ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1990.00001.x

出版商:Blackwell Science Inc    

年代:1990

数据来源: WILEY

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1990.00004.x

出版商:Blackwell Science Inc    

年代:1990

数据来源: WILEY

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1990.00006.x

出版商:Blackwell Science Inc    

年代:1990

数据来源: WILEY

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1990.00012.x

出版商:Blackwell Science Inc    

年代:1990

数据来源: WILEY

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1990.00018.x

出版商:Blackwell Science Inc    

年代:1990

数据来源: WILEY

摘要:

ABSTRACTThe response of photosynthesis and respiration of the intertidal brown algaFucus spiralisL. to light and temperature at ambient and elevated concentrations of inorganic carbon was investigated. The light‐saturated rate of photosynthesis was greater in air at 15° C and 20° C, but greater in water at 10° C. Light compensation point and Ikwas about 50% lower under submerged relative to emerged conditions, whereas the initial slope of photosynthesis versus irradiance was higher, except at 20° C. Under both submerged and emerged conditions light‐saturated photosynthesis was limited to a similar degree (78%, and 65%, respectively) by the availability of inorganic carbon at naturally occuring concentrations. In air, slight desiccation at tissue water contents of about 96% to 92% caused a stimulation in the rate of net photosynthesis to 110–148% of fully hydrated fronds. At lower water contents the rate of net photosynthesis declined linearly with decreasing water content and became zero at a water content of about 15%. Dark respiration declined linearly with tissue water content and remained positive to a water content of 8%. Upon reimmersion the fronds showed a complete recovery within 35 min following desiccation to a water content of 20–30%. ThusF. spiralisseems to be very tolerant to desiccation. SinceF. spiralisphotosynthesizes effectively in air, even at a higher rate than in water as long as it has not lost a large proportion of its water in desiccation, the alternating exposure to air may be beneficial by increasing the daily carbon gain compared to a fully submerge

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1990.00024.x

出版商:Blackwell Science Inc    

年代:1990

数据来源: WILEY

摘要:

ABSTRACTCulturesof TrichodesmiumNIBB 1067 were grown in the synthetic medium AQUIL with a range of iron added from none to5 × 10−7MFe for 15 days. Chlorophyll‐a, cell counts, and total cell volume were two or three times higher in medium with 10−7M Fe than with no added Fe. Oxygen production rate per chlorophyll‐awas over 60% higher with higher iron. Increased iron stimulated photosynthesis at all irradiances from about 12–250 μE · m−2· s−1. Nitrogen fixation rate, estimated from acetylene reduction, for 10−7and 10−8M Fe cultures was approximately twice that of the cultures with no added Fe. The range of rates of O2production and N2fixation in cultures at the iron concentrations we used were similar to the rates from natural samples ofTrichodesmiumfrom both the Atlantic, and the Pacific oceans. This similarity may allow this clone to be used, with some caution, for future physiological ecology studies. This study demonstrates the importance of iron to photosynthesis and nitrogen fixation and suggests thatTrichodesmiumplays a central role in the biogeochemical cycles of iron

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1990.00030.x

出版商:Blackwell Science Inc    

年代:1990

数据来源: WILEY

摘要:

ABSTRACTPhotosynthesis/photon flux density (PFD) relationships were compared among some of the major components of sparse algal turfs (green endoliths, red crusts, red filaments,Crouania, Sphacelaria)/ fromTague Bay forereef St. Croix, U.S. Virgin Islands. Algal turfs grazed by the sea urchinDiadema antillarumwere 2–10 times more productive per unit chlathan when not grazed by sea urchins. The maximum rate of net photosynthesis (Pnetmax) and saturation PFDs, but not the slope of the light‐limited portion of the curve (α), differed significantly among the algal turf components examined. The hypothesis that increased biomass‐specific primary productivity results from shifts in algal community structure was not supported because the maximum difference in photosynthesis between algal components was only a factor of two, and the less productive components were relatively more abundant under grazing. In the understory, green endoliths exhibited higher α and lower Pnetmax, suggesting shade adaptation. Photon flux density measurements taken with a fiber optic microprobe within the algal turfs indicated that photosynthesis of basal portions of algal filaments and red crusts are light‐limited in ungrazed algal turfs. As self‐shading changes with grazer‐mediated canopy removal, algal sublayers will contribute differentially to whole turf primary

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1990.00036.x

出版商:Blackwell Science Inc    

年代:1990

数据来源: WILEY

摘要:

ABSTRACTThree diatom species,Stephanodiscus hantzschii(Ehr.) Grun.,Asterionella formosaHass. andFragilaria crotonensisKitt. Hass. were isolated from Lake Maarsseveen where they are dominant and show a successional sequence. The physiological responses of each species to temperature and limitation by silicon and phosphorus were determined over the temperature range of 5° to 20° C using short‐term batch culture methods.Stephanodiscus hantzschiihad higher maximum growth rates than the other two species at all temperatures, and the maximum growth rates of all species increased with increasing temperature. Temperature affected not only maximum growth rates but also half‐saturation constants (Ks) and the minimum cell quotas.S. hantzschiihad low silicon requirements for growth under Si‐limiting conditions, andA. formosaandF. crotonensishad higher and nearly identical silicon requirements. The Ksvalues for silicon forS. hantzschiiwere essentially constant from5° to 20° C but variedgreatly for the other two species.A. formosahad the lowest requirements for growth under phosphorus limitation,F. crotonensiswas intermediate andS. hantzschiihad the highest growth requirements for phosphorus. The K1values for phosphorus were constant over the temperature range for bothA. formosaandF. crotonensisand were much higher and variable forS. hantzschii.Nutrient competition experiments were performed in continuous cultures at four temperatures and various Si:P ratios. The results generally, but not always, confirmed the predictions based on the Monod relationships for each species. Results not in agreement with predictions were usually because of similar physiological properties ofA. formosaandF. crotonensisor because of decreased loss rates forF. crotonensisdue to wall growth. In cultures with all three species phosphorus‐limited (Si:P>75),A. formosaoften dominated as predicted, althoughF. crotonensiswas sometimes the most abundant species. As predicted,S. hantzschiinever dominated at high Si:P ratios. At intermediate Si:P ratios whenA. formosaandF. crotonensiswere both Si‐limited andS. hantzschiiP‐limited, all three species coexisted becauseA. formosaandF. crotonensishave almost identical silicon requirements, although sometimesF. crotonensiswas more abundant than predicted. At 10°C the results agreed best with the predictions;A. formosadominated at high Si:P ratios andS. hantzschiidominated as predicted at low Si:P ratios when all three species

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1990.00040.x

出版商:Blackwell Science Inc    

年代:1990

数据来源: WILEY

摘要:

ABSTRACTUnder conditions of starvation for fixed nitrogen, cells of the filamentous cyanobacteriumAnabaena variabilisKütz, degrade much of their protein prior to heterocyst differentiation. Cells starved for a source of fixed nitrogen initially degraded about 2% of their protein per hour; by 24 h after nitrogen stepdown about 40% of the protein was degraded. Most of the acid‐soluble radiolabeled material was excreted into the medium. Proteolysis was completely inhibited by chloramphenicol, by cyanide, or in the dark, hut was only partially inhibited in the presence of dichlorophenyl dimethylurea. Methionine sulfoximine (MSX) (an inhibitor of glutamine synthetase) in the presence of ammonia caused heterocysts to form. MSX treated cells degraded protein; however, the amount of protein degraded was much less than in cells starved for ammonia. Glutamine, which can serve as a nitrogen source for this strain, did not prevent starvation‐induced proteolysis and did not prevent the differentiation of heteroc

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1990.00050.x

出版商:Blackwell Science Inc    

年代:1990

数据来源: WILEY