bluuebunny/crossref_metadata_2025_split huggingface dataset:
GENETICS OF GRACILARIA TIKVAHIAE (RHODOPHYCEAE). XI. FURTHER CHARACTERIZATION OF A BISEXUAL MUTANT1,2
Authors: van der Meer John P. 
Published: March 2008

ABSTRACTA spontaneous bisexual mutant of Gracilaria tikvahiae McLachlan has been further characterized. Female plants that are carriers for the mutation, but do not themselves express bisexuality, have been identified among progeny derived from the original bisexual male plant. In crosses to normal males these carrier females yielded normal tetrasporophytes which in the subsequent gametophyte generation produced a 2 female: 1 male: 1 bisexual segregation. In crosses to bisexual males the carrier females produced unusual tetrasporophytes that formed cystocarps in addition to tetraspores. The gametophyte generation obtained from the tetraspores of these tetrasporophytes included only females and bisexuals, these being present in a 1:1 ratio. Other crosses, using bisexual male progeny, indicated that these have the same characteristics as the original bisexual mutant. All of the results are consistent with the genetic interpretation made previously that bisexuality results from a single recessive mutation, designated bi, in a gene distinct from the mt locus controlling male vs. female differentiation. From the phenotypes that have been observed it appears that the mutation does not cause bisexuality per se but rather results in unregulated female expression in males and tetrasporophytes where female‐specific genes are normally repressed. It is suggested that the normal bi+ allele plays an important role in that repression process.The origin of the bisexual mutation has been re‐examined by studying the progenitor stock of the mutation and stocks related to it. It appears that the bisexual mutation arose in a two‐step process, first to a low level of expression that is found in the progenitor stocks and then to the high level of expression found in mutant clone 1045(bi) and its descendants.
MORPHOLOGICAL VARIABILITIES OF THREE CLOSELY RELATED MATING GROUPS OF CLOSTERIUM EHRENBERGII MENEGHINI (CHLOROPHYTA)1
Authors: Kasai Fumie , Ichimura Terunobu 
Published: March 2008

ABSTRACTThe ranges of morphological variabilities in vegetative cells of three closely related mating groups of Closterium ehrenbergii Meneghini were statistically analyzed, having been grown under standard and uniform culture conditions, using Group A clones from Japan and Australia, Group B clones from Japan and Taiwan and Group H clones from Nepal. Significant differences in the morphological characters were not recognized between the two complementary mating types in any of the three groups. It has been shown that cells of Group A are smallest (mean width 50 μm and mean length 250 μm) and cells of Group B are largest (mean width 67 μm and mean length 404 μm), while cells of Group H are intermediate (mean width 57 μm and mean length 333 μm). There are considerable differences in the mean cell size between the three mating groups, although some intergrading clones were recognized. Degrees of the intergrading overlap were shown to be small between the sympatric groups (A and B) and large between the two pairs of allopatric groups (A and H & B and H). It has been shown that cells of Group A are shorter and much more curved than cells of the other two mating groups. Cells of Groups B and H are slender and less curved. It has also been shown that the ranges in cell size of each mating group are smaller than those currently accepted for C. ehrenbergii.
ULTRASTRUCTURE OF MALE GAMETES OFSPHAEROPLEA ROBUSTA(CHLOROPHYCEAE)1
Authors: Buchheim Mark A. , Hoffman Larry R. 
Published: March 2008

ABSTRACTMale gametes have been studied in Sphaeroplea robusta (Chlorophyceae) using both light and electron microscopy. Mature gametes are typically biflagellate and possess a single, large mitochondrion that dominates the anterior third of the cell, directly posterior to the basal bodies. One or more microbodies are closely associated with the mitochondrion. Contractile vacuoles occur anterior to the elongated nucleus which, in fully mature gametes, possesses condensed chromatin. The reduced, starch‐filled chloroplast lacks an associated eyespot and occupies a posterior position. A thin, anteriorly directed process or extension of the chloroplast parallels a portion of one of the multistranded flagellar roots. The paired basal bodies are directly opposed with no demonstrable offset, and are connected by an arched distal fiber with a highly elaborated central striated region that forms the apical cone, a feature characteristic of male gametes in most species of Sphaeroplea. Possession of a striated distal fiber, a cruciate flagellar root system (i.e. two‐stranded microtubular roots alternating with multistranded roots), and directly opposed basal bodies are consistent with the alga's chlorophycean affinities.
COMPONENTS OF PHOTOSYNTHESIS IN THE INTERTIDAL SACCATE ALGA HALOSACCION AMERICANUM (RHODOPHYTA, PALMARIALES)1
Authors: Oates Brian R. 
Published: March 2008

