共查询到20条相似文献,搜索用时 15 毫秒
1.
Net electrolyte efflux from suspension-cultured tobacco cells undergoing the hypersensitive reaction to Pseudomonas syringae pv. pisi resulted from a specific efflux of K + which was accompanied by an equimolar net influx of H +. These fluxes began 60 to 90 minutes after inoculation of tobacco cells with bacteria, reached maximum rates of 6 to 9 micromoles per gram fresh weight tobacco cells per hour within 2.5 to 3 hours, and dropped below 4 micromoles per gram per hour within 5 hours. Tobacco cells lost approximately 35% of total K + during this period, and average cellular pH declined by approximately 0.75 pH unit. These events were accompanied by a 30% decrease in cellular ATP. K + and H + fluxes were inhibited by the protonophore ( p-trifluoromethoxy)carbonyl cyanide phenylhydrazone and by increasing the K + concentration of the external solution. Tobacco leaf discs inoculated with the bacterium also exhibited a specific net K + efflux and H + influx. These results suggest that induction of the hypersensitive reaction in tobacco proceeds through the activation of a passive plasmalemma K +/H + exchange mechanism. It is hypothesized that activation of this exchange is a major contributing factor in hypersensitive plant cell death. 相似文献
2.
A purified pectate lyase isozyme derived from Erwinia chrysanthemi induced rapid net K + efflux and H + influx in suspension-cultured tobacco cells. Comparable fluxes of other ions (Na +, Cl −) were not observed. The K + efflux/H + influx response began within 15 minutes after addition of enzyme to cell suspensions and continued for approximately 1 hour after which cells resumed the net H + efflux exhibited prior to enzyme treatment. The response was not prolonged by a second enzyme dose 1 hour after the first. The K +/H + response was characterized by saturation at low enzymic activity (2 × 10 −3 units per milliliter), and inhibition by the protonophore, carbonyl cyanide m-chlorophenylhydrazone, and was not associated with membrane leakiness caused by structural cell wall damage. The total K + loss and H + uptake induced by enzyme was one-fourth to one-third that induced by Pseudomonas syringae pv. pisi and did not reduce cell viability. These results indicate that pectate lyase induces a K + efflux/H + influx response in tobacco similar to but of shorter duration than that induced by P. syringae pv. pisi during the hypersensitive response. Pectate lyase or other cell wall degrading enzymes may therefore influence the induction of hypersensitivity. 相似文献
3.
The adaptation to extreme concentrations of Ca 2+ and its consequence on the properties of the 45Ca 2+ transport were studied in submerged mycelia of Trichoderma viride. The adaptation to low [Ca 2+] o did not cause changes in kinetic parameters of the 45Ca 2+ influx but the adaptation to high [Ca 2+] o increased the KM(Ca2+). The Vmax of the 45Ca 2+ influx decreased with the age of (non-adapted) mycelia with concomitant decrease of the KM(Ca2+) these changes were prevented in mycelia adapted to high Ca 2+. High [Ca 2+] o decreased the stimulation by the uncoupler, 3, 3′, 4′, 5-tetrachloro salicylanilide (TCS) (30 μM), as compared to the control, whereas the Ca 2+ chelator, EGTA, stimulated it. In the aged mycelia, the stimulation by TCS of the 45Ca 2+ influx faded away, in parallel with the activity of the H +-ATPase. The 45Ca 2+ efflux from mycelia was affected by TCS in a similar way as the 45Ca 2+ influx. The results demonstrate the adaptive responses of transport processes participating in the mycelial Ca 2+ homeostasis and ageing are in agreement with a notion that both Ca 2+-influx and-efflux are coupled by the H +-homeostasis at the plasma membrane. 相似文献
4.
Washing corn ( Zea mays L.) root tissue in water causes loss of about one-third of the exchangeable Ca 2+ over the first 10 to 15 minutes. Upon transfer to K +-containing solutions, the tissue shows a short period of rapid K + influx which subsequently declines. Addition of 0.1 millimolar Ca 2+ decreases the initial rapid K + influx, but increases the sustained rate of K + and Cl − uptake. It was confirmed (Elzam and Hodges 1967 Plant Physiol 42: 1483-1488) that 0.1 millimolar Ca 2+ is more effective than higher concentrations for the initial inhibition, and that Mg 2+ will substitute. The inhibition arises from a mild shock affect of restoring Ca2+. With 0.1 millimolar Ca2+ net H+ efflux is blocked for 10 to 15 minutes and the cells are depolarized by about 30 millivolts. However, 1 millimolar Ca2+ rapidly produces increased K+ influx and blocks net H+ efflux for only a few minutes; blockage is preceded by a brief net H+ influx which may restore and increase ion transport by reactivating the plasmalemma H+-ATPase. Stimulation of electrogenic H+-pumping with fusicoccin eliminates the shock responses and minimizes Ca2+ effects on K+ influx. Fusicoccin also strongly decreases Ca2+ influx, but has no effect on Ca2+ efflux. Ice temperatures and high pH decreased Ca2+ efflux, but uncoupler and chlorpromazine did not. It is suggested that the inhibitory and promotive actions of Ca2+ are manifested through decreases or increases in the protonmotive force. 相似文献
5.
Stomatal movements depend on both ion influx and efflux; attainment of steady state apertures reflects modulation of either or both processes. The role of Ca 2+ in those two processes was investigated in isolated epidermal strips of Commelina communis, using the Ca 2+ chelator EGTA to reduce apoplastic [Ca 2+]. The results suggest that a certain concentration of Ca 2+ is an absolute requirement for salt efflux and stomatal closure. EGTA (2 millimolar) increased KCl-dependent stomatal opening in darkness and completely inhibited the dark-induced closure of initially open stomata. Closure was inhibited even in a KCl-free medium. Thus, maintenance of stomata in the open state does not necessarily depend on continued K + influx but on the inhibition of salt efflux. Opening in the dark was stimulated by IAA in a concentration-dependent manner, up to 15.4 micrometer without reaching saturation, while the response to EGTA leveled off at 9.2 micrometer. IAA did not inhibit stomatal closure to the extent it stimulated opening. The response to IAA is thus consistent with a primary stimulation of opening, while EGTA can be considered a specific inhibitor of stomatal closing since it inhibits closure to a much larger degree than it stimulates opening. CO 2 causes concentration-dependent reduction in the steady state stomatal aperture. EGTA completely reversed CO 2-induced closing of open stomata but only partially prevented the inhibition of opening. 相似文献
6.
The effects of monovalent cations, inhibitors of metabolism dinitrophenol (DNP), carbonyl cyanide- p-trifluoromethoxyphenylhydrazone (FCCP), and KCN and temperature variations upon Ca 2+ fluxes in intact roots of barley ( Hordeum vulgare L. cv. Fergus and Herta) seedlings were investigated. 45Ca 2+ influx was depressed in CaSO 4-grown (low-salt) plants by the presence of NH 4+, K +, or Na + in the uptake medium. In contrast Ca 2+ influx was slightly increased by Li +. In low-salt roots pretreated with KCN and in roots preloaded with K + (high-K + plants), the presence of K + in the medium had no significant effect on Ca 2+ influx, while in roots preloaded with Na +, the presence of K + in the medium depressed Ca 2+ influx. In absolute terms, Ca 2+ influx was significantly greater in high-salt (both K + or Na + preloaded) than in low-salt roots.Patterns of 45Ca 2+ efflux in the absence and in the presence of K +, NH 4+, or Li + in the external medium showed that these monovalent cations caused stimulation of 45Ca 2+ efflux both from the cytoplasmic and vacuolar phases.It was noted that these modifications of Ca 2+ fluxes by monovalent cations are transient and characteristic of a transitional stage of cation uptake by low-salt roots. We conclude that, together with stimulated active H + efflux (another characteristic of this transitional stage), modifications of Ca 2+ fluxes during monovalent cation uptake by low-salt roots is a response directed towards the maintenance of electrical neutrality.Determination of net fluxes revealed that the plants were close to Ca 2+ flux equilibrium in the growth medium (0.5 mM CaSO 4). Transfer of these plants to 0.5 mM CaSO 4 + 0.25 mM K 2SO 4 caused a net release of CA 2+ into the external medium. 相似文献
7.
