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1.
The Ionic Relations of Acetabularia mediterranea 总被引:3,自引:0,他引:3
The concentrations of K+, Na+, and Cl in the cytoplasmand the vacuole of Acetabularia mediterranea have been measured,as have the vacuolar concentrations of SO4 andoxalate. The electrical potential difference between externalsolution, and vacuole and cytoplasm has been measured. The resultsindicate that Cl and SO4 are probably transportedactively into the cell, and that active transport of Na+ isoutwards. The results for K+ are equivocal. The fluxes of K+,Na+, Cl, and S04 into the cell and theeffluxes of Na+ and Cl have been determined. The Clfluxes are extremely large. In all cases the plasmalemma isthe rate-limiting membrane for ion movement. A technique isdescribed for the preparation of large, completely viable cellfragments containing only cytoplasm, with no vacuole. 相似文献
2.
Cells of Dunaliella parva, a green halotolerant alga, were equilibratedin 0.5 M NaCl (the same concentration as in the growth medium).The time course of changes in K+, Na+, Cl, andpellet volume were followed after a hypertonic shock causedby increasing the outside NaCl concentration to 1 M. The cellsresponded initially by shrinking; they returned to their originalvolume in the course of the next 23 h. At the time ofthe hypertonic shock there were rapid influxes of Na+ and Clwhich took about 30 min for completion. Thereafter, there wereprogressive losses of Na+ and Cl; these losses were temperature-dependentand presumably activated by metabolic energy. Cell K+ remainedconstant throughout. 相似文献
3.
Measurements of K+, Na+, and Cl were made on a halotolerantstrain of Dunaliella growing at 500 mM NaCl, 25 ?C, and a relativelylow light intensity (6000 Lx). Much effort was spent in searchingfor a means of measuring the extracellular volume of fluid trappedbetween the cells of centrifuged pellets. All of the sugarstried as markers were rejected because they were found to bedigested in the cell suspension. The most suitable marker wasfound to be [14C]polyethylene glycol2 (mol. wt. 4000); althoughthis substance was apparently adsorbed to the cell exterior,it was found possible to correct for adsorption and then obtaina reasonable figure for the trapped fluid. The final concentrationsof cell K+ and Na+ were 128 ? 53 mM and 131 ? 117 mM respectively.Cl balanced the sum of K+ Na+. Influxes of 22Na+, 42K+,and 36C1 were measured in cells in which the ions werein the steady state. Averages of 610 and 6.6 nmol m2s1 were obtained for Na+ and K+ respectively. Clinflux was divided into 2 phases with values of 1540 and 178mmol m2 s1. The faster influx was considered tobe across the outer cell membrane. The membrane responsiblefor the slower influx has not been identified. By comparingvalues of the potential difference calculated from the Nernstand Goldman equations, it was concluded that Na+ and K+ areprobably controlled by active mechanisms, whereas cell Clis likely to be at thermodynamic equilibrium with the medium. 相似文献
4.
Munns, R. 1985. Na+, K+ and Cl in xylem sap flowing toshoots of NaCl-treated barley.J. exp. Bot. 36: 10321042. Na+, Cl and K+ concentrations were measured in xylemsap obtained by applying pressure to the roots of decapitatedbarley plants grown at external [NaCl] of 0, 25, 50, 100, 150and 200 mol m3. For any given NaCl treatment, ion concentrationsin the xylem sap were hyperbolically related to the flux ofwater. Ion concentrations in sap collected at very low volumefluxes (without applied pressure) were 510 times higherthan in sap collected at moderate fluxes (under pressure). Fora given moderate volume flux, Na+ concentration in the xylemsap, [Na+]x, was only 4.0 mol m3 at external [NaCl] of25150 mol m3, and increased to 7.0 mol m3at 200 mol m3. [Cl-]x showed a similar pattern. Thisshows there would be little difference in the rate of uptaketo the shoot of plants at 25150 mol m3 externalNaCl and indicates little change even at 200 mol m-3 NaCl becausetranspiration rates would be much lower. Thus the reduced growthof the shoot of plants at high NaCl concentrations is not dueto higher uptake rates of Na+ or Cl. The fluxes of Na+, Cl and K increased non-linearlywith increasing volume flux indicating little movement of saltin the apoplast. The flux of K+ increased even when [K+]x wasgreater than external [K+], indicating that membrane transportprocesses modify the K+ concentration in the transpiration streamas it flows through the root system. Key words: -Xylem sap, Na+, K+, Cl fluxes, salinity, barley 相似文献
5.
