摘要:

ABSTRACTThree geographically isolated populations of the giant kelp,Macrocystis pyrifera(L.) C. Ag., were examined for responses to nitrate availability in batch culture experiments using juvenile sporophytes reared from spores in the laboratory. Although maximum rates of nitrate‐saturated growth were similar among groups, there were significant quantitative differences in the response to nitrate limitation that can be related to natural patterns of nutrient availability at these sites. Plants from Santa Catalina Island (most oligotrophic) achieved maximum growth rates at ambient nitrate concentrations that were lower than those for plants from Monterey Bay, California (most eutrophic), or Refugio State Beach (near Santa Barbara, California). Tissue nitrogen and amino acid concentrations were highest in plants cultured from Santa Catalina Island populations at all external nitrate concentrations, suggesting that differences in nitrate requirements for growth may reflect the efficiency of nitrate uptake and assimilation at subsaturating nitrate concentrations. Given the different physical environments from which these plants came, the data suggest that geographically isolated populations ofM. pyriferahave undergone genetic divergence that can be explained by ecotypic adaptation to unique habitat conditions at these site

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1991.00149.x

出版商:Blackwell Science Inc    

年代:1991

数据来源: WILEY

摘要:

ABSTRACTNitrogenase reductase (Fe‐protein) was detected in the marine planktonic cyanobacteriumTrichodesmium.The molecular weight was about 38 kD, as shown by western blotting using anti‐Rhodospirillum rubrumnitrogenase reductase antiserum. The enzyme was confined to a limited number (ca. 10–40%) of randomly distributed trichomes in theTrichodesmiumcolonies, as shown by immunogold localization and transmission electron microscopy. Associated microorganisms had little or no nitrogenase. Nitrogenase showed a diel cycle in localization: present throughout the cytoplasm of cells in N2‐fixing (daytime) colonies but at the periphery of non‐N2‐fixing (nighttime) colonies. This structural arrangement of N2‐fixing trichomes and nitrogenase is novel and different from the previously held paradigm for this and other diazotrophic

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1991.00158.x

出版商:Blackwell Science Inc    

年代:1991

数据来源: WILEY

摘要:

ABSTRACTThe question of what controls gamete release inAscophyllum nodosum(L.) Le Jolis was studied at six sites along the central coast of Maine. Percent release was assessed weekly along randomly marked transect lines in the mid‐intertidal zone. Six independent variables–water temperature at high tide, air temperature at low tide, nitrogen (ammonia, nitrite, and nitrate), and salinity–were measured concurrently. Stepwise multiple regression analysis on the percentage of plants having released gametes revealed that water temperature at high tide accounted for most of the among‐site variation(R2=0.77) in the timing of release. The addition of Julian day increased theR2to 0.82; no other variables were significant. Probit analysis, based on water temperature at high tide, generated an environmentally realistic model for predicting gamete release. The model predicts the onset, midpoint, and termination of gamete release at 6, 10, and 15°C, respectively, and the midpoint at a cumulative water temperature of 358°C. This model has value for developmental studies and, potentially, for reseedingA. nodosumpopulations. Probits may be useful for characterizing phenological events in other fucoids and alga

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1991.00166.x

出版商:Blackwell Science Inc    

年代:1991

数据来源: WILEY

摘要:

ABSTRACTThree clones of marineSynechococcus(WH6501, WH7803, and WH8018) were grown through at least three transfers, at 6‐day intervals, in synthetic medium with total iron concentrations from 10−9to 10−6M. After 6 days of exponential growth, these cultures were harvested, and the cell density and protein and pigment concentrations were measured. Aliquots of the culture were assayed for their carbon fixation rates at two light intensities. Cell density and protein concentration increased by up to 7.8 times over a range of iron from the lowest (10−9M) to the highest concentrations (10−6M). The concentration of chlorophyll‐aand phycobiliproteins showed a wider range of response, increasing by up to 48 times. The carbon fixation rate (per mL of culture) also increased approximately 40 times over the total range of iron concentration. The ranges of these biochemical and physiological responses were much lower than the range of total available iron, which was 1000‐fold, and the range of total cellular iron, which was estimated to be about 160‐fold. This “less‐than‐linear” relationship indicates that the cells are adapting to make more efficient use of iron under limiting conditions. Our results demonstrate characteristics of iron‐limitedSynechococcusthat may be important in understanding the relationships between primary productivity and iron a

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1991.00173.x

出版商:Blackwell Science Inc    

年代:1991

数据来源: WILEY

摘要:

ABSTRACTEmbryos of the fucoid algaPelvetia fastigiata(J. Ag.) DeToni were outplanted into the intertidal zone to assess survival during the physical stress brought about by emersion during a single low tide. Survival varied among microhabitats. Under the adultPelvetiacanopy, survival of 6‐h‐, 24‐h‐, 48‐h‐, and 1‐wk‐old embryos was nearly 100%. Almost all embryos of all ages died in exposed habitats on bare rock or within habitats where thePelvetiacanopy was removed experimentally. However, within red algal turfs, where most juvenilePelvetiaoccur, survival was unusually age specific: 24‐ to 48‐h‐old embryos survived poorly compared to younger (6 h old) or older embryos (1 wk old). Survival patterns reflected microhabitat temperatures during the experiments. The fate of young post‐settlement stages must be studied at these fine temporal and spatial scales to understand the organization of

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1991.00179.x

出版商:Blackwell Science Inc    

年代:1991

数据来源: WILEY

摘要:

ABSTRACTTwo morphologically distinct species of free‐swimming dinoflagellates belonging to the genusGyrodiniumutilize the spine and rhizopodial environments of planktonic foraminifera and colonial radiolaria as microhabitats. Up to 84% of the sarcodines examined in a given population were associated with these dinoflagellates at densities up to 20,000 cells per sarcodine in some radiolarian colonies. Both dinoflagellate species possess chloroplasts, indicating they are capable of autotrophy.14C‐labelling experiments with the radiolarian‐associated dinoflagellate demonstrate that it can take up inorganic carbon under both light and dark conditions. Ultrastructural evidence suggests the foraminiferal dinoflagellate may be capable of phagotrophy. Hence, these algae should be considered mixotrophs. An unusual cytoplasmic extension used for attachment and possibly feeding occurs in the foraminiferal‐associatedGyrodiniumand is documented with electron microscopy. Ultrastructural examination suggests this organelle may be hydrostatically controlled and may be an extension of the sac

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1991.00187.x

出版商:Blackwell Science Inc    

年代:1991

数据来源: WILEY

摘要:

ABSTRACTChemically inert, cylindrical rods positioned in the littoral of two eutrophic Alberta lakes supported higher periphytic algal biomass (measured as total chlorophylla)than nearby morphologically similar culms ofScirpus validusVahl. during most of the summer. Upon initiation of macrophyte senescence, biomass on the two substrata became more similar. Experiments were conducted to investigate the basis for these observations. Whole extracts of intact vegetativeScirpusculms had no effect on periphyton photosynthesis, suggesting that the natural substrata do not produce water‐soluble allelochemicals. Various modifications of the rod surfaces (roughening, wax coating, wax color) were used to test whether surficial properties ofScirpusculms influenced periphyton accumulation. Roughened rods supported levels of biomass similar to those of smooth rods, and both substrata developed structurally complex periphyton communities. Rods covered with paraffin wax had periphyton communities that were lower in biomass and structurally more simple than those on un‐coated rods or onScirpusculms. Coloring of the wax coating had no consistent effect on periphyton accumulation. We hypothesize that the hydrophobic cuticle on actively growingScirpusculms retards the development of precursors for attachment by periphytic algae. Upon senescence of the culm and loss of epidermal integrity, colonization of culm surfaces by periphytic algae may occur in a manner similar to that on artificial substr

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1991.00196.x

出版商:Blackwell Science Inc    

年代:1991

数据来源: WILEY

摘要:

ABSTRACTOptimum nutrient conditions for growth and photosynthesis ofPeridinium gatunense(Nygaard)(Peridinium cinctumfa.westii)were investigated using axenic clones in batch cultures. Selenium (Se) had previously been found to be an indispensable growth factor forP. gatunense.Optimal, suboptimal, and supraoptimal concentrations of HCO3−, N, Ca, Cl, Mg, P, K, S, Si, EDTA‐Na, Fe, Mo, Zn, Mn, Co, Se, B, Br, I, and various trace element mixtures were determined by measuring biomass development, growth rates,14C uptake, and/or oxygen production at various concentration gradients of these elements. The general characteristics of the best formulation, medium‐L 16, relative to other media, are its high content of NaHCO3(1 meq · L−1) and Mo (0.2 μM) but low concentrations of NO3‐N (150 μM), PO4‐P (10 μM), and Fe (0.4 μM), in addition to its content of Se. The total content of trace metals, except for Se, may be reduced to one‐fourth of that in medium‐L 16 without altering the major growth‐promoting properties of the medium. Medium‐L 16 deviated considerably from Lake Kinneret (Israel) water, being much lower in macroelements except for N and P. The pH (8.1–8.4) was in the same range, but the values of conductivity (140 μS · cm−1), alkalinity (1 meq · L−1) and NaCl (200 μM) were>8, 2, and 30 times higher, respectively, in the lake water. Selenium deficiency may limit the

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1991.00207.x

出版商:Blackwell Science Inc    

年代:1991

数据来源: WILEY

摘要:

ABSTRACTThe possible origin of carbon skeletons for ammonium assimilation inCyanidium caldarium(Tilden) Geitler was investigated. N‐sufficient cells assimilated ammonium at a rate of 182 ± 18 μmol·mL packed cell volume (pcv)‐1· h‐1. Removal of CO2or darkening almost immediately prevented ammonium assimilation. N‐limited cells in light assimilated ammonium at a rate of 493 ± 45 μmol · mL pcv‐1· h‐1in the presence of CO2and at a lower rate of 168 ± 17 μmol · mL pcv‐1· h‐1in the absence of CO2. In darkness they assimilated ammonium at a rate of 293 ± 29 μmol · mL pcv‐1h‐1in the presence of CO2, only 60% of the assimilation rate in light. In the absence of CO2, ammonium was assimilated at a similar rate of 325 ± 14 μmol · mL pcv‐1· h‐1. Under the latter conditions, however, assimilation was inhibited after 40 min and ceased after 70 min; it resumed upon resupply of CO2.We suggest that N‐sufficient cells ofC. caldariumobtain carbon skeletons for ammonium assimilation exclusively by photosynthetic reactions. Upon N‐limitation they develop the ability, apparently through derepression or activation of regulatory enzyme system(s), to obtain a consistent quantity of additional carbon skeletons and ATP from mobilization of carbon reserves. This enables the N‐limited cell to assimilate ammonium not only in light but also in darkness, and at a higher rate than N‐sufficient cells. The fact that ammonium assimilation in light occurs at a higher rate than in darkness suggests that ammonium assimilation in light is the sum of both light and dark ammonium assimilation, which implies separate metabolic reactions for the two processes. These results suggest the existence of two distinct and differently controlled pathways in N‐limited cells, but not in N‐sufficient cells, through which carbon skeletons for ammonium assimilation originate. An important role for dark CO2fixation in

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1991.00220.x

出版商:Blackwell Science Inc    

年代:1991

数据来源: WILEY

摘要:

ABSTRACTCell walls of fortyChlorellastrains covering all species of the Algal Collection of Göttingen(C. fuscavar.vacuolata, C. kessleri, C. luteoviridis, C. minutissima, C. protothecoides, C. saccharophila, C. sorokiniana, C. vulgaris, andC. zofingiensis)were compared. The nine species were divided into two groups according to the major sugar in the rigid wall. The first group had a glucose‐mannose‐rigid wall and includedC. fuscavar.vacuolata, C. luteoviridis, C. minutissima, C. protothecoides, C. saccharophila, andC. zofingiensis.The second group, with a glucosamine‐rigid wall, includedC. kessleri, C. sorokiniana, andC. vulgaris. Chlorellastrains of the nine species were further classified by constituent sugars, ruthenium red stainability, and anisotropy of the cell

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1991.00224.x

出版商:Blackwell Science Inc    

年代:1991

数据来源: WILEY