ABSTRACTRates of photosynthesis for the intertidal saccate alga Halosaccion americanum Lee were determined under submersed and emersed conditions. By fitting the data to a hyperbolic tangent function, P max was 4.08 mmol CO2. m−2. h−1 and Ik was 116.4 μE. m−2. s−1. under submersed conditions. Under emersed conditions, P max was 1.89 mmol CO2. m−2. h−1 and Ik was 22.9 μE. m−2. s−1. Dark fixation represented 3.7% of Pmax in submersed thalli, whereas it equalled 33.3% of Pmax in emersed thalli. Photosynthetic uptake from the thallus cavity represented a significant source of carbon, achieving 68.8% of that from the atmosphere and 29.4% of that from seawater. Retained seawater also greatly reduced drying under emersed conditions. Experimental thalli lost 70.4% of their water after 120 min under desiccating conditions, whereas control thalli lost only 6.3%. Emersed photosynthetic rates were enhanced by desiccation, At times, rates for desiccated thalli were two times those of fully‐hydrated ones. Only after water loss exceeded 47% did photosynthetic rates fall below fully‐hydrated rates. Utilizing data from this study a model was constructed to determine total photosynthetic production of H. americanum over a single daylight period. These caluclations demonstrate that photosynthetic contributions from emersed photosynthesis and retained seawater are significant. Because production from all sources is almost equal, total photosynthesis over a single day does not change greatly regardless of the time spent in air or in water.
NUTRIENT AND LIGHT LIMITATION OF ALGAE IN TWO NORTHERN CALIFORNIA STREAMS1
Authors: Hill Walter R. , Knight Allen W. 
Published: March 2008

ABSTRACTNutrient‐diffusing subsrates were used to investigate nutrient limitation of attached algal assemblages in a shaded stream and an unshaded stream in northern California. Water from both streams contained low levels of nitrogen (< 14 μg.L−1) and very low N:P ratios (< 2). After 31 days of colonization and growth, attached algal biomass on nitrate‐diffusing substrates was significantly greater than on control substrates in the unshaded stream. Nitrate‐diffusing substrates also supported larger numbers of grazing insects in the unshaded stream. The prostrate diatoms Achnanthes lanceolata Bréb. and Coconeis placentula Ehr. displayed the most consistent positive responses to nitrate enrichment. Nutrient enrichment did not increase the accrual of algal biomass in the shaded stream, but algal biomass was significantly greater at sites located under openings in the tree canopy, implicating light as a limiting factor in this stream. Several Navicula and Nitzschia species, and one unidentified Gomphonema species, were positively associated with higher light levels in the shaded stream. Shade appears to be the primary factor limiting algal growth in small northern California streams, but when its effect is reduced by logging, the inherently low levels of nitrogen in these streams can become limiting.
ULTRASTRUCTURE OF THE GAMETE OFPEDIASTRUM DUPLEX(CHLOROPHYCEAE)1
Authors: Wilcox Lee W. , Floyd Gary L. 
Published: March 2008

ABSTRACTGametes of Pediastrum duplex Meyen were investigated ultrastructurally, with emphasis on the flagellar apparatus. The cells are naked, biflagellate, and measure approximately 2.5 × 8 μm. Distinguishing them from zoospores is their possession of an eyespot and mating structure (the apical cap), and their lack of the peripheral band of cytoplasmic microtubules involved in colony formation. Four featurs of the flagellar apparatus are especially noteworthy: (1) the basal bodies are directly opposed and (2) are interconnected via their cores, (3) the central portion of the distal fiber is elaborated into an unusual ribbed structure which overlies the striated microtubule‐associated component (SMAC) of the two‐membered rootlets, and (4) the X‐rootlets are dissimilar in microtubular number. The smaller X‐rootlet consists of four microtubules in a three over one (3/1) configuration, whereas the larger has been found to be either 5 / 1, 6 / 1 or 7 / 1. The former rootlet extends past the nucleus whereas the latter extends down the opposite side of the cell, passing near the eyespot. The first two of these flagellar apparatus features have been previously noted in other motile cells of the Hydrodictyaceae. Although not specifically mentioned, published micrographs suggest the presence of the latter two as well, which may indicate that all four flagellar apparatus features are characteristics of all motile cells in the Hydrodictyaceae.
SIMILAR UNSTABLE MUTATIONS IN THREE SPECIES OF GRACILARIA (RHODOPHYTA)1
Authors: van der Meer John P. , Zhang Xuecheng 
Published: March 2008

ABSTRACTUnstable mutants with similar variegated pigmentation were genetically characterized in the red algae. Gracilaria tikvahiae (McLachlan), G. foliifera (Forsk.) Børg. and. G. sjoestedtii (Kylin). All three mutants were green plants with flecks of red tissue where cells had reverted to wild type. The mutant green phenotypes were all recessive, and their genetic behavior in crosses indicated that each was the result of a single, unstable, nuclear gene. Wild‐type revertant tissue was stable one it arose. Revertant plants obtained from spores and revertant fronds taken from variegated plants could not be distinguished from the normal wild type, either phenotypically or genetically. Reversion to wild type occurred during all phases of the life cycle. In crosses between the mutants and wild type, most of the F1 tetrasporophytes were heterozygous wild‐type plants, an observation consistent with the recessive nature of the mutations; however, a low frequency of homozygous unstable‐green F1 tetrasporophytes was also obttained from these crosses. The molecular basis of neither the mutant instability, i.e. the reversion to wild type, nor of the process producing the unstable green F1 tetrasporophytes can yet be deduced, but the phenotype of the plants and genetic results suggest the involvement of transposable genetic elements.
THE TIME‐COURSE OF PHOTOADAPTATION TO LOW‐LIGHT IN PROROCENTRUM MARIAE‐LEBOURIAE (DINOPHYCEAE)1
Authors: Harding Lawrence W. 
Published: March 2008

ABSTRACTThe estuarine dinoflagellate, Prorocentrum mariaelebouriae (Parke & Ballantine 1957) Faust 1974 undergoes increases in pigmentation and photosynthetic efficiency within several days of downward light shifts. These changes can be described by first‐order kinetics, as has been reported previously for Chlorophyll (Chl) a in several phytoplankton species. The studies described in this paper were conducted with isolates of populations of Prorocentrum from the Chesapeake Bay. We determined rates of adaptation to low‐light for cultures grown at a range of photon flux densities (I0= 2.65–26.2 E.m−2, d−1, shifted to 6.3–7.0% I0) at three temperatures (10°, 15°, and 20° C), bracketing the conditions this species experiences in situ. In this paper, I report the time‐course of changes in α, Pmax Chl a, peridinin, and Ik and first‐order rate constants, K1 for changes in α, Chl a and peridinin. cell−1. K1 for changes in α cell−1 averaged 1.58 × 10−2 h−1 for conditions encompassing five light treatments and three temperatures; the corresponding mean for Chl a was 1.59 × 10−2 h−1. Increases in peridinin measured for five light treatments at 15° C showed a mean K1 of 1.22 × 10−2 h−1, Average percent changes in per cell α, Chl a, and peridinin ranged from 0.4–4.0% h−1 (10–90% d−1) following exposure to low‐light. Photoadaptive changes are important to Prorocentrum because in nature it occupies turbid waters (Kt≥ 0.5 m−1) where the mixing depth often exceeds the depth of the photic layer. Cells are entrained beneath a seasonally‐stable density discontinuity and are exposed to very low‐light (< I E.m−2.d−1) for days to weeks during subpycnocline transport. The ability of this species to undergo changes in pigmentation and photosynthetic physiology confers increased efficiency of light harvesting and contributes to this species’survival in the estuary where it is an important component of the dinoflagellate flora.
PHYSIOLOGICAL CHARACTERIZATION OF SIX LIPID‐PRODUCING DIATOMS FROM THE SOUTHEASTERN UNITED STATES1
Authors: Tadros Mahasin G. , Johansen Jeffrey R. 
Published: March 2008

