Mature Sporangium Research Articles

Impacts of heavy metal and nutrient accumulation on the vegetative, anatomical and reproductive characteristics and phytoremediation efficiency of Azolla Filiculoides L .

abstract: Aquatic ecosystems are susceptible to contamination from various sources, including agricultural wastewater, urban sewage and industrial activities. This study investigated the phytoremediation potential of the aquatic fern Azolla filiculoides L. in removing heavy metals and nutrients from the Anzali lagoon, in the Caspian Sea. Water and plant samples were collected from diverse areas within the lagoon. The bioconcentration factor for potassium and lead surpassed one, indicating significant root absorption. Conversely, for manganese and zinc, the values were below one, suggesting restricted absorption by the roots. However, the biotranslocation factor exceeded one for all elements, with phosphorus and zinc exhibiting the highest values. This indicates that the plants effectively transferred heavy metals and nutrients to the shoots. A. filiculoides growing in contaminated areas had smaller epidermal cell dimensions, a thicker stem cortex, and thicker tracheid and sieve cells in the roots compared to those in uncontaminated areas. In contaminated areas, mature sporangium capsules opened rapidly, accelerating the maturation and germination of spores, thereby enhancing the survival capacity of A. filiculoides . The study demonstrates Azolla filiculoides 's effectiveness as a phytoremediator in the Anzali lagoon, highlighting its potential for sustainable and eco-friendly bioremediation of heavy metal-contaminated areas through ongoing research and technological progress.

Involvement of BldC in the Formation of Physiologically Mature Sporangium in Actinoplanes missouriensis.

AmBldD is a global transcriptional regulator that represses the transcription of several genes required for sporangium formation in Actinoplanes missouriensis. Here, we characterized one of the AmBldD regulons: AMIS_1980, encoding an ortholog of BldC, which is a transcriptional regulator involved in the morphological development of Streptomyces. We determined the transcriptional start point of the bldC ortholog by high-resolution S1 nuclease mapping and found an AmBldD box in its 5'-untranslated region. Reverse transcription-quantitative PCR analysis revealed that the transcription of bldC is activated during sporangium formation. A bldC null mutant (ΔbldC) strain formed normally shaped sporangia, but they exhibited defective sporangium dehiscence; under a dehiscence-inducing condition, the number of spores released from the sporangia of the ΔbldC strain was 2 orders of magnitude lower than that from the sporangia of the wild-type strain. RNA sequencing analysis indicated that BldC functions as a transcriptional activator of several developmental genes, including tcrA, which encodes a key transcriptional activator that regulates sporangium formation, sporangium dehiscence, and spore dormancy. Using electrophoretic mobility shift assay (EMSA), we showed that a recombinant BldC protein directly binds to upstream regions of at least 18 genes, the transcription of which is downregulated in the ΔbldC strain. Furthermore, using DNase I footprinting and EMSA, we demonstrated that BldC binds to the direct repeat sequences containing an AT-rich motif. Thus, BldC is a global regulator that activates the transcription of several genes, some of which are likely to be required for sporangium dehiscence. IMPORTANCE BldC is a global transcriptional regulator that acts as a "brake" in the morphological differentiation of Streptomyces. BldC-like proteins are widely distributed throughout eubacteria, but their orthologs have not been studied outside streptomycetes. Here, we revealed that the BldC ortholog in Actinoplanes missouriensis is essential for sporangium dehiscence and that its regulon is different from the BldC regulon in Streptomyces venezuelae, suggesting that BldC has evolved to play different roles in morphological differentiation between the two genera of filamentous actinomycetes.

New Perkinsea Parasitoids of Dinoflagellates Distantly Related to Parviluciferaceae Members.

Perkinsea is a phylogenetic group of protists that includes parasites of distantly related hosts. However, its diversity is still mainly composed of environmental sequences, mostly obtained from freshwater environments. Efforts to isolate and culture parasitoids of dinoflagellates have led to the description of several phylogenetically closely related species constituting the Parviluciferaceae family. In this study, two new parasitoid species infecting dinoflagellates during recurrent coastal blooms are reported. Using the ribosomal RNA (rRNA) gene phylogenies, we show that both cluster within Perkinsea, one of them at the base of Parviluciferaceae and the other in a distinct branch unrelated to other described species. The establishment of host-parasite lab cultures of the latter allowed its morphological characterization, resulting in the formal description of Maranthos nigrum gen. nov., sp. nov. The life-cycle development of the two parasitoids is generally the same as that of other members of the Parviluciferaceae family but they differ in the features of the trophont and sporont stages, including the arrangement of zoospores during the mature sporangium stage and the lack of specialized structures that release the zoospores into the environment. Laboratory cross-infection experiments showed that the parasitoid host range is restricted to dinoflagellates, although it extends across several different genera. The maximum prevalence reached in the tested host populations was lower than in other Parviluciferaceae members. The findings from this study suggest that Perkinsea representatives infecting dinoflagellates are more widespread than previously thought.

Parasite-mediated increase in prey edibility in the predator-prey interaction of marine planktonic protists

In planktonic predator-prey interactions, predation pressure could be affected by several factors associated with prey, including cell size, shape, nutritional quality, presence of chemical deterrents, and movement behaviors. In addition, parasitism may also play an important role in predator-prey interaction by infecting one or both partners involved in the biological interaction. In this study, parasite mediation in predator-prey interactions of planktonic protists was addressed using model organisms commonly observed in temperate coastal environments, namely, a phototrophic dinoflagellate Akashiwo sanguinea as a potential host and prey, a heterotrophic dinoflagellate predator Luciella masanensis, and a dinoflagellates-infecting parasitoid Parvilucifera infectans. Parasite mediation permitted L. masanensis to exploit the prey A. sanguinea that the predator was otherwise unable to use or did not prefer. However, parasite-mediated exploitation seems to be dependent on the infection cycle of P. infectans. Although zoospores and mature sporangium produced from infected A. sanguinea were not ingested by the predator L. masanensis, both newly infected (i.e., cells that zoospores had just penetrated) and infected (those containing early to late trophocytes) A. sanguinea cells attracted numerous L. masanensis cells and were rapidly ingested by the predator, leading to the predator's positive growth. The results from mixed culture experiments of the three protists showed that the presence of P. infectans at low density led to co-occurrence of the three protists. Thus, the parasitoid seems to play the role of a mediator in either inedible prey- or predator-dominated environments, leading to co-occurrence of the three protists.

Occurrence of stem blight and fruit rot caused by Phytophthora capsici on Chinese cucumber (Trichosanthes kirilowii) in China.

Chinese cucumber, Trichosanthes kirilowii Maxim, is a perennial liana plant belonging to the Cucurbitaceae family and is an important traditional medicine in Chinese herbalism. The root, fruit and seed possess the medicinal value, and also the seeds are edible (Zhang et al. 2019). With increasing demand, the wild resource was domesticated and has been planted in China. Diseases of T. kirilowii have become more prominent with the expansion of cultivated area and have caused the yield reduction (Zhang et al. 2014). The general disease field has caused a yield reduction of 10% -30%, even up to 80% seriously. Since 2017, fields in Luan city, Anhui province exhibited 10 to 30% of plants with stem blight and fruit rot. The two-week seedlings were infected at the basal part of stem and showed water-soaking, then damping off. In older plants, it is common to see stem blight with brown-to-black lesions, stunted growth, and most diseased plants eventual death. On rot fruit, the symptom of water soaked lesions was firstly observed, and then with white mold, eventual rot. More than 60 samples of symptomatic stems or fruit were collected from Luan and Hefei, Anhui province during April to October 2017. The symptomatic tissues were washed, disinfested with 0.5% sodium hypochlorite for 30 s, rinsed twice in sterile water for 1 min, dried and incubated on V8-juice amended with 50μg ml-1 of ampicillin and rifampicin at 25°C. Based on morphological characteristics, more than 80% of the total 98 isolates generated were similar on the level of morphology, and preliminarily identified as Phytophthora species (Erwin and Ribeiro 1996). Three isolates were selected randomly to further observe and identify up to species level. The isolates produced abundant, aerial, white mycelia on V8 agar plates. Sporangia were produced on sporangiophores in 10% V8 liquid culture medium after 4 days at 25°C, mainly obovoid with one papilla, 38.8 to 50.4 μm× 22.8 to 33.5 μm in size. The single mature sporangium immersed in water quickly released 20 to 40 biflagellate motile zoospores. The isolates were further confirmed by amplification and sequencing of two conserved markers, the internal transcribed spacer (ITS) region and cytochrome c oxidase subunit I (COI) region with primers ITS1/ITS4 (White et al. 1990) and OomCoxILevup/Fm85mod (Robideau et al. 2011), respectively. The GenBank Accession Nos. were MN368092, and MN369544 for ITS and COI, respectively. The BLAST search results showed 100% similarity with ITS sequences (KF700090, KC438376) and COI sequences (MH136864, AY129166) of Phytophthora capsici isolates in Genbank. Koch's postulates were performed by testing the pathogenicity of the sequenced isolate on the Chinese cucumber (cv. 'Wanlou9'). On 1-month-old plants, a flap of bark was cut with a sterile scalpel, and the 2×2 cm plug of 5-day-old mycelium was inserted. The flap was then closed and sealed with Parafilm. The agar plug was treated in the same manner as the inoculated plants as the controls. And also, the intact fruit (one month old) was inoculated with 10 μL of zoospore suspension (2 × 105 zoospore/ml) and kept in growth chamber at 25 °C, with 80% relative humidity, and the control was treated with 10 μL of sterile distilled water. Three days after inoculation, the stems and the fruit inoculated with mycelium and zoospores showed water-soaked lesions. After 10 days, the symptoms on the tissues resembled those observed in the field. No symptoms were detected on the controls. P. capsici was reisolated from the diseased tissues but not from the control. This combination of data confirmed that the pathogen was P. capsici. To our knowledge, this is the first report of P. capsici causing stem blight and fruit rot on Chinese cucumber in China.

Predatory protists.

The vast majority of eukaryotic life is made up of single cells commonly referred to as protists. In this primer, Leander provides an introduction to predatory protists - cells that eat other cells. This lifestyle, in particular the use of phagocytosis, makes endosymbiosis possible and enabled the evolution of complex cells.

Phenotypic identification of indigenous fungi and lactic acid bacteria isolated from ’gatot’ an Indonesian fermented food

Astriani A, Diniyah N, Jayus J, Nurhayati N. 2018. Phenotypic identification of indigenous fungi and lactic acid bacteria isolated from ’gatot’ an Indonesian fermented food. Biodiversitas 19: 947-954. As a traditional Indonesian food made from cassava, ‘gatot' has special attracted characters of black appearance and chewy texture, mainly as a result of certain fungi and lactic acid bacteria (LAB) during the spontaneous fermentation. However, many producers were failed to gain these typical properties since much unwanted microbial strain often appears during the spontaneous fermentation. Therefore, this study was conducted to isolate and identify the indigenous fungi and LAB which predominantly contributed in fermentation of cassava during ‘gatot’ production. Fungi and LAB were isolated from conventionally made of the ‘gatot’ followed by the phenotypic identification of the isolates based on the morphological and physiological properties. The fungi isolates were morphologically distinguished by the type of mycelia, the shape, and color of the sporangium, while the LAB strains were identified by the type of cell and colony form. In addition, the physiological behavior of the LAB isolates was characterized by their typical growth temperature, its catalase activity and its fermentation profile using BBL crystal kit test. The predominant fungi isolates were identified as Botryodiplodia theobromae, Rhizopus oligosporus, Trichoderma sp. and Aspergillus niger. B. theobromae had greyish white to black color of mycelia when it mature. R. oligosporus had globose sporangium and blackish grey color of the mature mycelia. Trichoderma sp. had green color of the mature sporangium and mycelia. A. niger had yellow color of the mycelia and black color of sporangium. Meanwhile, the indigenous LAB was majority identified as Lactobacillus manihotivorans, Bacillus licheniformis, Brevibacillus brevis and Lactobacillus fermentum. Those bacteria were gram-positive, rods shape, catalase-negative and grew optimally at 37oC. The LAB also arise frequently in many spontaneously fermented food. B. theobromae, R. oligosporus, L. manihotivorans, and L. fermentum were potential and non-pathogenic microbial, which can be used as a starter culture to produce ‘gatot’ under controlled fermentation process.

极小种群野生植物对开蕨种群结构特征和群落物种多样性

PDF HTML阅读 XML下载 导出引用 引用提醒 极小种群野生植物对开蕨种群结构特征和群落物种多样性 DOI: 10.5846/stxb201704190706 作者: 作者单位: 长白山科学研究院,长白山科学研究院,吉林省长白山保护开发区管理委员会,长白山科学研究院,长白山科学研究院,长白山科学研究院,吉林省抚松县林业局,吉林省抚松县林业局 作者简介: 通讯作者: 中图分类号: 基金项目: 国家"十二五"农村领域国家科技计划项目（2012BAD22B0401） Characteristics of population structure and community species diversity of an extremely small population of protected Phyllitis scolopendrium Author: Affiliation: Academy of Science of Changbai Mountian,Academy of Science of Changbai Mountian,Changbai Mountain Protection and Development Management Committee of Jilin Province,Academy of Science of Changbai Mountian,Academy of Science of Changbai Mountian,Academy of Science of Changbai Mountian,FuSong County Forestry Bureau of Jilin Province,FuSong County Forestry Bureau of Jilin Province Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:以国家Ⅱ级保护极小种群野生植物——对开蕨（Phyllitis scolopendrium）为研究对象，分析了在海拔729、1008m群落内，其种群大小、分布频度和密度，个体形态特征指标及其在种群内、种群间差异，苗高分布规律、相对苗高组替代年龄级结构，分布格局和群落各层次的物种多样性，群落的相似性。结果表明：对开蕨在自然分布区内为偶见种，呈斑块状分布。在400m2内，海拔1008m处（01群落）种群密度为31株，样地分布频度为43.75%，最大密度15株/25m2；海拔729m处（02群落）种群密度为91株，样地分布频度为93.75%，最大密度30株/25m2。通过对其自然苗高，叶片数量，有孢子囊叶片数量，最大叶片长、宽值，最小叶片长、宽值，冠径，叶片厚度7个形态指标的分析显示，种群内变异较大，随着植株高度（年龄）的增加，其变异系数均随之减小而趋于稳定；种群间在自然苗高，最大叶片长度和宽度，成熟孢子叶片数量，冠径，叶片厚度上达到极显著差异（P < 0.01）。其苗高分布呈现双峰型，01种群波谷出现在15.1-20.0cm处；02种群波谷出现在10.1-15.0cm处，两群落均显示有一次较大的更新过程，同时01种群在40.1-45.0cm出现间断。年龄级分析得出，01种群划分为5个龄级，近于正态分布；02种群划分为4个龄级，为倒J型分布；两种群分别处于中龄期和幼龄期，没有出现衰退型年龄结构。格局分析得出，对开蕨种群均为聚集分布。两群落的乔木、灌木、草本层的Shannon-Wiener指数、Pielou均匀度指数、Marglef丰富度指数、生态优势度和种间相遇机率较低（与地带顶级植被相比）而且分布不均；对开蕨在两群落的草本层中重要值较低，仅为伴生种。两群落相似性分析显示，乔木、灌木、草本层的相似度指数分别为66.67%、69.23%和38.46%，草本层差异较大。 Abstract:For Phyllitis scolopendrium, a second-class national protected wild plant with extremely small populations, which is distributed in a narrow region of the Changbai Mountains, we analyzed the population size, distribution frequency and density, individual features, and the variation of internal and external populations at 729 and 1008m above sea level (asl). The plant height, substitute age structure, distribution pattern, community biodiversity, and similarity of various layers were also described. Results showed that P. scolopendrium was a typical occasional species, which showed a patchy distribution pattern. At 729m asl, the population density was the highest (91 per 400m2), with a distribution frequency of 93.75% and highest density of 30/25m2. At 1008m asl, the population density was only 31 per 400m2, with a distribution frequency of 43.75% and highest density of 15/25m2. Based on the analyses of morphological features, including plant height, leaf number, sporangium leaf number, maximum leaf length and width, minimum leaf length and width, canopy width, and leaf thickness, we found that the morphological features of the internal population showed the highest variation, indicating a decreasing trend with increasing height/age. Additionally, variations in plant height, mature sporangium leaf number, maximum leaf length and width, canopy width, and leaf thickness all showed significant differences (P < 0.01), indicating that the two populations were from different species types. Plant height showed a double peak pattern. Trough value of type 01 population occurred at 15.1-20.0cm, whereas the trough value of the type 02 population occurred at 10.1-15.0cm. There was a significant update process in both types, and a break of the type 01 population at 40.1-45.0cm. We analyzed the age structure of type 01 and 02 populations and found that there were five age classes of the type 01 population, which showed a normal distribution pattern, whereas the type 02 population had four age classes, which showed an inverted J distribution pattern. Type 01 and 02 populations were at juvenile and middle age stages, with no trend of senescence. Based on the spatial pattern analysis, we found that P. scolopendrium showed a negative binomial distribution pattern. The diversity indices, including Shannon-Wiener, Pielou, and Margalef, showed that the similarity index of tree, shrub, and herb layers in the two types was low, indicating a low biodiversity status compared with the local climax community. Phyllitis scolopendrium was considered a companion species because of lower importance value in type 01 and 02 communities. Similarity analyses showed that plants in tree and shrub layers were the most similar, followed by the herb layer with values of 66.67%, 69.23%, and 38.46% respectively, indicating that the herb layer had the most variation. 参考文献 相似文献 引证文献

Black gill disease of Pacific white leg shrimp (Litopenaeus vannamei) by Aspergillus flavus

Objective: To study the epidemiology of black gill disease in white leg shrimp which is a major problem being faced by the commercial shrimp farmers who are culturing Litopenaeus vannamei (L. vannamei) in India. Methods: The normal and infected shrimps were collected from shrimp pond and the gill was preserved in appropriate preservative for histopathological examination and scanning electron microscope analysis. Pathogenic fungus was isolated from black gill of L. vannamei in potato dextrose agar medium. Morphological study and fungal strain identification were done by using light microscopy and scanning electron microscope. Fungal DNA was amplified by ITS4 and ITS5 primers and gene sequencing was done by Macrogen Inc., Korea. Phylogenetic tree was prepared by using MEGA 6 software. Results: Fungal spores and hyphae were observed both in internal and external gill surface of infected shrimps. Fungal spores were round in shape and mature sporangium was observed. The histopathology study showed clearly that infected gill was damaged by the fungi. Scanning electron microscopic study showed adherence of fungi in infected gill. Internal transcribed spacer gene sequencing revealed that it was caused by Aspergillus flavus. Conclusions: The outcome of the present study would help to know the cause of black gill disease and to understand the effect of pathogenic fungi in shrimp culture. This study will initiate researchers for work in field of treatment or prevention of black gill disease in commercial L. vannamei culture.

Ontogeny of the Sporangia of Sphaeropteris cooperi

Ontogeny of the Sporangia of Sphaeropteris cooperi

Immunolocalization of an endogenous antigenic material of Rhinosporidium seeberi expressed only during mature sporangial development

We investigated the immunolocalization of Rhinosporidium seeberi's antigens using sera from individuals infected with R. seeberi and tissue from Sri Lankan patients with rhinosporidiosis. The tissues were fixed in LR white resin, thin sectioned, fixed onto nickel grids and evaluated by transmission electron microscopy for the presence of R. seeberi's sporangia. The tissue samples were reacted with the patients's sera and then labeled with protein A colloidal gold (PACG) for immunolocalization. It was found that the PACG had fixed to antibodies that specifically recognized an internal electron lucent layer situated immediately under the mature sporangium's wall. Strikingly, the endospores, the juvenile and intermediate sporangia did not undergo PACG labeling. This study found that the expression of this antigen occurs only in the final developmental stages of R. seeberi's mature sporangia. Our data may explain why circulating antibodies to R. Seeberi were not detected before in studies that used endospores as antigen in immunoassays. This is the first report in which an antigenic material with a potential role in the immunology of rhinosporidiosis has been detected.

Immunolocalization of an endogenous antigenic material of Rhinosporidium seeberi expressed only during mature sporangial development.

We investigated the immunolocalization of Rhinosporidium seeberi's antigens using sera from individuals infected with R. seeberi and tissue from Sri Lankan patients with rhinosporidiosis. The tissues were fixed in LR white resin, thin sectioned fixed onto nickel grids and evaluated by transmission electron microscopy for the presence of R. seeberi's sporangia. The tissue samples were reacted with the patients's sera and then labeled with protein A colloidal gold (PACG) for immunolocalization. It was found that the PACG had fixed to antibodies that specifically recognized an internal electron lucent layer situated immediately under the mature sporangium's wall. Strikingly, the endospores, the juvenile and intermediate sporangia did not undergo PACG labeling. This study found that the expression of this antigen occurs only in the final developmental stages of R. seeberi's mature sporangia. Our data may explain why circulating antibodies to R. Seeberi were not detected before in studies that used endospores as antigen in immunoassays. This is the first report in which an antigenic material with a potential role in the immunology of rhinosporidiosis has been detected.

Cell wall permeability and its relationship to spore release in Achlya intricata

Dynamically, the process of sporangial emptying in the zoosporic fungus Achlya intricata best fits a model based on the regulated dissipation of an osmotically generated pressure potential. Two testable predictions, derived from this hypothetical discharge mechanism, are (a) that the sporangial cell wall must be capable of maintaining a concentration gradient of some solute to depress the luminal osmotic potential, since the mature sporangium lacks a plasmalemma; and (b) that the emptying process should be inhibited by water stress. The permeability of the sporangial wall was estimated by monitoring the uptake of polyethylene glycol (PEG) molecules of different molecular weights. An aqueous solution of PEG-2000 contained molecules of the critical hydrodynamic volume, corresponding to a maximum pore size of ∼2.0 nm in the sporangial wall. Complete control (and inhibition above a critical solute concentration) over the emptying process was gained using polymers with M r 's in excess of 2000. The pressure potential within the sporangium was estimated, during discharge, to be ∼ + 10 −3 MPa. This value of pressure potential is consistent with that predicted from a mathematical model previously published.

Dynamics of sporangial emptying in Achlya intricata

The dynamics of sporangial emptying in the zoosporic fungus Achlya intricata were characterized by analysis of photographic and video records of spore release. The mature sporangium is a semirigid cell wall enclosing loosely packed unicellular spores. There is a highly significant linear relationship between sporangial volume and the number of spores produced. During discharge, the spores exit the sporangium in a pulse-like fashion, the motion of the sporangial contents being punctuated by the passage of each successive spore through the constricting papilla. The plot of the number of spores released against time (“emptying profile”) is a rectangular hyperbola indicating that the velocity of spore release decreases during the emptying process. However, each individual spore accelerates during its passage through the sporangial lumen. Spore velocity shows a strong temperature dependence and is higher in larger sporangia than in smaller ones. Puncture at any point along the surface of the mature sporangium results in the release of spores through the artificial opening. Dynamically, sporangial emptying in A. intricata shares many features in common with Phytophthora cactorum and best fits a model based on the regulated dissipation of an osmotically generated pressure potential. This hypothesis is supported by mathematical modeling and the results of previous experiments.

Cell wall architecture of sporangia, chlamydospores, oogonia, and oospores in Phytophthora

The ultrastructure of the walls of sporangia, chlamydospores, oogonia, and oospores of Phytophthora was analyzed with thin sectioning, replica, and freeze-fracturing techniques. All walls produced by this fungus are built from two basic types of layers: A layers, which are amorphous throughout, and FA layers, in which a fibrillar network is embedded in an amorphous matrix. With the exception of the cyst wall, which consists entirely of an FA layer, all walls are composed of at least one A and one FA layer. The combination of thickness, type, and number of layers is different for each wall type, but there is a remarkable similarity between walls of chlamydospores and oogonia. The fibrillar elements in the sporangial wall are composed of cellulose, and indirect evidence suggests that this might be true for all wall types of Phytophthora. The primary sporangial wall is stretched during the expansion phase, leading to rupture of its external A layer and reorientation of the fibrils in the inner FA layer. As a result the surface of the mature sporangium bears characteristic patches of amorphous A-layer material from which the underlying microfibrils emanate in a stellate pattern.

A Light and Electron Microscopic Study of Stalk Formation in the MyxomyceteArcyria Cinerea

Stalk formation in Arcyria cinerea has been examined using both light and electron microscopy. The stalk of a mature sporangium consists of an outer wall or stalk tube which is filled with sporelik...

Ruptur der Kapselwand beiSphagnum

Two layers of modified cells of the “Wassergewebe” turn the border area of operculum and urn into a rigid zone of resistance. This maintains its diameter, even though the rest of the capsule wall starts to shrivel up once evaporation deprives the mature sporangium of most of its water content. The reinforced capsule area stands out progressively over the collapsing tissue on either side as shrinkage proceeds. Thanks to the presence of this rigid band of capsule wall tissue, the shape of the sporangium gradually changes from a sphere to a cylinder whose perfectly shaped distal mantle edge, naturally, coincides with the zone of resistance. This is where the capsule wall breaks, because the specific type of deformation makes this edge the site of maximum stress. The ensuing rent separates entire cells within the epidermis, while the adjoining layers of subepidermal cells are torn, leaving only a single wall intact, i.e. the inner periclinal wall of the second, innermost layer. The final rupture of this wall, which is still poorly understood as a mechanism, then triggers off the “explosion” of the capsule.

Growth and ultrastructural differentiation of sporangia in Phytophthora palmivora.

Development of sporangia in Phytophthora palmivora Butler consists of two main stages. The first involves expansion of the sporangial initial to about the size of the mature sporangium, whereas the second is characterized by the differentiation of the expanded vesicle to the mature sporangium. Differentiation includes basal plug formation, secondary sporangial wall thickening, and apical papilla formation.Expansion of the sporangial initial appears to be mainly the result of cytoplasmic inflow from the mycelial mat coupled with surface growth of the vesicle wall. Basal plug formation terminates the phase of expansion. The process of plug formation involves deposition of wall-like material at the base of the expanded vesicle. The depositions, which grow from the periphery towards the center of the sporangiophore, are at first rather irregular in shape but eventually lead to complete occlusion, thus separating the immature sporangium from the sporangiophore. Sporangial wall thickening starts at the basal plug and progresses towards the developing apical papilla. Papilla formation is initiated by an apical bulge of the immature sporangium. The cytoplasm within the bulge is specialized and characterized mainly by populations of small (50–100 nm) and large (about 250 nm) vesicles, which appear to be involved in papilla formation. Papilla deposition resembles hyphal tip growth in the absence of cell expansion.

The Characterization of Hyalochlorella marina gen. et sp.nov. a New Colourless Counterpart of Chlorella

SUMMARY: Hyalochlorella marina is described as the type species of a new colourless genus of the chlorococcalean algae. It is a morphological and developmental counterpart of Chlorella and analogous to Prototheca, the known colourless counterpart. Hyalochlorella is distinguishable from Prototheca by its mode of autospore discharge, its possession of a large centric or eccentric vacuole, a Ruthenium Red positive wall and its lack of pectinaceous interstitial ground substance in the mature sporangium. Its developmental cycle is simple, involving a period of growth followed by cytokinesis. Nuclear division occurs concomitantly with growth; cytokinesis involves the segmentation of a multinucleate protoplast into uninucleate daughter protoplasts (preautospores) by simultaneous multiple fission. Daughter cell number, although variable, is usually an integral of 2 n or 2 n - 2 n-2 . Numbers in the 2 n – 2 n - 2 series are believed to result from the degeneration of one nucleus in the tetranucleate stage followed by subsequent growth and division.

The Spore Pattern in some Species of Cheilanthes

A B S T R A C T Of the 32 taxa examined, 13 contained 32 spores in each sporangium and are considered apogamous, 14 were sexual species with 64 spores per sporangium, and 5 had 32 spores in some sporangia and 64 in others. When considered as a whole, the spores ranged in size from 29.9 to 74.88,u. Most species had oval or globose spores but several had tetrahedral spores. The spores of all were radially symmetrical. Almost all of the species possessed a crassimarginate type of laesura and all except C. cooperae and C. viscida had a perispore. The ornamentation of the perispore showed the following patterns: napate, granulate, psilate, lobate, foveate, and echinate. The exine pattern was predominantly psilate but foveate, rugulate, napate, and granulate conditions were observed. Seventeen taxa were found to have some degree of spore abortion. THP, GENUS Cheilanthes contains a large number of species and its relationship to other genera of the cheilanthoid ferns is not at all clear. It was felt that a study of the spore morphology of the North American species would be helpful in the clarification of its status as a genus and in its relationship to related genera. The only previously published papers dealing with spores in the genus Cheilanthes are those of Weaver (1896), McVaugh (1935), Harris (1955), Sladkov (1959, 1962), Nayar (1962, 1963), Tschudy and Tschudy (1965), Whittier (1965), and Hitt and Knobloch (1967). METHODS AND MATERIALS-Sixty-five collections among 32 species are considered in the text. Live plants from various sources were used in all cases. The spore number was obtained by placing a single, mature sporangium in a drop of Hoyer's