摘要:

ABSTRACTDuring competition for phosphate in continuous cultures, Cosmarium subcostatum Nord. routinely displaced Staurastrum paradoxum Meyer. The rate of displacement was independent of cell density between 100 and 6000 cells mL−1. This suggests that competition for nutrients is important over a wide range of naturally occurring cell densities. C. subcostatum had higher saturated rates of phosphate uptake but also higher half saturation values for uptake. As a result, the two desmids were similarly able to take up phosphate at low concentrations. The competitive advantage of C. subcostatum lay in its greater yield per unit of phosphorus. Growth of the two algae in shared medium in a dual‐chamber chemostat had no effect on uptake or yield characterist

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1988.tb04468.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

ABSTRACTA method for the isolation of total blade, chloroplast and nuclear DNAs from kelp is described. Total blade DNA was isolated from various kelp species at yields of about 1.0 μg.g−1wet weight of tissue extracted. Purified chloroplast and nuclear DNAs were isolated from Macrocystis integrifolia at respective yields of about 0.05 μg.g−1and 1.0 μg.g−1wet weight of tissue extracted.Hybridization experiments with a cloned portion of the 23S rRNA gene of M. integrifolia as probe (pMiR23S) showed that the M. integrifolia chloroplast genome contains two copies of the 23S rRNA gene.Three regions of the kelp chloroplast genome were studied by restriction analysis of the cpDNA of five genera. Respective differences were assessed by comparing the restriction fragment patterns produced with five restriction endonucleases for each of three cloned M. integrifolia cpDNA hybridization probes. The kelp cpDNA sequences that hybridized to the repeated sequence probe pMiR23S were less divergent (100 × p = 2.53) than were the sequences that hybridized to the single copy probes pMiR432 and pMiH7 (100 × p = 7.48–7.74). Sequence variation (100 × p) between kelp species ranged from 3.38–6.82. Sequence variation between kelp species and Fucus gardneri ranged from 9.08–12.04.Chloroplast DNA restriction fragment length data were used to derive two most parsimonious phylogenetic trees. Both trees had consistency indexes of 0.78 and indicated that the three lessoniacean genera in the comparison do not comprise a single

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1988.tb04469.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

ABSTRACTBlue‐green algal (cyanobacterial) crusts composed of nitrogen fixing Nostoc commune Voucher ex Born. et Flah. and Tolypothrix conglutinata var. colorata Ghose were studied in the upper‐subalpine life zone, Mission Mountain Wilderness, Montana. Rates of ethylene production were highest in the submerged shoreline crusts, lower for exposed crusts pioneering rocky shorelines and lowest in the Carex meadow. Nitrogenase activity (acetylene reduction technique) was constant between 200–285% crust moisture content (wet/dry weight) and then rapidly declined to 0 between 200–140%. Optimal temperatures for ethylene production by illuminated cells was between 20–30° C for T. conglutinata, 20° C for N. commune and about 25° C in darkness for both species. Nitrogenase activity by T. conglutinata in culture was unaffected by repeated freeze‐thaw treatments whereas N. commune was severely inhibited. In contrast, N2‐ase activity of these two species in an intact crust was unaffected by repeated freeze‐thaw treatments. Application of nitrogen‐free growth medium to intact crusts increased nitrogenase activity by 3.7 times implying that these were mineral deficient under field conditions. Photosynthesis was light saturated at 125 μmol‐m−2.s−1whereas nitrogenase activity was light independent for cells with carbohydrate reserves. When carbohydrate reserves were reduced by 8 h incubation in darkness, between 1–3 h of illumination were required to restore nitrogenase activity to 80% of the maximum rate. Biochemical pathway inhibitor studies employing DCMU, MFA, and CCCP showed that oxidative metabolism was the source of reductant for acetylene reduction. Tetrazolium precipitation in heterocysts paralleled acetylene reduction activity i

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1988.tb04470.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

ABSTRACTTemperature tolerance (1 week exposure time) was investigated in 49 species of benthic marine macroalgae and two seagrass species from San Juan Island (Washington) or Vancouver Island, British Columbia. Positive net photosynthesis was the parameter used to detect survival. Most algal species survived ‐1.5° C (the lowest applied temperature), and none 30° C. The most heat‐tolerant, eurythermal algal species survived 28° C: these were Ahnfeltia plicata, Mastocarpus papillatus (as crustose tetrasporophyte), Endocladia muricata, and Sargassum muticum. In contrast, most representatives of the Laminariales exhibited a cold‐stenothermic character: Cymathere triplicata, Pleurophycus gardneri, Hedophyllum sessile, Postelsia palmaeformis survived up to only 15° C, and Laminaria saccharina, L. groenlandica, L. setchellii to 18° C. As to the seagrass species, Zostera marina survived a temperature range of ‐ 1.5 to 30° C and Phyllospadix scouleri a range of ‐ 1.5 to 25° C. For many of the sublittoral species there was agreement between maximum survived temperatures in our experiments and average maxima of summer temperatures at the southern geographical limits of the species. Specimens of four species exhibited upper survival limits similar to those of conspecifics in the North Atlantic; namely, Desmarestia ‘aculeata, D. viridis, Plocamium cartilagineum, and Ahnfeltia plicata. These results favor the interpretation of upper temperature survival limits as conservativ

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1988.tb04471.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

ABSTRACTDiel patterns of photosynthesis and cell division were examined in Thalassiosira weissflogii Grun. (clone Actin) grown in nitrogen‐limited cyclostat culture. Ammonia (NH4+) was either supplied continuously or as a daily pulse to cultures grown in constant light or in a light: dark cycle. When either nitrogen or light was supplied periodically, both cell division and photosynthetic capacity were periodic. When both nitrogen and light were supplied periodically, cell division was coupled to the N‐pulse whereas periodicities of photosynthetic capacity were modified but remained coupled to the light‐dark cycle. Diel oscillations in photosynthesis were i) largely independent of cellular pigmentation and ii) similar for light‐limiting and saturating irradiances. Periodicity in photosynthetic capacity also persisted following transfer of non‐dividing batch cultures to constant light. Results suggest that photosynthesis but not cell division was coupled to a circadian clock in T. weissflogii. A circadian rhythm of photosynthesis may optimize carbon assimilation in phytoplankton exposed to intermittent nutrient supply by ensuring that maximum photosynthetic capacity occurs durin

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1988.tb04472.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

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 seque

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1988.tb04473.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

ABSTRACTThe lipid and fatty acid composition ofPorphyridium cruentum was determined as a function of light intensity, temperature, pH, and salinity. In cultures cultivated at the optimal temperature under non‐limiting light conditions, eicosapentaenoic acid was the main polyunsaturated fatty acid. When growth rate was reduced by decreased light intensity, increased cell concentration, suboptimal temperature, suboptimal pH, or increased salinity, the content of eicosapentaenoic acid decreased and that of arachidonic acid increased, the latter becoming the major polyunsaturated fatty aci

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1988.tb04474.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

ABSTRACTAscophyllum nodosum(L.) Le Jol. was freed from bacteria and the endophytic fungusMycosphaerella ascophylliCotton by repeated treatment with chlorine solutions and grown in artificial seawater. Two types of axenic culture of different origin were obtained. Type 1 was developed from apices ofA. nodosumcollected in the sea. Type 2 was from plants which developed from adventitious embryos on rhizoids formed by type 1. This is the first timeA. nodosumhas been cultivated axenically. Growth of the axenic alga was increased by IAA, 21P and zeatin. Without external growth regulators some strains of the axenic alga deteriorated within a year; others developed a filamentous habit. Sulfur in a reduced state also stimulated growth. Addition of either glucose, mannose or mannitol to the medium caused the formation of calluslike layers of loosely packed colorless cells under the epidermis of the thalli and the epidermis was sloughed off. No increase in thallus length was noticed.Mycosphaerella ascophylliin axenic culture did not excude any substances stimulating growth of the alga, but that does not exclude an influence of the fungus on the alga in vivo. The fungus, when growing within the alga, seemed to have little influence on algal morphology. A bacterized but fungus‐freeA. nodosumwas cultivated in an artificial seawater for 8 years. In the bacteria‐free alga, the fungus protruded from the epidermis and evidently utilized the alga as a carbon source. The bacteria thus seem much more important than the fungus for normal growth of theAscophyllumpl

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1988.tb04475.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

ABSTRACTAlgal community structure is described for a deep‐water rock pinnacle in the Gulf of Maine. Three depth zones of algal dominance were apparent consisting of 1) leathery macrophytes (to 40 m), 2) foliose red algae (to 50 m) and 3) crustose algae (fleshy crusts to 55 m and coralline crusts to 63 m). Microscopic filamentous and erect calcareous algae were also present but inconspicuous. Upright macroscopic filamentous and thin sheet‐like forms were not observed on the pinnacle. Sea anemones(Metridium senile)dominated some vertical faces and abrupt prominences in the shallowest regions of the pinnacle (to 24 m) and locally appeared to set the upper vertical limits of kelp and possibly foliose reds. Laminariasp. formed an open park‐like canopy from 24 to 30 m whereasAgarum cribrosum,the deepest kelp, grew as isolated individuals to 40 m.Peyssonneliasp. andLeptophytum laevewere the deepest occurring fleshy (to 55 m) and calcareous crusts (to 63 m), respectively. The occurrence of these algae at record depths for the Gulf of Maine and for cold water marine environments may be the result of an absence of large herbivores and the high productivity potential of the benthos in these relatively clear waters. By compiling data on depth distribution patterns world‐wide, it is evident that the three zone structure of algal morphologies observed in the Gulf of Maine is a global phe

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1988.tb04476.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

ABSTRACTThe influence of periodic nutrient supplies and a photocycle on phytoplankton competition for limiting nutrients was examined using the diatomsThalassiosira rotulaMeunier (clone 411) andChaetocerossp. cf.vixvisibilis Schiller(clone 847). Chaetocerossp. cf.vixvisibilisdisplacedT. rotulafrom ammonium‐limited cultures under constant light irrespective of whether ammonium was supplied continuously, in 6 pulses.day−1or in a single daily pulse. In contrast, the species coexisted under the 14:10 h LD photocycle under either continuous or pulsed ammonium supplies with the relative abundance ofC.sp. cf.vixvisibilisincreasing as the interval between ammonium additions lengthened. Coexistence was not observed with either silicic acid or nitrate limitation.Chaetocerossp. cf.vixvisibilisdisplacedT. rotula from both nitrate‐ and silicic acid‐limited chemostat cultures and from semi‐continuous cultures grown under the same photoperiod that produced coexistence with a daily pulse of ammonium.The presence of a photocycle was both necessary and sufficient to permit coexistence with ammonium limitation. Under continuous ammonium supply the photocycle may have induced a temporal separation of ammonium uptake between species, permitting sharing of the limiting nutrient and coexistence. In contrast, the species were shown to be in direct competition for the daily ammonium pulse. A competition model suggested that coexistence in this case arose from a balance between the species’ammonium uptake rates and their nitrogen demands for steady‐state growth induced by the photocycle. The results indicate that variations in nutrient supply rates may contribute to the coexistence of phytoplankton species in the sea, but that the identity of the limiting nutrient and the influence of variations in other non‐limiting resources play important roles in affecting the outcome of nutrient competition among p

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1988.tb04477.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY