Cymbellonitzschia diluviana Hustedt (Bacillariophyceae): Habitat and auxosporulation

The diatom Cymbellonitzschia diluviana Hustedt is an important indicator species in interglacial deposits but is rarely reported from contemporary sites. The presence of large populations in Lough Neagh, N. Ireland, made possible a study of its ecology and auxosporulation. The apical length of cells in the lake was usually between 7 and 25 µm, but in culture there was a broader range between 5 and 42 µm. Amongst smaller cells (< 11 µm), some (3 %) were found with raphes on the dorsal (i.e. convex side) rather than usual ventral side. At cell division, both daughter cells had hantzschioid symmetry. C. diluviana is found in alkaline waters (pH 7.6–9.0) but not usually where there is significant calcite deposition. Its present rarity is probably because its preferred habitat is now less common. In L. Neagh, C. diluviana was found on exposed rocky and sandy shores, but was particularly abundant in shifting sand bars. This highly abrasive and erosive environment requires cells to have good adhesion and the ability to withstand extended periods of burial. C. diluviana is essentially a ruderal species, adapted to habitats with high disturbance.     

Morphological variability of the diatom Cyclotella atomus Hustedt var. atomus and C. atomus var. gracilis var. nov.

Cyclotella atomus collected from different rivers, reservoirs and lakes shows considerable morphological variability. On the basis of electronmicroscopic (EM) study, we propose Cyclotella atomus var. gracilis Genkal et Kiss as a new variety of this species. Cyclotella atomus var. atomus has short and long radial striae, which are irregularly arranged on the same valve, and the alveolar chambers are not clearly divided from the central, hyaline part of the valve face. In addition to the described basic form, several specimens with other features have also been found and are thought to belong to an undescribed variety. The striae of the new variety are equal in length, and the alveolar chambers are clearly divided from the hyaline central area of the valve face by a curved structure.There are EM micrographs on Cyclotella atomus var. gracilis under different names in different papers. The new variety has several characteristics also found in other species, e.g. Cyclotella caspia Grun., or C. meneghiniana Kütz.     

硅藻中国一新记录种——泉生平片藻

利用光学显微镜和扫描电子显微镜对采自湖南省绥宁县巫水水域的硅藻标本进行了观察研究,鉴定出其中一种为硅藻中国新记录种——泉生平片藻［Tabularia fonticola (Hustedt) C.E. Wetzel & D.M. Williams］,该种具有以下鉴别特征：(1) 壳面轮廓为线形披针形,中央胸骨宽,线纹短且宽。(2) 横主肋和纵细肋硅质化增厚。(3) 孔纹开口被数条横向硅质条组成的筛板所遮拦。(4) 每个壳面仅在其一端着生一个唇形突。(5) 壳套顶孔区孔纹有序排列。(6) 第一环带开放。该研究首次报道了泉生平片藻的前正常营养期细胞的超微结构特征,研究结果不仅增加了对泉生平片藻的超微结构认识,而且扩展了其地理分布区域。     

Heterotrophic nutrition of the marine pennate diatom Navicula pavillardi Hustedt.

Navicula pavillardi Hustedt, a marine, littoral, pennate diatom, can grow in the dark on glutamate or on the complex organic supplements tryptone or yeast extract. Growth on glutamate in the dark took place without an initial lag phase, whereas growth on tryptone began only after a 2-day lag phase that could be abolished by the simultaneous presence of glucose. Lactate inhibited growth in the dark on glutamate, but not photoautotrophic growth. Relatively low concentrations of glutamine inhibited photoautotrophic growth. The observed doubling time for heterotrophic growth on glutamate or tryptone was about 70 h, compared with a doubling time of 24 h under optimal photoautotrophic conditions. Glucose did not decrease the doubling time in the dark on tryptone. The assimilation efficiency for glutamate was 41%. The estimated necessary uptake rate for glutamate to account for the observed heterotrophic doubling time on glutamate was close to those measured with isotope techniques. The kinetic parameters for glutamate uptake, which followed Michelis-Menten kinetics, were Ks = 0.018 mM, and Vmax = 7.0 X 10(-10) mumol per cell per minute. Although several amino acids served as sole nitrogen sources for photoautotrophic growth and were demonstrated by the use of isotope techniques to enter the cells, they could not be used as substrates for growth in the dark. Glucose was not taken up to a significant extent except by cells grown in the presence of tryptone. Lactate was taken up only by dark-grown cells. Results of preliminary studies on the metabolic fate of several uniformly labeled amino acids are presented.     

The transfer of Fragilaria obtusa Hustedt to the genus Staurosira Ehrenberg (Bacillariophyceae)

The ultra‐structure of the frustule of the rarely recorded diatom Fragilaria obtusa Hustedt was studied in detail using sand samples from Laranjal Bay (Lagoa dos Patos Rio Grande do Sul State, Brazil). F. obtusa is transferred to the genus Staurosira Ehrenberg as Staurosira obtusa (Hustedt) Garcia. The taxon is characterized by striae composed of elliptical areolae that are occluded by an internal velum, apical pore field formed by several rows of rimmed pores, girdle bands free of ornamentation, wide valvocopulae, and absence of rimoportulae. This is the first record of S. obtusa from an epipsammic habitat.     

Examination of diatom type material: Nitzschia delicatissima Cleve,Thalassiosira minuscula Krasske,and Cyclotella nana Hustedt

Type material of Thalassiosira minuscula Krasske and material identified by the respective authors as Nitzschia delicatissima Cleve and Cyclotella nana Hustedt (= Thalassiosira pseudonana Hasle et Heimdal) have been examined in light and electron microscopes. It is suggested that the slide labelled “Nitzschia delicatissima Helder 7/5–97” is accepted as neotype of the species since the original material must be regarded as lost, and that Thalassiosira pseudonana is identical to the diatom isolated by Guillard as clone 3-H. Nitzschia actydrophila Hasle and Thalassiosira monoporocyclus Hasle are rejected as separate species, the first being conspecific with N. delicatissima and the second with T. minuscula. The question is raised whether more emphasis should be laid on iconotypes of small diatom species identifiable only in the electron microscope than on real individuals.     

Androecial development and systematics inFlacourtiaceae s. l.

Androecial development of 13 species belonging to six tribes ofFlacourtiaceae has been investigated. While inScolopieae andFlacourtieae the stamens develop centrifugally, inErythrospermeae, Oncobeae andPangieae they are initiated in a centripetal sequence or a sequence that is neither distinctly centripetal nor centrifugal. The distribution of these developmental patterns coincides with the distribution of other characters (e.g. cyanogenic compounds, salicoid leaf teeth) and therefore supports a split of the family intoFlacourtiaceae s. str. (containing theScolopieae, Homalieae, Prockieae, Flacourtieae, Casearieae andBembicieae) andKiggelariaceae (withErythrospermeae, Oncobeae andPangieae) and is in accordance with results of recentrbcL studies.     

Production of carbohydrates by the marine diatom Chaetoceros affinis var. willei (Gran) Hustedt. II. Preliminary investigation of the extracellular polysaccharide

The isolation of an extracellular polysaccharide from cultures of Chaetoceros affinis var. willei (Gran) Hustedt is described. The polysaccharide behaved as a homogeneous, polyanionic compound in free-boundary electrophoresis at both pH 2 and 7. It contained sulphur, presumably as sulphate half ester groups (8.7% of SO₂Na), and the following monosaccharides were tentatively identified: rhamnose, fucose, arabinose, and galactose, with the two former constituting 63% of the polysaccharide preparation. The main cellular polysaccharide was a glucan and could be extracted from the cells by dilute acid. The remaining material gave, after hydrolysis, a complex mixture of monosaccharides with rhamnose as the major component. It is concluded that the extracellular polysaccharide is probably excreted from healthy cells.     

Genome analysis ofElymus angulatus andE. patagonicus (Poaceae) and their hybrids with N. and S. AmericanHordeum spp.

The results of genome analysis of five hybrids, viz.Elymus patagonicus ×Hordeum procerum, E. patagonicus ×H. tetraploidum, E. angulatus ×H. jubatum, E. angulatus ×H. lechleri, andE. angulatus ×H. parodii, are reported. The genomic constitution ofHordeum tetraploidum andH. jubatum is best given as H₁H₁H₂H₂, ofH. lechleri andH. parodii as H₁H₁H₂H₂H₄H₄, ofH. procerum as H₁H₁H₂H₂H₃H₃, and ofElymus patagonicus andE. angulatus as SSH₁H₁H₂H₂.     

Production of cellulases and saccharification of lignocellulosics by A. Micromonospora sp.

A locally isolated strain of Micromonospora sp. when grown on different natural cellulosic substrates gave the highest activity of carboxymethylcellulase (34 U/ml) and Avicelase (0.9 U/ml) on rice straw. Sugar cane bagasse was also a good substrate for growth and cellulase production. With commercial cellulosic substrates, highest carboxymethylcellulase (90 U/ml) and Avicelase (2.8 U/ml) activities were when the organism grew on xylan. Saccharification of sugar cane bagasse and rice straw by enzyme preparations of the organism grown on the respective substrates released 5.6 and 5.8 mg reducing sugar/ml. With all enzyme preparations, bagasse was more easily saccharified than rice straw.The authors are with the Atomic Energy Research Establishment, GPO Box 3787, Dhaka 1000, Bangladesh; N.A. Chowdhury, M. Moniruzzaman, and N. Choudhury in the Institute of Food and Radiation Biology, and N. Nahar in the Institute of Nuclear Science and Technology.     

Distinctions betweenHordeum bulbosum andH. murinum s.l. in seed and herbarium collections

It is sometimes necessary to identify eitherH. bulbosum orH. murinum on the basis of the inflorescence or seeds alone. The majority of taxonomic keys use the presence of swollen basal culms for the former against the annual habit for the latter. Confusion is due to similarities in inflorescences and spikelet morphology. Lodicules which always persist and are present beside the fruit in a mature caryopsis, and other characters such as the awns of the lemmas of the lateral spikelets enable conclusive distinction.     

Binding and precipitating activities ofErythrina lectins with complex type carbohydrates and synthetic cluster glycosides. A comparative study of the lectins fromE. corallodendron,E. cristagalli,E. flabelliformis,andE. indica

Erythrina lectins possess similar structural and carbohydrate binding properties. Recently, tri- and tetra-antennary complex type carbohydrates with non-reducing terminal galactose residues have been shown to be precipitated as tri- and tetravalent ligands, respectively, with certainErythrina lectins [Bhattacharyya L, Haraldsson M, Brewer CF (1988) Biochemistry 271034-41]. The present work describes a comparative study of the binding and precipitating activities of fourErythrina lectins,viz. E. corallodendron, E. cristagalli, E. flabelliformis, andE. indica, with multi-antennary complex type carbohydrates and synthetic cluster glycosides. The results show that though their binding affinities are very similar, theErythrina lectins show large differences in their precipitating activities with the carbohydrates. The results also indicate significant dependence of the precipitating activities of the lectins on the core structure of the carbohydrates. These findings provide a new dimension to the structure-activity relationship of the lectins and their interactions with asparagine-linked carbohydrates.Abbreviations EAL, ECorL, ECL, EFL, and EIL represent the lectins from the seeds ofErythrina arborescens, - E. corallodendron, E. cristagalli, E. flabelliformis, andE. indica respectively - AFOS thetri-antennary complex type oligosaccharide from asialofetuin - AFGP the tri-antennary glycopeptide from asialofetuin - MeGal methyl -d-galactopyranoside Unless stated otherwise all sugars are in thed-configuration.     

Genetic differentiation between Coffea liberica var. liberica and C. liberica var. Dewevrei and comparison with C. canephora

Coffea liberica Hiern includes C. liberica var. liberica (LIB) from western Africa and C. liberica var. dewevrei (DEW) from central Africa. This geographical distribution also includes cultivated C. canephora for which a within-species clustering in two interfertile groups is known. In this study, genetic differentiation between LIB and DEW was evaluated on the basis of morphological traits, molecular markers (AFLP) and male fertility of F1 hybrids. The results were also compared with the within-species differentiation in C. canephora. The morphological traits differed significantly but the distributions overlapped. By contrast, LIB and DEW constituted two distinct groups with high genetic differentiation (G_st=0.25) when using AFLP markers. In addition, the pollen viability of F1 hybrids between LIB and DEW was weak (44.2%) and similar to interspecific C. canephora x DEW F1 hybrids or C. canephora x LIB F1 hybrids, indicating that there are marked reproductive barriers between LIB and DEW.     