ANDERSON W. P; WILLCOCKS D. A.; WRIGHT BARBARA J. 《Journal of experimental botany》1977,28(4):894-901
The ion contents and membrane potentials of the cells of young,hydroponically cultured seedlings of Atriplex hastata L. var.salina, Wallr. have been measured at several different NaClconcentrations. The total tissue concentrations of Na+ and Clincrease as external NaCl increases, but there is always a markedexcess of internal Na+ over Cl; this is balanced by endogenousorganic anion formation with a concomitant extrusion of H+ tothe bathing solution. Membrane potentials of the root cells remain essentially invariantwith changes in external NaCl at approx. 130 mV; thereis no evidence of a radial gradient of potential across theroot. The potential seems to contain a cyanide-sensitive electrogeniccomponent, also invariant with NaCl concentration, of about70 mV, and a diffusion component. The electrogenic componentseems likely to be a H+ efflux, probably through a H+ uniportATPase. 相似文献
6.
Biophysical and Biochemical Regulation of Cytoplasmic pH in Chara corallina during Acid Loads 总被引:1,自引:0,他引:1
The contribution of membrane transport to regulation of cytoplasmicpH in Chara corallina has been measured during proton-loadingby uptake of butyric acid. In the short-term (i.e. up to 20min) uptake of butyric acid is not affected by removal of externalK+, Na+ or Cl but over longer periods uptake is decreased(by 2050% in different experiments) in the absence ofexternal Na+ or, sometimes, K+. Influxes of both Na+ and K+increase temporarily after addition of butyrate, Na+ immediatelyand K+ after a lag. Effects on Cl influx are small butCl efflux increases enormously after a short lag. Anapproximate comparison of internal butyrate with changes inthe concentration of K+, Na+, and Cl suggests that initially(i.e. for a few min) cytoplasmic pH is determined by bufferingand possibly by some decarboxylation of organic acids (biochemicalpH regulation), and that biophysical pH regulation involvingefflux of H+ balanced by influxes of K+, Na+ and especiallyefflux of Cl progressively becomes dominant. When butyric acid is washed out of the cells, cytoplasmic pHis restored completely or partially (depending on the butyrateconcentration used) and this is independent of the presenceor absence of external Cl. Where Cl is present,its influx is relatively small. It is suggested that cytoplasmicpH is then controlled biochemically, involving the synthesisof an (unidentified) organic acid and the accumulation of acidicanions in place of butyurate lost from the cell. During thesecond application of butyrate, net Cl efflux is small:it is suggested that control of cytoplasmic pH then involvesdecarboxylation of the organic acid anions. The questions of the source of Cl lost from the cell(cytoplasm or vacuole) and of possible cytoplasmic swellingassociated with the accumulation of butyrate are discussed. Key words: Chara corallina, butyric acid, cytoplasmic pH, membrane transport 相似文献
7.
