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1.
P. Guicherd J. P. Peltier E. Gout R. Bligny G. Marigo 《Trees - Structure and Function》1997,11(3):155-161
In leaves of Fraxinus excelsior L., malate and mannitol were characterized by 13C NMR spectroscopy and enzymatic specific assays as the major constituents of a soluble carbon fraction involved in an osmotic
adjustment. During a summer drought where predawn leaf water potential of adult trees growing in a mesoxerophilic stand fell
to – 4 MPa in August, malate and mannitol leaf contents increased by a factor of 1.8 and 2.2 respectively, compared to control
trees growing on a flood plain. This drought stress led to concentrations as high as 280 mM and 600 mM for mannitol and malate,
respectively. The effects of gradually developing water deficit were also studied in a semi-controlled environment in 3-year-old
seedlings. When predawn leaf water potential reached -6 MPa, leaves displayed a low turgor pressure but stomatal conductance
was still measurable. Malate and mannitol were also the main osmoticum involved. After rewatering, gas exchange capacities
were largely restored. Altogether, these results show that the strong water-stress tolerance of Fraxinus excelsior is in part related to an accumulation of malate and mannitol.
Received: 3 January 1996 / Accepted: 19 March 1996 相似文献
2.
To elucidate the osmotic adjustment characteristics of mangrove plants, inorganic ion and organic solute contents of intermediate
leaves were investigated in 3-month-old Kandelia candel (L.) Druce seedlings during 45 days of NaCl treatments (0, 200, and 500 mM NaCl). The contents of Na+, Cl−, total free amino acids, proline, total soluble sugars, pinitol and mannitol increased to different degree by salinity, whereas,
K+ content decreased by salinity compared with control. NaCl treatment induced an increase of inorganic ion contribution while
a decrease of organic solute contribution. It was concluded that accumulating a large amount of inorganic ions was used as
the main osmotic adjustment mechanism under salinity treatment. However, accumulation of organic osmolytes might be considered
to play much more important role in osmoregulation under severe salinity (500 mM NaCl) than under moderate salinity (200 mM
NaCl), thus the damage caused by high toxic ions (Na+ and Cl−) concentration in K. candel leaves could be avoided. 相似文献
3.
Arnost Kleinzeller Jonathan Goldstein 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1984,154(6):561-571
Summary Osmotic responses of slices of dogfish rectal gland to hypotonic (urea-free) and hypertonic media were studied. Transfer of tissue from isotonic (890 mosM) to hypotonic (550 mosM) saline produced an osmotic swelling associated with a slow net uptake of cell K+ (and Cl–) and a slow, two-component efflux of urea. Media made hypertonic (1180 mosM) by addition of urea or mannitol produced osmotic shrinkage with a net loss of KCl. The cell osmotic responses in hypotonic media were lower than predicted for an ideal osmometer. No volume regulatory responses were seen subsequent to the initial osmotic effects. The cation influx in hypotonic media lacked specificity: in the presence of 0.5 mM ouabain or in K+-free media a net influx of Na+ was found. At steady state, the cell membrane potential evaluated from the Nernst potentials of K+ and triphenylmethyl phosphonium+, was independent of medium tonicity, suggesting the membrane potential as a determinant in the cellular osmotic response. Zero-time86Rb+ fluxes were measured:86Rb+ influx was not affected by hypotonicity, implying an unchanged operation of the Na+–K+-ATPase. On the other hand,86Rb+ efflux was significantly reduced at hypotonicity; this effect was transient, the efflux returning to the control value once the new steady state of cell volume had been reached. A controlled efflux system is therefore involved in the cell osmotic response. The absence of the volume regulatory phenomenon suggests that the cells are not equipped with a volume-sensing mechanism.Abbreviations and symbols
DW
dry weight
-
E
extracellular (polyethylene glycol) space
-
E
Nernst potential
- H2Oe
H2Oi tissue water, extra- and intracellular
-
TPMP
+
triphenyl methyl phosphonium salt
-
WW
wet weight 相似文献
4.
Slama I Ghnaya T Messedi D Hessini K Labidi N Savoure A Abdelly C 《Journal of plant research》2007,120(2):291-299
Sesuvium portulacastrum is a halophytic species well adapted to salinity and drought. In order to evaluate the physiological impact of salt on water
deficit-induced stress response, we cultivated seedlings for 12 days, in the presence or absence of 100 mmol l−1 NaCl, on a nutrient solution containing either 0 mmol l−1 or 25 mmol l−1 mannitol. Mannitol-induced water stress reduced growth, increased the root/shoot ratio, and led to a significant decrease
in water potential and leaf relative water content, whereas leaf Na+ and K+ concentrations remained unchanged. The addition of 100 mmol l−1 NaCl to 25 mmol l−1 mannitol-containing medium mitigated the deleterious impact of water stress on growth of S. portulacastrum, improved the relative water content, induced a significant decrease in leaf water potential and, concomitantly, resulted
in enhancement of overall plant photosynthetic activity (i.e. CO2 net assimilation rate, stomatal conductance). Presence of NaCl in the culture medium, together with mannitol, significantly
increased the level of Na+ and proline in the leaves, but it had no effect on leaf soluble sugar content. These findings suggest that the ability of
NaCl to improve plant performance under mannitol-induced water stress may be due to its effect on osmotic adjustment through
Na+ and proline accumulation, which is coupled with an improvement in photosynthetic activity. A striking recovery in relative
water content and growth of the seedlings was also recorded in the presence of NaCl on release of the water stress induced
by mannitol. 相似文献
5.
Laboratory studies have indicated that Na+, K+ (together with Cl? the presumed counter-ion to these cations), NO3? and mannitol represent the major cellular osmotica in Laminaria digitata (Huds.) Lamour. The cellular content of NO3? (together with a fraction of the K+ pool which acts as the counter-ion to NO3?) was found to be inversely proportional to that of mannitol, suggesting that L. digitata maintains a constant turgor by means of an isotonic substitution between these compounds. An analysis of the seasonal changes in solute content in an Arbroath (Scotland) population of L. digitata confirmed this hypothesis and indicated that the total pool of stored photosynthate was partitioned between the interconvertible carbohydrates mannitol and laminaran (which has a much lower osmotic potential than mannitol) depending on the size of the cellular pool of NO3?. 相似文献
6.
Bartolomeo Dichio Giovanna Margiotta Cristos Xiloyannis Sabino A. Bufo Adriano Sofo Tommaso R. I. Cataldi 《Trees - Structure and Function》2009,23(2):247-256
Two-year-old olive trees (Olea europaea L., cv. Coratina) were subjected to a 15-day period of water deficit, followed by 12 days of rewatering. Water deficit caused
decreases in predawn leaf water potential (Ψw), relative water content and osmotic potential at full turgor (Ψ
π100) of leaves and roots, which were normally restored upon the subsequent rewatering. Extracts of leaves and roots of well-watered
olive plants revealed that the most predominant sugars are mannitol and glucose, which account for more than 80% of non-structural
carbohydrates and polyols. A marked increase in mannitol content occurred in tissues of water-stressed plants. During water
deficit, the levels of glucose, sucrose and stachyose decreased in thin roots (with a diameter <1 mm), whereas medium roots
(diameter of 1–5 mm) exhibited no differences. Inorganic cations largely contribute to Ψ
π100 and remained stable during the period of water deficit, except for the level of Ca2+, which increased of 25% in water-stressed plants. The amount of malate increased in both leaves and roots during the dry
period, whereas citrate and oxalate decreased. Thin roots seem to be more sensitive to water deficit and its consequent effects,
while medium roots present more reactivity and a higher osmotic adjustment. The results support the hypothesis that the observed
decreases in Ψw and active osmotic adjustment in leaves and roots of water-stressed olive plants may be physiological responses to tolerate
water deficit. 相似文献
7.
Cation sensitivity and kinetics of guard-cell potassium channels differ among species 总被引:8,自引:0,他引:8
in ward rectifying
g uard
c ell
K
+
c hannel, GCKC1in, from three major crop plants Solanum tuberosum L., Nicotiana tabacum L., and Vicia faba L. Selecting guard cells for our analyses we aimed to test whether K+ channels of the same cell type differ among species. The channels shared basic features including voltage-dependence, selectivity
and single-channel conductance. They activated at hyperpolarization (V
1/2 ≈ −164 mV) with single channels of 7 pS underlying the whole-cell current. The channel density in S. tuberosum was higher than in V. faba and N. tabacum while the activation and deactivation kinetics were faster in the latter two species. Among different monovalent cations
the K+ channels discriminated strongly against Na+, Li+, and Cs+. The sensitivity to Cs+ was similar for the three species. Extracellular Ca2+ blocked the V.␣faba K+ channel at concentrations ≥1 mM but only affected its functional homologs in S. tuberosum and N.␣tabacum at higher concentrations and more-negative membrane potentials. Like the differences in Ca2+-sensitivity, protoplasts from the three species differed remarkably in their response towards extracellular pH changes. Whereas
protons neither altered the open probability nor the kinetic parameters of the V. faba GCKC1in, in S. tuberosum and N. tabacum this cation affected the voltage-dependent properties strongly. An increase in proton concentration from pH 8.5 to 4.5 shifted
the potential of half-maximal open probability to less-negative values with a maximum effect around pH 6.2. The pH modulation
of the K+ channels could be described assuming a two-state model where the open and closed channel can be protonated. The observed
differences in cation-sensitivity and voltage-dependent kinetics between K+ channels reflect the diversification of guard-cell channels that may contribute to species-specific variations in the control
of stomatal aperture.
Received: 19 July 1997 / Accepted: 2 October 1997 相似文献
8.
Phosphate cycles in energy crop systems with emphasis on the availability of different phosphate fractions in the soil 总被引:5,自引:0,他引:5
Cornelia Andersohn 《Plant and Soil》1996,187(1):11-21
The growing cells of hydroponic maize roots expand at constant turgor pressure (0.48 MPa) both when grown in low-(0.5 mol m-3 CaCl2) or full-nutrient (Hoagland's) solution and also when seedlings are stressed osmotically (0.96 MPa mannitol). Cell osmotic pressure decreases by 0.1–0.2 MPa during expansion. Despite this, total solute influx largely matches the continuously-varying volume expansion-rate of each cell. K+ in the non-osmotically stressed roots is a significant exception-its concentration dropping by 50% regardless of the presence or absence of K+ in the nutrient medium. This corresponds to the drop in osmotic pressure. Nitrate appears to replace Cl- in the Hoagland-grown cells.Analogous insensitivity of solute gradients to external solutes is observed in the radial distribution of water and solutes in the cortex 12 mm from the tip. Uniform turgor and osmotic pressures are accompanied by opposite gradients of K+ and Cl-, outwards, and hexoses and amino acids, inwards, for plants grown in either 0.5 mol m-3 CaCl2 or Hoagland's solution (with negligible Cl-). K+ and Cl- levels within both gradients were slightly higher when the ions were available in the medium. The gradients themselves are independent of the direction of solute supply. In CaCl2 solution all other nutrients must come from the stele, in Hoagland's solution inorganic solutes are available in the medium.24 h after osmotic stress, turgor pressure is recovered at all points in each gradient by osmotic adjustment using organic solutes. Remarkably, K+ and Cl- levels hardly change, despite their ready availability. Hexoses are responsible for some 50% of the adjustment with mannitol for a further 30%. Some 20% of the final osmotic pressure remains to be accounted for. Proline and sucrose are not significantly involved. Under all conditions a standing water potential step of 0.2 MPa between the rhizodermis and its hydroponic medium was found. We suggest that this is due to solute leakage.Abbreviations EDX
energy dispersive X-ray microanalysis
-
water potential
- 11-1
cell osmotic pressure
- P
turgor pressure 相似文献
9.
Reaumuria vermiculata (L.), a perennial dwarf shrub in the family of Tamaricaceae, is a salt-secreting xero-halophyte found widely in arid areas
of Tunisia. In the present study, physiological attributes of R. vermiculata were investigated under salt stress. Four-month-old plants were subjected to various salinity levels (0, 100, 200, 300, 400
or 600 mM NaCl) for 30 days under greenhouse conditions. Results showed that plants grew optimally when treated with standard
nutrient solution without NaCl supply. However, increasing osmolality of nutrient solutions caused a significant reduction
in biomass production and relative growth rate. This reduction was more pronounced in roots than in shoots. In addition, this
species was able to maintain its shoot water content at 30% of the control even when subjected to the highest salt level,
whereas root water content seemed to be unaffected by salt. Shoot water potential declined significantly as osmotic potential
of watering solutions was lowered and the more negative values were reached at 600 mM NaCl (−3.4 MPa). Concentrations of Na+ and Cl− in the shoots of R. vermiculata were markedly increased with increasing osmolality of nutrient solutions, whereas concentration of K+ was not affected by NaCl supply. Salt excretion is an efficient mechanism of Na+ exclusion from the shoots of this species exhibiting high K+/Na+ selectivity ratio over a wide range of NaCl salinity. Proline accumulation in shoots was significantly increased with increase
in salt level and may play a role in osmoregulation. 相似文献
10.
Summary The N-metabolism ofArthrocnemum fruticosum (L.) Moq., growing in a saline area north-east of the Dead Sea in Jordan, was studied over its vegetative growth period from
March to September 1981. Plant and soil samples were taken at monthly intervals. Water content, Na+, K+, Cl−, NH
4
+
, NO
2
−
and NO
3
−
concentrations were determined in the soil extracts, and the same determinations plus ash weight, soluble carbohydrates,
proline, proteins andin vivo nitrate reductase in the plant roots and shoots.
Soil humidity decreased and salinity increased from March to August, with re-wetting occurring in late July. K+ and Cl− were much lower in the soils than Na+. Plant relative dry weight increased during summer due to the absorption of Na+ in addition to increased organic dry weight. The uptake of Na+ was not balanced by a similar uptake of Cl−.
Ammonium and nitrate decreased in soil and plants in parallel with increasing salinity. Nitrite was only found in the roots
and always in very low quantities. Proline was found only in March. The total soluble carbohydrates in the roots showed a
short increase in June when the sodium in the plants also increased. It was concluded that carbohydrates may be used to balance
osmotic shocks, but that another compatible compounds is necessary to maintatin long-term osmotic equilibrium.
The nitrate reductase activity, measuredin vivo, and the soluble protein changed roughly in parallel with the internal nitrate from May to August, suggesting that nitrogen
uptake and reduction in the plant is inhibited during summer when the soil is dry and very saline. This could be a direct
effect of drought and/or salinity on the plants, or an indirect onevia an inhibition of nitrifying bacteria. 相似文献
11.
Following small hypo-osmotic shocks, ion concentrations (Na+, K+, Cl-) in Platymonas subcordiformis decreased; this was due mainly to an increase of cell volume. With larger hypo-osmotic stresses, the decrease of ion concentration continued and, additionally, extrusion of mannitol was observed. The ion and mannitol concentrations were not regained after 240 min. In contrast, following hyperosmotic shocks, the ion concentrations increased transitorily during the first 20–40 min. The same was true for K+ following small hyperosmotic stresses and for Na+ and — partially — Cl- with larger shocks. Large hyperosmotic stresses caused permanent accumulation of mannitol, which levelled off after 60–80 min. Thus the transient increase of ions bridged the concentration gap until mannitol was accumulated to a high enough concentration to account for the osmotic adaptation of Platymonas, together with a basal level of the ions K+, Na+, Cl-.Abbreviations PS
photosynthesis
- Resp
respiration 相似文献
12.
Total RNA was isolated from the diatom Cyclotella cryptica and separated into poly(A)+ and poly(A)− fractions. These fractions were subjected to in vitro translation/immunoprecipitation experiments using an antiserum directed
against the predominant light-harvesting complex of Cy. cryptica (ccry antiserum) and a heterologous antiserum raised against the light-harvesting complex of the cryptophyte Cryptomonas maculata (cmac antiserum). From translation reactions programmed with poly(A)+ RNA the ccry-antiserum immunoprecipitated polypeptides with relative molecular weights (Mr) of 27 000, 25 000, 23 000 and 21 000, while
the cmac-antiserum precipitated proteins with Mrs of 32 500 and 27 000, respectively. Subsequent cDNA synthesis and immunological
screening of the cDNA library with both antisera resulted in the isolation of six cDNA clones encoding light-harvesting subunits.
Full-length precursors were 199-210 amino acids in length and had Mrs of 20 000–23 000. The lengths of the putative signal peptides were 29 or 30 amino acids.
Pairwise comparison revealed that the similarity between the clones ranged from 54–99% on the nucleotide level and from 36–99%
at the amino acid level. In agreement with the data from the screens with the two antisera, the genes clustered into two groups.
The data provide evidence that the genes constitute a heterogeneous multigene family and that the light-harvesting system
of Cy. cryptica might be as complex as that of higher plants and green algae.
Received: 23 March 1998 / Accepted: 25 July 1998 相似文献
13.
Mustapha Gorai Mustapha Ennajeh Habib Khemira Mohamed Neffati 《Acta Physiologiae Plantarum》2011,33(3):963-971
The aim of this study was to investigate the effects of NaCl-salinity on the physiological attributes in common reed, Phragmites australis (Cav.) Trin. ex Steudel. Plants grew optimally under salinity treatment with standard nutrient solution without added salt
and at NaCl concentrations up to 100 mM. Applied for 21 days, NaCl-salinity (300 and 500 mM) caused a significant reduction
in growth allocation of all different tissues of P. australis. Shoot growth of reed plants displayed a highly significant correlation with plant–water relations and photosynthetic parameters.
The net photosynthetic rate and stomatal conductance of reed plants treated with NaCl-salinity at varying osmotic potential
(ψπ) of nutrient solutions were positively correlated, and the former variable also had a strong positive relationship with transpiration
rate. Leaf water potential and ψπ followed similar trends and declined significantly as ψπ of watering solutions was lowered. The increase in total inorganic nutrients resulting from increased Na+ and Cl− in all tissues and K+, Ca2+ and Mg2+ concentrations were maintained even at the most extreme salt concentration. Common reed exhibited high K+/Na+ and Ca2+/Na+ selectivity ratios over a wide range of salinities under NaCl-salinity. These findings suggest that reed plants were able
to adapt well to high salinities by lowering their leaf ψπ and the adjustment of osmotically active solutes in the leaves. 相似文献
14.
Tomader Errabii Christophe Bernard Gandonou Hayat Essalmani Jamal Abrini Mohamed Idaomar Nadia Skali Senhaji 《Acta Physiologiae Plantarum》2007,29(2):95-102
The effects of NaCl and mannitol iso-osmotic stresses on calli issued from sugarcane cultivars (cvs.) R570, CP59-73 and NCo310
were investigated in relation to callus growth, water content, ion and proline concentrations. Callus growth and water content
decreased under both stresses with the highest reduction under mannitol-induced osmotic stress. The ion concentration was
drastically affected after exposure to NaCl and mannitol. Salt stress induced an increase in Na+ and Cl− accumulation and a decrease in K+ and Ca2+ concentrations. Under mannitol-induced osmotic stress, K+ and Ca2+ concentrations decreased significantly while Na+ and Cl− concentrations remained unchanged. Free proline accumulation occurred under both stresses and was more marked in stress-sensitive
cv. than in stress-resistant one. Our results indicated that the physiological mechanisms operating at the plant cell level
in response to salt- and osmotic-induced stress in sugarcane cvs. are different. Among the cvs., we concluded that the stress
resistance is closely related to the maintain of an adequate water status and a high level of K+ and Ca2+ under both stresses and a low level of Na+ concentration in the presence of NaCl. Thus, sugarcane (Saccharum sp.) can be regarded as a Na+ excluder. We also provided evidence that proline accumulation is a stress-sensitive trait rather than a stress resistance
marker. 相似文献
15.
Kukita F 《The Journal of membrane biology》2011,242(3):119-135
In hypertonic solutions made by adding nonelectrolytes, K+ channels of squid giant axons opened at usual asymmetrical K+ concentrations in two different time courses; an initial instantaneous activation (I
IN) and a sigmoidal activation typical of a delayed rectifier K+ channel (I
D). The current–voltage relation curve for I
IN was fitted well with Goldman equation described with a periaxonal K+ concentration at the membrane potential above −10 mV. Using the activation–voltage curve obtained from tail currents, K+ channels for I
IN are confirmed to activate at the membrane potential that is lower by 50 mV than those for I
D. Both I
IN and I
D closed similarly at the holding potential below −100 mV. The logarithm of I
IN/I
D was linearly related with the osmolarity for various nonelectrolytes. Solute inaccessible volumes obtained from the slope
increased with the nonelectrolyte size from 15 to 85 water molecules. K+ channels representing I
D were blocked by open channel blocker tetra-butyl ammonium (TBA) more efficiently than in the absence of I
IN, which was explained by the mechanism that K+ channels for I
D were first converted to those for I
IN by the osmotic pressure and then blocked. So K+ channels for I
IN were suggested to be derived from the delayed rectifier K+ channels. Therefore, the osmotic pressure is suggested to exert delayed-rectifier K+ channels to open in shrinking rather hydrophilic flexible parts outside the pore than the pore itself, which is compatible
with the recent structure of open K+ channel pore. 相似文献
16.
Summary Induction of resting cells ofPseudomonas natriegens, nov. spec. to the oxidation of L-arabinose and mannitol, and an additional marine isolate (L5) to oxidation of lactose and
mannitol, was found dependent on the presence of Na+ with marine levels of Mg++ and K+ included in the suspending media. However, omission of Na+ and Mg++, and increase of the concentration of K+ in the suspending media, permitted rapid utilization of these substrates (but not of glucuronate) by resting cells and greatly
accelerated the rates of induced enzyme formation. Inclusion of Mg++ in the suspending media suppressed the rates of induction and oxidation stimulated by elevation of the K+ concentration. Incubation of resting cells of isolate L5 in an assay medium containing 0.26 M KCl preserved the ability of
the organisms to produce a significant level of the enzymes for oxidation of mannitol, even after 8 hrs aging of the cells
in the cold.
Chloramphenicol inhibited the synthesis of induced oxidative enzymes in both these marine isolates suspended in high K+ medium, and the extent of inhibition was proportional to the time of addition of the antibiotic. Interruption of induction
of isolate L5 cells to mannitol by washing within 30 min removed the stimulatory effect of the elevated level of K+, whereas longer periods of incubation before interruption yielded cells more fully induced. A greater amount of β-galactosidase
was produced by resting cells of the marine isolate L5 incubated with the inducer in media with elevated K+ concentrations than by those cultured on lactose or induced in the resting state in the presence of Na+. Moreover, inclusion of an elevated K+ concentration in the suspending media stimulated the production of L-arabinose isomerase in resting cells ofP. natriegens. The requirement for Na+ for the growth of these bacteria, however, was not replaceable by elevation of the K+ concentration of culture media.
Supported by grant no.G-15838 from the National Science Foundation and equipment loan contract NR-103-398 with the Office
of Naval Research. Contribution no. 35 from the University of Georgia Marine Institute at Sapelo Island. 相似文献
17.
Potassium (K+) and chloride (Cl−) are two essential elements for plant growth and development. While it is known that plants possess specific membrane transporters
for transporting K+ and Cl−, it remains unclear if they actively use K+-coupled Cl− cotransporters (KCC), as used in animals, to transport K+ and Cl−. We have cloned an Oryza sativa cDNA encoding for a member of the cation–Cl− cotransporter (CCC) family. Phylogenetic analysis revealed that plant CCC proteins are highly conserved and that they have
greater sequence similarity to the sub-family of animal K+–Cl− cotransporters than to other cation–Cl− cotransporters. Real-time PCR revealed that the O. sativa cDNA, which was named OsCCC1, can be induced by KCl in the shoot and root and that the expression level was higher in the leaf and root tips than in any
other part of the rice plant. The OsCCC1 protein was located not only in onion plasma membrane but also in O. sativa plasma membrane. The OsCCC1 gene-silenced plants grow more slowly than wild-type (WT) plants, especially under the KCl treatment regime. After 1 month
of KCl treatment, the leaf tips of the gene-silenced lines were necrosed. In addition, seed germination, root length, and
fresh and dry weight were distinctly lower in the gene-silenced lines than in WT plants, especially after KCl treatment. Analysis
of Na+, K+, and Cl− contents of the gene-silenced lines and WT plants grown under the NaCl and KCl treatment regimes revealed that the former
accumulated relatively less K+ and Cl− than the latter but that they did not differ in terms of Na+ contents, suggesting OsCCC1 may be involved in K+ and Cl− transport. Results from different tests indicated that the OsCCC1 plays a significant role in K+ and Cl− homeostasis and rice plant development. 相似文献
18.
Ionic and osmotic components of salt stress specifically modulate net ion fluxes from bean leaf mesophyll 总被引:13,自引:2,他引:11
S. Shabala 《Plant, cell & environment》2000,23(8):825-837
Ionic mechanisms of salt stress perception were investigated by non‐invasive measurements of net H+, K+, Ca2+, 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 ) Ca2+ 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 Ca2+ 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
19.
Kedzierska K Bober J Ciechanowski K Gołembiewska E Kwiatkowska E Noceń I Dołegowska B Dutkiewicz G Chlubek D 《Biological trace element research》2005,107(1):21-32
The aim of the study was to verify the hypothesis if copper could influence the activity of sodium-transporting systems in
erythrocyte membrane that could be related to essential hypertension. The examined group of patients consisted of 15 men with
hypertension. The control group was 11 healthy male volunteers. The Na+/H+ exchanger (NHE) activity in erythrocytes was determined according to Orlov et al. The activity of transporting systems (ATP-Na+/K+; co-Na+/K+/Cl−; ex-Na+/Li+; free Na+ and K+ outflow [Na+, K+-outflow]) was determined according to Garay's method. The concentration of copper in plasma was assessed using atomic absorption
spectrometry. The activity of ATP-Na+/K+ (μmol/L red blood cells [RBCs]/h) in hypertensive patients was 2231.5±657.6 vs 1750.5±291 in the control (p<0.05), the activity of co-Na+/K+/Cl− (μmol/L RBCs/h) in hypertensives was 171.3±77.9 vs 150.7±53.9 in the control (NS). Na+-outflow (μmol/L RBCs/h) in hypertensives was 118.3±51.6 vs 113.3±24.4 in the control (NS). The K+-outflow (μmol/L RBCs/h) in hypertensives was 1361.7±545.4 vs 1035.6±188.3 in the control (NS). The activity of ex-Na+/Li+ (μmol/L RBCs/h) in hypertensive patients was 266.1±76.1 vs 204.1±71.6 in the control (p<0.05). NHE activity (mmol/L RBCs/h) in hypertensives was 9.7±2.96 vs 7.7±1.33 in the control (p<0.05). In hypertensive patients, negative correlation was found between the activity of Na+/K+/Cl− co-transport and plasma copper concentration (R
s=−0.579, p <0.05) and between the activity of ex-Na+/Li+ and plasma copper concentration (R
s=−0.508, p<0.05). Plasma copper concentration significantly influences the activity of sodium transporting systems in erythrocyte membrane.
Copper supplementation could be expected to provide therapeutic benefits for hypertensive patients. 相似文献
20.
Galactosemic cataracts are characterized by electrolyte disturbances resulting in osmotic imbalance and loss of transparency.
We have studied the defensive role of quercetin, a bioflavonoid, against the alterations of calcium (Ca2+), sodium (Na+), and potassium (K+) concentrations in galactose-induced cataract in a rodent model. The experimental study was conducted on weanling male Wistar
rats with an average body weight of 34 ± 0.9 g. Different groups received normal stock AIN 93 diet (group A, n = 8), AIN 93 diet with 30% galactose (group B, n = 8), and AIN 93 diet with 30% galactose + quercetin at 400 mg/100 g diet (group C, n = 8). Aldose reductase activity and protein content and concentrations of Ca2+, Na+, and K+ were determined in normal and cataractous lenses. Treatment with quercetin resulted in a significant decrease in Na+ and Ca2+ and aldose reductase levels and an increase in K+ and protein levels in galactosemic cataractous lenses. These results imply that inclusion of quercetin contributes to lens
transparency through the maintenance of characteristic osmotic ion equilibrium and protein levels of the lens. 相似文献