The influence of ozone on Ca 2+ transport in plant membranes from pinto bean ( Phaseolus vulgaris L. var Pinto) leaves was investigated in vitro by means of a filtration method using purified vesicles. Two transport mechanisms located at the plasma membrane are involved in a response to ozone: (a) passive Ca 2+ influx into the cell and (b) active Ca 2+ efflux driven by an ATP-dependent system, which has two components: a primary Ca 2+ transport directly linked to ATP which is partially activated by calmodulin and a H +/Ca 2+ antiport coupled to activity of a H +-ATPase. The passive Ca 2+ permeability is increased by ozone. A triangular pulse of ozone stimulates a higher influx of Ca 2+ than does a square wave, even though the total dose was the same (0.6 microliter per liter × hour). Leaves exposed to a square wave did not exhibit visible injury and were still able to recover from oxidant stress by activation of calmodulin-dependent Ca 2+ extrusion mechanisms. On the other hand, leaves exposed to a triangular wave of ozone, exhibit visible injury and lost the ability of extruding Ca 2+ out of the cell. 相似文献
8.
Artificial pH gradients across tonoplast vesicles isolated from storage tissue of red beet ( Beta vulgaris L.) were used to study the kinetics of a Ca 2+/H + antiport across this membrane. Ca 2+-dependent H + fluxes were measured by the pH-dependent fluorescence quenching of acridine orange. ΔpH-dependent Ca 2+ influx was measured radiometrically. Both H + efflux and Ca 2+ influx displayed saturation kinetics and an identical dependence on external calcium with apparent Km values of 43.9 and 41.7 micromolar, respectively. Calcium influx was unaffected by an excess of Mg 2+ but was inhibited by La 3+ > Mn 2+ > Cd 2+. The apparent Km for external calcium was greatly affected (5-fold) by internal pH in the range of 6.0 to 6.5 and a transmembrane effect of internal proton binding on the affinity for external calcium is suggested. 相似文献
9.
The possible presence and properties of the Ca 2+-dependent K + channel have been investigated in the Ehrlich ascites tumor cell. The treatment with ionophore A23187+Ca 2+, propranolol or the electron donor system ascorbate-phenazine methosulphate, all of which activate that transport system in the human erythrocyte, produces in the Ehrlich cell a net loss of K + (balanced by the uptake of Na +) and a stimulation of both the influx and the efflux of 86Rb. These effects were antagonized by quinine, a known inhibitor of the Ca 2+-dependent K + channel in other cell systems, and by the addition of EGTA to the incubation medium. Ouabain did not have an inhibitory effect. These results suggests that the Ehrlich cell possesses a Ca 2+-dependent K + channel whose characteristics are similar to those described in other cell systems. 相似文献
10.
Fluctuating extracellular Ca 2+ regulates many aspects of neuronal (patho)physiology including cell metabolism and respiration. Using fluorescence-based intracellular oxygen sensing technique, we demonstrate that depletion of extracellular Ca 2+ from 1.8 to ≤ 0.6 mM by chelation with EGTA induces a marked spike in O 2 consumption in differentiated PC12 cells. This respiratory response is associated with the reduction in cytosolic and mitochondrial Ca 2+, minor depolarization on the mitochondrial membrane, moderate depolarization of plasma membrane, and no changes in NAD(P)H and ATP. The response is linked to the influx of extracellular Na + and the subsequent activation of mitochondrial Na +/Ca 2+ and Na +/H + exchange. The mitochondrial Na +/Ca 2+ exchanger ( mNCX) activated by Na + influx reduces Ca 2+ and increases Na + levels in the mitochondrial matrix. The excess of Na + activates the mitochondrial Na +/H + exchanger (NHE) increasing the outward pumping of protons, electron transport and O 2 consumption. Reduction in extracellular Na + and inhibition of Na + influx through the receptor operated calcium channels and plasmalemmal NHE reduce the respiratory response. Inhibition of the mNCX, L-type voltage gated Ca 2+ channels or the release of Ca 2+ from the endoplasmic reticulum also reduces the respiratory spike, indicating that unimpaired intercompartmental Ca 2+ exchange is critical for response development. 相似文献
11.
