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1.
Borate absorption in excised sugarcane leaves 总被引:1,自引:0,他引:1
Borate absorption in sugarcane consists of a rapid and reversibleinflux into the mesophyll cells of the leaf which is completedwithin 20 rains. (Phase I), followed by a slower and irreversibleaccumulatory phase (II). Phase II uptake represents the summationof 3 absorption mechanisms, each dependent upon the externalconcentration. Highly specific mechanisms 1 and 2 transportborate across the initial barrier into the cells, reaction 3carries the borate across the vacuolar membrane. Calcium isshown to be essential for maximum rates of borate absorption.All 3 reactions are inhibited by OH through a combinationof competitive inhibition and irreversible disruption of cellularfunction or structure. Temperature changes over the range of1040 profoundly affect Vmaz and Km1, but have no effecton Km2 and Km3. Reactions 1 and 2 are unaffected by 50 mtl Cl,SO or H2PO4, whereas each of these anionscompetes with H2BO3 for site 3. Specific metabolic inhibitorswere used to delineate a linkage of mechanisms 1 and 2 to respiratoryelectron transport. Mechanism 3 is coupled to oxidative phosphorylation.
1Published with the approval of the Director of the Hawaii AgriculturalExperiment Station as Technical Paper No. 954. 相似文献
2.
Carrias Jean-Francois; Amblard Christian; Bourdier Gilles 《Journal of plankton research》1994,16(5):471-485
Seasonal population dynamics and the vertical distribution ofciliates were studied in relation to the particular food resourcesoccurring in a humic and moderately acidic lake (Lake Vassivière).The abundance (1.4 x 10320.4 x 103 cells l1 mean= 4.8 x 103 cells l1) and biomass (0.534.6 µgC l1, mean = 6.0 µg C l1) of ciliated protozoawere low and close to values reported for oligotrophic environments.The species composition of the population varied greatly withdepth. Whereas large-sized species of oligotrichs, some of whichwere mixotrophic, dominated at the surface, haptorids were bestrepresented in deep waters. The spatial distribution of thevarious groups of ciliates was largely determined by light andthe vertical distribution of microbial food resources (detritus,bacteria, algae) within the water column of this brown-coloredlake. 相似文献
3.
LARSON KIRK D.; SCHAFFER BRUCE; DAVIES FREDERICK S. 《Journal of experimental botany》1993,44(3):665-671
A system was developed to test the effects of floodwater O2concentration on ethylene evolution and stem lenticel hypertrophy,and the effects of exogenous ethylene on stem lenticel hypertrophyin mango (Mangifera indica L.) trees. Dissolved O2 concentrationsof 17x109 m3 m3 generally resulted in hypertrophyof stem lenticels within about 6 d of flooding, whereas floodwaterO2 concentrations of 1315 x 109 m3 m3 delayedhypertrophy until about day 9. After 14d of flooding, therewere more than twice the number of hypertrophied lenticels pertree with floodwater O2 concentrations of 17 x 109m3 m3 than with floodwater O2 concentrations of 15 x109 m3 m3. Ethylene evolution from stem tissueimmediately above the floodline increased 4- to 8-fold in treesexposed to floodwater O2 concentrations of 12 x 109m3 m3, increased 2-fold for trees exposed to floodwaterO2 concentrations of 67 x 109 m3 m3, butremained constant with floodwater O2 concentrations of 1315x 109 m3 m3. Plants maintained in highly oxygenatedfloodwater (1315 x 109 m3 m3), and givenexogenous ethylene developed many hypertrophied lenticels, whereasplants in highly oxygenated water and not given ethylene developedfewer or nohypertrophied lenticels. These data suggest thatethylene plays a role in promotion of stem lenticel hypertrophyin flooded mango trees, and that floodwater dissolved oxygenconcentration can regulate stem lenticel hypertrophy and ethyleneevolution in this species. Key words: Flooding, hypoxia, hypertrophic cell swelling 相似文献
4.
Temporal-spatial variations of chlorophyll a and primary production in Meiliang Bay, Lake Taihu, China from 1995 to 2003 总被引:2,自引:0,他引:2
There are few long-term data sets on primary production in alake, which can be used to validate the output from a productionmodel. To address this need, we determined the temporalspatialvariations of chlorophyll a (Chl a) and primary production (PPeu),based on the vertically generalized production model (VGPM)by using 742 samplings at seven sites in Meiliang Bay in LakeTaihu from 1995 to 2003. An empirical model estimating primaryproduction (PPin) was used to validate VGPM PPeu and the dominantfactors controlling PP were determined. Markedly higher Chla and PPeu values were recorded in Meiliang Bay in 1996 and1997 than in other years and a marked decrease in Chl a andPPeu was found between 2001 and 2003. Peaks of Chl a typicallyappeared in summer (JuneAugust) and minima occurred inwinter (January). The highest daily mean PPeu usually occurredin summer (June); the exception was at site 1, where peak dailymean PPeu occurred in spring (April). The lowest daily meanPPeu was recorded in winter (January). In Meiliang Bay, 43.0%of annual PP occurred in only 3 months, from June to August.The relative difference of maximum and minimum PPeu was markedlylarger than the corresponding difference in Chl a. Levels ofboth Chl a and PPeu were markedly decreased from the inner tothe outer areas of Meiliang Bay; the highest annual integratedPPeu was found at site 1, close to the inflow of the River Liangxiand this level was 1.85 and 2.14 times higher than at sites3 and 6, respectively, that were located in outer Meiliang Bay.The estimated daily mean PPeu variation closely matched withthat of the Chl a concentration, implying that Chl a concentrationcan account for the considerable variation of PP. The annualintegrated PPeu of the euphotic zone in Meiliang Bay rangedfrom 3.44 x 104 tC year-1 to 8.59 x 104 tC year-1 with an overallmean of 5.65 x 104 tC year-1. A significant positive linearrelationship was found between VGPM PPeu and empirical modelPPin [PPin = 0.826 (±0.015)PPeu + 272.0 (±25.0),r2 = 0.80, n = 742, P < 0.0001]. By considering the effectof water temperature, photosynthetically active radiation andphotoperiod on PP, the VGPM- generated PPeu more accuratelycaptured monthly variations than did the empirical model thatonly included Chl a concentration. 相似文献
5.
Biomass and productivity of microplankton were measured in theCraternaya Bay (Kurile Islands), which is influenced by hydrothermalactivity and volcanic heating. The hydrothermal fields are situatedaround its shores and underwater within the 020 m depth.A dense bloom of photoautotrophic microplanktonwas observed there, dominated by diatoms, phytoflagellates andthe symbiont-containing ciliate Mesodinium rubrum. The biomassof these ciliates attained 311 g m-3 in the upper waterlayer. The total biomass of the phototrophic microplankton reached3046 g m-3. The primary production in the water columnwas, correspondingly, enormously high: 610 g C m-2 day-1.The depth of the euphotic zone was 7 m. Pelagic photosynthesiswas inhibited in the upper 01 m by the spreading of alayer of low-salinity hydrothermal water. The numerical densityof bacterioplankton in the upper zone of the water column variedfrom 1 x 106 to 2.9 x 106 cells ml-1, and its wet biomass from250 to 750 mg m-3. Its production varied at stations from 70to 390 mg m-3 day-1. Chemosynthesis contributed up to 30% ofthis production in the sites neighbouring the hydrothermal vents.Outside their direct impact however, its share was negligible.The biomass of heterotrophic planktonic ciliates varied from30 to 270 mg m-3. The mechanisms of possible influence of shallowvolcanic activity on development and function of microplanktonin the Craternaya Bay is discussed. 相似文献
6.
Histiobalantium sp. was found regularly in the pelagic zoneof Lake Constance, FRG, over five annual cycles. Maxima of upto 6400 cells l1 were recorded in late summer, with similarnumbers in the 08 and 820 m depth intervals. Onan annual average, the population accounted for 1017%of the total biomass of planktonic ciliates. In the laboratory,Histiobalantium grew well on a diet of the cryptophyte Rhodomonassp. Maximum growth rates obtained in batch cultures were 0.21and 0.33 day11 at 9 and 18°C, respectively. In situexperiments using diffusion chambers yielded positive growthrates in autumn and winter. The highest values recorded at theambient temperatures 5, 14 and 17°C were 0.17, 0.32 and0.40 day1, respectively. Comparing these results withthe different seasonal distributions and higher measured growthrates of other ciliates from Lake Constance, we conclude thatHistiobalantium is a superior competitor at relatively low algalfood concentrations.
2Present address: Fisheries & Oceans Canada, 4160 MarineDrive, West Vancouver, BC, V7V 1N6, Canada 相似文献
7.
Contribution of Picocyanobacteria to total primary production and community respiratory losses in a backwater system 总被引:2,自引:0,他引:2
The contribution of autotrophic picoplankton (APP) to phytoplanktonicprimary production, investigated during the phytoplankton growingseason (MarchSeptember) in a macrophyte-dominated backwatersystem near Vienna, showed that APP mainly consisted of rod-shapedand coccoid cyanobacteria. Two stations were examined, exhibitingsimilar seasonal patterns in the development of picocyanobacteria,although the two sites differed in picocyanobacterial cell numbersand biomass by a factor of 1.5. Cell numbers determined by epifluorescencemicroscopy varied between 0.29 x 104 and 34.5 x 104 cells ml1at Station 1, and between 0.23 x 104 and 19.1 x 104 cells ml1at Station 2. At both sites, the mean cell volume of picocyanobacteriawas 0.5 µm3. Carbon fixation in the planktonic communityof the Kühwörter Wasser was dominated primarily bylarger phytoplankton, although the picoplankton community sometimessupplied up to 74% (mean: 35%) of total primary production.Distinct differences in chlorophyll a concentrations and primaryproduction between the two sites refer to a greater competitionbetween phytoplankton and macrophytes at Station 2. Communityrespiration deviated greatly in time and in level at the twostations, showing a higher dynamic in community metabolism atStation 1. At this site, community respiration losses rangedbetween 12 and 100% of gross production. Hence, community metabolismcomprised net autotrophic, balanced, and net heterotrophic situationsover the investigation period, whereas at Station 2, only netautotrophic situations could be determined. 相似文献
8.
Hogan K.P.; Fleck I.; Bungard R.; Cheeseman J.M.; Whitehead D. 《Journal of experimental botany》1997,48(6):1289-1297
Red beech (Nothofagus fusca (Hook. F.) Oerst.; Fagaceae) andradiata pine (Pinus radiata D. Don; Pinaceae) were grown for16 months in large open-top chambers at ambient (37 Pa) andelevated (66 Pa) atmospheric partial pressure of CO2, and incontrol plots (no chamber). Summer-time measurements showedthat photosynthetic capacity was similar at elevated CO2 (lightand CO2-saturated value of 17.2 µmol m2 s1for beech, 13.5 µmol m2 s1 for pine), plantsgrown at ambient CO2 (beech 21.0 µmol2 s1,pine 14.9 µmol m2s1) or control plants grownwithout chambers (beech 23.2 µmol m2 s1,pine 12.9 µmol m2 s1). However, the higherCO2 partial pressure had a direct effect on photosynthetic rate,such that under their respective growth conditions, photosynthesisfor the elevated CO2 treatment (measured at 70 Pa CO2 partialpressure: beech 14.1 µmol m2 s1 pine 10.3)was greater than in ambient (measured at 35 Pa CO2: beech 9.7µmol m2 s1, pine 7.0 µmol m2s1) or control plants (beech 10.8 µmol m2s1, pine 7.2 µmol m2 s1). Measurementsof chlorophyll fluorescence revealed no evidence of photodamagein any treatment for either species. The quantity of the photoprotectivexanthophyll cycle pigments and their degree of de-epoxidationat midday did not differ among treatments for either species.The photochemical efficiency of photosystem II (yield) was lowerin control plants than in chamber-grown plants, and was higherin chamber plants at ambient than at elevated CO2. These resultssuggest that at lower (ambient) CO2 partial pressure, beechplants may have dissipated excess energy by a mechanism thatdoes not involve the xanthophyll cycle pigments. Key words: Carotenoids, chlorophyll fluorescence, photosynthesis, photoinhibition, photoprotection, xanthophyll cycle 相似文献
9.
Annual Variation of Environmental Variables, Phytoplankton Species Composition and Photosynthetic Parameters in a Coastal Lagoon 总被引:6,自引:0,他引:6
Physicalchemical variables, phytoplankton biomass, speciescomposition and photosynthesisirradiance (P-I) parameterswere analysed during 1 year in the Santo André Lagoon,SouthwestPortugal a land-locked coastal ecosystem withtemporary connections with the sea. When the lagoon stayed closedthe observed phytoplankton blooms were mainly caused by Prorocentrumminimum, a potentially toxic dinoflagellate. It was dominantduring most of the year but the seawater inflow to the lagoontriggered a decrease in phytoplankton biomass and an abruptshift in species composition. The maximum photosynthetic rate(Pmax) ranged from 2.0 to 22.5 mg C (mg chlorophyll a)1h1 and the light saturation index (Ik), ranged from 5.2to 335.0 µE m2 s1, with winter minima andsummer maxima. Pmax and Ik were both positively correlated totemperature. Abundance ofP. minimum was associated with highnitrate concentrations whereas diatoms appear when ammonium,salinity and wind velocity are high. A mathematical model todescribe photosynthetic rate as a function of irradiance andtemperature [P (I, t)] was applied to the samples in which P.minimum was the dominant species 相似文献
10.
Malinsky-Rushansky Nechama Z.; Berman T.; Dubinsky Z. 《Journal of plankton research》1997,19(8):979-993
Autotrophic picoplankton populations in Lake Kinneret are composedof picocyanobacteria and picoeukaryotes. Overall, the ratesof photosynthetic carbon fixed by autotrophic picoplankton duringthis study were low (0.011.5 mg Cm3 h1).The highest chlorophyll photosynthetic activity of the <3µm cell-size fraction was found in spring, when picoeukaryotespredominated and in addition small nanoplankton passed throughthe filters. The maximum cell-specific photosynthetic rate ofcarbon fixation by picocyanobacteria and picoeukaryotes was2.5 and 63 fg C cell1 h1, respectively. The highestspecific carbon fixation rate of autotrophic picoplankton was11 µg C µg1 Chl h1 The proportionalcontribution of autotrophic picoplankton to total photosynthesisusually increased with depth. Picocyanobacteria collected fromthe dark, anaerobic hypolimnion were viable and capable of activephotosynthesis when incubated at water depths within the euphoticzone. Maximum rates of photosynthesis (Pmax) for picocyanobacteriaranged from 5.4 to 31.4 fg C cell1 h1 with thehighest values in hypolimnetic samples exposed to irradiance.Photosynthetic efficiency ( 相似文献
11.
Nitrate Effects on Pre-emergence Growth and Emergence Percentage of Wheat (Triticum aestivum L.) from Different Sowing Depths 总被引:1,自引:0,他引:1
The effects of a range of applied nitrate (NO3) concentrations(020 mol m3) on germination and emergence percentageof Triticum aestivum L. cv. Otane were examined at 30, 60, 90and 120 mm sowing depths. Germination percentage was not affectedby either sowing depth or applied NO3 concentration whereasemergence percentage decreased with increased sowing depth regardlessof applied NO3 concentration. Nitrate did not affectemergence percentage at 30 mm sowing depth, but at 60 to 120mm depth, emergence percentage decreased sharply with an increasedapplied NO3 concentration of 0 to 1·0 mol m3then decreased only slightly with further increases in appliedNO3 of about 5·0 mol m3. Root and shoot growth, NO3 accumulation and nitrate reductaseactivity (NRA) of plants supplied with 0, 1·0 and 1·0mol m3 NO3 at a sowing depth of 60 mm were measuredprior to emergence. The coleoptile of all seedlings opened withinthe substrate. Prior to emergence from the substrate, shootextension growth was unaffected by additional NO3 butshoot fr. wt. and dry wt. were both greater at 1·0 and1·0 mol m3 NO3 than with zero NO3.Root dry wt. was unaffected by NO3. Nitrate concentrationand NRA in root and shoot were always low without NO3.At 1·0 and 10 mol m3 NO3, NO3 accumulatedin the root and shoot to concentrations substantially greaterthan that applied and caused the induction of NRA. Regardlessof the applied NO3 concentration, seedlings which failedto emerge still had substantial seed reserves one month afterplanting. Coleoptile length was substantially less for seedlingswhich did not emerge than for seedlings which emerged, but wasnot affected by NO3. It is proposed that (a) decreasedemergence percentage with increased sowing depth was due tothe emergence of leaf I from the coleoptile within the substrateand (b) decreased emergence percentage with additional NO3was due to the increased expansion of leaf 1 within the substrateresulting in greater folding and damage of the leaf. Key words: Triticum aestivwn L., nitrate, sowing depth, seedling growth, seedling emergence 相似文献
12.
Conspicuous Peak of Oligotrichous Ciliates Following Winter Stratification in a Bog Lake 总被引:2,自引:0,他引:2
We analysed early spring protozooplankton peaks following winterstratification in two different basins (northeast, NE; southwest,SW) of an artificially-divided bog lake Große Fuchskuhle(Brandenburg,Germany). The maximum ciliate biomass and numbers (660 and 990µg l1 of organic carbon, and 290 and 260 cellsml1 in NE and SW, respectively) were reached in the surfacelayer during the ice melting and then continuously decreased.The surface layers were numerically dominated by species ofthe genus Urotricha, while in the ciliate biomass during thefirst part of the study, a mixotrophic oligotrich, Pelagostrombidiummirabile prevailed (Corg up to 940 µg l1). We observeda conspicuous ciliate peak that could not be related to thefeeding activity of the dominant ciliate species upon picoplankton.Seemingly, the peak was related to the specific conditions resultingfrom the ice melting where these ciliates could be concentrated.Additionally, the mixotrophy of oligo-trichous species allowedthem to penetrate below the oxycline, although feeding on nanoplanktonsuch as flagellates was also very likely. Our direct measurementsof uptake rates of bacteria showed that the abundant strombidiidswere not nutritionally dependent on bacterivory. However, theciliate uptake rate (up to 670 bacteria ciliate1 h1)contributed significantly to the overall bacteria mortalityrate. The maximum (community average) cell-specific ciliatefeeding rate of over 200 bacteria ciliates1 h1was reached, along with an increasing contribution of scuticociliates,paralleled by a drop in large oligotrichs. 相似文献
13.
Nitrate Inhibition of Chloride Influx in Barley: Implications for a Proposed Chloride Homeostat 总被引:6,自引:0,他引:6
Net accumulation of Cl by intact barley plants was virtuallyeliminated in roots and reduced by 40% in shoots when externalmedia (0.5 mol m3 CaSO4 plus 05 mol m3KCI) were supplemented with 0.25 mol m Ca(NO3)2. Plasmalemma36Cl influx (oc) was shown to be insensitive to externalNO3- in plants which had previously been grown in solutionslacking 3, but oc became sensitive to NO3-after a lagperiod of 36 h. Kinetic analyses revealed that the inhibitionof 36C1 influx by external NO3- was complex. At 0.25mol m3 NO3- the Vmax for Cl influx was reducedby greater than 50%, with insignificant effects upon Km. At0.5 mol m3 NO3- there was no further effect upon Vmaxbut Km for influx increased from 38±5 mmol m3to 116±26 mmol m3. By contrast, Cl effluxwas found to be insensitive to external NO3-. A model for theregulation of Cl influx is proposed which involves bothnegative feedback effects from vacuolar NO3- +Cl) concentrationand (external) NO3- inhibition of Cl influx at the plasmalemma.These combined effects serve to discriminate against Claccumulation, favouring NO3- accumulation, when the latter ionis available. Such observations are inconsistent with recentproposals for the existence of bona fide homeostats for chlorideaccumulation in higher plants. Key words: Nitrate inhibition, Chloride influx, Barley 相似文献
14.
The taxonomic composition, abundance and biomass of microzooplanktonwere studied at eight stations in Lake ShinjiOhashi RiverLakeNakaumi brackish-water system, Japan, monthly from April 1998to March 1999. Over the entire area, naked ciliates numericallydominated the microzooplankton community (annual mean 39.6%)followed, in order, by tintinnids (30.3%), copepod nauplii (24.6%)and rotifers (5.5%). The abundance of each taxonomic group ofmicrozooplankton varied geographically due to large salinityvariations (range 1.533.3 p.s.u.). It was notable thatnaked ciliates occurred overwhelmingly in Lake Shinji (54.9%of total microzooplankton) and rotifers were relatively numerousin Lake Shinji (8.8%) and Ohashi River (11.1%), where the salinitywas lower (annual mean 4.1 and 13.6 p.s.u., respectively) thanin Lake Nakaumi and Sakai Strait (26.3 and 29.8 p.s.u., respectively).Owing to large seasonal temperature variation (range 5.429.8°C),the abundance of microzooplankton showed marked seasonal variations,being higher in spring and summer than in the remaining seasons.A total of 49 species of tintinnids were identified, and 15of these species reached concentrations >500 individualsl-l. The occurrence of most tintinnid species was confined tocertain months or locations, closely associated with species-specifictemperature and salinity preference and/or tolerance. In thiseutrophic system, food supply for microzooplankton might besufficient due to extremely high chlorophyll a concentration(annual mean 8.8 µg l-lin Sakai Strait to 22.6 µgl-l in Lake Shinji). However, microzooplankton biomass remainedmoderate (range 0.1918.7 µg C l-l) due probablyto heavy predation by mesozooplankton, which inhabit this brackish-watersystem at extremely high biomass. 相似文献
15.
Role of NBC1 in apical and basolateral HCO3- permeabilities and transendothelial HCO3- fluxes in bovine corneal endothelium 总被引:1,自引:0,他引:1
Corneal transparency and hydration control are dependent on HCO3 transport properties of the corneal endothelium. Recent work (13) suggested the presence of an apical 1Na+-3HCO3 cotransporter (NBC1) in addition to a basolateral 1Na+-2HCO3 cotransporter. We examined whether the NBC1 cotransporter contributes significantly to basolateral or apical HCO3 permeability and whether the cotransporter participates in transendothelial net HCO3 flux in cultured bovine corneal endothelium. NBC1 protein expression was reduced using small interfering RNA (siRNA). Immunoblot analysis showed that 515 nM siRNA decreased NBC1 expression by 8095%, 4 days posttransfection. Apical and basolateral HCO3 permeabilities were determined by measuring the rate of pHi change when HCO3 was removed from the bath under constant pH or constant CO2 conditions. Using either protocol, we found that cultures treated with NBC1 siRNA had sixfold lower basolateral HCO3 permeability than untreated or siCONTROL siRNA-treated cells. Apical HCO3 permeability was unaffected by NBC1 siRNA treatment. Net non-steady-state HCO3 flux was 0.707 ± 0.009 mM·min1·cm2 in the basolateral-to-apical direction and increased to 1.74 ± 0.15 when cells were stimulated with 2 µM forskolin. Treatment with 5 nM siRNA decreased basolateral-to-apical flux by 67%, whereas apical-to-basolateral flux was unaffected, significantly decreasing net HCO3 flux to 0.236 ± 0.002. NBC1 siRNA treatment or 100 µM ouabain also eliminated steady-state HCO3 flux, as measured by apical compartment alkalinization. Collectively, reduced basolateral HCO3 permeability, basolateral-to-apical fluxes, and net HCO3 flux as a result of reduced expression of NBC1 indicate that NBC1 plays a key role in transendothelial HCO3 flux and is functional only at the basolateral membrane. corneal endothelium; sodium bicarbonate cotransporter; small interfering RNA; bicarbonate transport 相似文献
16.
Feeding of planktonic rotifers on ciliates: a method using natural ciliate assemblages labelled with fluorescent microparticles 总被引:1,自引:0,他引:1
Joaquim-Justo Celia; Detry Cedric; Caufman Fabrice; Thome Jean-Pierre 《Journal of plankton research》2004,26(11):1289-1299
A method was developed to allow direct measurements of predationexerted by metazooplankton on ciliates. The method relied onthe use of ciliates labelled with fluorescent microparticles(FMP). Optimal labelling conditions were determined with ciliatesfrom cultures (Tetrahymena pyriformis) and with natural ciliateassemblages sampled in a river. Labelled T. pyriformis wereused as tracer food to determine gut passage time (GPT) andingestion rates of the rotifer Brachionus calyciflorus in thelaboratory. Predation of metazooplankton from the lowland riverMeuse (Belgium) was determined by labelling natural assemblagesof ciliates and using them as tracer food for metazooplankterssampled in the river. Optimal labels of ciliates, i.e. sharpdistribution of FMP in cells, were obtained with short incubations(10 min) and low FMP concentrations (1 x 105 mL1). GPTvaried between 30 and 45 min for B. calyciflorus and from 25up to >35 min for rotifers from the river. The ingestionrate of B. calyciflorus fed with T. pyriformis was 3.3 ±0.6 ciliate rot1 h1, i.e. 1.4 ± 0.3 ngCrot1 h1. Metazooplankton species for which theingestion of ciliates could be measured were the rotifers Keratellacochlearis, Euchlanis dilatata and Synchaeta spp. Ingestionrates measured ranged from 0.4 to 12.5 ngC rot1 h1.The method proposed proved to be useful in estimating the predationof microplankton on ciliates in semi- in situ conditions; infurther developments, labelled natural assemblages of ciliatescould be used for in situ incubations with the Haney chamber. 相似文献
17.
Pigmented nanoflagellates in the coastal western subtropical Pacific are important grazers on Synechococcus populations 总被引:2,自引:0,他引:2
Tsai An-Yi; Chiang Kuo-Ping; Chan Ya-Fan; Lin Yun-Chi; Chang Jeng 《Journal of plankton research》2007,29(1):71-77
Although the key grazers on Synechococcus and other planktonicmarine bacteria are generally thought to be nanoflagellates(both non-pigmented and pigmented) as well as ciliates, we previouslyfound in our western subtropical Pacific coastal study sitethat ciliates exerted almost no grazing pressure. In this study,we used fluorescently labeled particles (FLP) as Synechococcus-sizedmimics to examine the contribution of pigmented (may includeautotrophic and mixotrophic spp.) versus non-pigmented (heterotrophic)nanoflagellate grazing to Synechococcus morality. During thewarm season from June to September, > 50% of the nanoflagellatepopulation was pigmented (1.82 x 103 versus 1.21.6x 103 cells mL1). Consumption, or clearance rates perpigmented nanoflagellate, varied considerably (0.5046.90nL cell1 h1), with the highest rates in June.Raw data showed pigmented nanoflagellate grazing to accountfor 294% (mean 43%) of Synechococcus production fromMay to October. Pigmented nanoflagellates consumed 12.5-foldmore Synechococcus than did ciliates. This study provides thefirst evidence that pigmented nanoflagellates are key grazersof Synechococcus populations in subtropical western Pacificcoastal waters. 相似文献
18.
The response of the germination of seeds of Barbarea vema (Mill.)Aschers, Brassica chinensis L., Brassica juncea (L.) Czern.& Coss., Brassica oleracea L. var. gongylodes L., Camelinasaliva (L.) Crantz, Eruca saliva Mill., Lepidium sativum L.,Nasturtium officinale R. Br., and Rorippa palustris (L.) Besserto white fluorescent light of different photon flux densitiesapplied for different daily durations in a diurnal alternatingtemperature regime of 20 °C/30 °C (16 h/8 h) was quantifiedby linear relations between probit percentage germination andthe logarithm of photon dose, the product of photon flux densityand duration. The low energy reaction, in which increasing dosepromotes germination, was detected in all the seed populationsbut in Barbarea vema and Brassica Juncea the lowest photon doseapplied (1052 and 105 7 mol m2 d1,respectively) was sufficient to saturate the response. Comparisons,where possible, between photoperiods demonstrated reciprocity,i.e. germination was proportional to photon dose irrespectiveof photoperiod, for the low energy reaction in Brassica oleracea(1 min d1 to 1 h d1), Camelina saliva (1 min d1to 8 h d1), Eruca saliva (1 min d1 to 24 h d1),Lepidium sativum (I min d1 to 8 h d1) and Rorippapalustris (1 min d1 to 8 h d1), but not in Brassicachinensis and Nasturtium officinale. The high irradiance reaction,in which increasing dose inhibits germination, was detectedin Barbarea vema, Brassica chinensis, Brassica juncea, Brassicaoleracea, and Camelina saliva. The minimum dose at which inhibitionwas detected was lO03 mol m2 d1.These results are discussed in the context of devising optimallight regimes for laboratory tests intended to maximize germination The response of germination to photon dose was also quantifiedwith 3 x 104 M GA2, co-applied (Brassica chinensis, Camelinasaliva, and Lepidium sativum) and with 2 x 102 M potassiumnitrate co-applied (Brassica chinensis). In the latter casepotassium nitrate had no effect in the dark and inhibited germinationin the light, but GA2, promoted germination substantially inall three species. Variation amongst seeds in the minimum photondose required to stimulate germination was not affected by co-applicationof GA2, in Brassica chinensis and Camelina saliva, whereas seedsof Lepidium salivum showed a narrower distribution of sensitivitiesto the low energy reaction in the presence of GA2 Barbarea vema (Mill.) Aschers, Brassica chinensis L., Brassica juncea (L.) Czern. & Coss., Brassica oleracea L. var. gongylodes L., Camelina saliva (L.) Crantz, Eruca saliva Mill., Lepidium satiaum L., Nasturtium officinale R. Br., Rorippa palustris (L.) Besser, Cruciferae, light, gibberellic acid, seed germination, seed dormancy 相似文献
19.
