic epidermis. Development of self- and cross-pollen on the stigmatic surface has been examined in Brassica oleracea, focusing on the hydration of the grains. Unlike self-compatible (SC) Arabidopsis thaliana, pollen hydration of self-incompatible (SI) Brassica oleracea is preceded by a latent period of between 30–90 min, which is significantly shortened by inhibition of protein synthesis in the stigma. Physiological experiments, some with isolated pollen coatings, indicate that during the latent period signals passing from the pollen to the sigma are responsible for readying the stigmatic surface for penetration and — after self-pollination — activation of the SI system. The changes at the stigma surface include the expansion of the outer layer of the cell wall beneath the grain. This expansion does not occur following self-pollination, when coating-derived signals stimulate a stigmatic response which interrupts hydration and arrests grain development. Cell manipulation studies suggest that self grains are not inhibited metabolically, but are physiologically isolated from the subjacent stigmatic papilla. This focusing of the SI response at the pollen-stigma interface ensures that a single papilla can simultaneously accept cross-pollen and reject self-grains. The evolution of this highly efficient SI system is disussed in the perspective of pathogen-defence mechanisms known also to be located in epidermal cells.     

The morphology of styles and stigmas inVicia (Leguminosae), and its systematic implications

The morphology and development of styles and stigmas ofVicia, one of the five genera of tribe Vicieae, were studied by scanning electron microscopy to contribute to a revision of infrageneric classification. Among the 22 species examined, variations were found as to: (1) whether a boundary between stigma and style is V-shaped when viewed from the adaxial side or not; (2) whether stylar hairs sprout on all sides of the style or only on the abaxial side; (3) whether a hairy area of the style connects with the stigma area first at lateral sides or at an adaxial side; (4) whether styles are tapered or bottle-neck-shaped; (5) whether styles are straight or bend abaxially. Based on these variations, five morphological types of styles and stigmas were provided with a diagnostic key. Comparisons with related tribes Cicereae, Coronilleae, Galegeae, Hedysareae, Loteae and Trifolieae as possible outgroups suggested that the V-shaped boundary between stigma and style is a synapomorphy of some species withinVicia, and that a dorsally compressed and abaxially tufted style, which was distributed in separate subgenera and sections sensu Kupicha but is now known to occur together with the V-shaped boundary, has evolved only one time in the genus, rather than more than once as supposed earlier.     

Comparative proteomic analysis reveals similar and distinct features of proteins in dry and wet stigmas

Angiosperm stigma supports compatible pollen germination and tube growth, resulting in fertilization and seed production. Stigmas are mainly divided into two types, dry and wet, according to the absence or presence of exudates on their surfaces. Here, we used 2DE and MS to identify proteins specifically and preferentially expressed in the stigmas of maize (Zea Mays, dry stigma) and tobacco (Nicotiana tabacum, wet stigma), as well as proteins rinsed from the surface of the tobacco stigma. We found that the specifically and preferentially expressed proteins in maize and tobacco stigmas share similar distributions in functional categories. However, these proteins showed important difference between dry and wet stigmas in a few aspects, such as protein homology in "signal transduction" and "lipid metabolism," relative expression levels of proteins containing signal peptides and proteins in "defense and stress response." These different features might be related to the specific structures and functions of dry and wet stigmas. The possible roles of some stigma-expressed proteins were discussed. Our results provide important information on functions of proteins in dry and wet stigmas and reveal aspects of conservation and divergence between dry and wet stigmas at the proteomic level.     

Studies on heteromorphic self-incompatibility systems: Physiological aspects of the incompatibility system of Primula obconica

