ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1989.tb00114.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTGametophytes are more abundant thou sporophytes in wave exposed rocky intertidal populations of Iridaea laminarioides Bory in Central Chile. In this study we experimental tested the differential effects of selected ecological factors on karyologically different life history phases. In the field, gametophytes dominated at higher elevation and during summer; tetrasporophytes were most abundant low in the intertidal and during the fall. Laboratory responses correlated with these patterns. Gametophytes exhibited greater desiccation tolerance than tetrasporophytes. Optimum growth of gametophytes occurred at higher temperatures (20°C) and longer photoperiods (16:8 h LD) than sporophytes (15°C and 12:12 h LD). Grazing preferences changed with the developmental stage of the alga, but all herbivores tested had increased preference for diploid tissues as compared to haploid. Number of spores produced with respect to total plant surface, or total rocky surface, or settlement of spores and their germination rate did not show significant differences between phases but showed great variability in space and time. Spontaneous spore release, however, was always higher in cystocarpic than in tetrasporangial thalli. Such a combination of results suggests that some real ecological differences exist between the two life history phases ofI. laminarioides.Such ecological differences permit a prediction of vertical and temporal patterns of distribution for both phases. Horizontal patterns of distribution cannot be explained because the several selection factors probably interact differently in various habitat

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1989.tb00115.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTThe mode of division of vegetative cells, formation of spermatangial parent cells, initiation of the carpogonial branch apparatus, and formation of tetrasporangial initials are homologous developmental processes that are documented for the first time in the type species of the economically important family Gracilariaceae, Gracilaria verrucosa (Hudson) Papenfuss from the British Isles.G. verrucosais characterized by a supporting cell of intercalary origin that bears a 2‐celled carpogonial branch flanked by two sterile branches, direct fusion of cells of sterile branches onto the carpogonium, formation of an extensive carpogonial fusion cell through the incorporation of additional gametophytic cells prior to gonimoblast initiation, gonimoblast initials produced from fusion cell lobes, schizogenous development of the cytocarp cavity, inner gonimoblast cells producing tubular nutritive cells that fuse with cells of the pericarp or floor of the cystocarp, absence of cytologically modified tissue in the floor of the cystocarp, and carposporangial initials produced in clusters or irregular chains. Spermatangial parent cells are generated in flaments from intercalary cortical cells that line an intercellular space forming a ‘pit’ or ‘conceptacle’. Tetrasporangial initials are transformed from terminal cells derived through division of an outer cortical cell. Tetrasporangia are cruciately divided.The Gracilariaceae is removed from Gigartinales and transferred to the new order Gracilariales. Their closest living relatives appear to be agarophytes belonging to the Gelidiales and Ahn

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1989.tb00116.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTThe vegetative organization and reproductive development ofGracilariopsis lemaneiformis(Bory) Dawson, Acleto et Foldvik [includingGracilaria sjoestedtiiKylin] were investigated. Our observations on spermatangial development and post‐fertilization features establish thatGracilariopsisDawson is distinct at the generic level fromGracilariaGreville, and ice propose the resurrection of Gracilariopsis Dawson as a result.Spermatangial parent cells ofGracilariopsisare superficial, initiated in pairs or groups of three by concavo‐convex longitudinal and transverse divisions. Each spermatangial parent cell cuts off a single, colorless spermatangium distally by a transverse division. The female reproductive apparatus consists of a supporting cell that bears a two‐celled carpogonial branch flanked by two sterile branches, as inGracilaria.Likewise, up to six sterile cells fuse with the carpogonium after fertilization to produce a primary fusion cell that generates the gonimoblasts; however, a secondary fusion cell is absent. Inner gonimoblast cells unite with cytologically modified cells of the inner pericarp by means of secondary pit‐connections. Tubular nutritive cells are absent. The gonimoblast consists of a central sterile tissue interconnected throughout by secondary pit‐connections surmounted by a fertile layer composed of carposporangia aligned in straight chains.The distribution ofGracilariopsisis extended to Weste

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1989.tb00117.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTThe vegetative life cycle ofGloeodinium montanumKlebs was examined. In unialgal culturesG. montanumdivided predominantly by binary fission once every 2‐3 weeks. Nuclear division was followed by a delayed cytokinesis producing non‐motileG. montanumcells. When placed in fresh media 2‐4 biflagellated swarmers were formed. The swarmers, although similar in appearance to those ofHemidinium ochraceumLevander (1900), differ from that species in their dimensions. During vegetative reproduction swarmers developed directly into non‐motile vegetativ

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1989.tb00118.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTGrowth, blade shape and blade thickness of young gametophytes ofPorphyra abbottaeKrishnamurthy cultured from conchospores were determined at various combinations of temperature (8, 10, 12° C), photon flux density (17.5, 70, 140 μmol·m‐−2·S−1), nutrient concentration (5, 25, 50, 100% f medium) and water motion (0, 50, 100, 150 rpm). Growth (as surface area) was light‐saturated at 70 μmol· m−2· S−1, light‐inhabited at 140 μmol·m−2· S−1, and nutrient‐saturated an 25% f medium. Temperature had no significant effect on growth. Water motion and nutrients had an interactive effect on growth, with water motion having the greatest effect at the lowest nutrient concentrations. Water motion enhanced growth even at saturating nutrient concentrations.Blade length / width ratio was greater in low light (2.5) than in saturating light (1.9); with increasing water motion the ratio increased from 1.2 to 2.4. Blade thickness (53‐88 μm) was greatest at the highest nutrient concentrations and at the lowest water motion levels. Temperature and light did not have a cons

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1989.tb00119.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTThe light‐saturated rate of photosynthesis in blue light was 50‐100% higher than that in red light for young sporophytes ofLaminaria digitata(Huds.) Lamour., although photosynthetic rates were slightly higher in red than in blue light at low irradiances. Short exposures to low irradiances (e.g. 2 min at 20 μmol · m−2· s−1) of blue light also stimulated the subsequent photosynthesis ofLaminariasporophytes in saturating irradiances of red light but had little effect on photosynthesis in low irradiances of red light. The full stimulatory effect of short exposures to blue light was observed within 5 min of the blue treatment and persisted for at least 15 min in red light or in darkness. Thereafter, the effect began to decline, but some stimulation was still detectable 45 min after the blue treatment. The degree of stimulation was proportional to the logarithm of the photon exposure to blue light over the range 0.15‐2.4 mmol · m−2, and the effectiveness of an exposure to 0.6 mmol · m−2at different wavelengths was high at 402‐475 nm (with a peak at 460‐475 nm) but declined sharply at 475‐497 nm and was minimal at 544‐701 nm. Blue light appears, therefore, to exert a direct effect on the dark reaction of photosynthesis in brown algae, possibly by activating carbon‐fixing enzymes or by stimulating the uptake or transport of in

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1989.tb00120.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTColonies of the stream‐inhabiting cyanobacteriumNostoc parmelioidesKützing often contain a single endosymbiotic dipteran larvaCricotopus nostocicola(Wirth), which induces a morphological change from small, spherical colonies to larger, ear‐shaped colonies. At a current velocity of 0 cm · s−1, whole colonies containing the midge showed overall rates of14CO2uptake and nitrogenase activity that were higher than those when the midge was absent (sphere‐shaped colonies). Spherical colonies incubated at current velocities of 5‐10 cm · s−1did not show higher rates of14CO2or15N2incorporation than those with the larvae (ear‐shaped colonies). Ear‐shaped colonies extended well into regions of higher current velocity, whereas spherical colonies did not. Photosynthesis of ear‐shaped colonies was stimulated by increased current velocity, increased inorganic C and decreased O2concentrations. Moreover, levels of O2at the surface of midge‐inhabited colonies decreased with increased current velocity. The morphological change induced by the larva is detrimental (lowers photosynthesis and N2fixation) in quiescent water but not at current velocities above 10 cm · s−1. This is probably a result of higher diffusion of O2and CO2associated with the

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1989.tb00121.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTThe effects of environmental variables, particularly irradiance, on the sinking rates of phytoplankton were investigated using cultures ofChaetoceros gracilisSchütt and C. flexuosum Mangin in laboratory experiments; these data were compared with results from assemblages in the open ocean and marginal ice zone of the Greenland Sea. In culture experiments both the irradiance under which the diatom was grown and culture growth rate were positively correlated with sinking rates. Sinking rates (ψ) in the Greenland Sea were smallest when determined from chlorophyll (mean ψchl= 0.14 m · d−1) and biogenic silica (ψsi= 0.14 m · d−1) and greatest when determined from particulate carbon (ψc= 0.55 m · d−1) and nitrogen (ψN= 0.64 m · d−1). Field measurements indicated that variations in sinking may be associated with changes in irradiance and nitrate concentrations. Because these factors do not directly affect water density, they must be inducing physiological changes in the cell which affect buoyancy. Although a direct response to a single environmental variable was not always evident, sinking rates were positively correlated with growth rates in the marginal ice zone, further indicating a connection to physiological processes. Estimats of carbon flux at stations with vertically mixed euphotic zones indicated that approximately 30% of the daily primary production sank from the euphotic zone in the form of small particulates. Calculated carbon flux tended to increase with pri

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1989.tb00122.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTThe three‐dimensional structure of the flagellar apparatus in the gonyaulacoid dinoflagellate.Ceratium hirundinellavar.furcoïdes(Schröder) Hub.‐Pest. was determined using serial section electron microscopy. The flagellar apparatus is quite large and consists of several components. The two basal bodies nearly abut at their proximal ends and are separated by an angle of approximately 120° The broad longitudinal microtubular root extends from the cell's left edge of the longitudinal basal body and bends around the sulcal/cingular depression into the cell's left antapical horn. A transverse striated fibrous root is associated with the transverse basal body and a narrow electron dense extension is present along the anterior edge of the transverse basal body. This study revealed severa1 hitherto unreported fibrous components of the flagellar apparatus that link the various microtubular and fibrous components to themselves and to the two striated collars. A large striated fibrous connective links the two striated collars to one another. This fibrous connective is linked to another striated fibrous connective that originates from the longitudinal basal body and lies perpendicular to the longitudinal microtubular root. The readily identifiable and numerous components of theCeratiumflagellar apparatus are comparable to those of other dinoflagellates. The combined presence of well dpveloped striated collars, a striated collar connective, and a basal body angle of approximately 120° indicates that this flagellar apparatus is most like that described for Peridinioid dinoflagellates. Important similarities are also noticeable between this flagellar apparatus and that ofOxyrrhis

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1989.tb00123.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY