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1.
Two genotypes of mungbean differing in the leaf shape, K-851 (trifoliate) and a mutant (pentafoliate), were exposed to salinity (0, 2.5, 5, 10 dS m–1) for 3, 6 and 9 d at flowering stage (40 – 45 d after sowing) to see the effect of salinity on nodule functioning. In both the genotypes, osmotic potential (s) and relative water content (RWC) of nodules decreased significantly, and proline content increased with increasing the salinity. The s of nodules was more decreased in the mutant than in genotype K-851, while reverse was true for RWC and proline accumulation. A remarkable increase in ethylene evolution was noticed from nodulated roots with the increasing level and duration of salinity and was much higher in K-851. A sharp decline in leghemoglobin content and acetylene reduction assay (ARA) of the nodules was observed with the salinity and this decrease was more marked in K-851 than the mutant. N content declined while Na+/K+ ratio and Cl content increased significantly. The mutant maintained better N status but lower Na+/K+ ratio and Cl content in nodules than K-851. Nodule dry matter also declined with salinity and the decrease was more expressed in K-851. Thus the functioning of nodules in the mutant was better than in the genotype K-851 under stress conditions.  相似文献   

2.
The effects of salinity on growth, leaf nutrient content, water relations, gas exchange parameters and chlorophyll fluorescence were studied in six-month-old seedlings of citrus (Citrus limonia Osbeck) and rooted cuttings of olive (Olea europaea L. cv. Arbequina). Citrus and olive were grown in a greenhouse and watered with half strength Hoagland’s solution plus 0 or 50 mM NaCl for citrus, or plus 0 or 100 mM NaCl for olive. Salinity increased Cl and Na+ content in leaves and roots in both species and reduced total plant dry mass, net photosynthetic rate and stomatal conductance. Decreased growth and gas exchange was apparently due to a toxic effect of Cl and/or Na+ and not due to osmotic stress since both species were able to osmotically adjust to maintain pressure potential higher than in non-salinized leaves. Internal CO2 concentration in the mesophyll was not reduced in either species. Salinity decreased leaf chlorophyll a content only in citrus.  相似文献   

3.
Summary Ouabain-insensitive, furosemide-sensitive Rb+ influx (J Rb) into HeLa cells was examined as functions of the extracellular Rb+, Na+ and Cl concentrations. Rate equations and kinetic parameters, including the apparent maximumJ Rb, the apparent values ofK m for the three ions and the apparentK i for K+, were derived. Results suggested that one unit molecule of this transport system has one Na+, one K+ and two Cl sites with different affinities, one of the Cl sites related with binding of Na+, and the other with binding of K+(Rb+). A 11 stoichiometry was demonstrated between ouabain-insensitive, furosemidesensitive influxes of22Na+ and Rb+, and a 12 stoichiometry between those of Rb+ and36Cl. The influx of either one of these ions was inhibited in the absence of any one of the other two ions. Monovalent anions such as nitrate, acetate, thiocyanate and lactate as substitutes for Cl inhibited ouabain-insensitive Rb+ influx, whereas sulfamate and probably also gluconate did not inhibitJ Rb. From the present results, a general model and a specialized cotransport model were proposed: 1) In HeLa cells, one Na+ and one Cl bind concurrently to their sites and then one K+ (Rb+) and another Cl bind concurrently. 2) After completion of ion bindings Na+, K+(Rb) and Cl in a ratio of 112 show synchronous transmembrane movements.  相似文献   

4.
B. Demmig  K. Winter 《Planta》1986,168(3):421-426
Concentrations of four major solutes (Na+, K+, Cl-, proline) were determined in isolated, intact chloroplasts from the halophyte Mesembryanthemum crystallinum L. following long-term exposure of plants to three levels of NaCl salinity in the rooting medium. Chloroplasts were obtained by gentle rupture of leaf protoplasts. There was either no or only small leakage of inorganic ions from the chloroplasts to the medium during three rapidly performed washing steps involving precipitation and re-suspension of chloroplast pellets. Increasing NaCl salinity of the rooting medium resulted in a rise of Na+ und Cl- in the total leaf sap, up to approximately 500 and 400 mM, respectively, for plants grown at 400 mM NaCl. However, chloroplast levels of Na+ und Cl- did not exceed 160–230 and 40–60 mM, respectively, based upon a chloroplast osmotic volume of 20–30 l per mg chlorophyll. At 20 mM NaCl in the rooting medium, the Na+/K+ ratio of the chloroplasts was about 1; at 400 mM NaCl the ratio was about 5. Growth at 400 mM NaCl led to markedly increased concentrations of proline in the leaf sap (8 mM) compared with the leaf sap of plants grown in culture solution without added NaCl (proline 0.25 mM). Although proline was fivefold more concentrated in the chloroplasts than in the total leaf sap of plants treated with 400 mM NaCl, the overall contribution of proline to the osmotic adjustment of chloroplasts was small. The capacity to limit chloroplast Cl- concentrations under conditions of high external salinity was in contrast to an apparent affinity of chloroplasts for Cl- under conditions of low Cl- availability.Abbreviation Chl chlorophyll  相似文献   

5.
Summary Loop diuretic-sensitive (Na+,K+,Cl)-cotransport activity was found to be present in basolateral membrane vesicles of surface and crypt cells of rabbit distal colon epithelium. The presence of grandients of all three ions was essential for optimal transport activity (Na+,K+) gradien-driven36Cl fluxes weree half-maximally inhibited by 0.14 m bumetanide and 44 m furosimide. While86Rb uptake rates showed hyperbolic dependencies on Na+ and K+ concentrations with Hill coefficients of 0.8 and 0.9, respectively, uptakes were sigmoidally related to the Cl concentration, Hill coefficient 1.8, indicating a 1 Na+: 1 K+:2 Cl stoichiometry of ion transport.The interaction of putative (Na+, K+, Cl)-cotransport proteins with loop diuretics was studied from equilibrium-binding experiments using [3H]-bumetanide. The requirement for the simulataneous presence of Na+,K+, and Cl, saturability, reversibility, and specificity for diuretics suggest specific binding to the (Na+, K+, Cl)-cotransporter. [3H]-bumetanide recognizes a minimum of two classes of diuretic receptors sites. high-affinity (K D1=0.13 m;B max1 =6.4 pmol/mg of protein) and low-affinity (K D2=34 m;B max2=153 pmol/mg of protein) sites. The specific binding to the high-affinity receptor was found to be linearly competitive with Cl (K 1=60mm), whereas low-affinity sites seem to be unaffected by Cl. We have shown that only high-affinity [3H]-bumetanide binding correlates with transport inhibition raising questions on the physiological significance of diuretic receptor site heterogeneity observed in rabbit distal colon epithelium.  相似文献   

6.
Summary The Na+ requirement for active, electrogenic Cl absorption byAmphiuma small intestine was studied by tracer techniques and double-barreled Cl-sensitive microelectrodes. Addition of Cl to a Cl-free medium bathingin vitro intestinal segments produced a saturable (K m =5.4mm) increase in shortcircuit current (I sc) which was inhibitable by 1mm SITS. The selectivity sequence for the anion-evoked current was Cl=Br>SCN>NO 3 >F=I. Current evoked by Cl reached a maximum with increasing medium Na concentration (K m =12.4mm). Addition of Na+, as Na gluconate (10mm), to mucosal and serosal Na+-free media stimulated the Cl current and simultaneously increased the absorptive Cl flux (J ms Cl ) and net flux (J net Cl ) without changing the secretory Cl flux (J sm Cl ). Addition of Na+ only to the serosal fluid stimulatedJ ms Cl much more than Na+ addition only to the mucosal fluid in paired tissues. Serosal DIDS (1mm) blocked the stimulation. Serosal 10mm Tris gluconate or choline gluconate failed to stimulateJ ms Cl . Intracellular Cl activity (a Cl i ) in villus epithelial cells was above electrochemical equilibrium indicating active Cl uptake. Ouabain (1mm) eliminated Cl accumulation and reduced the mucosal membrane potential m over 2 to 3 hr. In contrast, SITS had no effect on Cl accumulation and hyperpolarized the mucosal membrane. Replacement of serosal Na+ with choline eliminated Cl accumulation while replacement of mucosal Na+ had no effect. In conclusion by two independent methods active electrogenic Cl absorption depends on serosal rather than mucosal Na+. It is concluded that Cl enters the cell via a primary (rheogenic) transport mechanism. At the serosal membrane the Na+ gradient most likely energizes H+ export and regulates mucosal Cl accumulation perhaps by influencing cell pH or HCO 3 concentration.  相似文献   

7.
Two iso-osmotic concentrations of NaCl and Na2SO4 were used for discriminating between the effects of specific ion toxicities of salt stress on pepper plants (Capsicum annuum L.) grown in hydroponic conditions, in a controlled-environment greenhouse. The two salts were applied to plants at different electrical conductivities, and leaf water relations, osmotic adjustment and root hydraulic conductance were measured. Leaf water potential (w), leaf osmotic potential (o) and leaf turgor potential (p) decreased significantly when EC increased, but the decrease was less for NaCl- than for Na2SO4-treated plants. The reduction in stomatal conductance was higher for NaCl-treated plants. There were no differences in the effect of both treatments on the osmotic adjustment, and a reduction in root hydraulic conductance and the flux of solutes into the xylem was observed, except for the saline ions (Na+, Cl and SO4 2–). Therefore, pepper growth decreased with increasing salinity because the plants were unable to adjust osmotically or because of the toxic effects of Cl, SO4 2– and/or Na+. However, turgor of NaCl-treated plants was maintained at low EC (3 and 4 dS m–1) probably due to the maintenance of water transport into the plant (decrease of stomatal conductance), which, together with the lower concentration of Na+ in the plant tissues compared with the Na2SO4 treatment, could be the cause of the smaller decrease in growth.  相似文献   

8.
Summary The bumetanide-sensitive uptake of Na+, K(Rb) and Cl has been measured at 21°C in ferrent red cells treated with (SITS+DIDS) to minimize anion flux via capnophorin (Band 3). During the time course of the influx experiments tracer uptake was a first-order rate process. At normal levels of external Na+ (150mm) the bumetanide-sensitive uptake of K+ was dependent on Cl and represented almost all of the K+ uptake, the residual flux demonstrating linear concentration dependence. The uptake of Na+ and Cl was only partially inhibited by bumetanide indicating that pathways other than (Na+K+Cl) cotransport participate in these fluxes. The diuretic-sensitive uptake of Na+ or Cl was, however, abolished by the removal of K+ or the complementary ion indicating that bumetanide-sensitive fluxes of Na+, K+ and Cl are closely coupled. At very low levels of [Na] o (<5mm) K+ influx demonstrated complex kinetics, and there was evidence of the unmasking of a bumetanide-sensitive Na+-independent K+ transport pathway. The stoichiometry of bumetanide-sensitive tracer uptake was 2Na1K3Cl both in cells suspended in a low and a high K+-containing medium. The bumetanide-sensitive flux was markedly reduced by ATP depletion. We conclude that a bumetanide-sensitive cotransport of (2Na1K3Cl) occurs as an electroneutral complex across the ferret red cell membrane.  相似文献   

9.
Photosynthetic performance of the highly salt tolerant mangrove, Avicennia marina, was compared at two sites differing insubstrate soil salinities. Carbon dioxide exchange and chlorophyll fluorescence weremonitored at a high salinity site in Durban Bay (35) and at a low salinitysite in Beachwood (< 12). Mean CO2 exchange, conductanceand transpiration were consistently higher at the high salinity site. Carbondioxide response curves indicated that carboxylation efficiency was higherand stomatal limitation lower at the Durban Bay site. PSII quantum yield,electron transport rates (ETR) and intrinsic PSII efficiency(Fv/Fm) were significantly higher at the high salinity site.Quenching analysis indicated a higher degree ofphotoinhibition/photoprotection in leaves at the low salinity site. Predawnand midday leaf water potentials were –1.6 and –3.1 MPa at Beachwood,compared to –2.6 and –3.8 MPa, respectively, at Durban Bay. Leafconcentrations of Na+, K+, Ca2+, Mg2+,Cl- and N were significantly higher at Durban Bay. Photosyntheticperformance is apparently impaired at the low salinity site in Beachwood asa result of K+ and N deficiencies in the leaves.  相似文献   

10.
Leaf gas exchange, plant growth and leaf ion content were measured in wheat (Triticum durum L. cv. HD 4502) exposed to steady- state salinities (1.6, 12.0 and 16.0 dS nr−1) for 8 weeks. Salinity reduced leaf area and number of tillers, and increased Na+ and Cl concentrations in leaves. Leaf- to- leaf gradients of these ions were observed. The oldest leaf contained 6 to 8 times more Na+ and Cl than the flag leaf. Net photosynthetic rate (PN), transpiration rate (E) and stomatal conductance (gS) were the highest in flag leaf, declined in the middle and fully expanded leaves, and were minimum in the oldest leaves. These processes were reduced by salinity with similar leaf- to- leaf gradients. Intercellular CO2 concentrations in the older leaves were higher than in the flag leaf in non-saline plants, and increased similarly with salinity. Leaf age was the major factor in reducing PN, and senescence processes were promoted by salinity.  相似文献   

11.
Above-canopy sprinkler irrigation with saline water favours the absorption of salts by wetted leaves and this can cause a yield reduction additional to that which occurs in salt-affected soils. Outdoor pot experiments with both sprinkler and drip irrigation systems were conducted to determine foliar ion accumulation and performance of maize and barley plants exposed to four treatments: nonsaline control (C), salt applied only to the soil (S), salt applied only to the foliage (F) and salt applied to both the soil and to the foliage (F+S). The EC of the saline solution employed for maize in 1993 was 4.2 dS m–1 (30 mM NaCl and 2.8 mM CaCl2) and for barley in 1994, 9.6 dS m–1 (47 mM NaCl and 23.5 mM CaCl2). The soil surface of all pots was covered so that in the F treatment the soil was not salinized by the saline sprinkling and drip irrigation supplied nutrients in either fresh (treatments C and F) or saline water (treatments S and F+S).Saline sprinkling increased leaf sap Na+ concentrations much more than did soil salinity, especially in maize, even though the saline sprinkling was given only two or three times per week for 30 min, whereas the roots of plants grown in saline soil were continuously exposed to salinity. By contrast, leaf sap Cl concentrations were increased similarly by saline sprinkling and soil salinity in maize, and more by saline sprinkling than saline soil in barley. It is concluded that barley leaves, and to a greater extent maize leaves, lack the ability to selectively exclude Na+ when sprinkler irrigated with saline water. Moreover, maize leaves selectively absorbed Na+ over Cl whereas barley leaves showed no selectivity. When foliar and root absorption processes were operating together (F+S treatment) maize and barley leaves accumulated 11–14% less Na+ and Cl than the sum of individual absorption processes (treatment F plus treatment S) indicating a slight interaction between the absorption processes. Vegetative biomass at maturity and cumulative plant water use were significantly reduced by saline sprinkling. In maize, reductions in biomass and plant water use relative to the control were of similar magnitude for plants exposed only to saline sprinkling, or only to soil salinity; whereas in barley, saline sprinkling was more detrimental than was soil salinity. We suggest that crops that are salt tolerant because they possess root systems which efficiently restrict Na+ and Cl transport to the shoot, may not exhibit the same tolerance in sprinkler systems which wet the foliage with saline water. ei]T J Flowers  相似文献   

12.
Summary Ouabain-resistant effluxes from pretreated cells containing K+/Na+=1.5 into K+ and Na+ free media were measured.Furosemide-sensitive cation effluxes from cells with nearly normal membrane potential and pH were lower in NO 3 media than in Cl media; they were reduced when pH was lowered in Cl media. When the membrane potential was positive inside furosemide increased the effluxes of Na+ and K+ (7 experiments). With inside-positive membrane potential thefurosemideinsensitive effluxes were markedly increased, they decreased with decreasing pH at constant internal Cl and also when internal Cl was reduced at constant pH. The correlation between cation flux and the membrane potential was different for cells with high or low internal chloride concentrations. The data with chloride47mm showed a better fit with the single-barrier model than with the infinite number-of-barriers model. With low chloride no significant correlation between flux and membrane potential was found. The data are not compatible with pure independent diffusion of Na+ and K+ in the presence of ouabain and furosemide.  相似文献   

13.
Summary The function of the caecal bulb, and its adaptation to chronic high- or low-Na+ intake, was investigated by in vivo perfusion of anaesthetised birds. Effects of acute aldosterone injection (125 g·kg–1 body mass) were also measured.Evidence was found for primary active net absorption of Na+, inducing parallel Na-linked absorption of water and Cl and secretion of K+. Around 20–35% of total Cl absorption and K+ secretion were independent of Na+ fluxes, and these components appear to be driven by passive processes with apparent conductances of 6.3×10–3 (G Cl) and 1.1×10–3 (G K) S·cm–2.Acetate (40mM) stimulated Na+ fluxes (8.5–9.9 Eq·cm–2·h–1) and Na-linked water fluxes (27–44 l·cm–2·h–1). Increased coupling ratios (2.9–4.6 l·Eq–1) and other data indicate that these effects may be due to increased osmotic permeabilities of barriers involved in the Na-linked water transfer pathway.Low-Na+ maintenance enhanced EPD (49–69 mV, serosa positive) and all net fluxes:J Na (6.8–11.6);J K (–3.2––4.3);J Cl (4.3–5.6 Eq·cm serosal area–2·h–1);J v (28–43 l·cm–2·h–1) (mucosal-serosal fluxes positive).Acute aldosterone enhancedJ Na (10.8–14.0 Eq·cm–2·h–1) and EPD (54–66 mV) by 3 h after injection, but had no effect on the Na-linked components ofJ K orJ Cl.Abbreviations ECPD, EPD Electrochemical or electrical potential difference - G Cl ,G K ionic conductances (Cl, K+) - J v ,J ion net volume or ion flux rate, mucosa-serosa positive;P d (Cl) diffusive permeability coefficient (of Cl) - SEDM standard error of difference between means  相似文献   

