bluuebunny/crossref_metadata_2025_split huggingface dataset:
THE ULTRASTRUCTURE OF MEIOSPORES OF COLEOCHAETE PULVINATA (CHAROPHYCEAE)1
Authors: Graham Linda E. , Taylor Claude 
Published: March 2008

ABSTRACT In view of the relative importance of reproductive cell ultrastructure in phylogenetic and systematic studies of green algae, we investigated the fine structure of germinating zygotes and meiospores of Coleochaete pulvinata Braun. Meiospores have a flagellar apparatus very similar to that of zoospores and spermatozoids of the same species. Meiospores differ from zoospores and spermatozoids of C. pulvinata in having pyramidal body scales similar to those present on zoospores of C. scutata. Meiospores of C. pulvinata had as many as twice the number of spline microtubules as zoospores, and four times the number present in splines of spermatozoids of the same species. Developing meiospores of C.pulvinata, like those of other Coleochaete species, are individually surrounded by chamber walls. These differed from vegetative cell walls in lacking plasmodesmata. Moreover, the chamber walls in germinating zygotes of C.pulvinata stained a cobalt blue color with resorcinal blue, and fluoresced yellow in the presence of aniline blue, thus exhibiting the staining characteristics of callose. In location, morphology and presence of callose, chamberwalls resemble “special walls” of land plants, they may represent a charophycean spore development preadaptation useful in the evolution of walled spores characteristic of land
EFFECTS OF CO2 CONCENTRATION DURING GROWTH ON THE INTRACELLULAR STRUCTURE OF CHLORELLA AND SCENEDESMUS (CHLOROPHYTA)1
Authors: Miyachi Shigetoh , Tsuzuki Mikio , Maruyama Isao , Gantar Miroslav , Miyachi Shizuko , Matsushima Hisashi 
Published: March 2008

ABSTRACT Effects of CO2 concentration during growth on intracellular structure were studied with ftve species of Chlorella and Scenedesmus obliquus. Cells grown under ordinary air conditions (low‐CO2 cells) had a well developed pyrenoid surrounded by starch, while those grown under high CO2 conditions (high‐CO2 cells) had a less developed pyrenoid or no detectable pyrenoid. Two mitochondria, one at each side of the neck of the projection of the chloroplast close to the pyrenoid, were found in low CO2 cells of C. vulgaris 11h. Usually, lamellar stacks extended in parallel in the chloroplast of low‐CO2 cells of C. vulgaris 11h, while a grana‐like structure was found in high‐CO2 cells. However, in C. pyrenoidosa, grana like structures were found more commonly in low‐CO2 cells than in high‐CO2 cells. These results suggest that development of pyrenoid starch is generally correlated with growth under low CO2 conditions, whereas CO2‐effects on lamellar stacking are species dependent.
CELLULAR MOVEMENT IN THE CENTRIC DIATOMODONTELLA SINENIS1
Authors: Pickett‐Heaps Jeremy D. , Hill David R. A. , Wetherbee Richard 
Published: March 2008

ABSTRACTCultured, actively growing cells ofOdentella sinensissecrete mucilage, forming gelatinous masses; the mucilage can be visualised with Alcian Blue. When examined live with the light microscope, many cells exhibited continuous small shuffing and rocking movements that could last for long periods (30‐40 min); the cells, however, were not translocated and remained relatively fixed in position with respect to their neighbours.Ultrastructural examination of these cells showed prominent aggregations of mucilage vesicles, derived from the Golgi bodies, at the base of the labiate processes, each of which is close to an elevation bearing an ocellus. In Ditylum brightwellii, similar aggreations of these vesides were also located at teh labiate processes; this diatom, too, secretes mucilage but does not have ocelli. We conclude that the movements observed inO. sinenisisare an indirect result of active muilage secretion through the labiate process. It has been suggested that the raphe may have evolved from the labiate process; our conclusion, therefore, has phylogenetic implications, suggesting a functional as well as a morphological relationship between the two valve structures.
EFFECTS OF CURRENT VELOCITY AND LIGHT ENERGY ON THE STRUCTURE FO PERIPHYTON ASSEMBLAGE IN LABORATORY STREAMS1
Authors: Steinaman Alan D. , McIntire C. David 
Published: March 2008

ABSTRACTEffects of current velocity and light energy on the taxonomica and physiognomic characteristics of periphyton assemblages were investigated in laboratory streams. The initial rate of colonization was related to current velocity, while the effects of light energy accounted for differences in species composition by the end of the experiment. Although the laboratory systems had many species in common during the realy stages of colonization, the experimental treatments generated differences in rates of communitydevelopment. synedra spp. were the early coloniters of the substrate, followed by an understory of Achnanthes spp. After day 16, Stigeoclonium tenue developed in the streams exposed to the higher photon flux density, but was rare in the shaded streams. The applicability of traditional successional theory to develoopmental patterns in lotic periphyton assemblages is discussed.
OCCURRENCE OF RICHELIA INTACELLULARIS (CYANOPHYTA)WITHIN THE DIATOMMMS HEMIAULUS HAUKII ADN H. MEMBRANACEUS OFF HAWAII1
Authors: Heinbokel John F. 
Published: March 2008

ABSTRACTThe presence of nitrogen–Fixing cyanobacterial endophytes, such as Richelia intracellularis Schmidit commonly observed within several species of Rhizosolenia, in nitrogen‐limited oceanic waters has obvious implications both for the host organism(s) and for the entire planktonic assemblage. Recently, epi‐fluorescent examination of pllankton samples collected off Oahu, Hawaii, in september 1982 revealed R. intracellularis within the diatoms Hemiaulus membranaceus Cleve and H. hauckii Grunow as well as its expected presence within Rhizosolennia spp. Richelia intracellularis coccurred with within Hemiaulus spp. at frequenccies (ca.80%)comparable to those noted for Rhizosolenia spp. Standard bright field or phaseconrast microsocopy could not reliably distinguish the cyanobacteria within Hemiaulus spp. If this association is common, the occurrence of R.intracellularis (and its significance in the nitrogen dynamics of the ocean)may have been greatly underestimated in previous studies.
THE FLAGELLAR APPARATUS OF GYMNODINIUM SP. (DINOPHYCEAE)1
Authors: Roberts Keith R. 
Published: March 2008

ABSTRACT The detailed structure of the flagellar apparatus has been determined in a small dinoflagellate of the genus Gymnodinium. Although diminutive, this dinoflagellate possesses a complex flagellar apparatus consisting of a posteriorly directed microtubular root, a transverse striated fibrous root, several striated fibrous connectives that attach the basal bodies to one another as well as to the different roots, and a conspicuous non‐striated fibrous connective that directly links the posteriorly directded microtubular root with the extended lobe of the nucleus. This represents the second discovery of a nuclear connective linked to the flagellar apparatus in the Dinophyceae but is the first report to elucidate the spatial relationships of the connective with the flagellar apparatus and the cell. A detailed diagrammatic reconstruction is provided and the similarities between these flagellar apparatus features are compared with those known for other dinoflagellates. Additionally, the structure and displacement of the nuclear connective are compared with nuclear connectives described in other protists.
ULTRASTRUCTURE OF MEIOSIS INDASYA BAILLOUVIANA(RHODOPHYTA). II. PROMETAPHASE I—TELOPHASE II AND POST‐DIVISION NUCLEAR BEHAVIOR1
Authors: Broadwater Sharon , Scott Joe , Pobiner Bonnie 
Published: March 2008

ABSTRACTThis is the second of two papers which together are the first comprehensive ultrastructural report of meiosis in a red alga. Many details of the meiotic process inDasya baillouviana (Gmelin) Montagne are the same as those reported previously for mitotic cells in ceramialian red algae, but several characteristics seem unique to meiotic cells. The nucleus and nucleolus of meiotic cells are larger than those of mitotic cells and large accumulations of smooth ER are often found at the division poles during meiosis 1. The function of the ER accumulations is unknown. Importantly, both interkinesis and a simultaneous division of two separate nuclei during meiosis II was demonstrated. These new observations fail to support earlier speculation on higher red algae for a “uninuclear” meiosis (both nuclear divisions within the same nuclear envelope). However, following meiosis II the four nuclei migrate centripetally and possibly fuse in the center of the tetrasporangium. This post‐division nuclear maneuvering is not understood, but our interpretation accounts for the earlier and erroneous impression of “uninuclear” meiosis. Perhaps the most important aspect of meiosis observed inDasya isits basic adherence to the pattern commonly seen in higher plants and animals. This conservatism of the meiotic process lends further skepticism to the belief that red algae are extremely “primitive” organisms, although they undoubtedly represent a very “ancient” group of eukaryotic plants.
GENETICS OF CHAMPIA PARVULA (RHODYMENIALES. RHODOPMYTA): MENDELIAN INHERITANCE OF SPONTANEOUS MUTANTS1,2
Authors: Steele Richard L. , Thursby Glen B. , van der Meer John P. 
Published: March 2008

ABSTRACT Spontaneous mutants affecting the morphology and pigmentation of the small marine red alga Champia parvula were genetically characterized. All of the variants were transmitted in the Mendelian pattern expected for recessive nuclear mutations. The results permit the identification of four mutant genes affecting morphology and four mutant genes affecting pigmentation. One of the latter, designated yell, was interesting in that it also appeared to act as a recessive lethal during carposporophyte development. So linkage bas been discovered in crosses conducted thus far. Champia parvula was found to have many desirable features for genetic studies, especially a very rapid sexual life cycle, and it is suggested that this species should be considered as a possible model organism for future genetic studies on the Rhodophyta or for teaching seaweed genetics.
DESM1D ZYGOTES IN EAST TEXAS1
Authors: Smith Betsy B. 
Published: March 2008

ABSTRACT In an extensive survey for desmids in 217 lakes and ponds in 21 counties of east Texas, desmid zygotes were infrequently encountered. A list is given of zygotes of 22 species in 9 genera. Two zygotes previously unobserved are described and illustrated in photographs and camera lucida drawings.
EXOGENOUS STEROIDS AND GROWTH OF NEOSPONGIOCOCCUM SP. (CHLOROPHYTA)1
Authors: Hardy Mark G. , O'Kelley Joseph C. 
Published: March 2008

ABSTRACT Of the various types of steroids found in nature, only sterols (steroids whose molecules possess an 8‐ to 10‐carbon atom hydrocarbon side chain at position 17 of the perhydrocyclopentanophenanthrene ring) are known to be common constituents of algae. Little is known of the effects of steroids in the environment upon the growth and survival of algae. This paper investigates the growth of the green alga Neospongiococcum sp. in medium containing steroids. Bile acids are not inhibitory, even at a concentration of 100 ppm. Some sterols inhibit growth when present in the medium at a concentration of 100 ppm, but not at 10 ppm. Testosterone and β‐estradiol, which have no carbon atom side chain at ring position 17, inhibit growth at a concentration of only 10 ppm. Steroids whose molecules possess a 2‐carbon atom side chain at ring position 17 and a keto group at the α‐carbon of this side chain, such as pregnenolone, inhibit growth at a concentration of as little as 1 ppm. Respiration is also inhibited by pregnenolone at this level.
NUTRITIONAL REQUIREMENTS FOR SEXUAL REPRODUCTION INMESOTAENIUM KRAMSTAI(CHLOROPHYTA)1
Authors: Tiflickjian John D. , Raybum William R. 
Published: March 2008

ABSTRACTOptimum conditions for conjugation in the heterothallic saccoderm desmid Mesotaenium kramstai Lemmer‐mann have been determined. In culture, cells acquired the ability to form gamete pairs just prior to the onset of stationary phase after sufficient nitrate had been depleted from the medium. The appearance of potential gametes was delayed by increasing the concentration of KNO3When cells of both mating types were harvested from 15 to 18 day old cultures, washed, resuspended in fresh medium, and mixed, approximately 50 percent of the cells paired (measured three days after mixing) in a medium containing 0.13 mM or less KNO3. At greater concentrations, fewer pairs formed; no pairs formed in medium containing 0.5 mM KNO3. Conjugation was not inhibited by other macronutrients.Calcium and magnesium were essential for maximum conjugation. Although Ca2+and Mg2+contentrations of 0.05 mM and 0. I mM, respectively, were sufficient for optimum growth, maximum conjugation required more than 10 times these values. Few gamete pairs formed when either Ca2+or Mg2+was omitted from the medium, no pairing occurred when both Ca2+and Mg2+were omitted.
IRRADIANCE, DAYLENGTH AND TEMPERATURE EFFECTS ON ZOOSPOROGENESIS IN COLEOCHAETES CUTATA (CHAROPHYCEAE) 1
Authors: Graham Linda E. , Graham James M. , Kranzfelder James A. 
Published: March 2008

ABSTRACTUsing a factorial design, we investigated the effects of 150 different combinations of irradiance, daylength and temperature on zoosporogenesis in Coleochaete scutata. Analysis of variance (ANOVA) revealed that irradiance and daylength did not .significantly influence the response, out that temperature was highly significant. Exposure of thalli to 20°C for one to several days is sufficient to induce zoospore production in C. scutata and several other northern temperature species of Coleochaete. Results of the factorial experiment correlate well with field observations on the seasonal occurrence of asexual reproduction in several Coleochaete species. A technique based on results of this factorial study is described for using zoospores to obtain morphologically normal, unialgal cultures of Coleochaete .sp. It was concluded that the factorial approach to investigation of environmental control of zoosporogenesis can be a powerful tool for understanding natural algal population dynamics, as well as controlling growth and reproduction of algae in the laboratory.
GROWTH, PHOTOSYNTHESIS AND MAINTENANCE METABOLIC COST IN THE DIATOM PHAEODACTYLUM TRICORNUTUM AT VERY LOW LIGHT LEVELS 1
Authors: Geider Richard J. , Osbonie Bruce A. , Raven John A. 
Published: March 2008

ABSTRACT The compensation point for growth of Phaeodactylum tricornutum Bohlin is less than 1 μmol. m−2s−1. Growth at low PFDs (<3.5 μmol. m−2.s−1) does not appear to reduce the maximum quantum efficiency of photosynthesis (øm) or to greatly inhibit the potential for light‐saturated, carbon‐specific photosynthesis (Pmc). The value for øm in P. tricornutum is 0.10–0.12 mol O2‐mol photon−1, independent of acclimation PFD between 0.75 and 200 μmol.m−2.s−1 in nutrient‐sufficient cultures. Pmc in cells of P. tricornutum acclimated to PFDs <3.5 μmol m−2−s−1 is approximately 50% of the highest value obtained in nutrient‐sufficient cultures acclimated to growth‐rate‐saturating PFDs. In addition, growth at low PFDs does not severely restrict the ability of cells to respond to an increase in light level. Cultures acclimated to growth at lees than 1% of the light‐saturated growth rate respond rapidly to a shift‐up in PFD after a short initial lag period and achieve exponential growth rates of 1.0 d−1 (65% of the light‐ and nutrient‐saturated maximum growth rate) at both 40 and 200 μmol.m−2.s−1
ELECTROPHYSIOLOGICAL INVESTIGATIONS OF THE RED ALGA GRIFFITHSIA PAGIFIG AKYL. 1
Authors: Bauman Robert W. , Jones Bradley R. 
Published: March 2008

ABSTRACT The membrane potentials of the plasmalemma and tonoplast in Griffithsia pacifica Kyl were measured and shown to be significantly different. No consistent cell wall potential was discovered. Adjacent cells in the filament were demonstrated to be electrolonically coupled with a mean coupling coefficient of 0.13. Cobaltions did not move between cells. No dye coupling was seen using the fluorescent dye Lucifer yellow CH. These observations provide new information on the electrophysiology of red algae and indicate that there is intercellular continuity between the cells of a filament of Griffithsia pacifica.
DARK CARBON FIXATION STUDIES ON THE INTERTIDAL MACROALGA ASCOPHYLLUM NODOSUM (PHAEOPHYTA) 1
Authors: Johnston Andrew M. , Raven John A. 
Published: March 2008

ABSTRACT The characteristics of dark carbon fixation by Ascophyllum nodosum were investigated. In longitudinal profile the maximum rates of dark and light dependent fixation are found at the apex. The use of Michaelis‐Menten kinetics did not suitably describe the relationship between the uptake rate in the dark and the total inorganic carbon concentration. Dark fixation was saturated at a total inorganic carbon concentration [TIC] of 2.5 mM. The use of the Hill‐Whittingham equation to describe the uptake curve indicates that the process is diffusion limited. Comparisons of dark fixation at high (8.0) and low (5.2) pH suggest that bicarbonate ions are used as a source of inorganic carbon. The transfer of 14C, fixed in the dark, from the ethanol soluble to the insoluble fraction was relatively slow irrespective of the light treatment during the chase period. Ascophyllum nodosum displays a small diel fluctuation in the pH of aqueous extracts and titratable acidity similar to that displayed by CAM plants. The significance of dark fixation to the overall carbon budget is discussed.
A POLYPLOID SPECIES COMPLEX OF SPIROGYRA COMMUNIS (CHLOROPHYTA) OCCURRING IN NATURE 1
Authors: Wang Jen‐Chyong , Hoshaw Robert W. , McCourt Richard M. 
Published: March 2008

ABSTRACTInvestigations were conducted to determine whether ploidal changes found in laboratory cultures of Spirogyra also occur in nature. In an earlier study filament types identifiable as three different species (Spirogyra singu‐laris Nordstedt, S. communis (Hassall)Kütz., S. fragilis Jao) arose from an original clonal culture through vegetative growth and sexual reproduction. These three “species” or filament groups differed in filament width, chloroplast number, zygospore size, and chromosome number. The differences in chromosome number represented a polyploid series of diploid (S. communis), triploid (S. fragilis), and tetraploid (S. singularis) forms in which width increased with ploidal level. The three width groups constituted a “species complex.” Five years after isolation of the original strain in this species complex, filaments corresponding to two of the width groups (S. singularis and S. communis) were found at the original collection site in the Santa Catalina Mountains in southern Arizona. The two field‐collected groups were indistinguishable from the laboratory species complex in morphology and chromosome number. Homothallic conjugation within the two field width groups yielded progeny similar to those from homothallic conjugation of groups in the laboratory species complex. Filament widths of progeny were generally within the width limits of respective parental groups. The four possible intergroup crosses between the two laboratory and two field width groups yielded progeny similar to the wider parent (S. singularis) or the parent of intermediate width (S. fragilis). Progeny characteristics were determined by the width groups of parents, regardless of whether parents came from the laboratory or field. The similarities in morphology, chromosome numbers, and reproductive behavior of laboratory and field width groups imply that the laboratory species complex of S. communis has a natural counterpart in the field.
IRON‐MEDIATED CHANGES IN THE GROWTH OF LAKE ERIE PHYTOPLANKTON AND AXENIC ALGAL CULTURES1
Authors: Storch Thomas A. , Dunham Valgene L. 
Published: March 2008

ABSTRACTThe effect of iron enrichment on algal growth and photosynthesis was investigated using natural assemblages of Lake Erie phytoplankton and axenic cultures of Anabaena, Scenedesmus and Selenastrum. Cell yield and photosynthesis were frequently inhibited in the presence of unchelated iron over the range of 3.6 to 53.7 μM iron as FeCl3. In lake water and in a defined medium with low nutrient concentrations, the degree of inhibition by iron could be reduced by chelating the iron with EDTA or by enriching the cultures with phosphorus. Chemical analyses revealed that the EDTA efectively reduced the ability of the ferric iron to remove soluble phosphorus from the media. EDTA was also observed to reduce rather than enhance iron uptake by axenic cultures of A. flos‐aquae. These data support the hypothesis that additions of EDTA to low‐nutrient media may serve to stimulate algal growth in the presence of iron by preventing the iron from altering extracellular concentrations of soluble ions essential for algal metabolism. In medium with high nutrient concentrations, the soluble phosphorus concentration was not appreciably altered by either EDTA‐chelated or unchelated iron enrichment (0.9 to 53.7 μM). Instead, the observed enhancement of cell yield by EDTA‐chelated iron in nutrient‐rich media appeared to be due to the direct effect of iron on intracellular metabolic processes.
GROWTH OF COLPOMENIA PEREGRINA (PHAEOPHYCEAE) IN CULTURE: EFFECTS OF SALINITY, TEMPERATURE AND DAYLENGTH1
Authors: Vandermeulen Herbert 
Published: March 2008

ABSTRACTIncreases in size of Colpomenia peregrina (Sauv.) Hamel microthalli were determined at six different combinations of salinity and temperature under laboratory conditions. Microthalli grown at low salinity (15%) did not have a growth rate significantly different from microthalli grown at high salinity (30%). However, more macrothalli were produced in higher salinity media. Fewer macrothalli were produced at lower temperatures.Growth of C. peregrina microthalli was also determined at six different combinations of daylength and temperature. Microthalli under 15:9 h (LD cycle) did not have a growth rate significantly different from microthalli under 9:15 h LD. However, more macrothalli were produced under long day conditions. Of the three different temperatures utilized (5, 13 and 20° C) only 5° C produced significantly different growth rates. Low temperature reduced growth to such an extent that macrothalli of a size that could be recognized in the field took approximately two months to produce in culture. These results may explain the seasonal presence/absence of the delophycean phase of C. peregrina in the field.Zoospore survivorship and macrothallus production of C. peregrina in culture indicated that both PES and an artificial medium were suitable for the laboratory cultivation of this plant.