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1.
A method is described for the rapid separation of carbonic anhydrase(CA) isozymes by cellulose acetate membrane electrophoresisin which CA activity is detected using the pH-indicating dye,bromcresol purple. This method can detect bovine erythrocyteCA in a 0.3 mm3 sample applied at a concentration of 100 ngcm3 (total of 30 pg applied) while at higher concentrationsthree isozymes were observed. It was found, using a potentiometrictechnique, that intact cells of Anabaena flos-aquae (Cyanophyceae)and Chlorella ellipsoidea had no detectable activity while C.saccharophila and Chlamydomonas reinhardtii (Chlorophyceae)had external CA activity. CA activity of the extracts suggestedthe presence of internal CA in all species. After electrophoresisit was found that C. saccharophila and C. reinhardtii had twoisozymes while A. flos-aquae and C. ellipsoidea had only a singledetectable band. Spinach had up to five detectable isozymesthat were difficult to resolve. Incubation of spinach extractwith the CA inhibitor ClO4 (500 mol m3) inhibitedCA activity by 90% using the potentiometric technique, but afterelectrophoresis had no detectable effect. This technique isuseful in identifying isozymes that are substantially differentin electrical charge and in monitoring CA isozyme activity duringenzyme purification. Key words: Carbonic anhydrase, isozymes, cyanobacteria, microalgae, spinach 相似文献
2.
Mesozooplankton grazing under conditions of extreme eutrophication in Guanabara Bay, Brazil 总被引:1,自引:0,他引:1
Schwamborn R.; Bonecker S. L. C.; Galvao I. B.; Silva T. A.; Neumann-Leitao S. 《Journal of plankton research》2004,26(9):983-992
The objective of the present study was to quantify mesozooplanktongrazing in the eutrophic waters of Guanabara Bay. Mesozooplankton(>200 µm) was dominated by the copepods Acartia lilljeborgi,Acartia tonsa, Parvocalanus crassirostris and Paracalanus furcatus.Dinoflagellates, specifically the species Prorocentrum triestinum,were an important group for mesozooplankton nutrition, beingingested in significant amounts during all experiments. On average,12.3 ± 2.9 P. triestinum cells were ingested copepod1min1 (other dinoflagellates: 11 ± 8 cells copepod1min1). Filamentous cyanophyceae and nanoplankton wereingested in one experiment each, but the mesozooplankton communitygenerally preferred dinoflagellates to these groups, which werealways abundant in the water column. Euglenophyceae were notingested, although they dominated in one experiment. Mesozooplanktoningested, on average, only 0.2% of the nano- and microplanktonbiomass per day. The results suggest that grazing was not acontrolling process for the nano- and microplankton communityin the study area. Addition of zoeae larvae of Chasmagnatusgranulata (Decapoda: Brachyura: Grapsidae) in one experimenthad a significant effect on the mortality of adult copepods,probably due to a predatorprey relationship. 相似文献
3.
Biomass, feeding and production of Noctiluca scintillans in the Seto Inland Sea, Japan 总被引:1,自引:0,他引:1
The abundance and biomass of the large heterotrophic dinoflagellateNoctiluca scintillans, together with the changes in its potentialprey items, were monitored in the Seto Inland Sea, Japan, duringsummer 1997 (17 July-11 August). Growth and grazing rates ofNscintillans fed natural plankton populations were also measuredeight and seven times, respectively, during the survey period.The abundance and biomass of N scintillans averaged over thewater column (19 m) were in the range 1345 cells 11(temporalaverage = 93 cell11) and 0.149.6 µg C l1(temporalaverage = 13.8 µg C l1; three times higher thanthat of calanoid copepods during the same period). Noctilucascintillans populations followed the changes in phytoplankton:N.scintillans biomass was increasing during the period of diatomblooms and was at a plateau or decreasing during periods oflow chlorophyll a. The growth rates of N.scintillans (µ)were also consistent with the wax and wane of the N.scintillanspopulation: N.scintillans showed highest growth rates duringdiatom blooms. A simple relationship between µ and chlorophylla concentration was established, and the production of N.scintillanswas estimated using this relationship and the measured biomass.The estimated production averaged over the water column wasin the range >0.15.2 µg C l1 day1(temporalaverage = 1.4 µg C l1 day1; 64% of the productionof calanoid copepods during the same period). Diatom clearancerates by N.scintillans were in the range 0.100.35 mlcell1 day1, and the phytoplankton population clearanceby N.scintillans was >12% day1. Thus, although thefeeding pressure of N.scintillans on phytoplankton standingstock was low, N.scintillans was an important member of themesozooplank-ton in terms of biomass and production in the SetoInland Sea during summer. 相似文献
4.
The relationship between chlorophyll a (Chl a) and primary productivity(PP) in the uppermost water layer and the water column-based(015 m) integral values of those variables were examinedusing measurements taken in Lake Kinneret (Israel) from 1990to 2003. In 81% of all Chl a profiles examined, the distributionwas fairly uniform within the entire 015 m water column,and 12.3% of instances showed a prominent subsurface maximum,when the lake phytoplankton was dominated by the dinoflagellatePeridinium gatunense. Chl a can be reliably estimated by remotesensing techniques in the productive and turbid water of LakeKinneret, since Chl a concentration at surface layers can beextrapolated to the entire water column. Light vertical attenuationcoefficient average for wavelengths from 400 to 700 nm, Kd,ranged from 0.203 to 1.954 m1 and showed high degreeof temporal variation. The maximal rate of photosynthetic efficiency,PBopt [average 3.16 (±1.50)], ranged from 0.25 to 8.85mg C m3 h1 mg Chl a1. Using measured dataof Chl a, PBopt, and light as an input, a simple depth-integratedPP model allowed plausible simulation of PP. However, a lackof correlation between photosynthetic activity and temperature(or other variable with remotely sensed potential) renders theuse of models that require input of photosynthetic efficiencyto calculate integrated PP of little value in the case of productiveand turbid Lake Kinneret. 相似文献
5.
A paralytic shellfish poisoning (PSP) incident caused by consumptionof the mussel Mytilus edulis occurred for the first time inKorea in April 1986. Weekly water samplings were carried Outduring the period from 7 March to 21 April 1989 in Chinhae Bay,Korea, in order to identify the causative organism. The temperaturecharacteristics of the water column indicated three differenthydrological regimes: well mixed (up to 7 March), weakly stratified(1731 March) and stratified (721 April). Toxicityof the phytoplankton was detected during the weakly stratifiedperiod, but only in the 1050 p.m phytoplankton size fraction.This study presents the occurrence of the toxigenic dinoflagellateAlexandrium tamarense, which is a causative organism of PSP,in Korean coastal waters. Its biomass varied at different depthsin the water column, ranging from 200 to 8000 cells 11in the water column. The weekly fluctuation of A.tamarense toxicitywas similar to that of mussel toxicity.
1 Present address: Department of Biology, College of NaturalSciences, Hanyang University, Seoul 133-791, Korea 相似文献
6.
Koike Kazuhiko; Horie Yoshifumi; Suzuki Toshiyuki; Kobiyama Atsushi; Kurihara Kenji; Takagi Kenji; Kaga Shin-Nosuke; Oshima Yasukatsu 《Journal of plankton research》2006,28(1):103-112
In 2003, an occurrence of the yessotoxin (YTX)-producing dinoflagellate,Protoceratium reticulatum, and resultant toxin concentrationin scallops was monitored in Okkirai Bay, northern Japan. Theoccurrence peaked after 1 July and reached a maximum density(400 cells L1) on 16 July. It occurred over a wide rangeof water temperature and inorganic nutrient concentrations andwas tolerant of a broad range of environmental conditions. Hydrologicalparameters were monitored, and it was obvious that P. reticulatumflourished under low salinity (30.5932.60) and occurredat highest density in the surface layer (05 m depth)where effects from rainfall were greatest. In addition, dinoflagellatedensity increase and decrease was well correlated with inflowsof oceanic water into the bay. Thus, it can be assumed thatthe oceanic inflows may cause initial population increases (e.g.excystment or input of a seed population), withresultant growth in rain-affected waters and subsequent spreadthroughout the entire bay via water movement. YTX and 45-OHYTXconcentrations in scallops reached maximum levels (0.79 µgg1 and 0.44 µg g1 of digestive gland, respectively)2 weeks after the maximum cell density of P. reticulatum, andhigh levels of the toxin continued for a month. Low levels ofthe toxin were detected even during periods when cells werenot observed. 相似文献
7.
Copepod egg production, moulting and growth rates, and secondary production, in the Skagerrak in August 1988 总被引:5,自引:0,他引:5
Peterson William T.; Tiselius Peter; Kiorboe Thomas 《Journal of plankton research》1991,13(1):131-154
Measurements of hydrography, chlorophyll, moulting rates ofjuvenile copepods and egg production rates of adult female copepodswere made at eight stations along a transect across the Skagerrak.The goals of the study were to determine (i) if there were correlationsbetween spatial variations in hydrography, phytoplankton andcopepod production rates, (ii) if copepod egg production rateswere correlated with juvenile growth rates, and (iii) if therewas evidence of food-niche separation among co-occumng femalecopepods The 200 km wide Skagerrak had a stratified water columnin the center and a mixed water column along the margins. Suchspatial variations should lead to a dominance of small phytoplanktoncells in the center and large cells along the margins; however,during our study blooms of Gyrodinium aureolum and Ceratium(three species) masked any locally driven differences in cellsize: 50% of chla was >11 µm, 5% in the 1150µm fraction and 45% <50 µm. averaged for allstations. Chlorophyll ranged from 0.2 to 2.5 µg l1at most depths and stations. Specific growth rates of copepodsaveraged 0.10 day1 for adult females and 0.27 day1for juveniles The latter is similar to maximum rates known fromlaboratory studies, thus were probably not food-limited. Eggproduction rates were food-limited with the degree of limitationvarying among species: 75% of maximum for Centropages typicus, 50% for Calanus finmarchicus, 30% for Paracalanus parvus and 15% for Acartia longiremis and Temora longicornis. Thedegree of limitation was unrelated to female body size suggestingfood-niche separation among adults. Copepod production, summedover all species, ranged from 3 to 8 mg carbon m3day1and averaged 4.6 mg carbon m1 day1. Egg productionaccounted for 25% of the total. 相似文献
8.
Pseudobalanion plancioracum was the most abundant ciliate speciesin the pelagic zone of Lake Constance, FRG, over a 3 year period.Annual averages accounted for 30, 35 and 43% of total ciliatenumbers in the uppermost 20 m of the water column in 1987, 1988and 1989 respectively. Highest cell numbers were observed inearly spring, simultaneously with the first phytoplankton maximum.The small ciliate (mean length 15 µm, mean cell volume1300 µm3) is a raptorial feeder and predominantly consumesphytoplankton. In laboratory cultures, P planctonicum grew wellon a diet of Rhodomonas sp. (Cryptophyceae). Maximum growthrates increased from 0.46 day1 at 5 5°C to 1.52 day1at 18.5° C, while temperatures above 21°C were lethal.Depending on food concentration, 0.24.4 Rhodomonas cellswere ingested per ciliate and hour. 相似文献
9.
Photoadaptation in Antarctic phytopfankton: variations in growth rate, chemical composition and P versus I curves 总被引:1,自引:0,他引:1
The response of phytoplankton to variations in the light regimewas studied during the VULCAN and ACDA cruises in the Antarctic.Unenriched batch cultures of 1219 days' duration reachedchl concentrations of 1050 µg1 and exhibitedexponential growth rates, with the maximal rate being 0.41 doubl,day1. Ice edge algae exhibited maximum growth rates atphoton flux densities (PFD) of 30100 µE m2S1and the growth rate was reduced by about 30% at 5001000µE m2S1 The chl/C ratio ranged between 0.004and 0.018, with the lowest ratios at PFDs above 500 µEm2S1 chl/C ratios were also below maximum at PFDsbelow 4050 µE m2S1 The C:N:P ratioswere close to the Redfield ratios; the Si/C ratio averaged 0.16(atoms), and the ATP/C ratio averaged from 0.0024 to 0.0050in different culture senes. When thawed after having been frozenfor 10 days, shade-adapted cultures were in a much better conditionthan sun-adapted ones. P versus I data showed that the maximumassimilation number varied from 0.75 to 4.4 µg C (µgchl)1h1. It varied inversely with the chl/C ratio;therefore the maximum carbon turnover rate varied little betweensamples (0.024/0.035 h1). Low biomass communities exhibitedrelatively high values for (the initial slope of P versus Icurves), low values for 1sat (160330 µE m2S1),and they were susceptible to photoinhibition. In contrast, communitiesdominated by Odontella weissflogii exhibited low values for, a high value for Isat (560 µE m2S1 andthey tolerated high PFDs. The photo-adaptational status of thephytoplankton in natural water samples is discussed relativeto the profile of water column stability and mixing processes. 相似文献
10.
Growth of Ceratium hirundinella in a subtropical Australian reservoir: the role of vertical migration 总被引:3,自引:0,他引:3
Whittington John; Sherman Bradford; Green Damian; Oliver Roderick L. 《Journal of plankton research》2000,22(6):1025-1045
A study into the photophysiology, growth and migration of Ceratiumhirundinella in Chaffey Reservoir in subtropical northern NewSouth Wales, Australia, revealed that a proportion of cellsformed subsurface accumulations at depths that optimized lightintensity (212552 µmol photons m2 s1)for photosynthesis and cell growth. At high incident irradiance,Ceratium migrated downwards from the near-surface waters, avoidinghigh-light-induced, slow-recovering non-photochemical quenchingof photosystem II. Overnight deepening of the surface mixedlayer by convective cooling produced homogeneous distributionsof Ceratium with a significant proportion of the populationbelow the depth where light saturation of photosynthesis occurred.Ceratium migrated towards the surface from suboptimal lightintensities, at a velocity of 1.62.7 x 104 m s1.Subsurface accumulations occurred under a variety of turbulenceintensities; however, accumulation was significantly reducedwhen the turbulent velocity scale in the mixed layer was >5x 103 m s1, beyond which turbulent diffusion dominatedadvection by swimming. The formation of subsurface accumulationswith increased computed water column integral photosynthesisby 35% compared to a uniform cell distribution. 相似文献
11.
Results are presented of size-fractionated primary productionstudies conducted in the vicinity of the Subtropical Front (STF),an adjacent warm-core eddy, and in Sub-antarctic waters duringthe third South African Antarctic Marine Ecosystem Study (SAAMESIII) in austral winter (June/July) 1993. Throughout the investigation,total chlorophyll (Chl a) biomass and production were dominatedby small nano- and picophytoplankton. No distinct patterns intotal Chl a were evident. At stations (n = 7) occupied in thevicinity of the STF, total integrated biomass values rangedfrom 31 to 53 mg Chl a m2. In the vicinity of the eddy,integrated biomass at the eddy edge (n = 3) ranged from 24 to54 mg Chl a m2 and from 32 to 43 mg Chl a m2 inthe eddy (n = 2). At the station occupied in the Sub-antarcticwaters, total integrated biomass was 43 mg Chl a m2.Total daily integrated production was highest at stations occupiedin the vicinity of the STF and at the eddy edge. Here, totalintegrated production ranged from 150 to 423 mg C m2day1 and from 244 to 326mg C m2 day1, respectively.In the eddy centre, total integrated production varied between134 and 156 mg C m2 day1. At the station occupiedin the Sub-antarctic waters, the lowest integrated production(141 mg C m2 day1) during the entire survey wasrecorded. Availability of macronutrients did not appear to limittotal production. However, the low silicate concentrations duringthe survey may account for the predominance of small nano- andpicophytoplankton. Differences in production rates between theeddy edge and eddy core were related to water column stability.In contrast, at stations occupied in the vicinity of the STF,the control of phytoplankton production appears to be relatedto several processes, including water column stability and,possibly, iron availability. 相似文献
12.
Cyst formation: an important mechanism for the termination of Scrippsiella trochoidea (Dinophyceae) bloom 总被引:1,自引:0,他引:1
A sediment trap study was conducted at Daya Bay, South ChinaSea, to investigate the relationships between encystment andpopulation dynamics of Scrippsiella trochoidea from December1999 to January 2001. A dense bloom of S. trochoidea occurredduring the study period from August to September 2000, withthe maximum cell number of 3.18 x 104 cells mL1.Two morphotypes of cysts, one with a thick calcareous wall (calcifiedcyst) and another without the obvious calcareous cover (non-calcifiedcyst), were observed during this investigation. The morphologicaland excystment characteristics of these two cyst types werestudied as well. Mass encystments of S. trochoidea, with themaximum of 3.05 x 105 cysts m2 d1for calcified cyst, and 1.54 x 107 cysts m2 d1for non-calcified cyst, coincided with the maximum abundanceof the vegetative cells. Encystment caused the transfer of atotal of 2.244.49 x 108 cells m2 vegetativecells from the water column to the sea bottom during the bloomand resulted in a considerable loss of the bloom population.High assemblages of cysts of S. trochoidea were detected inthe surface sediments as well. This rich seed bedin the surface sediments caused by the high efficiency of encystmentafter blooms acting as a benthic reservoir for future vegetativepopulation, together with the short dormant period (1526days) and high germination rate (5090%), may explainthe repeated occurrence of S. trochoidea blooms in Daya Bay. 相似文献
13.
Development and fate of Eutreptiella gymnastica bloom in nutrient-enriched enclosures in the coastal Baltic Sea 总被引:1,自引:0,他引:1
Response of the phytoplankton community to bottom-up (nutrients,organic carbon source) and top-down (fish) manipulations, bothsingly and together, were studied daily during a 3 week periodin July 1993 by using eight 50 m3 mesocosms in the coastal northernBaltic Sea. Nutrient additions (once per week) invoked a seriesof blooms of Eutreptiella gymnastica Throndsen (Euglenophyceae)(up to 13 x 103 cells ml1) which formed the major part(6090%) of the total autotrophic biomass. After rapiddepletion of nutrients (23 days) from the surface layer(06 m) downwards migration and a subsequent peak of E.gymnasticain the lower part of the water columns (612 m) followed.Settled material collected from the bottom of the enclosurescontained a considerable amount of E.gymnastica cells and restingcysts. Nevertheless, sinking loss rates of E.gymnastica wereestimated to be less than 1% day1 of the suspended cellnumbers. The fate of E.gymnastica blooms was estimated to begrazing through mesozooplankton. However, provided the nutrientsare plentiful in the water column, the growth potential of E.gymnasticaappears to exceed the ambient grazing pressure. If the nutrientsbecome depleted, it seems to be effectively controlled by mesozooplanktongrazing, which is probably limiting the likelihood of massiveE.gymnastica blooms in the coastal Baltic Sea. Our study suggeststhat E.gymnastica appears to be a fast-growing fugitive (bloom)species with flexible behavioural (vertical migration) and lifehistory (cyst formation) adaptations which is able to exertdominant role and direct trophic relations similar to otherbloom species adapted for decaying turbulence and high nutrientenvironments. 相似文献
14.
Distinct roles of PMCA isoforms in Ca2+ homeostasis of bladder smooth muscle: evidence from PMCA gene-ablated mice 总被引:2,自引:0,他引:2
Liu L Ishida Y Okunade G Pyne-Geithman GJ Shull GE Paul RJ 《American journal of physiology. Cell physiology》2007,292(1):C423-C431
We previously showed that plasma membrane Ca2+-ATPase (PMCA) activity accounted for 2530% of relaxation in bladder smooth muscle (8). Among the four PMCA isoforms only PMCA1 and PMCA4 are expressed in smooth muscle. To address the role of these isoforms, we measured cytosolic Ca2+ ([Ca2+]i) using fura-PE3 and simultaneously measured contractility in bladder smooth muscle from wild-type (WT), Pmca1+/, Pmca4+/, Pmca4/, and Pmca1+/Pmca4/ mice. There were no differences in basal [Ca2+]i values between bladder preparations. KCl (80 mM) elicited both larger forces (150190%) and increases in [Ca2+]i (130180%) in smooth muscle from Pmca1+/ and Pmca1+/Pmca4/ bladders than those in WT or Pmca4/. The responses to carbachol (CCh: 10 µM) were also greater in Pmca1+/ (120150%) than in WT bladders. In contrast, the responses in Pmca4/ and Pmca1+/Pmca4/ bladders to CCh were significantly smaller (4050%) than WT. The rise in half-times of force and [Ca2+]i increases in response to KCl and CCh, and the concomitant half-times of their decrease upon washout of agonist were prolonged in Pmca4/ (130190%) and Pmca1+/Pmca4/ (120250%) bladders, but not in Pmca1+/ bladders with respect to WT. Our evidence indicates distinct isoform functions with the PMCA1 isoform involved in overall Ca2+ clearance, while PMCA4 is essential for the [Ca2+]i increase and contractile response to the CCh receptor-mediated signal transduction pathway. PMCA; bladder smooth muscle; gene-altered mice 相似文献
15.
Temporal changes in ciliate assemblages during the course ofa bloom of the harmful microalga Heterocapsa circularisquama(Dinophyceae) were investigated and consecutive estimates ofspecies-specific maximum grazing losses were analyzed from Augustto September 1998 at a site in western Hiroshima Bay, the SetoInland Sea of Japan. Temporal increases of the H. circularisquamamean concentration in the water column were observed twice (2529August and 710 September) with the maximum concentration(ca. 4000 cells mL1) being recorded on 25 August. Themain ciliate genera during the bloom were Favella, Tontonia,Eutintinnus, Tintinnopsis and Amphorellopsis. Increases of Favellaand Tontonia were observed when the concentration of H. circularisquamaranged from 260 to 1170 cells mL1. Total maximum grazingloss estimated from the abundance and ingestion rate of eachciliate species on H. circularisquama ranged from 1 to 75% standingstock removed d1 of the H. circularisquama concentration.High grazing losses mainly due to the genera Favella and Tontoniaoccurred during the period when the H. circularisquama concentrationwas decreasing. These results suggest that grazing by ciliateassemblages can influence the population dynamics of H. circularisquamadespite the potentially toxic nature of the phytoplankter. 相似文献
16.
Lamprothamnium, a Euryhaline Charophyte: I. OSMOTIC RELATIONS AND MEMBRANE POTENTIAL AT STEADY STATE 总被引:6,自引:0,他引:6
The charophyte Lamprothamnium papulosum (Wallr.) J. Gr. is foundat salinities varying from nearly fresh water to twice thatof sea water. It can maintain its turgor constant at 302 mosmolkg1 (0.73 MPa) when exposed to external osmotic pressuresof 550 to 1350 mosmol kg1 (1.33.3 MPa). Turgorshows a tendency to rise slightly at lower osmotic pressure(388 mosmol kg1 of turgor at 150 mosmol kg1 externalosmolality). K+ and Cl are the main solutes in the vacuole,and are most important in controlling internal osmotic pressure.Mg2+, Ca2+, and SO24 are present in significant amountsbut their concentrations do not change with changes in externalsalinity. Na+ is present in lower concentration than K+, andplays a minor role in regulating turgor. Sucrose is presentin significant concentrations, but changes little with changesin salinity. Two enzymes involved in sucrose metabolism, sucrosephosphate synthetase (EC 2.4.1.14
[EC]
), and sucrose synthetase (EC2.4.1.13
[EC]
) are active in whole cell extracts of Lamprothamnium.As in the fresh water charophytes, Lamprothamnium membrane potentialmay be depolarized (close to EK) or hyperpolarized, and presumablyof electrogenic origin. Both types of potential are found atall salinities tested. 相似文献
17.
The relationships between photosynthesis and photosyntheticphoton flux densities (PPFD, P-l) were studied during a red-tideof Dinophysis norvegica (July-August 1990) in Bedford Basin.Dinophysis norvegica, together with other dinoflagellates suchas Gonyaulax digitate, Ceratium tripos, contributed {small tilde}50%of the phytoplankton biomass that attained a maximum of 16.7µg Chla 1 and 11.93 106 total cells I1.The atomic ratios of carbon to nitrogen for D.norvegica rangedfrom 8.7 to 10.0. The photosynthetic characteristics of fractionatedphytoplankton (>30 µm) dominated by D.norvegica weresimilar to natural bloom assemblages: o (the initial slope ofthe P-l curves) ranged between 0.013 and 0.047 µg C [µgChla]1 h1 [µmol m s1]1the maximum photosynthetic rate, pBm, between 0.66 and 1.85µg C [µghla]1 h1; lk (the photoadaptationindex) from 14 to 69 µ,mol m2 s1. Carbonuptake rates of the isolated cells of D.norvegica (at 780 µmolm2 s1) ranged from 16 to 25 pg C cell1h and were lower than those for C.tripos, G.digitaleand some other dinoflagellates. The variation in carbon uptakerates of isolated cells of D.norvegica corresponded with PBmof the red-tide phytoplankton assemblages in the P-l experiments.Our study showed that D.norvegica, a toxigenic dinoflagellate,was the main contributor to the primary production in the bloom. 相似文献
18.
