Morphology and wall ultrastructure of the spores of the Lower Devonian plant Oocampsa catheta Andrews et al., 1975

The enigmatic Lower Devonian plant Oocampsa catheta Andrews et al. (Can. J. Bot. 53 (1975) 1719) is considered intermediate between the trimerophytes and progymnosperms. In order to shed light on its evolutionary relationships, the morphology and ultrastructure of its sporangium and spores were analysed using light, scanning electron and transmission electron microscopy. In addition, dispersed spores (Grandispora douglastownense McGregor (Palaeontographica B 142 (1973) 1) and Grandispora ?macrotuberculata (Trudy VNIGNI 37 (1963) 18) McGregor (Palaeontographica B 142 (1973) 1), considered to possibly represent forms derived from O. catheta, were also examined. It is concluded that G. douglastownense and G. ?macrotuberculata are probably end members of the same spore complex and most likely are dispersed spores produced by O. catheta. Oocampsa catheta spores are bilayered. An inner body has an innermost part consisting of continuous, parallel-stacked, laminae and an outermost part consisting of more erratic, anastomosing, laminae. The inner body is surrounded by an homogeneous outer layer that is extended at the equator forming a pseudozona, and is folded on the proximal surface forming the trilete mark and on the distal surface forming spinose ornament. The spores are partially camerate. On the inside of the sporangium wall there is a layer probably representing the residue left following degeneration of a (probably secretory) tapetum. Spore morphology, gross structure and wall ultrastructure are compared to that of extant and fossil plant groups, and it is concluded that the spores of O. catheta are highly distinctive and do not conform closely to any plant group, although they show most in common with the spores of the progymnosperms.     

Sporophyte-gametophyte interactions between anther and male gametophyte in petunia

Sporophyte-gametophyte interactions between anther and male gametophyte were investigated in two (fertile and sterile) clones of petunia (Petunia hybrida L.) with different reproductive strategies. Structural and functional reorganization of sporophyte tissues in the developing anther of fertile clone is closely coordinated with each of the successive stages of male gametophyte development (from meiosis to the formation of binuclear pollen) and comprises not only destruction of tapetum and three middle layers of the wall but also an activation of gas exchange and a rise in the content of sugars (sucrose, fructose, and glucose). In sterile clone, degradation of tapetum and anomalies in the development of sporogenic tissue were simultaneously observed in the prophase of meiosis. The death of microsporocytes and degeneration of tapetum were accompanied by a decrease in the level of sucrose delivered to the anther tissues and changes in the ratio between sucrose and hexoses in favor of glucose.     

Rice (Oryza sativa L.) cultivars tolerant to high temperature at flowering: anther characteristics

We examined the relationship between morphological characteristics of anthers and fertility in japonica rice cultivars subjected to high temperature (37.5(26 degrees C day/night) at flowering. Percentage fertility was negatively correlated with the number of cell layers that separated the anther locule from the lacuna that formed between the septum and the stomium. The cell layers consisted of the remaining septum and degraded tapetum, and serve to keep the adjacent two locules closed. Anther dehiscence therefore requires the rupture of the cell layers. We conclude that the tight closure of the locules by the cell layers delayed locule opening, and decreased fertility at high temperatures.     

Ultrastruktur und Entwicklungsgeschichte des Pollenkitts vonEuphorbia cyparissias,E. palustris undMercurialis perennis (Euphorbiaceae)

Development, fine structure and distribution of pollenkitt is investigated inEuphorbia cyparissias, E. palustris, andMercurialis perennis. The predominantly anemophilousM. perennis produces a great amount of strictly homogeneous pollenkitt, which is deposited in the exine caves. In contrast to this and to all other angiosperms so far investigated, bothEuphorbia species produce large quantities of an extremely inhomogeneous and particular pollenkitt. Its ultrastructure is quite different, both during its development and after its deposition on the exine surface: Lipid particles with different electron density and size are wrapped in a strictly homogeneous electron transparent matrix. This can be considered as new and additional proof for the secondary entomophily ofEuphorbia.

