bluuebunny/crossref_metadata_2025_split huggingface dataset:
ELECTRICAL IMPEDANCE IN ASCOPHYLLUM NODOSUM AND FUCUS VESTCULOSUS IN RELATION TO COOLING, FREEZING, AND DESICCATION1
Authors: MacDonald Marilyn A. , Fensom D. S. , Taylor A. R. A. 
Published: August 2007

SUMMARYElectrical impedance monitoring techniques appear to be useful in tracing the effect of cooling or desiccation upon the thallus of Fucus vesiculosus and Ascophyllum nodosum.These algae were found to be remarkably resistant to injury from freezing down to −20 C even during midsummer and from desiccation up to 70% water loss, and in these properties were markedly different from land plants.Freezing point depressions, the degree of supercooling, activation energies of cooling‐impedance curves, and the slope of these curves themselves were useful in disclosing differences between time of sampling, storage time, and indications of damage in tissue. No significant difference could be detected between the 2 species collected and tested at the same time. Significant differences occurred in F. vesiculosus between summer and winter, and in winter between submersed and intermittently exposed plants. Tracer ion uptake techniques confirmed that freezing to −20 C did not kill tissues.
PHOSPHATE UPTAKE UNDER NITRATE LIMITATION BY SCENEDESMUS SP. AND ITS ECOLOGICAL IMPLICATIONS1
Authors: Rhee G‐Yull 
Published: August 2007

SUMMARYUnder nitrogen limitation the phosphate content of Scenedesmus sp. shows little variation regardless of growth rate and the N/P atomic ratio of the medium. P uptake therefore can be calculated as the product of P content and N‐dependent growth rate. The maximum rate of P uptake in N limitation is lower by a factor of about 8 than the rate in P limitation.As reported earlier, P uptake by this alga under P limitation is described by the kinetics resembling non‐competitive enzyme inhibition, with one or several intracellular P fractions as inhibitors. These fractions include surplus P (water extractable) and inorganic polyphosphate fractions A (acid soluble) and B, C, and D (acid insoluble). In N limitation, the ratios of fractions A, B, C, and D are quite different from the ratios of P limitation at comparable growth rates. The concentrations of polyphosphate fraction A in N‐limited cells are much, higher than the levels in P‐limited cells, and this fraction becomes more predominant at low growth rates in N limitation. This fraction, if introduced as the inhibitor into the noncompetitive scheme, explains the uptake kinetics in both N‐ and P‐limited cells and the low maximum uptake rate in N limitation.This finding may have two significant ecological implications: (1) A nutrient imbalance which brings about changes in the internal, level or the metabolism, of fraction A would affect P uptake. (2) Nitrogen sufficiency would cause a competitive advantage in P uptake. This advantage would be shared by N2 fixers and algae with low optimum N/P ratios.In Scenedesmus sp. P limitation switches to N limitation and vice versa when the cell N/P atomic ratio is about 30.
MODIFICATION OF PHYTOPLANKTON GROWTH BY EXCRETED COMPOUNDS IN LOW‐DENSITY POPULATIONS1
Authors: Huntsman Susan A. , Barber Richard T. 
Published: August 2007

SUMMARYConditioned seawater, removed by filtration from an exponentially growing mixed phytoplankton population, inhibited the growth of a small inoculum of cells from the same source without reducing the lag period. When the 2 populations, one in exponential growth and the other freshly inoculated, were separated by a filter membrane allowing passage of excreted compounds, the growth rate of the freshly inoculated cells was again depressed but the lag phase was reduced almost as effectively as by the addition of the chelator, EDTA. Thus both inhibitory and stimulatory compounds appear to be excreted by the cells during exponential growth, the stimulatory group, apparently involved with trace metal metabolism, being more labile to degradation.A test was made to determine if the population could be induced to utilize unconditioned water. Even after repeated transfers there was no reduction in the lag period, indicating that the initiation of exponential growth represents a response to excreted conditioning agents (possibly chelating compounds) rather than an adjustment by the population to use unconditioned water.
ADAPTATION OF THE UNICELLULAR ALGA DUNALIELLA PARVA TO A SALINE ENVIRONMENT1
Authors: Ben‐Amotz Ami 
Published: August 2007

SUMMARYThe holophilic alga Dunaliella parva produces glycerol as a major product of photosynthetic 14CO2 incorporation and accumulates very large amounts of intracellular glycerol. A method was adopted for the determination of the cell water space based on the distribution of 14C sorbitol and 3H2O between the cells and the medium. Using these measurements the internal concentration of glycerol was found to be isoomotic with that of the medium over a broad range of 0.6 to 2.1 m NaCl. When the extracellular salt concentration of an algal suspension was increased or decreased, the intracellular water content immediately varied so as to keep an osmotic equilibrium between the cells and the medium. During the following 90 min under metabolic conditions, glycerol content changed until a new level was reached. Since no leakage of intracellular glycerol was observed above 0.6 m NaCl, these alterations in glycerol content are interpreted as due to metabolic formation and degradation of intracellular glycerol. Determination of the glycerol sensitivity of enzymic and photosynthetic reactions of cell‐free preparations from D. parva showed a broad range of tolerance to high concentrations of glycerol.These results indicate that osmoregulation in Dunaliella depends on the synthesis or degradation of intracellular glycerol in response to the external salt concentration. A proposed scheme of glycerol synthesis in Dunaliella is suggested.
THE CORRELATION OF GOLGI ACTIVITY AND POLYSACCHARIDE SECRETION IN PORPHYRIDIUM12
Authors: Ramus J. , Robins D. M. 
Published: August 2007

SUMMARYQuantitative morphometric measurements were made of the area occupied by the Golgi complex in log and stationary phase cells. The technique involved the cutting out and weighing of cellular compartments from electron micrographs of median cell sections. Data from the morphometric measurements combined with physiological measurements of secretory activity yielded a simple model for the involvement of the Golgi complex in the biogenesis of cell surface polysaccharides. Golgi were larger and more numerous in log phase, perhaps indicating a higher rate of polysaccharide synthesis than in stationary phase. In log phase, polysaccharide‐containing vesicles accumulate adjacent to the cell membrane. In stationary phase, the polysaccharide is secreted to the cell surface by exocytosis, giving rise to a capsule. Thus the shift from log to stationary phase results in structural and functional cellular differentiation, eg, from a thin to a thick capsule. The ecological implications of capsule formation are discussed.
TRANSFORMATION OF NONPOLAR FILAMENTS OF THE BLUE‐GREEN ALGA GLOEOTRICHIA ECHINULATA U. WISC. 1052 INTO DOUBLE HELICES12
Authors: Lange Willy 
Published: August 2007

SUMMARYNormally straight filaments of Gloeotrichia echinulata U. Wisc. 1052 transform into double helices when a critical culture density has been attained. In inorganic Zehnder‐Gorham's medium No. 11, the alga initially is morphologically uniform and forms single, lightly curved, polar filaments. When a stage of close proximity of the filaments is reached, excessively long filaments are observed that are nonpolar. Some of these nonpolar filaments form helices. Two independent single helices may entwine to form a double helix. Double helices also form when both ends of an excessively long filament meet and start entwining until a loop is left at about the original middle of the filament. In another manner of double‐helix formation, a straight filament makes a hairpin bend at about its middle; then 2 helices form starting at the bend and they entwine into a double helix, leaving a loop at the location of the original bend. Under proper culture conditions, the structures of double helices show an amazing regularity. Once double‐helix formation has started, some strong force brings the process to completion. In a mature culture, helices disintegrate into apparently healthy, short pieces of filaments or single cells, while the straight or slightly curved polar filaments still persist. Helical transformation of nonpolar filaments does not appear to be a sign of nutritional or other stress but rather appears to serve a specific purpose. One might speculate that a genetic exchange between opposite cells takes place.
DEVELOPMENT AND GERMINATION OF AKINETES OF APHANIZOMENON FLOS‐AQUAE1
Authors: Wildman Ruth B. , Loescher Judith H. , Carol L. Winger 
Published: August 2007

SUMMARYFlakes of Aphanizomenon flos‐aquae collected from an ice‐covered lake were found to contain all developmental stages from vegetative cells to mature akinetes. Changes during development include increase in cell size, gradual disappearance of gas vacuoles (clusters of gas vesicles), narrowing of intrathylakoidal spaces, and increase in cytoplasmic density. Development of akinetes is accompanied by proliferation of ribosomes, including polyribosomes, cyanophycin granules (structured, granules), and glycogen granules. The lipid bodies of vegetative cells are reduced in size and number in mature akinetes. Akinetes may occur singly or as multiples in sequence in a filament, either terminal or intercalary. Loss of flotation by increase in cytoplasmic density permits filaments to sink and overwinter in bottom sediments. The sequence was found to be reversed during germination of akinetes. Cyanophycin granules are reduced in size and staining density in the sporelings, and very few glycogen granules are seen. Gas vesicles reappear and increase in number, and intrathylakoidal spaces become wider. These changes then would permit the sporelings to rise from the bottom and begin another season's bloom.
ULTRASTRUCTURE OF THE RESERVOIR AND FLAGELLA IN PHACUS PLEURONECTES (EUGLENOPHYCEAE)1
Authors: Dynesius Roselynn A. , Walne Patricia L. 
Published: August 2007

SUMMARYThe ultrastructure of the reservoir region of Phacus pleuronectes is described. Thin sections, ruthenium red staining, and shadow‐cast preparations elucidate relationships and structural details of the flagella and flagellar hairs or mastigonemes. A heretofore undescribed structure in Phacus, the multitubular structure (MTS), with associated fibrillar projections, is reported. The MTS is located in the cytoplasm at the distal region of the reservoir near the contractile vacuole. A coordinated function of the MTS and adjacent fibrillar projections is suggested. The occurrence of mastigonemes along the entire length of the emergent flagellum is suggested, in contrast to earlier reports of their presence only on that portion of the flagellum distal to the cytostome. The present investigation postulates also that the mastigonemes are bipartite, the thicker fibrous bases becoming modified distally into the classically described, mastigonemes.
ISOLATION OF NITROSOGUANIDINE‐INDUCED CHLORELLA VULGARIS MUTANTS WITH HIGH METHIONINE CONTENT1
Authors: Cacco Giovanni , Ferrari Giovanni 
Published: August 2007

SUMMARYMutants of Chlorella vulgaris induced by N‐methyl‐N′‐nitro‐N‐nitrosoguanidine (NG), and, selected for the resistance to either ethionine or 6‐methylpurine, were tested for the relative rate of incorporation into protein of 3H‐methionine and 14C‐leucine. A highly significant, correlation between the 3H‐to‐14C ratio in the protein and its methionine content was found. 6‐Methylpurine proved to be more effective than ethionine as a screening agent for high methionine strains. Screening for 6‐methylpurine resistance, followed by a second screening for the highest methionine‐to‐leucine incorporation ratio, led to isolation of the mutants with a content up to 45% higher in methionine and up to 3 times higher in cysteine with respect to the wild strain.
THE ULTRASTRUCTURE OFSCENEDESMUS(CHLOROPHYCEAE). I. SPECIES WITH THE “RETICULATE” OR “WARTY” TYPE OF ORNAMENTAL LAYER1
Authors: Staehelin L. Andrew , Pickett‐Heaps Jeremy D. 
Published: August 2007

SUMMARYThe ultrastructure of the wall layers and ornamentative features ofScenedesmus pannonicusandS. longusare described using carefully correlated freeze‐etched replicas, thin sections and scanning electron micrographs. The two species arc enclosed by different types of ornamented layers,S. pannonicusby the tightly filling, “warty” layer andS. longusby the loosely fitting, “reticulate” layer, held off the coenobium by 2 types of tubular propping spikelets and rosettes. The reticulate layer has an intricate substructure, especially when studied with freeze‐etching. Its inner and outer surfaces appear different, as is its attachment to the 2 types of spikelets. Whole cells ofS. longussubjected to acetolysis lack the cellulose wall and cytoplasm, but all other surface features survive, including the Trilaminar Sheath (TLS); this ornamentation cannot be “pectic.” The cellulose wall and ornamentation is unaffected by boiling water alone. Boiling in 6nNaOH removes the surface ornamentation, but the TLS and wall remain; the possibility that these features contain silica is discussed.The terminal spines of both species consist of closely packed spikelets enclosed within a skin of hexagonally‐packed subunits. Similar subunits are seen in the propping spikelets of S. longus, and in the rows or “combs” of laterally fused spikelets ofS. pannonicus.The warty layer ofS. pannonicusis tightly appressed to the TLS except close to where the cells are joined, where it is suspended free. It is composed of a layer of globular subunits, and small indentations form the warts. Single, evenly distributed warts characterize the freely suspended sections of the warty layer, and the layer that encloses young coenobia soon after they have been formed: in contrast, the warts are clumped over the surface of older and larger colonies. Some of the single warts form characteristic double rows, but these latter remain single even on older cells. The surface structure of the warty layer, TLS, and plasmalemma are revealed by the freeze‐etching process.
COMPARATIVE ANATOMY OF CHAROPHYTA: II. THE AXIAL NODAL COMPLEX—AN APPROACH TO THE TAXONOMY OF LAMPROTHAMNIUM12
Authors: Frame Paul , Sawa Takashi 
Published: August 2007