Effects of Ions and Membrane Potential on the Elongation of the Unicellular Green Alga Closterium 总被引:1,自引:0,他引:1
Cells of the unicellular green alga Closterium ehrenbergii elongatedexclusively at septa and for 45 hours after cell division.Cell elongation was strongly inhibited by a decrease in eitherthe external concentration of Ca2+ or pH, and was also inhibitedby several competitive Ca2+ channel blockers. Changes in concentrationsof other external ions had no effect on the elongation. Theaverage concentrations of ions in the intracellular fluid ofthe interphase cell before cell division was as follows (inmM): K+=56.5, Na+=4.8, Ca2+=2.4, Mg2+=1.3, Cl=59.5; thepH was 7.4. The levels of K+, Na+ and Cl ions decreasedsignificantly with cell elongation, suggesting that this process,which proceeds with water uptake, surpasses ion absorption.The plasma membrane potential (Vm) in both the interphase cellsand in the elongating cells was in the range of 90 to105 mV (interior negative). The Vm was entirely determinedby the simple diffusion of K+. A decrease in the external concentrationof Ca2+ caused depolarization, probably by an indirect effectof low Ca2+. Changes in the extracellular level of H+ and othercations barely affected Vm. Thus, external Ca2+ and H+ are concludedto affect cell elongation but not via a change in the Vm acrossthe plasma membrane. (Received February 29, 1988; Accepted June 8, 1988) 相似文献
8.
An Examination, by Compartmental Flux Analysis, of the Development of Sodium and Chloride Absorption Capacities in Beetroot Disks 总被引:1,自引:0,他引:1
Using beetroot, Beta vulgaris L. var. Avon Early, grown in radioactivelylabelled nutrient solutions, concentrations and fluxes of Na+and Cl were estimated for cells of freshly cut storageroot disks, by compartmental analysis of radioisotope elutionmeasurements. These values were compared with results obtainedin a similar manner from beetroot grown in non-labelled nutrientsolution and loaded instead during an aging period in 22Na-or 36Cl- labelled 1 mM NaCl solution. In accord with the generallyaccepted, but never properly tested, view, it was found thatnet Na+ influx followed from a reduction in efflux with agingand net Cl uptake depended on a marked increase in influx.However, both these important changes took place at the tonoplast,and, although aging led to a reduction of plasmalemma fluxes,at no time was entry of Cl into the cytoplasm, or lossof Na+ from the cytoplasm, significantly restricted. 相似文献
9.
The marine hyphomycete Dendryphiella salina (Suth.) Nicot &Pugh has a resting membrane potential of 250 mV (insidenegative). The respiratory inhibitors sodium azide and FCCPinduced a rapid but reversible depolarization of the membraneof at least 180 mV; sodium azide also caused alkalinizationof the medium. Vanadate brought about significant depolarizationbut this was not always reversible. EDTA induced depolarizationthough to a lesser extent. DIDS and SITS caused a depolarizationof around 3070 mV which was readily reversible, N-ethylmaleimideirreversibly depolarized the membrane by 180200 mV. Ouabainhad no effect. When external concentrations of H+ , K+ , Na+or Cl were changed singly, only changes in H+ affectedmembrane potential, with shifts decreasing with increasing pH.Glucose and 3-O-methyl glucose depolarized the membrane in aconcentration-dependent manner which was enhanced by starvationof the hyphae. Recovery occurred in the presence of the hexose.Glucose caused an alkalinization of the medium, with time characteristicssimilar to the membrane potential changes. It is concluded thatthere is an electrogenic proton pump and a protonglucosesymporter in D. salina. The retention of proton-based transportsystems suggests a terrestrial origin for the fungus. Key words: Marine fungi, Dendryphiella salina, membrane potential, electrogenic proton pump, proton symport, hexose 相似文献
10.
Osmotic and Ionic Regulation in Chara L-cell Fragments 总被引:1,自引:0,他引:1
Ion absorption from rather complicated artificial pond water(APW) by cell fragments having a lower osmotic pressure thanthe intact internodal cell (L-cell fragments) was studied. L-cellfragments were prepared by taking advantage of trans cellularosmosis and ligating the cell with thread. The results wereas follows: (1) L-cell fragments absorbed more K+ than Na+ fromaKCL + NaCl mixture in the presence of Ca2+, Mg2+ and SO24 inthe light; (2) the influx of KCI was larger than that of KNO3;(3) the amount of positive charge carried by K+, Na+ and Mg2+across the cell membrane balanced well with the amount of negativecharge carried by Cl in Cl-containing and NO3-free APW; (4) no conclusion could be made as to whether ornot the rule of electro neutrality held for the K+, Na+, Ca2+and NO3 fluxes across the cell membrane, because dilutedKNO3 is unstable; (5) L-cell fragments in KCl-containing APWsurvived longer than those in KNO3-containing and Cl-free APW; (6) after incubation in KNO3-containing and Cl-freeAPW, L-cell fragments absorbed a great amount of KCI immediatelyafter being transferred to KCl-containing and NO3 -freeAPW; and (7) lowering the turgor pressure of the intact cellby raising the external osmotic pressure did not induce ionflux into the cell. Thus, we concluded that the L-cell fragmentsabsorbed ions from the external solution not because of theirlower turgor pressure, but because of the diluted ion concentrationof the cytoplasm and the vacuole. The electroneutrality ruleheld, at least, for K+, Na+, Mg2+ and Cl influxes acrossthe cell membrane inthe KCl-containing and NO3-free APW.These results were analyzed on the basis of an extended poremodel which presumed the existence of ATP-dependent processesin the membrane, and suggested that K+, Na+ and Mg2+ inflowsinto an L-cell fragment are likely to be induced by active Clinflow. (Received May 18, 1987; Accepted September 29, 1987) 相似文献
11.
Reduced Permeability to K+ and Na+ Ions of K+ Channels in the Plasma Membrane of Tobacco Cells in Suspension after Adaptation to 50 mM NaCl 总被引:1,自引:0,他引:1
Murata Yoshiyuki; Obi Ichiro; Yoshihashi Manabu; Noguchi Masakatsu; Kakutani Tadaaki 《Plant & cell physiology》1994,35(1):87-92
The whole-cell patch-clamp technique was used to study and comparethe characteristics of K+-and Na+-transport processes acrossthe plasma membrane in two types of protoplast isolated fromNaCl-adapted and -unadapted cells of tobacco (Nicotiana tabacumL. cv. Bright Yellow-2) in suspension culture. In both typesof protoplast, with 100 mM KCl in the bathing solution and inthe pipette solution, depolarization of the plasma membranefrom the holding potential of 0 mV to a positive potential resultedin a relatively large outward current which increased with increasingpositive potential, whereas hyperpolarization to negative potentialsup to 100 mV resulted in only a small inward current.The outward current activated by depolarization was predominantlycarried by K+ ions through K+ channels. Na+ ions also had afinite ability to pass through these K+ channels. The outwardK+ and Na+ currents of the NaCl-adapted cells were considerablysmaller than those of the NaCl-unadapted cells. These resultssuggest that adaptation to salinity results in reduced permeabilityof the plasma membrane to both K+ and Na+ ions.
1Present address: Research Laboratory of Applied Biochemistry,Tanabe Seiyaku Co., Ltd., 16-89, Kashima 3-chome, Yodogawa-ku,Osaka, 532 Japan 相似文献
12.
Potassium Transport in Enteromorpha intestinalis (L.) Link: II. EFFECTS OF MEDIUM COMPOSITION AND METABOLIC INHIBITORS 总被引:2,自引:0,他引:2
In springwater (25.5 mol m3 Cl, 20.4 mol m3Na+, 0.14 mol m3 K+) Enteromorpha intestinalis couldnot survive for more than a few weeks unless provided with 0.5mol m3 K+ in the medium or alternatively exposed to seawaterfor 1 day per week. Maintenance of a cytoplasmic K+ level ofabout 200 mol m3 is critical for the maintenance of normalmetabolic activity. Net gains of intracellular K+ occurred whenthe plants were transferred from low-salinity to seawater; converselylarge net losses occurred when plants were transferred fromseawater to springwater. These two processes were not simplythe reverse of one another; net gain of K+ involved a largeincrease in the tracer flux both into and out of the cell butnet loss of K+ virtually halted the tracer flux into the cell.Any injury incurred by rapid salinity changes was short-lived;plants were rapidly able to adjust intracellular [K1.K+). K+(orto some extent Rb+) was found to be necessary in the effluxmedium for 42K+ exchange to occur. The osmotic concentrationof the medium was also important but extracellular Na+ and Clconcentrationswere not critical. K+ influx and efflux in both springwaterand seawater were largely independent of light and were sensitivein varying degrees to a range of common metabolic inhibitorsand uncouplers. The results are best explained by the presenceof an active K+ influx, generated by an ATP-dependent K+ pumpat the plasmalemma. Key words: Enteromorpha, Potassium transport, Salinity changes, Uncouplers, Inhibitors 相似文献
13.
Ionic Activity Gradients across the Surface Membrane of Cytoplasmic Droplets Prepared from Chara australis 总被引:1,自引:0,他引:1
The membrane potential and the ionic activity gradients of K+and Cl across the surface membrane of cytoplasmic dropletsprepared from Chara australis internodal cells, were measuredin high and low ionic strength bathing solutions using liquidion exchange microelectrodes selective for K+ and Cl.Our results indicate that K+ is close to electrochemical equilibriumwhereas Cl is not.
1 Present address: ICI Japan, Palace Hotel Annex Building, Marunouchi,Tokyo, Japan. 相似文献
14.
Plants of Lupinus albus L., cv. Ultra, were grown hydroponicallywith NO3-nutrition for 51 d under control (0.05 mol m3Na+ and 10 mol m3 Cl) and saline (40 mol m3NaCI) conditions. Plants were harvested 41 and 51 d after germinationand analysed for content and net increment of C, N and the mineralcations K+, Na+, Mg2+, and Ca2+ and the anions Cl, NOJ,malate, phosphate, and SO42. Roots, stem interaodes,petioles and leaflets were analysed separately. During the studyperiod net photosynthesis, respiratory losses of CO2 from shootand root and the composition of the spontaneously bleeding phloemsap and the root pressure xylem exudate were also determined.Using molar ratios of C over N in the transport fluids, incrementsof C and N, and photosynthetic gains as well as respiratorylosses of C, the net flows of C and N in the xylem and phloemwere then calculated as in earlier studies (Pate, Layzell andMcNeill, 1979a). Knowing the carbon flows, the ratios of ionto carbon in the phloem sap, and ion increments in individualorgans, net flows of K+, Na+, and Cl over the study periodwere also calculated. Salt stress led to a general decrease of all partial componentsof C and N partitioning indicating that inhibitions were notdue to specific effects of NaCI salinity on photosynthesis oron NO3 uptake. However, there were differences between variouslyaged organs, and net phloem export of nitrogenous compoundsfrom ageing leaves was substantially enhanced under saline conditions.In addition, NO3reduction in the roots was specificallyinhibited. Uptake and xylem transport of K+ was more severelyinhibited than photosynthetic carbon gain or NO3 uptakeby the root. K+ transport in the phloem was even more severelyrestricted under saline conditions. Na+ and Cl flowsand uptake, on the other hand, were substantially increasedin the presence of salt and, in particular, there were thenmassive flows of Na in the phloem. The results are discussedin relation to the causes of salt sensitivity of Lupinus albus.The data suggest that both a restriction of K+ supply and astrongly increased phloem translocation of Na+ contribute tothe adverse effects of salt in this species. Restriction ofK+ supply occurs by diminished K+ uptake and even more by reducedK+ cycling within the plant. Key words: Lupinus albus, salt stress, phloem transport, xylem transport, partitioning, carbon, nitrogen, K+, Na+, CI 相似文献
15.
