摘要:

SUMMARYIn axenicChlorella pyrenoidosaChick cultures, extracellular release was linear with time, but plateau‐type curves were obtained in cultures with added bacteria. Initial rates of excretion were identical in both, systems. Kinetics of extracellular release in axenicAnabaena flos‐aquae(Lyng.) Bréb. cultures were more complex than inChlorellabut the initial excretion rates were identical in axenic and mixed algal‐bacterial cultures. In lakewater, extracellular release kinetics resemble the pattern in mixedChlorella‐bacteria cultures. An explanation is an initial lag in bacterial utilization of algal extracellular products. As a result, bothin situand in the laboratory, consecutive short, experiments give higher excretion rates than single long incubations. It is suggested that the former are close to total or gross extracellular release rates whereas the latter give net values, detecting only substances not, removed by hete

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1976.tb02816.x

出版商:Blackwell Science Inc    

年代:1976

数据来源: WILEY

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1976.tb02419.x

出版商:Blackwell Science Inc    

年代:1976

数据来源: WILEY

摘要:

SUMMARYThe taxonomic history of the desmid generaOnychonemaWallich,SphaerozosmaCorda andTeilingiaBourrelly is reviewed. In addition, Teiling's studies on asymmetry applied toOnychonemaandSphaerozosmaare considered. Observations based on SEM examination of one species each ofOnychonemaand ofSphaerozosmaare presented to show morphological differences. Finally, an appraisal of the taxonomic proposals by Telling and Bourrelly is given.

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1976.tb02817.x

出版商:Blackwell Science Inc    

年代:1976

数据来源: WILEY

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1976.tb02420.x

出版商:Blackwell Science Inc    

年代:1976

数据来源: WILEY

摘要:

SUMMARYDiatom systematics depends almost entirely upon structure of the silica shell. It is not known to what extent the taxonomic species, as defined by shell structure, corresponds to the genetic species—i.e., to the reproductively isolated population. As an approach to this problem, we report here a comparison of enzymes by electrophoresis. We have examined the genetic constitution of a number of clones of (presumably) the same species for each of 2 closely related, centric diatom species:Thalassiosira pseudonanaHasle and Heimdal andT. fluviatilisHustedt. The 4 clones ofT. fluviatilisform a distinct group, clearly separated from all theT. pseudonanaclones. WithinT. pseudonana, 4 estuarine clones and one reef clone form a group that is distinctly different from 4 oceanic clones. A single clone ofT. pseudonanafrom the Continental Slope waters is intermediate between these 2 groups and probably shares genes with both groups, indicating that the 2T. pseudonanagroups are not genetically isolated. We conclude that i) within groups, isolates are closely related even though they originated from different continents; and, ii)T. pseudonanais subdivided into ecological race

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1976.tb02818.x

出版商:Blackwell Science Inc    

年代:1976

数据来源: WILEY

摘要:

SUMMARYPreadapted cultures were grown in a 12:12 LD cycle at a series of light intensities under cool‐white, fluorescent lamps.Pyrocystis fusiformisMurray maintained high division rates at low light intensities at the expense of cell size. In contrast,Dissodinium lunula(Schuett) Taylor had relatively lower division rates at low light intensities with little concomitant decrease in size. The response ofP. noctilucaMurray was intermediate between these two species. For all three, cell numbers did not increase above an intensity of 5–10 μEin·m−2·sec−1and division rate was saturated atca.30, 60, and 60μEin·m−2·sec−1forP. fusiformis, P. noctiluca, andD. lunula, respectively. The capacity for stimulable bioluminescence was saturated at light intensities of 0.15 μEin·m−2·day in short‐term (2‐day) experiments. In cultures ofP. fusiformisandP. noctiluca, maintained for at least one month at lower intensities than needed to saturate division rate, a decrease in the capacity for stimulable bioluminescence was accompanied by a reduction in cell size. Our results suggest that cell size and bioluminescent capacity may prove to be a potentially useful indication of the history of exposure of natural populations ofPyrocystiss

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1976.tb02819.x

出版商:Blackwell Science Inc    

年代:1976

数据来源: WILEY

摘要:

SUMMARYBipolar asymmetry has been considered a morphological characteristic sufficient for differentiation of genera among the Desmidiaceae. Therefore,Micrasterias sudanensisGrönbl., Prowse&Scott, the only species ofMicrasteriasshowing such asymmetry, is made the type of a new genus,Prescottiella, gen. nov

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1976.tb02820.x

出版商:Blackwell Science Inc    

年代:1976

数据来源: WILEY

摘要:

SUMMARYAlthough earlier North American records ofStictyosiphon soriferus(Reinke) Rosenvinge cannot he substantiated, the species is shown to be common in Newfoundland and is also reported from Nova Scotia. Plants are summer annuals and a component of ephemeral subtidal communities characteristic of suitable inlets and harbors. Only plurilocular reproductive organs are produced. In culture the life history of populations from both sides of the North Atlantic consists of a direct replication by asexual zoospores. A microscopic stage might occur in the field, and is presently known only from European cultures. In eastern CanadaS. soriferusis readily distinguishable fromS. tortilis(Rupr.) Reinke,S. subsimplexHolden andS. griffithsianus(Le Jol.) Holmes&Batters.

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1976.tb02821.x

出版商:Blackwell Science Inc    

年代:1976

数据来源: WILEY

摘要:

SUMMARYThe life history ofColeochaete scutataBréb. was analyzed by Feulgen microspectrophotometry, a technique measuring DNA content in individual nuclei. By correlating nuclear DNA content with morphological structures or stages in the life history, changes in ploidy level are revealed.The microspectrophotometric study confirmed the earlier reports of a haploid vegetative thallus with mitotic division restricted primarily to the margin of the thallus. In the mitotic cycle the G1(pre‐synthesis) phase is longer in duration than the synthesis find G2(post‐synthesis) phases. Oogamous sexual reproduction results in resistant oospores which attain DNA levels of 2C 8C (1C being the DNA level of gamete nuc

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1976.tb02822.x

出版商:Blackwell Science Inc    

年代:1976

数据来源: WILEY

摘要:

SUMMARYThe activity of extracted NADH‐NO3−reductase was measured in the marine dinoflagellatesAmphidinium carteriHulburt andCachonina nieiLoeblich. Its activity showed a diel periodicity and wasca.twice as great at midday as at midnight. The enzyme activity was unstable, with anin vitrohalf‐life of 2–3 h. Values of enzyme activity were low or undetectable during lag phase but paralleled the instantaneous growth rate value during log phase. Nitrate reductase activity was not found in the stationary phase of growth, but additions of NO3−resulted in enzyme activity after 24h. WhenA. carteriwas exposed to a series of light intensities for several weeks, the division rate and enzyme activity increased with increasing light intensity up to saturating intensities. In 6 h exposures, enzyme activity decreased with decreasing light intensities below light intensities saturating division rate. Additions of NH4+(0.5–50 μm) toA. cartericultures decreased the amount of extractable enzyme. Thein vitroactivity was not inhibited by similar NH+4co

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1976.tb02823.x

出版商:Blackwell Science Inc    

年代:1976

数据来源: WILEY