SUMMARYThe present investigation on the axial nodes of 32 taxa belonging to the genera Chara, Lamprothamnium, Nitellopsis, Nitella and Tolypella confirms previous reports that within a given taxonomic group the structure of the main axial nodal complex is highly consistent. Besides the genera Nitella and Tolypella of the tribe Nitelleae, Lamprothamnium of the tribe Chareae is the only genus in which the central cells of the main axial nodal complex subdivide. This anatomical feature of the main axial nodal complex thus clearly separates the genus Lamprothamnium from the other genera of the tribe chareae. In 2 controversial species of the genus Chara, C. hornemannii and C. buckellii, the present study reveals that the central cells of their main axial nodal complexes do not subdivide. The transfer of these two species to the genus Lamprothamnium by Daily (1) may not be appropriate.
A RHIZOPLAST IN CARTERIA RADIOSA (CHLOROPHYCEAE)12
Authors: Lembi Carole A. 
Published: August 2007

SUMMARYA rhizoplast or rhizoplast‐like structure was observed with the electron microscope in Carteria radiosa. The cross‐banded structure extends from the proximal end of each of at least 2 of the basal bodies and extends toward, although does not make contact with, the nucleus. The rhizoplast terminates in a ribosome‐free area composed of fine granules and microfibrils. This is the first ultrastructural verification of a rhizoplast in a volvocalean alga.
D‐LACTATE UTILIZATION BY GONIUM (CHLOROPHYCEAE)1
Authors: Saito Shôichi 
Published: August 2007

SUMMARYAcetate, glucose, pyruvate, and lactate utilization as Carbon sources have been investigated in 3 strains of Gonium multicoccum, 2 of G. octonarium, and 1 of G. quadratum. In all strains, growth was supported with acetate, pyruvate and dl‐lactate in continuous light. These species commonly utilized d‐lactate for growth as a carbon source in the light, but there was no effect in the dark. However, they could not utilize l‐lactate for growth in light or darkness.
SEXUAL REPRODUCTION OF PERIDINUM CINCTUM F. OVOPLANUM (DINOPHYCEAE)1,2
Authors: Pfiester Lois A. 
Published: August 2007

SUMMARYSexual reproduction is induced in the dinoflagelate Peridinium cinctum f. ovoplanum Lindemann when exponentially growing cells are inoculated into nitrogen deficient medium. Small, naked vegetative cells, produced by division of the thecate cells, then act as gametes. The zygote remains motile for 12–13 days during which time it enlarges and the theca which it forms becomes warty. Thirteen to 14 day s following plasmogamy the zygote is nonmotile, the protoplast contracts, a large red oil droplet appears, the wall thickens and becomes chitinized. This hypnozygote germinates within 7–8 weeks at 20 c producing 1 post‐zygotic cell retaining the large red oil droplet. The presence of 4 nuclei in these post‐zygotic cells may be demonstrated by staining them with acetocarmine. Two of these nuclei are smaller than the other two and probably abort. One may infer that meiosis occurs immediately prior to or at the germinartion of the hypnozygote. This post‐zygotic cell divides within 24 h into 2 daughter cells each with a promment red oil droplet. These daughter cells divide after 2–3 days into ordinary vegetative cells.Attempts to induce sexual reproduction by changes in temperature or light and by inoculation of cells into media deficient in a number of basic elements were unsuccessful.
MORPHOLOGICAL VARIATION OFACHNANTHES HAUCKIANA(BACILLARIOPYCEAE) IN THE RIELD1
Authors: Tropper Caroline B. 
Published: August 2007

SUMMARYSamples of 2 populations of the diatom,Achnanthes hauckiana Grun.,collected from Sippewissett Marsh, Massachusetts, were measured. Regression analyses of the measurements were calculated. The length/width ratio of both samples decreased almost linearly with decreasing length. The length/width ratio of the rostrate ends also decreased almost linearly with decreasing length. The number of striae per 10 μm showed a slight tendency to increase with decreasing length. Some of the specimens collected, which fit the descriptions ofA. hauckianavar.ellipticaor ver.rostrata,appear to be morphological variants of the nominate variety. The change in shape with size fits Geitler's rule of proportionally greater decrease in the apical axis than the decrease in the transapical axis.The regression lines of change in shape with size might be used as taxonomic characteristics and contain more information than the usual descriptions of limits of size and shape of a species.
EFFECT OF PHOSPHORUS DEFICIENCY ON TWO ALGAE GROWING IN CHEMOSTATS1
Authors: Healey F. P. , Hendzel L. L. 
Published: August 2007

