摘要:

ABSTRACTSeventeen clones of the ciguatera‐causing dinoflagellateGambierdiscus toxicusAdachi and Fukuyo were acclimated to the same environments over several months. Significant variance components were detected between non‐acclimated and acclimated cultures for cell potencies, yields and reproduction rates. The resultant variance in acclimated potencies among clones was statistically significant(P<0.0001), indicating that potency can be used for genetic comparisons. However, cell potency differences for a clone ofG. toxicusin the acclimated vs. non‐acclimated phases can exceed genetic differences between clones. This stresses the need for a rigorous acclimation process. Caribbean isolates ofG. toxicuswere inherently more toxic than isolates from other areas. One Caribbean clone yielded 55 × 10−4mu (mouse units)·cell−1whereas clones Bermuda, the Bahamas, and Florida ranged from only 1.8 × 10−4mu·cell−1to a maximum of 19.8 × 10−4mu·cell−1. Toxicity decreased with increasing latitude(r =–0.819,P<0.01), indicating that environmental differences probably influenced the potencies. A comparison of acclimated reproduction rates at four light intensities also indicated that genetic differences among clones existed. The resulting reproduction rate/light slopes overlapped, indicating that the clones may be adapted

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1989.00617.x

出版商:Blackwell Science Inc    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTThe fine structure of pit plugs in 90 species of red algae was examined, bringing the total number of species in the continuing survey to 153. The organization of plug caps was confirmed to be a stable, predictable trait within thalli, between generations in heteromorphic life histories, and within the presently recognized orders, with one exception—the Acrochaetiales. Two forms of the outer cap were found in this group, a thin plate, as in the Nemaliales and Palmariales, and a dome, as in Batrachospermales and Corallinales. Variation of pit plug structure indicates that the Acrochaetiales are a heterogeneous assemblage and that pit plugs will be useful in reappraising their systematics. The systematic affinities of several species of uncertain affinities are clarified.Schmitziella endophloeaBornet et Batters is excluded from both orders, Corallinales and Acrochaetiales, with which it previously was allied. Although other ordinal attributions are not precluded by pit plug structure alone, pit plug structure is consistent with placement ofApophlaea sinclairiiHarvey andHildenbrandia rivularis(Liebman) J. Agardh in the Hildenbrandiales,Plagiospora gracilisKuckuck,Schmitziella endophloea,andWurdemannia miniata(Duby) J. Feldmann et Hamel in the Gigartinales, andPseudorhododiscus nipponicusMasuda in the Palmariale

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1989.00625.x

出版商:Blackwell Science Inc    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTThe brown tide picoalgaAureococcusanophagefferens Hargraves et Sieburth was present in approximately equal numbers in 12 large scale (13,000 L) mesocosms at the start of a nutrient addition experiment in June 1985. Increases in abundance in untreated systems mimicked the pattern of bloom development in Narragansett Bay, Rhode Island, the seawater source for the experiment.Aureococcusincreased to maximal values of 2.6 × 109cells. L−1and persisted at high numbers (108cells·L−1) for 7–8 weeks. In nutrient addition tanks, the picoalgae bloomed briefly (1–3 weeks) but rapidly declined to the usual level (∼107cells·L−1) for eukaryotic algae in Narragansett Bay. The decline in picoalgae abundance was followed by an increase in total diatoms in all nutrient treated tanks. Mean picoalgae abundance in the mesocosms and the bay was significantly(P<0.05) and inversely correlated(r =–0.93) with mean concentration of dissolved inorganic nitrogen. The persistence of the brown tide species in control mesocosms and Narragansett Bay appears related to its ability to grow at very low concentrations of dissolved inorganic nitrogen, levels previously shown to lim

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1989.00636.x

出版商:Blackwell Science Inc    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTThe two‐layered, fibrillar cell wall ofMougeotiaC. Agardh sp. consisted of 63.6% non‐cellulosic carbohydrates and 13.4% cellulose. The orientation of cellulose microfibrils in the native cell wall agrees with the multinet growth hypothesis, which has been employed to explain the shift in microfibril orientation from transverse (inner wall) toward axial (outer wall). Monosaccharide analysis of isolated cell walls revealed the presence of ten sugars with glucose, xylose and galactose most abundant. Methylation analysis of the acid‐modified, 1 N NaOH insoluble residue fraction showed that it was composed almost exclusively of 4‐linked glucose, confirming the presence of cellulose. The major hemicellulosic carbohydrate was semi‐purified by DEAE Sephacel (Cl−) anion‐exchange chromatography of the hot 1 N NaOH soluble fraction. This hemicellulose was a xylan consisting of a 4‐xylosyl backbone and 2,4‐xylosyl branch points. The major hot water soluble neutral polysaccharide was identified as a 3‐linked galactan.Mougeotiacell wall composition is similar to that of (Charophyceae) and has homologies with vascular plant cell walls. Our observations support transtructural evidence which suggests that members of the Charophyceae represent the phylogenetic line that gave rise to vascular plants. Therefore, the primary cell walls of vascular plants many have evolved directly from structures typical of the filamentous green algal cell walls found

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1989.00646.x

出版商:Blackwell Science Inc    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTLipophilic pigments were examined in microbial mat communities dominated by cyanobacteria in the intertidal zone and by diatoms in the subtidal and sublittoral zones of Hamelin Pool, Shark Bay, Western Australia. These microbial mats have evolutionary significance because of their similarity to lithified stromatolites from the Proterozoic and Early Paleozoic eras. Fucoxanthin, diatoxanthin, diadinoxanthin, β‐carotene, and chlorophyllsaandccharacterized the diatom mats, whereas cyanobacterial mats contained myxoxanthophyll zeaxanthin, echinenone, β‐carotene, chlorophyllaand, in some cases, sheath pigment. The presence of bacteriochlorophyllawith in the mats suggest a close association of photosynthetic bacteria with diatoms and cyanobacteria. The high carotenoids: chlorophyll a ratios (0.84–2.44 wt/wt) in the diatom mats suggest that carotenoids served a photoprotective function in this high light environment. By contrast, cyanobacterial sheath pigment may have largely supplanted the photoprotective role of carotenoids in the intertid