Summary In Primula obconica, a species with a heteromorphic self-incompatibility system, the distinction between compatible and incompatible pollen tubes takes place on the stigma surface in thrum flowers, self tubes growing randomly over the papillar cells. No differences were seen between self and cross tube behaviour on the pin stigma surface, but self tubes were inhibited within the stigmatic tissue with differences in tube length evident after 24 h. The stigma surface bears a proteinaceous pellicle and binds the lectin Concanavalin A. Removal of the stigma removes the incompatibility barrier in mature gynoecia. Bud pollination shows that pollen tubes cannot grow in a normal manner on immature stigmas; the random growth of tubes over the stigma surface resembles that of mature thrum selfs. Fewer compatible tubes reach the style base of young gynoecia and smaller numbers of seeds are set than in mature flowers. Pin and thrum pollen grains germinate and grow in aqueous media, thrum tubes growing longer than pin. The presence of H₃BO₄ and CaCl₂ in the growth medium promotes tube elongation and lengths equivalent to compatible styles can be obtained. The pollen grains have proteinaceous materials in their walls which diffuse out on moistening. Prolonged washing in aqueous media removes these materials but the incompatibility reaction remains unchanged. Thus the incompatibility reaction is between pollen tubes and stigmatic tissue and differs from the homomorphic, sporophytic system where pollen wall proteins elicit the incompatibility response.     

Structure of the style and wet non-papillate stigma of Colophospermum mopane, Caesalpinioideae: Detarieae

The capitate stigma of Colophospermum mopane (Kirk ex Benth.) Kirk ex J. Leonard is an intensely folded bilobed structure. The epidermal layer of the stigma consists of non-papillate cells. Before anthesis the epidermis is covered with a cuticle and thin proteinaceous layer. Elongated subepidermal cells constitute the secretory zone. Cell disintegration in the central region of each stigma lobe leads to cavities that become connected to the central cavity in the style. During early anthesis it appears as if the receptive surface of the stigma is confined to the depressions of the stigma surface and to the cleft between the two stigma lobes as the secretory product and pollen grains are mainly confined to these areas. The secretory products of the stigma and style are released during five different stages from prior to anthesis to late anthesis. The stigmatic exudate appears complex and consists of carbohydrates, proteins and lipids. The style has a hollow, lysigenous, fluid-filled canal that is not lined with an epidermal layer or cuticle. The stylar canal is continuous with the opening between the two stigma lobes and provides an open route for the passage of exudate. The stylar exudate is PAS-positive. The dorsal and ventral bundles that supply the style branch in such a way as to almost form a cylinder around the central transmitting tissue and stylar canal. New sieve elements proliferate before anthesis.  © 2002 The Linnean Society of London, Botanical Journal of the Linnean Society , 2002, 139 , 295–304.     

Ultrastructure of the dimorphic pollen and stigmas of the cleistogamous species,Collomia grandiflora (Polemoniaceae)

Summary An ultrastructural study of the pollen and stigma of the dimorphic flowers in the cleistogamous speciesCollomia grandiflora reveals significant differences in cytoplasmic features in the pollen and wall features in the papillae. Both pollen types contain lipid and starch reserves, but the smaller CL (cleistogamous) pollen shows a much greater abundance of starch compared to the CH (chasmogamous) pollen. In addition to the papular size and shape differences between the two stigma types, there is a more extensive cuticular stretching and wall microfibrillar loosening over the CH papillar tip. There is no apparent pellicle on the cuticle surface of either type of papilla, only scattered lipidic deposits. It is proposed that these structural differences may contribute to the cross incompatibility between the two floral morphs.     

Distyly and incompatibility inVillarsia congestiflora (Menyanthaceae), with comparative remarks onV. capitata

The Western Australian annual of restricted distribution,Villarsia congestiflora, has distylous flowers and pollen-size heteromorphism. Results of a crossing program indicate that this species is strongly self-incompatible, that crosses among individuals of the same morph produce little or no seed, and that intermorph crosses produce copious seed. The species shares a number of morphological and ecological traits withV. capitata, another distylous, self-incompatible annual species of Western Australia with a greater area of distribution. Artificial hybrids between the two, however, showed reduced pollen stainability. Both species combine a number of specialized morphological features with a breeding system that is primitive for the familyMenyanthaceae.     

Heterostyly inPrimula. 1. Fine-structural and cytochemical features of the stigma and style inPrimula vulgaris huds

Summary The stigmas of the heterostylous genusPrimula are of the dry type without a free-flowing surface secretion. The papillae of the stigma surface cells of the two morphs, in pin (stigma exserted) and thrum (stamens exserted), bear a thin proteinaceous surface pellicle, overlying a discontinuous cuticle. The vacuoles of the papillate cells contain tannins, and tannin cells extend in files through the stigma heads and form a loose sheath surrounding the pollen-tube transmitting tract in the styles. The cells of the transmitting tissue in the stigma heads have a normal complement of organelles, and abundant ribosomal endoplasmic reticulum. The intercellular spaces contain an internal secretion which reacts cytochemically for both carbohydrate and protein. The transmitting tract in the styles forms a central core surrounded by several vascular strands. The cells are elongated, and the intercellular spaces here also have a carbohydrate-protein content. In a compatible pollination, thrum pollen tubes enter the stigma by penetrating the cuticle at the tip or on the flank of the pin papilla. Pin tubes on the thrum stigma enter between adjacent papillae, penetrating the thin cuticle at the base. The tubes grow through the transmitting tracts in the intercellular material.     

Suberized tyloses in trees: An ultrastructural and cytochemical study

The nature of the wall layers observed in suberized tyloses was studied in Populus basalmifera L., Ulmus americana L. and Quercus rubra L. As the suberin layers were present only in tyloses that had completed their expansion, most of the results concern mature tyloses. The cyto- and immunocytochemical tests were conducted, respectively, with an exoglucanase having a binding affinity for β(1→4)-D-glucans, the subunits of cellulose, and with two monoclonal antibodies specific for un-esterified and esterified pectic molecules. In the three species, labelling for pectic compounds was intense over the external layer of tyloses but usually more dispersed or nearly absent over the layer corresponding to a primary wall that was, however, intensely labelled for β(1→4)-D-glucans. The outer wall layer, comparable to a middle lamella in mature tyloses, was continuous with similar material that appeared to be secreted by the tylosis. This material was particularly abundant in pit chambers, in void spaces between the tylosis and the vessel wall, particularly at the junction of the vessel and two adjacent cells, and close to the rim of vessel perforation plates. In P. balsamifera, a single suberized layer or occasionally a succession of suberized and cellulose-containing layers was observed internal to the tylosis primary wall. In U. americana, the wall of tylosis was similar to that of P. balsamifera except that, at times, a secondary-wall-like layer was formed and only a single suberized layer was observed. In Q. rubra, the suberized layer was always observed internal to the tylosis secondary wall. Simple pits were also constantly noted in Q. rubra tyloses. The occasional occurrence of a cellulosic layer internally to the suberized layer was observed in the three species. Histochemical tests revealed that lignin was also an important component of the tylosis wall. The tyloses frequently contained phenolic compounds in close association with the suberized layers. The significance of the formation of suberized tyloses in trees is discussed.     

Ultrastructural changes in suspension culture cells of Panicum maximum during cryopreservation

A Panicum maximum cell suspension was used to study ultrastructural changes during cryopreservation. Pregrowing the cells in mannitol caused reduction in the vacuolar volume by redistribution of the large central vacuole into a number of smaller vesicles. Invaginations were formed in the plasma membrane of the cells, to accommodate the reduced cell volume. Swelling of organelles occurred during different stages of cryopreservation. The cisternae of the endoplasmic reticulum dilated and formed vesicles. Although some damage was apparent, organelles were still recognizable in cells frozen slowly and freeze-fixed at –10°C. The cells were able to repair such damage within two days in culture, and regained their normal appearance. Cells frozen slowly without any cryoprotection, and cells frozen rapidly by direct immersion into liquid nitrogen after cryoprotection, were lethally damaged by destruction of membranous structures. Osmiophilic granules were found along the plasma membrane of lethally damaged cells, indicating that their formation is a consequence of freeze damage, rather than a mechanism to prevent injury.Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid - DMSO dimethyl sulfoxide     

含笑花药发育的超微结构研究

对含笑花药发育中的超微结构变化进行观察,结果显示:(1)花粉发育中有三次液泡变化过程——第一次是小孢子母细胞在形成时内部出现了液泡,这可能与胼胝质壁的形成有关;第二次是在小孢子母细胞减数分裂之前,细胞内壁纤维素降解区域形成液泡,它的功能可能是消化原有的纤维素细胞壁;第三次是在小孢子液泡化时期,形成的大液泡将细胞核挤到边缘,产生极性。(2)含笑花粉在小孢子早期形成花粉外壁外层,花粉外壁内层在小孢子晚期形成,而花粉内壁是在二胞花粉早期形成;花粉成熟时,表面上沉积了绒毡层细胞的降解物而形成了花粉覆盖物。研究认为,含笑花粉原外壁的形成可能与母细胞胼胝质壁有关,而由绒毡层细胞提供的孢粉素物质按一定结构建成了花粉覆盖物。     

