共查询到20条相似文献,搜索用时 31 毫秒
1.
Miller Perry L.; Nadkarni Prakash M.; Pearson William R. 《Bioinformatics (Oxford, England)》1992,8(2):167-175
A platform program that performs biological sequence comparisonprovides a case study to compare the relative advantages ofa machineindependent approach to parallel computationversus a machine-specific approach. The program consists oftwo routines: (i) PSCANLIB, which compares a single biologicalsequence against a database of sequences, and (ii) PCOMPLJB,which compares a database of sequences against another databaseof sequences, or against itself. The program was first parallelizedto run on the Intel Hypercube parallel computer using nativeHypercube commands to coordinate the parallel computation. Theparallelization logic of the program was then translated intoa machineindependent parallel programming language, Linda.Tliese two approaches to parallelization are contrasted in termsof: (i) the expressive power of the logic that coordinates theparallel computation, (ii) the portability of the machineindependentversion to other parallel machines and (Hi) the relative efficiencyof the two versions of the program. In the benchmark tests reported,the benefits of the machineindependent approach wereachieved with only a modest sacrifice in efficiency. 相似文献
2.
Single clonal plants of white clover (Trifolium repens L) grownfrom explants in a Perlite rooting medium, and dependent fornitrogen on N2 fixation in root nodules, were grown for severalweeks in controlled environments which provided two regimesof CO2, and temperature 23/18 °C day/night temperaturesat 680 µmol mol1 CO2, (C680), and 20/15 °Cday/night temperatures at 340 µmol mol1 CO2 (C340)After 34 weeks of growth, when the plants were acclimatedto the environmental regimes, leaf and whole-plant photosynthesisand respiration were measured using conventional infra-red gasanalysis techniques Elevated CO2 and temperature increased ratesof photosynthesis of young, fully expanded leaves at the growthirradiance by 1729%, despite decreased stomatal conductancesand transpiration rates Water use efficiency (mol CO2 mol H2O1)was also significantly increased Plants acclimated to elevatedCO2, and temperature exhibited rates of leaf photosynthesisvery similar to those of C340 leaves instantaneouslyexposed to the C680 regime However, leaves developed in theC680 regime photosynthesised less rapidly than C340 leaves whenboth were exposed to a normal CO2, and temperature environmentIn measurements where irradiance was varied, the enhancementof photosynthesis in elevated CO2 at 23 °C increased graduallyfrom approx 10 % at 100 µmol m1 s1 to >27 % at 1170 µmol m2 s1 In parallel, wateruse efficiency increased by 2040 % at 315 µmolm2 s1 In parallel, water use efficiency increasedby 2040 % at 315 µmol m2 s1 In parallel,water use efficiency increased by 2040 % at 315 µmolm2 s1 In parallel, water use efficiency increasedby 2040 % at 315 µmol m2 s1 to approx100 % at the highest irradiance Elevated CO2, and temperatureincreased whole-plant photosynthesis by > 40 %, when expressedin terms of shoot surface area or shoot weight No effects ofelevated CO2 and temperature on rate of tissue respiration,either during growth or measurement, were established for singleleaves or for whole plants Dependence on N2, fixation in rootnodules appeared to have no detrimental effect on photosyntheticperformance in elevated CO2, and temperature Trifolium repens, white clover, photosynthesis, respiration, elevated CO2, elevated temperature, water use efficiency, N2 fixation 相似文献
3.
The effect of DDT on DCIP and Fe(CN)63 photoreductions,and cyclic and non-cyclic photo-phosphorylations, in some 30varieties of barley from widely different parts of the worldis reported. Whereas resistant barleys were not affected byDDT treatment, chloroplasts from treated susceptible barleysshowed parallel inhibitions of all the investigated aspectsof photosynthesis. However, in a few susceptible varieties inhibitionsof Fe(CN)63 photoreduction or non-cyclic photophosphorylationwere not so pronounced. Possible reasons for these anomaliesare discussed; in particular earlier reports that DDT had noeffect on these latter photosynthetic activities may have beendue to the use of hypotonic media during chloroplast isolation. 相似文献
4.
Biomass and phosphorus distribution and accumulation rates wereestimated for an undisturbed subtropical rainforest in northernNew South Wales. The accumulation rates were estimated overa 16-year period. It is estimated that the steady-state above-groundbiomass for this forest is 35.0 tonne ha1. Most of theannual biomass production was replacing litterfall and mortality.The above-ground forest contained 52 kg P ha1 with agross annual accumulation of about 0.4 kg P ha1/yr1.The forest understorey and forest floor contained 4.7 kg P ha1and 7.9 kg P ha1, respectively. The annual uptake wasapprox. 4 kg P ha1 yr1. The phosphorus utilizationof this stand was compared with that of a Eucalyptus grandisplantation Sub-tropical rainforest, biomass accumulation, phosphorus cycling 相似文献
5.
Evidence for Symplasmic Ion Transport in Maize Roots 总被引:1,自引:0,他引:1
Excised maize roots, placed in saturated water vapour to limitthe external ionic supply, continued to produce exudates attheir basal ends for at least 24 h. The mean rate of fluid exudationfrom roots in water vapour was about 28 per cent of the correspondingrate in control roote placed in a solution containing0.1 mil CaCl2 and 1 mM KC1. Moreover, the net fluxes (mean ±S.E.)of potassium and calcium ions into the exudate were reducedfrom (35.8±3.2) x 10 and (4.37±0.39) xlO9 mole cm2 h for roots in solution to(10.9±0.6) x 109 and (l.00±0.06)x 109molecm2 h1 respectively for roots in vapour. It isconsidered that the observation of a prolonged exudation ofwater and ions from the roots placed in water vapour demonstratesthe existence of an alternative ionic supply within the roottissue itself and that this parallel route of ion transportto the exudate constitutes the cortical symplasmic pathway. Pre-treatment of the excised roots with 0.8 M mannitol beforeexudation studies in water vapour and solution led to a significantreduction in the rates of fluid and ion exudation which hadbeen observed in untreated roots under similar conditions. Itis concluded that the plas-molysis, induced by mannitol, disruptedthe symplasmic connections between root cells and that thisperturbation significantly reduced the operation of the symplasmicmode of ion transport into the exudate. 相似文献
6.
The Cl fluxes across the plasma membrane and the Clcontent of the acidresistant alga Dunaliella acidophila(optimal growthat pH 1.0, positive membrane potential) werestudied in the presence of 0.01300 mM Cl. Up to40 mM Cl in the medium, theinternal Cl concentrationis higher than that predicted by the electrochemical equilibrium,whereas at higher external Cl concentrations internalCl levels are lower than expected for the electrochemicalequilibrium. Growth in the absence of Cl is significantlylower than in the standard growth medium (2.2 mM Cl)and this reduction cannot be overcome by the addition ofothermonovalent anions such as Br or NO3 The latterimplies a specific Cl requirement in addition to therole of Cl as apermeant anion during ion translocations.Growth and photosynthesis tolerate an excess of Cl upto 300 mM (without stepwiseadaptation to increasing salinity).The uptake of Cl (measured by tracer techniques) exhibitsMichaelisMenten kinetics (KM = 0.75 mM Cl) andis stimulated by light and high H+ concentrations. Internalacidification by acetic acid causes an inhibition of Cluptake. The uptake of Cl is inhibited by the monovalentanions Br, I, and NO3 with K1, values notvery much different from the KM. value for Cl. The aniontransport inhibitors SITS and DIDS do not affect photosynthesis,but strongly suppressthe uptake of Cl. The Clchannel blockers A9C and NPPB cause inhibitionsof Cl uptake as well as of photosynthesis andthe ATPpool. FCCP strongly depresses the internal ATPpool withouta marked effect on Cl uptake. Cl efflux was inhibitedbyDIDS and SITS, but stimulated or inhibited by FCCP, dependingon the external Cl concentration. Results are in agreementwiththe hypothesis that Cl uptake into D. acidophila is dueto catalysed diffusion and is primarily independent of the hydrolysisofATP. Cl efflux is assumed to be coupled to an activepump. Data suggest tight cooperativity between the systemsresponsiblefor Cl uptake and Cl efflux, with thecytoplasmic pH and the membrane potential being important mediators. Key words: Acid resistance, chloride carrier, chloride channels, Dunaliella acidophila, membrane potential, plasma membrane 相似文献
7.
The thesis that the minimum cell-phosphorus content of planktonalgae is a light- and temperature-independent species constantwas investigated using the marine plankton diatom Thalassiosirarotula. To what extent the maximum cell-phosphorus content isalso a constant, light- and temperature-independent quantityhas been tested in parallel. At 2.5C and 3.03 nE cm2s1 the minimum and maximum cell-phosphorus contents aregreater than the values for 16C and 8.93 nE cm2 s1by a factor of 5.7. The light intensities were kept near thelight saturation for the growth rate for all experimental temperatures(2.5, 6, 12 and 16C). The light dependence of the phosphoruscontent was tested at 12C. For 1.43 nE cm2 s1the minimum phosphorus content was lower by a factor of 2.5than for 64.28 and 80.36 nE cm2 s1 respectively.The maximum P-content for 2.86 nE cm2 s1 was 3.9times higher than for 64.28 nE cm2 s1 T. rotulais, on the basis of the stored P-content, only capable of betweenthree and five cell divisions. The N/P atomic ratios were, dependingupon light and temperature, between 56:1 and 226:1 for the minimumcell-phosphorus content, which implies a pronounced phosphorusdeficiency. 相似文献
8.
A monoclonal antibody (46-12-C12) for use in a solid-phase enzyme-linkedimmunosorbent assay (ELISA) specific for an anionic peroxidase(APRX) from peanut (Arachis hypogaea L.) suspension cell mediumwas developed. The McAb (IgG1) had a high affinity (2.77 ? 1011)and specificity for APRX, and showed only weak interaction witha-amylase and virtually no reactivity with other enzymes, suchas MCPRX (peanut), minor CPRX (peanut), peroxidase (horseradish),RuBP case (spinach), -glucosidase (rice), ß-glucosidase(almonds), acid phosphatase (potato), catalase (bovine liver)and glucose-6-phosphatase (yeast). Sample dilution curves werefound to parallel the standard curve. The detection limit was0.002 ? 1012 mol APRX. The absorbance was linear at concentrationsbetween 0.00424 ? 1012 mol APRX. Three hundredsamples could be analysed per day by one person, with a semi-automaticperformance. Using this assay, levels of APRX have been determinedin a number of biological extracts of different origin. Key words: Peanut, anionic peroxidase, monoclonal antibody, enzyme-linked immunosorbent assay (ELISA) 相似文献
9.
10.
Ion Content of the Halotolerant Alga Dunaliella salina 总被引:3,自引:0,他引:3
The intracellular concentration of the major ions in Dunaliellasalina cells were determined, following the removal of extracellularions by ion-exchange minicolumns. Log phase cells, grown inmedia containing 14 molar NaCl, contained 3050mM chloride and 200350 mM magnesium (5 mM in medium).Phosphorus, which is present intracellularly mostly as polyphosphate,was present in amounts of 60100 fmoles per cell, equivalentto a concentration of 6001,000 mM (0.2 mM in medium).Previous data indicated that such cells contained 2040mM Na+, 150300mM K+, 20mM SO24, and very low concentrationsof Ca2+ and charged nitrogenous compounds. Mg2+ and K+ seemto serve as the major counter ions for the intracellular negativecharge present in the massively accumulated polyphosphates.The former accounts for about 2/3 of the required positive charge.This is supported by the observation that limitation in thephosphate or K+ supply in the medium lead to a parallel decreasein the accumulation of intracellular phosphorus, Mg2+ or K+.
1Present address: Department of Vegetables, The Volcani Center,Bet-Dagan 50250, Israel. (Received June 13, 1988; Accepted August 25, 1988) 相似文献
11.
A stable isotope dilution method employing a deuterium-labelledinternal standard and combined gas chromatography-mass spectrometryhas been used to quantify the accumulation of di-hydrozeatin-O-ß-D-glucosidein the primary leaves of decapitated, disbudded bean plants.This cytokinin accumulated at a rate of 11 ng g1 fr.wt. d1 (eq. to an increase of 50 ng d1 per leaf),reaching a maximum of c. 500 ng g1 after 40 d from decapitation.This accumulation appeared to parallel the gradual increasein leaf fresh weight, and did not occur in detached leaves,in leaves of intact plants, or in leaves of plants that weredecapitated but not disbudded. When secondary lateral buds wereallowed to grow out from decapitated and initially disbuddedplants, the levels of dihydrozeatin-O-ß-D-glucosidein the primary leaves rapidly declined to a value similar toor lower than that found in leaves of intact plants. A similardecline in dihydrozeatin-O-ß-D-glucoside levels wasseen over 5 d in detached leaves of plants which had been decapitatedand disbudded for 15 d; this effect was reduced but not preventedwhen the leaves were supplied with inorganic nutrients. Theseresults are discussed in relation to the metabolism and distributionof cytokinins in the whole plant. 相似文献
12.
Regulation of Sulphate Transport in a Tropical Legume, Macroptilium atropurpureum, cv. Siratro 总被引:2,自引:0,他引:2
CLARKSON DAVID T.; SMITH FRANK W.; BERG PETER J. VANDEN 《Journal of experimental botany》1983,34(11):1463-1483
When young plants of Macroptilium atropurpureum, cv. Siratrowere deprived of external sulphate (-S plants) growth of shootsand roots continued at rates comparable to those in plants wellsupplied with sulphate (control) for 3 d and 5 d respectively.Dilution of internal sulphur therefore took place and redistributionof sulphur occurred between inorganic and organic forms andbetween roots and younger leaves. Even when S-deficiency limitedgrowth, plants contained 16% of their total sulphur as sulphate,but most of this was retained in old leaves and redistributedslowly to growing zones. The capacity for sulphate uptake increased in roots of Splants very soon after they were deprived of external sulphate;within 24 h the absorption from 0.25 mol m3 SO42was more than five times that of control roots. Maximum increasedcapacity was reached after 23 d stress when the Vmaxof system 1 was 1948 nmol h1g1root fr. wt. inS plants and 337 nmol h1g1root fr. wt.in controls. The Kmfor system 1 did not change significantlywith S-stress being between 58 µM in both setsof plants. Absorption of L-cysteine was not stimulated by S-stress. There was a close, positive relationship between plant growthrate and the rate at which sulphate uptake capacity was enhancedby withholding sulphate from culture solutions. When S plants were replaced in sulphate-containing solutiontheir capacity for SO42 declined to the control levelwithin 24 h. Very marked repression of capacity was also foundwhen S plants were treated with L-cysteine, but therewas no immediate effect with methionine. Roots of this species appear to have a very active system fordegrading L-cysteine to sulphate, 30% of the label in 35S-cysteineabsorbed by roots was recovered in 35SO42 after 20 minor 2 h incubation. By contrast, roots had a very weak abilityto reduce sulphate. When part of the root system was in solution lacking sulphatethere was enhanced uptake of sulphate by other parts which themselveswere amply supplied with sulphate. This is seen as an exampleof compensatory absorption. The response to S-stress is specific and there were no positiveinteractions between S-stress and the absorption of phosphate,or P-stress and the uptake of sulphate. The results are discussed in relation to the close control ofsulphate uptake by internal sulphate concentration, redistributionof forms of sulphur during stress and mobility of sulphate inthe phloem. Key words: Kinetics, Amino-S, Sulpholipid, Repression;, Deficiency 相似文献
13.
The efflux of Cl at the plasma membrane of Chara wasstudied in relation to two treatments known to affect the flux:that of removal of external Cl and of light. It is shownthat although removal of external Cl results in a rapidreduction in Cl efflux (consistent with a direct effectof external Cl on the transport system) the magnitudeof this reduction in the dark is greater than the measured darkinflux. Therefore, in the dark at least, it is proposed that1:1 exchange diffusion cannot account for the trans-stimulationof efflux by external Cl. Light induces an inhibition of efflux and a concomitant stimulationof Cl influx at 20 °C, but at 10 °C the responsesto light of the two fluxes can be separated temporally. It istherefore suggested that the fluxes are not reciprocally dependenton the same factor which mediates in the light response. Furtherconsiderations show that it is unlikely that the cytoplasmicCl concentration mediates in the light response of eitherflux, but that changes in cytoplasmic pH may do so. 相似文献
14.
Palomares-Garcia Ricardo; Bustillos-Guzman J. J.; Lopez-Cortes D. 《Journal of plankton research》2006,28(12):1217-1232
Phytoplankton growth and microzooplankton grazing rates wereevaluated in one station in Bahía Concepción,located in the middle region of the Gulf of California, México.We used high-performance liquid chromatography (HPLC) estimationsof phytoplankton pigment signatures to evaluate the annual variationof taxon-specific grazing and growth rates obtained with thedilution technique. Chlorophyll-a (Chl-a) concentrations variedwidely (0.343.32 µg L1) and showed two maxima,during late spring and autumn, associated with the transitionbetween mixed and stratified conditions. Phytoplankton growthrates varied seasonally with the lowest rates during summer(range: 0.012.55 day1 for Chl-a; 0.003.84day1 for Chl-b; 0.263.29 day1 for fucoxanthin;0.006.27 day1 for peridinin; 0.004.35 day1for zeaxanthin). Microzooplankton grazing was an important lossprocess (range: 0.01.89 day1 for Chl-a; 0.003.12day1 for Chl-b; 0.263.29 day1 for fucoxanthin;0.002.03 day1 for peridinin; 0.003.51 day1for zeaxanthin). Average grazing rates accounted 6889%of estimated average phytoplankton pigment-specific growth rates.The analysis of pigment signatures indicates that diatoms anddinoflagellates were the dominant groups, and contrary to expectationfor typical subtropical lagoons, the specific growth rates inBahía Concepción showed a pronounced seasonalvariability, linked to transitional hydrographic conditions.Our results indicate a close coupling between the communitymicrozooplankton grazing and phytoplankton growth rates, withoutselective feeding behavior. These results suggest that microzooplanktonplay a critical role and may significantly modify the availabilityand efficiency of transfer of energy to higher trophic levels. 相似文献
15.
The xylem vessels of excised adventitious roots of onion, Alliumcepa, were perfused with unbuffered nutrient solution adjustedinitially to either pH 9·3 or 3·9; the pH of thesolution after passage through the xylem, at rates not lessthan 2 xylem volume changes min1, was close to pH 6·5in both instances. The flux of H+ across the xylem/symplastboundary into mildly alkaline, phosphate-buffered solutionsperfusing the vessels could be increased greatly with increasingbuffer strength, up to a maximum value between 0·51·0pmol H+ mm2 s1. The apparent neutralization ofacidic malic acid buffers had a slightly lower maximum capacity,equivalent to 0·3 to 0·5 pmol H+mm2 s1. The addition of 5·0 pmol m3fusicoccin (FC) to the xylem perfusion solution stimulated theentry of H+ into the xylem; in unbuffered perfusion solutionsthe pH fell to pH 3·6 after a lag of 2535 min.FC additions to phosphate-buffered solutions also stimulatedthe H+ flux to an extent similar to that in unbuffered solution,viz. 0·20·4 pmol mm2 s1. The release of K+ (36Rb-labelled) into xylem sap transientlyincreased as the [K+] in weakly buffered perfusion solutionswas raised stepwise; a very marked increase being seen whenthe concentration was raised to 100 mol m3 from 40 molm3. The addition of 5·0 mmol m3 FC to theperfusing solution containing 100 mol m3 K+ rapidly decreasedthe K+ flux to the xylem as the H+ flux increased. Fusicoccinalso inhibited the flux of K+ into unbuffered perfusion solutionsbut the effect appeared reversible. Addition of 10 mmol m3abscisic acid (ABA) to the perfusion solution quickly producedtransient increases in both K+ and H+ fluxes into the xylem.In this and other experiments using weakly phosphate-bufferedperfusing solutions, H+ fluxes were comparable in size to thoseof K+ The results are consistent with the idea that the stele of onionroots contains a proton trarislocating ATPase whose activityresponds to the pH of the xylem sap. It is evident that theactivity of the proton secreting and proton neutralizing mechanismsin the xylem parenchyma control the movement of other ions acrossthe xylem/symplast boundary. Key words: Xylem perfusion, fusicoccin, abscisic acid, pH gradient 相似文献
16.
Chloride Transport in Chara corallina and the Electrochemical Potential Difference for Hydrogen Ions 总被引:6,自引:0,他引:6
The pH of the cytoplasm of Chara corallina cells has been measuredwith the weak acid 5,5-dimethyloxazolidine-2,4-dione (DM0).Over an external pH range 4·59·5 the resultsfit the regression equation pHcytoplasm=6·28+0·22pHout. Using measured values of the electric potential difference acrossthe plasmalemma we have calculated the electrochemical potentialdifference across this membrane for H+ and Cl. Thesedata are used to test the hypothesis that the inward transportof Cl is coupled to the inthix of H+ or, which comesto the same thing, efflux of OH. One-for-one couplingwill not give net Cl uptake from solutions with pH greaterthan about 7·2, unless the cytoplasmic Cl concentrationis lower than 10 mM, or the pH just outside the membrane islower than that in the bulk solution. It is shown that net Cluptake proceeds from solutions with pH up to 9. The alternative possibility is that Cl transport is broughtabout by co-transport of two H+ for each Cl; this isnot ruled out by the results reported. Such a mechanism mightbe detectable by its electrogenic effect: although such effectshave not been detected, it is shown that they would be smallunder most conditions. Other possible mechanisms are discussed. 相似文献
17.
A solid state Clselective microelectrode is describedand its performance in test solutions compared with that ofa microelectrode embodying a Clselective liquid ion-exchanger.The solid state microelectrode was found to be more selectiveto Cl against an interfering background of common inorganicion species than the ion-exchanger microelectrode. It performedsatisfactorily in the presence of NO3 and thus is suitablefor use with plant tissues. 相似文献
18.
A dual radioactive-labelled bacteria technique using Vibrio(DRLV), developed for laboratory studies on bacterivory, hasbeen refined for use at the concentrations of prey and predatorstypcially found at sea. Experiments with estuarine water collectedin spring and in autumn showed that bacterivorous nanoflagellates(HNF) (concentration 1.38±0.35x103 HNF ml1) ingested2.7±0.96 DRLV flagellate11 h1 at concentrationsof 0.82.2x106 DRLV ml1 in the presence of 2.04±0.68x106natural bacteria ml1. The method was also applied tosamples collected in October in the Celtic Sea, when on average1 ml of water from the surface layer contained 1.41±0.16x106natural bacteria, 14.6x103 cyanobacteria, 530±170 HNF,7.3±3.0x103 phototrophic nanoflagellates (1.54µm), 49.0±26.5 phototrophic dinoflagellates, 36.3±12.6heterotrophic dinoflagellates and 21.3±9.5 Leucocryptosmarina. Under these conditions the grazing rate in most samplesdid not exceed the coefficient of variation of the method (2%),although we estimate the grazing rate was -1.6 DRLV HNF1h1 and on one occasion a rate of 2.45 was recorded. Thegross growth efficiency for protein of -30% displayed by naturalHNF means that they could release about 相似文献
19.
The abundant species of Calanus that dominate the mesozooplanktonof high North Atlantic latitudes overwinter at depths >500m, when the population loses 7080% of its biomass bypredation and physiological stress. This represents an annualflux of carbon, obtained in the photic zone, into the interiorof the ocean of 274.5 mg C m2 year1, or 0.0018Gt C year1 for the North Atlantic. This is a small valuecompared with the flux of respiratory carbon by diel migrantsin warmer oceans and, when extrapolated to a global flux (0.0120.018Gt C year1 over areas where winter migrations are importantis also small compared with computations of the global sinkingflux of particles through 200 m (1.63.8 Gt C year1or other relevant global carbon fluxes in the oceans. 相似文献
20.
In this paper we report measurements concerning the conductivityof water and ions and the interaction between the two in excisedpieces of xylem of red maple stems under various conditions.We have also demonstrated that it is possible to detect theflow of solutions through the stems of maple by measuring thedegree of interaction between the flow of water and ions. Inthis technique we apply voltage pulses of ±V volts acrossa length of stem and detect the unequal current pulses resultingfrom the greater frictional drag when current (which is carriedprimarily by cations) is flowing against the water stream thanwhen flowing with the water stream. The hydraulic conductivityof recent maple sapwood ranges from 30 to 90 cm3 s1 cm2(J cm3)1 cm; in 2 mM KCl the electrical conductivityis roughly 3 x 104 mho cm1 and the electro-kineticcross coefficient is roughly 4x105 A cm2 (J cm3)1cm. 相似文献