SUMMARYphosphorus‐limited chemostats were used to study the effect of degree of phosphorus deficiency on several aspects of the composition and metabolism of Anabaena variabilis Kütz. and Scenedesmus quadricauda (Turp.) Bréb. The changes as a function of the dilution rate could be placed into 3 patterns. Most aspects of the composition showed it progressive change with dilution rate. The carbohydrate content generally increased while cellular P and nitrogen, protein, nucleic acid and chlorophyll contents generally decreased over the entire range of increasing deficiency studied. The changes in metabolism fell into a second pattern, showing great sensitivity to the onset of P deficiency. The ability to take up phosphate and the alkaline phosphatase activity increased most markedly with increasing deficiency at the higher dilution rates. The third pattern was confined to the, lipid content of S. quadricauda, which increased with deficiency only at the lowest dilution rates.
EFFECT OF WATER POTENTIAL ON A MICROCOLEUS (CYANOPHYCEAE) FROM A DESERT CRUST1
Authors: Brock Thomas D. 
Published: August 2007

SUMMARYThe effect of water potential, on the growth and photosynthesis of a species of Microcoleus forming a desert crust was determined, using both osmotic and matric variations in water potential. The alga was quite sensitive to moisture stress, partial inhibition of growth being observed at ‐7 bars, and complete inhibition at ‐18 bars. Photosynthesis was markedly inhibited at ‐18 bars, and virtually completely at, ‐28 bars (water potential of seawater) and lower. The alga was more sensitive to matric reduction in water potential than osmotic. By comparisons of these results with those obtained with other algae, it is concluded that this desert crust alga is not especially adapted to grow and photosynthesize at low water potentials, although it shows considerable ability to survive severe drought conditions.
MERCURY ACCUMULATION IN PEDIASTRUM BORYANUM (CHLOROPHYCEAE)1,2,3
Authors: Richardson Thomas R. , Millington William F. , Miles Harry M. 
Published: August 2007

SUMMARYLaboratory grown cultures of the green alga Pediastrum boryanum (Turp.) Meneg. concentrate mercury in amounts greater than the concentration in the culture medium. The concentration effect proceeds rapidly during colony formation and is directly dependent upon the materials of the outer layer of the cell wall known to include silica and sporopollenin. The alga displays exceptional tolerance to the rather high levels of mercury used.
NITRATE UPTAKE IN MARINE PHYTOPLANKTON: (NITRATE, CHILORIDE)‐ACTIVATED ADENOSINE TRIPHOSPHATASE FROMSKELETONEMA COSTATUM(BACILLARIOPHYCEAE)1,2
Authors: Falkowski Paul G. 
Published: August 2007

SUMMARYA membrane‐bound (nitrate, chloride)‐activated AT Pase was found in the neritie diatom,Skeletonema costatum(Grev.) Cleve. The enzyme is suggested to translocate NO3−across the plasmalemma, against a concentration gradient. TheKmof the enzyme with respect to NO3−isca.0.9 × 10−6M, and is in close agreement with the reportedK8for NO3−uptake by the whole cell.
THE EFFECT OF INTERTIDAL STRESS ON PADINA SANCTAE‐CRUCIS (PHAEOPHYTA)1
Authors: Liddle Larry B. 
Published: August 2007

SUMMARYThe hypothesis is that plants growing in the intertidal region display developmental and morphological differences from subtidal plants of the same species. Intertidal and subtidal populations of Padina sanctae‐crucis Börg. Were compared, emphasizing morphological and developmental features. Plant size in relation to number of reproductive bands, vegetative cell sizes and the rate of spore development were analyzed to evaluate the hypothesis. The results indicate that environmental stress tends to dwarf intertidal plants through reduction in cell size. Spores from both intertidal and subtidal populations were cultured in the laboratory under standard conditions. No significant differences were found between the growth rates. The results may be interpreted to mean that cell enlargement is inhibited by intertidal stress.
UNIPARENTAL INHERITANCE IN CHLAMYDOMONAS EUGAMETOS (CHLOROPHYCEAE)1,2
Authors: McBride A. Charles , McBride Judy C. 
Published: August 2007

SUMMARYThe gene sr‐2 conferring resistance to 500 μ/ml streplomycin exhibits uniparental inheritance in Chlamydomonas eugametos Moewus. The mutation to neamine dependence (nd) is probably of the same type. All meiotic progeny from crosses involving these mutant genes have the phenotype of the historically designated male parent. Unlike C. reinhardtii Dang., no exceptional zygotes have been observed.