摘要:

SUMMARYThe epipelic algae found in 9 rivers of southern Baffin Island were investigated during the 1972 growing season. The overall assemblage consisted of 240 taxa, of which 200 belonged to the Bacillariophyta and, only 17 to the Chlorophyta. Members of the Bacillariophyta accounted for S7–100% by numbers and 44–100% by volume of the algae at most localities. The dominant taxa wereAchnanthes kriegeriKrasske,A. marginulataGrun., andTabellaria flocculosa(Roth.) Kütz. The Chlorophyta comprised. 0–7% by numbers and 0–30% by volume of the algae, withCosmarium tinctumRalfs,Cylindrocystisspp., andMougeotiasp. being most common.The standing crop in the different rivers commonly exceeded 8 × 106cells/cm2(8 × 109μ3/cm2), and a maximum growth rate of 3.2 × 105cells/cm2/day (3.2 × 108μ/cm2/day) was observed. Temperature and light are considered important, factors in the regulation of algal numbers, while nutrient supply in the overlying water, grazing by herbivores, wave action, and flooding appeared to have

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1974.tb02677.x

出版商:Blackwell Science Inc    

年代:1974

数据来源: WILEY

摘要:

SUMMARYSix strains of branched blue‐green algae were examined in a search for lines to an explanation for apparent noncompetitiveness. Classical taxonomic treatments were often inadequate for confident species determination; forms that were very differ their morphologically frequently “keyed” to the same species. Strain distinctions based on comparative morphological and physiological studies were inconclusive. With the exception of 1 species, there were no substantial differences in physiological rates. In addition to the branching habit, diversity of cellular form was found to be an outstanding group characteristic. Individual cells of developing trichomes became a spore‐like and then divided to produce either cell clusters or lateral branches. The eventual separation of daughter cells by sheath materials may be analogous to spore formation in Nostocales and could be the factor which determines the nature of these organisms. The Stigonemataceae may not represent the pinnacle of blue‐green algal development but may, instead, be a primitive and basic form linking coccoid and filament

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1974.tb02678.x

出版商:Blackwell Science Inc    

年代:1974

数据来源: WILEY

摘要:

SUMMARYScaly green monads are often placed in a separate class, Prasinophyceae, and have been considered to be among the most, primitive of green algae. Platymonas possesses rhizoplasts which resemble sarcomeric structures. At prophase, extranuclear spindle micro‐tubules emanate from a granular region which appears to arise through dissolution or dispersion of the rhizoplasts. It is probable that the rhizoplasts are largely consumed during the formation of the spindle and only small fragments are left at metaphase. The rhizoplasts can be seen again at telophase but are short at this stage. The basal bodies are not at the spindle poles but remain at their interphase position. The interzonal spindle collapses early at telophase, and shortly thereafter cleavage microtubules appear. These microtubules extend from the region of the basal bodies to the posterior of the cell. The events of cell division are compared with these events in other green algae and in Ochromonas. The functional and phylogenetic significance of the observations is discusse

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1974.tb02679.x

出版商:Blackwell Science Inc    

年代:1974

数据来源: WILEY

摘要:

SUMMARYThe “root‐like” haptera of the holdfast of Alaria esculenta (L.) Grev. display a negative phototropic curvature only when unilaterally irradiated with blue (432 nm) and green (552 nm) wavele

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1974.tb02680.x

出版商:Blackwell Science Inc    

年代:1974

数据来源: WILEY

摘要:

SUMMARYRhamnochrysis aestuarinaefrom Ipswich, Massachusetts, is a new species of benthic marine chrysophyta. Details are given describing its gross and fine structure morphology, its reproductive life history as understood from, both field and culture studies, and its ecology and probable systematic position in the Chrysomeridaceae (Sarcinochrysidales).

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1974.tb02681.x

出版商:Blackwell Science Inc    

年代:1974

数据来源: WILEY

摘要:

SUMMARYThe diatomPhaeodactylum tricornutumBohlin is known to be pleomorphic. Previously it was considered that growth on medium solidified with agar produced ovate cells, whereas growth in liquid medium gave rise to fusiform cells. We have shown that ovate cells can be propagated in liquid medium if the calcium content of the medium is below 15 mg/liter. If the concentration of calcium is raised, fusiform cells develop.

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1974.tb02682.x

出版商:Blackwell Science Inc    

年代:1974

数据来源: WILEY

摘要:

SUMMARYThermal denaturation profiles of32P‐labeled DNA obtained from synchronous cultures ofCryptothecodinium cohniiwere examined by elution from hydroxyapatite over a temperature range of 65 to 99 C. The profile of uniformly labeled DNA from this organism shows at least 4 discrete components which elute after a temperature of 83 C is reached. These components from the “high melt” region of the profile appear to be synthesized during the latter one‐third of the S phase in synchronous

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1974.tb02683.x

出版商:Blackwell Science Inc    

年代:1974

数据来源: WILEY

摘要:

SUMMARYAmebae differed greatly in their ability to prey on algae. Species ofChlamydomonas, Pandorina, Anabaena, Ourococcus, Ankistrodesmus,andGloeocystiswere utilized by 3 or all 4 of the test protozoa, while strains ofStaurastrumandChlorellawould not support growth of the predators. Heating the cells ofChlorellasp. rendered them available to the 4 amebae and madePandorina moruma better nutrient for some of the protozoa. HeatingChlamydomonas oblongahad no effect on its availability toTetramituis rostratusand reduced its suitability as a food source forAmoeba discoides.The rate of protozoan feeding was also influenced by temperature, pH, and age of the algal prey.

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1974.tb02684.x

出版商:Blackwell Science Inc    

年代:1974

数据来源: WILEY

摘要:

SUMMARYBenthic algal‐bacterial mats are present in the effluents of alkaline hot springs at temperatures between 50 and 73 C. The thin surface layer is composed of the unicellular blue‐green algaSynechococcus lividus. Also present in the surface layer and forming thick, orange mats beneath it, are filamentous, phototrophic, gliding bacteria of the genusChloroflexis, also capable of heterotrophic growth. The very low species diversity and the constancy of the hot spring environment, make these mats a good ecosystem for studying the transfer of nutrients from the algae to the bacteria. To determine whether the alga might supply organic materials to the bacterium, excretion by natural populations ofS. lividuswas studied in the field by means of short‐term radioisotope experiments. Under optimal conditions for photosynthesis, between 3 and 12% of the total14C fixed was excreted as14C‐labeled organic compounds. Variations in cell density at concentrations ofS. lividusapproximating those found in the mat had no effect on the percentage excretion. However, at cell densities below a threshold, level, the percentage excretion increased with diminishing cell density. Except at very low light intensities the percentage of fixed carbon excreted, was very similar for all light intensities tested. Excretion at temperatures approaching the upper limit for growth was not significantly different from the percentage excretion values observed at lower temperatures.14C‐labeled organic compounds excreted during algal photosynthesis could be subsequently assimilated by natural populations of the bacteria present i

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1974.tb02685.x

出版商:Blackwell Science Inc    

年代:1974

数据来源: WILEY

摘要:

SUMMARYSynchronous mitotic divisions produce multi‐nucleate cells ofSorastrum. Perinuclear envelopes of endoplasmic reticulum and a virtually intact nuclear envelope enclose mitotic nuclei. Cytoplasmic cleavage, which shirts before the last round of Synchronous mitoses, gives rise to uninucleate fragments which differentiate to form zoospores. These zoospores are released into a spherical vesicle, presumably derived from the inner layer of the parental cell wall, in which they swarm actively before aggregating as a spherical colony. The roughly conical shaped zoospores apparently adhere laterally before withdrawing their flagella and extending horns and a stipe, which, following wall deposition, interconnects the cells at the center of the colony. The probable role of the microtubules, which underlie the plasmalemma of aggregating cells, in determining the shape of both the cells and the colony itself is discusse

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1974.tb02686.x

出版商:Blackwell Science Inc    

年代:1974

数据来源: WILEY