Production of carbohydrates by the marine diatom Chaetoceros affinis var. willei (Gran) Hustedt. I. Effect of the concentration of nutrients in the culture medium

The chemical composition of cells of Chaetoceros affinis var. willei (Gran) Hustedt grown in batch culture was markedly influenced by the concentration of nutrients in the medium. In the logarithmic growth phase the content of cellular glucan was relatively low, but in the stationary phase the glucan content showed a rapid increase which seemed to coincide with the depletion of nitrate from the medium. This led to very pronounced variations in the ratio of protein to carbohydrate. This ratio can easily be determined and seems to be a sensitive and convenient parameter for characterizing the physiological state of the diatom cells.     

Phytophthora captiosa sp. nov. and P. fallax sp. nov. causing crown dieback of Eucalyptus in New Zealand

A locally severe crown disease of exotic plantation Eucalyptus trees has been recorded periodically in New Zealand since 1986. Symptoms include leaf spots, petiole infection and twig and small branch lesions. Outbreaks of disease are episodic and individual trees may show marked variation in crown symptoms ranging from unaffected to total defoliation. Two previously unknown species of Phytophthora are associated with the disease. These are described and formally designated here as P. captiosa, from Eucalyptus botryoides and E. saligna; and P. fallax, from E. delegatensis, E. fastigata, E. nitens and E. regnans. Both P. captiosa and P. fallax have non-papillate, non-caducous sporangia and both are self-fertile. Phylogenetic analysis on the basis of ITS rDNA sequence data indicates they are closely related to each other but evolutionarily distant from the majority of described Phytophthora taxa. They share a common ancestor with another assemblage of Phytophthora lineages that includes P. insolita, P. macrochlamydospora and P. richardiae. Sporulation of P. captiosa and P. fallax has not been observed in the field. The mode of infection and spread of these non-caducous Phytophthora species in the eucalypt tree canopy remains unknown. This issue, and the possible geographic origins of these two Phytophthora species are discussed.     

Comparisons of the hybrids Hordeum chilensexH. vulgare,H. chilensexH. bulbosum,H. chilensexSecale cereale and the amphidiploid of H. chilensexH. vulgare

Summary Diploid hybrids between Hordeum chilense and three other species, namely H. vulgare, H. bulbosum and Secale cereale, are described together with the amphidiploid of H. chilensexH. vulgare. Both the diploid hybrid and the amphidiploid of H. chilensexH. vulgare were chromosomally unstable, H. chilensexH. bulbosum was less so, while H. chilensexS. cereale was stable. Differential amphiplasty was found in all combinations. No homoeologous pairing was found in the Hordeum hybrids but in H. chilensexS. cereale there was chromosome pairing both within the two genomes and between the genomes.     

Taxonomic studies on three marine pleurostomatid ciliates, Litonotus bergeri nov. spec., L. blattereri nov. spec. and L. petzi nov. spec. (Ciliophora, Pleurostomatida) from North China Sea

The morphology and infraciliature of three pleurostomatid ciliates, Litonotus bergeri nov. spec., L. blattereri nov. spec. and L. petzi nov. spec., collected from mariculture ponds near Qingdao (Tsingtao), China, were investigated using live observations and the protargol impregnation method. These new species are distinguished from their congeners by a combination of characters including the typical distribution of extrusomes, i.e., along entire ventral margin, the number of macronuclear nodules, features and number of somatic kineties, living morphology, number and position of contractile vacuoles and their marine biotopes. Considering the distribution of extrusomes and general morphology, five new combinations are suggested, Litonotus vermiforme (Sauerbrey, 1928) nov. comb. [basionym: Loxophyllum vermiforme Sauerbrey, 1928], Litonotus levigatum (Sauerbrey, 1928) nov. comb. [basionym: Loxophyllum levigatum Sauerbrey, 1928], Litonotus undulatum (Sauerbrey, 1928) nov. comb. [basionym: Loxophyllum undulatum Sauerbrey, 1928], Loxophyllum pictus (Gruber, 1884) nov. comb. [basionym: Litonotus pictus Gruber, 1884] and Loxophyllum trichocystiferus (Foissner, 1984) nov. comb. [basionym: Litonotus trichocystiferus Foissner, 1984].