摘要:

ABSTRACTPrefertilization and immediate postfertilization development in the female reproductive branch ofPolysiphonia harveyi(Bailey) was studied with the electron microscope. Results pertaining to prefertilization morphology and development are consistent with those established in earlier light microscopic studies, but several unexpected ultrastructural characteristics were discovered. The mature carpogonium was found to have double membrane‐bound vacuoles of nuclear origin and the carpogonial nucleus contained a nucleolus with a distinctive crystalline lattice. Trichogynes lacked a nucleus. Of particular interest was the discovery of a highly structured channel of smooth endoplasmic reticulum (SER) which extended uninterrupted, except for pit connections, through the carpogonial branch. It is suggested that the message of fertilization is conducted through the SER channel from the carpogonium to the support cell. Few observations were made on postfertilization branches, but evidence of direct fusion between the carpogonium and auxiliary cell was fairly conclusive. Pit plugs in the female branch were found to be of three morphological types differing by the presence and number of pit membranes. We have designated these plugs Type I–III since differential functioning was not fully ascertained. Our data suggest that pit membranes may serve to stabilize the plug and that those plugs without membranes are more readily dismantled to allow cytoplasmic continuity between ce

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1982.tb03206.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

ABSTRACTThe green algaStichococcus bacillarisNaeg. is able to take up at least eleven amino acids. All of these except glutamic and aspartic acids are transported by carrier systems that obey saturation kinetics. The acidic amino acids enter the cell by passive diffusion. Michaelis‐Menten parameters (Ksand Vmax) were calculated for several amino acids. All obey simple Michaelis‐Menten behavior except for 2‐methylalanine and leucine which may have double carrier systems of different affinities. Interactions between pairs of amino acids suggest that there is at least one carrier system specific for basic amino acids and probably several systems specific for neutral amino acids. Further analysis of neutral amino acid interactions reveal that the uptake of several amino acids is incompletely inhibited by competitor uptake at infinite concentration. The simplest interpretation of the data is the operation of three carrier systems for neutral amino acids, one of which has higher affinity and broader specificity than the other two. The amino acid carrier systems appear to operate by an active mechanism. The metabolic poison DCCD inhibits uptake up to 99%. The capacities of the neutral amino acid carrier systems are increased when cells are grown in medium containing suboptimal concentrations of nit

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1982.tb03207.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

ABSTRACTAcrosymphyton firmumsp. nov., is described from the northeastern coast of North 1., New Zealand. Gametophytes are spring–summer annuals which grow subtidally on cobbles. Thalli are uniaxial; each axial cell bears a whorl of four indeterminate and one determinate branchlets. Indeterminate branchlets are alternately arranged giving the thallus a distichous and feather‐like appearance. Numerous corticating rhizoidal filaments are produced from the periaxial and lower whorl branchlet cells. These rhizoids entwine and obscure the main axis as the thallus develops until in the mature plant the axes have a firm consistency and lubricous texture. The carpogonial branch bearing short lateral filaments and auxiliary cell branch with terminal auxiliary cell place this new species in the genusAcrosymphytonSjöstedt. Of the three described species in the genus,A. firmumis most similar toA. taylori.This is the first report of the genusAcrosymphytonand the only confirmed report of the family Dumontiaceae in New Zealand wa

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1982.tb03208.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

ABSTRACTThe flagellar apparatus ofPyrobotryshas a number of features that are typical of the Chlorophyceae, but others that are unusual for this class. The two flagella are inserted at the apex, but they extend to the side of the cell toward the outside of the colony, here designated as the ventral side. Four basal bodies are present, two of which extend into flagella. Four microtubular rootlets alternate between the functional and accessory basal bodies. In each cell, the two ventral rootlets are nearly parallel, but the dorsal rootlets are more widely divergent. The rootlets alternate between two and four microtubules each. A striated distal fiber connects the two functional basal bodies in the plane of the flagella. Two additional, apparently nonstriated, fibers connect the basal bodies proximal to the distal fiber. Another striated fiber is associated with each four‐membered rootlet near its insertion into the flagellar apparatus. A fine periodic component is associated with each two‐membered rootlet. A rhizoplast‐like structure extends into the cell from each of the functional basal bodies. The arrangement of these components does not reflect the 180° rotational symmetry that is usually present in the Chlorophyceae, but appears to be derived from a more symmetrical ancestor. It is suggested that the form of the flagellar apparatus is associated with the unusual colony structure ofPyro

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1982.tb03209.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

ABSTRACTChlorcorona bohemica(Fott) Fott was previously of uncertain taxonomic affinities. The cell to cell connections, which are one of the chief features of the colony, are composed of wall extensions from adjacent cells. The outgrowths are connected by a fine fibrous component extending from wall to wall. The structure of the wall itself and the cell to cell connections, are similar to those ofPyrobotrys, although the connections in the latter are not as elongated. In addition, the flagellar apparatus ofChlorocoronais very similar to the flagellar apparatus ofPyrobotrys, and unlike that in other Chlorophyceae examined. These features suggest thatChlorcoronais closely related toPyrobotrysand should be referred to the family Spondylomoraceae.