Ultrastructural studies of dorsal ciliated organs in Spionidae (Annelida: Polychaeta)

The distribution and structural components of dorsal ciliated organs (dco) in 15 species of the Spionidae were studied by scanning- and transmission electron microscopy. Based on the distribution patterns of dco, the investigated species are divided into four non-systematic groups: (I) paired anterior dco, (II) paired dco extending posteriorly for several chaetigers, (III) paired anterior dco in combination with unpaired, sexually dimorphic, metameric dco, and (IV) paired anterior dco in combination with paired, metameric dco. Previous ultrastructural studies have only included species possessing organs of groups I and III. In the present investigation the ultrastructure of dco found in Laonice bahusiensis and Spio cf. filicornis (species with dco of groups II and IV) is studied in an attempt to consider their homology. Apart from the metameric dco of group III, similarities of the cellular components of the dco indicate a homology to nuchal organs.     

Ultrastructural characteristics of an achlorophyllous callus line ofLotus corniculatus

Summary An achlorophyllus isoline originated spontaneously from a green callus line derived from a genotype ofLotus corniculatus L. cv. Leo. This isoline is characterized by significantly faster callus growth than the green line and by differentiating significantly fewer plants per gram of callus when subcultured on a shoot differentiating medium. The isoline does, however, develop loci of meristematic cells when transferred from a medium containing 2,4-D to one containing benzyl adenine. After this transfer, plastids, mitochondria, dictyosomes, and endoplasmic reticulum appear to be more prevalent in many cells. Nuclei and nucleoli become more prominent in these cells. Ingrowths, lined with plasmalemma, develop along the outer tangential cell wall of many cells in contact with the culture medium and along various walls of cells found in the interior of the callus. These cells have characteristics of transfer cells. A few cells at the periphery of meristematic groups of cells elaborate lamellar structures similar to suberin lamellae in their cell walls.     

Ultrastructural and cytochemical aspects of induced apogamy following abscisic acid pre-treatment of secondary moss protonema

Abscisic acid (ABA) treatment of secondary protonema of Physcomitrium pyriforme Brid in the presence of sucrose does not prevent cell division but results in shorter cells with vesicular cytoplasm and an accumulation of lipid. When transferred to sucrose medium without ABA and with low irradiance isodiametric intercalary cells are cut off which give rise to apogamous sporophytes either directly or after the formation of a small amount of callus. The organization of the cells leading up to the apogamous sporophyte is described. The cells initiating the sporophyte develop dense cytoplasm and the walls become labyrinthine and callosed, but they do not form any recognizable placenta. It is proposed that labyrinthine walls are a consequence of a perturbation of cell wall metabolism as growth changes from gametophytic to sporophytic. The use of the term transfer cell for this kind of cell is questioned and the need for a causal approach to the investigation of labyrinthine walls is stressed.     

Reconstructing dry and wet summers in SE Slovenia from oak tree-ring series

We present a reconstruction of the June weather conditions in SE Slovenia from 1497 to 2003 based on the De Martonne aridity index (AI). The AI were derived from oak (Quercus spp.) tree-ring series of living trees and historic wood, which exhibited a clear response to June precipitation (positive) and temperature (negative). In the reconstructed AI time series we classified negative and positive deviations from the mean as strong (+/-1.28 SD) or extreme (+/-1.645 SD), and thus identified 50 years with a likely dry and hot June, as well as 40 years with a likely wet and cool June. Historical sources and chronicles were used to validate the AI reconstruction in the pre-instrumental period before 1896. The years 1501, 1540, 1546, 1616, 1718, 1788, 1822, 1834, 1839 and 1841, with extreme or strong negative AI deviations, are mentioned in Slovenian chronicles because of crop failures, droughts or extremely hot summers. The years 1691, 1705, 1798, 1799 and 1847, with extreme or strong positive AI deviations, are mentioned as years with a cool and rainy summer. We discuss the relevance of June weather conditions for the growth of plants in the region between the Alps, the Mediterranean and the continental Pannonian lowland, and the possible changes due to the current climate change scenario.     

Development and cell surface of a non-syncytial invasive tapetum inCanna: Ultrastructural,freeze-substitution,cytochemical and immunofluorescence study

Summary The anther ofCanna indica L. ×C. sp. hybrid contains a hitherto uncharacterized non-syncytial, invasive category of tapetum. With the onset of prophase I the tapetal walls are dissolved and the released protoplasts migrate into the loculus, where they stay discrete. Concomitant with the dissolution of walls the tapetal protoplasts develop a 17 nm thick extracellular granulo-fibrillar cell coat. This feature develops in the synchronous phase of tapetal development. The cell coat reacts positively with ruthenium red, potassium ferrocyanide, ConA-FITC and in the Thiéry reaction. Immunofluorescence microscopy using anti-tubulin revealed that even after the migration of tapetal cells into the loculus, the microtubules retain a predominant orientation in the cell cortex, probably derived from that in the original tapetal walled cells. This order is lost during late post-meiotic stages when the cells distort and can produce amoeboid processes. The microtubule orientation is correlated with that of the cell coat fibrils. Tapetal cells vary in ultrastructure and the density of cell coat fibrils after their migration into the loculus, but the cell coat persists until the cells degenerate. It is surmised that development of the cell coat relates to the lack of cell fusion and that the cortical microtubules help to sustain cell form. During post-meiotic stages the free tapetal cells develop massive peripheral arrays of interconnected ER cisternae, probably as part of a secretory apparatus which matures when the spores are producing their ornamented walls. Buds grown in colchicine solution showed accumulation of sporopolleninlike granules in all extracellular spaces of the anther cavity.     

阔鳞瘤蕨(水龙骨科)卵细胞发育超微结构观察

水龙骨科是蕨类植物中最进化的类群,该文采用超微技术对水龙骨科的阔鳞瘤蕨(Phymatosorus hainanensis)卵发育过程进行观察,以完善薄囊蕨植物卵发生的资料,为揭示蕨类植物的有性生殖及演化机制奠定基础。结果表明:(1)幼卵、颈沟细胞、腹沟细胞通过胞间连丝紧密连接。(2)发育过程中,卵与腹沟细胞之间细胞壁显著加厚,将卵细胞与腹沟细胞隔离。(3)在壁的下方产生分离腔,内含大量不定形物质,但卵细胞与腹沟细胞在中间处始终相连。(4)分离腔中的不定形物质沉积在卵细胞质膜外形成了一层加厚的卵膜,而在连接区(孔区)处不形成卵膜,该位置最终形成了受精孔。(5)卵细胞核变得高度不规则,近成熟时卵核产生了大量的核外突。     

Bacterial adhesion to different termite flagellates: Ultrastructural and functional evidence for distinct molecular attachment modes

Summary The attachment modes of rodlike ectobiotic bacteria to the surface of two different termite flagellates were studied.Devescovina glabra was covered by laterally attached bacteria. Treatment with chemicals that disturb hydrophobic interactions and solubilize proteins removed the ectobionts. Freeze-fracture and freeze-etching electron microscopy revealed rows of intramembrane particles that occurred exclusively along the attachment sites. The adhering Gram-negative bacteria possessed an S-layer (surface layer) composed of globular protein particles. The S-layer could be removed by protein-solubilizing chemicals, e.g., urea, as shown by ultrathin-section electron microscopy. Therefore, it seems plausible that the attachment was mediated by hydrophobic interactions between the flagellate's plasma membrane and the S-layer of the bacteria. The bacteria of the second flagellate,Joenia annectens, adhered by their tips. The attachment was extremely strong. Chemicals disturbing ionic or hydrophobic bindings or solubilizing proteins did not detach the ectobionts. Globular intramembrane protein particles were preferentially found in a ringlike array at the external fracture face of the flagellate's contact sites.Abbreviations DIC differential interference contrast - EGTA ethylene glycol-bis(-aminoethyl ether) N,N,N,N-tetraacetic acid - TEM transmission electron microscope - Tween 20 polyoxyethylenesorbitan