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1.
Glycolysis in vitro was studied, using extracts from germinatingpea seeds. Steady state rates of CO2 evolution declined long before allsubstrate, either glucose or sugar phosphate, was convertedto CO2 and ethanol. High rates of CO2 evolution were restoredby addition of more substrate. Some factors which regulate glycolysis in vitro were investigated,using glucose as a substrate. High levels of P1 and Mg2+ wererequired to obtain optimum rates of CO2 evolution. Levels ofintermediates indicated that high P1 acted via a stimulationof 6-phosphofructokinase. Glucose, in the presence of hexokinase, induced substantiallyhigher rates of CO2 evolution than a number of sugar phosphates.However, evolution of CO2, from glucose-6-phosphate or fructose-6-phosphate,was greatly stimulated by the addition of purified yeast pyruvatedecarboxylase, rates sometimes exceeding those attained whenglucose was used as a substrate. The reason for this stimulationby pyruvate decarboxylase is unknown. Effects of high KCl and NaCl were measured, using glucose asa substrate. KCl and NaCl, at 200 mM and higher concentrations,reduced steady state rates of glycolysis. The degree of inhibitionwas much greater at high than at low rates of glycolysis. Thiswas shown, for example, when using different concentrationsof P1. High levels of KCl and NaCl greatly increased levels of fructose-1,6-diphosphateand triose phosphates, particularly at low P1, and did not reducethe net carbon movement past 6-phosphofructokinaseThus high KCl and NaCl weakened the control of glycolysis by6-phos-phofructokinase. 相似文献
2.
NADP malic enzyme (EC 1.1.1.40
[EC]
) from leaves of two C4 speciesof Cyperus (C. rotundus and C. brevifolius var leiolepis) exihibiteda low level of activity in an assay mixture that contained lowconcentrations of Cl. This low level of activity wasmarkedly enhanced by increases in the concentration of NaClup to 200 mM. Since the activity of NADP malic enzyme was inhibitedby Na2SO4 and stimulated by relatively high concentration ofTris-HCl (50100 mM, pH 78), the activation ofthe enzyme by NaCl appears to be due to Cl. Variationsin the concentration of Mg2+ affected the KA (the concentrationof activator giving half-maximal activation) for Cl,which decreased from 500 mM to 80 mM with increasing concentrationsof Mg2+ from 0.5 mM to 7 mM. The Km for Mg2+ was decreased from7.7 mM to 1.3 mM with increases in the concentration of NaClfrom zero to 200 mM, although the increase of Vmax was not remarkable.NADP malic enzyme from Cyperus, being similar to that from otherC4 species, was able to utilize Mn2+. The Km for Mn2+ was 5mM, a value similar to that for Mg2+. The addition of 91 mMNaCl markedly decreased the Km for Mn2+ to 20 +M. NADP malicenzyme from Setaria glauca, which contains rather less Clthan other C4 species, was inactivated by concentrations ofNaCl above 20 mM, although slight activation of the enzyme wasobserved at low concentrations of NaCl at pH7.6. (Received February 20, 1989; Accepted June 12, 1989) 相似文献
3.
The potential differences across the tonoplast and plasmalemmamembranes have been measured in the single cells of Nitellatranslucens, the cells being immersed in an artificial pondwater (composition: NaCl 1.0 mM., KC1 0.1 mM., CaCl2, 0.1 mM.).The potential of the cytoplasm is 138 m V with respectto the bathing medium and 18 mV with respect to the vacuole.The concentrations of Na, K, and Cl have been measured in thetwo cell fractions. The concentrations in the flowing cytoplasmare: Na 14 mM., K 119 mM., and Cl 65 mM.; the vacuolar concentrationsare: Na 65 mM., K 75 mM.,and Cl 160 mM. The observed potential differences across the two membranesare compared with the Nernst potentials for all three ions.This analysis shows that all three ions are actively transportedat the plasmalemma: Na is pumped outwards while K and Cl arepumped inwards. At the tonoplast Na is pumped into the vacuolewhile K and Cl are close to electrochemical equilibrium. The inhibitor, ouabain, has no effect on the cell resting potential. 相似文献
4.
