摘要:

ABSTRACTLaboratory experiments were conducted to study the effects of agitation on growth, cell division, and nucleic acid dynamics of the dinoflagellateGymnodinium nelsoniiMartin. When cultures were placed on an orbital shaker at 100 rpm, cell division was prevented, cellular volume increased up to 1.5 times that of the nonperturbed cells, the form and location of the cell nucleus were modified, and the RNA and DNA concentrations per cell increased up to 10 times those of the controls. When shaking was stopped after 10 days, cells divided immediately at about 2/3 of the division rate of the unshaken populations, and all the altered parameters were restored. If the agitation continued for more than 20 days, total cell death and disintegration occurred. Several cellular types differing in size and shape were observed in the control and shaken cultures. One possible hypothesis for these results is that failure of the cell to divide results from physical disturbance of the microtubule assemblage associated with chromosome separation during mitosis. My study suggests that small‐scale oceanic turbulence of sufficient intensity may inhibit growth of individual dinoflagellate cells, but immediate development of the population may continue when calm weather follows the active mixing perio

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1992.00267.x

出版商:Blackwell Science Inc    

年代:1992

数据来源: WILEY

摘要:

ABSTRACTGeniculate coralline algae are common members of kelp forest communities. The structure provided by their stiff branches greatly influences the abundance and species composition of benthic animals and can affect associated algae by inhibiting recruitment, but the branches are themselves substrate for a large number of other taxa. However, other than qualitative observations, little is known about the within‐site distribution, recruitment, and growth of these algae. We examined the distribution of the dominant corallines at a subtidal site in central California. Abundances ofCalliarthron tuberculosum(Post.&Rupr.) Dawson,Bossiella californicassp.schmittii(Manza) Johans.,Calliarthron cheilosporioidesManza,Corallina vancouveriensisYendo, and unidentifiable juveniles were determined at depths of 10, 15, and 20 m and on horizontal rock, vertical rock, and cobble.Calliarthron tuberculosumwas most abundant (≤39% cover) at all depths, growing primarily on horizontal surfaces. Vertical surfaces and cobbles were dominated byB. californicassp.schmittii(40 and 15% cover, respectively). These two most abundant species had the highest cover at 15 m.Calliarthron cheilosporioidesandC. vancouveriensiswere relatively rare (<1% cover) and generally grew on horizontal rocks and at shallower depths. Unidentified juveniles were also rare and occurred mainly on horizontal rocks and cobbles at 20 m.The settlement and growth rates of coralline crusts and the initiation and growth rates of young erect fronds from these crusts were determined in clearings made in the spring and fall at the three depths. Crust densities and diameters were highest at 10 m and in spring clearings. Settlement and growth tended to decrease with increasing depth. Trends were similar in fall clearings, but initial settlement was lower. Initiation and growth of fronds decreased with depth and were also higher in fall clearings. These variations in depth and substrata distribution, as well as settlement and growth, suggest there is considerable variation in the population biology between species in this group of subtidal pla

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1992.00273.x

出版商:Blackwell Science Inc    

年代:1992

数据来源: WILEY

摘要:

ABSTRACTRemote sensing of highly turbid finfish aquaculture impoundments using the Calibrated Airborne Multispectral Scanner (CAMS) mounted on a Lear jet flown at 900 m was conducted in central Mississippi on 16 May 1990. Concurrentin situdata consisted of phytoplankton pigment concentrations and standing crop, water color, turbidity, and surface‐water temperature. Surface and near‐surface assemblages of cyanophytes and chlorophytes varied dramatically among impoundments; total chlorophyll concentrations and standing crop values ranged from 8 to 483 mg·m−3and 8.0 × 102to 2.2 × 106cells‐mL−1, respectively. Regression models fit to CAMS data provided reliable estimates for and produced accurate digital cartographs of total chlorophyll and carotenoid concentrations, phytoplankton standing crop, and turbidity. Although a model to effectively estimatein situc‐phycocyanin concentrations was not identified, the lack of a suitable model may have resulted from variability of pigment extraction during quantification rather than failure of remotely sensed imagery to detect c‐phycocyanin. Models derived from imagery of impoundments directly beneath the aircraft sufficiently describedin situparameters in imagery of adjacent series of impoundments not directly below the aircraft. High‐resolution airborne remote sensing provides a means for monitoring local phytoplankton dynamics in temporal and spatial scales analogous to biotic and abiotic processes affecting such dynamics and necessary for applications to ecological research and fisheries or aquac

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1992.00281.x

出版商:Blackwell Science Inc    

年代:1992

数据来源: WILEY

摘要:

ABSTRACTThree strains ofScenedesmus acutus f. alternansHortobagyi with markedly different sensitivities to copper were examined to determine the relative importance of cellular polyphosphate content on acute copper toxicity to photosynthesis. By manipulating the phosphate concentration in semicontinuous cultures, the response of each strain was assessed at three cellular phosphorus states: P‐loaded, P‐sufficient, and P‐deficient. The results demonstrated the importance of cellular polyphosphate content in reducing the toxic effect of copper on photosynthesis; the greater the cellular P content, the less inhibition of photosynthesis occurred during copper exposure. This relationship was evident for both Cu‐tolerant strains (XCu and B‐4) and a Cu‐sensitive strain (X72). The ranges of response to 9.9 μM Cu (measured as the percentage of control rate of photosynthesis within strains) were, from P‐loaded to P‐deficient cells, X72, 78–54%; XCu, 95–77%; and B‐4, 99–94%. The data suggest that polyphosphate plays a passive role in protecting cells from copper; however, with respect to the mechanism of Cu tolerance, polyphosphate appeared to be relatively unimportant because the sensitivity of the Cu‐tolerant strains showed less dependence on cellular polyphosphate than d

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1992.00291.x

出版商:Blackwell Science Inc    

年代:1992

数据来源: WILEY

摘要:

ABSTRACTMacrophytic members of the Rhodophyta, which were grown under controlled conditions, were analyzed for their fatty acid distribution. Significant differences were found between some species of the Gelidiales and Gracilariales. Two dominant polyunsaturated fatty acids of the 20 carbon chain group, 20:4ω6 and 20:5ω3, were found in all the Gelidiales species, whereas only 20:4ω6 was found in the Gracilariales species. An inverse relationship between the content of these two polyunsaturated fatty acids in Gelidiales species and among the two groups of species are reported and discussed. All other fatty acid characteristics were more or less similar in these two orders. We cannot draw any solid conclusion about the relationship betweenGracilariopsiscf.lemaneiformis(formerlyGracilaria lemaneiformis) and the genusGracilaria, since our results (the existence of 20:4ω6 and 20:5ω3 inGracilariopsis) contradict results found by other researchers. The diverse growth conditions of photon flux density and temperature caused some differences in the distribution of the fatty acids in each species. These differences could not explain the different results in similar species reported in the litera

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1992.00299.x

出版商:Blackwell Science Inc    

年代:1992

数据来源: WILEY

摘要:

ABSTRACTMass spectrometric analysis of oxygen uptake and evolution in the light by marineSynechococcusWH7803 indicated that the respiration rate was near zero at low irradiance levels but increased significantly at high irradiances. The light intensity (Ir) at which oxygen uptake began to increase with increasing light intensity depended on the growth irradiance of the culture. In each case, Ircoincided with the minimum light intensity for saturation of carbon assimilation (Ik). At irradiances>Ir, net oxygen evolution rates paralleled carbon assimilation rates. Oxygen uptake at high light intensities was inhibited by DCMU, indicating that oxygen uptake was due to Mehler reaction activity. The onset of Mehler activity at Iksupports the idea that oxygen becomes an alternative sink for electrons from photosystem I when NADPH turnover is limited by the capacity of the dark reactions to utilize reductant.

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1992.00304.x

出版商:Blackwell Science Inc    

年代:1992

数据来源: WILEY

摘要:

ABSTRACTThe biosynthesis of the light‐harvesting complex (LHC) polypeptides of the green flagellateMantoniella squamata(Manton et Parke) Desikachary (Micromonadophyceae, Chlorophyta) was examined byin vivopolypeptide labeling and immunoprecipitation ofin vitrotranslation products. Using protein synthesis inhibitors, the LHC polypeptides were shown to be synthesized on 80S cytoplasmic ribosomes and not in the chloroplasts of cells. Poly (A)+ RNA was isolated and proteins were synthesized by a rabbit reticulocyte lysate system, with antisera raised againstM. squamataLHC used for immunoprecipitation from the translation products. One polypeptide 3‐5 kDa larger than mature LHC polypeptides was immunoprecipitated. These studies indicate that although the LHC ofM. squamatais quite different from the LHC of most green plants, the LHC polypeptides are synthesized as precursors in the cytoplasm of the cell and suggest that the genes encoding these polypeptides are located in the nucl

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1992.00309.x

出版商:Blackwell Science Inc    

年代:1992

数据来源: WILEY

摘要:

ABSTRACTThe endoparasitic dinoflagellateAmoebophrya ceratiiKoeppen occurs in coastal waters of Nova Scotia within cells of two dinoflagellate hosts, aScrippsiellaspecies (probablyS. trochoidea(Stein) Loeb. III) andDino‐physis norvegicaClaparede&Lachman. We describe the development of the endoparasitic stage (the trophont) ofA. ceratiiwithin host cells using light and electron microscopy. After entry into the host, the trophont grows and expands until most of the host cell is occupied by the parasite. Growth is marked by a proliferation of trophont nuclei and flagella and by the formation of numerous lobes, each of which possesses a characteristic dinoflagellate amphiesma. The mature endoparasitic trophont is recognized at the light microscopic level as a beehive‐shaped structure that consists of numerous lobes of the developing motile sporont cells and a mastigocoel cavity containing the sporont flage

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1992.00312.x

出版商:Blackwell Science Inc    

年代:1992

数据来源: WILEY

摘要:

ABSTRACTTrichodesmium thiebautiiGomont, a marine planktonic diazotrophic cyanobacterium, has an unusual subcellular arrangement. To identify subcellular structures related to photosynthesis, antibodies against phycoerythrin, phycocyanin, and ribulose 1,5‐bisphosphate carboxylase/oxygenase (Rubisco) were used together with an immuno‐gold labeling technique and electron microscopy. Thylakoid membranes, identified by transmission electron microscopy and phycobiliprotein labeling, were arranged as a loose network throughout all cells. Rubisco showed a particularly intense localization in medium electron‐dense polyhedral bodies, therefore identified as carboxysomes. The average density of the carboxysomal Rubisco label was about five times higher than that in the cytoplasm. The carboxysomes (4–11 per cell section) were scattered throughout the cytoplasm. These data, together with those obtained from double immunolabeling experiments using nitrogenase (Fe‐protein) and Rubisco antibodies, revealed thatTrichodesmiumcontains both N2‐ and CO2‐fixing proteins within the same cell. This is in contrast to the previous concept of a spatial segregation of the two processes inTrichodesmiumand demonstrate that nitrogenase‐containing cells are not comparable to heterocysts

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1992.00320.x

出版商:Blackwell Science Inc    

年代:1992

数据来源: WILEY

摘要:

ABSTRACTCarrageenan, the major cell wall carbohydrate of certain red algae, is variable in structure and gelling properties. Sequence types include gelling (kappa and iota) and nongelling (lambda) types in addition to precursors, often in hybrid molecules containing more than one precursor and/or sequence type. Molecular markers to subunits were needed to study carrageenan synthesis, cell wall organization, and the relationship between structure and function. Monoclonal antibodies were produced to carrageenan, and their specificities were determined by competitive enzyme immunoassay. Antibodies were identified with specificities related to kappa, iota, and lambda carrageenan. The patterns of immunofluorescence localization onKappaphycus alvarezii = Eucheuma alvareziivar.tambalang(Doty) sections were distinctive for each antibody. The antibody to a kappa‐related epitope labeled mature tissue strongly; antibodies to an iota‐related epitope and a lambda‐related epitope labeled weakly, consistent with the kappa‐enriched carrageenan produced by this alga. Kappa‐related epitopes were distributed throughout the wall and matrix, whereas iota‐related epitopes were concentrated in the middle lamella. Lambda‐related epitopes were localized primarily at the plant cuticle where kappa and iota antigens were lacking. An antibody appeared to be specific for a precursor of the gelling subunits because it showed maximal wall and intracellular labeling at the youngest developmental stage. All antibodies labeled intracellular inclusions in the transition zone between the epidermis and medulla during the development of medullary cells from the peripheral meristem in young branches. The results demonstrate the intracellular synthesis of epitopes related to all major carrageenan subunits and their differential extracellular

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1992.00328.x

出版商:Blackwell Science Inc    

年代:1992

数据来源: WILEY