摘要:

ABSTRACTNutrient‐diffusing subsrates were used to investigate nutrient limitation of attached algal assemblages in a shaded stream and an unshaded stream in northern California. Water from both streams contained low levels of nitrogen (<14 μg.L−1) and very low N:P ratios (<2). After 31 days of colonization and growth, attached algal biomass on nitrate‐diffusing substrates was significantly greater than on control substrates in the unshaded stream. Nitrate‐diffusing substrates also supported larger numbers of grazing insects in the unshaded stream. The prostrate diatoms Achnanthes lanceolata Bréb. and Coconeis placentula Ehr. displayed the most consistent positive responses to nitrate enrichment. Nutrient enrichment did not increase the accrual of algal biomass in the shaded stream, but algal biomass was significantly greater at sites located under openings in the tree canopy, implicating light as a limiting factor in this stream. Several Navicula and Nitzschia species, and one unidentified Gomphonema species, were positively associated with higher light levels in the shaded stream. Shade appears to be the primary factor limiting algal growth in small northern California streams, but when its effect is reduced by logging, the inherently low levels of nitrogen in these streams can become

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1988.tb04225.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

ABSTRACTWe attempted to determine the extent to which benthic diatoms contribute to water column primary productivity in shallow‐water estuaries and to elucidate the primary mechanisms responsible for suspending the diatoms. A perliminary study conducted in Mugu Lagoon, California indicated that productivity of ocean water entering the lagoon during flood tides was often several orders of magnitude less than that of the same water mass about 3 h later. Benthic pennate diatoms displaced from the sediments into the water column accounted for the increase. A more detailed study was conducted in Barataria Estuary, Louisiana where, for one month, daily measurements were made of benthic and water column productivity and several other environmental variables. During the month, the relationship between water column and benthic primary productivity varied from strongly negative to weakly negative to positive. K‐systems analysis indicated that factors comprised of wave height, meteorological tides, astronomical tides, and benthic productivity and standing crop accounted for the full range of variation in water column productivity. Benthic pennate diatoms, represented an average of 74% of the diatom taxa in water column samples. We conclude that the primary productivity of well‐mixed shallow estuarine waters is often greatly aumented by displaced benthic

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1988.tb04226.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

ABSTRACTGametes of Pediastrum duplex Meyen were investigated ultrastructurally, with emphasis on the flagellar apparatus. The cells are naked, biflagellate, and measure approximately 2.5 × 8 μm. Distinguishing them from zoospores is their possession of an eyespot and mating structure (the apical cap), and their lack of the peripheral band of cytoplasmic microtubules involved in colony formation. Four featurs of the flagellar apparatus are especially noteworthy: (1) the basal bodies are directly opposed and (2) are interconnected via their cores, (3) the central portion of the distal fiber is elaborated into an unusual ribbed structure which overlies the striated microtubule‐associated component (SMAC) of the two‐membered rootlets, and (4) the X‐rootlets are dissimilar in microtubular number. The smaller X‐rootlet consists of four microtubules in a three over one (3/1) configuration, whereas the larger has been found to be either 5 / 1, 6 / 1 or 7 / 1. The former rootlet extends past the nucleus whereas the latter extends down the opposite side of the cell, passing near the eyespot. The first two of these flagellar apparatus features have been previously noted in other motile cells of the Hydrodictyaceae. Although not specifically mentioned, published micrographs suggest the presence of the latter two as well, which may indicate that all four flagellar apparatus features are characteristics of all motile cells in the Hydrod

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1988.tb04227.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

ABSTRACTThe biovolume and species composition of epipelic algae along sediment depth gradients were sampled seasonally in an acidic oligotrophic lake in the Adirondack Park in New York State. The epipelic algal community of Woods Lake (Herkimer Co., NY) was dominated by diatoms and cyanobacteria. Distinct depth zonation patterns of community composition were evident. Total algal biovolume increased with depth due to a dense cyanobacterial mat on the sediments in deeper water (5–8 m). This mat was dominated by a single species of cyanobacteria, Hapalosiphon pumilus (Kütz.) Kirchner, which accounted for the late summer maximum in total biovolume at 7 m. The shallower (1–4 m) epipelic communities were dominated by diatoms, which showed a spring maximum in total biovolume and were dominated by Fragilaria acidobiontica Charles, Navicula tenuicephala Hust. and N. subtilissim

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1988.tb04228.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

ABSTRACTParamylon is the β‐1, 3‐glucan storage product in euglenoid algae. It is a fibrous crystal that occurs as membrane‐bound granules in the cytosol. The role of the surrounding membrane in paramylon synthesis was investigated by the use of freeze‐etch electron microscopy. When Euglena gracilis Klebs strain Z (Pringsheim) cells were frozen in supercooled liquid nitrogen, the fracture plane primarily was throuh the paramylon membrane. A large intramembranous particle (IMP, mean diam range 5.6‐6.5 nm) and a small IMP (mean diam range 9.6‐10.3 nm) were predominant in both PF (protoplasmic fracture) and EF (exoplasmic fracture) faces of the paramylon membrane. During paramylon synthesis induction, the ratio of small to large IMPs increased in both fracture faces. The IMP density decreased in both fracture faces concomitant to paramylon synthesis increase. These changes in IMP profile and density suggest that the paramylon membrane is involved in the synthesis

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1988.tb04229.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

ABSTRACTThe photosynthetic pigments of 51 species (71 isolates) of tropical and sub‐tropical diatoms from 13 out of 22 families were examined. These were the Thalassiosiraceae, Melosiraceae, Coscinodiscaceae, Rhizosoleniaceae, Biddulphiaceae, Chaetoceraceae, Lithodesmiaceae, Eupodiscaceae, Cymatosiraceae, Diatomaceae, Naviculaceae, Nitzschiaceae and Phaeodactylinaceae. Pigments were analyzed by cellulose and polyethylene thin‐layer chromatography (TLC) and reverse‐phase high‐performance thin‐layer chromatography (HPTLC). All species contained chlorophylls a and c2and the carotenoids carotene, fucoxanthin, diatoxanthin and diadinoxanthin. In addition, 14 species (20 isolates) contained one or more of four minor carotenoids, which were not identified further. One species,Thalassiothrix heteromorpha, contained small amounts of a 19′‐butanoyloxyfucoxanthin‐like pigment, in addition to fucoxanthin.Chlorophyll c2was present in all the diatoms tested and occurred together with chlorophyll c1in 88% of them. The presence of both chlorophylls c1and c2therefore can no longer be considered a universal characteristic of the diatom class. Where chlorophyll c1was absent or occurred in trace amounts only (8 species, 11 isolates), it was usually replaced by a new chlorophyll c pigment designated chlorophyll c3, recently characterized from several prymnesiophytes and one chrysophyte. Exceptions wereNitzschia closterium(CS‐114), which contained only chlorophyll c2, andNitzschia bilobata(CS‐47), which contained all three chlorophylls (c1, c2and c3) in approximately equal amounts. Five species that contained chlorophylls c1and c2also contained chlorophyll c3in trace quantitiesQuantitative pigment analyses of the 71 isolates showed that chlorophyll concentrations ranged from 0.02 μg. 106cells−1in the smallest diatom,Extubocellulus spinifer, to 174.4 μg. 106cells−1in one of the largest diatoms,Coscinodiscussp. under the standard growth conditions used. The mean molar ratio of chlorophylla:cin the 72 isolates was 3.33, with a range of 1.65–7.25.The close similarity between diatom and prymnesiophyte pigmentation was confirmed. Each class has three patterns of pigmentation: viz species with chlorophylls c1and c2and‘true’fucoxanthin, species with chlorophylls c3and c2and‘true’fucoxanthin, and species with chlorophylls

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1988.tb04230.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

ABSTRACTThree features of chloroplast DNA (cpDNA) in plastids isolated fromAcetabularia mediterranea (acetabulum)were analyzed after staining the organelles with the fluorochrome 4′6‐diamidino‐2‐phenyl indole (DAPI): (1) number of chloroplasts exhibiting DNA fluorescence, (2) number of nucleoids per plastid, and (3) nucleoid morphology. In vegetativeAcetabulariacells only half of the total chloroplast population comprising several millions displayed the whitish‐blue fluorescence of the DNA/DAPI complex. This percentage remained stable independent of whether cells were grown in supplemented natural sea water or enriched synthetic sea water. A single nucleoid, widely differing in size and morphology among the organelles, was characteristic of 76–81% of chloroplasts with DNA. Less than 20% contained two nucleoids, and in rare cases three or four nucleoids were present. The pattern of nucleoid numbers followed a Poisson distribution in one experiment, if calculated with the intrinsic mean of the observed data. In two other experiments, however, a significant difference existed between observed and expected values for a Poisson distribution according to the Chisquared test.After secondary enlargement of portions of the negatives, the nucleoids’substructure was disclosed and found to consist of brightly fluorescent spots interspersed by unstained regionsThe lack of cpDNA inAcetabulariacells appears to be brought about by (1) the polarized pattern of growth and translation confined to the apical region of the single cell and (2) the cpDNA arrangement in a single nucleoid acentrically located in the organelle. A scheme for the evolution of a chloroplast population having plastids without DNA is proposed. In theory the lack of cpDNA could arise in each plant, since chloroplasts never evolved a mitotic‐like spindle to ensure the equal distribution of genetic material. The different nucleoid arrangement in most other plants, however, efficiently counteracts this ‘carel

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1988.tb04231.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

ABSTRACTIn previous studies,Laminaria saccharinaL. (Lamour.) sporophytes were found to exhibit two major peaks of sporogenesis and an annual life cycle in Long Island Sound, New York. Young sporophytes were observed shortly after the sporogenesis peaks in early autumn and spring, but most of the mature sporophytes decayed during summer. A new study was conducted to determine if the spring sporogenesis activity contributed to the recruitment observed in autumn through oversummering of gametophytic and juvenile sporophytic stages, as previously suggested. Reproduction and growth in gametophytes and growth in juvenile sporophytes were studied under crossed gradients of light and temperature. Periodic outplantings of substrata seeded with gametophytic and sporophytic stages to the field were conducted to assess actual survival.The optimum temperature and light conditions for gametophyte development, growth and reproduction varied with the time of year meiospores were obtained. Most of this variation was attributable to temperature. A seasonal adaptation to temperature in most developmental stages was observed. Higher temperatures resulted in greater numbers of male gametophytes. Gametophytic stages could develop at all times, suggesting that oversummering in this stage was possible. Juvenile sporophytes had a narrower optimum temperature range and again photon fluence rate contributed little to observed variances. Out planting of sporophytic stages at various times during the year indicated only sporophytes prepared from autumn and winter could survive summer conditions. The thalli of these plants grew rapidly in spring and eroded back to the meristematic region in summer. Most of these plants then quickly became reproductive, resulting in another autumn sporogenesis peak. Gametophytic and sporophytic outplantings prepared from spring meiospores did not survive the summer. Thus, the recruitment observed in autumn can only be the result of the previous autumn's sporogenesis activity. The sporogenous activities of spring and early summer appear to be unimportant, despite the fact that all reproductive indices are superior at those times.

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1988.tb04232.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

ABSTRACTMorphological, demographic and physiological characteristics of Rhode Island intertidal and subtidal populations ofAscophyllum nodosum(L.) Le Jolis were compared in order to examine factors influencing vertical distribution. The two populations had distinctive morphologies: subtidal plants were narrower (more terete) and highly branched compared with intertidal plants. The subtidal population showed signs of necrosis and breakage, which was reflected in significantly shorter mean plant size. High survivorship and low recruitment of both population resulted in relatively constant densities, averaging 91 and 50 plants per m2in the intertidal and subtidal habitats, respectively. Intertidal plants had higher mean annual growth rates (25 cm.yr−1) than subtidal plants (2 cm.yr−1). In general, intertidal plants had higher photosynthetic capacity and nutrient (NO3−) uptake rates than the subtidal population but maintained lower light‐harvesting pigment and tissue nitrogen concentrations. AlthoughAscophyllum nodosumis capable of survival and growth in subtidal as well as intertidal areas, results of this study suggest that different selective pressures affect persistence in each habitat. The scarcity of plants in the subtidal environment may be due to the lack of a critical balance between algal production, allocation of photosynthate, and the negative effects of grazers or comp

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1988.tb04233.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

ABSTRACTUnstable mutants with similar variegated pigmentation were genetically characterized in the red algae. Gracilaria tikvahiae (McLachlan), G. foliifera (Forsk.) Børg. and. G. sjoestedtii (Kylin). All three mutants were green plants with flecks of red tissue where cells had reverted to wild type. The mutant green phenotypes were all recessive, and their genetic behavior in crosses indicated that each was the result of a single, unstable, nuclear gene. Wild‐type revertant tissue was stable one it arose. Revertant plants obtained from spores and revertant fronds taken from variegated plants could not be distinguished from the normal wild type, either phenotypically or genetically. Reversion to wild type occurred during all phases of the life cycle. In crosses between the mutants and wild type, most of the F1tetrasporophytes were heterozygous wild‐type plants, an observation consistent with the recessive nature of the mutations; however, a low frequency of homozygous unstable‐green F1tetrasporophytes was also obttained from these crosses. The molecular basis of neither the mutant instability, i.e. the reversion to wild type, nor of the process producing the unstable green F1tetrasporophytes can yet be deduced, but the phenotype of the plants and genetic results suggest the involvement of transposable genetic el

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1988.tb04234.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY