Characteristics of spore germination and protonemal development in Hypnum pacleseens

The spore germination, protonemal development, and gametophyte differentiation of Hypnum pacleseens were observed in cultivation. Photomicrographs showed that spore germination of Hypnum pacleseens occured within the exospore. Its protonema is massive with filamentous chloronema formed inside. The terminal part of the chloronema differentiated into filamentous caulonema and its rhizoid was derived from the apical cell of the filamentous chloronema. The initial cell of gametophyte differentiated from chloronema and caulonema. Sporeling-type of Hypnum pacleseens is developmentally similar to Glyphmitrium-type.     

Characteristics of spore germination and protonemal development in Hypnum pacleseens

The spore germination,protonemal development,and gametophyte differentiation of Hypnum pacleseens were observed in cultivation.Photomicrographs showed that spore germination of Hypnum pacleseens occured within the exospore.Its protonema is massive with filamentous chloronema formed inside.The terminal part of the chloronema differentiated into filamentous caulonema and its rhizoid was derived from the apical cell of the filamentous chloronema.The initial cell of gametophyte differentiated from chloronema and caulonema.Sporeling type of Hypnum pacleseens is developmentally similar to Glyphmitrium-type.     

The sporeling development in Frullania tamarisci (L.) Dum

Abstract

The sporeling development in Frullania tamarisici (L.) Dum. ssp. tamarisci is described for the first time. Its pattern belongs to the Frullania-type in which a globose, many-celled protonema is formed within the stretched exospore. The primary leaves are ovate to oblong, followed by the saccate-inflated juvenile leaves. In the juvenile stage each underleaf is associated with a single leaf.     

垂蒴真藓原丝体发育特征的研究

在室内培养垂蒴真藓(Bryum uliginosum)孢子的基础上,对其孢子萌发、原丝体发育及配子体发生的全过程进行了跟踪观察。结果表明：该种孢子萌发后直接产生绿丝体。而轴丝体和假根仅在绿丝体上产生;配子体原始细胞产生于绿丝体基部细胞或轴丝体上。由此可以看出：垂蒴真藓属于真藓型孢子萌发型(Bryum-type)。     

Ultrastructural study of spore wall morphogenesis inOphioglossum thermale kom. var.nipponicum (Miyabe et Kudo) nishida

Spore wall morphogenesis ofOphioglossum thermale var.nipponicum was examined by transmission electron microscopy. The spore wall of this species consists of three layers: endospore, exospore, and perispore. The spore wall development begins at the tetrad stage. At first, the outer undulating lamellar layer of the exospore (Lo) is formed on the spore plasma membrane in advance of the inner accumulating lamellar layer (Li) of the exospore. Next, the homogeneous layer of the exospore (H) is deposited on the outer lamellar layer. Both lamellar layers may be derived from spore cytoplasm; and the homogeneous layer, from the tapetum. Then the endospore (EN) is formed. It may be derived from spore cytoplasm. The membranous perispore (PE), derived from the tapetum, covers the exospore surface as the final layer. Though the ornamentation of this species differs distinctly from that ofO. vulgatum, the results mentioned above are fundamentally in accordance with the data obtained fromO. vulgatum (Lugardon, 1971). Therefore, the pattern of spore wall morphogenesis appears to be very stable in the genusOphioglossum.     

The Morphology of Protonema and Bud Formation in the Bryales

The development of protonema from spore in aseptic culture wasfollowed in species representing 14 genera and 7 orders of theBryales. In no case could a distinction be made between sharplydefined ‘chloronema’ and ‘caulonema’stages. In all species, with the exception of the anomalous Cinclidotusfontinaloides, the protonema developed a markedly heterotrichoushabit, with prostrate filaments of relatively unlimited growthand erect filaments of more restricted development. The twotypes of filament were usually distinct in cellular characteristicsas well as in the direction of growth. In some cultures a thirdtype of filament grew downwards into the medium. Shoot buds were found to occupy diverse positions in differentspecies, but the commonest position was near the base of a primaryfilament of the erect branch system. Shoot buds were formedas readily in artificial light of sufficient intensity as innatural daylight.     

Spore morphology and wall ultrastructure of Hymenophyllaceae Link (Pteridophyta) from north-west Argentina

The family Hymenophyllaceae is represented in the study area by six species in two genera, Hymenophyllum J. E. Smith and Trichomanes L. The study was based on herbarium material and spores were studied under light microscope (LM), scanning electron microscope (SEM) and transmission electron microscope (TEM). Both genera have trilete spores, 23 to 45 μm in equatorial diameter, with an ornamentation of echinulae and cones in Hymenophyllum and of verrucae, gemmae and granules in Trichomanes. Mature spores have a sporoderm composed of a perispore, an exospore and a fibrillar endospore; the exospore is 0.5 to 2.5 μm thick, compact and with an irregular margin. In some cases radial channels and other channels associated with the middle and inner parts of the laesurae were evident. A series of cavities filled with an opaque content line the inner margin of the exospore. The perispore is 20 to 400 nm thick and unevenly differentiated along the surface of a same spore. Under TEM, two main differentially contrasted portions could be distinguished: a dark massive portion with structural components could not be distinguished, and a light portion with several plates arranged in piles. The inner surface of the perispore exhibit short scales. Globules are immersed within the perispore at some depth from the perispore surface and others connected to it by structural threads. The spore characters observed including shape, ornamentation, laesurae length and wall structure are useful in distinguishing the two genera studied, but less useful in differentiation at the species level.     

ULTRASTRUCTURAL STUDY ON SPORE WALL MORPHOGENESIS IN LYCOPODIUM CLAVATUM (LYCOPODIACEAE)

Spore wall morphogenesis of Lycopodium clavatum was observed by transmission electron microscopy. The spore plasma membrane indicates the reticulate spore sculpture shortly after meiosis. The mature spore wall of this species consists of two layers, inner endospore and outer exospore. There is no perispore in the sporoderm of this species. The exospore formation begins during the tetrad stage; and this layer is divided into two distinct sublayers, an outer lamellar layer and an inner granular layer. The lamellar layer is formed on the sculptured spore plasma membrane. Additional lamellae attach to this layer in a centripetal direction. For that reason, this layer may be derived from spore cytoplasm. The granular layer is formed only in the proximal region following lamellar layer formation, and it also may be derived from spore cytoplasm. The endospore is formed lastly and seems to be derived from spore cytoplasm as well. Accordingly, the spore sculpture of this species may be under the genetic control of the spore nucleus.     

A meiosis-specific protein kinase, Ime2, is required for the correct timing of DNA replication and for spore formation in yeast meiosis

 In this report we study the regulation of premeiotic DNA synthesis in Saccharomyces cerevisiae. DNA replication was monitored by fluorescence-activated cell sorting analysis and by analyzing the pattern of expression of the DNA polymerase α-primase complex. Wild-type cells and cells lacking one of the two principal regulators of meiosis, Ime1 and Ime2, were compared. We show that premeiotic DNA synthesis does not occur in ime1Δ diploids, but does occur in ime2Δ diploids with an 8–9 h delay. At late meiotic times, ime2Δ diploids exhibit an additional round of DNA synthesis. Furthermore, we show that in wild-type cells the B-subunit of DNA polymerase α is phosphorylated during premeiotic DNA synthesis, a phenomenon that has previously been reported for the mitotic cell cycle. Moreover, the catalytic subunit and the B-subunit of DNA polymerase α are specifically degraded during spore formation. Phosphorylation of the B-subunit does not occur in ime1Δ diploids, but does occur in ime2Δ diploids with an 8–9 h delay. In addition, we show that Ime2 is not absolutely required for commitment to meiotic recombination, spindle formation and nuclear division, although it is required for spore formation. Received: 20 February 1996 / Accepted: 7 June 1996     

Influence of edaphic and climatic factors on dynamics of root colonization and spore density of vesicular-arbuscular mycorrhizal fungi in Acacia farnesiana Willd. and A. planifrons W.et.A.

 A study was conducted to assess the dynamics of vesicular-arbuscular mycorrhizal (VAM) fungi associated with Acacia farnesiana and A. planifrons in moderately fertile alkaline soils. The intensity of root colonization by VAM fungi and the distribution of VAM fungal structures varied with host species over a period of time. The occurrence of vesicles with varied morphology in the mycorrhizal roots indicates infection by different VAM fungal species. This was further confirmed from the presence of spores belonging to different VAM fungal species in the rhizosphere soils. Root colonization and spore number ranged from 56% – 72% and 5 – 14 g^{–  1}soil in A. farnesiana and from 60% – 73% and 5 – 15 g^{–  1} soil in A. planifrons. Per cent root colonization and VAM spore number in the rhizosphere soil were inversely related to each other in both the Acacia species. However, patterns of the occurrence of VAM fungal structures were erratic. Spores of Acaulospora foveata, Gigaspora albida, Glomus fasciculatum, G. geosporum and Sclerocystis sinuosa were isolated from the rhizosphere of A. farnesiana whereas A. scrobiculata, G. pustulatum, G. fasciculatum, G. geosporum and G. microcarpum were isolated from that of A. planifrons. The response of VAM status to fluctuating edaphic factors varied with host species. In A. farnesiana though soil nitrogen (N) was positively correlated with root colonization, soil moisture, potassium and air temperature were negatively correlated to both root colonization and spore number. Per cent root colonization and spore number in A. planifrons were negatively related to each other. Further, in A. planifrons as the soil phosphorus and N were negatively correlated with the density of VAM fungal spores, the same edaphic factors along with soil moisture negatively influenced root colonization. Received: 16 May 1995 / Accepted: 7 February 1996     

Spore wall ultrastructure of Polypodiaceae from north-western Argentina

The spore wall ultrastructure of Campyloneurum, Microgramma, Pecluma, Phlebodium, Pleopeltis and Serpocaulum (Polypodiaceae) from north-western Argentina has been studied using transmission electron microscopy (TEM). The exospore is 0.4–3 μm thick, two-layered and variously ornamented in all taxa. The exospore surface is distinctive, but in general ultrastructure the exospore is similar in all species studied. The structural elements of the exospore consist of cavities in the inner part as well as channels with a radial orientation and channels at both sides of the laesura. Variation in the exospore surface was observed in spores at different stages of maturation. The perispore is darkly contrasted and 0.04–2 μm thick. Three different structure types were recognised, including fibrillar, multilamellar and lacunose. Scattered globules and spherules were always present on the perispore surface. The structural variability of the perispore was surveyed within complete sporangia. We concluded that the observed variability may be related to the stage in spore maturation and, consequently, to the stages in perispore differentiation. As the exospore ultrastructure is similar and interpreted as related to functional activity in the studied material, it cannot be used for systematic delimitations at this generic or specific level.     

Spore morphology and ultrastructure of Cyathea (Cyatheaceae,Pteridophyta) species from southern South America

Spore sculpture and wall structure of eight Cyathea (Cyatheaceae) species from southern South America were studied using light microscopy (LM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. Two layers, i.e. an inner and an outer layer, were observed in the perispore. The inner layer has two strata: the inner stratum is attached to the exospore and composed of rodlets tangentially oriented to the spore surface and randomly intermixed; the outer stratum consists of a three-dimensional network of rodlets with either free or fused distal edges forming spinules. The outer layer is thin, darkly contrasted and covers the rodlets. In most cases, the exospore has two layers and a pitted surface. In Cyathea atrovirens, the exospore surface is smooth, while in C. delgadii and C. myriotricha it is verrucate. The homogeneity of perispore features within the genus Cyathea is evident, while exospore features are heterogeneous. The exospore has different kinds of surface-structures that are of potential interest for assessing evolutionary trends within the group.     

梨蒴珠藓孢子萌发与原丝体发育特征研究

为了解梨蒴珠藓（Bartramia pomiformis）孢子萌发和原丝体发育特征,在显微镜下观察室内人工培养的梨蒴珠藓单倍配子体发育过程。结果表明,梨蒴珠藓孢子吸水膨胀5 d后,开始破壁萌发,原丝体系统以丝状绿丝体为主,轴丝体在绿丝体上分化产生。培养22 d后,配子体在轴丝体细胞上分化产生。参照Nishida的标准,梨蒴珠藓孢子萌发类型为真藓型（Bryum-type）。这为梨蒴珠藓的人工扩繁提供了发育学基础资料。     

中华缩叶藓孢子萌发与原丝体发育特征研究

通过室内人工培养中华缩叶藓的孢子,在光学显微镜下详细观察了其孢子萌发、原丝体发育及配子体发生的全过程.结果表明:中华缩叶藓的孢子在壁内萌发,随后分裂产生块状原丝体;块状原丝体上可产生两种丝状体,一种是具疣的棒状原丝体,另一种是由长圆柱状细胞组成的轴丝体;配子体原始细胞只产生于块状原丝体上.根据中华缩叶藓的孢子萌发和原丝体发育特征,并参照Nishida对藓类植物孢子萌发类型的划分,确定中华缩叶藓的萌发孢子型应属于缩叶藓型(Ptychomitrium-type).     

Epiphytism and terrestrialization in tropicalHuperzia (Lycopodiaceae)

A gap in the exospore and the presence of a mesospore is found to be a normal part of development in the ten species ofSelaginella we have studied. The early spore wall consists of an exospore and a mesospore forming successively on the plasma membrane of the megaspore protoplast when it is 10–15 µm in diameter. Enlargement of the exospore and mesospore creates a central space, the lumen of the megaspore, around the megaspore protoplast. After that there is a vast enlargement of the exospore and a relatively small enlargement of the mesospore. The exospore splits close to its contact with the mesospore forming a gap over equatorial and distal regions. The gap becomes greatly expanded and becomes filled with lipids, PAS-positive carbohydrates, proteins and is crossed by wicks. Experiments with solutions of different osmolality on fresh megaspores show that the exospore and mesospore are not osmotic barriers. The mesospore appears not to be resistant to acetolysis at the many stages tested but exospore is resistant. Thus the mesospore size and shape is retained by the inner exospore that enveloped the mesospore. At maturation the mesospore undergoes lysis and absorption. At the beginning of germination stages an endospore forms at the inner part of the exospore. This inner part of the exospore, that adhered to and enveloped the mesospore, becomes pressed near to the bulk of the exospore. Until pregermination stages the megaspore protoplast is small (10–20 µm in diameter).     

碎米藓属两种藓类植物孢子萌发与原丝体发育特征研究

为获取其孢子萌发类型与该属植物系统发育、生态选择以及生殖策略选择的相关性,该研究通过室内人工培养的方式,在微米量级下观察并描述了碎米藓属(Fabronia)碎米藓(F.pusilla)和东亚碎米藓(F.matsumurae)两种藓类植物孢子萌发、原丝体发育和配子体发生的过程.结果表明:(1)两种藓类植物孢子均为壁外萌发...     

THE EFFECT OF METHANOL ON SPORE GERMINATION AND RHIZOID DIFFERENTIATION IN ONOCLEA SENSIBILIS

In germinating spores of Onoclea sensibilis, the nucleus migrates to one end prior to an asymmetric cell division that partitions each spore into two daughter cells of unequal size. The larger cell develops into a protonema, whereas the smaller cell immediately differentiates into a rhizoid. When spores were germinated in the presence of methanol, nuclear migration was inhibited and most nuclei moved only to the raphe on the proximal side of the spores. Subsequent cell division partitioned each spore into daughter cells of equal size of which both developed into a protonema and neither into a rhizoid. Spores became sensitive to methanol at a time just prior to or coincident with nuclear migration and the effects of the alcohol were rapidly reversible as long as the spores were removed from methanol prior to the completion of cell division. Exposure to methanol prior to, but not during, nuclear migration or after mitosis had no effect upon rhizoid differentiation. The alcohol disrupted the formation of crosswalls after mitosis and they were often convoluted and irregularly branched. These results are consistent with the interpretation that methanol may disrupt a membrane site that plays an essential role in nuclear movement and rhizoid differentiation.     

Immunoblot Analysis of Exospore Polypeptides from Some Entomophilic Microsporidia12

ABSTRACT. Immunological relationships between genera and species of microsporidia were examined by immunoblot analysis. Exospore polypeptides from two Nosema spp., three Vairimorpha spp., and two undescribed Vairimorpha-like isolates were analyzed. Gel electrophoresis and immunoblot analysis revealed that a variety of polypeptides, mostly between 15,000 and 90,000 molecular weight, are present on the exospore. The three Vairimorpha spp. are closely related immunologically to each other, but less so to the two undescribed Vairimorpha-like isolates. The two Nosema spp. are immunologically distant from each other and from the Vairimorpha spp. Indirect evidence, however, indicated that many internal spore polypeptides present in both genera are similar. Cross-reactivity between exospore polypeptides from entomophilic microsporidia and antisera to a mammalian microsporidium, Encephalitozoon cuniculi, was very limited. These results indicate that immunoblot analysis of exospore polypeptides may be employed to investigate the interrelatedness of microsporidian species, and that exospore polypeptides of some microsporidia are sufficiently diverse to be of immunodiagnostic value.     

Phenology of 16 species of ferns in a subtropical forest of northeastern Taiwan

A knowledge of fern phenology promotes understanding of the biology and ecology of ferns. In this study, the phenology of 16 fern species in a subtropical broadleaf forest (N24°46′, E121°34′) in northeastern Taiwan was monitored from August 1997 to August 2001. Every fern produced both fertile and sterile leaves in each year of the study. Most fertile leaves emerged in February and March, whereas most sterile leaves emerged from May to September. Most leaves reached full expansion during April–July and died during April–August. The average life span of leaves ranged from 4.4 months to 30.3 months. In seven species, fertile leaves lived longer than sterile leaves, but this difference was significant only in Pteris wallichiana. In the other nine species, sterile leaves lived longer than fertile leaves, but the difference was significant only in Cyathea spinulosa, Plagiogyria dunnii, and Plagiogyria adanata. The ephemeral fertile leaves of the two dimorphic species died soon after releasing their spores, at only 5 months of age. However, their sterile leaves survived for over 22 months. The fertile leaves of the other 14 species remained green for almost 2 years after releasing their spores. Sterile leaves remained sterile throughout their lives. Spores matured in May–July and were released in June–August. After spore release, the sporangia detached. No leaf produced a second cohort of sori. Several phenological events, including sterile leaf emergence, leaf expansion and senescence, and spore maturation and release, were significantly positively correlated with temperature but not with precipitation, whereas the emergence of fertile leaves was weakly negatively correlated with temperature and precipitation. However, those correlations varied among different species. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.