We tested the hypothesis that the growth rate of Anabaena circinalis,under diurnally stratified conditions, would increase as flotationvelocity increased owing to higher light availability. An insitu experiment compared the growth of diurnally stratifiedpopulations of A. circinalis with flotation velocities of 0.5and 1.0 m h1, with neutrally buoyant populations thatwere exposed to either mixed or persistently stratified conditions.The experiment was conducted in the turbid lower Murray Riverin South Australia (vertical attenuation coefficient = 4.52± 0.36 m1). To represent the mixing patterns,A. circinalis was contained in diffusion chambers that weremoved to different positions in the water column throughoutthe day. Diurnal populations with flotation velocities of 1.0and 0.5 m h1 grew at 0.23 ± 0.01 and 0.15 ±0.01 day1, respectively. Mixed populations grew at 0.19± 0.01 day1, whereas persistently stratified populationsgrew at 0.43 ± 0.01 day1. Results were used toextend a model that predicts growth of A. circinalis when exposedto the different mixing patterns. The model showed that bloomsare unlikely to be formed when the period of diurnal stratificationis <1 week, regardless of flotation velocity. When the diurnallystratified period is >1 week, flotation velocity is importantand a bloom may form depending on values assigned to the growthperiod and maximum mixed depth (Zm). 相似文献
19.
Neill, S. J., McGaw, B. A. and Horgan, R. 1986. Ethylene and1-aminocyclopropane-l-carboxylic acid production in flacca,a wilty mutant of tomato, subjected to water deficiency andpretreatment with abscisic acid J. exp. Bot. 37: 535541. Plants of Lycoperstcon esculentum Mill. cv. Ailsa Craig wildtype and flacca (flc) were sprayed daily with H2O or 2?102mol m3 abscisic acid (ABA). ABA treatment effected apartial phenotypic reversion of flc shoots; leaf areas wereincreased and transpiration rates decreased. Leaf expansionof wild type shoots was inhibited by ABA. Indoleacetic acid (IAA), ABA and l-aminocyclopropane-l-carboxylicacid (ACC) concentrations were determined by combined gas chromatography-massspectrometry using deuterium-labelled internal standards ABAtreatment for 30 d resulted in greatly elevated internal ABAlevels, increasing from 1?0 to 4?3 and from 0?45 to 4?9 nmolg1 fr. wt. in wild type and flc leaves respectively.Endogenous IAA and ACC concentrations were much lower than thoseof ABA. IAA content ranged from 0?05 to 0?1 nmol g1 andACC content from 0?07 to 0?24 nmol g1 Ethylene emanationrates were similar for wild type and flc shoots. Wilting of detached leaves induced a substantial increase inethylene and ACC accumulation in all plants, regardless of treatmentor type. Ethylene and ACC levels were no greater in flc leavescompared to the wild type. ABA pretreatment did not preventthe wilting-induced increase in ACC and ethylene synthesis. Key words: ABA, ACC, ethylene, wilting, wilty mutants 相似文献
20.
Grazing and ingestion rates of laboratory-born Thalia democraticaaggregates and Dolioletta gegenbauri gonozooids, phorozooidsand oozooids were determined while fed Isochrysis galbana (45µm diameter) alone or in combination with Peridinium trochoideum(1618 µm diameter) at concentrations of 0.150.70mm3 x 11. Grazing rates (ml x zooid1 x 24 h 1)ranged from 10 to 355, and at zooid weights greater than 5 µgcarbon were in order oozooid > gonozooid > aggregate.Grazing rates increased exponentially with increasing zooidweight. Weight-specific grazing rates (ml x µgC1x 24 h1) were independent of the four-fold initial foodconcentration. Mean weight-specific grazing rates increasedlinearly with increasing zooid weight for the aggregates andoozooids, but gonozooid mean rates were independent of zooidweight. Aggregate and gonozooid ingestion rates (106 µm3x zooid1 x 24 h1) ranged from 4 to 134 while oozooidrates ranged from 3 to 67. All ingestion rates were independentof the initial food concentration but increased linearly withincreasing zooid weight at similar rates. All mean weight-specificingestion rates (ml x µgC1 x 24 h1) wereindependent of zooid weight. The mean aggregate daily ration(µgC ingested x µg body C1) was 59% and themean doliolid ration was 132%. Field studies indicate that normalconcentrations of D. gegenbauri in the Georgia Bight clear theirresident water volume (1 m3) in about 4 months, but that highlyconcentrated, swarm populations which occur along thermohalinefronts clear their resident water volume in less than 1 day.
1Current address: MacLaren Plansearch Ltd., P.O.Box 13250, sta.A.,St.John's, Nfld. A1B 4A5 相似文献