bluuebunny/crossref_metadata_2025_split huggingface dataset:
USE OF METHYLAMMONIUM AS AN AMMONIUM ANALOGUE IN NITROGEN TRANSPORT AND ASSIMILATION STUDIES WITHCYCLOTELLA CRYPTICA(BACILLARIOPHYCEAE)1
Authors: Wheeler Patricia A. 
Published: August 2007

ABSTRACTThe effect of methylammonium on the utilization of other nitrogen sources and the characteristics of methylammonium uptake byCyclotella crypticaReimann, Lewin, and Guillard were examined. Methylammonium prevented growth on nitrate, nitrite, and arginine, but did not affect growth on ammonium or glutamine. Methylammonium was taken up rapidly by what appears to be an ammonium transport system. Transport followed saturable kinetics, was specific for ammonium and methylammonium, and appeared to be subject to nitrogen regulation. Transport rates were hyperbolically related to external Na+and strongly inhibited by high external concentrations of K+. These results support the use of methylammonium as an ammonium analogue, as an inhibitor of the utilization of some forms of nitrogen, and in the analysis of the mechanism and regulation of ammonium transport.
BROMOPEROXIDASES AND HALOGENATED LIPIDS IN MARINE ALGAE1
Authors: Hewson William D. , Hager Lowell P. 
Published: August 2007

ABSTRACTUsing the facilities of the RIV Alpha Helix, marine algae were collected and immediately sampled for the presence of peroxidase enzymes capable of performing electrophilic bromination via the oxidation of bromide ion. Algae were also sampled for halogenated neutral lipids. A spectrophotometric assay employing monochlorodimedone was used to measure the level of enzymatic bromination, and an automated halogen analyzer was used to determine the level of lipid halogen. Of 72 algae tested for bromoperoxidase, 55 were active; moreover 27 of 102 algae contained significant levels of lipid halogen. For 67 algae there was sufficient sample to complete both assays. A comparison of the reds, browns and greens showed the Rhodophyta to be the richest in both bromoperoxidase and lipid halogen levels while the Phaeophyta was the poorest. pH optima in the range pH 5 to 8 were determined for a few of the more active algal bromoperoxidases. Cyanide inhibited the bromination of monochlorodimedone but inhibition could not be distinguished from the possibility of competition by cyanide for electrophilic bromination.
GROWTH OF A COCCOID NANOPLANKTER (EUSTIGMATOPHYCEAE) FROM THE CHESAPEAKE BAY AS INFLUENCED BY LIGHT, TEMPERATURE, SALINITY AND NITROGEN SOURCE IN FACTORIAL COMBINATION1
Authors: Terlizzi Daniel E. , Karlander Edward P. 
Published: August 2007

ABSTRACTDivision rates of Nannochloris oculata Droop (Chesapeake Bay clone) were recorded in semicontinuous cultures grown at 81 combinations of light intensity, temperature, salinity and nitrogen source. A maximal growth rate of 2.1 doublings 1 day occurred at 30 C, 15‰ salinity with a light intensity of 11,300 lux (1.350 mW/cm2) using ammonium or urea as nitrogen sources. Several generalizations about the autecology of this organism result: (1) salinity optima were between 5–15‰ in all instances. (2) the lack of growth at 10 C and the universal improvement in growth with temperature elevation to 30 C indicates a rather high temperature optimum. (3) there is a trend of decreasing light optimum with temperature decreases below the optimum.The source of nitrogen providing the best growth was shown to be dependent on light, temperature, salinity and interactions among these variables. For nitrate and ammonium cultures, temperature had the greatest influence on growth rate, followed by light and then salinity. For urea cultures, the order was temperature, salinity, then light. Interactions of all combinations of variables were significant with the temperature‐salinity‐light interaction most pronounced with urea cultures. Demonstration of interactions among environmental variables and nitrogen nutrition suggests that some conclusions based on surveys employing fixed variables alone may be unreliable.
31P‐NMR DIFFERENTIATION BETWEEN INTRACELLULAR PHOSPHATE POOLS IN COSMARIUM (CHLOROPHYTA)1
Authors: Elgavish A. , Elgavish G. A. 
Published: August 2007

ABSTRACT 31P nuclear magnetic resonance (NMR) spectroscopy of intact Cosmarium sp. cells is presented as a suitable tool for the differentiation of intracellular accumulation pools of polyphosphates.The cold trichloroacetic acid (TCA) insoluble fraction is shown to contain most of the total cellular phosphate in the phosphate rich Cosmarium cells. Moreover, evidence from a 31 P‐NMR study and electron microscopic observations of cold TCA treated Cosmarium cells indicate that this fraction consists mostly of polyphosphates which seem to retain the native morphological structure observed in the untreated cells. The determination of orthophosphate in the hot water extract of Cosmarium cells did not measure the polyphosphate pools. Determination of total phosphorus content in the hot water extract rendered a value three times higher than the frequently used orthophosphate determination procedure. However, as revealed by the 31P‐NMR spectra and the chemical analyses of the extract and of the treated cells, even total phosphorus in the extract measured only 30% of the total cellular phosphorus. 31P‐NMR enabled the unequivocal chemical identification of the major phosphate compounds in the hot water extract (“Surplus P”) as orthophosphate and polyphosphates of about 10 phosphate units chainlength. More than 70% of the accumulation pool of polyphosphates was still in the cells after extraction. However, the electron microscopy study revealed that the native granular structure of polyphosphates had been destroyed by the hot water extraction procedure.
INFLUENCE OF ENVIRONMENTAL FACTORS AND POPULATION COMPOSITION ON THE TIMING OF CELL DIVISION IN THALASSIOSIRA FLUVIATILIS (BACILLARIOPHYCEAE) GROWN ON LIGHT/DARK CYCLES1
Authors: Chisholm Sallie W. , Costello John C. 
Published: August 2007

ABSTRACTCell division patterns in Thalassiosira fluviatilis grown in a cyclostat were analyzed as a function of temperature, photoperiod, nutrient limitation and average cell size of the population. Typical cell division patterns in populations doubling more than once per day had multiple peaks in division rate each day, with the lowest rates always being greater than zero. Division bursts occurred in both light and dark periods with relative intensities depending on growth conditions. Multiple peaks in division rate were also found, when population growth rates were reduced to less than one doubling per day by lowering temperature, nutrients, or photoperiod and the degree of division phasing was not enhanced. Temperature and nutrient limitation shifted the timing of the major division burst relative to the light/dark cycle.Average cell volume of the inoculum was found to be a significant determinant of the average population growth rate and the timing and magnitude of the peaks in division rate. The results are interpreted in the context of a cell cycle model in which generation times are “quantized” into values separated by a constant time interval.
GROWTH‐INHIBITORS AND GROWTH‐PROMOTERS IN ENTEROMORPHA COMPRESS A (CHLOROPHYTA)1
Authors: Niemann Dorothea I. , Dörffling Karl 
Published: August 2007

ABSTRACTMethanol extracts from the alga Enteromorpha compressa (L.) Grev. contain substances which inhibit the elongation of Lepidium roots. Chromatographic separation of the inhibiting substances revealed that one of the inhibitory zones of the chromatograms had properties of the so‐called inhibitor β. Neither abscisic acid (ABA) nor lunularic acid proved to be responsible for the growth‐inhibiting property of this zone.Moreover, the extracts contain substances which promote the elongation of Avena coleoptile segments. One of these substances could be tentatively identified as indole‐3‐acetic acid by thin‐layer and gas‐liquid chromatography. (In addition to indole‐3‐acetic acid a second growth‐promoting factor with the properties of the so‐called accelerator α could be detected.)
VALVE AND BAND MORPHOLOGY OF SOME FRESHWATER DIATOMS. III. PRE‐ AND POST‐AUXOSPORE FRUSTULES AND THE INITIAL CELL OFMELOSIRA ROESEANA1
Authors: Roemer Stephen C. , Rosowski James R. 
Published: August 2007

ABSTRACTFrustules of a clonal culture ofMelosira roeseanaRabenh. were examined with light and scanning electron microscopy. Vegetative valves in the post‐auxospore (full size) stage exhibit a larger width/length ratio than those in the pre‐auxospore (size‐reduced) stage. Cells form chains by linking spines of adjacent valves which occur at the periphery of the valve face‐mantle junction. Three or jour large pores occur at the center of the valve face, with the diameter of each pore tapering from the inner to the outer valve surface; these pores are often occluded by siliceous processes. Features ofM. roeseana,not shown previously forMelosira,include a “stepped” mantle, on only one of the two valves resulting from the same cell division, flattened processes attached to short siliceous stalks on the valve face, disk‐like processes on the mantle, and an open girdle band with up to eight antiligulae. Siliceous scales on the surface of the initial cell are remnants of the auxospore wall. The epivalve of the initial cell is larger in diameter than the hypovalve, and both valves lack linking spines and a step on the valve surface. The initial, cell epicingulum consists of only two bands; the hypocingulum has up to seven. Initial cells with four or more hypocingular bands divide to form new post‐auxospore filaments.Melosira roeseanashould not be included in the genusMelosiraas it is presently defined by the type species,M. nurnmuloidesC. Ag. Major differences include irregular linking spines, a closed pseudoloculate valve construction, and labiate processes on the valve face and mantle ofM. nummuloides,compared with well‐defined linking spines, a valve constructed of a basal siliceous layer perforated by poroid areolae, and labiate processes lacking on the valve ofM. roeseana.
DISTRIBUTION AND SALINITY ADAPTATIONS OF BANGIA ATROPURPUREA (RHODOPHYTA), A PUTATIVE MIGRANT INTO THE LAURENTIAN GREAT LAKES1
Authors: Sheath Robert G. , Cole Kathleen M. 
Published: August 2007

ABSTRACTIn a survey of the distribution of Bangia atropurpurea (Roth) Ag. along the north and east shorelines of the Laurentian Great Lakes, it was observed that this species was concentrated in the lower lakes. Asexual reproduction by monospore formation was the only form of reproduction in these populations. First generation germlings derived from these spores grew in a wide range of salinities from 1 to 26‰, but the rate was inversely proportional to salinity. In addition, acclimation of parent plants to freshwater or marine media prior to sporulation affected growth rates of first generation germlings placed into a series of salinities. By the second and third generation, germlings with a lineage of seawater showed a preference for the higher salinities, 19 and 26‰ Plants collected in Lake Ontario exhibited no decline in photosynthetic rate as salinity was raised by 13‰ for 15 min. At 26‰ the rate was reduced by half and thylakoids were disrupted in the region of the pyrenoid. On the other hand, third generation plants with a history of seawater attained maximum photosynthetic rates at 26‰ and contained a normal thylakoid organization. Three chromosomes were observed in these plants, which agrees with some of the previous findings for marine Bangia. Origins and taxonomic status of Bangia growing In the Great Lakes are discussed in light of these findings.
POPULATION GENETICS OF SKELETONEMA COSTATUM (BACILLARIOPHYCEAE) IN NARRAGANSETT BAY1
Authors: Gallagher Jane C. 
Published: August 2007

ABSTRACTDuring a two year period 457 clones of the diatom Skeletonema costatum were isolated prior to and during the summer‐fall and winter‐spring blooms of this species in Narragansett Bay, R.I. Their allozyme banding patterns were examined for 5 enzyme loci. Genotypic frequencies indicated that the winter bloom populations were genetically different from the prevalent summer bloom populations of the same species. Genetic differences between seasonal blooms are as great as those found between species of terrestrial organisms, but are not accompanied by morphological variation. Although blooms have distinct prevalent forms, they are not genetically homogeneous. No single clone is ever representative of all populations of S. costatum. The dynamics of these allochronic populations appear to be governed by a form of cyclic natural selection, and are probably a regular feature of the cycles of abundance of this species in this area. These results cast doubt on some of the assumptions often made in the “autecological approach” to phytoplankton ecology. This study comprises the first quantitative examination of the population genetics of a microalga.
THE RELEASE OF GLYCOLATE BY A FRESHWATER DIATOM1
Authors: Colman Brian , Hosein Myda L. 
Published: August 2007

ABSTRACT Navicula pelliculosa (Breb) Hilse grown on 2% CO2 in air released glycolate when incubated in light in buffer pH 8.0 containing 10 mM bicarbonate. Excretion ceased about 90 min after transfer to air and no excretion was detected with air‐grown cells. These results indicate that glycolate release in this alga, as in species of other algal phyla, is an artifact of growth on high concentrations of CO2.
OPTIMUM N:P RATIOS AND COEXISTENCE OF PLANKTONIC ALGAE1
Authors: Rhee G‐Yull , Gotham Ivan J. 
Published: August 2007

ABSTRACTThe optimum atomic ratio of N to P, the ratio at which one nutrient limitation changes over to the other, was determined in seven species of freshwater planktonic algae. The ratio varied over a wide range among species; the average for these species was 17. If the cellular nutrient ratios in marine species are comparable with those in freshwater organisms, Redfield's ratio of 15 is remarkably close to the average. Cellular N:P ratios varied over a 24‐h period under a light:dark cycle. The variation of the optimum ratio between species and diel change in cellular N:P ratios within a species could play an important role in population dynamics by enhancing the probability of coexistence of species.
TRACHELOMONAS HISPIDA VAR. CORONATA (EUGLENOPHYCEAE), II. ENVELOPE SUBSTRUCTURE1,2
Authors: West Larry K. , Walne Patricia L. 
Published: August 2007

ABSTRACTEnvelopes of the mineralizing protist, Trachelomonas hispida var. coronata Lemm., were examined by light and electron microscopy and by electron diffraction analysis. The ellipsoidal hollow envelope is made of mineralized strands of mucilage (muci‐strands) that form a compact wall 0.2–4.0 μm thick, interspersed with numerous puncta 0.2–0.3 μm in diameter and, in some instances with tapered spines ca. 0.6 μm long and 0.7 μm wide at the base. The mucilage strands are cylindrical, anastomosing threads 20 nm thick. Electron‐dense, needle‐shaped mineral deposits form axial cores in the strands. Also, powdery granular mineral deposits are dispersed sparingly throughout the mucilage matrix. Micromicro‐electron diffraction analyses verify the crystalline nature of the needle‐shaped deposits, which are 4–9 nm thick and vary in length (20–100 nm). The mucilage strands and microcrystallites pervade the whole of the envelope matrix, including the spines, and may be preferentially oriented along the envelope surfaces.
EFFECT OF NITROGEN SUPPLY ON NITROGEN CONTENT AND GROWTH RATE OF JUVENILE MACROCYSTIS PYRIFERA (PHAEOPHYTA) SPOROPHYTES1
Authors: Wheeler Patricia A. , North Wheeler J. 
Published: August 2007