Iu G Kaminski? 《Biokhimii?a (Moscow, Russia)》1983,48(7):1080-1084
The circadian changes in the contents of intermediates of the initial reactions of the glycolytic pathway in pigeon liver were studied. the concentrations of glucose, glucose-6-phosphate, fructose-6-phosphate, fructose-1,6-diphosphate and triose phosphates were found to change synchronously, being maximal at the dark time and minimal during the light daytime. The glycogen content in the liver decreased steadily between 12.00 and 09.00. The diurnal variations in the concentrations of metabolite pairs (glucose and glucose-6-phosphate, glucose-6-phosphate and fructose-6-phosphate, fructose-6-phosphate and fructose-1.6-diphosphate, fructose-1.6-diphosphate and triose phosphates) appeared to correlate significantly. The results obtained suggest that in the liver at least there are no limiting i. e. physiologically non-equilibrium reactions in the carbohydrate metabolic pathway from glucose to triose phosphates. 相似文献
5.
Kelly Grahame J.; Mukherjee Ute; Holtum Joseph A. M; Latzko Erwin 《Plant & cell physiology》1985,26(2):301-307
Phosphofructokinase was purified 585-fold from Chlorella pyrenoidosaby using a combination of ammonium sulphate fractionation, filtrationthrough Sepharose 4B and chromatography on DEAE-Sephacel. Enzymestability was maintained by the presence of 50 mM Pi at pH 6.6.The optimum pH for activity was 7.7. Concentrations of substratesrequired to achieve half maximal velocity in the standard assaywere 9 µM (ATP) and 0.2 mM (fructose-6-P). ATP above 0.5mM was inhibitory. Enzyme activity was inhibited by high concentrations(10100 mM) of Pi but lower concentrations (15mM) were effective in relieving the influence of other inhibitorssuch as P enolpyruvate. Inhibition by P-enolpyruvate was greaterat lower pH and with less Pi in reaction mixtures: 50% inhibitioncould be attained with 0.1 mM P-enolpyruvate. Fructose-2,6-bisphosphate,which was shown to be present in Chlorella, had no effect onthe phosphofructokinase. Chlorella appeared to contain onlyone form of phosphofructokinase, possibly in the chloroplast.No pyrophosphate :D-fructose-6-P 1-phospho transferase activitycould be detected. (Received February 20, 1984; Accepted December 5, 1984) 相似文献
6.
Effects on positive phototaxis and the cell motility of 7 cationsin 5mM MOPS (morpholinopropane sulfonic acid) buffer (pH 7.0)containing 0.16 mM NaCl, 0.68 mM KCl, 0.5 mM CaCl2 and 0.16mM MgCl2 were studied in the unicellular flagellate Cryptomonaswith a photoelectrical measuring apparatus and photomicrography.When calcium ion was removed from the medium by adding 1 mMEGTA (ethylene glycol-bis-(ß-amino-ethylether)-N,N'-tetraaceticacid), the phototactic response was totally inhibited, but theswimming rate was not much affected. The effect of EGTA waspartially reversed by the addition of 1 mM CaCl2. When 15mMKCl or RbCl was added to the medium, phototaxis was greatlyinhibited, but there was no significant influence on the swimmingrate. Similar but less inhibitory effects were induced in thepresence of NaCl, LiCl and CsCl. KCl-induced inhibition waspartially removed by the addition of 15 mM CaCl2 or MgCl2. (Received June 25, 1982; Accepted September 27, 1982) 相似文献
7.
In vivo regulation of glycolysis and characterization of sugar: phosphotransferase systems in Streptococcus lactis. 总被引:29,自引:22,他引:7
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J Thompson 《Journal of bacteriology》1978,136(2):465-476
Two novel procedures have been used to regulate, in vivo, the formation of phosphoenolpyruvate (PEP) from glycolysis in Streptococcus lactis ML3. In the first procedure, glucose metabolism was specifically inhibited by p-chloromercuribenzoate. Autoradiographic and enzymatic analyses showed that the cells contained glucose 6-phosphate, fructose 6-phosphate, fructose-1,6-diphosphate, and triose phosphates.Dithiothreitol reversed the p-chloromercuribenzoate inhibition, and these intermediates were rapidly and quantitatively transformed into 3- and 2-phosphoglycerates plus PEP. The three intermediates were not further metabolized and constituted the intracellular PEP potential. The second procedure simply involved starvation of the organisms. The starved cells were devoid of glucose 6-phosphate, fructose 6-phosphate, fructose- 1,6-diphosphate, and triose phosphates but contained high levels of 3- and 2-phosphoglycerates and PEP (ca. 40 mM in total). The capacity to regulate PEP formation in vivo permitted the characterization of glucose and lactose phosphotransferase systems in physiologically intact cells. Evidence has been obtained for "feed forward" activation of pyruvate kinase in vivo by phosphorylated intermediates formed before the glyceraldehyde-3-phosphate dehydrogenase reaction in the glycolytic sequence. The data suggest that pyruvate kinase (an allosteric enzyme) plays a key role in the regulation of glycolysis and phosphotransferase system functions in S. lactis ML3. 相似文献
8.
The cell-membrane resistance (Rm) of Vigna hypocotyls was examined,and the effects of osmotic stress, ionic stress and IAA on Rmwere investigated. Rm decreased by 64 to 77% under osmotic stressin the presence of absorbable solutes (40 mM sorbitol, 15 mMKC1, 30 mM sucrose; or 40 mM sorbitol, 15 mM KC1, 30 mM sucroseplus 104 M IAA) or under ionic stress (50 mM NaCl or50 mM KC1). Rm was not changed by perfusion with 104M IAA. Therefore, the hyper-polarizations of the membrane potentialobserved in both cases should be ascribed totally to the activationof the electrogenic proton pump. Although Rm showed an increaseof 1.6 fold when the hypocotyls were subjected to osmotic stress(100 mM sorbitol or 100 mM sorbitol plus 104 M IAA),83.6% or 92.4% of the hyperpolarization of the membrane potential(Vpx was also the result of the activation of the pump. Theresults, calculated on the basis of the current source model,support the viewpoint that the hyperpolarization of the cellmembrane potential of Vigna hypocotyls under osmotic stress,ionic stress or in the presence of IAA is an expression of theactivation of the proton pump, and is not caused by an increasein Rm.
1 Present address: Researchers and Planners of Natural Environment, Yotsugi Bldg. (2F), 1-5-4 Horinouchi, Suginami-Ku, Tokyo,166 Japan
2 Present address: Graduate School of Integrated Science, YokohamaCity University, 22-2 Seto, Kanazawa-Ku, Yokohama, 236 Japan (Received February 14, 1991; Accepted July 24, 1991) 相似文献
9.
Maximum activity of phosphoenolpyruvate carboxylase (PEPC, EC4.1.1.31) was detected at the stationary phase of growth ofCatharanthus roseus cells in a heterotrophic culture. The activityof PEPC, after partial purification by fractionation with ammoniumsulphate and chromatography on Q-Sepharose, was greatly influencedby pH. The Km of phosphoenolpyruvate (PEP) was 23 µM atpH 8·0 and 45 µM at pH 7·4. Malate, aspartate,citrate, ATP, pyrophosphate and Pi acted as inhibitors of PEPC,but the extent of inhibition varied in each case with the pHof the reaction mixture. By contrast, glucose-6-phosphate, fructose-1,6-bisphosphateand acetyl-CoA, known as stimulators of the activity of PEPCfrom other sources, had little or no effect on the activityof the partially purified PEPC. The possible role and mechanismof regulation of PEPC in C. roseus cells are discussed.Copyright1994, 1999 Academic Press Catharanthus roseus, Apocynaceae, Madagascar periwinkle, suspension culture, phosphoenolpyruvate carboxylase, enzyme kinetics, glycolysis 相似文献
10.
A simple method for continuous spectrophotometric assay of fructose-1,6-bisphosphate aldolase is described. The method is based on the reactivity of the product triose phosphates with cyanide to form compounds capable of the reduction of cytochrome c. At the concentrations employed, cyanide, acting catalytically, reacts with the enediol tautomer of the triose phosphates to generate the reductants, which reduce cytochrome c causing increased absorbance at 550 nm. The rate of increase in the rate of appearance of 550-nm absorbance is directly proportional to the concentration of aldolase present. The procedure is particularly useful for Class I aldolases, since the assay must be run under mildly alkaline conditions. 相似文献
11.
Sulphite at concentrations from 0.05 to 5.0 mM was supplied to illuminated,
detached poplar (Populus deltoides Bart. ex Marsh)
leaves via the transpiration stream. The rate of CO2 fixation and
partitioning of newly fixed carbon between sucrose and starch were measured
and compared with the contents of selected phosphorylated intermediates,
the contents of fructose-2,6-bisphosphate (Fru2,6BP) and the activation of
sucrose-phosphate synthase (SPS). Supplying leaves with 0.5 mM sulphite led to an increase in the
sucrose/starch partitioning ratio without altering the rate of
14CO2 fixation. The increase in sucrose synthesis
compared to starch synthesis was accompanied by relatively small changes of
3-phosphoglyceric acid (PGA), fructose-1,6-bisphosphate (Fru1,6BP), hexose
phosphates (hexose-)), uridine 5'-diphosphoglucose (UDPGlc), an
accumulation of triose phosphates (triose-P), an activation of SPS, and
decreased Fru2,6BP contents. Supplying leaves with 1.0 mM sulphite
decreased 14CO2 assimilation and increased
partitioning of fixed carbon into starch. A selective inhibition of sucrose
synthesis was accompanied by an accumulation of triose-P, Fru1,6BP,
hexose-P, and a decrease of PGA contents. There was also a large increase
of Fru2,6BP contents and a decline in the activation of SPS. It could be
argued that sulphite affects the allocation of photosynthetic carbon to
sucrose and that sulphite can inhibit photosynthesis via a selective
inhibition of sucrose synthesis. 相似文献
12.
Although salinity is one of the major problems limiting agriculturalproduction around the world, the underlying mechanisms of highNaCl perception and tolerance are still poorly understood. Theeffects of different bathing solutions and fusicoccin (FC),a known activator of plasma membrane ATPase, on plasma membranepotential (Em) and net fluxes of Na+, K+and H+were studied inwheat suspension cells (Triticum aestivum) in response to differentNaCl treatments. Emof cells in Murashige and Skoog (MS) mediumwas less negative than in cells exposed to a medium containing10 mM KCl + 0.1 m M CaCl2(KSM) and to a basic salt medium (BSM),containing 1 m M KCl and 0.1 m M CaCl2. Multiphasic Na+accumulationin cells was observed, peaking at 13 min after addition of 120m M NaCl to MS medium. This time scale was in good agreementwith net Na+flux changes measured non-invasively by moving ion-selectivemicroelectrodes (the MIFE system). When 120 m M NaCl was addedto all media studied, a quick rise of Na+influx was reversedwithin the first 20 min. In both 120 and 20 m M NaCl treatmentsin MS medium, net Na+efflux was observed, indicating that activeNa+transporters function in the plant cell response to saltstress. Lower external K+concentrations (KSM and BSM) and FCpre-treatment caused shifts in Na+fluxes towards net influxat 120 m M NaCl stress. Copyright 2000 Annals of Botany Company Sodium, potassium, proton, membrane potential, fusicoccin, salt stress, wheat, Triticum aestivum 相似文献
13.
The metabolite levels in the mesophyll of leaves of Zea mays L. have been compared with the regulatory properties of the cytosolic fructose-1,6-bisphosphatase from the mesophyll to show how withdrawal of triose phosphate for sucrose synthesis is reconciled with generation of the high concentrations of triose phosphate which are needed to allow intercellular diffusion of carbon during photosynthesis. i) A new technique is presented for measuring the intercellular distribution of metabolites in maize. The bundle-sheath and mesophyll tissues are partially separated by differential homogenization and filtration through nylon nets under liquid nitrogen. ii) considerable gradients of 3-phosphoglycerate, triose phosphate, malate and phosphoenolpyruvate exist between the mesophyll and bundle sheath which would allow intercellular shuttles to be driven by diffusion. These gradients could result from the distribution of electron transport and the Calvin cycle in maize leaves. iii) consequently, the mesophyll contains high concentrations of triose phosphate and fructose-1,6-bisphosphate. iv) Most of the regulator metabolite fructose-2,6-bisphosphate, is present in the mesophyll. v) The cytosolic fructose-1,6-bisphosphatase has a lower substrate affinity than that found for the enzyme from C3 species, especially in the presence of inhibitors like fructose-2,6-bisphosphate. vi) This lowered affinity for substrate makes it possible to reconcile use of triose phosphate for sucrose synthesis with the maintenance of the high concentration of triose phosphate in the mesophyll needed for operation of photosynthesis in this species.Abbreviations DHAP
Dihydroxyacetonephosphate
- Fru1,6-bisP
fructose-1,6-bisphosphate
- Fru2,6bisP
fructose-2,6-bisphosphate
- PEP(Case)
phosphoenolpyruvate (carboxylase)
- PGA
3-phosphoglycerate
- Rubisco
ribulose-1,5-bisphosphate carboxylase 相似文献
14.
Twenty days’ exposure to 50 or 100 mM NaCl in the rooting medium substantially increased fresh and dry weights of seedling
shoots of the recretohalophyte Limonium sinense while 200 or 300 mM were increasingly inhibitory. KCl treatment was only slightly stimulating (50 mM) or strongly inhibitory
(100–300 mM). Lesser effects on leaf area were also seen. Diameter of foliar salt glands was significantly larger than that
of controls in 100 and 200 mM NaCl with the effect being reversed at higher concentrations. Gland enlargement was also observed
in the presence of 100 mM KCl, while larger concentrations reduced gland size. Generally, gland diameter was larger in the
presence of NaCl than in KCl. NaCl and KCl also increased gland number per leaf and secretion rate per gland. At 100 and 200 mM
NaCl or KCl, Na+ secretion per leaf from NaCl-treated plants exceeded K+ secretion rate from KCl-treated plants while at 200 mM, Na+ secretion per gland was significantly higher for Na+ than for K+. Evidence of cell death in leaves of salt-treated plants using Evans blue staining indicates that release of cell contents
through loss of membrane integrity contributed to the secretion values. We conclude that the greater tolerance of L. sinenseto to NaCl compared to KCl is linked to the more effective secretion of Na+ than of K+ and, in turn, to a greater stimulation of salt gland formation and activity and larger gland diameter. 相似文献
15.
Ca Fluxes and Membrane Potentials in Nitella translucens 总被引:4,自引:0,他引:4
The concentrations of Ca have been measured in the flowing cytoplasmand the vacuole of the single cells of Nitella translucens,the cells being immersed in an artificial pond Water (composition:NaCl, 1.0 mM; KCl, 0.1 mM; CaCl2, 0. mM). In the flowing cytoplasmthe total concentration is 8 mM and in the vacuole 12 mM. Measurementsof the electrical potential differences across the plasmalemmaand tonoplast membranes show that the cytoplasm is at a potentialof 134 mV with respect to the bathing medium and 24mV with respect to the vacuole. An attempt has been made tomeasure the tracer fluxes of Ca and it is shown that the cellsare not in flux equilibrium. The influx is 0.046 µµmoles cm2 sec1; the efflux was too small to measurewith any degree of accuracy. The observed potential differences across both membranes arecompared with the Nernst potentials for Ca. This analysis showsthat Ca is not in electrochemical equilibrium across eithermembrane and that the driving forces on Ca are directed fromthe bathing medium and the vacuole into the cytoplasm. It issuggested that there is no necessity for a metabolically drivenCa pump at the plasmalemma because the low cytoplasmic Ca contentcould be due to the low permeability of the plasmalemma; theGoldman flux equation gives a value of PCa = 4.3x108cm sec1. A Ca pump at the tonoplast appears to be necessaryto explain the steep electrochemical potential gradient fromthe vacuole to the cytoplasm. The efflux of Ca from the isolated cell wall has been measured.From these measurements it was possible to estimate the concentrationof indiffusible anions in the Donnan Free Space; the value obtainedwas 0.74 equiv. 1.1. 相似文献
16.
Sodium Chloride Compartmentation in Leaf Vacuoles of the Halophyte Suaeda maritima (L.) Dum. and its Relation to Tonoplast Permeability 总被引:1,自引:0,他引:1
Single channel properties, whole vacuole currents and protonpumping capacity were investigated in the intact vacuoles andmembrane patches of leaf tonoplast from the halophyte Suaedamaritima. ATP-dependent proton pumping capacity was similarto non-halophytes whether the plants were or were not grownwith added sodium chloride (200 mM). The most abundant ion channelwas inward rectifying and had a single channel conductance of58 pS in symmetrical KCl solutions (100 mM) to 170 pS usingphysiological conditions (50/150 mM KCl/NaCl cytoplasmic side,50/450 mM KCl/NaCl vacuolar side). The channel showed all thecharacteristics of the SV type channel described in many otherspecies. In the open state these channels caused tonoplast conductancesin excess of 0.5 nS m2 but conductances were much lowerusing physiological ion concentrations and membrane potentials.In spite of the poor selectivity and the potentially large tonoplastconductance it is calculated that compartmentation of NaCl inleaf vacuoles can be sustained by about 30% of ATP-dependentproton pumping capacity. The results do not indicate any specialadaptation of the tonoplast ion channels in the halophyte. Key words: Ion-channels, patch-clamp, salt-tolerance, vacuole 相似文献
17.
Biochemical Limitations to Carbon Assimilation in C3 Plants--A Retrospective Analysis of the A/Ci Curves from 109 Species 总被引:9,自引:0,他引:9
Species-specific differences in the assimilation of atmosphericCO2 depends upon differences in the capacities for the biochemicalreactions that regulate the gas-exchange process. Quantifyingthese differences for more than a few species, however, hasproven difficult. Therefore, to understand better how speciesdiffer in their capacity for CO2 assimilation, a widely usedmodel, capable of partitioning limitations to the activity ofribulose-1,5-bisphosphate carboxylase-oxygenase, to the rateof ribulose 1,5-bisphosphate regeneration via electron transport,and to the rate of triose phosphate utilization was used toanalyse 164 previously published A/Ci, curves for 109 C3 plantspecies. Based on this analysis, the maximum rate of carboxylation,Vcmax, ranged from 6µmol m2 s1 for the coniferousspecies Picea abies to 194µmol m2 s1 forthe agricultural species Beta vulgaris, and averaged 64µmolm2 s1 across all species. The maximum rate ofelectron transport, Jmax, ranged from 17µmol m2s1 again for Picea abies to 372µmol m2 s1for the desert annual Malvastrum rotundifolium, and averaged134µmol m2 s1 across all species. A strongpositive correlation between Vcmax and Jmax indicated that theassimilation of CO2 was regulated in a co-ordinated manner bythese two component processes. Of the A/Ci curves analysed,23 showed either an insensitivity or reversed-sensitivity toincreasing CO2 concentration, indicating that CO2 assimilationwas limited by the utilization of triose phosphates. The rateof triose phosphate utilization ranged from 4·9 µmolm2 s1 for the tropical perennial Tabebuia roseato 20·1 µmol m2 s1 for the weedyannual Xanthium strumarium, and averaged 10·1 µmolm2 s1 across all species. Despite what at first glance would appear to be a wide rangeof estimates for the biochemical capacities that regulate CO2assimilation, separating these species-specific results intothose of broad plant categories revealed that Vcmax and Jmaxwere in general higher for herbaceous annuals than they werefor woody perennials. For annuals, Vcmax and Jmax averaged 75and 154 µmol m2 s1, while for perennialsthese same two parameters averaged only 44 and 97 µmolm2 s1, respectively. Although these differencesbetween groups may be coincidental, such an observation pointsto differences between annuals and perennials in either theavailability or allocation of resources to the gas-exchangeprocess. Key words: A/Ci curve, CO2 assimilation, internal CO2 partial pressure, photosynthesis 相似文献
18.
Copper chloride was evaluated as a specific inhibitor of neuralresponses to sweet taste stimuli in the goldern hamster (Mesocricetusauratus). The chorda tympani whole-nerve response to taste stimuliwas recorded before and after the tongue was treated for 30s with 0.01, 0.1 and 1 mM CuCl2. Sweet stimuli [sucrose, fructose,saccharin (calcium salt), D-phenylalanine], which primarilystimulate chorda tympani S fibers, and non-sweet stimuli (NaCl,NH4Cl) were used. At 0.01 mM, copper chloride had little effect.At 0.10 mM it partially inhibited responses to sucrose and saccharin,but had little effect on responses to D-Phe, fructose, NaCl,NH4Cl, or a mixture of sucrose plus L-Phe. L-Phe, which hasthe same chelating properties as D-Phe, is not an S-fiber stimulusand likely reduced sucrose inhibiton by chelating the cupricion.Analysis of concentrationresponse functions revealedthat 0.1 mM copper chloride inhibited the neural response tolow concentrations of sucrose by about 25%, but did not significantlyinhibit high concentrations of surcrose, suggesting competitiveinhibition. In contrast, 0.1 mM CuCl2 reduced saccharin responsesby 25% throughtout the effective range, suggesting non-competitiveinhibition. Occupation of a saccharide receptor site by coppermay interfere with dimer but not monomer reception and distortthe saccharin receptor site. At 1 mM, CuCl2 non-competitivelyinhibited responses to sucrose, fructose, saccharin and thenon-sweet NaCl (an N-fiber stimulus), but not NH4Cl (an H-fiberstimulus). The mechanisms of copper chloride inhibition aredifficult to establish because its effects are weak at concentrationswhere they are specific. 相似文献
19.
《Plant & cell physiology》1978,19(4):715
Please replace the paragraph Culture of material in Materialand method on page 574 (Fujii, Shimmen and Tazawa), Vol. 19,No. 4 with the following corrected paragraph. Materials and methods Culture of material Spirogyra sp. used for the experiments was collected in theriver Kamogawa in Kyoto. Cylindrical cells composing the filamentwere 55 µm in diameter and 100200 µm in length.Each cell usually had one spiral ribbon-like chloroplast. Thealga was cultured in slightly modified Reichardt's medium (27),1000 ml of which contained: 200 mg KNO3, 20 mg K2HPO4, 10mgH3BO3, 6.6 mg FeSO4?7H2O, 25 mg Na2EDTA (ethylenediamine tetraaceticacid disodium salt), 200 mg NaHCO3, 50 mg CaSO4?2H2O, 10mg MgSO4?7H2O,0.5 mg ZnSO4?7H2O, 5mg MnCl2?4H2O, 24 µg Na2MoO4, 2 µgCoCl2?6H2O, 500 mg Tris. The pH was adjusted to 7.4 with HCl.The alga was cultured in a Petri dish at 20?1?C under a 16 hr8hr light-dark regime. The light intensity was about 2000 lux.Under such conditions, the cells divided once a day fairly synchronously. Experimental solutions Artificial pond water (APW) containing 0.1 mM each of KCl, NaCland CaCl2 相似文献
20.
MURALITHARAN MORLEY S.; CHANDLER STEPHEN F.; VAN STEVENINCK REINHARD F. M. 《Annals of botany》1992,69(5):459-465
Non-selected and Na2SO-, K2SO4- or KCl-selected callus culturesof Vaccinium corymbosum L. cv. Blue Crop were grown on mediasupplemented with 0, 25 and 50 mM Na2SO4 (non-selected and Na2SO(-selectedonly), 0, 25 and 50mMK2SO4 (non-selected and K2SO4-selectedonly) or 0, 50 and 100 mM KCl (non-selected and KCl-selectedonly). On all media, growth of selected callus (on a fresh-weightor dry-weight basis) was greater than that of non-selected callus,and selected callus grew optimally on the level and type ofsalt on which it was selected. Selected callus was friable andmaintained a higher f. wt:d. wt ratio. Tissue water potentialin selected callus was more negative than in non-selected callus. Flame photometry and chloridometry showed Na+, K+ and Claccumulated in callus to concentrations equal to or greaterthan the initial concentration in the medium. Turbidometry showedthat tissue SO42- concentration was lower than the concentrationin the medium. In most cases selected callus accumulated moreNa+, Ksup, SO42 or Cl than non-selected callus.Vacuolar ion concentration was measured by electronprobe X-raymicroanalysis, and on most media selected callus had highervacuolar ion concentrations than non-selected callus. SO42and Cl were accumulated in the vacuoles at concentrationshigher than the external medium, but vacuolar Na+ concentrationdid not reach external concentration on Na2SO4 and on potassiumsalts was maintained between 12 and 17 mM. Vacuolar K+ concentration(approx. 142191 mM on no salt) decreased on Na2SO4 andincreased on K2SO4 and KCl. There was no precise correlation between total or specific ionaccumulation (Na+, K+, SO42 and Cl and fresh-weightyield. Results suggest that selection results in adaptationin response to decreased water potential of the medium. Vaccinium corymbosum, blueberry, electronprobe X-ray microanalysis, callus, in vitro selection, salt tolerance, KCl, K2SO4, Na2SO4 相似文献