Whitehead, D. C. and Lockyer, D. R. 1986. The influence of theconcentration of gaseous ammonia on its uptake by the leavesof Italian ryegrass, with and without an adequate supply ofnitrogen to the roots.J. exp. Bot. 38: 818827. Plants of Italian ryegrass (Lolium multiflorum Lam.) were grownin pots of soil with two rates of 15N-labclled nitrate, oneproviding adequate, and the other less than adequate, N formaximum growth. After 25 d in a controlled environment cabinet,the plants were transferred to chambers and exposed for 33 dto NH3in the air at one of nine concentrations ranging from14 to 709 µg NH3 m3. Increasing the concentrationof NH3 in the air increased the dry weight of the shoots ofplants grown at the lower but not the higher rate of nitrate.The content of total N in the plant shoots (% dry weight) waslinearly related to NH3 concentration; at 709 µg NH3 andin both sets of plants it was more than double the content at14 µg NH3 m3. Calculations, based on 15N enrichment,indicated that the amount of N taken up from the NH3 per unitleaf area increased linearly with increasing concentration ofNH3 in the air uptake (µg dm2 h1) = 0.1009xat the lower rate of nitrate and 0-0829x at the higher rateof nitrate, where x is the concentration of NH3 in the air expressedas µg NH3m3. The proportion of the total plant N that was derived from theNH3 ranged from 4?0% at a concentration of 14 µg NH3 m3with the higher rate of nitrate addition to 77?5% at a concentrationof 709 µg m3 with the lower rate of nitrate addition.The proportions of the total N in the water-insoluble proteinof the leaf tissue that were derived from nitrate and gaseousNH3 were similar to the proportions in the whole leaf material. Key words: Ammonia, nitrogen, leaf sorption, Lolium multiflorum 相似文献
20.
Temporal variability of diversity and biomass of tintinnids (Ciliophora) in a southwestern Atlantic temperate estuary 总被引:2,自引:0,他引:2
Seasonal variations in diversity and biomass of tintinnids (Ciliophora:Tintinnida) were investigated at two fixed stations in the innerpart of the Bahía Blanca Estuary (38°42' S, 61°50'W) during an annual cycle. The variations were analysed in relationto surface temperature, salinity, transparency, solar radiationand chlorophyll a (Chl a)concentration. Biomass was calculatedin terms of biovolume and carbon units. Diversity was estimatedas the number of species and the Shannon Index (H', ln based).Density of tintinnids ranged from 100 to 7800 individuals L1H' ranged from 0 to 1.81. The biomass varied from 0.3 to 127.78x 106 µm3 L1 (0.0239.4 µg C L1).Density was significantly related to temperature, solar radiationand Secchi distance (P < 0.01); diversity was significantlyrelated to temperature (P < 0.01) and solar radiation (P< 0.05). Biomass was significantly related only to temperature(P < 0.01) in one of the stations. According to principalcomponents analysis (PCA) tintinnids exhibited a segregationof three groups: winter, springsummer and autumn forthe most internal station and winter, spring and summerautumnfor the most external station. H' values were lower than thoseobserved in other coastal systems found at about the same latitudein the northern hemisphere. 相似文献