ABSTRACTThe effect of nitrogen supply on nitrogen content and growth rate of juvenile Macrocystis pyrifera (L.) C. A. Agardh sporophytes was studied in two types of experiments: growth in continuously flowing mixtures of deep (nutrient‐rich) and surface (nutrient‐poor) seawater, and growth in batch cultures with alternate 7–10 day periods in deep and surface water. In the continuous flow experiments, the nitrogen content of the plants increased with the increased concentration of nitrate in the seawater. In the batch culture experiments, a lag period of 3–7 days often occurred before changes in the nitrogen supply were reflected in corresponding changes in the nitrogen content of the plants. Growth rates were a linear function of tissue nitrogen which varied between 1–3% dry weight. Saturation of growth rate as a function of tissue nitrogen did not occur, although tissue nitrogen levels did saturate as a function of external nitrate supply. Juvenile M. pyrifera sporophytes do not appear to “store” nitrogen. Total nitrogen varies from 1–6% dry weight in Laminariales and Fucales, but only some species of Laminaria appear to accumulate large pools of “surplus” nitrogen.
TRACHELOMONAS HISPIDA VAR. CORONATA (EUGLENOPHYCEAE). III. ENVELOPE ELEMENTAL COMPOSITION AND MINERALIZATION1,2
Authors: West Larry K. , Walne Patricia L. , Bentley James 
Published: August 2007

ABSTRACTThis report is the first direct demonstration of Mn deposition in envelopes (loricas) of Trachelomonas in culture. The envelopes of Trachelomonas hispida var. coronata Lemm. were analyzed for elemental composition by X‐ray fluorescence spectrometry (XRF), atomic absorption spectrophotometry (AA), and electron microscopic, energy‐dispersive X‐ray spectroscopy (EM‐EDS). The envelopes contained extensive deposits of manganese (20–60 wt. %) and lesser amounts of Si, Ca and either Ba or Ti, the last three together totalling less than 5% by weight. The average amount of Mn per envelope was estimated at 1.5 × 10−10 g. Traces of Na, K, P, S and Cl were also detectable. Biomineralization of envelopes was studied by comparison of envelope substructure and composition in lightly colored, golden and dark brown envelopes that were isolated by micromanipulation, processed individually or in groups, and analyzed by SEM, TEM, EM‐EDS, and scanning transmission EM‐EDS (STEM‐EDS). Dark envelopes were thicker (1–4 μm), more ornate and less porous than light envelopes, but the ultrastructure of the two was similar. In both types of envelopes, distribution and thickness of Mn‐containing fibrillar to needle‐like microcrystallites were similar. However, dark envelopes contained a greater density of granular deposits around the needle‐like microcrystallites than did light envelopes. Dark envelopes contained 2–40 times more Mn than did light envelopes, but since envelope mass is proportionately greater, Mn concentrations were similar. Our results suggest that the extent of mineralization depends upon the amount of mucilage secreted. Biomineralization studies with Trachelomonas offer the rare advantage that mineral deposition occurs extracellularly, and not within membrane‐bound compartments as in many other unicellular model systems.
STRUCTURE AND COMPOSITION OF PITHOPHORA OEDOGONIA (CHLOROPHYTA) CELL WALLS1
Authors: Pearlmutter Nina L. , Lembi Carole A. 
Published: August 2007

ABSTRACTCarbohydrates, amino acids and other cell wall components of Pithophora oedogonia (Montagne) Wittrock were identified by physical, biochemical, and cytochemical techniques as well as by light and electron microscopy. The major polysaccharides of P. oedogonia cell walls were cellulose and chitin. In addition to N‐acetylglucosamine and glucose, N‐acetylgalactosamine, galactose, arabinose, fucose, mannose, xylose, and galacturonic acid were the other sugars, amino sugars, and sugar derivatives detected. The carbohydrate content of the cell walls was estimated to be 65% non‐nitrogenous hexose and 6% chitin. Chitin was present in the crosswall disks and outer wall, whereas cellulose was confined to the inner wall. Protein and N‐ acetylgalactosamine were concentrated in the chitin‐rich wall fraction. The location of chitin in P. oedogonia cell walk is suggested as a basis for morphological differences between the two genera, Cladophora and Pithophora.
VERTICAL DISTRIBUTION OF SEAWEED SPORES IN A WATER COLUMN OFFSHORE OF NORTH CAROLINA1
Authors: Amsler Charles D. , Searles Richard B. 
Published: August 2007

ABSTRACTDifferences in the vertical distribution of seaweed spores in a 20 m water column 30 km off the coast of North Carolina were documented. Spores were collected on plastic, and glass slides that were subsequently transferred to incubator cultures where germlings were grown and counted. Spores of green algae and bangiophycidean red algae were collected throughout the water column, whereas spores of brown algae and florideophycidean red algae occurred almost exclusively near the bottom. The occurrence of some kinds of spores in the upper water levels suggests relatively large dispersal shadows for those species. The taxa recovered in the upper levels were typically opportunistic organisms, many of them epiphytes. The collection of many Enteromorpha individuals in the upper and mid levels was of particular interest since locally this genus only occurs in abundance in shallow water habitats 35 km or more from the study site.
PHOTOSYNTHESIS OF THE RED ALGA GASTROCLONIUM COULTERI (RHODOPHYTA) IN RESPONSE TO CHANGES IN TEMPERATURE, LIGHT INTENSITY, AND DESICCATION1
Authors: Hodgson Lynn M. 
Published: August 2007

ABSTRACTPreviously reported transplantation experiments in the field showed that Gastroclonium coulteri (Harvey) Kylin could survive above its normal intertidal range (0.0–0.5 m above MLLW), except during periods of daytime low tides in spring. Net photosynthetic rate measurements in the laboratory were performed to determine which physical factors might determine the upper boundary for this species in the intertidal zone.Maximum net photosynthesis occurred between 15 and 20° C, but remained positive between 4 and 35° C. The air temperature extremes observed in the field were 2° C (only seen once) and 26° C. Net photosynthesis increased as expected with light intensity to the highest value obtainable in the laboratory, 1400 μEin m−2 s−1. Plants collected from the field under higher light intensity (up to 2000 μEin m−2 s−2) also showed high rates of photosynthesis. Neither the temperature nor light levels observed in the field were directly damaging to photosynthesis. Desiccation, however, resulted in a sharp decrease in both photosynthesis and respiration. G. coulteri fully recovered from successive daily treatments of about 35% desiccation, but not from successive treatments of 50% desiccation. One exposure to 70% desiccation allowed no recovery of photosynthetic capacity.
THE EFFECTS OF LIGHT AND NITROGEN ON GROWTH, PIGMENT CONTENT, AND BIOCHEMICAL COMPOSITION OF GRACILARIA FOLIIFERA V. ANGUSTISSIMA (GIGARTINALES, RHODOPHYTA)1
Authors: Lapointe Brian E. 
Published: August 2007

ABSTRACTThe combined effects of light intensity and nitrogen (NO3−) on growth rate, pigment content, and biochemical composition of Gracilaria foliifera v. angustissima (Harvey) Taylor was investigated using outdoor continuous cultures.Growth of Gracilaria increased linearly with increasing light to 0.43 doublings d−1 at high light levels (383 ly d−1 of in situ light), suggesting that light may often limit growth of this plant in nature. Chlorophyll a and phycoerythrin contents were inversely proportional to light level and growth rate. However, pigment content did not affect the growth capacity of Gracilaria. There was no increase in growth or pigment content with increasing additions of nitrogen. The low nitrogen treatment was unenriched seawater that had higher NO3− levels than most coastal waters (influent = 8.61 μM; residual = 0.94 μM). When growing near its maximum rate under high light intensities, Gracilaria had a significantly (P < 0.001) lower phycoerythrin: chlorophyll a ratio (phyco: Chl a) than did Gracilaria growing more slowly under lower light (Phyco:Chl a of 2.8 ± 0.2 vs. 3.8 ± 0.3). Faster growing plants also had C:N ratios above 10, indicating N‐ limitation. In addition to harvesting light the phycobiliproteins of Gracilaria may store nitrogen.Growth rates of Gracilaria correlated negatively with ash (r =–0.85) and positively with the carbon: phycoerythrin ratio (r = 0.85), suggesting that these two indices can be used to estimate growth in the field.