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1989.00655.x

出版商:Blackwell Science Inc    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTAssimilation of14CO2or14C‐acetate by the hydrocarbon producing algaBotryococcus brauniiKützing was investigated to determine the allocation of incorporated14C among early metabolites of photosynthesis and secondary metabolites. When the cells were exposed to NaH14CO3for 10 sec, over 90% of incorporated14C was detected in phosphoglycerate, suggesting that this alga assimilates inorganic carbon by the C‐3 pathway. The distribution pattern of14C in the number of metabolites revealed that organic acids, neutral sugars and amino acids were first labelled with14C, and, after lag periods of a few minutes, lipids including hydrocarbon were increasingly labelled. Addition of 5 mM acetate to the culture medium did not affect the growth of this alga but enhanced cellular respiration. The incorporation of14CO2into the lipid fraction was stimulated, but net photosynthesis was inhibited by the addition of acetate.14C‐acetate was incorporated into lipids at a very low rate in comparison with the rate of14CO2incorpo

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1989.00662.x

出版商:Blackwell Science Inc    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTElectron microscopy of a “vacuole‐less” mutant ofChlamydomonas moewusiiGerloff revealed the presence of small anterior vacuoles. These vacuoles behaved like contractile vacuoles in wild‐type cells, but they were apparently unable to complete diastole and discharge their contents. When wild‐type and mutant cells were incubated in hypertonic medium, small coated vacuoles persisted in the region where contractile vacuoles form. When these cells were transferred to hypotonic medium, the vacuoles appeared to fill and fuse to form larger vacuoles Shortly after the appearance of full expanded contractile vacuoles, collapsed vacuoles were observed in wild‐type cells suggesting the completion of diastole and the onset of systole. In mutant cells, the initial steps of filling and fusion to form larger vacuoles apparent interactions of vacuoles with the plasma membrane were not observed. New contractile vacuoles accumulated around the nucleus. When fusion of the contractile vacuole with the plasma membrane was blocked by EGTA, a similar accumulation of large vacuoles occurred. Our observations suggest that the contractile‐vacuole mutant ofC. Moewusiiproduces vacuoles which can accumulate excess water as part of the mechanism of osmoregulation but which cannot comp

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1989.00667.x

出版商:Blackwell Science Inc    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTEnrichment cultures of littoral benthic algae from Mono Lake, California, and Abert Lake, Oregon, were grown under conditions of varied salinity and nutrient content. Field‐collected inocula were composed mainly of diatoms and filamentous blue‐green and green algae. The yield of long‐term cultures (30 days) showed tolerance over a broad salinity range (50–150 g·L−1) for Mono Lake‐derived algae. Algae from Abert Lake had a lower range of tolerance (25–100 g·L−1) Organic content and pigment concentrations of algae from both lakes were also reduced above the tolerated salinity level. Within the range of salinity tolerance for Mono Lake algae, initial growth rates and organic content were reduced by increased salinity. The effects of macro‐ and micronutrient enrichment on algal growth in Mono Lake water were also tested. Only nitrogen enrichment (either as ammonium or nitrate) stimulated algal growth. Although the benthic algae cultured here had wide optima for salinity tolerance, the rates of growth and storage were limited by increased salinity within the optimum range. Although the lakes compared had similar species composition, the range and limits of tolerance of the algae were related to salinity of

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1989.00673.x

出版商:Blackwell Science Inc    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTCommunity structure of benthic diatoms in two sandy streams was studied for two summers to assess differences in abundances and species composition among habitats and between years and streams. The greatest differences in abundances (cells·cm−2) were lower abundances on rocks than on sand, whether the sand was clean or covered with flocculent organic material. Relatively little variation in abundances occurred between years and streams. Species composition of diatom communities varied more among habitats and between streams than from year to year. Species composition was most unique in floc‐covered sand when communities in clean and floc‐covered sand, rock, plant, and plankton were compared. Diatom species composition in these sandy streams was most similar on sand and

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1989.00678.x

出版商:Blackwell Science Inc    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTChemical composition and quantitative cytological measurements were determined for the eustigmatophyteNannochloropsissp. Cultures were grown in turbidostats at three irradiance levels: growth‐limiting light, growth‐saturating light and photoinhibiting light. Cellular chlorophyll a content decreased as irradiance level increased, concomitant with a disproportionate reduction in carotenoid content.Nannochloropsissp. grown in saturating light was characterized by a high content of lipid, fatty acids and carbohydrate compared with cells grown in light‐limiting conditions. The increase in cellular lipid content coincided with a reduction in the percentage of eicosapentaenoic acid (C20:5) and arachidonic acid (C20:4), fatty acids that are mainly associated with galactolipids, and with an increase in the relative abundance of palmitic acid (C16:0) and palmitoleic acid (C16:1). At growth limiting light conditions,Nannochloropsissp. preferentially synthesized galactolipids; however, as growth became light saturated, relatively more neutral lipids, mainly triacylglycerols, were synthesized. Changes in lipid content and composition were qualitatively related to changes in cell morphology. Cells grown under low light conditions were characterized by a large relative volume of chloroplast, high surface density of thylakoid membranes and low relative volume of lipid storage bodies. The physiological implications of the changes in cellular lipid composition and ultrastructure are discussed in relation to light/shade adapt

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1989.00686.x

出版商:Blackwell Science Inc    

年代:1989

数据来源: WILEY