摘要:

SUMMARYThe diatomAchnanthes exigua, isolated from Alhambra North Hot Spring, showed a maximum growth rate of 2 doublings per day at 40 C; the maximum and minimum temperatures at which growth occurred was 44 and 10 C, respectively. The optimal temperature for respiration was 40 C, whereas the optimum temperature for photosynthesis was 42 C. Respiration exhibited greater thermotolerance than either growth or photosynthesis. Light saturation occurring at comparatively low light intensities suggests that the unialgal diatom culture may represent a selected shade‐adapted organis

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1974.tb02668.x

出版商:Blackwell Science Inc    

年代:1974

数据来源: WILEY

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1974.tb02417.x

出版商:Blackwell Science Inc    

年代:1974

数据来源: WILEY

摘要:

SUMMARYTwo‐membered cultures of 3 phytoplankters isolated from Onondaga Lake, grown in defined media under laboratory conditions, were analyzed by electronic particle counts and statistical methods to determine antagonistic, neutral, or stimulatory relationships. Over the range studied (exponential phase of growth, nutrients not limiting), growth ofStaurastrum paradoxumis markedly reduced in the presence ofChlamydomonassp. Growth ofChlamydomonasis not affected by presence ofStaurastrum. The initial concentration ofStaurastrumhas an effect on its subsequent growth. The initial concentration ofChlamydomonasdoes not have an effect on its subsequent growth nor that ofStaurastrum. These effects are not mediated by a filterable factor (unless highly labile) or by competition for a nutrient. They resemble, and perhaps describe, fluctuations of these species in the lak

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1974.tb02669.x

出版商:Blackwell Science Inc    

年代:1974

数据来源: WILEY

摘要:

SUMMARYHypnospores, a type of sculptured‐walled resting spore formed by some zoosporic chlorophycean and chrysophycean algae, have been viewed at the ultrastructural level using thin section, SEM, and freeze‐etch techniques. The “spiny” wall of the hypnospore, as seen in the light microscope, appears as a raised, scalloped surface at the ultrastructural level. The PAS‐positive wall is composed of 2 distinct layers. Prior to the formation of the wall, vacuoles form in the cytoplasm, lipid deposits are detectable, and typical cytoplasmic organelles apparently degenerate. The entire process is completed in less t

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1974.tb02670.x

出版商:Blackwell Science Inc    

年代:1974

数据来源: WILEY

摘要:

SUMMARYThe oceanic diatomThalassiosira pseudonanaHasle and Heimdal (formerlyCyclotella nana) was grown with 12L:12D illumination cycles in nitrogen‐limited continuous culture with a mixture of ammonium and nitrate as the N source. Measurements included, at 3 different growth rates (degrees of N limitation), cell concentration, cell carbon, nitrogen, and chlorophyllacontents, cell volume, photosynthetic carbon assimilation vs. irradiance, short‐term uptake of ammonium and nitrate vs. their ambient concentrations, andin vitroactivities of the assimilatory enzymes nitrate reductase and glutamic dehydrogenase.The various parameters showed either an increase (patterna) or a decrease (patternb) with increasing N limitation. Those following patternawere nitrate reductase activity and the capacity to assimilate nitrate and ammonium. Those following patternbwere glutamic dehydrogenase activity, photosynthetic rate, nitrogen:carbon and chlorophylla:carbon composition ratios. Results are discussed in terms of the interpretation such measurement for natural phytoplankton and effects of circadian periodic

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1974.tb02671.x

出版商:Blackwell Science Inc    

年代:1974

数据来源: WILEY

摘要:

SUMMARYIncubation of cultures of a high‐temperature strain of chlorella at 10 C stopped growth and bleached all chlorophyll in the cells in 24 hr. Optimal conditions of light (3.0 mw/cm2), gas (1% CO2‐in‐air), and inorganic medium for maximal growth at 39 C were maintained in the transfer from 39 to 12, 10, or 5 C. The bleaching process at 10 C is characterized by a lag period for the first few hours followed by a linear decrease in chlorophyll content of cultures. The amounts of time required to bleach half of the chlorophyll initially present (effective half‐times) at 10 C were 14 hr for chlorophyllaand 17 hr for chlorophyllb. Effective half‐times of bleaching for total chlorophyll were 47 hr at 12 C and 6 hr at 5 C.Addition of glucose to inorganic medium delayed but did not prevent bleaching. Use of argon gas instead, of 1% CO2‐in‐air prevented cells from bleaching in both inorganic and glucose media, and indicated an oxygen requirement for bleaching.Incubation of 6 additional strains ofChlorellaat 10 C resulted in responses ranging from bleaching to no gro

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1974.tb02672.x

出版商:Blackwell Science Inc    

年代:1974

数据来源: WILEY

摘要:

SUMMARYMorphological stability, with the elimination of the unicellular singe, was achieved by culturing several strains of Scenedesmus in media with, low inorganic salt levels. Organisms stabilize and form only colonies at specific nutrient levels. One became colonial only when the salt level was dropped to 3.07 mg inorganic salts per liter, with N and P at levels found in nature.

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1974.tb02673.x

出版商:Blackwell Science Inc    

年代:1974

数据来源: WILEY

摘要:

SUMMARYThe excretion of glycolic acid by the marine diatomChaetoceros socialisthrough time was studied. Excretion in axenic cultures was linear for the time intervals used, but for nonaxenic cultures an equilibrium was created, suggesting bacterial uptake of glycolic acid. In studies with an inhibitor of glycolate dehydrogenase, the level of glycolic acid in the medium jumped 15–fold. This shows the presence of this enzyme, and implies the presence of the entire set of enzymes which convert glycolic acid to serine and release carbon dioxide. In both axenic and nonaxenic cultures a steady state was reached. All of the data suggest that at high cell densities glycolic acid is liberated from the cell by a passive mechanism. The effect of such an excretion in natural waters is discusse

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1974.tb02674.x

出版商:Blackwell Science Inc    

年代:1974

数据来源: WILEY

摘要:

SUMMARYBracteacoccus minorgrows on glucose both in the dark and in the light. However, the growth rates at 50 ft‐c or higher in the presence of glucose are considerably lower than those in inorganic media at the same intensities. The lowered growth rates in the presence of glucose appear to be related to changes in metabolism toward increased production of storage carbohydrates. Glucose shortens the length of the lag phase at high light intensities and increases the length of the exponential phase at all light intensities, resulting in very high cell yields compared to cultures grown in inorganic media.B. minorhas 2 transport systems for glucose: (1) a high affinity system, KS=1 × 10−5M, which is formed in the dark in the absence of external glucose; and (2) a low affinity system, KS=5 × 10−4M, which appears to be constitutive. At high concentrations of glucose there is also significant free diffusion of glucose into the cells. The glucose analog, 3‐O‐methyl glucose, is also taken up by the inducible system, but at a lower rate than glucose. It is Acumulated, about 2000 times in a 20‐min incubation period, indicating active transport. Cycloheximide inactivates the high affinity system to the same extent as high light intensities, and also prevents induction of this system in the dark. Rates of photosynthesis are inversely correlated to glucose uptake rates over a range of light intensities of pre‐incubation. The possession of a light‐regulated high‐affinity transport system as well as a constitutive low‐affinity system for glucose is probably of competitive advantage to this alga in

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1974.tb02675.x

出版商:Blackwell Science Inc    

年代:1974

数据来源: WILEY

摘要:

SUMMARYEleven strains ofPandorina unicoccasp. nov. were studied for morphological characterization. The species was delimited by having cells which contain a single basal pyrenoid and by colonies which have cells separate from each other in the colonial envelope. A defined medium was developed for 4 strains ofP. unicoccaand the nutritional requirements of these strains were examined. All 4 strains were capable of completely autotrophic growth and they could utilize nitrate, ammonium, or urea as nitrogen sources. Optimum growth was nuts attained at pH 8.0.

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1974.tb02676.x

出版商:Blackwell Science Inc    

年代:1974

数据来源: WILEY