The uptake of K + and Ca 2+ in Dunaliella salina is mediated by two distinct carriers: a K + carrier with a high selectivity against Na +, Li +, and choline + but not towards Rb +, K +, Cs +, or NH 4+, and a Ca 2+ carrier with a high selectivity against Mg 2+. The latter is specifically blocked by La 3+ and by Cd 2+. Apparent Km values for K + and Ca 2+ uptake are 2.5 and 0.8 millimolar, respectively, and their maximal calculated fluxes are 22 and 0.8 nanomoles per square meter per second, respectively. Effects of permeable ions and ionophores on K + and Ca 2+ uptake suggest that the driving force for their uptake is the transmembrane electrical potential. Inhibitors of ATP production, typical inhibitors of plasma membrane H +-ATPases and protonionophores inhibit K + and Ca 2+ uptake and accelerate K + efflux. The results suggest that an H +-ATPase in the cell membrane provides the driving force for K + and Ca 2+ uptake. Efflux measurements from 86Rb + and 45Ca 2+ loaded cells suggest that part of the intracellular K + and most of the intracellular Ca 2+ is nonexchangeable with the extracellular pool. Correlations between phosphate and K + contents and the effect of phosphate on K + efflux suggest intracellular associations between K + and polyphosphates. On the basis of these results, it is suggested that: (a) K + and Ca 2+ uptake in D. salina is driven by the transmembrane electrical potential which is generated by the action of an H +-ATPase of the plasma membrane. (b) Part of the intracellular K + is associated with polyphosphate bodies, while most of the intracellular Ca 2+ is accumulated in intracellular organelles in the algal cells. 相似文献
12.
A pH-sensitive electrode was applied to measure activity of H + ions in the medium surrounding excitable cells of pumpkin ( Cucurbita pepo L.) seedlings during cooling-induced generation of action potential (AP). Reversible alkalization shifts were found to occur synchronously with AP, which could be due to the influx of H + ions from external medium into excitable cells. Ethacrynic acid (an anion channel blocker) reduced the AP amplitude but had no effect on the transient alkalization of the medium. An inhibitor of plasma membrane H +-ATPase, N,N’-dicyclohexylcarbodiimide suppressed both the AP amplitude and the extent of alkalization. In experiments with plasma membrane vesicles, the hydrolytic H +-ATPase activity was subjected to inhibition by Ca 2+ concentrations in the range characteristic of cytosolic changes during AP generation. The addition of a calcium channel blocker verapamil and a chelating agent EGTA to inhibit Ca 2+ influx from the medium eliminated the AP spike and diminished reversible alkalization of the external solution. An inhibitor of protein kinase, H-7 alleviated the inhibitory effect of Ca 2+ on hydrolytic H +-ATPase activity in plasma membrane vesicles and suppressed the reversible alkalization of the medium during AP generation. The results provide evidence that the depolarization phase of AP is associated not only with activation of chloride channels and Cl ? efflux but also with temporary suppression of plasma membrane H +-ATPase manifested as H + influx. The Ca 2+-induced inhibition of the plasma membrane H +-ATPase is supposedly mediated by protein kinases. 相似文献
13.
The importance of Ca 2+ signaling in astrocytes is undisputed but a potential role of Ca 2+ influx via L-channels in the brain in vivo is disputed, although expression of these channels in cultured astrocytes is recognized. This study shows that an increase in free cytosolic Ca 2+ concentration ([Ca 2+] i) in astrocytes in primary cultures in response to an increased extracellular K + concentration (45 mM) is inhibited not only by nifedipine (confirming previous observations) but also to a very large extent by ryanodine, inhibiting ryanodine receptor-mediated release of Ca 2+, known to occur in response to an elevation in [Ca 2+] i. This means that the actual influx of Ca 2+ is modest, which may contribute to the difficulty in demonstrating L-channel-mediated Ca 2+ currents in astrocytes in intact brain tissue. Chronic treatment with any of the 3 conventional anti-bipolar drugs lithium, carbamazepine or valproic acid similarly causes a pronounced inhibition of K +-mediated increase in [Ca 2+] i. This is shown to be due to an inhibition of capacitative Ca 2+ influx, reflected by decreased mRNA and protein expression of the ‘transient receptor potential channel’ (TRPC1), a constituent of store-operated channels (SOCEs). Literature data are cited (i) showing that depolarization-mediated Ca 2+ influx in response to an elevated extracellular K + concentration is important for generation of Ca 2+ oscillations and for the stimulatory effect of elevated K + concentrations in intact, non-cultured brain tissue, and (ii) that Ca 2+ channel activity is dependent upon availability of metabolic substrates, including glycogen. Finally, expression of mRNA for Ca v1.3 is demonstrated in freshly separated astrocytes from normal brain. 相似文献
14.