Interaction of Salinity and Anaerobiosis in Barley and Rice 总被引:3,自引:0,他引:3
Barley and rice at the early tillering stage were exposed simultaneouslyto anaerobiosis and high [NaCl]. Barley was grown at 0.5, 70,and 125 mol m3 NaCl, and rice at 2, 20, 40, and 80 molm3 NaCl. Surprisingly, anaerobiosis only slightly aggravatedthe adverse effects of high [NaCl] on root and shoot growthof both species. For rice and barley grown under aerobic conditions, high [NaCl]increased [Na+] and [Cl] and decreased [K+] in both rootsand shoots. However, the changes in ion concentrations in theshoots were smaller for rice than for barley. For roots of barley, anaerobiosis decreased [Na+], [Cl],and [K+] at both low and high [NaCl], possibly as a result ofinhibition of active ion accumulation. For barley shoots, anaerobiosisincreased [Na+] and [Cl], but only at high salinity;in contrast, [K+] was reduced by anaerobiosis at both low andhigh [NaCl]. These results indicate that anaerobiosis slightlyincreased the permeability of the barley root system to Na+and Cl. For rice, the most important interaction between salinity andanaerobiosis occurred in the shoots, where anaerobiosis increased[Na+] and decreased [K+], particularly at 40 and 80 mol m3NaCl, while there was no interaction between anaerobiosis andsalinity for Cl uptake. It is therefore suggested thatanaerobic treatment of rice decreased the selectivity for K+over Na+ of cation transport to the shoots, at least for plantsgrown at high salinities. 相似文献
16.
Lamprothamnium, a Euryhaline Charophyte: IV. MEMBRANE POTENTIAL, IONIC FLUXES AND METABOLIC ACTIVITY DURING TURGOR ADJUSTMENT 总被引:3,自引:0,他引:3
The early time-course of turgor adjustment following a hyper-or hypo-osomotic shock was examined in the brackish-water charophyteLamprothamnium papulosum. The response to a reduction in turgorwas a five to seven-fold stimulation of the influxes of Cl,K+ and Na+. The distribution of radioactive tracers in the cellsuggested that the ionic composition of the cytoplasm was strictlycontrolled during turgor adjustment. Metabolic activity wasrelatively unaffected by the loss of turgor. high fluxes throughthe cytoplasm, and a cytoplasmic K concentration possiblyas high as 280 mol m3. Osmotic adjustment to a lower salinity was achieved by largeincreases in the passive effluxes of K+ and Cl ratherthan by decreases in their influxes. The membrane remained hyperpolarized during hyperosmotic adjustmentbut depolarized after a hypo-osmotic change. This result isdiscussed in relation to changes in the driving forces for ionmovements during osmotic transitions. Key words: Lamprothamnium, Turgor, Osmotic stress 相似文献
17.
A Cl channel and two types of K+ channel have been observed,by the use of the patch-clamp technique, in the membrane surroundingcytoplasmic droplets from Chara corallina. Measurements on cell-attachedpatches showed that the channel selective for Cl hada chord conductance of 21 pS at the resting membrane p.d. (mean= 11 mV, n = 19) and when open, passed an outward current of1.4 pA (n = 24 patches) at the resting p.d., with reversal ofthe direction of current at 54 mV (130 mol m3Cl in the external solution). The Cl concentrationin the cytoplasmic droplet calculated from the reversal p.d.was 15 mol m3. The channel strongly rectified outwardcurrent flow, but this rectification disappeared with symmetricalCl concentrations across detached patches of membrane.It is concluded that rectification observed in cell-attachedpatches is primarily due to asymmetric Cl concentrationsrather than an asymmetry in energy barriers to Cl permeationin the channel or any voltage-dependent kinetics of the channel.The channel was rarely observed in detached patches despitebeing commonly observed in cell-attached patches. However, theabsence of Ca2+ at the cytoplasmic face of the membrane allowedobservation of the channel in detached patches for brief periods,during which ion substitution experiments revealed a permeabilitysequence of aspartate (76:33:1). A 100 pS K+ channel previously described by Luhring (1986) wasfrequently observed, in some instances simultaneously, witha channel having a conductance of 60 pS and displaying outwardrectification. This rectification was due to the channel remainingopen almost continuously for positive membrane potential differences(p.d.) and remaining shut almost continuously for negative p.d.'s.The 60 pS channel, like the 100 pS K+ channel, reversed currentflow at the resting p.d., suggesting that it was also permeableto K+. Key words: Plant ion-channels, chloride channel, potassium channel, patch-clamp 相似文献
18.
Oka Kotaro; Naitou Shigehiro; Yoshida Motoko; Ishikawa Hideo; Ohta Eiji; Sakata Makoto 《Plant & cell physiology》1987,28(5):843-849
Membrane potentials of protoplasts isolated from Vigna mungohypocotyl segments were measured using the fluorescent probediS-C3-(5). The fluorescence intensity changed in response tothe external K+ concentration. Membrane potential was estimatedto be inside negative (85?8 mV at 0.1 mM KCl) from theNernst equation for K+. The membrane potential was not affectedby DCCD (50 µM) or low temperature (5?C). Addition of0.5 mM Ca2+ to the protoplast suspension markedly depolarizedthe membrane potential, and subsequent EDTA treatment repolarizedit to the initial level. The Ca2+ effect on the membrane potentialmay be due to change in the permeability ratio of Clto K+. (Received December 16, 1986; Accepted April 22, 1987) 相似文献
19.
The intercellular distribution of vacuolar solutes in the epidermis and mesophyll of barley leaves changes in response to NaCl 总被引:8,自引:3,他引:5
Concentrations of inorganic and organic solutes were measuredin sap extracted from individual mesophyll and epidermal cellsof the third leaf of barley. During the development of the thirdleaf plants were grown in various salt solutions (NaCl; 2, 50,100, and 150 mM, KCI; 100 mM or KNO3; 100 mM). Leaves were analysed24 d after full expansion. Cell-sap was extracted usinga modified pressure probe and analysed for its osmolality, concentrationsof P, Na+ K+ Ca2+, and Cl and, in some cases, of nitrate,hexoses and total amino acids. Salt treatment caused differentialchanges in the concentrations of solutes in mesophyll and epidermalcells, but did not affect the basic pattern of solute compartmentationbetween these tissues. Calcium was found at osmotically significantconcentrations only in the epidermis, whereas P and organicsolutes were almost exclusively found in the mesophyll. Chlorideand Na+ accumulated preferentially in the epidermis, althoughmesophyll concentrations also increased considerably. At 150mM external NaCl, mesophyll cells contained 302 mM Na and 167mM Cl, compared to 29 mM Na+ and 16 mM Cl in thecontrol. Mesophyll Cl levels were even higher in the100 mM KCl treatment (216 mM) where mesophyll and epidermalK+ accumulated to 424 and 491 mM, respectively. These huge increasesin mesophyll Na+ Cl and K+ were not associated with abreakdown in leaf performance since net rates of photosynthesisdecreased only by less than 20%. Under control (2 mM NaCl) conditions,solutes followed patterned gradients between the various epidermalcell types. The extent of these gradients changed with leafage. During 50 mM NaCl treatment, gradients in Cl, nitrateand malate concentrations progressively disappeared, with malateconcentrations approaching zero. Potassium and Na+ exhibitedaltered distribution profiles, whereas Ca2+ distribution wasunaffected. NaCl-dependent increases in osmolalities differedbetween cells. Exposure of plants to 150 mM NaCl caused qualitativelysimilar changes in both epidermal solute and osmolality profiles,although absolute values differed from those at 50 mM NaCl.In particular, epidermal Cl and Na+ increased to about500 mM and K+ disappeared (<<5 mM) from the vacuole ofcertain epidermal cell types completely. Key words: Barley leaf epidermis, mesophyll, salt stress, single-cell analysis, vacuolar solutes 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