ABSTRACTSix strains of diatoms from intertidal waters were isolated as part of the SERI Aquatic Species Program collection and screening effort: Amphiprora hyalina Greville, Cyclotella cryptica Reimann, Lewin & Guillard, Navicula acceptata Hustedt (two strains, NAVIC6 and NAVIC8), Navicula saprophila Lange‐Bertalot & Bonik, and Nitzschia dissipata (Kütz.) Grunow. Among numerous algal strains isolated as part of this collection effort, these six strains showed rapid growth and elevated lipid content in preliminary screening experiments and were chosen for further physiological characterization. N. dissipata grew most rapidly at 25°C, whereas the other five strains grew best at 30–35°C. Salinity tolerance varied among strains, with maximal growth occurring at the following conductivities: 10–60 mS.cm−1 (A. hyalina and N. acceptata NAVIC8), 10–35 mS.cm−1 (C. cryptica), 20–45 mS.cm−1 (N. acceptata NAVIC6), 10 mS.cm−1 (N. saprophila), and 20–35 mS.cm−1 (N. dissipata). The diatoms also differed in their utilization of nitrogen sources with A. hyalina growing optimally with either nitrate or urea; N. acceptata NAVIC6, with either nitrate or ammonium; C. cryptica, N. acceptata NAVIC8, and N. dissipata, with nitrate; and N. saprophila, with urea. Under optimal conditions, A. hyalina grew at 2.0 doublings. day−1; C. cryptica grew at 3.0 doublings. day−1. Each Navicula strain had a growth rate of 3.8 doublings. day−1, and N. dissipata grew at 2.6 doublings.day−1. All six strains had lipid contents in excess of 37% ashfree dry weight (AFDW) under nutrient‐limited conditions, with N. saprophila having the highest lipid content at 48% AFDW.
LOTIC ALGAL COMMUNITIES IN THE MT. ST. HELENS REGION SIX YEARS FOLLOWING THE ERUPTION1
Authors: Steinman Alan D. , Lamberti Gary A. 
Published: March 2008

ABSTRACTA survey of 21 lotic habitats from the Mt. St. Helens region, Washington, was conducted during late summer 1986, six years after the eruption. A total of 152 taxa was observed (94 diatoms, 36 chlorophytes, 19 cyanophytes, 2 xanthophytes, and I rhodophyte). Sampling sites were classified by TWINSPAN (two‐way indicator species analysis) and ordinated by DECORANA (detrended correspondence analysis). In general, both techniques corresponded well with each other and grouped sites according to the intensity of disturbance that they experienced. Species richness and diversity values tended to be lowest at the most heavily disturbed sites. Chlorophyll a values ranged over two orders of magnitude and tended to be higher at sites sampled from small, low‐discharge tributaries. Loowit Creek, a thermally influenced stream that begins within the volcanic crater, was dominated by thick mats of the cyanophyte Mastigocladus laminosus. A general comparison of the present study with one conducted just after Mt. St. Helens erupted suggests that successional processes are operating in these lotic algal communities.
ULTRASTRUCTURE OF THE ZOOSPORES AND VEGETATIVE CELLS OF TETRAEDRON AND CHLOROTETRAEDRON (CHLOROPHYCEAE)1
Authors: Watanabe Shin , Floyd Gary L. , Wilcox Lee W. 
Published: March 2008

ABSTRACTThe flagellar apparatus of the zoospores of Tetraedron bitridens Beck‐Mannagetta and Chlorotetraedron polymorphum MacEntee, Bold et Archibald includes directly opposed basal bodies, a distal fiber that is elaborated into a ribbed structure to which the continuous striated microtubule‐associated component (SMAC) is connected, and partial caps over the proximal end of each basal body. The angle between basal bodies ranges from approximately 25° to 150°. Basal bodies at wider angles are interconnected via their cores. A septum is present in the B‐tubule of one basal body triplet in C. polymorphum. Both organisms have four microtubular rootlets arranged in a cruciate pattern. The two X‐membered rootlets in a single cell have dissimilar numbers of microtubules. In C. polymorphum there are 5 and 6 microtubules in a 4/1 and 5/1 arrangement. 3/1 and 4/1 rootlets are present in T. bitridens. Zoospores of T. bitridens have a fuzzy coat whereas those of C. polymorphum are naked. Pyrenoids in both species are covered by a continuous starch sheath. Vegetative, interphase cells of C. polymorphum have two centrioles connected by a fiber that are located in depressions in the nuclear envelope. We propose that these two genera may be closely related to Neochloris, and that the coenobial genera Hydrodictyon, Pediastrum and Sorastrum are derived from a Tetraedron‐like alga.
ULTRASTRUCTURAL FEATURES OF MITOSIS IN PLOEOTIA COSTATA (HETERONEMATALES, EUGLENOPHYTA)1
Authors: Triemer Richard E. , Fritz Lawrence 
Published: March 2008

ABSTRACTThe ultrastructural features of mitosis in the colorless phagotrophic euglenoid, Ploeotia costata (Farmer and Triemer 1988bn; syn: Serpenomonas costata, Triemer 1986) are described. During interphase the nucleus is rounded and lies adjacent to the reservoir and the four basal bodies, two of which bear flagella. At the onset of mitosis, two additional flagella are generated from the accessory basal bodies such that four basal bodies with flagella now lie at one pole of the prophase nucleus. Microtubules develop in the nucleus prior to migration of one of the basal body pairs to the opposite pole of the nucleus. By metaphase, chromosomes with layered kinetochores are aligned on the equator of the spindle, and a dumbbellshaped nucleolus stretches from pole to pole. Continued elongation of the nucleus results in the separation of the chromosomal masses at anaphase. The distance between the nuclear poles from metaphase to anaphase changes little although the overall length of the nucleus nearly doubles. By telophase a large interzonal spindle develops between the forming daughter nuclei. The extended interzonal spindle breaks near the center prior to cell cleavage.
BENTHIC DIATOM DISTRIBUTION IN A PENNSYLVANIA STREAM: ROLE OF pH AND NUTRIENTS1
Authors: Keithan Elaine D. , Lowe Rex L. , DeYoe Hudson R. 
Published: March 2008

ABSTRACTBuffalo Creek is in a forested watershed in eastern Pennsylvania and is relatively acid in upstream reaches (pH∼6), becoming alkaline downstream (pH∼8). Temperature, nitrogen (NO3‐N) and phosphorus (O‐PO4) increase significantly downstream whereas N/P declines. Nutrient‐diffusing substrata were deployed in triplicate at an upstream and downstream site. Six treatments included two concentrations of nitrate, two concentrations of phosphate, nitrogen + phosphate, and a control. Substrata were collected after 18 days, scraped and analyzed for accrual of chlorophyll a and algal community structure. Chlorophyll a and algal biovolume were greatest downstream across all nutrient treatments. At the community level, accrual appeared to be limited by phosphorus at upstream sites. Downstream accrual also may have been phosphorus‐limited, but the results were equivocal. Benthic algae on all treatments at both sites were ∼96% diatoms. Minimal overlap in species composition was observed between upstream and downstream sites. Of the 75 species of diatoms encountered in the study, 58 species did not occur at the upstream site and 10 species did not occur at the downstream site. The upstream site was depauperate in species and dominated by Eunotia exigua (Bréb. ex Kütz.) Rabh., which showed a positive response to phosphorus and accounted for over 50% of the biomass across treatments. The downstream site showed a four‐fold increase in species richness. Communities at this site contained some species that appeared to be phosphorus‐limited, e.g. Melosira varians Ag., and others that seemed to be nitrogen‐limited, e.g. Diatoma vulgare Bory and Navicula seminulum Grun. We conclude that extreme conditions upstream (low pH, high N/P) result in a species‐poor community dominated by acidophilous phosphorus‐limited diatoms. Increases in downstream nutrients and pH result in a relatively rich and diverse community.
PATHWAY OF AMMONIUM ASSIMILATION IN A MARINE DIATOM DETERMINED WITH THE RADIOTRACER13N1
Authors: Zehr Jonathan P. , Falkowski Paul G. 
Published: March 2008

ABSTRACTIn unicellular algae, ammonium can be assimilated into glutamate through the action of glutamate dehydrogenase (GDH) or into glutamine through the sequential activities of glutamine synthetase and glutamate 2‐oxoglutarate amidotransferase (GS‐GOGAT pathway). We have shown that the first radio‐labeled product of assimilation of13NH4+(t1/2= 10 min) was glutamine in the marine diatom Thalassiosira pseudonana (Hustedt). When GS‐GOGAT was inhibited with methionine sulfoximine, the incorporation of radioactivity into both glutamine and glutamate was blocked, implying that the radio‐labeled glutamate is formed from glutamine. Glutamine was also the first labeled product when the intracellular concentration of ammonium was elevated by preincubation with unlabeled ammonium. The results indicate that the GS‐GOGAT pathway is the primary pathway for the assimilation of nitrogen in T. pseudonana.
AMINO ACID SEQUENCE ANALYSIS OF THE SMALL SUBUNIT OF RIBULOSE BISPHOSPHATE CARBOXYLASE FROM FUCUS (PHAEOPHYCEAE)1
Authors: Keen Jeffrey N. , Pappin Darryl J. C. , Evans Leonard V. 
Published: March 2008

ABSTRACTThis paper reports for the first time amino acid sequence information for the small subunit of ribulose‐1,5‐bisphosphate carboxylase / oxygenase (Rubisco) from a non‐green alga. N‐terminal sequences are presented for the polypeptide from three species of the genus Fucus (Phaeophyceae). Although homologous to small subunit polypeptides from other organisms, the Fucus sequences exhibit a unique N‐terminal section resembling neither cyanobacterial nor chlorophytic sequences. This difference may be a consequence of the plastid DNA coding arrangement for the small subunit in chromophytes, a situation reported for the related organism Olisthodiscus but not previously investigated at the amino acid sequence level.