Relationships among several of the ion movements associated with the acrosome reaction of S. purpuratus were investigated. Egg jelly initiates 45Ca 2+ and 22Na + uptake, and K + and H + efflux. H + efflux and 22Na + uptake occur with approximately equivalent stoichiometries as rapidly as the appearance of acrosomal rods, perhaps reflecting a linked process. Most K + loss, as measured either by 42K + efflux or K +-ion-selective electrodes, occurs after the acrosome reaction is complete. Since an elevation of seawater K + (from 10 to 15 m M) or the addition of 0.5 m M tetraethylammonium (TEA), an inhibitor of K + channels, inhibits the acrosome reaction half-maximally, K + movements or alterations of K +-dependent membrane potentials may regulate the triggering by jelly. Most, but not all, of the 45Ca 2+ influx is inhibited with a mixture of 10 μ M FCCP, 1 m M CN ?, and 2 μg/ml oligomycin, suggesting that the mitochondria store most of the Ca 2+. The extracellular Na + concentration affects Ca 2+ fluxes: sperm placed into 5 m M Na + seawater have enhanced 45Ca 2+ uptake, but do not undergo the acrosome reaction, unless 30 m M Na + is also added. Low Na + concentrations lead to spontaneous triggering, by allowing for both Ca 2+ influx and Na +-dependent H + efflux. At least one early Ca 2+ requirement precedes the Na + and H + movements, as inferred from attempts at reversing the inhibitors of jelly induction of the acrosome reaction. When sperm are incubated with jelly in the absence of Ca 2+, then washed and incubated with jelly in the presence of Ca 2+, the acrosome reaction is triggered only upon the second incubation. However, when sperm are mixed with jelly in the presence of the other inhibitors (verapamil, TEA, 5 m M Na + seawater, low pH, or elevated K +), they are altered so that even upon subsequent washing, jelly-mediated triggering is no longer possible. This suggests the existence of an intermediate state in the reaction pathway, that follows an event for which Ca 2+ is required, but that precedes the Na + and H + movements, which are inhibited by all inhibitors of the acrosome reaction. These data are used to develop a partial sequence of ionic changes associated with the triggering mechanism. 相似文献
15.
High Na + concentrations may disrupt K + and Ca 2+ transport and interfere with growth of many plant species, cotton ( Gossypium hirsutum L.) included. Elevated Ca 2+ levels often counteract these consequences of salinity. The effect of supplemental Ca 2+ on influx of Ca 2+, K +, and Na + in roots of intact, salt-stressed cotton seedlings was therefore investigated. Eight-day-old seedlings were exposed to treatments ranging from 0 to 250 millimolar NaCl in the presence of nutrient solutions containing 0.4 or 10 millimolar Ca 2+. Sodium influx increased proportionally to increasing salinity. At high external Ca 2+, Na + influx was less than at low Ca 2+. Calcium influx was complex and exhibited two different responses to salinity. At low salt concentrations, influx decreased curvilinearly with increasing salt concentration. At 150 to 250 millimolar NaCl, 45Ca 2+ influx increased in proportion to salt concentrations, especially with high Ca 2+. Potassium influx declined significantly with increasing salinity, but was unaffected by external Ca 2+. The rate of K + uptake was dependent upon root weight, although influx was normalized for root weight. We conclude that the protection of root growth from salt stress by supplemental Ca 2+ is related to improved Ca-status and maintenance of K +/Na + selectivity. 相似文献
16.
In the budding yeast Saccharomyces cerevisiae, mating pheromones activate a high-affinity Ca 2+ influx system (HACS) that activates calcineurin and is essential for cell survival. Here we identify extracellular K + and a homologous pair of transmembrane proteins, Kch1 and Kch2 (Prm6), as necessary components of the HACS activation mechanism. Expression of Kch1 and especially Kch2 was strongly induced during the response to mating pheromones. When forcibly overexpressed, Kch1 and Kch2 localized to the plasma membrane and activated HACS in a fashion that depended on extracellular K + but not pheromones. They also promoted growth of trk1 trk2 mutant cells in low K + environments, suggesting they promote K + uptake. Voltage-clamp recordings of protoplasts revealed diminished inward K + currents in kch1 kch2 double-mutant cells relative to the wild type. Conversely, heterologous expression of Kch1 in HEK293T cells caused the appearance of inwardly rectifying K + currents. Collectively, these findings suggest that Kch1 and Kch2 directly promote K + influx and that HACS may electrochemically respond to K + influx in much the same way as the homologous voltage-gated Ca 2+ channels in most animal cell types. 相似文献
17.
Activation of a host plasma membrane K + efflux/net H + uptake exchange by pathogenic pseudomonads plays an important role in the development of hypersensitivity in tobacco ( Nicotiana tabacum). Involvement of the plasmalemma H +-pumping ATPase in this response was investigated. The exchange response of suspension-cultured tobacco cells to Pseudomonas syringae pv syringae was reduced 90% or more by ATPase inhibitors including vanadate, N-ethylmaleimide, and N,N′-dicyclohexylcarbodiimide. The exchange was also strongly inhibited by the protonophore carbonyl cyanide m-chlorophenylhydrazone and by slightly alkaline external pH. Respiratory inhibitors such as oligomycin and sodium azide reduced the exchange by 50% to 75%, while glycolysis inhibitors such as sodium arsenite and sodium iodoacetate decreased exchange by approximately 90%. These results suggest that plasmalemma H +-ATPase activity is required for the exchange response and that this may reflect a requirement for a plasmalemma pH and/or electrical potential gradient. 相似文献
18.
Net fluxes of Ca 2+, H + and K + were measured from intact Chara australis cells and from isolated cell walls, using ion-selective microelectrodes. In both systems, a stimulation in Ca 2+ efflux (up to 100 nmol m ?2 s ?1, from an influx of ~40 nmol m ?2 s ?1) was detected as the H + or K + concentration was progressively increased in the bathing solution (pH 7.0 to 4.6 or K + 0.2 to 10mol m ?3, respectively). A Ca 2+ influx of similar size occurred following the reverse changes. These fluxes decayed exponentially with a time constant of about 10 min. The threshold pH for Ca 2+ efflux (pH 5.2) is similar to a reported pH threshold for acid-induced wall extensibility in a closely related characean species. Application of NH 4+ to intact cells caused prolonged H + efflux and also transient Ca 2+ efflux. We attribute all these net Ca 2+ fluxes to exchange in the wall with H + or K +. A theoretical treatment of the cell wall ion exchanges, using the ‘weak acid Donnan Manning’ (WADM) model, is given and it agrees well with the data. The role of Ca 2+ in the cell wall and the effect of Ca 2+ exchanges on the measured fluxes of other ions, including bathing medium acidification by H + efflux, are discussed. 相似文献
19.
Ca 2+ (0.1-1.0 millimolar) accelerated dark-induced stomatal closure and reduced stomatal apertures in the light in epidermal peels of Commelina communis L. In contrast, ethyleneglycol-bis-(β-aminoethyl ether) N,N′tetraacetic acid (EGTA) (2 millimolar), a Ca 2+ chelator, prevented closure in the dark and accelerated opening in the light. EGTA did not promote significant opening in the dark. It is therefore concluded that EGTA does not increase ion uptake into guard cells, but rather prevents ion efflux. Addition of EGTA to incubating solutions with 10 millimolar KCl resulted in steady state apertures of 15.6 micrometers, whereas in the absence of EGTA similar apertures required 55 millimolar KCl and 150 millimolar KCl was needed in the presence of 1 millimolar CaCl 2. The results demonstrate the importance of Ca 2+ in the regulation of stomatal closure and point to a role of Ca 2+ in the regulation of K + efflux from stomatal guard cells. 相似文献
20.
Ionic mechanisms of salt stress perception were investigated by non‐invasive measurements of net H +, K +, Ca 2+, Na +, and Cl ? fluxes from leaf mesophyll of broad bean ( Vicia faba L.) plants using vibrating ion‐selective microelectrodes (the MIFE technique). Treatment with 90 m M NaCl led to a significant increase in the net K + efflux and enhanced activity of the plasma membrane H +‐pump. Both these events were effectively prevented by high (10 m M ) Ca 2+ concentrations in the bath. At the same time, no significant difference in the net Na + flux has been found between low‐ and high‐calcium treatments. It is likely that plasma membrane K + and H + transporters, but not the VIC channels, play the key role in the amelioration of negative salt effects by Ca 2+ in the bean mesophyll. Experiments with isotonic mannitol application showed that cell ionic responses to hyperosmotic treatment are highly stress‐specific. The most striking difference in response was shown by K + fluxes, which varied from an increased net K + efflux (NaCl treatment) to a net K + influx (mannitol treatment). It is concluded that different ionic mechanisms are involved in the perception of the ‘ionic’ and ‘osmotic’ components of salt stress. 相似文献
|