14.
Summary Isolated posterior gills from Chinese crabs (Eriocheir sinensis) acclimated to tap-water were perfused and bathed with full, physiological saline (containing Na+ and Cl). Under these conditions they developed an outside positive transepithelial potential difference (PDte). Substitution of Na+ by choline on both sides of the epithelium resulted in a substantial hyperpolarization of the PDte, while substitution of Cl by gluconate reverses PDte to outside negative values.The magnitudes of the potential differences were strongly related to the adaptation media (artificial seawater or tap-water).The KCN-sensitive, outside positive PDte was shown to be strongly dependent on Cl. Application of thiocyanate and 4-acetamido-4-isothiocyanato-stilbene-2,2 disulfonic acid (SITS) to the bath solution resulted in a reduction of the PDte, while the Cl-channel blocker, diphenylamine-2-carboxylic acid (DPC), showed no effect. The PDte was markedly reduced by acetazolamide, an inhibitor of carbonic anhydrase (CA), and these results are discussed with reference to the presence of a Cl/HCO 3 -exchanger in the apical membrane.Chloride was shown to pass the basolateral membrane via Cl-channels: Diphenylamine-2-carboxylic acid (DPC) reduced the PDte with an IC50 of 3.7×10–5 mol/l when added to the perfusion saline. A basolateral K+-channel and its linkage to Cl uptake could be demonstrated by using the K+-channel blocker, Ba2+, or increased K+ concentrations in the perfusion saline (PDte decrease). Ouabain did not reduce the PDte under nominally Na+-free conditions, indicating that the Cl transport is independent of the Na+/K+-ATPase. In this paper we shall discuss the possible energy sources and linkages between pH regulation and active Cl absorption under these experimental conditions.Abbreviations A9C anthracene-9-carboxylic acid - CA carbonic anhydrase - DMSO dimethylsulfoxide - DPC diphenylamino-2-carboxylic acid - PD te transepithelial potential difference - SITS 4-acetamido-4-isothiocyanato-stilbene-2,2-disulfonic acid - TEA tetraethyl-ammoniumchloride  相似文献   

15.
Summary Bidirectional transepithelial K+ flux measurements across high-resistance epithelial monolayers of MDCK cells grown upon millipore filters show no significant net K+ flux.Measurements of influx and efflux across the basal-lateral and apical cell membranes demonstrate that the apical membranes are effectively impermeable to K+.K+ influx across the basal-lateral cell membranes consists of an ouabain-sensitive component, an ouabain-insensitive component, an ouabain-insensitive but furosemide-sensitive component, and an ouabain-and furosemide-insensitive component.The action of furosemide upon K+ influx is independent of (Na+–K+)-pump inhibition. The furosemide-sensitive component is markedly dependent upon the medium K+, Na+ and Cl content. Acetate and nitrate are ineffective substitutes for Cl, whereas Br is partially effective. Partial Cl replacement by NO3 gives a roughly linear increase in the furosemide-sensitive component. Na+ replacement by choline abolishes the furosemide-sensitive component, whereas Li+ is a partially effective replacement. Partial Na+ replacement with choline gives an apparent affinity of 7mm Na, whereas variation of the external K+ content gives an affinity of the furosemide-sensitive component of 1.0mm.Furosemide inhibition is of high affinity (K 1/2=3 m). Piretanide, ethacrynic acid, and phloretin inhibit the same component of passive K+ influx as furosemide; amiloride, 4,-aminopyridine, and 2,4,6-triaminopyrimidine partially so. SITS was ineffective.Externally applied furosemide and Cl replacement by NO 3 inhibit K+ efflux across the basal-lateral membranes indicating that the furosemide-sensitive component consists primarily of KK exchange.  相似文献   

16.
Summary After swelling in hyposmotic solution, Ehrlich ascites tumor cells shrink towards their original volume. Upon restoration of isosmolality (300 mOsm) the cells initially shrink but subsequently recover volume. This regulatory volume increase (RVI) is completely blocked when [Na+] o or [Cl] o is reduced by 50% in the presence of normal [K+] o . With normal [NaCl] o but less than 2 mm [K+] o , not only is volume recovery blocked but the cells lose KCl and shrink. When [K+] o is increased to 5 mm there is a rapid net uptake of K+ and Cl which results in volume recovery. This suggests that the reswelling phase requires the simultaneous presence of Na+, K+, and Cl. Although ouabain has no effect on volume recovery, bumetanide completely blocks RVI by inhibiting a cotransport pathway that mediates the net uptake of Na+, K+ and Cl in the ratio of 1Na1K2Cl. Na+ that accumulates is then replaced by K+ via the Na/K pump.I wish to thank my colleague, Dr. Thomas C. Smith for advice and helpful comments during the course of these studies. The excellent technical assistance provided by Rebecca Corcoran-Merrill is gratefully acknowledged.This investigation was supported by Grant CA 32927 from the National Cancer Institute, U.S. Public Health Service.  相似文献   

17.
Can elevated CO(2) improve salt tolerance in olive trees?   总被引:2,自引:0,他引:2  
We compared growth, leaf gas exchange characteristics, water relations, chlorophyll fluorescence, and Na+ and Cl concentration of two cultivars (‘Koroneiki’ and ‘Picual’) of olive (Olea europaea L.) trees in response to high salinity (NaCl 100 mM) and elevated CO2 (eCO2) concentration (700 μL L−1). The cultivar ‘Koroneiki’ is considered to be more salt sensitive than the relatively salt-tolerant ‘Picual’. After 3 months of treatment, the 9-month-old cuttings of ‘Koroneiki’ had significantly greater shoot growth, and net CO2 assimilation (ACO2) at eCO2 than at ambient CO2, but this difference disappeared under salt stress. Growth and ACO2 of ‘Picual’ did not respond to eCO2 regardless of salinity treatment. Stomatal conductance (gs) and leaf transpiration were decreased at eCO2 such that leaf water use efficiency (WUE) increased in both cultivars regardless of saline treatment. Salt stress increased leaf Na+ and Cl concentration, reduced growth and leaf osmotic potential, but increased leaf turgor compared with non-salinized control plants of both cultivars. Salinity decreased ACO2, gs, and WUE, but internal CO2 concentrations in the mesophyll were not affected. eCO2 increased the sensitivity of PSII and chlorophyll concentration to salinity. eCO2 did not affect leaf or root Na+ or Cl concentrations in salt-tolerant ‘Picual’, but eCO2 decreased leaf and root Na+ concentration and root Cl concentration in the more salt-sensitive ‘Koroneiki’. Na+ and Cl accumulation was associated with the lower water use in ‘Koroneiki’ but not in ‘Picual’. Although eCO2 increased WUE in salinized leaves and decreased salt ion uptake in the relatively salt-tolerant ‘Koroneiki’, growth of these young olive trees was not affected by eCO2.  相似文献   

18.
The chickpea genotype, CSG-8962 was raised in screenhouse to study salinity induced changes in ethylene evolution, antioxidative defence system and membrane integrity in relation to changes in plant water and mineral content. At vegetative stage (60 d after sowing), the plants were exposed to single saline irrigation (0, 2.5, 5.0 and 10.0 dS m–1). Sampling was done 3 d after saline treatments. The other sets of treated plants were re-irrigated with water and sampled after further 3 d. The w of leaf and s of leaf and roots decreased from –0.47 to –0.61 MPa, –0.67 to –1.23 MPa and from –0.57 to –0.95 MPa, respectively, with increasing salinity. Similarly, RWC of leaf and roots reduced from 87.5 to 72.3 % and 96.7 to 84.35 %, respectively. The decline in s of roots was mainly due to accumulation of proline and total soluble sugar. With salinity, increase in ethylene evolution, 1-aminocyclopropane-1-carboxylic acid (ACC) content and ACC oxidase activity was reported. Similarly, marked increase in H2O2 content (20 – 182 %) and lipid peroxidation (43 – 170 %) was observed. The defense mechanism activated in roots was confirmed by the increased activities of superoxide dismutase (SOD), peroxidase (POX), ascorbate peroxidase (APX), glutathione transferase (GTase), glutathione reductase (GR) and catalase (CAT) but ascorbic acid (AA) content was decreased. About 3-fold increase in Na+/K+ ratio and 2.5 fold increase in Cl content was observed. Upon desalinization, a partial recovery was observed in most of the parameters studied.  相似文献   

19.
Summary The fluorescence intensity of the dye 1,1-dipropyloxadicarbocyanine (DiOC3-(5)) has been measured in suspensions of Ehrlich ascites tumor cells in an attempt to monitor their membrane potential (V m ) under different ionic conditions, after treatment with cation ionophores and after hypotonic cell swelling. Calibration is performed with gramicidin in Na+-free K+/choline+ media, i.e., standard medium in which NaCl is replaced by KCl and cholineCl and where the sum of potassium and choline is kept constant at 155mm. Calibration by the valinomycin null point procedure described by Lariset al. (Laris, P.C., Pershadsingh, A., Johnstone, R.M., 1976,Biochim. Biophys. Acta 436:475–488) is shown to be valid only in the presence of the Cl-channel blocker indacrinone (MK196). Distribution of the lipophilic anion SCN as an indirect estimation of the membrane potential is found not to be applicable for the fast changes inV m reported in this paper. Incubation with DiOC3-(5) for 5 min is demenstrated to reduce the Cl permeability by 26±5% and the NO 3 permeability by 15±2%, while no significant effect of the probe could be demonstrated on the K+ permeability. Values forV m , corrected for the inhibitory effect of the dye on the anion conductance, are estimated at –61±1 mV in isotonic standard NaCl medium, –78±3 mV in isotonic Na+-free choline medium and –46±1 mV in isotonic NaNO3 medium. The cell membrane is depolarized by addition of the K+ channel inhibitor quinine and it is hyperpolarized when the cells are suspended in Na+-free choline medium, indicating thatV m is generated partly by potassium and partly by sodium diffusion. Ehrlich cells have previously been shown to be more permeable to nitrate than to chloride. Substituting NO 3 for all cellular and extracellular Cl leads to a depolarization of the membrane, demonstrating thatV m is also generated by the anions and that anions are above equilibrium. Taking the previously demonstrated single-file behavior of the K+ channels into consideration, the membrane conductances in Ehrlich cells are estimated at 10.4 S/cm2 for K+, 3.0 S/cm2 for Na+, 0.6 S/cm2 for Cl and 8.7 S/cm2 for NO 3 . Addition of the Ca2+-ionophore A23187 results in net loss of KCl and a hyperpolarization of the membrane, indicating that the K+ permeability exceeds the Cl permeability also after the addition of A23187. The K+ and Cl conductances in A23187-treated Ehrlich cells are estimated at 134 and 30 S/cm2, respectively. The membrane potential is depolarized in hypotonically swollen cells, confirming that the increase in the Cl permeability following hypotonic exposure exceeds the concommitant increase in the K+ permeability. In control experiments where the membrane potentialV m =E K =E Cl =E Na , it is demonstrated that cell volume changes has no significant effect on the fluorescence signal, apparently because of a large intracellular buffering capacity. The increase in the Cl conductances is 68-fold when cells are transferred to a medium with half the osmolarity of the standard medium, as estimated from the net Cl efflux and the change inV m . The concommitant increase in the K+ conductance, as estimated from the net K+ efflux, is only twofold.  相似文献   

20.
Summary The volume regulatory response of the Ehrlich ascites tumor was studied in KCl-depleted, Na+-enriched cells. Subsequent incubation in K+-containing NaCl medium results in the reaccumulation of K+, Cl, water and the extrusion of Na+. The establishment of the physiological steady state is due primarily to the activity of 2 transport systems. One is the Na/K pump (K M for K 0 + =3.5mm;J max=30.1 mEq/kg dry min), which in these experiments was coupled 1K+/1 Na+. The second is the Cl-dependent (Na++K+) cotransport system (K M for K 0 + =6.8mm;J max=20.8 mEq/kg dry min) which mediates, in addition to net ion uptake in the ratio of 1K+1Na+2Cl, the exchange of K i + for K 0 + . The net passive driving force on the cotransport system is initially inwardly directed but does not decrease to zero at the steady state. This raises the possibility of the involvement of an additional source of energy. Although cell volume increases concomitant with net ion uptake, this change does not appear to be a major factor regulating the activity of the cotransport system.  相似文献   

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