bluuebunny/crossref_metadata_2025_split huggingface dataset:
COMPARATIVE ANALYSES OF THE DINOFLAGELLATE FLAGELLAR APPARATUS. II. CERATIUM HIRUNDINELLA1
Authors: Roberts Keith R. 
Published: November 2006

ABSTRACTThe three‐dimensional structure of the flagellar apparatus in the gonyaulacoid dinoflagellate. Ceratium hirundinella var. furcoïdes (Schröder) Hub.‐Pest. was determined using serial section electron microscopy. The flagellar apparatus is quite large and consists of several components. The two basal bodies nearly abut at their proximal ends and are separated by an angle of approximately 120° The broad longitudinal microtubular root extends from the cell's left edge of the longitudinal basal body and bends around the sulcal/cingular depression into the cell's left antapical horn. A transverse striated fibrous root is associated with the transverse basal body and a narrow electron dense extension is present along the anterior edge of the transverse basal body. This study revealed severa1 hitherto unreported fibrous components of the flagellar apparatus that link the various microtubular and fibrous components to themselves and to the two striated collars. A large striated fibrous connective links the two striated collars to one another. This fibrous connective is linked to another striated fibrous connective that originates from the longitudinal basal body and lies perpendicular to the longitudinal microtubular root. The readily identifiable and numerous components of the Ceratium flagellar apparatus are comparable to those of other dinoflagellates. The combined presence of well dpveloped striated collars, a striated collar connective, and a basal body angle of approximately 120° indicates that this flagellar apparatus is most like that described for Peridinioid dinoflagellates. Important similarities are also noticeable between this flagellar apparatus and that of Oxyrrhis marina.
UPTAKE, METABOLISM, AND RELEASE OF CAMP IN SELENASTRUM CAPRICORNUTUM (CHLOROPHYCEAE)1
Authors: Francko David A. 
Published: November 2006

ABSTRACTUptake rate, intracellular metabolism, and extracellular release of cAMP were examined in batch cultures of the unicellular alga Selenastrum capricornutum Printz (Chlorophyceae). cAMP uptake was linearly dependent on external substrate concentration (0.5 nM to 1 mM) over a broad range of culture cell densities (1.7‐5 × 106cells. mL−1) to mid‐to‐late log phase growth. Chromatographic analyses indicated that the majority of assimilated [3H]‐cAMP was converted within 30 min to radiolabelled material which co‐chromatographed with ADP/ATP and adenosine. About 20% of the (3H]‐label originally added to cells as a [3H]‐cAMP was released to the extracellular medium within 10 min, and chromatographic analyses demonstrated that most of the radiolabelled material was released as cAMP. Analyses with cell suspensions preincubated in KCN or DCMU suggested that cAMP release, but not uptake, was repressed by respiratory or photosynthetic electron flow inhibitors. However, the data were consistent with a passive CAMP uptake mechanism only if much of the assimilated CAMP was bound or compartmentalized.
PH‐DEPENDENCE OF CHLORTETRACYCLINE(CTC)‐INDUCED PLUG FORMATION IN NITELLA FLEXILIS (CHARACEAE)1
Authors: Foissner Ilse 
Published: November 2006

ABSTRACTThe formation of chlortetracycline(CTC)‐induced wall appositions (callose plugs) in Nitella flexilis (L.)Ag. was pH‐dependent in the range between 4.3‐8.3. Plug number and plug diameter increased with the pH of the CTC solution. At pH 4.3 plug formation was light‐dependent and occurred below the alkaline regions of the cell surface which form during photo synthetic assimilation of HCO3−. Inhibition of photosynthesis by 3–(3′,4′‐dichlorophenyl)‐1, 1‐dimethylurea prevented plug formation in the light. Dark‐treated cells could be induced to form plugs by raising the pH of the CTC solution. The formation of large but incomplete plugs in the presence of cytochalasin B is explained by the formation of numerous weak alkaline sites. I suggest that CTC enhances locally the Ca2+content at the cytoplasm near the plasmamembrane. The ionophoric character of CTC is probably more pronounced at high pH mainly because of a weaker binding with cations and a closer contact with the membrane.
PHOTOSYNTHESIS OF ALGAL CULTURES AND PHYTOPLANKTON FOLLOWING AN ACID pH SHOCK1
Authors: Nalewajko Czeslawa , O'Mahony Margaret A. 
Published: November 2006

ABSTRACTIn acidifying lakes, pH decreases abruptly in response to acid precipitation events. We tested the hypothesis that, in comparison to a circumneutral lake, phytoplankton photosynthesis in an acidifying lake is less sensitive to a rapid decrease in pH (acid pH shock).Phytoplankton in Plastic Lake, which is undergoing acidification, was characterized by a predominance of Pyrrophyta, and phytoplankton photosynthesis decreased to a lesser extent in response to an acid pH shock than the photosynthesis of populations from St. Nora Lake, a circumneutral lake located nearby, in which Pyrrophyta were not abundant. Rates of phytoplankton photosynthesis in acid pH shock experiments were significantly correlated with hydrogen ion but not with dissolved inorganic carbon (DIC) concentrations.Depression of photosynthesis following an acid pH shock occurred in axenic cultures of Chlorella pyrenoidosa Chick but was not observed in axenic cultures of the acidophilic alga Chlorella saccharophila (Krug.) Nadson or in three species isolated from Plastic Lake. However, the three isolates were not acidophilic during growth. We conclude that phytoplankton in acidifying lakes consists predominantly of species which are tolerant to acid pH for short periods (hours) but cannot grow at these pHs.
MORPHOLOGY AND DEVELOPMENT OFAHNFELTIA PLICATA(RHODOPHYTA): PROPOSAL OF AHNFELTIALES ORD. NOV.1
Authors: Maggs Christine A. , Pueschel Curt M. 
Published: November 2006

ABSTRACTAhnfeltia plicata (Hudson) Fries, the type species ofAhnfeltiaFries, is currently assigned to the Phyllophoraceae (Gigartinales). Several morphological and biochemical characters distanceA. plicatafrom the Phyllophoraceae but, because sexual reproduction has never been demonstrated, an alternative placement has not been possible.A. plicatanow is shown to have a heteromorphic sexual life history. Erect branched gametophytes are dioecious. In male sori, spermatangia are cut off transversely from spermatangial mother cells. Female sori form numerous terminal sessile carpogonia. Following fertilization, several zygotes in each sorus fuse facultatively with undifferentiated intercalary cells of the female sorus and cut off gonimoblast initials obliquely outwards. These initials give rise to branching gonimoblast filaments that fuse with apical and intercalary female sorus cells and with each other, then grow radially outward in the compound external carposporophyte and terminate in carposporangia. Carpospores develop in culture into crustose tetrasporophytes identical toPorphyrodiscus simulansBatters. Field‐collectedP. simulanstetraspores grew into erectA. plicataaxes. Tetrasporangia are formed by division and enlargement of crust apical cells followed by sequential enlargement and maturation of tetrasporocytes in an erosive process. Monosporangia are formed in sori on male gametophytes. Pit plugs of both gametophyte and tetrasporophyte phases consist of naked plug cores without cap layers of membranes. Gametophytes exhibit both cell fusions and secondary pit connections whereas tetrasporophytes form cell fusions but lack secondary pit connections. On the basis of the unique female and postfertilization reproductive development and in conjunction with the pit plug structure which is unique among florideophytes, the order Ahnfeltiales, containing the family Ahnfeltiaceae, is proposed.
DIEL CHANGES IN THE COMPOSITION OF PHOTOSYNTHETIC PIGMENTS AND CELLULAR CARBON AND NITROGEN IN PYRAMIMONAS PARKEAE (PRASINOPHYCEAE)1
Authors: Kohata Kunio , Watanabe Masataka 
Published: November 2006

ABSTRACTDiel changes in mean cell volume, cellular carbon (carbon content per cell), cellular Chl a, C/N ratio, Chl a/carbon ratio and pigment composition were determined for an axenic clonal culture of Pyramimonas parkeae Norris et Pearson through three 12:12 h LD cycles in a laboratory culture tank of 1 m3. Mean cell volume and cellular C, N and most pigments increased during the light period as a result of photosynthesis and decreased with an increase in cell density by phased cell division during the dark period. Chi a and Chi b increased in a parallel manner during the light period. Increases in the diel synthesis pattern of carotenoids varied. Violaxanthin and lutein content increased for a few hours at the beginning of the light period and preceeded that of neoxanthin. The diel synthesis pattern of neoxanthin was similar to that of Chi a. Increases of loroxanthin and its ester form were slower than that of Chi a at the beginning of the light period. A net increase of α‐carotene was observed during the dark period. Mass spectroscopy of carotenoid structure showed a new xanthophyll, loroxanthin dodecenoate, in this species.
EVIDENCE THAT THE NUCLEOMORPHS OF CHLORARACHNION REPTANS (CHLORARACHNIOPHYCEAE) ARE VESTIGIAL NUCLEI: MORPHOLOGY, DIVISION AND DNA‐DAPI FLUORESCENCE1
Authors: Ludwig Martha , Gibbs Sarah P. 
Published: November 2006

ABSTRACTChlorarachnion reptans Geitler shows affinities to both the Chlorophyceae and the chloroplast endoplasmic reticulum‐containing chromophyte algae in possessing chlorophyll b and chloroplasts which are limited by four membranes, respectively. In the periplastidal compartment surrounding each of the four to eight chloroplasts of a C. reptans cell are putative eukaryotic‐sized ribosomes, scattered tubules and vesicles, and a small double‐membrane‐limited nucleus‐like organelle named the nucleomorph. The nucleomorphs display 4′‐6‐diamidino‐2‐phenylindole (DAPI)fluorescence which is sensitive to DNase digestion, but not to treatment with RNase. The nucleomorphs also contain a fibrillogranular body which resembles a nucleolus. Nucleomorph division occurs by the sequential infolding of the inner and outer envelope membranes and subsequent constriction in two, with no involvement of microtubules. In all these characteristics, the nucleomorphs of C. reptans are similar to the cryptomonad nucleomorph which has been hypothesized to be the vestigial nucleus of an ancestral red alga which gave rise to the chloroplasts of the Cryptophyceae. The presence of chlorophyll b and the contents and morphology of C. reptans chloroplast compartments suggest a green algal origin for the chloroplasts of these cells. The discovery of a second organism with a DNA‐containing, nucleus‐like organelle in its chloroplast compartment lends strong support to the hypothesis that the chloroplasts of many algae have evolved from eukaryotic endosymbionts.
INFLUENCE OF CELL SHAPE AND SIZE ON ALGAL COMPETITIVE ABILITY1
Authors: Grover James P. 
Published: November 2006

ABSTRACTAllometric relations between physiological processes and cell volume and surface area are combined with the variable‐internal‐stores model of growth to predict the ability of hypothetical phytoplankton to compete for phosphorus at equilibrium. The analysis shows that for spherical cells, smaller cells are better competitors than large ones. For cells that are very elongated in shape, however, large cells are often better competitors than small ones. The cells predicted to be the best competitors compare favorably in size and shape with the species observed to dominate in phosphorus‐limited chemostats at equilibrium.
UNIQUE LOCATION OF THE PHYCOBILIPROTEIN LIGHT‐HARVESTING PIGMENT IN THE CRYPTOPHYCEAE1
Authors: Spear‐Bernstein Laurel , Miller Kenneth R. 
Published: November 2006

ABSTRACTThe cryptophyte algae, or cryptomonads, comprise a small algal group with a unique photosynthetic apparatus. Both a chlorophyll a/c2light‐harvesting complex and a phycobiliprotein antenna (which can be either phycoerythrin or phycocyanin) are present, with the phycobiliprotein playing the major role in harvesting light for photosynthesis. Longstanding circumstantial evidence suggested that, in cryptophytes, the phycobiliprotein is located in the intrathylakoid space (thylakoid lumen) rather than on the outer surface of the thylakoid as part of a phycobilisome as in other algae. We used immunogold labeling to show conclusively that 1) the phycoerythrin (PE) of the cryptophyteRhodomonas lensPascher and Ruttner is located within the intrathylakoid space, 2) the PE is not exclusively bound to the thylakoid membrane but instead is distributed across the thylakoid lumen and 3) a fraction of this PE is tightly associated with the thylakoid membrane. The thylakoids are not everted to compensate for this unusual arrangement. The location of the major light‐harvesting pigment on the “wrong” side of the otherwise very normal photo‐synthetic membrane is unexpected, unique to the cryptophytes, and, remarkably, does not impair the photosynthetic abilities of this organism. A model is presented which incorporates these results ‐with previous information to give a complete structural picture of the cryptophyte light‐harvesting apparatus.
HEAVILY LICHENIZED PHYSOLINUM (CHLOROPHYTA) FROM A DIMLY LIT CAVE IN MISSOURI1
Authors: Davis Joseph S. , Rands David G. , Lachapelle Mario 
Published: November 2006

ABSTRACT Heavily lichenized Physolinum monile (De Wildem.) Printz from damp limestone walls in a dimly lit cave located in Missouri was studied from fresh collections and specimens fixed in situ, and from cultures. The narrow (7‐13 μm wide thallus), profusely branched plant consisted of filaments of the alga P. monile ensheathed by clear fungal cells (5‐8 in a single layer) that adhered tightly to each other and completely covered the algal cells. Cells of P. monile filaments were uninucleate, each containing a single massive chloroplast with numerous tightly packed thylakoids and lipid droplets and surrounded by a thin layer of cytoplasm. No plasmodesmata occurred in the cellulosic crosswalls between adjacent cells. The ensheathing fungal cells contained concentric bodies, produced haustoria that penetrated the algal cells, and developed hyphae (the tips of which formed clusters of conidia). Ensheathing fungal cells were well situated and constructed to concentrate light on the algal cells. Colonies of blue‐green algae were firmly attached to the surface of the fungal cells. The association was slow growing but frequently produced and released aplanospores from the algal cells. Aplanospores were single (not attached to each other) with smooth walls or united in groups of two or more. Structures resembling lichen soredia, composed of aplanospore‐like cells attached to one or more comdia‐like cells, commonly occurred among the lichenized Physolinum filaments. The single chloroplast that occupies most of the cell's volume, the numerous, tightly packed thylakoids, and light focusing by ensheathing fungus cells may enable the organism to survive in a dimly lit environment. Because the filamentous alga reproduces only by aplanospores, we propose resurrection of the genus Physolinum. The lichenized Physolinum somewhat resembles the lichens Coenogonium moniliforme Tuck. and Cystocoleus Thwaites.
AN ENCYSTMENT STAGE, BEARING A NEW SCALE TYPE, OF THE ANTARCTIC PRASINOPHYTE PYRAMIMONAS GELIDICOLA AND ITS PALEOLIMNOLOGICAL AND TAXONOMIC SIGNIFICANCE1
Authors: van den Hoff John , Burton Harry R. , Vesk Maret 
Published: November 2006

ABSTRACTCysts of the Antarctic prasinophyte Pyramimonas gelidicola McFadden were found in water samples from a fjord and a saline lake in the Vestfold Hills, Antarctica Unialgal cultures of P. gelidicola from Ace Lake produced cysts. After ca. five weeks, tile cysts settled and adhered to the bottom of the culture flask. The cyst wall was covered by a scale type not seen on the flagellated cells; however, the base of the cyst scale was similar to the box scales of P. gelidicola motile cells. Cyst scales were also found off the continental shelf in Prydz Bay.In a 1.7 m sediment core taken from Ace Lake, both cyst scales and box scales of P. gelidicola occurred at most depths. Differences in the ratio of these two scale types at different depths in the core may indicate past ecological changes in the lake. Upper sediments of the core were dated at 5310 ± 90 yrs B.P., indicating that prasinophyte scales may be recognizably preserved for extended periods. P. gelidicola was widely distributed in saline lakes of the Vestfold Hills with salinities of 3.2–133% and temperatures ranging from – 5.0 to 10.4°C. This is the first report of encystment of P. gelidicola and, to our knowledge, is the first record of a prasinophyte with two distinctly different scale types occurring on cells during different stages of the life history.
NITROGEN LIMITATION IN ISOCHRYSIS GALBANA (HAPTOPHYCEAE). II. RELATIVE ABUNDANCE OF CHLOROPLAST PROTEINS1
Authors: Falkowski Paul G. , Sukenik Assaf , Herzig Ronny 
Published: November 2006

ABSTRACT Using spectroscopic, biophysical and immunological techniques, we assayed the relative abundance often chloroplast proteins and protein complexes in the marine haptophyte, Isochrysis galbana Green, grown at nine steady‐state dilution rates in nitrogen‐limited chemostats. The proteins included Photosystem I reaction center (RCI) chlorophyll protein, CP1; Photosystem II reaction center (RC II) protein, D1; two chlorophyll a‐binding apoproteins, CP 43 and CP 47; 33 KDa oxygen evolving protein, OEC 33; α subunit of coupling factor, CF1α; large (LSU) and small subunits (SSU) of ribulose 1,5‐bisphosphate carboxylase, RuBisCO; the chlorophyll a/c/fucoxanthin protein complex, LHCP; and cytochrome b6/f. Seven of the ten protein complexes are encoded in the chloroplast, two are encoded in the nucleus and one shares chloroplast and nuclear genomes. Over the range of dilution rates (0.96‐0.18 d−1) cell N decreased 42% and cellular chlorophyll a decreased 50%; however, the stoichiometric proportion of RC II: cytochrome b6/f: RC I remained constant, averaging 1:3.3:0.8. In contrast, RuBisCO / PS II decreased by 58%. The light harvesting chlorophyll a/c/fucoxanthin protein complex increased relative to RC II; however, as cells became more nitrogen limited the fraction of total cell nitrogen contained in RuBisCO decreased from 21.3 to 6.7%, whereas that of the light harvesting complex remained relatively constant, averaging 6.8%. Our results generally support the hypothesis that in nitrogen limited cells, proteins encoded in the nuclear genome are synthesized preferentially over those encoded in the chloroplast.
SURVIVAL OF SCENEDESMUS ACUMINATUS (CHLOROPHYCEAE) IN DARKNESS1
Authors: Dehning Irmtraut , Tilzer Max M. 
Published: November 2006

ABSTRACTSurvival of the green alga Scenedesmus acuminatus Lagerh. in complete darkness was studied in axenic batch cultures at 7°C and 22°C for three months. The decrease in cell numbers was insensitive to temperature and slower than the loss of dry weight. However, the lag phase before cells began to lyse was more than twice as long at 7° C than at 22°C. The decline in cellular carbohydrates and proteins occurred in two phases. During the first 3‐4 days, the decrease in cellular carbohydrate levels was significantly accelerated and temperature‐sensitive. Pyrenoids disappeared within 5 days of darkness. Proteins showed 20‐fold higher degradation rates at 22°C than at 7°C during the first 4 days. Thereafter, the rates of carbohydrate and protein decomposition were slow and temperature‐independent. By contrast, lipids degraded only little at virtually constant and temperature‐insensitive rates over the entire experimental period.After three months of dark incubation, about 40% of the remaining cells had retained their growth potential. However, the lag phase, after which cell division was resumed when exposed to light, increased with the duration of the previous dark period. The decrease in photo synthetic potential, which was more pronounced at 22° C than at 7° C, was apparent both in declining maximum assimilation numbers and maximum quantum yields. Cellular chlorophyll a concentrations in surviving cells decreased only slightly.We conclude that the primary means by which S. acuminatus survives extended dark periods is by reduction of catabolic reactions. This was suggested by the slow loss of cell weight. No evidence of significant heterotrophic acetate uptake was found. The initial temperature‐dependence of most observed processes indicates that in natural environments chances for survival of algae are augmented by the prevailing low water temperatures.
TRANSIENT PHOTOSYNTHETIC RESPONSES OF NITROGEN‐DEPRIVED PETALONIA FASCIA AND LAMINARIA SACCHARINA (PHAEOPHYTA) TO AMMONIUM RESUPPLY1
Authors: Williams Susan L. , Herbert Stephen K. 
Published: November 2006

ABSTRACTPetalonia fascia (Müller) Küntze and Laminaria saccharina (L.) Lamouroux cultured in N‐free medium exhibited transient depressions in light‐limited and light‐saturated gross O2 evolution within 0.3 h following ammonium resupply. Recovery of photosynthesis to pre‐resupply rates required 24 h. After 6‐9 d of ammonium resupply, photo synthetic rates of N‐deprived algae were similar to those of control plants grown with nitrogen. This study demonstrates that N‐deprived macroalgae exhibit suppressed photosynthesis upon nitrogen resupply similar to many microalgal species. The apparent slowness of short‐term recovery from nitrogen‐elicited photo synthetic suppression may have ecological consequences for macroalgae under conditions of patchy nutrient supply.
BIOMINERALIZATION OF THE STALKS OF ANTHOPHYSA VEGETANS (CHRYSOPHYCEAE)1
Authors: Lee Robert Edward , Kugrens Paul 
Published: November 2006

ABSTRACTMineralized stalks of the chryophyte Anthophysa ve‐getans (O. F. Müller) Stein were examined by electron microscopy, and the composition of the stalks was determined by energy dispersive x‐ray microanalysis. Colonies grown in water from a local lake (Dowdy Lake) had mineralized stalks that were colorless and composed mainly of spherules of calcium phosphate up to 0.7 μm in diameter. The addition of 0.1 mM MnCl2 to the culture medium resulted in deeply orange‐brown stalks mineralized primarily with minute granules of a manganese compound. The addition of 0.1 mM FeCl3 to the culture media resulted in light yellow stalks mineralized mainly with small granules of an iron compound. The addition of 0.1 mM MgCl2 or KCl resulted in stalks that were similar in appearance and composition to the colonies grown in culture medium alone. These results show that the composition of the mineralized stalks of A. vegetans is dependent on the elements present in the culture medium. This is also the first time that calcium phosphate has been reported as a mineralization product in the chrysophytes.
EVIDENCE FOR SEXUAL REPRODUCTION IN THE PRIMITIVE GREEN ALGA NEPHROSELMIS OLIVACEA (PRASINOPHYCEAE)1
Authors: Suda Shoichiro , Watanabe Makoto M. , Inouye Isao 
Published: November 2006

ABSTRACTEvidence for a specialized sexual process in Nephroselmis olivacea Stein is presented. This alga is a member of the Prasinophyceae, which is regarded by some as the most primitive Class of green plants. N. olivacea has a heterothallic type of mating system. Plus and minus gametes were morphologically similar but showed different behaviors during the mating process. The minus gamete settled to the substratum, attaching by its ventral side. The plus gamete attached to the dorsal side of the minus gamete by the region near the flagellar bases of the plus gamete. The mature zygotes were spherical and strongly adhered to the substratum. After zygote germination, two biflagellate daughter cells, each with two pyrenoids were liberated. These cells divided, resulting in four vegetative cells, each with a single pyrenoid.