     

Morphology of the retina in deep‐water fish Nezumia sclerorhynchus (Valenciennes, 1838) (Gadiformes: Macrouridae)

Using light microscopy, we examined the retina of benthopelagic fish Nezumia sclerorhynchus. Although the retina is typical of other vertebrates, having three nuclear and two synaptic layers, it presents some features associated with the animal's deep‐sea habitat. A stratum argenteum containing iridescent crystals is located in the choroid. The pigment cell layer shows bulky cells filled with melanin granules but without the typical apical processes. The visual cells, consisting of a big population of rods, are arranged in several banks. No cones were observed. The outer segments are very long and cylindrical, and the inner segments are constituted by a small ellipsoid at the proximal end. The outer nuclear layer contains several rows of oval nuclei, and the spherules in the outer plexiform layer have less regular outlines than nuclei. The inner retina is characterized by very large horizontal cells, and presumable bipolar and amacrine cells separated by large spaces that are occupied by neuronal processes. Finally, the low density of ganglion cells produces a thin nerve fibre layer. The results of this study suggest that the retina of Nezumia sclerorhyncus exhibits high visual sensitivity and that vision is a sense that plays an important role in its behaviour.     

Colchicine inhibits plasmodium formation and disrupts pathways of sporopollenin secretion in the anther tapetum ofTradescantia virginiana L.

Summary During an earlier investigation, microtubules were observed at the periphery of invasion processes in the developing syncytial tapetum ofTradescantia virginiana L. They were also associated with membranous sacs that accumulate adjacent to tetrads, with putative fusion sites where the tapetal plasmodium is initiated, and, in postmeiotic stages, with the perispore membrane that encloses the developing spore cells. Colchicine was administered to developing flower buds to investigate the roles of these microtubules. The results indicate that microtubules neither initiate nor guide the tapetal invasion of the loculus. The treatments, however, resulted in absence of cell coat from invasion processes and prevention of cell fusion. They also inhibited polarized migration of membrane sacs and removed the associated microtubules. The development of an organized secretory apparatus at the perispore membrane was disrupted, with subsequent disordered deposition of sporopollenin in the extracellular spaces of the partially-fused plasmodium. The results suggest that microtubules participate in the formation and internal spatial organization of the tapetal plasmodium, and establishment of a secretory surface that normally produces sporopollenin at the tapetum-microspore interface.     

Isolation and Characterization of a Rice Cysteine Protease Gene, OsCP1, Using T-DNA Gene-Trap System

The T-DNA gene-trap system has been efficiently used to elucidate gene functions in plants. We report here a functional analysis of a cysteine protease gene, OsCP1, isolated from a pool of T-DNA insertional rice. GUS assay with the T-DNA tagged line indicated that the OsCP1 promoter was highly active in the rice anther. Sequence analysis revealed that the deduced amino acid sequence of OsCP1 was homologous to those of papain family cysteine proteases containing the highly conserved interspersed amino acid motif, ERFNIN. This result suggested that the gene encodes a cysteine protease in rice. We also identified a suppressed mutant from T2 progeny of the T-DNA tagged line. The mutant showed a significant defect in pollen development. Taken together, the results demonstrated that OsCP1 is a cysteine protease gene that might play an important role in pollen development.     

高温影响番茄小孢子发育的细胞学研究

以番茄‘Micro-Tom’为材料,利用形态观察、DAPI染色、石蜡切片等方法对正常情况下番茄小孢子发生过程进行时期划分.通过连续7d的高温胁迫((35±1)℃/(30±1)℃)处理试验,结合细胞学观察,研究高温对番茄花粉小孢子发育的影响.研究表明,高温胁迫不仅导致花粉畸形或败育、花粉数量减少、活力低萌发力差,而且还导致花药绒毡层、药隔组织、药室内壁、花药表皮、环状细胞簇等花药细胞结构的发育异常.结果有助于阐明热胁迫对番茄小孢子发育的影响,并为培育耐高温农作物新品种提供思路.     

扁豆绒毡层发育的超微结构研究

应用透射电镜对扁豆绒毡层发育过程进行了研究,主要结果如下：１）首次发现扁豆绒毡层在发育过程中,经历了二交胞质重组（第一次始于减数分裂末期Ⅱ,第二次始于小孢子发育早期）,使绒毡层细胞的活动呈现３个高峰期（即小孢子母细胞减数分裂期、小孢子四分体期一小孢子早期、小孢子晚期－二胞花粉中期）。２绒毡层细胞的分泌作用有３种形式（渗透分泌、胞吐分泌和自溶）。３．首次观察到绒毡层细胞的内切向壁和径向壁经历了两个周