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1982.tb03210.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

ABSTRACTThe distribution of14C among photosynthetic end‐products was examined in eastern Canadian arctic phytoplankton, with particular emphasis on the synthesis of lipids. The pattern of14C distribution for phytoplankton at each of three depths was generally similar among populations from 12 stations. About 18% of the total14C fixed was incorporated into lipids. At one station, phytoplankton were experimentally subjected to temperature and light conditions different from those in situ: lipid‐14C did not exceed 30% of total14C fixed within the temperature range ‐1.0 to 6.0° C and irradiance range 1 to 700 W · m−2. It is suggested that low temperatures and low light intensities, even when, maintained for prolonged periods, are not fully sufficient conditions for eliciting high relative rates of14C incorporation into lipids. It is possible that differences in species composition may be a factor accounting for different patterns of14C distribution between north and south polar phytoplankton under apparently similar environmental c

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1982.tb03211.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

ABSTRACTA cloned axenic culture ofMicrocystisKützing was obtained by combining two procedures: a) the disaggregation of multicellularMicrocystiscolonies by dilution into deionized water, and b) the selective growth ofMicrocystisin agar media containing Na2S, which inhibited or killed the associated contaminants.Microcystisgrowth was stimulated by 0.3–1 mM Na2SO3, but not by 0.1–33 mM Na2SO4. AlthoughMicrocystiscells survived temporary exposure to high Na2S concentrations, their growth was not stimulated by 1×10−5to 1.0 M Na2S. Possible metabolic roles of reduced sulfur compounds are considered.Microcystiscolonies disaggregated to unicells at ionic concentrations below 1 mM for univalent cations, 10–100 μM for the divalent cations, and 3–10 μM for Fe3+. Higher cation concentrations prompted cell aggregation. With>100 mM Fe3+, theMicrocystiscapsule appeared rust‐colored. Neither nonionic solutes nor anions detectably influenced aggregation. These observations suggest cation interactions with theMicrocystiscapsule and are discussed with regard to: a) possible siderochrome activity, cation chelation or luxury uptake of cations, b) the questionability of using cell aggregation as a criterion for identifyingMicrocystisin samples of unknown ionic strength, c) the utility of low ionic strength media in releasing contaminating bacteria from the capsule and in obtaining algal unicells for cloning, and d) a model for cation interactions w

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1982.tb03212.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

ABSTRACTA study of certain fossil, limestone‐forming algae in upper Ordovician beds (Elkhorn and Whitewater Formations of the Richmond Subseries of the Cincinnati Series) in southwestern Ohio and adjacent eastern Indiana culminated with the conclusion that an organism originally described as a sponge, and later placed in the genusGirvanellaNicholson and Etheridge (Cyanochloronta), should in fact be transferred to the genusSolenoporaDybowski (Rhodophycophyta), A calcified reproductive layer was discovered in one of the specimens sectioned. These structures are interpreted as either sporangia or as sporangial chambers, and occur in a sorus rather than a conceptacle type of arrangement. This find has an important bearing on the phylogenetic history of the Solenoporacea

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1982.tb03213.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

ABSTRACTA marine unicellular alga,Nannochloris bacillarisNaumann, was studied with respect to growth, viability and photosynthesis during the steady‐state and also subsequent to changes in the concentration of artificial seawater medium. Cells grew exponentially over the range of 2% to 300% artificial seawater, but more rapidly at lower salinities. In contrast to growth, photosynthesis as measured by both oxygen evolution and bicarbonate photoassimilation was not obviously inhibited for cells adapted within the range of 7% to 200% artificial seawater. In 300% artificial seawater, photosynthesis, especially bicarbonate photoassimilation, was inhibited. Osmotic shocks caused by transferring cells from 200% to 7% artificial seawater had little if any effect on growth, viability or photosynthesis. However, equal shocks in the upward direction (from 7% to 200% artificial seawater) caused long lag phases in growth, totally inhibited photosynthesis and very often led to cell death. Intermediate upward shocks were less deleterious, but did result in lags in growt

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1982.tb03214.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

ABSTRACTThree axenic polar sea ice diatom cultures were subjected to a 30 day simulated summer‐winter transition in which light and temperature were decreased and salinity was increased to mimic seasonal changes previously reported for ice‐covered polar seas. The diatoms responded to these changes by a reduction in cellular metabolism as indicated by: 1) A decline in growth rate and photosynthetic rate; 2) a decrease in cellular ATP; and 3) the storage and subsequent utilization of endogenous carbon reserves. In addition, heterotrophic potential of the three clones increased by as much as 60‐fold. In some cases, the decrease in light intensity characteristic of the onset of polar winter was alone sufficient to trigger these physiological ch

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1982.tb03215.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY