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1.
Dextran glucosidase from Streptococcus mutans (SmDG), which belongs to glycoside hydrolase family 13 (GH13), hydrolyzes the non-reducing terminal glucosidic linkage of isomaltooligosaccharides and dextran. Thermal deactivation of SmDG did not follow the single exponential decay but rather the two-step irreversible deactivation model, which involves an active intermediate having 39% specific activity. The presence of a low concentration of CaCl2 increased the thermostability of SmDG, mainly due to a marked reduction in the rate constant of deactivation of the intermediate. The addition of MgCl2 also enhanced thermostability, while KCl and NaCl were not effective. Therefore, divalent cations, particularly Ca2+, were considered to stabilize SmDG. On the other hand, CaCl2 had no significant effect on catalytic reaction. The enhanced stability by Ca2+ was probably related to calcium binding in the β→α loop 1 of the (β/α)(8) barrel of SmDG. Because similar structures and sequences are widespread in GH13, these GH13 enzymes might have been stabilized by calcium ions.  相似文献   

2.
Structural calcium sites control protein thermostability and activity by stabilizing native folds and changing local conformations. Alicyclobacillus acidocaldarius survives in thermal-acidic conditions and produces an endoglucanase Cel9A (AaCel9A) which contains a calcium-binding site (Ser465 to Val470) near the catalytic cleft. By superimposing the Ca2+-free and Ca2+-bounded conformations of the calcium site, we found that Ca2+ induces hydrophobic interactions between the calcium site and its nearby region by driving a conformational change. The hydrophobic interactions at the high-B-factor region could be enhanced further by replacing the surrounding polar residues with hydrophobic residues to affect enzyme thermostability and activity. Therefore, the calcium-binding residue Asp468 (whose side chain directly ligates Ca2+), Asp469, and Asp471 of AaCel9A were separately replaced by alanine and valine. Mutants D468A and D468V showed increased activity compared with those of the wild type with 0 mM or 10 mM Ca2+ added, whereas the Asp469 or Asp471 substitution resulted in decreased activity. The D468A crystal structure revealed that mutation D468A triggered a conformational change similar to that induced by Ca2+ in the wild type and developed a hydrophobic interaction network between the calcium site and the neighboring hydrophobic region (Ala113 to Ala117). Mutations D468V and D468A increased 4.5°C and 5.9°C, respectively, in melting temperature, and enzyme half-life at 75°C increased approximately 13 times. Structural comparisons between AaCel9A and other endoglucanases of the GH9 family suggested that the stability of the regions corresponding to the AaCel9A calcium site plays an important role in GH9 endoglucanase catalysis at high temperature.  相似文献   

3.
Cytosolic Ca2+ and jasmonate mediate signals that induce defense responses in plants. In this study, the interaction between Ca2+ and methyl jasmonate (MJ) in modulating defense responses was investigated by monitoring ajmalicine production in Catharanthus roseus suspension cultures. C. roseus suspensions were treated with nine combinations of CaCl2 (3, 23, and 43 mM) and MJ (0, 10, and 100 μM) on day 6 of growth. Increased Ca2+ influx through the addition of extracellular CaCl2 suppressed ajmalicine production in MJ-induced cultures. The highest ajmalicine production (4.75 mg/l) was observed when cells were treated with a low level of calcium (3 mM) combined with a high level of MJ (100 μM). In the presence of 3 mM CaCl2 in the medium, the addition of Ca2+ chelator EGTA (1, 2.5, and 5 mM) or Ca2+ channel blocker verapamil (1, 10, and 50 μM) to MJ-induced (100 μM) cultures on day 6 also inhibited ajmalicine production at higher levels of the Ca2+ inhibitors. Hence, ajmalicine production in MJ-induced C. roseus cultures depended on the intracellular Ca2+ concentration and a low extracellular Ca2+ concentration (3 mM) enhanced MJ-induced ajmalicine production.  相似文献   

4.
Altered cytosolic free calcium concentrations ([Ca2+]i) accompany impaired brain metabolism and may mediate subsequent effects on brain function and cell death. The current experiments examined whether hypoxia-induced elevations in [Ca2+]i are from external or internal sources. In the absence of external calcium, neither KCl depolarization, histotoxic hypoxia (KCN), nor the combination changed [Ca2+]i. However, with external CaCl2 concentrations as small as 13 M, KCl depolarization increased [Ca2+]i instantaneously while hypoxia gradually raised [Ca2+]i. The combination of KCN and KCl was additive. Increasing external calcium concentrations up to 2.6 mM exaggerated the effects of K+ and KCN on [Ca2+]i, but raising medium calcium to 5.2 mM did not further augment the rise. Diminishing the sodium in the media, which alters the activity and perhaps the direction of the Na/Ca exchanger, reduced the increase in [Ca2+]i due to hypoxia, but enhanced the KCl response. The changes in ATP following K+ depolarization, KCN or their combination in the presence of physiological calcium concentrations did not parallel alterations in [Ca2+]i, which suggests that diminished activity of the calcium dependent ATPase does not underlie the elevation in [Ca2+]i. Valinomycin, an ionophore which reduces the mitochondrial membrane potential, elevated [Ca2+]i and the effects were additive with K+ depolariration in a calcium dependent manner that paralleled the effects of hypoxia. Together these results suggest that hypoxia-induced elevations of synaptosomal [Ca2]i are due to an inability of the synaptosome to buffer entering calcium.  相似文献   

5.
Seedlings of Trigonella foenum-graecum were treated with four heavy metal salts (CdCl2, CoCl2, K2Cr2O7 and NiCl2) to study the effect of heavy metals on growth and diosgenin production. It was found that CdCl2 increased diosgenin production up to 40-fold and CoCl2 increased diosgenin production up to 41-fold at concentrations which did not affect growth significantly. But K2Cr2O7 and NiCl2 were toxic to growth and inhibited diosgenin production. Effect of exogenously applied methyl jasmonate (MeJa) and calcium (Ca2+) on diosgenin production in seedlings of T. foenum-graecum was also investigated. MeJa enhanced the production of diosgenin. Maximum increase (10.5-fold) was found at 100 μL L−l concentration of MeJa. To study the role of Ca2+ on diosgenin production, seedlings of T. foenum-graecum were treated with a promoter of Ca2+ influx (calcium ionophore A23187), calcium depleted medium, Ca2+ channel blocker (verapamil) and antagonist (LaCl3), a divalent cation chelator (EGTA) and modulator of calcium release (caffeine). All the treatments were compared with a control containing 220 mg L−l concentration of CaCl2. The results suggest that the increase in cytosolic Ca2+ has an inhibitory role on diosgenin production. However, a calcium chelator or Ca2+ channel inhibitors could be used to elicit diosgenin production in this plant.  相似文献   

6.
Effect of calcium ions on heat tolerance of Saccharomyces cerevisiae and on the induction of Hsp104 synthesis by this microorganism was studied. Short-term (30 min) treatment with CaCl2 at 30°C enhanced the heat tolerance to the lethal heat shock (50°C); the synthesis of Hsp104 was induced as well. The effect of Ca2+ on the heat tolerance and Hsp104 synthesis was shown to be ion-specific and was inhibited by LaCl3, which is known to block calcium ion channels on the cytoplasmic membrane. The effect of Ca2+ depended on the potential of the inner mitochondrial membrane. When the cells were treated with sodium azide, which reduced the electrochemical potential, the effect of calcium both on heat tolerance and Hsp104 synthesis was suppressed. Depending on the concentration of exogenous Ca2+ and the ambient conditions, calcium ions may either induce or inhibit the expression of the stress genes and cell viability.  相似文献   

7.
Ca2+ entry through L-type calcium channels (CaV1.2) is critical in shaping the cardiac action potential and initiating cardiac contraction. Modulation of CaV1.2 channel gating directly affects myocyte excitability and cardiac function. We have found that phospholemman (PLM), a member of the FXYD family and regulator of cardiac ion transport, coimmunoprecipitates with CaV1.2 channels from guinea pig myocytes, which suggests PLM is an endogenous modulator. Cotransfection of PLM in HEK293 cells slowed CaV1.2 current activation at voltages near the threshold for activation, slowed deactivation after long and strong depolarizing steps, enhanced the rate and magnitude of voltage-dependent inactivation (VDI), and slowed recovery from inactivation. However, Ca2+-dependent inactivation was not affected. Consistent with slower channel closing, PLM significantly increased Ca2+ influx via CaV1.2 channels during the repolarization phase of a human cardiac action potential waveform. Our results support PLM as an endogenous regulator of CaV1.2 channel gating. The enhanced VDI induced by PLM may help protect the heart under conditions such as ischemia or tachycardia where the channels are depolarized for prolonged periods of time and could induce Ca2+ overload. The time and voltage-dependent slowed deactivation could represent a gating shift that helps maintain Ca2+ influx during the cardiac action potential waveform plateau phase.  相似文献   

8.
Regulation of proline accumulation in plants under chilling stress remains unclear. In this paper, we treated Jatropha curcas seedlings under chilling stress with exogenous calcium chloride (CaCl2), the plasma membrane Ca2+-channel blocker lanthanum chloride (LaCl3), calmodulin antagonists, chlorpromazine (CPZ), and trifluoperazine (TFP) and investigated the effects of calcium and calmodulin (CaM) on proline accumulation and chilling tolerance. The results showed that CaCl2 treatment significantly enhanced chilling stress-induced proline accumulation. CaCl2 also induced an almost immediate and rapid increase of Δ1-pyrroline-5-carboxylate synthetase (P5CS) and glutamate dehydrogenase activities, the key enzymes in the glutamate pathway of proline biosynthesis, and up-regulated P5CS expression, but it decreased the activity of proline dehydrogenase (ProDH), a key enzyme of proline degradation, and inhibited ProDH expression. Treatment with LaCl3, CPZ, and TFP exhibited the opposite effects to those by CaCl2 treatment. Moreover, CaCl2, LaCl3, CPZ, and TFP had little effect on the activities of ornithine aminotransferase and arginase, the key enzymes in the ornithine pathway of proline biosynthesis. These results indicated that Ca2+-CaM might be involved in signal transduction events, leading to proline accumulation in J. curcas seedlings under chilling stress, and that Ca2+-induced proline accumulation is a combined result of the activation of the glutamate pathways of proline biosynthesis and the simultaneous inhibition of the proline degradation pathway. In addition, CaCl2 treatment increased tissue vitality, decreased the content of the lipid peroxidation product malondialdehyde (MDA), and alleviated electrolyte leakage in J. curcas seedlings under chilling stress, indicating that exogenous Ca2+ can enhance chilling tolerance, and proline might be a key factor in this increased chilling tolerance.  相似文献   

9.
Summary. Calcium ion (Ca2+) uptake was measured in rod outer segments (ROS) isolated from rat retina in the presence of varying concentrations of CaCl2 in the incubation buffer (1.0–2.5 mM). It is known that taurine increases Ca2+ uptake in rat ROS in the presence of ATP and at low concentrations of CaCl2 (Lombardini, 1985a); taurine produces no significant effects when CaCl2 concentrations are increased to 1.0 and 2.5 mM. With the removal of both taurine and ATP, Ca2+ uptake in rat ROS increased significantly in the presence of 2.5 mM CaCl2. Taurine treatment in the absence of ATP was effective in decreasing Ca2+ uptake at the higher levels of CaCl2 (2.0 and 2.5 mM). Similar effects were observed with ATP treatment. The data suggest that taurine and ATP, alone or in combination, limit the capacity of the rat ROS to take up Ca2+ to the extent that a stable uptake level is achieved under conditions of increasing extracellular Ca2+, indicating a protective role for both agents against calcium toxicity. Received January 25, 2000/Accepted January 31, 2000  相似文献   

10.
Characteristics of the increasing effect for the concentration of intracellular calcium ions ([Ca2+]i) by high-KCl application were investigated in the neuroblastoma×glioma hybrid NG108-15 cell line (NG108-15 cells). The present study confirmed that the increasing effect of [Ca2+]i by high-KCl application in single NG108-15 cells, differentiated with dibutyryl cAMP (Bt2cAMP), was significantly enhanced, compared to undifferentiated cells. The following observations were made at first: (1) The response to high-KCl application, in both undifferentiated and differentiated cells, was significantly inhibited by calciseptine (CaS), an L-type Ca2+ channel blocker, but not by N-, P- and R-type Ca2+ channel blockers. The IC50 values for CaS in both undifferentiated and differentiated cell was almost identical. (2) The inhibitory effect of CaS was irreversible. (3) The increasing effect for [Ca2+]i by high-KCl application was completely dependent on the presence of extracellular calcium ions. (4) The increased [Ca2+]i by high-KCl application under a plateau concentration was quickly decreased to basal levels when the high-KCl solution was exchanged for a high-KCl solution containing EGTA (without CaCl2). Together, these results suggest that the enhancement of the response effect of [Ca2+]i by high-KCl application in differentiated single NG108-15 cells was mainly due to the quantitative increase of L-type voltage-sensitive calcium channels (VSCCs), which were irreversibly inhibited by CaS.  相似文献   

11.
The response of pericarp disks from ripening tomato (Lycopersicon esculentum Mill. cv. Traveler‘76) to CaCl2, additions was studied to determine the effect of Ca2+ on ethylene and CO2 production. Application of 5 mM CaCl2 resulted in a 2, 20, 33, 39, and 50% increase in ethylene production in disks obtained from preclimacteric minimum, climacteric rise, climacteric peak, one, and two days postclimacteric fruit, respectively. CaCl2 concentrations of 10 and 50 mM gave no additional stimulation of ethylene production; CO2 production at 5 mM CaCl2 was not different from controls, but is increased at 10 and 50mM CaCl2. CaCl2 also increased ethylene production in disks treated with 1-aminocyclopropane-1-carboxylic acid (ACC) or aminoethoxy-vinylglycine. Chloride salts of K+, Na+, Mg2+, Sr2+ and La3+ did not stimulate ethylene production. SrCl2 stimulated ethylene production to a lesser degree than CaCl2. Disks from potato (Solanum tuberosum L. cv. Katahdin) tubers produced greater quantities of ethylene and ACC when 5 mM CaCl2 was included in the incubation medium (K. B. Evensen, 1983. Physiol. Plant. 60:125–128). Ca2+-treated disks had more than three times as much ACC synthase activity as control disks after 18 to 24 h incubation, when ethylene and ACC were maximal. The apparent Km for S-adenosylmethionine was 13 μM at 29°C, pH 8.0 in extracts from both Ca2+-treated and control disks. Inclusion of 1 to 50 mM CaCl2 in the assay medium did not significantly affect enzyme activity. ACC synthase extracted from control and Ca2+-treated disks had a pH optimum of 8.5 and an apparent molecular weight of 72 kdalton, estimated by gel filtration. It is likely that the presence of Ca2+ in the buffer allows greater synthesis of ACC synthase as part of the wound-healing response in potato, while in tomato the predominant effect is on membrane stabilization.  相似文献   

12.
Calcium Dependence of Rapid Auxin Action in Maize Roots   总被引:6,自引:2,他引:4       下载免费PDF全文
We investigated the interaction of Ca2+ and auxin on root elongation in seedlings of Zea mays L. The seedlings were raised either in the presence of Ca2+ (high calcium; HC = imbibed and raised in 10 millimolar CaCl2), in the absence of additional Ca2+ (intermediate calcium; IC = imbibed and raised in distilled H2O, calcium supply from seed only), or without additional Ca2+ and subsequently depleting them of Ca2+ (low calcium; LC = imbibed and raised in distilled H2O and subsequently treated with 1 millimolar ethyleneglycol-bis-[β-aminoethylether]-N,N,N′,N′ -tetraacetic acid [EGTA]). Exposure of roots of either HC or IC seedlings to auxin concentrations from 0.1 to 10 micromolar resulted in strong inhibition of elongation. In roots of LC seedlings, on the other hand, auxin concentrations as high as 10 micromolar caused only slight inhibition of elongation. Adding 0.5 millimolar Ca2+ to LC roots in the presence of IAA allowed normal expression of the inhibitory action of the hormone. Inhibition of elongation in IC roots by indoleacetic acid was reversible upon treatment of the roots with 1 millimolar EGTA. The inhibitory action of auxin could then be re-established by supplying 0.5 millimolar Ca2+. The data indicate that Ca2+ may be necessary to the growth-regulating action of auxin. The significance of this finding is discussed with respect to the potential role of Ca2+ as a second messenger of auxin action and the relevance of this model to recent evidence for gravi-induced redistribution of Ca2+ and its role in establishing gravitropic curvature.  相似文献   

13.
Summary The growth of WI-38 cells in serum-free growth medium with and without hormone supplementation in the presence of elevated Ca2+ concentrations was investigated. At 5 mM CaCl2, WI-38 cells seeded at low density without serum or hormone supplementation showed up to a 12-fold increased in cell number at saturation density over that obtained at day 1. Saturation densities were comparable when either 5 mM CaCl2 or epidermal growth factor (1 mM CaCl2) was used in the presence of insulin, dexamethasone and transferrin. Combining suboptimal doses of epidermal growth factor and CaCl2 resulted in an additive effect on saturation density. Thus, nornal human diploid cells are capable of substantial growth in serum-free, hormone-free growth medium. In contrast, confluent cultures refed with the same medium are not responsive to elevated Ca2+ concentrations. In fact, elevated Ca2+ concentrations inhibited the proliferative response of confluent cultures to epidermal growth factor, but enhanced their response to the combined treatment of insulin, transferrin and dexamethasone. This work was supported by the United States Public Health Society grants T-32, CA09171 and AG-00378. Editor's Statement This paper rigorously dissects the interplay among external Ca2+ concentration, cell density and specific growth factors on fibroblast growth in defined medium. Wallace L. McKeehan  相似文献   

14.
The dynamics of intracellular Ca2+ signal in response to NMDA (N-methyl-D-aspartate, 30 μM) or KA (kainite, 30 μM), its dependence on extracellular Ca2+ and the mechanisms of KA-triggered Ca2+ entry into neurons have been tested in neurons of rat cortical primary cultures. The level of intracellular free Ca2+ concentrations ([Ca2+] i ) was evaluated on Leica SP5 MF confocal microscope using Fluo-3 fluorescent dye, which resolves changes in [Ca2+] i in the micromolar range. The dynamics of [Ca2+] i increase in response to NMDA and KA was different but in both cases the [Ca2+] i increase required the presence of Ca2+ in the extracellular solution. The neuronal population was found to be heterogeneous, based on the response to KA applied together with either L-type calcium channel blocker nifedipine (3 μM) or IEM-1460 (3 μM), a blocker of Ca2+-permeable AMPAR (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor) lacking GluR2 subunit. Experiments exhibited three types of calcium responses, characteristically belonging to interneurons (expressing Ca2+-permeable AMPAR), pyramidal neurons (with AMPAR containing GluR2, making them impermeable to Ca2+), and intermediate type of cells expressing both AMPAR types. Thus, we have demonstrated the role of AMPAR and L-type calcium channels in KA-triggered Ca2+ entry into neurons. The dynamics of [Ca2+] i during the KA treatment was shown to depend on subunit composition of particular AMPAR subtype expressed in neurons. The data suggest that neuronal types existing in adult cortical tissue are probably presented in primary culture, too.  相似文献   

15.
Zinc is an essential trace element necessary to life. This metal may exert some of its physiological effects by acting directly on cellular membranes, either by altering permeability or by modulating the activity of membrane-bound enzymes. On the other hand, calcium is an essential element in a wide variety of cellular activities. The aim of the present work was to study a possible interaction between zinc and calcium on intestinal transport ofd-galactose in jejunum of rabbit in vitro. In media with Ca2+, when ZnCl2 was present at 0.5 or 1 mM, zinc was found to reduce thed-galactose absorption significantly. In Ca2+-free media, where CaCl2 was omitted and replaced isotonically with choline chloride, the sugar transport was not modified by zinc. Verapamil at 10−6 M (blocking mainly Ca2+ transport) did not modify the inhibitory effect of zinc ond-galactose transport. When 10−6 M of A 23187 (Ca2+-specific ionophore) was added with/without Ca2+ to the media, ZnCl2 produced no change in sugar transport. These results could suggest a possible interaction of calcium and zinc for the same chemical groups of membrane, which could affect the intestinal absorption of sugars.  相似文献   

16.
Ca2+ enhanced the transformation frequency of Thermoactinomyces vulgaris (stock no. 1278) of an auxotrophic strain by the chromosomal DNA isolated from a prototrophic strain (stock no. 1227). The number of transformants showed a marked increase with increasing concentration of CaCl2 upto 0.05 mM; and above this concentration, the transformation frequency decreased significantly. Antipsychotic drugs that are potent calmodulin inhibitors, like trifluoperazine and chlorpromazine, when applied in the concentration range of 0.01–0.04 mM along with optimal CaCl2 concentration to the cultures of the recipient cells, resulted in a significant inhibition in the frequency of Ca2+-stimulated transformation. The results of present investigation suggest the involvement of a Ca2+-dependent protein activator in the development of Ca2+-mediated competence, which could have played an important role in the enhancement of genetic transformation in this aerobic spore forming thermophilic actinomycete. Received: 21 May 2002 / Accepted: 21 June 2002  相似文献   

17.
The cytotoxic effect of the antitumor antibiotic peplomycin (PEP), a new member of bleomycin group antibiotics, toward HeLa cells and mouse FM3A cells is enhanced by some membrane-interacting drugs such as verapamil, persantin, prenylamine, chlorpromazine and anafranil. The enhancing action of verapamil is selective to this group antibiotics, since it does not potentiate the cytotoxic effects of vincristine, adriamycin, mitomycin C, cis-diamminedichloroplatinum(II) and macromomycin. An enhanced PEP cytotoxicity has been also demonstrated by the treatment of cells in the presence of increased CaCl2. This enhancing effect of increased CaCl2 is prevented by the Ca2+ transport inhibitor ruthenium red. Since these membrane-directed drugs have been shown to affect Ca2+ metabolism, we conclude that potentiation of PEP cytotoxicity by these drugs is mediated by an increase in intracellular Ca2+.  相似文献   

18.
P2Y receptors have been implicated in the calcium mobilization by the response to neuroexcitatory substances in neurons and astrocytes, but little is known about P2Y receptors in microglia cells. In the present study, the effects of ADP on the intracellular calcium concentration ([Ca2+]i) in cultured dorsal spinal cord microglia were detected with confocal laser scanning microscopy using fluo-4/AM as a calcium fluorescence indicator that could monitor real-time alterations of [Ca2+]i. Here we show that ADP (0.01–100 μM) causes a rapid increase in [Ca2+]i with a dose-dependent manner in cultured microglia. The action of ADP on [Ca2+]i was significantly blocked by MRS2211 (a selective P2Y13 receptor antagonist), but was unaffected by MRS2179 (a selective P2Y1 receptor antagonist) or MRS2395 (a selective P2Y12 receptor antagonist), which suggest that P2Y13 receptor may be responsible for ADP-evoked Ca2+ mobilization in cultured microglia. P2Y13-evoked Ca2+ response can be obviously inhibited by BAPTA-AM and U-73122, respectively. Moreover, removal of extracellular Ca2+ (by EGTA) also can obvious suppress the Ca2+ mobilization. These results means both intracellular calcium and extracellular calcium are potentially important mechanisms in P2Y13 receptor-evoked Ca2+ mobilization. However, P2Y13 receptor-evoked Ca2+ response was not impaired after CdCl2 and verapamil administration, which suggest that voltage-operated Ca2+ channels may be not related with P2Y13-evoked Ca2+ response. In addition, Ca2+ mobilization induced by ADP was abolished by different store-operated Ca2+ channels (SOCs) blocker, 2-APB (50 μM) and SKF-96365 (1 mM), respectively. These observations suggest that the activation of P2Y13 receptor might be involved in the effect of ADP on [Ca2+]i in cultured dorsal spinal cord microglia. Furthermore, our results raise a possibility that P2Y13 receptor activation causes Ca2+ release from Ca2+ store, which leads to the opening of SOCs.  相似文献   

19.
Involvement of extracellular Ca2+ in stomatal movement through the regulation of water channels was investigated in broad bean (Vicia faba L.). Leaf peels were first incubated to open stomata, and then transferred to buffers in the presence of different CaCl2 concentrations. Stomatal status was observed under magnification and stomatal aperture (pore width/length) was measured. Stomatal closure was significantly induced and aperture oscillation occurred at lower extracellular concentrations of calcium ([Ca2+]ext), while at higher concentrations, no significant change in stomatal aperture was observed, which was similar to the response recorded with HgCl2. Lower [Ca2+]ext-induced stomatal closure could be reversed using depolarizing buffer. It is suggested that lower [Ca2+]ext regulates water channels through an indirect way and at higher concentrations, extracellular Ca2+ is involved in regulating stomatal aperture by directly influencing water channels to retard aperture change.  相似文献   

20.
J. Gorham  J. Bridges 《Plant and Soil》1995,176(2):219-227
The optimum Ca2+ concentration for growth of cotton (Gossypium hirsutum cv. Acala SJ-2) was in the range 1 to 15 mol m–3 for plants growing in hydroponic culture with 100–150 mol m–3 NaCl. Most saline (but not sodic) soils contain higher Ca2+ concentrations. CaCl2 was inhibitory to the growth of cotton above 20–50 mol m–3. Increasing concentrations of Ca2+ in the range 0–2 mol m–2 drastically reduced Na+ accumulation in the leaves. As CaCl2 concentrations were increased above the optimum for growth there was a further reduction in leaf Na+ accumulation, but this was more than offset by increased leaf Ca2+ and Cl concentrations. Leaf K+ concentrations were not much affected by changes in external CaCl2 concentrations. The response of Mg2+ varied from an increase to a decrease with increasing external CaCl2 and was influenced by nutritional status. There was no evidence that high Ca2+ caused a deficiency of Mg2+ in cotton. Except for Cl, whose concentrations tended to decrease initially and then increase as the CaCl2 concentration increased, the anions were largely unaffected by changes in external CaCl2.  相似文献   

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